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1
Kogan, Marcelo, Alejandra Metz e Rodrigo Ortega. "Adsorption of glyphosate in chilean soils and its relationship with unoccupied phosphate binding sites". Pesquisa Agropecuária Brasileira 38, n. 4 (aprile 2003): 513–19. http://dx.doi.org/10.1590/s0100-204x2003000400010.
Testo completoAbstract (sommario):
The objective of this work was to investigate glyphosate adsorption by soils and its relationship with unoccupied binding sites for phosphate adsorption. Soil samples of three Chilean soils series - Valdivia (Andisol), Clarillo (Inceptisol) and Chicureo (Vertisol) - were incubated with different herbicide concentrations. Glyphosate remaining in solution was determined by adjusting a HPLC method with a UV detector. Experimental maximum adsorption capacity were 15,000, 14,300 and 4,700 mg g¹ for Valdivia, Clarillo, and Chicureo soils, respectively. Linear, Freundlich, and Langmuir models were used to describe glyphosate adsorption. Isotherms describing glyphosate adsorption differed among soils. Maximum adjusted adsorption capacity with the Langmuir model was 231,884, 17,874 and 5,670 mg g-1 for Valdivia, Clarillo, and Chicureo soils, respectively. Glyphosate adsorption on the Valdivia soil showed a linear behavior at the range of concentrations used and none of the adjusted models became asymptotic. The high glyphosate adsorption capacity of the Valdivia soil was probably a result of its high exchangeable Al, extractable Fe, and alophan and imogolite clay type. Adsorption was very much related to phosphate dynamics in the Valdivia soil, which showed the larger unoccupied phosphate binding sites. However relationship between unoccupied phosphate binding sites and glyphosate adsorption in the other two soils (Clarillo and Chicureo) was not clear.
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Peng, Shimeng, Pei Wang, Lanfang Peng, Tao Cheng, Weimin Sun e Zhenqing Shi. "Predicting Heavy Metal Partition Equilibrium in Soils: Roles of Soil Components and Binding Sites". Soil Science Society of America Journal 82, n. 4 (17 maggio 2018): 839–49. http://dx.doi.org/10.2136/sssaj2018.03.0104.
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Gustafsson, Jon Petter, Charlotta Tiberg, Abubaker Edkymish e Dan Berggren Kleja. "Modelling lead(II) sorption to ferrihydrite and soil organic matter". Environmental Chemistry 8, n. 5 (2011): 485. http://dx.doi.org/10.1071/en11025.
Testo completoAbstract (sommario):
Environmental contextLead(II) is a toxic metal pollutant with many anthropogenic sources. We show that lead(II) is bound more strongly to soil surfaces than previously understood. This knowledge may lead to better models for lead(II) dissolution from the soils, which will improve risk assessments for this metal. AbstractLead(II) adsorption to soil organic matter and iron (hydr)oxides is strong, and may control the geochemical behaviour of this metal. Here, we report the adsorption of Pb2+ (i) to 2-line ferrihydrite, and (ii) to a mor layer. The results showed that ferrihydrite has heterogeneous Pb2+ binding. Use of a surface complexation model indicated that ~1 % of the surface sites adsorbed Pb2+ more strongly than the remaining 99 %. Although only one surface complexation reaction was used (a bidentate complex of the composition (≡FeOH)2Pb+), three classes of sites with different affinity for Pb2+ were needed to simulate Pb2+ binding correctly over all Pb/Fe ratios analysed. For the mor layer, Pb2+ sorption was much stronger than current models for organic complexation suggest. The results could be described by the Stockholm Humic Model when the binding heterogeneity was increased, and when it was assumed that 0.2 % of the binding sites were specific for Pb. Use of revised model parameters for nine Vietnamese soils suggest that lead(II) binding was more correctly simulated than before. Thus, underestimation of lead(II) sorption to both (hydr)oxide surfaces and organic matter may explain the failure of previous geochemical modelling attempts for lead(II).
4
Naidu, R., S. Mcclure, NJ Mckenzie e RW Fitzpatrick. "Soil solution composition and aggregate stability changes caused by long-term farming at four contrasting sites in South Australia". Soil Research 34, n. 4 (1996): 511. http://dx.doi.org/10.1071/sr9960511.
Testo completoAbstract (sommario):
The effect of long-term farming on the cation exchange capacity (CEC), organic carbon content, soil solution composition, and aggregate stability was investigated using contrasting soils from 4 sites in the Mid North of South Australia. Undisturbed and farmed profiles were characterised at each site. Farming led to a 10–50% decrease, approximately, in organic matter and CEC in the surface horizon. Scanning electron microscopic study of the surface and selected subsurface soils revealed poor aggregation, compaction, reduced porosity, and a decrease in aggregate particle size in the farmed surface soils. Intra-aggregate binding in the undisturbed soils appeared to be largely due to fungal hypha, with the roots largely contributing to inter-aggregate binding of soil particles. Electrical conductivity (EC) of soil solutions was generally 2–3 times higher in the undisturbed soils than farmed soils, suggesting increased leaching of ions associated with loss of tree cover. This was also supported by a decrease in the concentrations of mobile ions such as Cl-and Na+ in the farmed soils. The concentrations of Na+ and K+ decreased with farming leading to a decrease in the Gapon selectivity constant for Na–Ca and K–Ca exchange. The changes in soil solution composition together with the decline in organic matter concentrations resulted in increased sensitivity of soils to dispersion.
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Ghabbour, Elham A., Geoffrey Davies, Nadeem K. Ghali e Matthew D. Mulligan. "The effect of temperature on tight metal binding by peat and soil derived solid humic acids". Canadian Journal of Soil Science 81, n. 3 (1 agosto 2001): 331–36. http://dx.doi.org/10.4141/s00-065.
Testo completoAbstract (sommario):
The brown biomaterials called humic acids (HA) in peats and soils retain water and bind metal cations and other solutes. Studies of the interactions of purified solid peat and soil-derived HA from different countries with metal cations in water probe HA microstructures and help to characterize the metal binding sites. Labile cations such as Caaq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ tightly bind to solid HAs in sequential steps. The isotherms A vs. c are well fitted with the Langmuir model and plots of 1/A vs. 1/c are linear for each step. Here, A is mmol bound metal g–1 HA and c is the equilibrium cation concentration (M). This paper compares the stoichiometric site capacities vi and equilibrium constants Ki for tight binding of Ca aq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ at different solid HA sites. Measurements at different temperatures give linearly correlated metal binding enthalpy and entropy changes, indicating that conformational changes and cation/HA hydration/dehydration are important factors in metal binding and release by solid HAs. Key words: Humic acids; metal binding; isotherms; thermodynamics
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Kayler, Z. E., M. Kaiser, A. Gessler, R. H. Ellerbrock e M. Sommer. "Application of <i>δ</i><sup>13</sup>C and <i>δ</i><sup>15</sup>N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms". Biogeosciences Discussions 8, n. 2 (1 marzo 2011): 1985–99. http://dx.doi.org/10.5194/bgd-8-1985-2011.
Testo completoAbstract (sommario):
Abstract. Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. We used the δ13C and δ15N isotopic signatures from two organic matter (OM) fractions from soil to identify the likely binding mechanisms involved. We used OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1) OM separated chemically with sodium pyrophosphate (OM(PY)) and (2) OM stabilized in microstructures found in the chemical extraction residue (OM(ER)). Furthermore, because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms within these soils. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established proxies of different binding mechanisms. Parsing soil OM into different fractions is a systematic method of dissection, however, we are primarily interested in how OM is bound in soil as a whole, requiring a means of re-assembly. Thus, we implemented the recent zonal framework described by Kleber et al. (2007) to relate our findings to undisturbed soil. The δ15N signature of OM fractions served as a reliable indicator for microbial processed carbon in both arable and forest land use types. The δ13C signature of OM fractions in arable sites did not correlate well with proxies of soil mineral properties while a consistent pattern of enrichment was seen in the δ13C of OM fractions in the forest sites. We found a significant difference in δ13C of pooled OM fractions between the forest and arable land use type although it was relatively small (<1‰). We found different binding mechanisms predominate in each land use type. The isotopic signatures of OM fractions from arable soils were highly related to the clay and silt size particles amount while organic matter not directly bound to mineral surfaces in the contact zone was involved in cation bonding with Ca. In forest soils, we found a relationship between isotopic signatures of OM(PY) and the ratio of soil organic carbon content to soil surface area (SOC/SSA). For arable soils, the formation of OM(PY)-Ca-mineral associations seems to be a relevant OM stabilization mechanism while the OM(PY) of forest soils seems to be separated from layers of slower exchange not directly attached to mineral surfaces. This means there is a potential to build multiple OM layers on mineral particles in the arable soil and thus the potential for carbon accumulation.
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Burlakovs, Juris, Raimonds Kasparinskis e Maris Klavins. "Leaching of Contamination from Stabilization/Solidification Remediated Soils of Different Texture". Scientific Journal of Riga Technical University. Environmental and Climate Technologies 9, n. 1 (1 settembre 2012): 12–16. http://dx.doi.org/10.2478/v10145-012-0011-0.
Testo completoAbstract (sommario):
Abstract Development of soil and groundwater remediation technologies is a matter of great importance to eliminate historically and currently contaminated sites. Stabilization/solidification (S/S) refers to binding of waste contaminants to a more chemically stable form and thus diminishing leaching of contamination. It can be performed using cement with or without additives in order to stabilize and solidify soil with the contamination in matrix. A series of experiments were done to determine leaching properties of spiked soils of different texture bound with cement. Results of experiments showed, that soil texture (content of sand, silt and clay particles) affects the leaching of heavy metals from stabilized soils.
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Taillon, K. M., e W. H. Hendershot. "Measurement and modeling of surface charge and cation binding in agricultural soil". Canadian Journal of Soil Science 88, n. 5 (1 novembre 2008): 749–59. http://dx.doi.org/10.4141/cjss07076.
Testo completoAbstract (sommario):
Models of metal adsorption have typically been developed and tested for soil components rather than whole soils and at cation concentrations higher than usual environmental conditions. This study investigates whether the non-ideal consistent competitive adsorption (NICA) model can be applied to ion binding in whole soils at low total metal concentrations. Surface charge was measured for 18 agricultural soils from southern Quebec over the pH range 3.5 to 8. The adsorption of Ca, Cd, Cu, Pb and Zn was also measured for three total metal concentrations of 2, 5 and 10 mg L-1 at pH 6 in a 0.005 M Ca(ClO4)2 solution. NICA model parameters were solved for each soil using the surface charge and adsorption data and a non-linear least squares fitting routine. Two types of binding sites were identified: the first type had a pKa near 4 while the second type had a pKa near 7.5. The first type of binding site contributed the greater proportion of the variable charge over most of the pH range, and the second site was unimportant at the lower pHs. The surface charge was accurately described by the NICA model with a mean R2 of 0.995. A mean of the surface charge parameters describing H+ binding accounted for more than 95% of the variable charge on the soils. For individual soils, the NICA model gave a fit to the experimental data with mean R2 values for Ca, Cd, Cu, Pb and Zn of 1.00, 0.906, 0.879 (two concentrations only), 0.825 and 0.918 respectively. When mean adsorption parameters, instead of values determined for each soil individually, are used, the model gave mean R2s for Ca, Cd, Cu, Pb and Zn of 0.938, 0.941, 0.998 (two concentrations only), 0.978 and 0.935. It seems that the NICA model can be used to describe the surface charge and adsorption of cations by whole soils. The mean adsorption parameters appear to describe the adsorption behavior of the soil nearly as well as the individually fitted parameters. This implies that mean parameters for these agricultural soils may provide satisfactory predictions for the adsorption behavior of similar soils. Key words: NICA model, NICCA, surface charge, cation binding, agricultural soil
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Liu, Paiyu, Pei Wang, Yang Lu, Yang Ding, Guining Lu, Zhi Dang e Zhenqing Shi. "Modeling kinetics of heavy metal release from field-contaminated soils: Roles of soil adsorbents and binding sites". Chemical Geology 506 (febbraio 2019): 187–96. http://dx.doi.org/10.1016/j.chemgeo.2018.12.030.
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Peng, Lanfang, Zhenqing Shi, Pei Wang, Wei Li, Zhang Lin, Zhi Dang e Donald L. Sparks. "A novel multi-reaction model for kinetics of Zn release from soils: Roles of soil binding sites". Journal of Colloid and Interface Science 514 (marzo 2018): 146–55. http://dx.doi.org/10.1016/j.jcis.2017.12.006.
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Lee, Younji, Minseok Park e Seunghun Hyun. "Leaching Behavior of Metallic Elements from Abandoned Mine Sites in Varying Environmental Factors". Institute of Life Science and Natural Resources 30 (31 dicembre 2022): 87–100. http://dx.doi.org/10.33147/lsnrr.2022.30.1.87.
Testo completoAbstract (sommario):
Improper management of abandoned mine sites can cause heavy metal contamination of down-gradient agricultural soil, groundwater, and surface water. In this study, we investigated the effects of changes in environmental factors on the leaching behavior of the heavy metals and suggested future research direction for better risk management of the abandoned mine sites under climate change. Numerous studies showed that the concentration of heavy metals in the leachate frequently exceed the environmental criteria even though the leachable heavy metal was negligible (< 1 % of the total concentration), which indicates that mine soils can be long-term resources of contamination. From the result of batch and column experiments, it has been found that soil properties (e.g., soil pH, redox potential, etc.) affect the leaching behavior by solubility change, complex formation, precipitation, etc. Two-site kinetic leaching models were mainly applied for understanding nonequilibrium leaching behavior of the metals due to heterogeneous physical structure and various binding sites of the soil. Meanwhile, it was also reported that the change in hydrodynamic properties due to rainfall pattern can influence leaching behavior by changing the interfacial interaction between soil and water. Several researchers recognized that extreme weather condition (high temperature and increased drought period) due to climate change can elevate initial leaching concentration of the heavy metal. In reality, climate change can cause the nonequilibrium leaching of the metals by influencing hydrodynamic condition and chemical stability of the soil system. Therefore, future works to precisely predict the heavy metal leaching behavior across abandoned mine sites are necessary and risk management of these sites in response to climate change should be designed.
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Adams, M. L., D. J. Hawke, N. H. S. Nilsson e K. J. Powell. "The relationship between soil solution pH and Al3+concentrations in a range of South Island (New Zealand) soils". Soil Research 38, n. 1 (2000): 141. http://dx.doi.org/10.1071/sr98095.
Testo completoAbstract (sommario):
Concentrations of Al3+ were calculated in soil solutions from concentrations of the monomeric ‘reactive Al’ species ([Al3+] + [Al(OH)2+] + [Al(OH)2+] + [AlF2+]) obtained using a recently reported flow injection analysis (FIA) chelating resin technique. Soil solution samples came from 7 sites encompassing a range of New Zealand soils (Brown, Gley, Pallic, Podzol, and Recent Soils) and vegetation types (pasture, shrub lands, and indigenous and exotic forest). Previously published data from a further 7 sites, obtained using a rapid (7 s) FIA technique, were transformed to give compatible results. The resultant data (n = 85) covered the pH range 2.7–7.6, and showed a single curvilinear relationship for log [Al3+] v. soil solution pH, regardless of vegetation or soil type. At pH >5.6, the data had a slope of –2.98 and fell between the amorphous Al(OH)3 and gibbsite solubility lines. At pH <5.0, the data had a slope of –0.46; further, the soil solutions were under-saturated with respect to both minerals. These results are interpreted as indicating control of Al solubility by Al(OH)3 (s) (at pH >5.6) and soil organic matter (at pH <5.0), respectively. This interpretation is supported by data from a pH-dependent Al–fulvic acid binding curve, for which calculated values of [Al3+] follow the same curvilinear relationship determined from the soil solution samples.
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Longstaffe, James G., Denis Courtier-Murias, Ronald Soong, Myrna J. Simpson, Werner E. Maas, Michael Fey, Howard Hutchins et al. "In-Situ Molecular-Level Elucidation of Organofluorine Binding Sites in a Whole Peat Soil". Environmental Science & Technology 46, n. 19 (12 settembre 2012): 10508–13. http://dx.doi.org/10.1021/es3026769.
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Yoon, Tae H., Hichung Moon, Yeong J. Park e Kyoung K. Park. "Investigation of Metal Binding Sites on Soil Fulvic Acid Using Eu(III) Luminescence Spectroscopy". Environmental Science & Technology 28, n. 12 (novembre 1994): 2139–46. http://dx.doi.org/10.1021/es00061a023.
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Yao, Xin, Chuntian Su, Tuantuan Fan, Haoyu Ren e Fei Luo. "Investigating the Binding Properties between Strontium and Dissolved Organic Matter under the Influence of pH and Ca2+ in a Typical Karst Area, China". Land 11, n. 9 (23 agosto 2022): 1376. http://dx.doi.org/10.3390/land11091376.
Testo completoAbstract (sommario):
Due to the unique hydrogeological environment of karst areas, pollutants are more likely to enter the soil and water, showing a special migration and transformation behavior. In this work, the binding behaviors between strontium (Sr2+) and dissolved organic matter (DOM) extracted from soil under the influence of pH and Ca2+ in a typical karst area were investigated by applying three-dimensional fluorescence spectroscopy combined with parallel factor analysis (EEM–PARAFAC) and two-dimensional correlation analysis (2D-COS) of synchronous fluorescence spectra (SF). The results show that DOM extracted from soil was dominated by tryptophan-like and tyrosine-like materials (77% in total). Two-dimensional COS of SF showed that the tryptophan-like substance in DOM extracted from soil preferentially bound to Sr2+. When the pH was 7, the binding coefficient (logKa) of the four DOM components ranged from 2.69 to 4.04, which was more conducive to the binding of DOM extracted from soil and Sr2+ than under acidic and alkaline conditions. Ca2+ in soil weakened the binding of DOM extracted from soil to Sr2+ by competing for binding sites and changing the molecular surface potential. This research is helpful for acknowledging the migration and transformation of Sr2+ and offers a reference for groundwater protection in karst areas.
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Olagoke, Folasade K., Klaus Kaiser, Robert Mikutta, Karsten Kalbitz e Cordula Vogel. "Persistent Activities of Extracellular Enzymes Adsorbed to Soil Minerals". Microorganisms 8, n. 11 (16 novembre 2020): 1796. http://dx.doi.org/10.3390/microorganisms8111796.
Testo completoAbstract (sommario):
Adsorption of extracellular enzymes to soil minerals is assumed to protect them against degradation, while modifying their activities at the same time. However, the persistence of the activity of adsorbed enzymes remains poorly understood. Therefore, we studied the persistence of cellulase and α-amylase activities after adsorption to soil amended with various amounts (+1, +5, and +10 wt.%) of three typical soil minerals, montmorillonite, kaolinite, and goethite. Soil without mineral addition (pure soil), pure minerals, and pure dissolved enzymes were used as references. Soil mineral–enzyme complexes were prepared and then incubated for 100 days; temporal changes in enzyme activities were analyzed after 0, 0.1, 1, 10, and 100 days. The specific enzyme activities (activities normalized to protein content) and their persistence (activities relative to activities at day 0) were compared to enzyme activities in solution and after sorption to the control soil. Amylase adsorption to pure minerals increased in the following order: montmorillonite > kaolinite > goethite. That of cellulase increased in the following order: goethite > montmorillonite > kaolinite. Adsorption of enzymes to soils did not increase in the same order of magnitude as the addition of reactive binding sites. Based on inverse relationships between the amount of enzyme adsorbed and the specific enzyme activity and their persistency, we showed that a limited availability of sorption sites is important for high specific activity and persistence of the enzymes. This is probably the consequence of less and weaker bonds, as compared to a high availability of sorption sites, resulting in a smaller impact on the active sites of the enzyme. Hence, we suppose that the soil mineral phase supports microorganisms in less-sorptive environments by saving energy on enzyme production, since small enzyme release could already result in sufficient activities to degrade respective target carbon substrates.
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Anđelković, Tatjana, Ružica Nikolić, Aleksandar Bojić, Darko Anđelković e Goran Nikolić. "Binding of cadmium to soil humic acid as a function of carboxyl group content". Macedonian Journal of Chemistry and Chemical Engineering 29, n. 2 (15 dicembre 2010): 215. http://dx.doi.org/10.20450/mjcce.2010.168.
Testo completoAbstract (sommario):
The binding of Cd(II) to soil humic acid (HA) at pH 6.5 and in 0.1 mol/L KNO3 ionic medium, was studied by potentiometric titration with a cadmium ion selective electrode. The influence of carboxyl groups in cation-humic interactions was investigated by selective blocking of humic acid carboxyl groups with thionyl chloride and methanol. Infrared spectroscopic analysis confirmed that esterification took place. Differences between underivatized and derivatized HA complexation properties are ascribed to carboxyl groups. The Scatchard plots and incremental formation constants were used to obtain values for Cd-binding constants, for both HAs. The derivatization decreased the number of HA complexing sites by approximately 60 %, which correlates with acid-base properties of both HAs, studied by barium hydroxide and calcium acetate exchange methods. The stability constants for binding at the strongest sites (logKINT) was larger for underivatized HA (5.40) than for derivatized HA (4.92), indicating greater stability in the case when carboxyl groups are involved in complexation reaction.
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Liang, Shuai, Shengguang Cao, Changrong Liu, Shah Zeb, Yu Cui e Guoxin Sun. "Heavy metal adsorption using structurally preorganized adsorbent". RSC Advances 10, n. 12 (2020): 7259–64. http://dx.doi.org/10.1039/d0ra00125b.
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Bless, Aplena Elen S., Samen Baan e Yahya Darmawan. "Spatial Distribution of Trace Elements in Rice Field at Prafi District Manokwari". Indonesian Journal of Geography 48, n. 1 (2 agosto 2016): 1. http://dx.doi.org/10.22146/ijg.12430.
Testo completoAbstract (sommario):
Mapping spatial variability of trace elements in rice Ḁeld is necessary to obtain soil quality information to en-hance rice production. ἀis study was aimed to measure concentration and distribution of Zn, Cu, Fe, Pb, and Cd in two diᴀerent sites (SP1, SP2) of PraḀ rice Ḁeld in Manokwari West Papua. ἀe representative 26 soil samples were analysed for their available trace metal concentration (DTPA), soil pH, and C-organic and soil texture. ἀe result indicated that Fe toxicity and Zn deḀcient problems were encountered in both sites. Rice Ḁeld in SP2 was more deḀcient in Zn than SP1. Site with the highest trace elements (Zn, Fe, Cu, and Cd) concentration had low soil pH and high C-organic. Acidic soil has higher solubility of metals; while high C-organic could improve the formation of dissolve organic carbon-metal binding, hence it improving the trace metals concentration in soil solution.
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Schrumpf, M., K. Kaiser, G. Guggenberger, T. Persson, I. Kögel-Knabner e E. D. Schulze. "Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals". Biogeosciences 10, n. 3 (13 marzo 2013): 1675–91. http://dx.doi.org/10.5194/bg-10-1675-2013.
Testo completoAbstract (sommario):
Abstract. Conceptual models suggest that stability of organic carbon (OC) in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Density fractionation is a useful tool to study the relevance of OC stabilization in aggregates and in association with minerals, but it has rarely been applied to full soil profiles. We aim to determine factors shaping the depth profiles of physically unprotected and mineral associated OC and test their relevance for OC stability across a range of European soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF) were analysed for OC, total nitrogen (TN), δ14C, and Δ14C. Bulk samples were also incubated to determine CO2 evolution per g OC in the samples (specific mineralization rates) as an indicator for OC stability. Depth profiles of OC in the light fraction (LF-OC) matched those of roots for undisturbed grassland and forest sites, suggesting that roots are shaping the depth distribution of LF-OC. Organic C in the HF declined less with soil depth than LF-OC and roots, especially at grassland sites. The decrease in Δ14C (increase in age) of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. The LF at three sites were rather depleted in 14C, indicating the presence of fossil material such as coal and lignite, probably inherited from the parent material. At the other sites, modern Δ14C signatures and positive correlations between specific mineralization rates and fLF-OC indicate the fLF is a potentially available energy and nutrient source for subsurface microorganisms throughout the profile. Declining specific mineralization rates with soil depth confirm greater stability of OC in subsoils across sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining specific mineralization rates with increasing contributions of HF-OC to bulk soil OC, and the low Δ14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. While quantitatively less important than OC in the HF, consistent older ages of oLF-OC than fLF-OC suggest that occlusion of LF-OC in aggregates also contributes to OC stability in subsoils. Overall, our results indicate that association with minerals is the most important factor in stabilization of OC in soils, irrespective of vegetation, soil type, and land use.
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Oyediran, Ibrahim A., e Oluwasegun Y. Mikail. "Geotechnical Characterization and Stabilization of Gully Erosion Soils at Auchi, Anambra Basin Southeastern Nigeria". Environmental and Earth Sciences Research Journal 9, n. 3 (28 settembre 2022): 90–97. http://dx.doi.org/10.18280/eesrj.090302.
Testo completoAbstract (sommario):
Gully erosion is a severe ecological concern in Auchi and its environs, which has led to destruction of lives and properties. Termite reworked soils have been observed to possess improved engineering properties and have over the years been used to improve soil properties. This research therefore seeks to mitigate the effects of the erosion by stabilizing the gully soils using termite-reworked soils of different genetically diverse origins. Soils from gully walls and beds from two gully erosion sites in the Auchi area and termite-reworked soils from different geological terrains were sampled. All the soils were analyzed for the determination of natural moisture content, grain size analyses, and Atterberg limits. The gully soil samples were thereafter compacted with termite-reworked soils at optimum blending ratio ranging between 27 to 50% by weight gotten through an arithmetic method by adopting grading limits for soil-aggregate mixtures. Shear strength parameters were determined on the compacted soils at OMC. The results revealed that the gully soil is non-plastic unconsolidated poorly graded sand with uniformity coefficient between (1.70-2.50), coefficient of curvature (0.77-1.15), natural moisture content between (4.00-9.00), while the termite reworked soils of both terrains are fairly graded inorganic soil of low to medium plasticity composed of kaolinite as the dominant clay mineral, indicating non-swelling and shrinkage potentials. Both termite-reworked soils are classified as lean clay soils, indicative of their suitable binding properties. The gully soils possess low maximum dry density showing the soils are unconsolidated and friable while the effect of the stabilization increases the MDD and reduces the OMC. Pre-stabilized gully soils have an average cohesion value of 15.5 KN/m2 indicating a very loose soil while the SBT (Sedimentary base termitarium) stabilized gully soil and the BCT (Basement complex termitarium) stabilized gully soil have an average cohesion value of 51.3 KN/m2 and 57.3 KN/m2 indicating the presence of binding material. Conclusively, blending of gully soil with termite-reworked soils significantly enhanced the cohesion between the grain particles of the gully soils, improved its strength and can thus help prevent gully.
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Flemming, Hans-Curt. "Sorption sites in biofilms". Water Science and Technology 32, n. 8 (1 ottobre 1995): 27–33. http://dx.doi.org/10.2166/wst.1995.0256.
Testo completoAbstract (sommario):
The distribution of pollutants in water is strongly dependent on the processes at the solid-liquid interface, such as soprtion. The solid phase is represented by many different materials, mostly minerals but also metals and organics. In technical and natural water systems, biofilms occur to a greater or lesser extent. They will cover the underlying material (substratum) at least partially and represent a gel-type layer, mainly consisting of extracellular polymeric substances (EPS), formed by biofilm organisms, in which the latter are embedded. Thus, the sorption properties of biofilms will significantly determine the overall process. This effect may have been almost completely overseen, e.g., in the assessment of the fate of pollutants in waters, in the process of sediment diagenesis, and in chemical sorption studies. Sorption data can differ considerably between sterile and non-sterile assays; this aspect puts in question many results gained in biologically uncharacterized systems. Sorption in biofilms can be undesired, if pollutants accumulate in biomass such as activated sludge. The same effect, however, can be biotechnologically exploited, e.g. in biosorption reactors. Biofilms can sorb water, inorganic and organic solutes and particles. As sorption sites can serve: EPS, cell walls, cell membranes and cell cytoplasm. These sites display different sorption preferences, capacities and properties. The situation becomes even more complex as biofilms may respond physiologically to sorbed substances. For example: the uptake of toluene can lead to the formation of uronic acids in the EPS and, thus, to an increased sorption capacity for cations. When decomposing, biofilms will release sorbed substances. This can be of significance if trickling deposition of sewage water on soil is finished. The biomass will decompose, sorbed pollutants are remobilized and can contaminate the ground water if not retained abiotically by other soil components. A substantial research demand is identified regarding the following questions: (i) what do biofilms sorb; (ii) what are the binding sites; (iii) what are the sorption mechanisms and capacity, and (iv) what is the remobilization potential?
23
Schrumpf, M., K. Kaiser, G. Guggenberger, T. Persson, I. Kögel-Knabner e E. D. Schulze. "Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals". Biogeosciences Discussions 9, n. 9 (21 settembre 2012): 13085–133. http://dx.doi.org/10.5194/bgd-9-13085-2012.
Testo completoAbstract (sommario):
Abstract. Conceptual models suggest that stability and age of organic carbon (OC) in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Various tools like density fractionation, mineralization experiments, and radiocarbon analyses have been used to study the importance of these mechanisms. We systematically apply them to a range of European soils to test whether general controls emerge even for soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled in 10 cm depth intervals to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF) were analysed for OC, total nitrogen (TN), δ13C, and Δ14C. Bulk samples were also incubated to determine mineralizable OC. Declining OC-normalized CO2 release and increasing age with soil depth confirm greater stability of OC in subsoils across sites. Depth profiles of LF-OC matched those of roots, which in turn reflect plant functional types in soil profiles not subject to ploughing. Modern Δ14C signatures and positive correlation between mineralizable C and fLF-OC indicate the fLF is an easily available energy and nutrient source for subsurface microbes. Fossil C derived from the geogenic parent material affected the age of OC especially in the LF at three study sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining OC-normalized CO2 release rates with increasing contributions of HF-OC to bulk soil OC and the low Δ14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. The decrease in Δ14C (increase in age) of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. While quantitatively less important than OC in the HF, consistent older ages of oLF-OC than fLF-OC indicate that occlusion of LF-OC in aggregates also contributes to OC stability in subsoils. Overall, our results showed that association with minerals is the most important factor in stabilization of OC in soils.
24
Sun, C. Y., J. S. Liu, Y. Wang, N. Zheng, X. Q. Wu e Q. Liu. "Effect of long-term cultivation on soil organic carbon fractions and metal distribution in humic and fulvic acid in black soil, Northeast China". Soil Research 50, n. 7 (2012): 562. http://dx.doi.org/10.1071/sr12100.
Testo completoAbstract (sommario):
Cultivation affects soil organic matter and its fractions. Fulvic acid (FA) and humic acid (HA) make up an important part of soil organic matter, and their binding capacity influences heavy metal behaviour in soil. This research studied changes in soil organic components and the distribution of copper (Cu), lead (Pb), and zinc (Zn) in HA and FA affected by long-term cultivation in black soils. Uncultivated sites and their adjacent cultivated sites (18, 50, and >200 years) were selected. Alkaline sodium hydroxide/pyrophosphate extraction of humic substances and precipitation of HA by acidification were used to separate the HA and FA fractions. Concentrations of Cu, Pb, and Zn in HA and FA were determined. The content of soil organic carbon (C) had decreased by 30% after 200 years of cultivation. Cultivation led to a moderate decrease (38%) in HA and a minor decrease (7%) in FA. The CHA/CFA ratio, which is a humification parameter, decreased from 2.05 in the uncultivated soil to 1.38 in the soil cultivated for 200 years, indicating a lower degree of humification of organic matter in cultivated soils. Of the Na4P2O7 + NaOH-extracted Pb and Zn, 47–60% and 63–76%, respectively, was associated with FA, showing that FA has a high affinity for Pb and Zn. Of the Na4P2O7 + NaOH-extracted Cu, 55% was in the HA fraction. The share of Cu and Zn in the HA fraction decreased with cultivation time, but cultivation did not bring about a systematic change in Pb distribution in humic substances. The results show that cultivation can decrease the humified C content and metals bound to the HA fraction, and suggest that cultivation may potentially increase the mobility of heavy metals.
25
Sani, A., U. K. Adamu, B. S. Hayatu, I. A. Adam, R. W. Aliyu, M. D. Garba, J. Aliyu, H. Almu, e N. A. Abdulkadir. "Treated wastewater irrigation effects on aggregate stability of Sandy loam soils in Semi-arid Tropical Zone of Nigeria". Global Journal of Agricultural Research 10, n. 4 (15 aprile 2022): 1–15. http://dx.doi.org/10.37745/gjar.2013/vol10n4115.
Testo completoAbstract (sommario):
Irrigation with treated wastewater (TWW) for agricultural production is gradually becoming very important recycling option that substitutes fresh water (FW) particularly in water stressed regions like the Semi-arid Tropical zone of Nigeria. However, owing to high salt concentrations, dissolved organic matter and organic compounds found in the TWW occasionally, its application can have potential adversative impacts such as reduction of soil aggregate stability (SAS), which in turn affects soil quality. To assess the impact of TWW irrigation in comparison to FW irrigation on soils aggregation and SAS, wet sieving technique and the relationship of coefficient of variation (KV) and Mean Weight Diameter (MWD) were applied, while normal standard procedure was used for determination of some selected soil chemical and physical characteristics. The results indicated that the application of TWW increased the soil aggregate stability, and significantly highest (P<0.05) in phase III soils compared to other phases and control treated soils possibly due to relatively high organic matter content in the TWW sites compared to FW sites. Furthermore, the TWW is characterized by low concentration of salinity and sodicity parameters such as EC and Na, and comparatively high microbial glue like adhesive substances from the OC of the TWW soils. This in turn improve the aggregation, structural stability of the topsoil on one hand, and reduce the soils vulnerability to erosion on the other hand by binding micro-aggregates together to form macro-aggregates and larger pore spaces between micro-aggregates. Consequently, leading to improved water infiltration and permeability. Overall, the results indicated that the use of TWW for irrigation is a viable option, but care should be taken on the type and composition of the TWW particularly with regards to soluble salts concentration, organic and inorganic substances, as they can influence soils aggregate stability with other soil physical and chemical properties. This will consequently affect general soil quality and crop yield.
26
Ahmed, Waqas, Huang Jing, Liu Kailou, Sehrish Ali, Han Tianfu, Sun Geng, Chen Jin et al. "Impacts of long-term inorganic and organic fertilization on phosphorus adsorption and desorption characteristics in red paddies in southern China". PLOS ONE 16, n. 1 (29 gennaio 2021): e0246428. http://dx.doi.org/10.1371/journal.pone.0246428.
Testo completoAbstract (sommario):
Soil phosphorus (P) adsorption and desorption occur in an important endogenous cycle linked with soil fertility problems and relevant to the environmental risk assessment of P. In our study, the effect of long-term inorganic and organic fertilization on P adsorption and desorption characteristics in relation to changes in soil properties was evaluated by selecting three long-term experimental sites in southern China. The selected treatments at each site were CK (unfertilized), NPK (synthetic nitrogen, phosphorus and potassium) and NPKM (synthetic NPK plus manure). The adsorption and desorption characteristics of P were evaluated using Langmuir and Freundlich isotherms. The results showed that long-term application of NPK plus manure significantly increased soil organic carbon (SOC), total P and available P at all three sites compared with the NPK and CK treatments. All three treatments fit these equations well. The maximum adsorption capacity (Qm) of P increased with NPKM treatment, and the binding energy of P (K) and the maximum buffering capacity (MBC) showed increasing trends. NPKM showed the highest Qm (2346.13 mg kg-1) at the Jinxian site, followed by Nanchang (221.16 mg kg-1) and Ningxiang (2219.36 mg kg-1). Compared to CK and NPK, the NPKM treatment showed a higher MBC as 66.64, 46.93 and 44.39 L kg-1 at all three sites. The maximum desorption capacity (Dm) of P in soil was highest with the NPKM treatment (157.58, 166.76, 143.13 mg kg-1), showing a better ability to release P in soil. The correlation matrix showed a significant positive correlation of SOC, total and available P with Qm, Dm and MBC. In conclusion, it is suggested that manure addition is crucial to improve P utilization in red paddy soils within the recommended range to avoid the risk of environmental pollution.
27
Meychik, Nataly, Yuliya Nikolaeva, Maria Kushunina e Igor Yermakov. "Are the carboxyl groups of pectin polymers the only metal-binding sites in plant cell walls?" Plant and Soil 381, n. 1-2 (16 aprile 2014): 25–34. http://dx.doi.org/10.1007/s11104-014-2111-z.
Testo completo
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Da Silva, Joaquim C. G. Esteves, e Adélio A. S. C. Machado. "Interaction of Fulvic Acids with Al(III) Studied by Self-Modeling Curve Resolution of Second-Derivative Synchronous Fluorescence Spectra". Applied Spectroscopy 50, n. 4 (aprile 1996): 436–43. http://dx.doi.org/10.1366/0003702963906050.
Testo completoAbstract (sommario):
The interaction of Al(III) with two samples of fulvic acids (fua), extracted from materials present in a pinewood soil (fua2 from the upper soil horizon, or leaf litter, and fua3 from lower soil horizons), was followed by synchronous fluorescence (SyF) spectroscopy at pH 4. The variations observed in the inverted second-derivative spectral data were analyzed by SIMPLISMA, a self-modeling curve resolution technique. Three binding sites were detected for each fua sample, and their spectra and SyF intensity profiles were obtained. Conditional stability constants for coordination of one binding site of each fua and Al(III) were obtained (log values): fua2, 5.65(15); fua3, 4.64(2). The experimental and data analysis methodologies were validated by analysis of data obtained for salicylic acid under the same conditions. The log value found for its conditional stability constant for Al(III) coordination at pH 4 was 4.34(15).
29
Ghabbour, E. A., G. Davies, R. L. Dunfee, N. A. Smith e M. E. Vozzell. "Adsorption of nucleic acid constituent uracil on copper(II)-loaded, solid peat and soil-derived humic acids". Canadian Journal of Soil Science 81, n. 3 (1 agosto 2001): 309–16. http://dx.doi.org/10.4141/s00-066.
Testo completoAbstract (sommario):
Humic acids (HA) in compost, peats and soils sorb organic compounds selectively. This paper investigates the micro- and macroscopic properties of solid HAs isolated from a German peat (GHA) and a New Hampshire soil (NHA) using tightly bound copper(II) and nucleic acid constituent uracil adsorption as analytical probes. Isotherm measurements at 5.0–35.0°C show that tightly bound Cu(II) decreases the amount of uracil adsorbed by GHA at mM or lower uracil concentrations whereas previous work revealed the opposite effect for bound Hg(II). Site capacity comparisons are consistent with lower coordination numbers for HA-bound Hg(II) than for HA-bound Cu(II). Low coordination numbers leave Hg(II) sites open for uracil binding. Enthalpy and entropy changes for uracil adsorption on GHA, NHA, their Cu(II) and Hg(II)-loaded forms and on compost-derived HA are linearly correlated, indicating that HAs are free energy buffers. Water and bound metals evidently play major roles in HA-solute interactions and in HA aggregation/disaggregation. Key words: Humic acids, metal binding, nucleic acid constituents, uracil, adsorption, isotherms, thermodynamics
30
Beauchemin, Suzanne, e R. R. Simard. "Soil phosphorus saturation degree: Review of some indices and their suitability for P management in Québec, Canada". Canadian Journal of Soil Science 79, n. 4 (1 novembre 1999): 615–25. http://dx.doi.org/10.4141/s98-087.
Testo completoAbstract (sommario):
Many agricultural fields contain excessive labile soil P in regard to crop needs. Its environmental fate must be assessed. The concept of P saturation degree is meaningful as it describes the portion of the soil binding sites already covered with P, and indicates the potential desorbability of soil P. The first objective of this study was to review different indices that have been proposed to estimate the degree of soil P saturation and the relationships between soil P saturation degree and P solubility. The second objective is to discuss their suitability as environmental indicators for P management in the province of Québec, Canada. In the Netherlands, the P saturation index is defined as the ratio of P to Al + Fe contents extracted by ammonium oxalate [Pox/( Alox + Feox ) or ( Pox/0.5( Alox + Feox )]. This approach has been mainly used with non-calcareous soils. In Québec, the ratio of Mehlich-III extractable P to Al (M3P/AlM3) is proposed as an alternative, which relies on routine laboratory test. However, the suitability of the M3P/AlM3 ratio has yet to be determined for some specific soil groups (e.g. gleyed soils, soils with Alox content >6 g kg−1) and for subsoil horizons. Regardless of the chosen index, it is suggested that the best way to manage the risk of water contamination by P in Québec (namely, defining critical levels of soil P saturation) may be to form homogeneous soil groups to account for their distinctive behaviour and characteristics. Key words: Phosphorus, saturation, management
31
Schilling, M., e W. T. Cooper. "Identification of Copper Binding Sites in Soil Organic Matter through Chemical Modifications and13C CP-MAS NMR Spectroscopy". Environmental Science & Technology 38, n. 19 (ottobre 2004): 5059–63. http://dx.doi.org/10.1021/es049653w.
Testo completo
32
Fischer, P., R. Pöthig, B. Gücker e M. Venohr. "Estimation of the degree of soil P saturation from Brazilian Mehlich-1 P data and field investigations on P losses from agricultural sites in Minas Gerais". Water Science and Technology 74, n. 3 (31 maggio 2016): 691–97. http://dx.doi.org/10.2166/wst.2016.169.
Testo completoAbstract (sommario):
The degree of phosphorus saturation (DPS) of agricultural soils is studied worldwide for risk assessment of phosphorus (P) losses. In previous studies, DPS could be reliably estimated from water-soluble P (WSP) for European and Brazilian soils. In the present study, we correlated measured WSP and Mehlich-1 P (M1P) from soils of Minas Gerais (MG) and Pernambuco (PE) (R2 = 0.94, n = 59) to create a DPS map from monitoring data. The resulting DPS map showed high spatial variability and low values of DPS (54 ± 22%, mean and standard deviation; n = 1,827). Measured soil DPS values amounted to 63 ± 14% and resulted in relatively low dissolved P concentrations measured in a surface runoff study in MG. However, fertilizer grains on the soil surface led to high WSP values (>30 mg/kg) indicating high risks of dissolved P losses. We suppose that small Oxisol particles with Fe and Al hydroxides sorbed most of the dissolved fertilizer P in runoff so that P was mainly exported in particulate form. In soils with lower contents of P sorption and binding partners, e.g. Entisols in PE, this effect may be less dominant. Consequently, superficial fertilizer effects have to be considered in addition to DPS in risk assessment of P losses from agricultural areas in Brazil.
33
Li, Jian, Andrew W. Rate e Robert J. Gilkes. "Silver ion desorption kinetics from iron oxides and soil organic matter: effect of adsorption period". Soil Research 42, n. 1 (2004): 59. http://dx.doi.org/10.1071/sr03056.
Testo completoAbstract (sommario):
In order to have a better understanding of the mobility and bioavailability of silver in the environment, it is important to investigate the desorption behaviour of silver from some environmentally relevant soil components. Four single soil constituents (charcoal, humic acid, ferrihydrite, goethite) were chosen to investigate the rate of desorption of silver ions. The effect of reaction period between silver and the soil constituents on subsequent desorption was also investigated. A significant proportion of Ag+ sorbed by Fe oxides, humic acid, and charcoal cannot readily be desorbed back into solution. For goethite and humic acid, a longer contact period between Ag+ and the adsorbing phase caused subsequent slower rates of desorption, and a smaller proportion of adsorbed Ag+ was desorbed back into solution. Two-site and log-normal equations, assuming the desorption reaction was first-order, gave excellent fits to experimental data, except for Ag+ desorption from charcoal, in which case the kinetic experimental data fitted to a 1-site model better. The parameters obtained from the modelling provide information regarding the possible changes in metal–oxide binding and metal–humic acid complexing mechanisms, and these changes can be interpreted as a re-arrangement of Ag ions to sites with slower desorption reaction rates. All the reaction sites on charcoal have very similar desorption rates (rate constants), and these sites are relatively slow to desorb Ag. Fe oxides, and humic acid and charcoal could be very important sinks for Ag. The longer the Ag interacts with soils in environment, the less mobile Ag becomes, and the less toxic and bioavailable it will be to living organisms.
34
Henderson, Keri L. D., Jason B. Belden, Shaohan Zhao e Joel R. Coats. "Phytoremediation of Pesticide Wastes in Soil". Zeitschrift für Naturforschung C 61, n. 3-4 (1 aprile 2006): 213–21. http://dx.doi.org/10.1515/znc-2006-3-410.
Testo completoAbstract (sommario):
Soils at agrochemical dealer sites often are contaminated with pesticide residues from decades of accidental and incidental spillage. We have determined that prairie grasses native to the Midwestern U.S. are suitable for phytoremediation because they are tolerant of most herbicides and of climatic extremes, such as heat, cold, drought, and flooding. A mixed stand of big bluestem, switch grass, and yellow indiangrass develops a rhizosphere with microflora that can readily detoxify pesticide residues. Specific atrazine-degrading bacteria or the free enzyme atrazine chlorohydrolase also can enhance the rate of biotransformation of atrazine in soil. Metolachlor degradation can be accelerated significantly by the prairie grass/rhizosphere effect. Several grasses used in filter strips have also been evaluated for their pesticidedegradation capabilities. The prairie grasses also have been demonstrated to reduce the rates of leaching of pesticides through intact soil columns, since less water leaches out of vegetated soil columns compared to non-vegetated soil columns. The evaluation of the degree of success of remediation has relied heavily on chemical residue analysis, but recent studies on biological endpoints have shown promise for providing more ecologically relevant indications of the potential exposure of organisms to pesticides in the soil. Earthworm 8-day bioaccumulation assays and root growth assays have shown the value of assessing the bioavailability of the residues. Mass balance experiments have utilized radiolabeled atrazine and metolachlor to ascertain the complete metabolism and binding profile of those two pesticides in phytoremediation studies.
35
Vlădoiu, Diana Larisa, Marioara Nicoleta Filimon, Vasile Ostafe e Adriana Isvoran. "Effects Of Herbicides And Fungicides On The Soil Chitinolytic Activity. A Molecular Docking Approach". Ecological Chemistry and Engineering S 22, n. 3 (1 settembre 2015): 439–50. http://dx.doi.org/10.1515/eces-2015-0025.
Testo completoAbstract (sommario):
Abstract A molecular docking study was undertaken using the programs SwissDock and PatchDock to assess the interactions of the bacterial chitinases belonging to the GH18 and GH19 families with two herbicides (chlorsulfuron and nicosulfuron) and two fungicides (difenoconazole and drazoxolon). Both molecular docking programs predict that all considered pesticides bind to the active sites of chitinases produced by soil microorganisms. There are correlations for predicted binding energy values for receptor-ligand complexes obtained using the two programs consolidating the prediction of the chitinases-pesticides interactions. The interactions of chitinases with pesticides involve the same residues as their interactions with known inhibitors suggesting the inhibitory potential of pesticides. Pesticides interact stronger with chitinases belonging to the GH18 family, their active sites reflecting higher polarity than those of the GH19 chitinases. Also, herbicides reveal a higher inhibitory potential to bacterial chitinases than fungicides.
36
Esteves da Silva, Joaquim CG, Adélio ASC Machado, Miguel A. Ferreira e Francisco Rey. "Method for the differentiation of leaf litter extracts and study of their interaction with Cu(II) by molecular fluorescence". Canadian Journal of Chemistry 76, n. 8 (1 agosto 1998): 1197–209. http://dx.doi.org/10.1139/v98-150.
Testo completoAbstract (sommario):
Six leaf litter extracts (LLE) (eucalyptus (Eucaliptus globulus), fern (Pteridium aquilinium), oak (Quercus robur), chestnut (Castanea sátiva), laurel (Laurus nobilis), and ulex (Ulex europoeus) canopies) were isolated following an extraction procedure similar to that used for fulvic acids (FA) and were characterized by elemental analysis and UV-Vis, FT-IR, and synchronous molecular fluorescence (SyF) spectroscopies. Moreover, information about their interaction with the Cu(II) ion in aqueous solution (100 mg yL of LLE in 0.1 M KNO3 at pH = 6) was obtained from the measurement of SyF spectra at increasing concentrations of Cu(II). These spectral sets were treated by a self-modeling mixture analysis method (SIMPLISMA) to obtain improved quenching profiles to be used in the estimation by the method of Ryan and Weber of the conditional stability constants (Kc), concentration of binding sites, and percentage of fluorescent binding sites accessible for complexation. For comparison purposes, two samples of FA extracted from two horizons of an oak forest soil (0-5 cm and 5-15 cm) were also studied. The spectroscopic data obtained for LLE and FA were different. The results suggest that LLE are characterized by relatively high concentrations of individualized simple molecules and include reactive structures (alkene and protein residues). The ratio of aliphatic yaromatic structures was higher in LLE than for FA. Both LLE and soil FA form stable complexes with Cu(II), but the logarithm of the conditional stability constant of the 1:1 complexes is larger for LLE (about 5) than for the soil FA (about 4.5).Key words: leaf litter extracts, soil fulvic acids, synchronous fluorescence, Cu(II) complexation, SIMPLISMA, spectral pattern recognition.
37
Baumgarth, Birgit, Frank Wilco Bartels, Dario Anselmetti, Anke Becker e Robert Ros. "Detailed studies of the binding mechanism of the Sinorhizobium meliloti transcriptional activator ExpG to DNA". Microbiology 151, n. 1 (1 gennaio 2005): 259–68. http://dx.doi.org/10.1099/mic.0.27442-0.
Testo completoAbstract (sommario):
The exopolysaccharide galactoglucan promotes the establishment of symbiosis between the nitrogen-fixing Gram-negative soil bacterium Sinorhizobium meliloti 2011 and its host plant alfalfa. The transcriptional regulator ExpG activates expression of galactoglucan biosynthesis genes by direct binding to the expA1, expG/expD1 and expE1 promoter regions. ExpG is a member of the MarR family of regulatory proteins. Analysis of target sequences of an ExpG(His)6 fusion protein in the exp promoter regions resulted in the identification of a binding site composed of a conserved palindromic region and two associated sequence motifs. Association and dissociation kinetics of the specific binding of ExpG(His)6 to this binding site were characterized by standard biochemical methods and by single-molecule spectroscopy based on the atomic force microscope (AFM). Dynamic force spectroscopy indicated a distinct difference in the kinetics between the wild-type binding sequence and two mutated binding sites, leading to a closer understanding of the ExpG–DNA interaction.
38
Rosenberg, Michael G. "Clindamycin". Pediatrics In Review 17, n. 10 (1 ottobre 1996): 373–74. http://dx.doi.org/10.1542/pir.17.10.373.
Testo completoAbstract (sommario):
Clindamycin (CM) is a chemically synthesized derivative of lincomycin, which originally was isolated from the soil actinomycete Streptomyces lincolnesis in 1962. CM essentially has replaced lincomycin therapeutically because of its broader antimicrobial spectrum and enhanced gastrointestinal absorption. CM inhibits bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome, thereby blocking peptide chain initiation and elongation. CM functions as a bacteriostatic agent; however, in certain clinical situations, it can be considered bactericidal. Interestingly, the ribosomal binding sites of macrolide antibiotics (erythromycin, clarithromycin, etc) and chloramphenicol appear to overlap, leading to the theoretic concern of drug antagonism should these medications be used in combination.
39
Chung, Kun H., Seog W. Rhee, Hyun S. Shin e Christopher H. Moon. "Probe of cadmium(II) binding on soil fulvic acid investigated by 113Cd NMR spectroscopy". Canadian Journal of Chemistry 74, n. 7 (1 luglio 1996): 1360–65. http://dx.doi.org/10.1139/v96-152.
Testo completoAbstract (sommario):
Binding of cadmium(II) on soil fulvic acid (FA) was investigated over a range of fulvate-to-cadmium concentration ratios (8 – 59 equiv. mol−1) using 113Cd NMR spectroscopy. The 113Cd chemical shift of cadmium bound on fulvate was observed in a more downfield region (δ −20.4 to −15.6) than that bound on synthetic polymers, poly(acrylic acid) (PAA: δ −36.6 to −38.2), poly(methacrylic acid) (PMAA: δ −34.0 to −25.4), and poly(vinyl benzoic acid) (PVBA: δ −34.7 to −31.2). The calculated values of individual chemical shifts for the species CdL+ and CdL2 (L: carboxylate) formed in Cd(II)–carboxylate systems (e.g., acetate, benzoate) are δ −22 to −24 and δ −39 to −40, respectively. The relative downfield shift of cadmium(II)–fulvate suggests that functional groups (e.g., hydroxyl and neutral N donor) other than carboxylates may be involved in cadmium coordination. The chemical shifts of cadmium complexes of hydroxycarboxylates (e.g., glycolate) or carboxylates containing neutral N donor (e.g., picolinate) were generally observed in more downfield regions than their carboxylate counterparts. Key words: fulvic acid, polyfunctionality, binding sites, chemical shift, 113Cd NMR.
40
Tabassum, Noshabah, Uzaira Rafique, Khaled S. Balkhair e Muhammad Aqeel Ashraf. "Chemodynamics of Methyl Parathion and Ethyl Parathion: Adsorption Models for Sustainable Agriculture". BioMed Research International 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/831989.
Testo completoAbstract (sommario):
The toxicity of organophosphate insecticides for nontarget organism has been the subject of extensive research for sustainable agriculture. Pakistan has banned the use of methyl/ethyl parathions, but they are still illegally used. The present study is an attempt to estimate the residual concentration and to suggest remedial solution of adsorption by different types of soils collected and characterized for physicochemical parameters. Sorption of pesticides in soil or other porous media is an important process regulating pesticide transport and degradation. The percentage removal of methyl parathion and ethyl parathion was determined through UV-Visible spectrophotometer at 276 nm and 277 nm, respectively. The results indicate that agricultural soil as compared to barren soil is more efficient adsorbent for both insecticides, at optimum batch condition of pH 7. The equilibrium between adsorbate and adsorbent was attained in 12 hours. Methyl parathion is removed more efficiently (by seven orders of magnitude) than ethyl parathion. It may be attributed to more available binding sites and less steric hindrance of methyl parathion. Adsorption kinetics indicates that a good correlation exists between distribution coefficient (Kd) and soil organic carbon. A general increase in Kd is noted with increase in induced concentration due to the formation of bound or aged residue.
41
Xia, Kang, William Bleam e Philip A. Helmke. "Studies of the nature of Cu2+ and Pb2+ binding sites in soil humic substances using X-ray absorption spectroscopy". Geochimica et Cosmochimica Acta 61, n. 11 (giugno 1997): 2211–21. http://dx.doi.org/10.1016/s0016-7037(97)00079-3.
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Mittal, Sheenu, e Lee Kroos. "Combinatorial Regulation by a Novel Arrangement of FruA and MrpC2 Transcription Factors during Myxococcus xanthus Development". Journal of Bacteriology 191, n. 8 (6 febbraio 2009): 2753–63. http://dx.doi.org/10.1128/jb.01818-08.
Testo completoAbstract (sommario):
ABSTRACT Myxococcus xanthus is a gram-negative soil bacterium that undergoes multicellular development upon nutrient limitation. Intercellular signals control cell movements and regulate gene expression during the developmental process. C-signal is a short-range signal essential for aggregation and sporulation. C-signaling regulates the fmgA gene by a novel mechanism involving cooperative binding of the response regulator FruA and the transcription factor/antitoxin MrpC2. Here, we demonstrate that regulation of the C-signal-dependent fmgBC operon is under similar combinatorial control by FruA and MrpC2, but the arrangement of binding sites is different than in the fmgA promoter region. MrpC2 was shown to bind to a crucial cis-regulatory sequence in the fmgBC promoter region. FruA was required for MrpC and/or MrpC2 to associate with the fmgBC promoter region in vivo, and expression of an fmgB-lacZ fusion was abolished in a fruA mutant. Recombinant FruA was shown to bind to an essential regulatory sequence located slightly downstream of the MrpC2-binding site in the fmgBC promoter region. Full-length FruA, but not its C-terminal DNA-binding domain, enhanced the formation of complexes with fmgBC promoter region DNA, when combined with MrpC2. This effect was nearly abolished with fmgBC DNA fragments having a mutation in either the MrpC2- or FruA-binding site, indicating that binding of both proteins to DNA is important for enhancement of complex formation. These results are similar to those observed for fmgA, where FruA and MrpC2 bind cooperatively upstream of the promoter, except that in the fmgA promoter region the FruA-binding site is located slightly upstream of the MrpC2-binding site. Cooperative binding of FruA and MrpC2 appears to be a conserved mechanism of gene regulation that allows a flexible arrangement of binding sites and coordinates multiple signaling pathways.
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Feria-Cáceres, Pedro F., Lucas Penagos-Velez e Claudia X. Moreno-Herrera. "Tolerance and Cadmium (Cd) Immobilization by Native Bacteria Isolated in Cocoa Soils with Increased Metal Content". Microbiology Research 13, n. 3 (14 agosto 2022): 556–73. http://dx.doi.org/10.3390/microbiolres13030039.
Testo completoAbstract (sommario):
Twelve cadmium native bacteria previously isolated in soils of cocoa farms located in the western Colombian Andes (Santander), and tolerant to 2500 µM CdCl2 (120 mg Cd/L), were chosen in order to test their tolerance and Cd immobilization using liquid culture medium (Nutritive broth) at different concentrations of heavy metals. Furthermore, in the greenhouse experiments, the strains Exiguobacterium sp. (11-4A), Klebsiella variicola sp. (18-4B), and Enterobacter sp. (29-4B) were applied in combined treatments using CCN51 cacao genotype seeds grown in soil with different concentrations of Cd. All bacterial strains’ cell morphologies were deformed in TEM pictures, which also identified six strain interactions with biosorption and four strain capacities for bioaccumulation; FT-IR suggested that the amide, carbonyl, hydroxyl, ethyl, and phosphate groups on the bacteria biomass were the main Cd binding sites. In the pot experiments, the concentration of Cd was distributed throughout the cacao plant, but certain degrees of immobilization of Cd can occur in soil to prevent an increase in this level in roots with the presence of Klebsiella sp.
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Johan, Prisca Divra, Osumanu Haruna Ahmed, Nur Aainaa Hasbullah, Latifah Omar, Puvan Paramisparam, Nur Hidayah Hamidi, Mohamadu Boyie Jalloh e Adiza Alhassan Musah. "Phosphorus Sorption following the Application of Charcoal and Sago (Metroxylon sagu) Bark Ash to Acid Soils". Agronomy 12, n. 12 (29 novembre 2022): 3020. http://dx.doi.org/10.3390/agronomy12123020.
Testo completoAbstract (sommario):
Acidic cations such as Al, Fe, and Mn tend to fix P in soils, and this reaction make P unavailable for plant uptake. Several conventional strategies for farmers had been proposed to ameliorate Al toxicity either via liming or continuous P fertilization. However, these approaches are not only expensive but are also environmental unfriendly. Thus, a sorption study was carried out using charcoal and sago bark ash as soil amendments to determine their effects on P sorption characteristics of low pH soils. Phosphorus sorption determination was based on standard procedures and the P adsorption data for the samples tested in this study were fitted to the Langmuir equation. The results suggest that the combined use of charcoal and sago bark ash decreased P adsorption and increased P desorption relative to the untreated soils. Organic matter in the charcoal reduced P sorption by providing more negatively charged surfaces, thus increasing anion repulsion. Apart from increasing the amount of P adsorbed in the soil, the use of the sago bark ash increased the amount of P desorbed because the primary reaction between the sago bark ash and soils is an acid neutralization reaction. These improvements do not only reduce P fixation in acid soils but they also promote the effective utilization of nutrients via the timely release of nutrients for maximum crop production. In conclusion, the incorporation of charcoal and sago bark ash to the soil had a positive effect on replenishing the soil solution’s P. The organic matter of the charcoal reduces P sorption capacity by blocking P binding sites, increasing the negative electric potential in the plane of adsorption, causing steric hindrance on the mineral surfaces and decreasing goethite and hematite-specific surface areas. However, there is a need for the inclusion of more soil chemical, physical, and mineralogical properties in predicting soil P sorption to enhance the reliability of the findings.
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Ruan, Rujue, Zhifang Jiang, Yuhuan Wu, Maojun Xu e Jun Ni. "High-throughput sequence analysis reveals variation in the relative abundance of components of the bacterial and fungal microbiota in the rhizosphere of Ginkgo biloba". PeerJ 7 (15 novembre 2019): e8051. http://dx.doi.org/10.7717/peerj.8051.
Testo completoAbstract (sommario):
Background The narrow region of soil, in contact with and directly influenced by plant roots, is called the rhizosphere. Microbes living in the rhizosphere are considered to be important factors for the normal growth and development of plants. In this research, the structural and functional diversities of microbiota between the Ginkgo biloba root rhizosphere and the corresponding bulk soil were investigated. Methods Three independent replicate sites were selected, and triplicate soil samples were collected from the rhizosphere and the bulk soil at each sampling site. The communities of bacteria and fungi were investigated using high-throughput sequencing of the 16S rRNA gene and the internal transcribed spacer (ITS) of the rRNA gene, respectively. Results A number of bacterial genera showed significantly different abundance in the rhizosphere compared to the bulk soil, including Bradyrhizobium, Rhizobium, Sphingomonas, Streptomyces and Nitrospira. Functional enrichment analysis of bacterial microbiota revealed consistently increased abundance of ATP-binding cassette (ABC) transporters and decreased abundance of two-component systems in the rhizosphere community, compared to the bulk soil community. In contrast, the situation was more complex and inconsistent for fungi, indicating the independency of the rhizosphere fungal community on the local microenvironment.
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Rigane, E., R. Dutoit, S. Matthijs, N. Brandt, S. Flahaut e K. S. Belghith. "Characterization of Putative Virulence Factors of Pseudomonas aeruginosa Strain RBS Isolated from a Saltern, Tunisia: Effect of Metal Ion Cofactors on the Structure and the Activity of LasB". BioMed Research International 2020 (23 luglio 2020): 1–13. http://dx.doi.org/10.1155/2020/6047528.
Testo completoAbstract (sommario):
Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium able to survive in diverse environments such as soil, plants, freshwater, and seawater. P. aeruginosa can be an opportunistic pathogen to humans when their immune system is deficient. Its pathogenicity may be linked to the production of virulence factors. We isolated P. aeruginosa strain RBS from the saltern of Sfax in Tunisia. In this study, we characterized the halotolerance, antibiotic susceptibility, and some virulence factors of strain RBS. High NaCl concentrations inhibited growth and motility. However, biofilm formation was enhanced to protect bacteria against salt stress. Among the 18 antibiotics tested, quinolones and tetracycline showed a significant inhibitory effect on growth, motility, and biofilm formation of strain RBS. β-Lactams, however, did not have any inhibitory effect on neither bacterial growth nor motility. In some cases, resistance was due, in part, to biofilm formation. We also showed that RBS produces two proteases, LasB and AprA, which have been shown to be implicated in host infection. LasB was further characterized to study the role of metal ions in enzyme stability. It possesses two distinct metal ion-binding sites coordinating a calcium and a zinc ion. The effect of metal ion chelation was evaluated as well as substitutions of residues involved in metal ion binding. Impairing metal ion binding of LasB led to a loss of activity and a sharp decrease of stability. Our findings suggest that the binding of both metal ions is interdependent as the two metal ions’ binding sites are linked via a hydrogen bond network.
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Jeong, Buyun, Jinsung An e Kyoungphile Nam. "Time series analysis for determining ecologically acceptable Cu concentration from species sensitivity distribution with biotic ligand models in soil pore water". Environmental Engineering Research 26, n. 2 (3 aprile 2020): 200021–0. http://dx.doi.org/10.4491/eer.2020.021.
Testo completoAbstract (sommario):
A site-specific, ecologically acceptable concentration of Cu in soil pore water was determined with four trophic levels of soil-residing organisms. Specifically, soil pore water was periodically collected from a site contaminated with heavy metals using in-situ samplers. Dissolved Cu concentration, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, NO3-, dissolved organic carbon, pH, and temperature were analyzed to derive a half-maximal effective concentration of Cu (EC50[Cu]T) using a biotic ligand model (BLM). The BLM parameters, such as binding constants (logKXBL) and the fraction of biotic ligand sites occupied by Cu ions (f), were adapted from previous studies. The EC50{Cu2+,} values were used to construct a species sensitivity distribution (SSD) curve from which the hazardous concentration, protecting 95% of the soil-residing organisms (HC5), was determined. Using ten BLM-based acceptable concentrations of Cu obtained by combining BLM and SSD, time series analysis was conducted with the fixed monitoring benchmark method to obtain maximum Cu concentration as an endpoint exhibiting no-adverse-effect which was found to be 0.084 mg/L of Cu in soil pore water at the test site. This study provides a systematic tool for determining an ecologically acceptable concentration of Cu in the soil by incorporating soil pore water chemistry and time series analysis.
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Pelfrene, Aurélie, e Nathalie Gassama. "Competition between particles and dissolved organic matter for trace metal binding in unpolluted soil solutions: Monitoring and thermodynamic approaches". Bulletin de la Société Géologique de France 183, n. 3 (1 maggio 2012): 189–201. http://dx.doi.org/10.2113/gssgfbull.183.3.189.
Testo completoAbstract (sommario):
Abstract In this study, monitoring and thermodynamic approaches were combined in order to identify the dominant features, which control the speciation of Cd, Cu, Pb, and Zn in solutions from unpolluted planosolic soil (North Massif Central, France). Three sites were selected according to topography and monitored from January to May 2006 using piezometers. The sandy-loam to clay-loam organic-rich horizon (horizon A) and the gravely and concretion-rich horizon (horizon E) were chosen to assess the potential impact of type of horizon on the chemical speciation of metals in the soil solutions. Binding of metals to organic ligands was studied by differential pulse anodic stripping voltammetry (DPASV) in order to acquire experimental data which could be used for the validation of speciation models. These data, together with data from the literature on properties of natural particulate matter, were used to determine the speciation of Cd, Cu, Pb and Zn with a thermodynamic code (PHREEQC). The observed and predicted speciation were compared to estimate the contributions of natural dissolved organic matter and of particles to the binding of metal ions. There was a good match between observed and predicted results, validating the approach used. Results show that particles (mixed iron and aluminium oxides ± clays ± organic matter) play the main role in the speciation of the trace metals in soil waters rather than complexation with dissolved organic matter. Moreover, particles govern speciation to a greater extent in horizon E than in horizon A, which can be linked to hydrodynamics (reaction time between water and soil due to porosity) and chemical reactivity of the solution circulating.
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Hur, Jin, e Bo-Mi Lee. "Comparing the Heterogeneity of Copper-Binding Characteristics for Two Different-Sized Soil Humic Acid Fractions Using Fluorescence Quenching Combined with 2D-COS". Scientific World JOURNAL 11 (2011): 1865–76. http://dx.doi.org/10.1100/2011/640598.
Testo completoAbstract (sommario):
Heterogeneous distributions of copper-binding characteristics were compared for two ultrafiltered size fractions of a soil HA using fluorescence quenching combined with two-dimensional correlation spectroscopy (2D-COS). The apparent shapes of the original synchronous fluorescence spectra and the extent of the fluorescence quenching upon the addition of copper were similar for the two fractions. The stability constants calculated at their highest peaks were not significantly different. However, the 2D-COS results revealed that the fluorescence quenching behaviors were strongly affected by the associated wavelengths and the fraction's size. The spectral change preferentially occurred in the wavelength order of 467 nm → 451 nm → 357 nm for the 1–10 K fraction and of 376 nm → 464 nm for the >100 K fraction. The extent of the binding affinities exactly followed the sequential orders interpreted from the 2D-COS, and they exhibited the distinctive ranges of the logarithmic values from 5.86 to 4.91 and from 6.48 to 5.95 for the 1–10 K and the >100 K fractions, respectively. Our studies demonstrated that fluorescence quenching combined with 2D-COS could be successfully utilized to give insight into the chemical heterogeneity associated with metal-binding sites within the relatively homogeneous HA size fractions.
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Lisevich, Irina, Dmitrii Lukianov, Daniel Wilson, Petr Sergiev, Olga Dontsova e Ilya Osterman. "Abstract OR-4: New Antibiotic Binding Site on the 30S Ribosomal Subunit". International Journal of Biomedicine 11, Suppl_1 (1 giugno 2021): S8—S9. http://dx.doi.org/10.21103/ijbm.11.suppl_1.or4.
Testo completoAbstract (sommario):
Background: Antibiotic resistance becomes one of the main problems of modern medicine; therefore, the development of new antibacterial compounds is absolutely necessary. The ribosome is the target for a lot of different antibiotics; there are several main binding sites on the ribosome – decoding center, peptidyl-transferase center, and ribosome exit tunnel. Modification or mutation of nucleotides in these sites could make cells resistant to structurally different antibiotics. Methods: pDualrep2 reporter system was used for detection of the protein synthesis inhibitors in cultural broths of new soil bacteria. By means of a cell-free translation system, the inhibitory activity and mechanism of action of Auraplanin were estimated. CryoEM data collection was performed on a Titan Krios operated at 300 kV, equipped with a Falcon II direct electron detector. Results: In this work, we have found a new inhibitor of protein synthesis, which binds in a completely new binding site. This compound is produced by Actinoplanes sp. VKM Ac-2862 and by Cryo-EM study of its complex with E.coli ribosome, it was shown, that it binds close to 560 loop of 30S ribosomal subunit. The new compound is a derivative of tetramic acid and we called it Auraplanin, because of bright orange color of the producer strain. Structural data are in good agreement with genetic results – resistant mutations were located close determined binding site. Substitutions C564G, G558U, and G566A significantly increase minimal inhibitory concentration, all these mutations were not detected previously. We also observed resistant mutation in ribosomal protein S4, this mutation was previously identified as error-prone. Interestingly, ribosomal ambiguity mutations, G299A and G347U, also increased resistance to Auraplanin. Conclusion: On the basis of the genetic, structural and biochemical studies we hypothesized that Auraplanin acts prevent the transfer from an open to a closed conformation of 30S subunit, in contrast to streptomycin, which promotes the formation of a closed state.