Journal articles on the topic 'Mineralisation'
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1
Roberts, Fiona, Greg Markby, Scott Dillon, Colin Farquharson, and Vicky E. MacRae. "Beyond mineralisation: metabolic functions for matrix mineralisation regulators." Journal of Endocrinology 245, no. 2 (May 2020): R11—R22. http://dx.doi.org/10.1530/joe-19-0460.
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The physiological mineralisation of skeletal tissues, as well as the pathological mineralisation of soft tissues involves a fine balance between regulators that either promote or inhibit the process. In recent years, several studies have advocated a non-skeletal role for some of these mineralisation regulators in a range of human diseases, including diabetes, cardiovascular disease, obesity and neurodegenerative disease. This is an emerging area of interest and the functional roles and mechanisms of action of these various endocrine factors, phosphatases and phosphodiesterase’s in important pathologies are the focus of this review. Mechanistic insight of the pathways through which these acknowledged regulators of skeletal mineralisation act beyond the skeleton has the potential to identify druggable targets for commonly experienced morbidities, notably those related to metabolism and metabolic syndrome.
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Currey, J. D. "The design of mineralised hard tissues for their mechanical functions." Journal of Experimental Biology 202, no. 23 (December 1, 1999): 3285–94. http://dx.doi.org/10.1242/jeb.202.23.3285.
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Most hard tissues have as their primary purpose to be stiff. Outside the arthropods, mineralisation of a soft organic matrix is the almost universal method of producing high stiffness. However, stiffening brings with it the undesirable mechanical result of brittleness (lack of toughness). The mineralisation of some tissues, such as bone and dentine, can be modified rather easily, in evolutionary terms, to produce the optimum mix of stiffness with bending strength (which, except at the highest mineralisations, go together) on one hand and toughness on the other hand. However, in most other tissues, such as mollusc shell, echinoderm skeleton, brachiopod shell, barnacle shell and enamel, mineralisation is almost all-or-none, and no subtle gradations seem possible. In such cases, other features, such as architecture, must be modified to produce a useful skeleton. Not only the mechanical properties of the skeletal tissue, but its cost, mass and time taken for production will, biologists tend to assume, be balanced by natural selection to produce a satisfactory result. However, such complexity makes it difficult to be sure that we understand the extent to which mineralised skeletal materials are the best possible solution to the problems facing the animals and that we are not just telling ‘Just-So’ stories. Furthermore, there are some skeletal materials that do not seem to make much sense at the moment, although no doubt all will become clear eventually.
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Bianchini Jr., I., RH Silva, MB Cunha-Santino, and RS Panhota. "Aerobic and anaerobic decomposition of Pistia stratiotes leachates from a tropical eutrophic reservoir (Barra Bonita, SP, Brazil)." Brazilian Journal of Biology 70, no. 3 (August 2010): 559–68. http://dx.doi.org/10.1590/s1519-69842010000300012.
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The present study discussed the kinetic aspects of leachate decomposition from an aquatic macrophyte, Pistia stratiotes L (water lettuce). This species was collected from Barra Bonita Reservoir located in the State of São Paulo (Brazil). Decomposition chambers were prepared with high molecular weight (HMW), low molecular weight (LMW) and integral (INT = HMW + LMW) dissolved organic matter (DOM) diluted with reservoir water. The samples were incubated at 20 °C, in darkness and under aerobic or anaerobic conditions. For 79 days, the concentrations of dissolved oxygen (DO) and organic carbon (OC) were measured. For calculating the deoxygenation coefficients (k d) and maximum oxygen consumption (COmax) the concentration of DO was integrated and fitted to a first-order kinetics model, which also applied to the depletion of OC concentrations. The COmax of INT incubations were 4% higher than the sum of HMW and LMW fractions. The deoxygenation coefficients, k d, had the same order of magnitude for all treatments. In relation to carbon decay, regardless of the availability of oxygen, the INT DOM also showed higher mineralisation. These results suggest that the leachate mineralisations are short-term processes; when the fractionation of the leachates occurs, the LMW had organic compounds with more accessibility for heterotrophic metabolism. On the other hand, when compared to INT DOM, the HMW and LMW were less consumed suggesting an interaction of the reactivity of the leachate. Our data suggest that in the Barra Bonita Reservoir the mineralisation of P. stratiotes leachates occurs through two competitive pathways (i.e. mineralisation of the labile compounds and formation of recalcitrant organic resources and their mineralisation) in which the oxygen availability and the molecular mass of DOM can interfere in the rates of reactions.
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Padhi, Ajoy Kumar, Mrinal Kanti Mukherjee, Brajesh Kumar Tripathi, Dheeraj Pande, Balbir Singh Bisht, and Bhabesh Chandra Sarkar. "Polymetallic Uranium Mineralisation in Rohil, Rajasthan, Western India: Insights from Mode of Occurrences, Structural Controls, Alteration Geochemistry and Exploration." Minerals 13, no. 4 (April 14, 2023): 555. http://dx.doi.org/10.3390/min13040555.
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Geological and radiometric studies of outcrops aided by extensive subsurface exploration through drill holes in an otherwise soil-covered terrain revealed the existence of low grades, medium tonnage, and metasomatite types of polymetallic uranium deposits at Rohil in India. Microscopic studies, electronprobe micro analyses, and geochemical analyses of samples from lodes indicate the polymetallic nature of mineralisation involving copper and molybdenum, in addition to uranium. Wide variations in the composition of fluid (S-, F-, P-, and O-rich) led to the formation of sulphides, fluorite, U-phosphosilicate, quartz, and magnetite, respectively, and are associated with uraninite. Litho-geochemical analyses from the Rohil deposit indicate multifarious metasomatic alterations associated with polymetallic mineralisation occurring in veins. The major mineralogical and metasomatic controls on rock compositions and the extent of material transfer processes that influenced the host rocks and mineralisati on are quantified by molar element ratio studies and alteration plots. General element ratio (GER) diagrams on chemical analyses of rock samples reveal albitisation and chloritisation as major and microclinisation, sericitisation, carbonatisation, and silicification as minor wall rock alterations associated with ore mineralisation. The alteration box plot between the chlorite–carbonate–pyrite index (CCPI) and the Ishikawa alteration index (AI) indicates the influence of hydrothermal activity and dominance of both albitisation and chloritisation. The ore zone is controlled by meso- and microstructures and the geometry of the soda- and potash-metasomatised zone around hydrothermal veins. This zone contains several anastomosing mineralised veins defined by a prominent joint that is set in quartzite that strikes subparallel to the axial surface of the F2 isoclinal folds and the pervasive schistosity S1 in the quartz–feldspar–biotite schist. Aventurisation of albite and microcline, established through electron probe micro analyses, can be considered as a pathfinder for uranium mineralisation. The close association of uranium and metallic sulphide mineralisation with microstructural, mineralogical (albitisation, chloritisation, and microclinisation), and geochemical variations can be applied as suitable exploration guides in a similar geological set-up worldwide.
5
Sierra, J. "Nitrogen mineralisation and its error of estimation under field conditions related to the light-fraction soil organic matter." Soil Research 34, no. 5 (1996): 755. http://dx.doi.org/10.1071/sr9960755.
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In situ, incubations of intact soil cores were carried out to identify factors controlling nitrogen (N) mineralisation and its spatial variability under field conditions. The analysed factors were soil moisture, temperature, and the content of light-fraction (density ≤ 2 Mg/m3) organic carbon (LC) contained in the soil. The error associated with the estimate of in situ N mineralisation was analysed using undisturbed samples in laboratory incubations. The coefficient of variation of in situ N mineralisation ranged from 58 to 234%. Nitrogen and LC mineralisation in the field showed a similar temporal pattern. The major factor affecting this pattern was soil temperature, soil moisture being near the optimum level throughout the experiment. The rate of N mineralisation during an incubation period was correlated with the content of LC at the beginning of the period; this factor explained 40–50% of the variation in N mineralisation. At a low rate of N mineralisation, a large proportion of the spatial variability was attributed to the error of estimation. From the relationship between N mineralisation and LC content, we estimated the rate constant k which could be expressed as a function of soil temperature. Within the observed temperature range (daily mean average 11–17°C), the Q10 (temperature coefficient) of in situ N mineralisation was 1.5. Negative values of N mineralisation were associated with the lower LC content of each period, indicating the presence of an immobilisation process, or that a proportion of LC was not involved in N mineralisation.
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Stenger, R., G. F. Barkle, and C. P. Burgess. "Mineralisation of organic matter in intact versus sieved/refilled soil cores." Soil Research 40, no. 1 (2002): 149. http://dx.doi.org/10.1071/sr01003.
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In a 6-month laboratory incubation study, we compared the net C and N mineralisation of the soil organic matter (SOM) of 3 pasture soils and the mineralisation of glucose-C in intact versus sieved/refilled soil cores. The main questions were whether the net C and N mineralisation differed between intact and sieved/refilled soil cores after a conditioning period of 4 weeks, and how much the C and N mineralisation of SOM differed among the similarly managed pasture soils. Apart from the net nitrogen mineralisation in one soil, there were no significant differences in cumulated mineralisation of C or N from SOM between the core types. In a fine-textured soil, net mineralisation of glucose-C differed significantly between core types, which was attributed to the different distribution of the amended glucose in intact and sieved/refilled cores. Net C and N mineralisation of SOM were closely correlated in the sieved/refilled cores, whereas no significant correlation was found in the intact cores. Expressing net C and N mineralisation as percentages of total soil C and N showed a more than 2-fold maximum difference between the soils in spite of similar long-term organic matter input. Subsequent studies should be done using more replicates and wider diameter, better controllable cores on ceramic plates. CO2, net nitrogen mineralisation (NNM), soil microbial biomass.
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Brackin, Richard, Scott Buckley, Rhys Pirie, and Francois Visser. "Predicting nitrogen mineralisation in Australian irrigated cotton cropping systems." Soil Research 57, no. 3 (2019): 247. http://dx.doi.org/10.1071/sr18207.
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Cotton cropping systems in Australia have poor nitrogen (N) use efficiency, largely due to over-application of N fertiliser. The N mineralisation from soil organic N reserves is often overlooked, or underestimated despite recent studies indicating that it may contribute the majority of N exported with the crop. Predicting N mineralisation is a major challenge for agricultural industries worldwide, as direct measurements are time-consuming and expensive, but there is considerable debate as to the most reliable methods for indirect estimation. Additionally, laboratory incubations assess potential (rather than actual) mineralisation, and may not be representative of N cycling rates in the field. We collected 177 samples from most major Australian cotton growing regions, and assessed their mineralisation potential using ex situ laboratory incubations, along with an assessment of potential indicators routinely measured in soil nutrient tests. Additionally, at three unfertilised sites we conducted in situ assessment of mineralisation by quantifying soil N at the beginning of the growing season, and soil and crop N at the end of the season. We found that Australian cotton cropping soils had substantial mineralisation potential, and that soil total N and total carbon were correlated with mineralisation, and have potential to be used for prediction. Other potential indicators such as carbon dioxide production and ammonium and nitrate concentrations were not correlated with mineralisation. In parallel studies of ex situ and in situ mineralisation, we found ex situ laboratory incubations overestimated mineralisation by 1.7 times on average. We discuss findings in terms of management implications for Australian cotton farming systems.
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Parfitt, R. L., and G. J. Salt. "Carbon and nitrogen mineralisation in sand, silt, and clay fractions of soils under maize and pasture." Soil Research 39, no. 2 (2001): 361. http://dx.doi.org/10.1071/sr00028.
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Although several studies have quantified either C mineralisation or net N mineralisation in particle-size fractions, no work has examined simultaneous C and net N mineralisation. Therefore, we conducted an 18-week laboratory incubation to compare simultaneous mineralisation in sand, silt, and clay fractions. The soils (silt loams) were collected from fields of long-term pasture and maize. Sand, silt, and clay were separated by mild dispersion in water followed by centrifugation. Samples were incubated at 25°C in the dark in a quartz matrix, and were leached every 2 weeks with 0.004 M CaCl 2 at a suction of 20 kPa to remove soluble products. C mineralisation was determined from CO 2 -C evolved each 2 weeks, and mineral N was measured in the leachate. C mineralisation, on a C basis, followed the order sand > clay > silt, and was related (r 2 = 0.88) to the proportion of O-alkyl C (carbohydrate C) estimated from 13 C NMR. The low mineralisation in the silt may also have been a result of the physical protection of substrates in small pores in this fraction. The rates of N release were initially rapid from the maize soil fractions, and were consistent with the high initial mineral-N contents; subsequently, the rates were slower, and probably related to C mineralisation. For the pasture soil, N mineralisation followed the order clay>silt>sand, and was inversely related to the C: N ratios. Immobilisation appeared to take place in the sand fraction, whereas a large part of the net N mineralisation occurred in the clay fraction. There is now good evidence that rates of C and net N mineralisation differ within discrete particle size fractions, and data on such fractions could be useful for constructing soil organic matter models.
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Franzmann, P. D., L. R. Zappia, B. M. Patterson, J. L. Rayner, and G. B. Davis. "Mineralisation of low concentrations of organic compounds and microbial biomass in surface and vadose zone soils from the Swan Coastal Plain, Western Australia." Soil Research 36, no. 6 (1998): 921. http://dx.doi.org/10.1071/s97116.
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Mineralisation rates for ring-labelled 14C-atrazine, benzene, and toluene were determined for a number of Swan Coastal Plain soils which had not been previously in contact with these contaminants. Microbial biomass was estimated by phospholipid techniques in soil samples from the same sites. Mineralisation rates for the volatile aromatic hydrocarbons in the thin (up to 30 cm) surface soils (23·4-42·6 µmol/kg · day when fitted to zeroth-order rate kinetics) were appreciably faster than the mineralisation rates measured in soils collected from a depth of 1 m (0·11-3·0 µmol/kg · day). The pesticide atrazine was degraded slowly, with degradation rates in surface soils ranging from 1·22×10-3 to 2·78×10-4 µmol/kg · day, and those in soils at 1 m ranging from 5· 13×10-4 to 3·16×10-4 mol/kg · day. When mineralisation data were fitted to first-order kinetics then half-lives for atrazine mineralisation ranged from about 1 year in surface soils to 3·1-5·1 years in soils at 1 m. These rates were comparable to atrazine mineralisation rates measured in soils that had not been previously in contact with atrazine, as reported by others. The extent of mineralisation of the organic compounds v. time generally fitted better to zeroth-order kinetics than to first-order kinetics. Confidence in the determination of the mineralisation rate at slow rates of mineralisation was low (r2 as low as 0·2 in plots of the extent of mineralisation v. time in zeroth-order and first-order plots for samples that showed slow mineralisation). Biomass, expressed as stationary phase Escherichia coli equivalents (SPEE), ranged from 1·4 ×107 to 1·2×108 SPEE/g dry weight for surface soils, and from 8·6×105 to 7·3×106 SPEE/g dry weight for soils at 1 m. The phospholipids extracted from surface soils tended to contain higher proportions of unsaturated and hydroxy fatty acids than soils at 1 m, which contained higher relative concentrations of branched fatty acids, which is consistent with the microbiota moving, with greater depth, from a Gram-negative to a more Gram-positive dominated population. Biomass correlated well with mineralisation rates of the volatile aromatic compounds (r2 = 0·96) but less so with atrazine mineralisation rates (r2 = 0·86), although further experiments would be required to determine if biomass was consistently a good predictor of mineralisation rate for these organic contaminants. The results suggest that it is important to maintain a fertile, ‘microbially rich’ soil in order to maximise the potential for mineralisation of organic contaminants above groundwater resources. The mineralisation rate measurements for atrazine obtained in this study should be useful in models for the prediction of the contamination threat to groundwater resources.
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Angus, JF, M. Ohnishi, T. Horie, and RL Williams. "A preliminary study to predict net nitrogen mineralisation in a flooded rice soil using anaerobic incubation." Australian Journal of Experimental Agriculture 34, no. 7 (1994): 995. http://dx.doi.org/10.1071/ea9940995.
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Complementary field and laboratory studies were conducted to determine whether laboratory measurements of net nitrogen (N) mineralisation under anaerobic conditions could be used to predict field rates in a flooded soil and N uptake by a rice crop. The laboratory experiment consisted of measurements of ammonium accumulation at 10, 20, 30, and 40�C for 7, 14, and 28 days of anaerobic incubation. There was no accumulation of ammonium at 10�C, but increasing ammonification rate at temperatures of 20�C was observed, except for a slower rate at 40�C after 14 days. Two models were tested on the data: a zero-order reaction in which rate of mineralisation was a linear function of temperature; a first-order reaction in which net N mineralisation rate was a proportion of a depleting pool of labile organic N. In the second model, the rate was also linearly related to temperature. Both models fitted the laboratory data well (R2 = 0.94 and 0.97, respectively), but the second model accounted better for mineralisation at 40�C for the 28-day incubation. These models were then run, using daily mean temperatures over a rice-growing season, to predict net mineralisation in the field. The predictions were compared with measured net N mineralisation in a flooded soil and N uptake by the crop measured throughout the season in the field from which the incubated soil was sampled. Net N mineralisation and crop uptake increased throughout the season, reaching maximum values of 115 and 111 kg N/ha at maturity. The zero-order and first-order models both predicted net N mineralisation accurately until the middle of the season, after which the zero-order model overestimated net N mineralisation but the first-order model predicted the reduction in the rate of net N mineralisation with reasonable accuracy. The close agreement between the laboratory incubations and field measurements of net mineralisation and crop N uptake suggest that incubation tests may provide useful information for including in a model to assist rice growers' decisions about N fertiliser.
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Sgraja, M., J. Bertling, and P. J. Jansens. "Mineralisation von Mikrokapseln." Chemie Ingenieur Technik 75, no. 8 (August 25, 2003): 1114. http://dx.doi.org/10.1002/cite.200390282.
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Ouyang, Lei, Liuqian Yu, and Renduo Zhang. "Effects of amendment of different biochars on soil carbon mineralisation and sequestration." Soil Research 52, no. 1 (2014): 46. http://dx.doi.org/10.1071/sr13186.
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The aim of this study was to determine the impact of addition of different biochars on soil carbon mineralisation and sequestration. Different biochars were produced from two types of feedstock, fresh dairy manure and pine tree woodchip, each of which was pyrolysed at 300, 500, and 700°C. Each biochar was mixed at 5% (w/w) with a forest loamy soil and the mixture was incubated at 25°C for 180 days, during which soil physicochemical properties and soil carbon mineralisation were measured. Results showed that the biochar addition increased soil carbon mineralisation at the early stage (within the first 15 days) because biochar brought available organic carbon to the soil and changed associated soil properties, such increasing soil pH and microbial activity. The largest increase in soil carbon mineralisation at the beginning of incubation was induced by the dairy manure biochar pyrolysed at 300°C. Soil carbon mineralisation was enhanced more significantly by the dairy manure biochars than by the woodchip biochars, and the enhancement effect decreased with increasing pyrolysis temperature. Although the biochar addition induced increased soil carbon mineralisation at the beginning of the incubation, soil carbon mineralisation rates decreased sharply within a short time (within 15 days) and then remained very low afterwards. Carbon mineralisation kinetic modelling indicated that the stable organic matter in biochars could be sequestrated in soil for a long time and resulted in high levels of carbon sequestration, especially for the woodchip biochars pyrolysed from higher temperatures.
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Angus, J. F., T. P. Bolger, J. A. Kirkegaard, and M. B. Peoples. "Nitrogen mineralisation in relation to previous crops and pastures." Soil Research 44, no. 4 (2006): 355. http://dx.doi.org/10.1071/sr05138.
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Most of the nitrogen (N) used by Australian crops is mineralised from the residues of previous crops and pastures. Net N mineralisation was studied in 2 field experiments in southern NSW, one comparing different residue-management and tillage systems during continuous cropping and the other comparing residues of annual and perennial pastures in a pasture–crop system. After 14 years of continuous cropping, soil total N concentration had decreased by 50%. Neither stubble retention nor direct drilling affected potential N mineralisation or the decrease in total N. However, soil mineral N in the field was greater after direct drilling than cultivation and greater after stubble retention than stubble burning. There were 2 reasons for the discrepancy. One was because retained stubble conserved soil water, leading to periods of increased mineralisation. The other was that direct drilling and stubble retention reduced growth and N uptake by crops. In contrast to the similar rates of potential mineralisation under different tillage and stubble systems, there were significant differences following different pasture species. In a 5-year study of a pasture–crop system we measured net mineralisation following annual pasture based on subterranean clover and perennial pasture based on lucerne and/or the grasses phalaris and cocksfoot. Mineralisation generally decreased with number of years after pasture removal. Previous lucerne pastures led to slow net mineralisation in the first year after removal, apparently because of immobilisation by high C : N residues. Mineralisation in soil containing perennial grass residues was the highest measured. This high rate may be due to redistribution of N to the topsoil by roots of perennial grasses. The comparison of continuous crop and pasture–crop systems showed that the decline in soil N supply was not prevented by direct drilling and stubble conservation, but N mineralisation was increased by pastures, particularly those containing perennial grasses.
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Sadras, Victor O., and Jeffrey A. Baldock. "Influence of size of rainfall events on water-driven processes. II. Soil nitrogen mineralisation in a semi-arid environment." Australian Journal of Agricultural Research 54, no. 4 (2003): 353. http://dx.doi.org/10.1071/ar02113.
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Power laws describe the relationships between the number N (s) and the size s of daily rainfall events, i.e. N (s) ~ s–τ, with higher τ corresponding to sites or seasons with greater frequency of small rainfall events. This paper tested the hypothesis that the rate of soil nitrogen mineralisation increases with increasing exponent τ, as affected by both spatial and temporal sources of variation. Rates of nitrogen mineralisation in an uncropped sandy loam soil were calculated using a simulation model with detailed nitrogen and water balances, and long-term weather data for 6 Australian locations in a range of annual rainfall from 260 to 360 mm. Daily rates of mineralisation were calculated using actual rainfall, and variable or fixed temperature and evaporative demand. The annual pattern of mineralisation rate, calculated as a function of rainfall and variable temperature and evaporative demand, was bimodal with peaks in April and November. These peaks disappeared and differences among locations were reduced when the effects of temperature and evaporative demand were removed. Under constant temperature and evaporative demand, mineralisation rates between April and November were 68% greater than rates between December and March. In the former period, characterised by a high frequency of small rainfall events, monthly mineralisation rate was a direct function of the amount of rainfall. In contrast, mineralisation was independent of the amount of rainfall during the period of larger, less frequent rainfall events from December to March. Parameter τ accounted for 75% of the variation in mineralisation rate in the period December–March and it also accounted for a substantial part of the variation between periods.
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Purnomo, Erry, A. S. Black, C. J. Smith, and M. K. Conyers. "The distribution of net nitrogen mineralisation within surface soil. 1. Field studies under a wheat crop." Soil Research 38, no. 1 (2000): 129. http://dx.doi.org/10.1071/sr99058.
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To test the hypothesis that net nitrogen (N) mineralisation is concentrated in the surface few centimetres following minimal soil disturbance for crop establishment, mineralisation was measured during the growth of wheat. The soil was a Red Kandosol located in southern New South Wales. Mineralisation was estimated usingin situ incubations inside capped PVC tubes, which were sampled every 3 weeks. Soil from the tubes was sampled at depth intervals of 2 cm to a depth of 10 cm and at 5-cm intervals from 10 to 20 cm. The results showed that net N mineralisation decreased with depth to 20 cm. Over the season, an average of 32% of the N mineralised in the top 20 cm of soil originated from the 0–2 cm layer, 72% was from the 0–6 cm layer, and only 13% was from soil below 10 cm. The decrease in N mineralisation with soil depth was highly correlated with decreases in the organic carbon (r2 = 0.84, P < 0.05) and total N (r2 = 0.83, P < 0.05) concentration. The soil's N-supplying ability is concentrated near the surface where it is susceptible to erosional loss. The N supply may also be inhibited by temperature and moisture extremes, which are common in the surface few centimetres of soil where mineralisation was concentrated. The PVC enclosures created artefacts in soil temperature and moisture, although it is argued that the effects on net N mineralisation were small in most sampling periods.
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D, Clarson, and Ramaswami P.P. "MINERALISATION PATTERN OF SULPHUR IN DIFFERENT SOIL TYPES." Madras Agricultural Journal 77, February (1990): 70–73. http://dx.doi.org/10.29321/maj.10.a01919.
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The rate of mineralisation of sulphur in soils is higher during the first or second week, when the favourable environmental factors such as noisture and temperature are prevailing. Addition of elemental sulphur stimulates the mineralisation process; as it gives energy to the sulphur oxidising organisms. The rate of mineralisation is lowered after two wooks, probably due to the Immobilisation of sulphur.compounds as they might be assimilated to the microbial tissue.
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Kearney, Michaela, Paul R. Cooper, Anthony J. Smith, and Henry F. Duncan. "Characterisation of miRNA Expression in Dental Pulp Cells during Epigenetically-Driven Reparative Processes." International Journal of Molecular Sciences 24, no. 10 (May 11, 2023): 8631. http://dx.doi.org/10.3390/ijms24108631.
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Within regenerative endodontics, exciting opportunities exist for the development of next-generation targeted biomaterials that harness epigenetic machinery, including microRNAs (miRNAs), histone acetylation, and DNA methylation, which are used to control pulpitis and to stimulate repair. Although histone deacetylase inhibitors (HDACi) and DNA methyltransferase inhibitors (DNMTi) induce mineralisation in dental pulp cell (DPC) populations, their interaction with miRNAs during DPC mineralisation is not known. Here, small RNA sequencing and bioinformatic analysis were used to establish a miRNA expression profile for mineralising DPCs in culture. Additionally, the effects of a HDACi, suberoylanilide hydroxamic acid (SAHA), and a DNMTi, 5-aza-2′-deoxycytidine (5-AZA-CdR), on miRNA expression, as well as DPC mineralisation and proliferation, were analysed. Both inhibitors increased mineralisation. However, they reduced cell growth. Epigenetically-enhanced mineralisation was accompanied by widespread changes in miRNA expression. Bioinformatic analysis identified many differentially expressed mature miRNAs that were suggested to have roles in mineralisation and stem cell differentiation, including regulation of the Wnt and MAPK pathways. Selected candidate miRNAs were demonstrated by qRT-PCR to be differentially regulated at various time points in mineralising DPC cultures treated with SAHA or 5-AZA-CdR. These data validated the RNA sequencing analysis and highlighted an increased and dynamic interaction between miRNA and epigenetic modifiers during the DPC reparative processes.
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English, L. T. P., V. H. Galvan, and C. R. Pullinger. "Geological setting of gold-silver mineralization in the La India mining district, Nicaragua." Naturalis Scientias 01, no. 01 (2024): 41–45. http://dx.doi.org/10.62252/nss.2024.1003.
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La India gold mining district covers a 50 km² area of fault-fill gold-silver mineralized quartz-adularia veins on the western margin of a Tertiary volcanic arc in western Nicaragua. Historic mining records and modern mineral exploration data, which to-date has defined a mineral endowment of over 2.3 Moz gold, provide a wealth of geological information. This paper draws on these observations and data to describe and classify the gold-silver mineralisation at La India, identify the geological controls, and interpret the timing of mineralisation within the regional tectonic setting. The district-scale gold-silver mineralisation at La India occurs in two adjacent geological settings with distinct mineralization characteristics and exploration potential: (1) an upland area of strongly faulted felsic to andesitic volcanics where the historic mine workings are located, and (2) an adjacent downthrown graben, the Sebaco Graben, where a thick sequence of andesite is preserved overlying the felsic volcanic sequence. Gold mineralisation is classified as rift margin-type low-sulphidation epithermal gold-silver fault and fracture-fill vein mineralization. In the historic mining area erosion has exposed the top of the high-grade epithermal zone. Minimal erosion in the Sebaco Graben means that the epithermal system is fully preserved at depth, with localised hydrothermal sinter outcrops, sporadic low-grade mineralised veins and a phreatic breccia pipe exposed at surface. Apart from the one phreatic breccia, the gold-silver mineralisation occurs in quartz veins and breccias that filled brittle faults and associated fractures and fissures which developed in an extensional tectonic setting. The structures containing the gold-silver mineralisation were formed as normal and trans-tensional faults with orientations consistent with southwest-directed extension: (1) a predominant northwest to north-northwest set parallel to the subducting plate; (2) secondary but locally extensive east-west, and (3) tertiary shorter and narrower northeast and north-striking veins. A district-scale north-northwest orientated through-going structure linking the major gold-silver deposits in the historic mining area is interpreted as a deep crustal conduit for the gold-silver bearing hydrothermal fluids. Other, as yet unidentified basement feeder structures may have fed mineralised corridors in the east and west of the district. The gold-silver mineralisation is best developed where structures pass through competent felsic volcanics and welded tuffs in the historic mine area, and also in the overlying andesite flows in the Sebaco Graben. Gold-silver mineralisation is less well developed where the structure passes through less competent unwelded tuffs and volcanic agglomerates. Gold-silver mineralisation is interpreted as occurring shortly before or at 8-10 Ma at the end of a long period of slab-rollback induced extension and arc volcanism. Post-mineralisation block faulting split the La India district into the upthrown, and subsequently eroded historic mine area where epithermal mineralisation is largely exposed at surface, and the well-preserved downthrown blocks such as the Sebaco graben where much of the gold-silver mineralisation is still hidden several hundred metres below surface.
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Baños-González, Manuel A., Juan Calderón-Colmenero, Alberto Aranda-Fraustro, Marco A. Peña-Duque, Marco A. Martínez-Ríos, Benjamín Valente-Acosta, Carlos Linares-López, Hugo Delgado-Granados, and Aurora de la Peña-Díaz. "Aortic mineralisation in children with congenital cardiac disease." Cardiology in the Young 21, no. 5 (June 8, 2011): 551–55. http://dx.doi.org/10.1017/s1047951111000448.
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AbstractBackgroundCongenital cardiac diseases are the most frequent congenital malformations. In adult patients, the mineralisation of the aorta due to cardiovascular disease is very common, but vascular mineralisation in paediatric cardiopathies is a topic less studied. This study shows that children with a complex congenital cardiopathy show a high degree of vascular mineralisation in the ascending aorta. This can be part of the cardiac failure pathophysiology due to congenital cardiopathies.ObjectiveThe aim of this study was to determine the presence and degree of vascular mineralisation in samples of the ascending and descending aorta of children with complex congenital cardiopathies.DesignWe conducted a cross-sectional study.SubjectsWe obtained 34 vascular tissues from the autopsies of 17 children with congenital cardiac disease.MethodsWe used a scanning electron microscope with an energy-dispersive X-ray spectroscopy in order to analyse the vascular tissues.ResultsThe amount of minerals was two times higher in the ascending aorta than in the descending aorta of children with congenital cardiac disease.ConclusionsThe study provides evidence that vascular mineralisation can start at an early age, and that it is higher in the ascending aorta than in the descending aorta.
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Angus, J. F., A. F. van Herwaarden, D. P. Heenan, R. A. Fischer, and G. N. Howe. "The source of mineral nitrogen for cereals in south-eastern Australia." Australian Journal of Agricultural Research 49, no. 3 (1998): 511. http://dx.doi.org/10.1071/a97125.
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The relative importance of soil mineral nitrogen (N) available at the time of sowing ormineralised during the growing season was investigated for 6 crops of dryland wheat. The soil mineral N in the root-zone was sampled at sowing and maturity and the rate of net mineralisation in the top 10 cm was estimated by sequential sampling throughout the growing season, using an in situ method. Mineralisation during crop growth was modelled in relation to total soil N, ambient temperature, andsoil water content. Mineral N accumulated before sowing varied by a factor of 3 between the sites (from 67 to 195 kgN/ha), while the net mineralisation during crop growth varied by a factor of 2 (from 43 to 99 kgN/ha). The model indicated that 0·092% of total N was mineralised per day when temperature and water were not limiting, with rates decreasing for lower temperatures and soil water contents. When tested with independent data, the model predicted the mineralisation rate of soil growing continuous wheat crops but underestimated mineralisation of soil in a clover-wheat rotation. For crops yielding <3 t/ha, the supply of N was mostly from mineralisation during crop growth and the contribution from mineral N accumulated before sowing was relatively small. For crops yielding >4 t/ha, thesupply of N was mostly from N present in the soil at the time of sowing. The implication is that for crops to achieve their water-limited yield, they must be supplied with an amount of N greater than can be expected from mineralisation during the growing season, either from fertiliser or from mineral N accumulated earlier.
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Murphy, D. V., G. P. Sparling, I. R. P. Fillery, A. M. McNeill, and P. Braunberger. "Mineralisation of soil organic nitrogen and microbial respiration after simulated summer rainfall events in an agricultural soil." Soil Research 36, no. 2 (1998): 231. http://dx.doi.org/10.1071/s97043.
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Simulated rainfall events were applied during the summer fallow period to a Western Australian agricultural soil, a loamy sand, under continuous wheat and after the second pasture phase of a 2 pasture : 1 wheat (2P : 1W) rotation. The aims of this study were to determine the change in microbial activity, amount of net and gross nitrogen (N) mineralised, and inorganic N produced after dry soil was re-wet during summer rainfall. Three irrigation treatments were applied: (i) control soils received no water, (ii) the single wet treatment received 45 mm of water on day 0 and was allowed to dry, and (iii) the multiple wet treatment received 45 mm of water on day 0 plus further applications of 5 mm on days 3 and 8. The CO2 production and N mineralisation were measured in the surface 10 cm of soil for a period of 14 days after initial irrigation. Net N mineralisation was measured from in situ incubation of soil cores and gross N mineralisation by 15N isotopic dilution. The CO2 production was measured by infrared gas analysis of air samples taken from a closed headspace above the soil. A large flush in CO2 production and gross N mineralisation occurred immediately after rewetting the dry soil. This response was short-lived and rates of CO2 production and gross N mineralisation declined rapidly after 2 days. After irrigation on day 0, CO2 production was twice as large and gross N mineralisation was slightly larger in the 2P : 1W soil than continuous wheat. Gross N mineralisation and CO2 production were not significantly different in the multiple and single wet treatments after the re-wet on day 3, but an additional flush in activity occurred in the multiple wet treatment after the re-wet on day 8. The patterns of gross N mineralisation and CO2 production corresponded to changes in the soil water content, especially in the surface 2·5 cm of soil. Net and gross N mineralised and gross N immobilised over the 14-day period after the initial re-wet were greater in the multiple wet compared with the single wet treatments under both wheat and 2P : 1W. However, gross N mineralisation was approximately 4-fold greater than net N mineralisation under wheat and 15-fold greater under 2P : 1W. The majority of gross N mineralised after simulated summer rainfall was immobilised which resulted in an increase in inorganic N within the soil profile (0-50 cm) during opening winter rains.
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Armstrong, Katy, André Bardow, Xiangkun Elvis Cao, Flavia Cassiola, Nico Fischer, Colin Hills, Ali Reza Kamali, et al. "Accelerated mineralisation: general discussion." Faraday Discussions 230 (2021): 213–26. http://dx.doi.org/10.1039/d1fd90046c.
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Dunham, K. C. "Pennine mineralisation in depth." Proceedings of the Yorkshire Geological Society 47, no. 1 (September 1988): 1–12. http://dx.doi.org/10.1144/pygs.47.1.1.
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Ineson, P. R. "Mineralisation and Shear Zones." Ore Geology Reviews 7, no. 1 (April 1992): 74–75. http://dx.doi.org/10.1016/0169-1368(92)90021-c.
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Riedel, Stefanie, Daniel Ward, Radmila Kudláčková, Karolina Mazur, Lucie Bačáková, Jemma G. Kerns, Sarah L. Allinson, et al. "Electron Beam-Treated Enzymatically Mineralized Gelatin Hydrogels for Bone Tissue Engineering." Journal of Functional Biomaterials 12, no. 4 (October 8, 2021): 57. http://dx.doi.org/10.3390/jfb12040057.
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Biological hydrogels are highly promising materials for bone tissue engineering (BTE) due to their high biocompatibility and biomimetic characteristics. However, for advanced and customized BTE, precise tools for material stabilization and tuning material properties are desired while optimal mineralisation must be ensured. Therefore, reagent-free crosslinking techniques such as high energy electron beam treatment promise effective material modifications without formation of cytotoxic by-products. In the case of the hydrogel gelatin, electron beam crosslinking further induces thermal stability enabling biomedical application at physiological temperatures. In the case of enzymatic mineralisation, induced by Alkaline Phosphatase (ALP) and mediated by Calcium Glycerophosphate (CaGP), it is necessary to investigate if electron beam treatment before mineralisation has an influence on the enzymatic activity and thus affects the mineralisation process. The presented study investigates electron beam-treated gelatin hydrogels with previously incorporated ALP and successive mineralisation via incubation in a medium containing CaGP. It could be shown that electron beam treatment optimally maintains enzymatic activity of ALP which allows mineralisation. Furthermore, the precise tuning of material properties such as increasing compressive modulus is possible. This study characterizes the mineralised hydrogels in terms of mineral formation and demonstrates the formation of CaP in dependence of ALP concentration and electron dose. Furthermore, investigations of uniaxial compression stability indicate increased compression moduli for mineralised electron beam-treated gelatin hydrogels. In summary, electron beam-treated mineralized gelatin hydrogels reveal good cytocompatibility for MG-63 osteoblast like cells indicating a high potential for BTE applications.
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Parfitt, R. L., G. J. Salt, and S. Saggar. "Effect of leaching and clay content on carbon and nitrogen mineralisation in maize and pasture soils." Soil Research 39, no. 3 (2001): 535. http://dx.doi.org/10.1071/sr00044.
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We conducted a 7-week laboratory incubation experiment to evaluate the effect of leaching on net C and N mineralisation in soils. The soils were collected from adjacent fields of long-term pasture and maize, where each field contained an Inceptisol and an Andisol. The concentration of clay mineral was 200 g/kg halloysite in the Inceptisol and 120 g/kg allophane in the Andisol. Half the samples were leached weekly with 0.002 M CaCl2 at a suction of 20 kPa to remove soluble products, and half were not leached. Carbon mineralisation was determined from CO2-C evolved each week. Net N mineralisation was measured for the leached samples from the NH4-N and NO3-N in the CaCl2 extracts, and for the batch of non-leached samples by extraction in 0.5 M K2SO4. Carbon and net N mineralisation were greater in the soils under pasture than in soils under maize. The proportion of total C mineralised as CO2-C, and of total N mineralised as NH4-N and NO3-N, followed the order Inceptisol-pasture > Inceptisol-maize > Andisol-pasture > Andisol-maize, suggesting that allophane and Al ions reduced net mineralisation. Dissolved organic carbon (DOC) produced during incubation, as a proportion of total C, was greatest for the Inceptisol-maize sample and least for the Andisol-pasture sample. Non-leaching resulted in the accumulation of acids and solutes, and decreased C mineralisation for the Inceptisol samples.
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Sparling, Graham, Robert Dragten, Jackie Aislabie, and Rhonda Fraser. "Atrazine mineralisation in New Zealand topsoils and subsoils: influence of edaphic factors and numbers of atrazine-degrading microbes." Soil Research 36, no. 4 (1998): 557. http://dx.doi.org/10.1071/s97065.
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The mineralisation of 14C-ring-labelled atrazine to 14CO2 was measured in 3 contrasting New Zealand soils under controlled conditions of temperature and moisture. The numbers of atrazine-degrading organisms were measured by a most probable number technique. Decomposition rates were slow, with a maximum of 41% of atrazine being mineralised over 263 days. Mineralisation was generally very low in subsoils and was much reduced by low moisture content. However, one subsoil from 60–90 cm depth had unusually high numbers of atrazine-degrading microbes and showed mineralisation greater than or equivalent to the surface soil. Mineralisation was approximately doubled by a 10°C rise in temperature over the range 16–28°C. In general, the rate of atrazine mineralisation over 7–96 days could be predicted from the number of atrazine-degrading microbes and the cation exchange capacity of the soil (R2 = 0·86). A large amount (54–77%) of 14C remained in the soil as non-extractable residues after 263 days, but only trace amounts of the added atrazine or the decomposition products de-ethyl atrazine and de-isopropyl atrazine were detected by extraction in organic solvent.
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Sienkiewicz, Jadwiga, Grażyna Porębska, Apolonia Ostrowska, and Dariusz Gozdowski. "Indicators of peat soil degradation in the Biebrza valley, Poland." Environmental Protection and Natural Resources 30, no. 2 (June 1, 2019): 41–51. http://dx.doi.org/10.2478/oszn-2019-0009.
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Abstract Peat mineralisation leads to net loss of CO2 to the atmosphere, as well as to release of other elements from the decomposed soil organic matter (SOM) to groundwater. This results in the degradation of peat soils and the ecosystems they support. Here we evaluated the practical indicatory suitability of the existing and proposed new indices for the assessment of peat soil degradation in the Biebrza river valley encompassing, unique on European scale, peatland ecosystems. We studied relationships between soil organic carbon (SOC) and total nitrogen (Ntot), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in a series of degraded peat soils in the Biebrza valley. Samples were taken from soils developed on peat deposits that varied in thickness and the degree of peat decomposition, from undegraded to highly mineralised peats. The relationships between changes in the SOC content and changes in the values of the remaining variables (SOM, Ntot, DOC, DON, C/N ratio), were statistically tested. Linear and non-linear regressions were used to establish the relationships amongst the variables examined. The losses of soil C and N occur independently and differ between stages of peat soil mineralisation. From our study, it results that the peat mineralisation intensity may be estimated based on the loss of SOC. We found that 1% loss of SOC corresponded to 1.028% loss of SOM, regardless of the degree of peat soil mineralisation, whereas SOM solubility, measured by the content of DOC, varied based on the intensity of peat soil mineralisation. The content of DOC decreased with the decrease in the SOC content, whereas the DOC/ SOC ratio increased depending on the intensity of peat decomposition. The C/N ratio is not a reliable indicator of peat mineralisation, because its values are driven not only by the nitrogen natively present in peat soils but also by nitrogen from external sources. The contents of SOC and Ntot did not decrease uniformly during peat decomposition because C and N show various mobility in the processes of SOM mineralisation. We found that the DOC/SOC ratio was most indicative of peat soil mineralisation intensity. © IOŚ-PIB
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Sørensen, Peter, Ingrid K. Thomsen, and Jaap J. Schröder. "Empirical model for mineralisation of manure nitrogen in soil." Soil Research 55, no. 6 (2017): 500. http://dx.doi.org/10.1071/sr17018.
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A simple empirical model was developed for estimation of net mineralisation of pig and cattle slurry nitrogen (N) in arable soils under cool and moist climate conditions during the initial 5 years after spring application. The model is based on a Danish 3-year field experiment with measurements of N uptake in spring barley and ryegrass catch crops, supplemented with data from the literature on the temporal release of organic residues in soil. The model estimates a faster mineralisation rate for organic N in pig slurry compared with cattle slurry, and the description includes an initial N immobilisation phase for both manure types. The model estimates a cumulated net mineralisation of 71% and 51% of organic N in pig and cattle slurry respectively after 5 years. These estimates are in accordance with some other mineralisation studies and studies of the effects of manure residual N in other North European countries.
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N.A Tennakoon and M. de S, Liyanage. "NET N MINERALISATION IN COCONUT/NITROGEN FIXING TREE BASED SYSTEM." CORD 13, no. 01 (June 1, 1997): 34. http://dx.doi.org/10.37833/cord.v13i01.307.
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To study the net N mineralisation rates of coconut/NFT plantations, a field incubation technique was carried out. In this study, four types of NFT i.e. Acacia auriculiformis, Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala and coconut monocropping were selected. Forty plastic tubes were inserted into the soil, to a depth of 15 cm at a distance of 2 m and l m away from coconut palm, for field incubation period of 2 weeks. Similarly another set of forty tubes were inserted for a 4 week field incubation period, after removing the previous set of tubes. Fresh soll samples (same depth) were also taken close to the inserted tubes on the day on which tubes were inserted for the estimation of initial N concentrations in the soil. Mineralised N concentrations were extracted by 2 M KCl and the net N mineralisation rates were calculated.
Net N mineralisation was significantly higher (P= 0.001) 4 weeks after field incubation peniod than 2 weeks and also, the significant higher (P= 0.001) net N mineralisation was shown 2 m away from coconut than l m away from coconut. The highest net N mineralisation (4.9 ‑ 15.5 kgha-1) was found in Gliricidia site than in the other NFT sites, followed by Leucaena > Calliandra > Acacia. The lowest net N mineralisation (1.2 ‑ 2.2 kgha-1) was recorded in the coconut monocrop, either 2 weeks or 4 weeks incubation period. This study clearly indicated that growing NFTs with coconut enhances N availability in coconut lands and Gliricidia being the most promismig.
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Bierlein, Frank P., and Paul K. Smith. "The Touquoy Zone deposit: an example of "unusual" orogenic gold mineralisation in the Meguma Terrane, Nova Scotia, Canada." Canadian Journal of Earth Sciences 40, no. 3 (March 1, 2003): 447–66. http://dx.doi.org/10.1139/e03-002.
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The Touquoy Zone deposit is host to disseminated gold mineralisation in metasiltstones of lower Palaeozoic age. From the close correlation between ore grades and the intersection of favourable stratigraphy and bounding faults, it is apparent that mineralisation is controlled by both structural and lithological influences. Within the ore zone, disseminated gold, arsenopyrite, pyrite, and rare base-metal sulphides are associated with a network of widely spaced, millimetre-scale, quartzcarbonate veinlets. Quasi-pervasive fluid flow and prolonged interaction with the host rocks resulted in a diffuse, but pronounced halo of wall-rock alteration that is characterized by the breakdown of detrital feldspar and metamorphic chlorite and the development of hydrothermal carbonate phases, K-mica, and disseminated sulphides. These mineralogical changes are accompanied by enrichment in CO2, K, Au, As, and S and depletion in Na across the ore zone. Vein formation occurred at between 250° and 350°C and pressures of less than 12 kbar (1 kbar = 100 MPa), corresponding to an estimated depth of between <2.8 and 6 km. Mineralisation resulted from the unmixing of an overpressured (low-salinity, CO2-rich) fluid in response to decreasing pressure during its ascent and penetration into permeable host rocks. Geological and geochemical features of mineralisation in the Touquoy Zone deposit are seen as convincing evidence for a close genetic association between disseminated-style and lode gold mineralisation in orogenic terrains, with the resulting style of mineralisation largely controlled by the overall structural geometry of the mineralising site, rheological properties, permeability and chemical receptiveness of the host rock, and structural level of emplacement.
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Widowati, Ladiyani R., Steven Sleutel, Diah Setyorini, Sukristiyonubowo, and Stefaan De Neve. "Nitrogen mineralisation from amended and unamended intensively managed tropical andisols and inceptisols." Soil Research 50, no. 2 (2012): 136. http://dx.doi.org/10.1071/sr11225.
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Intensive vegetable production systems throughout South East Asia are characterised by large nutrient inputs and low nitrogen (N) use efficiencies. In Indonesia, intensive vegetable production is concentrated on volcanic highland soils starting from an altitude of around 700 m above sea level. We measured potential N mineralisation from soil organic matter and from several representative organic materials in Andisols and Inceptisols with andic properties from Central Java, Indonesia. Unamended soils and soils amended with crop residues, animal manures, and compost were incubated during 3–4 months at 25°C in the laboratory, then we monitored N mineralisation. Relative N mineralisation was significantly smaller in the Andisols (average 3.6 ± 1.0%) than the Inceptisols (7.4 ± 2.9%), and was negatively related to oxalate-extractable aluminium (Alox) (r = –0.749) and soil organic carbon (r = –0.705). This is probably due to the strong protection of organic matter (and organic N) by binding to active Al compounds. Net N mineralisation from the added organic materials was highly variable (ranging from 68.1% for the broccoli residues to 2.6% for tithonia compost), and was best related to the organic N content (r = 0.476). There were no significant correlations between net N mineralisation and biochemical fractions, which we attribute to the large variety of materials used in this study compared with previous studies. The data generated here on N mineralisation potential from soil organic matter, and from a variety of plant materials and animal manures that are commonly used in these intensive vegetable rotations, will allow for the rapid and efficient introduction of N fertiliser advice systems based on balance sheets.
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Goh, K. M., and M. L. Nguyen. "Estimating net annual soil sulfur mineralisation in New Zealand grazed pastures using mass balance models." Australian Journal of Agricultural Research 48, no. 4 (1997): 477. http://dx.doi.org/10.1071/a95123.
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Estimates of net soil sulfur (S) mineralisation of grazed pastures in New Zealand were made using the New Zealand Ministry of Agriculture (MAF) S model and a recently developed simple mass-balance S model. Quantitative estimates of S inputs and outputs in the MAF S model were also compared with those obtained in recent field trials. Results obtained showed that the MAF S model was reasonably accurate in estimating S inputs and outputs and long-term maintenance pasture S requirements but not short-term pasture S requirements, due to the parameters used not accounting for the effects of major factors affecting soil organic S mineralisation. Net annual soil S mineralisation under high-producing pastures estimated by the simple mass-balance model was substantial, ranging from 17·7 to 29·1 kg S/ha · year, thus showing that the mineralisation of soil organic S can be a significant source of S for pasture plant growth. The inclusion of the MAF soil organic S test into the MAF S model may improve short-term S requirements, but the soil organic S test needs to be calibrated with net soil S mineralisation potential, soil types, management practices, and pasture production. Although some of the excreta S that has been transferred to stock camps may be returned to the main grazing area, this excretal S and sulfate leaching losses were found to be major S outputs of the main grazing area. The results suggested that the mineralisation of soil organic S may not be sufficient to replace S losses indefinitely when S fertiliser applications are withheld.
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Knudsen, Christian, Jeroen A. M. Van Gool, Claus Østergaard, Julie A. Hollis, Matilde Rink-Jørgensen, Mac Persson, and Kristoffer Szilas. "Gold-hosting supracrustal rocks on Storø, southern West Greenland: lithologies and geological environment." Geological Survey of Denmark and Greenland (GEUS) Bulletin 13 (October 12, 2007): 41–44. http://dx.doi.org/10.34194/geusb.v13.4972.
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A gold prospect on central Storø in the Nuuk region of southern West Greenland is hosted by a sequence of intensely deformed, amphibolite facies supracrustal rocks of late Mesoto Neoarchaean age. The prospect is at present being explored by the Greenlandic mining company NunaMinerals A/S. Amphibolites likely to be derived from basaltic volcanic rocks dominate, and ultrabasic to intermediate rocks are also interpreted to be derived from volcanic rocks. The sequence also contains metasedimentary rocks including quartzites and cordierite-, sillimanite-, garnet- and biotite-bearing aluminous gneisses. The metasediments contain detrital zircon from different sources indicating a maximum age of the mineralisation of c. 2.8 Ga. The original deposition of the various rock types is believed to have taken place in a back-arc setting. Gold is mainly hosted in garnet- and biotite-rich zones in amphibolites often associated with quartz veins. Gold has been found within garnets indicating that the mineralisation is pre-metamorphic, which points to a minimum age of the mineralisation of c. 2.6 Ga. The geochemistry of the goldbearing zones indicates that the initial gold mineralisation is tied to fluid-induced sericitisation of a basic volcanic protolith. The hosting rocks and the mineralisation are affected by several generations of folding.
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Tiddy, Caroline, Diana Zivak, June Hill, David Giles, Jim Hodgkison, Mitchell Neumann, and Adrienne Brotodewo. "Monazite as an Exploration Tool for Iron Oxide-Copper-Gold Mineralisation in the Gawler Craton, South Australia." Minerals 11, no. 8 (July 26, 2021): 809. http://dx.doi.org/10.3390/min11080809.
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The chemistry of hydrothermal monazite from the Carrapateena and Prominent Hill iron oxide-copper-gold (IOCG) deposits in the IOCG-rich Gawler Craton, South Australia, is used here to define geochemical criteria for IOCG exploration in the Gawler Craton as follows: Monazite associated with IOCG mineralisation: La + Ce > 63 wt% (where La > 22.5 wt% and Ce > 37 wt%), Y and/or Th < 1 wt% and Nd < 12.5 wt%; Intermediate composition monazite (between background and ore-related compositions): 45 wt% < La + Ce < 63 wt%, Y and/or Th < 1 wt%. Intermediate monazite compositions preserving Nd > 12.5 wt% are considered indicative of Carrapateena-style mineralisation; Background compositions: La + Ce < 45 wt% or Y or Th > 1 wt%. Mineralisation-related monazite compositions are recognised within monazite hosted within cover sequence materials that directly overly IOCG mineralisation at Carrapateena. Similar observations have been made at Prominent Hill. Recognition of these signatures within cover sequence materials demonstrates that the geochemical signatures can survive processes of weathering, erosion, transport and redeposition into younger cover sequence materials that overlie older, mineralised basement rocks. The monazite geochemical signatures therefore have the potential to be dispersed within the cover sequence, effectively increasing the geochemical footprint of mineralisation.
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Zhao, Wei, Jin-bo Zhang, Christoph Müller, and Zu-cong Cai. "Effects of pH and mineralisation on nitrification in a subtropical acid forest soil." Soil Research 56, no. 3 (2018): 275. http://dx.doi.org/10.1071/sr17087.
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Effects of pH on nitrification have been explored widely; however, few researchers have investigated the compound effects of pH and mineralisation on nitrification and responsible nitrifiers in subtropical forest soils. An acid subtropical forest soil was subjected to pH treatments by liming for 40 days at 25°C and 60% water holding capacity. After 40 days, gross N transformation rates in the samples were evaluated using the 15N tracing technique and model. Ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) were quantified by quantitative polymerase chain reaction. The results showed that gross rates of mineralisation (P < 0.01), NH4+ oxidation to NO3− (P < 0.01), and dissimilatory NO3− reduction to ammonium (DNRA, P < 0.05) significantly increased with elevated soil pH. The NH4+ oxidation to NO3− rates and N mineralisation rates were significantly correlated (P < 0.05). The abundance of AOB (P < 0.05) but not AOA amoA genes dramatically increased in the elevated pH treatments after 40 days. We suggest that the N mineralisation was sensitive to elevated pH in the subtropical acid forest soil, which increased the supply rate of nitrification substrate and the favourable pH microsites for nitrifiers. Interactions between elevated pH and mineralisation have a synergistic and stimulatory effect on development of AOB and their associated nitrifying activity.
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Di, H. J., G. P. Sparling, R. Lee, and G. N. Magesan. "The effect of mineralisation rates of atrazine in surface and subsurface soils on its groundwater contamination potential." Soil Research 39, no. 1 (2001): 175. http://dx.doi.org/10.1071/sr00004.
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Atrazine is a widely used herbicide for weed control and has been found in groundwater in many countries. The groundwater contamination potential of atrazine in 2 soils on the east coast of the North Island of New Zealand was modelled under 3 scenarios. Scenario 1 used atrazine mineralisation rates as determined in an incubation experiment which showed higher rates of mineralisation in subsoil layers than in surface soils. Scenario 2 assumed a decreasing mineralisation rate with soil depth in proportion to changes in microbial biomass. Scenario 3 used a logistic model to describe atrazine mineralisation rates compared with the first-order model used in Scenarios 1 and 2. The results showed that serious errors could occur when modelling the groundwater contamination potential by assuming a decreasing degradation rates with soil depth, when in fact the degradation rates could be higher in some subsoil layers. A site that had not been exposed to atrazine in the past was shown to have a higher potential for groundwater contamination than a neighbouring site of the same soil which had been treated with atrazine in the past. The groundwater contamination potential was found to be higher in the Te Awa soil than in the Twyford soil due to the longer mineralisation half-lives in the Te Awa soil.
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Sierra, J., G. Loranger-Merciris, L. Desfontaines, and M. Boval. "Aerobic microbial activity in four tropical earthworm-soil systems. A mesocosm experiment." Soil Research 52, no. 6 (2014): 584. http://dx.doi.org/10.1071/sr14034.
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Soil organic matter (SOM) quality and carbon (C) availability may be major features influencing the effect of earthworms on the aerobic processes in clayey tropical soils. In this study, we assessed the effect of an anecic (Polypheretima elongata), an endogeic (Pontoscolex corethrurus) and an epigeic (Eudrilus eugeniae) earthworm on the aerobic microbial activity of two tropical soils, a calcic Vertisol and an acid Ferralsol, with clay content >70% and very different organic C content and SOM stability. The soil–earthworm interaction was studied in a 6-month mesocosm experiment in a greenhouse using soils with and without (control soil) earthworm addition. Potential C mineralisation, actual net nitrogen (N) mineralisation and dehydrogenase activity (DHA), as indicators of the aerobic activity of the soils, and phosphorus (P) availability were determined during the trial. DHA was used as an indicator of the global aerobic activity. Earthworms had little effect on potential C mineralisation but significantly increased actual net N mineralisation. The increase in N mineralisation in the Vertisol was twice as great as, and longer (6 v. 3 months) than for the Ferralsol. Differences between soils for N mineralisation were associated with a less recalcitrant SOM in the Vertisol. Available P increased 10% in the earthworm treatments. Earthworm activity improved N and P availability. DHA was 15 times higher for the Vertisol than for the Ferralsol, but the positive effect of earthworms on DHA was greater for the Ferralsol. This effect was greater for E. eugeniae, probably because of surface burrows generated by this epigeic earthworm, which favoured oxygen entry into the soil. Differences between the two soils were greater for DHA than for C and N mineralisation, and this was observed for the control soils as well as for the earthworm treatments. This indicates that earthworm activity modified the rate of the aerobic processes but it did not affect the intrinsic biological properties of these tropical soils, which were controlled mainly by SOM quality and C availability.
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Paul, K. I., P. J. Polglase, A. M. O'Connell, J. C. Carlyle, P. J. Smethurst, and P. K. Khanna. "Soil nitrogen availability predictor (SNAP): a simple model for predicting mineralisation of nitrogen in forest soils." Soil Research 40, no. 6 (2002): 1011. http://dx.doi.org/10.1071/sr01114.
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A new empirical model (SNAP) combines a simple laboratory measurement of the basal rate of N mineralisation with the modifying effects of daily temperature and water content to predict seasonal and annual rates of mineralisation of forest soils. Short-term (20-60-day) aerobic incubations of either undisturbed or bulked and mixed soil were found suitable for prediction of the basal rate of N mineralisation. Data from laboratory incubations of a range of soils were used to calibrate empirical relationships describing the effects of temperature (Tm) and water (Wm) on rates of N mineralisation. Submodels for predicting daily average temperature (STUF) and water content (SWUF) for up to 3 surface soil layers were developed and used to provide inputs to the Tm and Wm functions, respectively. Inputs required for SNAP are restricted to variables whose values are easily obtained. In addition to the amount of N mineralised during a short aerobic laboratory incubation, other soil properties required are bulk density, gravel and clay content, and upper and lower limits of soil water content. Climatic data required included daily air temperature, rainfall, and solar radiation. Other inputs are slope, leaf area index of the stand, and approximate mass and height of litter. Predicted rates of N mineralisation have been verified using data from 9 native forests, 12 radiata pine plantations, and 12 eucalypt plantations from across southern Australia. Despite the wide range of forest types, soil types, climatic regions, and management systems, predicted annual rates of N mineralisation were in close agreement with those observed in the field, regardless of whether daily soil temperature and water content were predicted (R2 = 0.76, P < 0.001, n�=�127) or observed (R2 = 0.78, P < 0.001, n = 68). Sensitivity analysis showed that it was most important to minimise analytical error in inputs used to calculate the basal rate of N mineralisation (i.e. soil temperature, water content, and N mineralised during laboratory incubation). The model was more sensitive to daily soil temperature than to daily soil water content.
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Murphy, D. V., G. P. Sparling, and I. R. P. Fillery. "Stratification of microbial biomass C and N and gross N mineralisation with soil depth in two contrasting Western Australian agricultural soils." Soil Research 36, no. 1 (1998): 45. http://dx.doi.org/10.1071/s97045.
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The distribution of microbial biomass C and N and the decline in gross N mineralisation and NH4+ consumption with soil depth was investigated in 2 soils with different soil texture and land use. Soils were from an annual pasture on a loamy sand and from a sandy clay loam previously cropped with wheat. Intact soil cores were collected from the surface 0–10 cm in steel tubes and were sampled in 2·5 cm layers. Disturbed soil down to 50 cm was collected in 10 cm sections using a sand auger. Microbial biomass was estimated by chloroform fumigation and 0·5 M K2SO4 extraction. Microbial biomass C was determined from the flush in ninhydrin-positive compounds, and microbial biomass N from the flush in total soluble N after K2S2O8 oxidation. Gross N mineralisation and NH4+ consumption were estimated by 15N isotopic dilution using 15NH3 gas injection to label the soil 14NH4+ pool with 15N. The pattern of distribution of the microbial biomass and the rate of N transformations were similar for both soils. There was a rapid decline in microbial biomass C and N and gross N mineralisation with soil depth. Approximately 55% of the microbial biomass, 70–88% of gross N mineralisation, and 46–57% of NH4+ consumption was in the surface 0–10 cm in both soils. There was also a stratification of microbial biomass and gross N mineralisation within the 0–10 cm layer of intact soil cores. It was estimated that one-quarter of the total microbial biomass and at least one-half of the total gross N mineralisation within the soil profiles (0–50 cm) was located in the surface 2·5 cm layer. These results demonstrate the importance of the surface soil layer as a major source of microbial activity and inorganic N production. There was a strong correlation between the distribution of microbial biomass and the gross rate of mineralisation of soil organic N within the soil profile.
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Vonopartis, L. C., R. Booysen, P. A. M. Nex, J. A. Kinnaird, and L. J. Robb. "Combined satellite and portable XRF exploration mapping of the Zaaiplaats tin field, South Africa." South African Journal of Geology 125, no. 1 (March 1, 2022): 45–60. http://dx.doi.org/10.25131/sajg.125.0006.
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Abstract The Zaaiplaats tin field is host to two of the historically most significant tin mines in South Africa. The geological maps of Zaaiplaats and Groenfontein have not been updated since the 1980s and 1950s respectively and warrant a renewed investigation. Cassiterite is hosted in the Bobbejaankop and Lease granites, of the Zaaiplaats and Groenfontein tin mines, which are part of the Lebowa Granite Suite of the Bushveld Complex. Tin mineralisation is primarily hosted as low-grade disseminations and within networks of high-grade hydrothermal pipes and lenticular ore-bodies. One difficulty in mapping such formations arises from the limited lithological variability between mineralised and unmineralised granitic facies. In order to map the granitic lithologies and discriminate alteration zones, an integrated approach is applied by combining remote sensing and in situ portable X-ray fluorescence (pXRF) mapping. The pXRF large ion lithophile (LIL) element distribution mapping, specifically correlating Rb, Sr and Ba with Sn, points to the concentration of late-stage magmatic-hydrothermal fluids, which are associated with endogranitic mineralisation. The use of the Rb/Ba ratio highlights regions of late-stage magmatic-hydrothermal alteration, effectively delineates granitic facies and identifies zones of potential tin mineralisation. Spectral image processing techniques were used as tools to support the mapping of these granites, their variable degrees of magmatic-hydrothermal alteration and regions of endogranitic disseminated mineralisation. We thus exemplify that an expert-based and synergic approach, combining inexpensive in situ pXRF and freely available satellite remote sensing data, supports the mapping and identification of endogranitic mineralisation in early exploration stages. Furthermore, due to its versatility, this approach can easily be applied to other styles of plutonic mineralisation.
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Sakkas, Panagiotis, Idiegberanoise Oikeh, Damer P. Blake, Sheralyn Smith, and Ilias Kyriazakis. "Dietary vitamin D improves performance and bone mineralisation, but increases parasite replication and compromises gut health in Eimeria-infected broilers." British Journal of Nutrition 122, no. 6 (June 10, 2019): 676–88. http://dx.doi.org/10.1017/s0007114519001375.
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AbstractCoccidial infections reduce fat-soluble vitamin status and bone mineralisation in broiler chickens. We hypothesised that broilers infected with Eimeria maxima would benefit from increased dietary supplementation with vitamin D (vitD) or with 25-hydroxycholecalciferol (25(OH)D3 or 25D3). Broilers were assigned to diets with low (L) or commercial (M) vitD levels (25 v. 100 μg/kg) supplemented as cholecalciferol (D3) or 25D3. At day 11 of age, birds were inoculated with water or 7000 E. maxima oocysts. Pen performance was calculated over the early (days 1–6), acute (days 7–10) and recovery periods (days 11–14) post-infection (pi). At the end of each period, six birds per treatment were dissected to assess long bone mineralisation, plasma levels of 25D3, Ca and P, and intestinal histomorphometry. Parasite replication and transcription of cytokines IL-10 and interferon-γ (IFN-γ) were assessed at day 6 pi using quantitative PCR. Performance, bone mineralisation and plasma 25D3 levels were significantly reduced during infection (P < 0·05). M diets or diets with 25D3 raised plasma 25D3, improved performance and mineralisation (P < 0·05). Offering L diets compromised feed efficiency pi, reduced femur breaking strength and plasma P levels at day 10 pi in infected birds (P < 0·05). Contrastingly, offering M diets or diets with 25D3 resulted in higher parasite loads (P < 0·001) and reduced jejunal villi length at day 10 pi (P < 0·01), with no effect on IL-10 or IFN-γ transcription. Diets with M levels or 25D3 improved performance and mineralisation, irrespective of infection, while M levels further improved feed efficiency and mineralisation in the presence of coccidiosis.
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Strong, D. T., P. W. G. Sale, and K. R. Helyar. "The influence of the soil matrix on nitrogen mineralisation and nitrification III. Predictive utility of traditional variables and process location within the pore system." Soil Research 37, no. 1 (1999): 137. http://dx.doi.org/10.1071/s98042.
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Regression analysis was used to examine the importance of organic nitrogen (%N), soil water content (θv), soil pH, and C: N ratio for predicting N mineralisation in a small field plot. Undisturbed soil cubes (c. 1·7 cm3) were collected from the soil surface and received treatments of drying and rewetting, urea, substrate derived from clover leachate, or no amendment, and were incubated at either –10 or –30 kPa for 20 days. The data confirm the hypothesis that within a small field plot, θv and %N explain most of the variation in net N mineralisation and nitrification. The pore size classes of 0·6–10 and 10–30 µm made disproportionately small and large contributions to N mineralisation, respectively, apparently due to non-uniform distribution of organic N through the pore system. When soluble N substrate was added to the soils, both these pore classes appeared to support mineralisation. We concluded that prior to sampling, the microbial biomass had been more active in the pores 0·6–10 µm, and had nearly exhausted the organic substrates in this pore class, whereas this was not so for the 10–30 µm pore class. Drying and rewetting increased the importance of %N as a predictor of N mineralisation, probably because this treatment disrupted physical protective mechanisms of organic N. Soil pH was generally not a useful predictor of N mineralisation and often seemed to be a dependent rather than an independent variable in relation to nitrification. Neither was C: N ratio a useful predictor of N transformation processes, and this was probably related to physical regulatory mechanisms in the soil.
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Cotti, Silvia, Ann Huysseune, Wolfgang Koppe, Martin Rücklin, Federica Marone, Eva M. Wölfel, Imke A. K. Fiedler, Björn Busse, Antonella Forlino, and P. Eckhard Witten. "More Bone with Less Minerals? The Effects of Dietary Phosphorus on the Post-Cranial Skeleton in Zebrafish." International Journal of Molecular Sciences 21, no. 15 (July 30, 2020): 5429. http://dx.doi.org/10.3390/ijms21155429.
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Dietary phosphorus (P) is essential for bone mineralisation in vertebrates. P deficiency can cause growth retardation, osteomalacia and bone deformities, both in teleosts and in mammals. Conversely, excess P supply can trigger soft tissue calcification and bone hypermineralisation. This study uses a wide range of complementary techniques (X-rays, histology, TEM, synchrotron X-ray tomographic microscopy, nanoindentation) to describe in detail the effects of dietary P on the zebrafish skeleton, after two months of administering three different diets: 0.5% (low P, LP), 1.0% (regular P, RP), and 1.5% (high P, HP) total P content. LP zebrafish display growth retardation and hypomineralised bones, albeit without deformities. LP zebrafish increase production of non-mineralised bone matrix, and osteoblasts have enlarged endoplasmic reticulum cisternae, indicative for increased collagen synthesis. The HP diet promotes growth, high mineralisation, and stiffness but causes vertebral centra fusions. Structure and arrangement of bone matrix collagen fibres are not influenced by dietary P in all three groups. In conclusion, low dietary P content stimulates the formation of non-mineralised bone without inducing malformations. This indicates that bone formation and mineralisation are uncoupled. In contrast, high dietary P content promotes mineralisation and vertebral body fusions. This new zebrafish model is a useful tool to understand the mechanisms underlying osteomalacia and abnormal mineralisation, due to underlying variations in dietary P levels.
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SKARPELIS, N. "Geodynamics and evolution of the Miocene mineralization in the Cycladic - Pelagonian belt, Hellenides." Bulletin of the Geological Society of Greece 34, no. 6 (January 1, 2002): 2191. http://dx.doi.org/10.12681/bgsg.16862.
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The paper aims to provide a sound account of the type of Miocene mineralisations in the Cycladic – Pelagonian belt and their relationship with the geodynamic evolution of the area. Skarn and manto types, epithermal precious and base metals mineralisation, and vein magnesite in ultramafics are associated to distinct stages of the geodynamic evolution of the belt. Extensional tectonics favoured their generation. Late stages of extensional tectonics resulted in the formation of vertical to subvertical NW-SE trending fault zones, which were then used as conduits for ascending hydrothermal fluids. The relationship between the geodynamics and the metallogenetic evolution of the belt is discussed on the basis of available data on the geology of four critical areas: Tinos and Mykonos islands, Laurium and Northern Euboea.
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Prechtel, A., M. Armbruster, and E. Matzner. "Modelling sulphate stream concentrations in the Black Forest catchments Schluchsee and Villingen." Hydrology and Earth System Sciences 7, no. 4 (August 31, 2003): 552–60. http://dx.doi.org/10.5194/hess-7-552-2003.
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Abstract. The sulphate (SO4) released by mineralisation and desorption from soil can play an important role in determining concentrations of SO4 in streams. The MAGIC model was calibrated for two catchments in the Black Forest, Germany (Schluchsee and Villingen) and SO4 concentrations in the streams for the years 2016 and 2030 were predicted. Special emphasis was placed on the dynamics of soil sulphur (S) pools. At Schluchsee, 90% of soil S is stored in the organic S (Sorg) pool, whereas at Villingen, 54% is in the inorganic (Sinorg) pool. The Villingen stream chemistry was modelled successfully by measured Langmuir isotherm parameters (LIPs) for Sinorg. Schluchsee data could not be modelled satisfactorily using measured or freely adapted LIPs only, as the Sinorg pool would have to be more than five times larger than what was measured. With 60.5 mmolc SO4 m-2 yr-1 as internal soil source by mineralisation and the measured LIPs, stream data was modelled successfully. The modelling shows that in these two catchments pre-industrial concentrations of SO4 in runoff can be reached in the next two decades if S deposition decreases as intended under currently agreed national and international legislation. Sorg is the most likely dominant source of SO4 released at Schluchsee. Mineralization from the Sorg pool must be included when modelling SO4 concentrations in the stream. As the dynamics and the controlling factors of S release by mineralisation are not yet clear, this process remains a source of uncertainty for predictions of SO4 concentrations in streams. Future research should concentrate on dynamics of S mineralisation in the field, such that mathematical descriptions of long-term S-mineralisation can be incorporated into biogeochemical models. Keywords: sulphate release, organic S, mineralisation, acidification, recovery, modelling, MAGIC, catchments, predictions, Germany, forest
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Requejo, M. I., M. C. Cartagena, R. Villena, L. Giraldo, A. Arce, F. Ribas, M. J. Cabello, and M. T. Castellanos. "Nitrogen mineralisation in soil after addition of wine distillery waste compost: laboratory and field evaluation." Soil Research 54, no. 2 (2016): 144. http://dx.doi.org/10.1071/sr15031.
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The application of wastes from the wine-distillery industry as source of organic matter and nutrients could be a good option of agricultural management. This study is focused on soil nitrogen (N) mineralisation after addition of compost derived from this industry at different doses (7, 13 and 20 t ha–1). An aerobic soil incubation in controlled conditions was carried out to study N mineralisation from the soil-compost mixture as well as isolating the compost from the soil. The data were fitted to a non-linear regression obtaining low values of potentially mineralisable N (N0) and constants of mineralisation (k) (from 81 to 104 mg kg–1 and from 0.008 to 0.013 L day–1 for the soil-compost mixtures, and from 42 to 71 mg kg–1 and from 0.009 to 0.015 L day–1 for the increasing doses of compost) which indicates that it is a mature compost very resistant to mineralisation. Nitrogen mineralised (NM) in the field during two growing seasons (2011 and 2012) of a melon crop was calculated through a N balance, taking into account N inputs and outputs in the soil-plant system. NM in the unamended plots accounted to 31 kg ha–1 and 24 kg ha–1 in 2011 and 2012, respectively, and increased proportionally to the dose of compost applied until 113 kg ha–1 and 98 kg/ha in the consecutive years. The constants of mineralisation obtained in the laboratory were adjusted by field temperatures to predict NM in the field and a general overestimation was observed. The best estimates were obtained when considering the mixture of soil and compost, which reflects the important role of the soil to evaluate N mineralisation caused by the addition of organic wastes.
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Chiba de Castro, WA, MB Cunha-Santino, and I. Bianchini Junior. "Anaerobic decomposition of a native and an exotic submersed macrophyte in two tropical reservoirs." Brazilian Journal of Biology 73, no. 2 (May 2013): 299–307. http://dx.doi.org/10.1590/s1519-69842013000200010.
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Some aquatic plants have fast metabolism and growth, even at sub-optimal conditions, and become dominant in lentic environments such as large reservoirs, altering the nutrient cycle and impairing their environmental quality. There is great need in the knowledge impact processes of invasive species in aquatic environments, among the major, those related to the decomposition. This study evaluated the anaerobic decomposition of invasive submerged macrophytes Egeria densa Planch, native, and Hydrilla verticillata (L.f.) Royle, exotic in Porto Primavera and Jupiá reservoirs, Paraná basin. We evaluated the decay of organic matter, humification degree of the leached material, electrical conductivity and pH of the decomposition process. Mathematical models were utilised to describe the decomposition patterns over time. Both species showed the same heterogeneous pattern of decay of organic matter and carbon mineralisation. The models of carbon mineralisation, compared with the experimentally obtained data presented were adequate. Both species show no significant differences in the decomposition processes. Incubations of both species presented rapid t ½ for POC mineralisation and low DOC mineralisation.
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Purnomo, Erry, A. S. Black, and M. K. Conyers. "The distribution of net nitrogen mineralisation within surface soil. 2. Factors influencing the distribution of net N mineralisation." Soil Research 38, no. 3 (2000): 643. http://dx.doi.org/10.1071/sr99059.
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This investigation examined the magnitude of gradients in net nitrogen (N) mineralisation through the surface 20 cm of soils used for cropping, and factors influencing these gradients. Soils used were W (Red Kandosol) from a previous field study, CT (conventional tillage) and DD (direct drilled) from a long-term rotation experiment on a Red Kandosol, and YS (Yellow Sodosol) from under wheat established by reduced tillage. Soil was collected in 2-cm intervals to a depth of 10 cm and at 5-cm intervals between depths of 10 and 20 cm. All depths were used from soil W but only depths of 0–2, 8–10, and 15–20 cm were used for the remaining soils. Soils were incubated for 0, 2, 4, 8, and 16 weeks under controlled conditions (soil water, 80% of water-holding capacity; temperature, 20˚C; aeration, 1 h/week). Net N mineralisation and carbon dioxide (CO2) evolution were measured. Heterotrophic activity as measured by CO2 evolution decreased with depth but was still evident in soil from below 10 cm. This activity was strongly correlated with the concentration of organic carbon (C) (r = 0.88, P < 0.05) and soil pH (r = 0.80, P < 0.05). The percentage of organic C released as CO2 was highly correlated with pH (r = 0.86, P < 0.05), implying that, when sampled at an appropriate scale, acidity limits heterotrophic activity. Net N mineralisation decreased with depth in all soils. In soil W, 59% of net N mineralised originated from 0 to 2 cm, 87% was from the surface 6 cm, and only 1% was from below 10 cm. This was similar to the distribution of net N mineralisation found in the field experiment reported in the previous paper. Net N mineralisation was correlated with CO2 evolution (r = 0.97, P < 0.01) and pH (r = 0.73, P < 0.05). The C : N ratio increased from 18 in the surface 6 cm to 27 between 10 and 20 cm. The lack of net N mineralisation below 10 cm was attributed to this increase in the C : N ratio. This is the first observation of gradients in net N mineralisation with depth at this scale in different tillage systems.
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Aislabie, J., D. Hunter, J. Ryburn, R. Fraser, G. L. Northcott, and H. J. Di. "Atrazine mineralisation rates in New Zealand soils are affected by time since atrazine exposure." Soil Research 42, no. 7 (2004): 783. http://dx.doi.org/10.1071/sr03096.
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To understand more clearly the groundwater contamination potential of herbicides applied to New Zealand soils, experimental field plots were established on 2 different soil types: Himatangi, a sandy dune soil, and Kiripaka, a silty clay derived from basalt. A mix of triazine herbicides, containing atrazine, terbuthylazine, and hexazinone, was applied to the plots at 10 kg a.i./ha. At various times after application, soil was removed from the plots and analysed for residual levels of herbicides, in vitro rates of mineralisation of 14C-ring-labelled atrazine, and numbers of atrazine-degrading microbes. Atrazine and terbuthylazine were below detectable levels (<0.01 mg/kg) in Himatangi topsoil 18 months after pesticide application but still detectable in topsoil from the Kiripaka site. Hexazinone was detectable in topsoil from both soil plots 18 months after application. Atrazine adsorption isotherms were constructed for topsoil and subsoil from both plots, with estimated Kf values ranging from 0.53 to 4.69 μg1–n mLn/g. A single application of atrazine was sufficient to enhance the rate of 14C-atrazine mineralisation in vitro by topsoil from both plots, and subsoil from the Kiripaka site. Rates of mineralisation of atrazine in the soil from the plots increased 1–6 months after pesticide application and remained elevated for 18–24 months. The numbers of atrazine degraders detected did not correlate with atrazine mineralisation rates. An atrazine-degrading bacterium, identifed as Arthrobacter nicotinovorans, was isolated from Himatangi soil exhibiting enhanced rates of atrazine-mineralisation activity.