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1
Akter, Sonia, Lis Wollesen de Jonge, Per Møldrup, Mogens Humlekrog Greve, Trine Nørgaard, Peter Lystbæk Weber, Cecilie Hermansen, Abdul Mounem Mouazen, and Maria Knadel. "Visible Near-Infrared Spectroscopy and Pedotransfer Function Well Predict Soil Sorption Coefficient of Glyphosate." Remote Sensing 15, no. 6 (March 22, 2023): 1712. http://dx.doi.org/10.3390/rs15061712.
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The soil sorption coefficient (Kd) of glyphosate mainly controls its transport and fate in the environment. Laboratory-based analysis of Kd is laborious and expensive. This study aimed to test the feasibility of visible near-infrared spectroscopy (vis–NIRS) as an alternative method for glyphosate Kd estimation at a country scale and compare its accuracy against pedotransfer function (PTF). A total of 439 soils with a wide range of Kd values (37–2409 L kg−1) were collected from Denmark (DK) and southwest Greenland (GR). Two modeling scenarios were considered to predict Kd: a combined model developed on DK and GR samples and individual models developed on either DK or GR samples. Partial least squares regression (PLSR) and artificial neural network (ANN) techniques were applied to develop vis–NIRS models. Results from the best technique were validated using a prediction set and compared with PTF for each scenario. The PTFs were built with soil texture, OC, pH, Feox, and Pox. The ratio of performance to interquartile distance (RPIQ) was 1.88, 1.70, and 1.50 for the combined (ANN), DK (ANN), and GR (PLSR) validation models, respectively. vis–NIRS obtained higher predictive ability for Kd than PTFs for the combined dataset, whereas PTF resulted in slightly better estimations of Kd on the DK and GR samples. However, the differences in prediction accuracy between vis–NIRS and PTF were statistically insignificant. Considering the multiple advantages of vis–NIRS, e.g., being rapid and non-destructive, it can provide a faster and easier alternative to PTF for estimating glyphosate Kd.
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Kim, Do-Hyeon, and Jun-Yeop Lee. "Prediction of the Adsorption Behaviors of Radionuclides onto Bentonites Using a Machine Learning Method." Minerals 12, no. 10 (September 25, 2022): 1207. http://dx.doi.org/10.3390/min12101207.
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This study builds a model to predict distribution coefficients (Kd) using the random forest (RF) method and a machine learning model based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB). A database of ten input variables, including the distribution coefficient, pH, initial radionuclide concentrations, solid–liquid ratio, ionic strength, oxidation number, cation exchange capacity, surface area, electronegativity, and ionic radius, was constructed and used for the RF model calculation. The calculation parameters employed in this work included two different hyperparameters, the number of decision trees and the maximum number of variables to divide each node, together with the random seeds inside the RF model. The coefficients of determination were derived with various combinations of hyperparameters and random seeds, and were employed to assess the RF model calculation result. Based on the results of the RF model, the distribution coefficients of 22 target nuclides (Am, Ac, Co, Cm, Cd, Cs, Cu, Na, Np, Ni, Nb, U, Sr, Sn, Pb, Pa, Pu, Po, I, Tc, Th, and Zr) were predicted successfully. Among the various input variables, pH was found to make the highest contribution to determining the distribution coefficient. The novelty of this study lies in the first application of the machine learning method for predicting the Kd value of bentonites, using JAEA-SDB. This study has established a model for reliably predicting the distribution coefficient for various radionuclides that is intended for use in evaluating the Kd value in arbitrary aqueous conditions.
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Zolfaghari, Kiana, Claude R. Duguay, and Homa Kheyrollah Pour. "Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model." Hydrology and Earth System Sciences 21, no. 1 (January 24, 2017): 377–91. http://dx.doi.org/10.5194/hess-21-377-2017.
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Abstract. A global constant value of the extinction coefficient (Kd) is usually specified in lake models to parameterize water clarity. This study aimed to improve the performance of the 1-D freshwater lake (FLake) model using satellite-derived Kd for Lake Erie. The CoastColour algorithm was applied to MERIS satellite imagery to estimate Kd. The constant (0.2 m−1) and satellite-derived Kd values as well as radiation fluxes and meteorological station observations were then used to run FLake for a meteorological station on Lake Erie. Results improved compared to using the constant Kd value (0.2 m−1). No significant improvement was found in FLake-simulated lake surface water temperature (LSWT) when Kd variations in time were considered using a monthly average. Therefore, results suggest that a time-independent, lake-specific, and constant satellite-derived Kd value can reproduce LSWT with sufficient accuracy for the Lake Erie station. A sensitivity analysis was also performed to assess the impact of various Kd values on the simulation outputs. Results show that FLake is sensitive to variations in Kd to estimate the thermal structure of Lake Erie. Dark waters result in warmer spring and colder fall temperatures compared to clear waters. Dark waters always produce colder mean water column temperature (MWCT) and lake bottom water temperature (LBWT), shallower mixed layer depth (MLD), longer ice cover duration, and thicker ice. The sensitivity of FLake to Kd variations was more pronounced in the simulation of MWCT, LBWT, and MLD. The model was particularly sensitive to Kd values below 0.5 m−1. This is the first study to assess the value of integrating Kd from the satellite-based CoastColour algorithm into the FLake model. Satellite-derived Kd is found to be a useful input parameter for simulations with FLake and possibly other lake models, and it has potential for applicability to other lakes where Kd is not commonly measured.
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Estrada-Arriaga, E. B., and N. P. Mijaylova. "A comparison of biodegradation kinetic models applied to estrogen removal with nitrifying activated sludge." Water Science and Technology 62, no. 9 (November 1, 2010): 2183–89. http://dx.doi.org/10.2166/wst.2010.441.
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The biological degradation of estrone (E1), estradiol (E2) and ethinylestradiol (EE2) was studied in batch experiments at typical concentration levels using nitrifying activated sludge from a membrane bioreactor (MBR). Since first-order, pseudo first-order and Monod-type kinetics were observed. Pseudo first order kinetic was reformulated using only the soluble concentrations S and assuming adsorption coefficient KD of the estrogens. For the adsorption coefficients KD determination, activated sludge from MBR was spiked with the respective target compounds and stirred. Finally, the water was analyzed. The KD values of estrogens ranged from 0.323 to 0.474 L/g. Greater than 98% of E1, E2 and EE2 were found to be removed in batch reactors. The measured data were linearly regressed giving R2 values ranging from 0.748 to 0.990. According to these results, the biodegradation kinetics were adjusted to pseudo first-order assuming adsorption coefficient KD and Monod-type kinetic. The biodegradation rate constant k of the estrogens were: E1 and E2 > 78.52 L/gVSS d and 12.41 L/gVSS d for EE2. Monod-type kinetic indicates that these compounds are biodegradated by co-metabolism. E2 was oxidized into E1.
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Castillo-Ramírez, Alejandra, Eduardo Santamaría-del-Ángel, Adriana González-Silvera, Robert Frouin, María-Teresa Sebastiá-Frasquet, Jing Tan, Jorge Lopez-Calderon, Laura Sánchez-Velasco, and Luis Enríquez-Paredes. "A New Algorithm to Estimate Diffuse Attenuation Coefficient from Secchi Disk Depth." Journal of Marine Science and Engineering 8, no. 8 (July 25, 2020): 558. http://dx.doi.org/10.3390/jmse8080558.
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The vertical diffuse attenuation coefficient Kd (PAR) is used for calculating the euphotic zone, the first optical depth that is important for primary productivity models. Currently, Kd (PAR) can be estimated using an irradiometer or a Secchi disk (SD). The main objective of this work is to define a model that can be applied to a wide range of optical marine conditions to estimate Kd (PAR) by SD. We used irradiance profiles and SD depth (ZSD) from 679 stations in various marine regions. Three parametric models were developed, and their statistical performance was evaluated in view of previous approaches reported and remote sensing data. The best results were obtained with an adaptive model representing three cases: clear-water, turbid-water, and a transition zone (R2 = 0.965, MAE = 0.083, RMSD = 0.239, BIAS = 0.01, and MPI = 0.854). Previous models considering a single optical depth figure at which the SD disappears did not capture the marine optical complexity. Our classification of 113 stations with spectral absorption data into Jerlov water types indicated that no unique correspondence existed between estimated Kd (PAR) and water type, making it ambiguous to associate compatible inherent optical properties and chlorophyll with ZSD. Although obtaining Kd (PAR) from ZSD is simple/low-cost, care should be taken in the methodology used to measure ZSD to ensure consistent results across different optical marine conditions.
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Zhang, Yu, Zhantang Xu, Yuezhong Yang, Guifen Wang, Wen Zhou, Wenxi Cao, Yang Li, et al. "Diurnal Variation of the Diffuse Attenuation Coefficient for Downwelling Irradiance at 490 nm in Coastal East China Sea." Remote Sensing 13, no. 9 (April 26, 2021): 1676. http://dx.doi.org/10.3390/rs13091676.
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The diurnal variation of the diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd(490)) has complex characteristics in the coastal regions. However, owing to the scarcity of in situ data, our knowledge on the diurnal variation is inadequate. In this study, an optical-buoy dataset was used to investigate the diurnal variation of Kd(490) in the coastal East China Sea, and to evaluate the Kd(490) L2 products of geostationary ocean color imager (GOCI), as well as the performance of six empirical algorithms for Kd(490) estimation in the Case-2 water. The results of validation show that there was high uncertainty in GOCI L2 Kd(490), with mean absolute percentage errors (MAPEs) of 69.57% and 68.86% and root mean square errors (RMSEs) of 0.70 and 0.71 m−1 compared to buoy-measured Kd12(490) and Kd13(490), respectively. Meanwhile, with the coefficient of determination (R2) of 0.71, as well as the lowest MAPE of 27.31% and RMSE of 0.29 m−1, the new dual ratio algorithm (NDRA) performed the best in estimating Kd(490) in the target area, among the six algorithms. Further, four main types of Kd(490) diurnal variation were found from buoy data, showing different variabilities compared to the area closer to the shore. One typical diurnal variation pattern showed that Kd(490) decreased at flood tide and increased at ebb tide, which was confirmed by GOCI images through the use of NDRA. Hydrometeorological factors influencing the diurnal variations of Kd(490) were also studied. In addition to verifying the predominant impact of tide, we found that the dominant effect of tide and wind on the water column is intensifying sediment resuspension, and the change of sediment transport produced by them are secondary to it.
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Moiseev, S. I., A. I. Buyanovsky, A. N. Deminov, S. V. Klinushkin, and S. A. Moiseeva. "Application of the morphometric maturity coefficient to determine terminal molt in the crab Chionoecetes angulatus from the Okhotsk Sea." Trudy VNIRO 179 (October 26, 2020): 5–25. http://dx.doi.org/10.36038/2307-3497-2020-179-5-25.
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Results of studies on the relationship between the claw morphometric parameters and the carapace width (CW) of the triangle crab (Chionoecetes angulatus) crab from the Sea of Okhotsk presented. For the operational screening and separation of males into morphometrically mature (ММ – large-clawed) and immature (MI – small-clawed) species, it is proposed to use the coefficient of morphometric maturity (K%). This coefficient can be defined as the ratio of claw height to carapace width (KH%) or as the ratio of claw diagonal to carapace width (KD%), expressed as a percentage. When assessing the coefficient of morphometric maturity (K%), the boundary value for KH% is 16, and for KD% it is 35, which allows reliable identification of large-clawed (MM) males at K% values above the boundary values, and small-clawed (MI) males at K% values below the boundary values. Four functional groups were distinguished in males of C. angulatus: 1) MI physiologically immature — CW ≤90 mm, KH% <13.5, and KD% ≤29; 2) MI physiologically mature — CW 90.1–120 mm, KH% 12–16 and KD% 25–35; 3) MI large-sized physiologically sexually mature — CW >120 mm, KH% 13–16 and KD% 29–35; 4) MM morphometrically and functionally mature — CW 74–167 mm, KH% >16 and KD% >35. The correlation of the onset of morphometric maturity with biochemical parameters of hemolymph and with the development of muscle tissue is discussed. For various functional groups of males C. angulatus, an abundance estimate was implemented taking into account the K% coefficient.
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Onyeocha, Veronica O., O. D. Akpan, Ikejiofor A. Onuchukwu, and Maduabuchi A. Chidiebere. "The Dimerization Effects of Some Solutes on the Partition Coefficient kD in Binary Immiscible Solvents." International Letters of Chemistry, Physics and Astronomy 80 (December 2018): 40–52. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.80.40.
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The dimerization of a solute dissolved in binary immiscible solvents shows that the value of the partition coefficient, kD of the solutes are influenced by the dimerization constant, K of the solute in one of the solvents according to the description: (C_X^A)/(C_X^B ) = kD + 2kD2KCxB where CxA and CxB are the concentrations of the solute x in the solvents A and B respectively. Both kD and K are parameters that predict the extent of beneficiation for most minerals. Also, kD is a fundamental parameter that determines the extent of solute recovery during solvent extraction. In this study, it is found that the order K kD and K kD are the effects for acetic and succinic acids respectively in the binary solvents composed of carbon tetrachloride/water and diethylether/water systems respectively. These results suggest that the distributions of these solutes in the solvents are accompanied by the formation of succinic anhydride which is more favoured than the dimerization of the acetic acid. Also, the changes in the values of distribution enthalpies, HD are corroborated to explain these experimental observations.
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Kraus, Cleber Nunes, Daniel Andrade Maciel, Marie Paule Bonnet, and Evlyn Márcia Leão de Moraes Novo. "Phytoplankton Genera Structure Revealed from the Multispectral Vertical Diffuse Attenuation Coefficient." Remote Sensing 13, no. 20 (October 14, 2021): 4114. http://dx.doi.org/10.3390/rs13204114.
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The composition of phytoplankton and the concentration of pigments in their cells make their absorption and specific absorption coefficients key parameters for bio-optical modeling. This study investigated whether the multispectral vertical diffuse attenuation coefficient of downward irradiance (Kd) gradients could be a good framework for accessing phytoplankton genera. In situ measurements of remote sensing reflectance (Rrs), obtained in an Amazon Floodplain Lake (Lago Grande do Curuai), were used to invert Kd, focusing on Sentinel-3/Ocean and Land Color Instrument (OLCI) sensor bands. After that, an analysis based on the organization of three-way tables (STATICO) was applied to evaluate the relationships between phytoplankton genera and Kd at different OLCI bands. Our results indicate that phytoplankton genera are organized according to their ability to use light intensity and different spectral ranges of visible light (400 to 700 nm). As the light availability changes seasonally, the structure of phytoplankton changes as well. Some genera, such as Microcystis, are adapted to low light intensity at 550–650 nm, therefore high values of Kd in this range would indicate the dominance of Microcysts. Other genera, such as Aulacoseira, are highly adapted to harvesting blue-green light with higher intensity and probably grow in lakes with lower concentrations of colored dissolved organic matter that highly absorbs blue light (405–498). These findings are an important step to describing phytoplankton communities using orbital data in tropical freshwater floodplains. Furthermore, this approach can be used with biodiversity indexes to access phytoplankton diversity in these environments.
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Prasetyo, Budhi Agung, Vincentius Paulus Siregar, Syamsul Bahri Agus, and Wikanti Asriningrum. "IN-SITU MEASUREMENT OF DIFFUSE ATTENUATION COEFFICIENT AND ITS RELATIONSHIP WITH WATER CONSTITUENT AND DEPTH ESTIMATION OF SHALLOW WATERS BY REMOTE SENSING TECHNIQUE." International Journal of Remote Sensing and Earth Sciences (IJReSES) 14, no. 1 (June 21, 2017): 47. http://dx.doi.org/10.30536/j.ijreses.2017.v14.a2682.
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Diffuse attenuation coefficient, Kd(λ), has an empirical relationship with water depth, thus potentially to be used to estimate the depth of the water based on the light penetration in the water column. The aim of this research is to assess the relationship of diffuse attenuation coefficient with the water constituent and its relationship to estimate the depth of shallow waters of Air Island, Panggang Island and Karang Lebar lagoons and to compare the result of depth estimation from Kd model and derived from Landsat 8 imagery. The measurement of Kd(λ) was carried out using hyperspectral spectroradiometer TriOS-RAMSES with range 320 – 950 nm. The relationship between measurement Kd(λ) on study site with the water constituent was the occurrence of absorption by chlorophyll-a concentration at the blue and green spectral wavelength. Depth estimation using band ratio from Kd(λ) occurred at 442,96 nm and 654,59 nm, which had better relationship with the depth from in-situ measurement compared to the estimation based on Landsat 8 band ratio. Depth estimated based on Kd(λ) ratio and in-situ measurement are not significantly different statistically. Depth estimated based on Kd(λ) ratio and in-situ measurement are not significantly different statistically. However, depth estimation based on Kd(λ) ratio was inconsistent due to the bottom albedo reflection because the Kd(λ) measurement was carried out in shallow waters. Estimation of water depth based on Kd(λ) ratio had better results compared to the Landsat 8 band ratio.
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Zeng, Qing Ling, Lu Wang, Chun Hua Shen, Fei Li, and Zhen Ming Zhou. "Adsorption Characteristics of Estrone to Aerobic Activated Sludge." Applied Mechanics and Materials 295-298 (February 2013): 12–16. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.12.
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Batch experiments were conducted to measure the sorption capacities of estrone (E1) to aerobic activated sludge. The effect of temperature on E1 sorption was investigated at the temperatures of 5-35oC. The results showed that E1 sorption equilibrium was reached at 15min. E1 sorption on the sludge fitted both Freundlich and linear sorption isotherm models. Distribution coefficients (Kd) of E1 to aerobic inactivated sludge was 546.5 L∙kg-1 at 25oC. The effect of temperature on sorption indicated that lower temperature benefited the sorption. The distribution coefficients (Kd) and sorption rate both decreased with the increased temperature. Kd of E1 to aerobic inactivated sludge was decreased by about 44%; the sorption rate was decreased by about 13% when temperature increased from 5 to 35oC. The specific sorption coefficient KOM or KOC was also used to describe the sorption capacity, which also decreased with increased temperature. Sorption thermodynamics indicated that the sorption process was exothermic and spontaneous.
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Onyeocha, Veronica O., O. D. Akpan, Ikejiofor A. Onuchukwu, and Maduabuchi A. Chidiebere. "The Dimerization Effects of Some Solutes on the Partition Coefficient k<sub>D</sub> in Binary Immiscible Solvents." International Letters of Chemistry, Physics and Astronomy 80 (December 4, 2018): 40–52. http://dx.doi.org/10.56431/p-794j27.
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The dimerization of a solute dissolved in binary immiscible solvents shows that the value of the partition coefficient, kD of the solutes are influenced by the dimerization constant, K of the solute in one of the solvents according to the description: (C_X^A)/(C_X^B ) = kD + 2kD2KCxB where CxA and CxB are the concentrations of the solute x in the solvents A and B respectively. Both kD and K are parameters that predict the extent of beneficiation for most minerals. Also, kD is a fundamental parameter that determines the extent of solute recovery during solvent extraction. In this study, it is found that the order K kD and K kD are the effects for acetic and succinic acids respectively in the binary solvents composed of carbon tetrachloride/water and diethylether/water systems respectively. These results suggest that the distributions of these solutes in the solvents are accompanied by the formation of succinic anhydride which is more favoured than the dimerization of the acetic acid. Also, the changes in the values of distribution enthalpies, HD are corroborated to explain these experimental observations.
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Sedeño-Díaz, Jacinto Elías, Eugenia López-López, Erick Mendoza-Martínez, Alexis Joseph Rodríguez-Romero, and Sandra Soledad Morales-García. "Distribution Coefficient and Metal Pollution Index in Water and Sediments: Proposal of a New Index for Ecological Risk Assessment of Metals." Water 12, no. 1 (December 19, 2019): 29. http://dx.doi.org/10.3390/w12010029.
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The Lake of Texcoco is a closed basin with soils that confer salinity, conductivity, and alkalinity to it. It has undergone a reduction in size, incorporation of wastewater, and short-term desiccation, and includes temporary wetlands interconnected during the rainy season, some of which receive treated wastewater. Sediments contain metals, thus affecting water quality. Five artificial lakes were studied, and 12 metals (As, Ba, Cd, Cu, Cr, Fe, Mg, Mn, Hg, Ni, Pb, and Zn) were monitored bimonthly in water and sediments from June 2015 to March 2018. The Metal Pollution Index (MPI) and the Distribution Coefficient (Kd) were computed. Fe and Cd were the most and least stable metals in sediments, respectively (mean Log(Kd) = 4.24 and 2.079). Based on Log(Kd), metals were ranked as Fe > Mn > Zn > Cu > Mg > Cr > Ni > Ba > Pb > Hg > As > Cd. Log(Kd) values < 3 and > 5 indicate that metals occur mainly in water and sediments, respectively. The Mean Distribution Coefficient Log(Kd MPI) is a novel index proposed to assess ecological risk from metals in a water body. This index allows determining the phase (liquid or solid) where metals predominate, negatively affecting either free-swimming or benthic organisms. Log(Kd MPI) values indicated that metals occur primarily in the liquid phase in all lakes studied.
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Decarreau, A., and S. Petit. "Fe3+/Al3+ partitioning between tetrahedral and octahedral sites in dioctahedral smectites." Clay Minerals 49, no. 5 (December 2014): 657–65. http://dx.doi.org/10.1180/claymin.2014.049.5.03.
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AbstractThe distribution of Al3+ and Fe3+ between octahedral and tetrahedral sites of dioctahedral smectites was shown to be controlled by a partition coefficient Kd(4/6) = [(Fe3+)4×(Al3+)6]/[(Fe3+)6×(Al3+)4]. The Kd(4/6) value is near 0.006 for natural dioctahedral smectites, formed between 2 and ~100°C, and near 0.0174 for smectites synthesized at 200°C. These Kd(4/6) values, obtained from both chemical and spectroscopic data, were consistent with those calculated using the ionic radii of cations and Brice’s model (Brice, 1975). The partition coefficient approach explained well why for natural and synthetic dioctahedral smectites no tetrahedral Fe3+ is detected when the total Fe3+ content is below 3 atoms per unit cell (24 oxygen atoms).
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Baborová, Lucie, Eva Viglašová, and Dušan Vopálka. "Comparison of Sr Transport in Compacted Homoionous Na and Ca Bentonite Using a Planar Source Method Evaluated at Ideal and Non-Ideal Boundary Condition." Water 13, no. 11 (May 28, 2021): 1520. http://dx.doi.org/10.3390/w13111520.
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With the aim to determine the influence of dominant interlayer cation on the sorption and diffusion properties of bentonite, diffusion experiments with Sr on the compacted homoionous Ca- and Na-forms of Czech natural Mg/Ca bentonite using the planar source method were performed. The bentonite was compacted to 1400 kg·m−3, and diffusion experiments lasted 1, 3 or 5 days. Two methods of apparent diffusion coefficient Da determination based on the analytical solution of diffusion equation for ideal boundary conditions in a linear form were compared and applied. The determined Da value for Ca-bentonite was 1.36 times higher than that for Na-bentonite sample. Values of Kd were determined in independent batch sorption experiments and were extrapolated for the conditions of compacted bentonite. In spite of this treatment, the use of Kd values determined by batch sorption experiments on a loose material for the determination of effective diffusion coefficient De values from planar source diffusion experiments proved to be inconsistent with the standard Fickian description of diffusion taking into account only the pore diffusion in compacted bentonite. Discrepancies between Kd and De values were measured in independent experiments, and those that resulted from the evaluation of planar source diffusion experiments could be well explained by the phenomenon of surface diffusion. The obtained values of surface diffusion coefficients Ds were similar for both studied systems, and the predicted value of total effective diffusion coefficient De(tot) describing Sr transport in the Na-bentonite was four times higher than in the Ca-bentonite.
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Dahm, Donald J., Kevin D. Dahm, and Karl H. Norris. "Obtaining Material Absorption Properties from Remission Spectra of Directly Illuminated, Layered Samples." Journal of Near Infrared Spectroscopy 10, no. 1 (January 2002): 1–13. http://dx.doi.org/10.1255/jnirs.316.
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The effective linear absorption coefficient, K, obtained in transflection from directly illuminated samples made up of layers of thickness d, may be approximately related to the linear absorption coefficient, k, of the material making up the layers through the following empirical equations: k = [(1 – ½ exp(–2 Kd)] K and K = [(1 + exp(–4 kd)] k. The fractions of incident intensity absorbed or remitted by one layer may be modeled by assuming that that the light that moves through a sample has both the characteristics of directed and diffuse radiation.
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Yang, Chaoyu, Haibin Ye, and Shilin Tang. "Seasonal Variability of Diffuse Attenuation Coefficient in the Pearl River Estuary from Long-Term Remote Sensing Imagery." Remote Sensing 12, no. 14 (July 15, 2020): 2269. http://dx.doi.org/10.3390/rs12142269.
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We evaluated six empirical and semianalytical models of the diffuse attenuation coefficient at 490 nm (Kd(490)) using an in situ dataset collected in the Pearl River estuary (PRE). A combined model with the most accurate performance (correlation coefficient, R2 = 0.92) was selected and applied for long-term estimation from 2003 to 2017. Physical and biological processes in the PRE over the 14-year period were investigated by applying satellite observations (MODIS/Aqua data) and season-reliant empirical orthogonal function analysis (S-EOF). In winter, the average Kd(490) was significantly higher than in the other three seasons. A slight increasing trend was observed in spring and summer, whereas a decreasing trend was observed in winter. In summer, a tongue with a relatively high Kd(490) was found in southeastern Lingdingyang Bay. In Eastern Guangdong province (GDP), the relatively higher Kd(490) value was found in autumn and winter. Based on the second mode of S-EOF, we found that the higher values in the eastern GDP extended westward and formed a distinguishable tongue in winter. The grey relational analysis revealed that chlorophyll-a concentration (Cchla) and total suspended sediment concentration (Ctsm) were two dominant contributors determining the magnitude of Kd(490) values. The Ctsm-dominated waters were generally located in coastal and estuarine turbid waters; the Cchla-dominated waters were observed in open clear ocean. The distribution of constituents-dominated area was different in the four seasons, which was affected by physical forces, including wind field, river runoff, and sea surface temperature.
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Zhang, Xianqing, Cai Li, Wen Zhou, Yuanning Zheng, Wenxi Cao, Cong Liu, Zhantang Xu, Yuezhong Yang, Zeming Yang, and Fei Chen. "Study of the Profile Distribution of the Diffuse Attenuation Coefficient and Secchi Disk Depth in the Northwestern South China Sea." Remote Sensing 15, no. 6 (March 10, 2023): 1533. http://dx.doi.org/10.3390/rs15061533.
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The diffuse attenuation coefficient for the downwelling irradiance Kdz,λ is a critical parameter in terms of the optical properties of the ocean. In the northwestern South China Sea, there are complex physical processes, and the accurate estimation of Kdz,λ in the northwestern South China Sea is critical for the study and application of the underwater light field and water constituents. In this study, using Hydrolight 6.0 (HL60) software, Kdz,λ was simulated based on the inherent optical properties (IOPs) and chlorophyll a concentration dataset in the northwestern South China Sea. The simulations were in good agreement with the results calculated by the model of Lee (2005), and the spectral characteristics of Kdz,λ were consistent with several oceanic types according to Jerlov’s classification. The horizontal and vertical distribution characteristics of Kd(z,490) were studied in the two typical upwelling areas of eastern Hainan Island and eastern Vietnam. Kd(z,490) in eastern Hainan Island exhibited an overall decreasing trend from west to east at the same depth, while the vertical depth of the maximum value of Kd(z,490) in eastern Hainan Island was found to increase from west to east, which was significantly associated with the distribution trend of the temperature and salinity. Kd(z,490) in eastern Vietnam exhibited unique horizontal and vertical distribution characteristics due to upwelling, with a low temperature and high salinity. A satisfactory linear relationship between Kd(z,490) and Kdz,λ was found from 420 to 580 nm with R2 > 0.76, root mean square (RMSE) ≤ 0.010 m−1, and mean absolute percentage error (MAPE) < 9%, and this result indicated that Kdz,λ from 420~580 nm could be estimated with Kd(z,490). The regression accuracy sharply decreased after 580 nm, indicating that Kdz,λ estimation based on Kd(z,490) can be more suitably achieved from 420~580 nm and becomes inaccurate after 580 nm. Based on the simulations, an empirical relationship for ZSDD estimation involving Kd,10%490 was developed, and ZSDD in the northwestern South China Sea was calculated, with a range of 5–23 m and a suitable agreement with ZSDD obtained via the method of Lee (2018).
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Bailin, Cao, and Chen Huitang. "PD-Based Trajectory Tracking Control for Robot Manipulators." Journal of Dynamic Systems, Measurement, and Control 115, no. 3 (September 1, 1993): 566–69. http://dx.doi.org/10.1115/1.2899140.
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In this paper, it is proved that a trajectory tracking system of a manipulator is globally stable if the system is controlled under the decentralized PD control law plus a sliding term with a constant coefficient, and the norm of the coefficient matrix of its differential term is no less than that of the centripetal and Coriolis’ force term corresponding to the desired angular velocity, i.e., ∥Kd∥ ≥ ∥C(q, q˙d)∥. Condition ∥Kd∥ ≥ ∥C(q, q˙d)∥ implies that Kd increases only with q˙d instead of q˙. A type of globally asymptotically stable adaptive sliding mode PD-based control scheme is proposed, and the proof of stability of the system is also given. It is easy to implement in real-time compared with other adaptive control laws as no estimation of gravitational and frictional forces is necessary.
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Kusakabe, Masashi, and Hyoe Takata. "Temporal trends of 137Cs concentration in seawaters and bottom sediments in coastal waters around Japan: implications for the Kd concept in the dynamic marine environment." Journal of Radioanalytical and Nuclear Chemistry 323, no. 1 (November 30, 2019): 567–80. http://dx.doi.org/10.1007/s10967-019-06958-z.
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AbstractRadioactivity concentrations of 137Cs in seawaters and bottom sediments have been measured in the coastal waters off all nuclear power plant sites in Japan. Sediment distribution coefficient (Kd) values obtained before the Fukushima Daiichi Nuclear Power Plant accident were variable and related to the specific surface area of the bottom sediment. A mathematical model suggested that before the accident the Kd values were in the transient state approaching a dynamic equilibrium with a converged Kd value of 1000–1600. Based on a post-accident mathematical model, the apparent Kd reached the maximum of about 104 and then decreased until now, converging to 6 × 103 on average.
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Fakhruradzi, Sheikh, and A. Fitriadhy. "Optimization on fishing net porosity of twin pontoon floating breakwater in waves." Journal of Mechanical Engineering and Sciences 16, no. 1 (March 23, 2022): 8801–10. http://dx.doi.org/10.15282/jmes.16.1.2022.12.0695.
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Chaotic process in wave passing through pores on the attached fishing net between twin pontoons of floating breakwater (TPFB) may lead to several severe problems relating to the hydrodynamic performance of such coastal structure. In presence of relatively fine pores, the wave transmission coefficient (Kt) tends to diminish while the reflection coefficient (Kr) will likely increase, or vice versa for coarse ones. The circumstance requires a complete design optimization study into obtaining an optimum porosity. This paper presents optimization on the fishing net porosity (n) of TPFB using artificial intelligence (AI) model. Here, a multi-objective evolutionary algorithm with various genetic parameters is proposed to search for optimum n ratio through primarily minimizing transmission (Kt) and reflection coefficients (Kr) while maximizing energy dissipation coefficient (Kd). In addition, a computational fluid dynamic (CFD) programme is developed using an extended Reynolds Average Navier-Stokes (RANS) solver for a solid-permeable obstacle. Several parameters such as wavelengths and porosity ratios including a set of optimization criteria, have been taken into account in the simulation, where the optimum solution is then selected from various populations. Meanwhile, the optimum result will be qualitatively evaluated, in which it is visualized by the characteristic patterns of induced energy dissipation. The results revealed that the optimization algorithm is effectively capable of determining global trade-offs between Kt, Kr, and Kd. As compared to the existing model, Kt and Kr decrease to less than 0.85 and 0.42 respectively, whereas Kd was increased up to 0.34 resulting in optimum hydrodynamics of TPFB indicated by further enhancement in the rate of energy dissipation across TPFB entanglement. For validation, the numerical model can fairly simulate well on the hydrodynamics of structure.
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Oberlander, Tyler J., Bernadette L. Olson, and Lee Weidauer. "Test-Retest Reliability of the King-Devick Test in an Adolescent Population." Journal of Athletic Training 52, no. 5 (May 1, 2017): 439–45. http://dx.doi.org/10.4085/1062-6050-52.2.12.
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Context: The King-Devick (KD) test is a screening tool designed to assess cognitive visual impairments, namely saccadic rhythm, postconcussion. Test-retest reliability of the KD in a healthy adolescent population has not yet been established. Objective: To investigate the overall test-retest reliability of the KD among a sample of healthy adolescents. Additionally, we sought to determine if sex and age influenced reliability. Design: Cross-sectional study. Setting: Secondary school. Patients or Other Participants: Sixty-eight healthy adolescents, 41 boys (age = 15.4 ± 1.9 years) and 27 girls (age = 15.4 ± 1.9 years). Main Outcome Measure(s): Participants completed the KD (version 1) at 3 testing sessions (days 1, 30, and 45) following standard instructions. We recorded total time to complete the reading of 3 cards for each participant during each testing session. Two-way random-effects intraclass correlation coefficients (ICCs) using single measurements repeated over time and repeatability coefficients were calculated. Linear mixed models were used to determine whether differences existed at each testing time and to examine whether changes that took place among visits were different by sex or age. Results: Adolescents who completed the KD demonstrated acceptable reliability (ICC = 0.81; 95% confidence interval = 0.73, 0.87); however, the repeatability coefficient was large (±8.76 seconds). The sample demonstrated improvements between visits 1 and 2 (mean ± standard error = 4.3 ± 0.5 seconds, P < .001) and between visits 2 and 3 (2.4 ± 0.5 seconds, P < .001) for a total improvement of 6.9 seconds over 3 tests. No significant visit-by-sex or visit-by-age interactions were observed. Conclusions: Despite the ICC being clinically acceptable, providers using the KD test for serial assessment of concussion in adolescents should be cautious in interpreting the results due to a large learning effect. Incorporating multiple measures can ensure accurate detection of sport concussion.
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Ganf, GG, RL Oliver, and AE Walsby. "Optical properties of Gas-vacuolate cells and colonies of Microcystis in relation to light Attenuation in a Turbid, Stratified Reservoir (Mount Bold Reservoir, South Australia)." Marine and Freshwater Research 40, no. 6 (1989): 595. http://dx.doi.org/10.1071/mf9890595.
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Profiles of downwelling and upwelling irradiance were measured in a stratified, turbid reservoir, when Microcystis aeruginosa formed a significant proportion of the phytoplankton community. The attenuation coefficient (Kd) was c. 2.1 m-1 and the reflectance (R) c. 0.03. Application of Kirk's simulation model relating apparent and inherent optical properties enabled calculation of coefficients of absorption (a; 1.3-1.6 m-') and scattering (6; 5-7 m-1). The asymptotic diffuse backscattering coefficient (0.2 m-1) was derived from the relationship b′b = 3.6 RaKd, a slight modification of Kirk's original equation. Turbidity measurements supported the general rule that nephelometric turbidity was numerically equivalent to the scattering coefficient. There was good agreement between the measured light profile and one reconstructed from inherent optical properties using the relationship between Kd, a and b. The optical properties of cells and colonies of Microcystis were investigated before and after the collapse of gas vacuoles. The Chla-specific absorption coefficient for cells (0.0138 m2 mg,-1 Chla) was higher than for colonies (0.0106 m2 mg,-1 Chla) at a depth equivalent to 0.2 m. Both coefficients decreased with increasing depth as the spectral composition changed. The Chla-specific scattering coefficient for vacuolate cells (0.14 m2 mg,-1 Chla) was greater than for colonies (0.11 m2 mg,-1 Chla), and a similar correspondence occurred for non-vacuolate cells and colonies (0.029 and 0.020 m2 mg,-1 Chla respectively). These measurements illustrate the package effect and also that c. 80% of light scattering is due to gas vacuoles. The relationship between pressure-sensitive turbidity and gas-vacuole volume suggested that 1 gL mL-1 was equivalent to a turbidity of 2 NTU. These optical characteristics, combined with the buoyant nature of Microcystis, suggest that it is a canopy species.
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Corcoran, Forrest, and Christopher E. Parrish. "Diffuse Attenuation Coefficient (Kd) from ICESat-2 ATLAS Spaceborne Lidar Using Random-Forest Regression." Photogrammetric Engineering & Remote Sensing 87, no. 11 (November 1, 2021): 831–40. http://dx.doi.org/10.14358/pers.21-00013r2.
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This study investigates a new method for measuring water turbidity—specifically, the diffuse attenuation coefficient of downwelling irradiance Kd —using data from a spaceborne, green-wavelength lidar aboard the National Aeronautics and Space Administration's ICESat-2 satellite. The method enables us to fill nearshore data voids in existing Kd data sets and provides a more direct measurement approach than methods based on passive multispectral satellite imagery. Furthermore, in contrast to other lidar-based methods, it does not rely on extensive signal processing or the availability of the system impulse response function, and it is designed to be applied globally rather than at a specific geographic location. The model was tested using Kd measurements from the National Oceanic and Atmospheric Administration's Visible Infrared Imaging Radiometer Suite sensor at 94 coastal sites spanning the globe, with Kd values ranging from 0.05 to 3.6 m –1 . The results demonstrate the efficacy of the approach and serve as a benchmark for future machine-learning regression studies of turbidity using ICESat-2.
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Wakamori, M., Y. Ikemoto, and N. Akaike. "Effects of two volatile anesthetics and a volatile convulsant on the excitatory and inhibitory amino acid responses in dissociated CNS neurons of the rat." Journal of Neurophysiology 66, no. 6 (December 1, 1991): 2014–21. http://dx.doi.org/10.1152/jn.1991.66.6.2014.
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1. Effects of two volatile anesthetics [halothane (Hal) and enflurane (Enf)] and a volatile convulsant [hexafluorodiethyl ether (HFE)] on amino acid-induced membrane currents in neurons dissociated from the nucleus tractus solitarius of the rat were examined. The dissociated neurons were voltage clamped in the whole-cell mode of the patch-clamp technique. All drugs were applied with a microperfusion system, termed the "Y-tube" method. 2. The glutamate (Glu)-induced excitatory response was slightly reduced by both the anesthetics. The responses to three agonists at Glu receptor were depressed by Hal (10(-3) M) in the rank order of quisqualate greater than N-methyl-D-aspartate greater than kainate. HFE slightly increased the Glu response at a high concentration of 2 x 10(-3) M. 3. The gamma-aminobutyric acid (GABA)-induced chloride current (ICl) was enhanced by both anesthetics. The dissociation constant (Kd) for the enhancement was 2.3 x 10(-4) M for Hal and 2.1 x 10(-4) M for Enf, and the Hill coefficient was 1.6 for Hal and 1.5 for Enf. HFE depressed the GABA response with a Kd of 8.7 x 10(-5) M and a Hill coefficient of 0.84. 4. Hal (10(-3) M) and Enf (10(-3) M) decreased the Kd of the GABA concentration-response curve from 3.5 x 10(-6) to 10(-6) and 1.9 x 10(-6) M, respectively, without changing the maximum response or the Hill coefficient (1.5). In the presence of HFE (10(-4) M), the Kd was increased to 1.4 x 10(-5) M and the Hill coefficient was slightly changed to 1.2.(ABSTRACT TRUNCATED AT 250 WORDS)
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Bédard, Jean H. "Parameterization of the Fe=Mg exchange coefficient (Kd) between clinopyroxene and silicate melts." Chemical Geology 274, no. 3-4 (July 2010): 169–76. http://dx.doi.org/10.1016/j.chemgeo.2010.04.003.
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Ganetsos, G. "Prediction of the distribution coefficient (Kd) variation with operating conditions in chromatographic systems." Journal of Chromatography A 411 (January 1987): 81–94. http://dx.doi.org/10.1016/s0021-9673(00)93961-x.
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Sonon, Leticia S., and A. Paul Schwab. "Adsorption Characteristics of Atrazine and Alachlor in Kansas Soils." Weed Science 43, no. 3 (September 1995): 461–66. http://dx.doi.org/10.1017/s0043174500081479.
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The adsorption of atrazine and alachlor was studied on samples of three horizons from soils with different textures and organic carbon contents. Soils were equilibrated with five concentrations of atrazine and alachlor using batch techniques. Adsorption affinity for atrazine and alachlor was approximated by the Freundlich constant (Kf), distribution coefficient (Kd), and the normalizedKdbased on organic carbon (Koc). Adsorption was not significantly correlated with soil depth, clay content, or organic carbon. Atrazine adsorption was a linear function of equilibrium concentration for nearly all soil horizons but was nonlinear in most horizons for alachlor. The extent of atrazine adsorption was greater in all horizons of the fine-textured soils (Kd= 1.5 to 5.5) compared to coarse-textured soils (Kd= 0.40 to 0.87). The same general trends with texture were not apparent for alachlor. Conversion ofKdtoKocfailed to reduce the variability in the linear adsorption coefficient for atrazine and alachlor in the different soils of this study.
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Uthman, Qudus O., Davie M. Kadyampakeni, Peter Nkedi-Kizza, Samuel Kwakye, and Neriman Tuba Barlas. "Boron, Manganese, and Zinc Sorption and Leaf Uptake on Citrus Cultivated on a Sandy Soil." Plants 11, no. 5 (February 26, 2022): 638. http://dx.doi.org/10.3390/plants11050638.
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Solute fate in soil-plant continuum could either be soil or leaf uptake or leaching beyond the rooting zone. An adsorption coefficient (KD) is an important chemical property to describe the interaction between the solute and soil, affecting the solute movement in soils from one point to another. Boron (B), manganese (Mn), and zinc (Zn) uptake are evident in the leaves as a constituent of photosynthesis and other plant body-building mechanisms for growth and development. This study investigates the availability of micronutrients (B, Mn, and Zn) to citrus trees through modified application methods and rates. Leaf samples were collected from experimental plots arranged in a randomized complete block design, with 4 micronutrient treatments: control, foliar ×1, foliar ×2, and soil ×1. Boron, Mn, and Zn rates were 1.12, 10.08, and 5.60 kg ha−1, respectively. Composite soil samples were randomly collected at 5 points, and a 1-point adsorption study was conducted in 4 soil depths at an increment of 15 cm from the soil surface. Adsorption coefficient (KD) for Mn and B was 22 and 3 times higher at 0–15 cm than at soil depth of 15–60 cm. The adsorption coefficient (KD) for Zn was 2.5 times greater at 0–15 cm than 15–30 cm soil depth, while there was little or no sorption at 30–60 cm. Leaf Mn and Zn concentrations showed that foliar spray was 2 times higher than the soil application method, while B showed that the soil application method was 2 times higher than foliar application method for 2 seasons sampling events. Thus, the behavior of B, Mn, and Zn in the soil via adsorption coefficient (KD) reflects the availability of B, Mn, and Zn in the citrus leaves.
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Yamaguchi, Tetsuji, Saki Ohira, Ko Hemmi, Logan Barr, Asako Shimada, Toshikatsu Maeda, and Yoshihisa Iida. "Consideration on modeling of Nb sorption onto clay minerals." Radiochimica Acta 108, no. 11 (November 26, 2020): 873–77. http://dx.doi.org/10.1515/ract-2020-0006.
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AbstractSorption distribution coefficient (Kd) of niobium-94 on minerals are an important parameter in safety assessment of intermediate-depth disposal of waste from core internals etc. The Kd of Nb on clay minerals in Ca(ClO4)2 solutions were, however, not successfully modeled in a previous study. The high distribution coefficients of Nb on illite in Ca(ClO4)2 solutions were successfully reproduced by taking Ca–Nb–OH surface species into account. Solubility of Nb was studied in Ca(ClO4)2 solutions and the results were reproduced by taking an aqueous Ca–Nb–OH complex species, CaNb(OH)6+, into account in addition to previously reported Nb(OH)6− and Nb(OH)72−. Based on this aqueous speciation model, the Ca–Nb–OH surface species responsible for the sorption of Nb on illite in Ca(ClO4)2 solutions was presumed to be X_OCaNb(OH)6. Although uncertainties exist in the speciation of aqueous Ca–Nb–OH species, the result of this study proposed a possible mechanism for high distribution coefficient of Nb on illite in Ca(ClO4)2 solutions. The mechanism includes Ca–Nb–OH complex formation in aqueous, solid and surface phases.
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Tiwari, S. P., and P. Shanmugam. "An optical model for deriving the spectral particulate backscattering coefficients in oceanic waters." Ocean Science 9, no. 6 (November 21, 2013): 987–1001. http://dx.doi.org/10.5194/os-9-987-2013.
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Abstract. An optical model is developed based on the diffuse attenuation coefficient (Kd) to estimate particulate backscattering coefficients bbp(λ) in oceanic waters. A large in situ data set is used to establish robust relationships between bbp(530) and bbp(555) and Kd(490) using an efficient nonlinear least-square method which uses the trust region algorithm with Bisquare weights scheme to adjust the coefficients. These relationships are obtained with good correlation coefficients (R2 = 0.786 and 0.790), low root mean square error (RMSE = 0.00076 and 0.00072) and 95% confidence bounds. The new model is tested with three independent data sets: the NOMAD SeaWiFS Match ups, OOXIX IOP algorithm workshop evaluation data set (Version 2.0w APLHA), and IOCCG simulated data set. Results show that the new model makes good retrievals of bbp at all key wavelengths (from 412–683 nm), with statistically significant improvements over other inversion models. Thus, the new model has the potential to improve our present knowledge of particulate matter and their optical variability in oceanic waters.
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Tiwari, S. P., and P. Shanmugam. "An optical model for deriving the spectral particulate backscattering coefficients in clear and turbid coastal waters." Ocean Science Discussions 10, no. 1 (February 4, 2013): 261–90. http://dx.doi.org/10.5194/osd-10-261-2013.
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Abstract. An optical model is developed based on the diffuse attenuation coefficient (Kd) to estimate particulate backscattering coefficients bbp(λ) in clear and turbid coastal waters. A large in-situ data set is used to establish robust relationships between bbp(530) and bbp(555) and Kd(490) using an efficient nonlinear least square method which uses the Trust-Region algorithm with Bisquare weights scheme to adjust the coefficients. These relationships are obtained with good correlation coefficients (R2 = 0.786 and 0.790), low Root Mean Square Error (RMSE = 0.00076 and 0.00072) and 95% confidence bounds. The new model is tested with two independent data sets such as the NOMAD SeaWiFS Match-ups and OOXIX IOP algorithm workshop evaluation data set (Version 2.0w APLHA). Results show that the new model makes good retrievals of bbp at all key wavelengths (from 412–683 nm), with statistically significant improvements over other inversion models. Thus, the new model has the potential to improve our knowledge of particulate matters and their optical variability in both clear and turbid coastal waters.
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de Tello, Clédola C. O., Daisy M. M. dos Santos, and Thais B. Teixeira. "Study of the sorption and modelling of cesium by a Brazilian bentonite using PHREEQC." MRS Advances 5, no. 5-6 (2020): 245–52. http://dx.doi.org/10.1557/adv.2020.57.
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ABSTRACTTo estimate the cesium sorption by the bentonite and to obtain the isotherms, some batch-adsorption experiments are being carried out, being the Kd (retardation coefficient) calculated from these isotherms. One-dimensional flow cell was constructed to measure the bentonite permeability regarding to a cesium solution, which results will be used to evaluate the diffusion coefficient – D. It will be used the PHREEQC software to model the transport of the cesium radionuclide through this bentonite with the Kd and D data. The modelling of radionuclide transport in the Brazilian materials will contribute to evaluate the efficiency of multi-barriers system of the national repository, because it is one of its safety criteria.
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Setiawan, Budi, and Heni Suseno. "Study of Distribution Coefficient of 90Sr on Citumbuk Bentonite and Sukaramai Kaolinite." EKSPLORIUM 38, no. 1 (June 21, 2017): 1. http://dx.doi.org/10.17146/eksplorium.2017.38.1.3056.
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ABSTRACTThe study of distribution coefficient of strontium on bentonite and kaolinite samples, collected from Citumbuk, Bogor and Sukaramai, Padang, has been investigated under batch experiments. The sorption ratio was determined as a function of time, ionic strength and Sr concentration in the solution. The strontium wasextensively absorbed in the samples, with Kd values of 13,700 and 1,600 mL/g for bentonite and kaolinite samples respectively. The other results showed that ionic strength of the solution and initial concentration of Sr have given an effect to 90Sr sorption onto samples. ABSTRAKStudi tentang koefisien distribusi dari stronsium pada sampel bentonit dan kaolin yang diambil dari lokasi Citumbuk, Bogor dan Sukaramai, Padang, telah diteliti secara catu. Rasio penyerapan ditentukan sebagai fungsi waktu, kekuatan ionic dan konsentrasi Sr di larutan. Stronsium telah terserap dengan baik pada sampel, dengan nilai Kd adalah 13.700 dan 1.600 mL/g masing-masing untuk sampel bentonite dan kaolin. Hasil lainnya menunjukkan bahwa kekuatan ionik dan konsentrasi awal Sr di larutan telah memberikan pengaruh pada penyerapan 90Sr ke dalam sampel.
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Chiang, Yvonne, A. Jerry Kresge, Oleg Sadovski, Xiaofeng Zeng, and Yu Zhu. "Kinetics and mechanism of acid-catalyzed hydrolysis of the diazo functional groups of 1-diazo-2-indanone and 2-diazo-1-indanone in aqueous solution." Canadian Journal of Chemistry 83, no. 9 (September 1, 2005): 1202–6. http://dx.doi.org/10.1139/v05-115.
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Rates of hydrolysis of 1-diazo-2-indanone and 2-diazo-1-indanone were measured in dilute aqueous perchloric acid solutions using both H2O and D2O as the solvent, and rates of hydrolysis of the latter substrate were measured in dilute aqueous (H2O only) formic acid buffer solutions as well. The data for 1-diazo-2-indanone gave the hydronium ion catalytic coefficient kH+ = 5.7 × 103 (mol/L)1 s1 and the isotope effect kH+/kD+ = 2.9. The normal direction (kH/kD > 1) of this isotope effect was taken as evidence for a reaction mechanism involving rate-determining hydron transfer from the hydronium ion to the substrate's diazo carbon atom; followed by rapid displacement of diazo nitrogen by a water molecule, giving the observed 1-hydroxy-2-indanone product. The data for 2-diazo-1-indanone, on the other hand, gave a hydronium ion catalytic coefficient two orders of magnitude greater than the value for 1-diazo-2-indanone (kH+ = 5.9 × 101 (mol/L)1 s1), and an isotope effect near unity (kH+/kD+ = 1.2). It is argued that this isotope effect represents a situation in which diazo carbon hydronation and displacement of diazo nitrogen are each partly rate determining, a conclusion supported by incipient saturation of buffer catalysis in the formic acid buffer solutions. The 100-fold difference in hydronium ion catalytic coefficients for the two substrates is rationalized in terms of differing electron densities on the diazo carbon atoms.Key words: diazo compound hydrolysis, solution kinetics, acid catalysis, solvent isotope effects, buffer catalysis saturation.
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Gouy, V., and R. Bélamie. "Using the Creams Pesticides Transfer Sub-Model at a Rainfall Simulation Scale." Water Science and Technology 28, no. 3-5 (August 1, 1993): 679–83. http://dx.doi.org/10.2166/wst.1993.0473.
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The pesticide sub-model of CREAMS was tested to describe pesticides transfer into runoff generated by a rainfall simulation. Adsorption coefficient, Kd, was found to be a sensitive parameter of the model. So, we developed an experimental method in order to measure Kd in a dynamic way. We studied four pesticides (atrazine, simazine, lindane, methidathion) and three soils (loam sand, sand loam, calcareous silt loam). The values of Kd obtained were compared to the values measured on the soils by the standardized method of batches and to the values of the literature. Mean Kd measured in the runoff of a rainfall simulation were considerably greater, especially for low suspended particles loads. We ran the model with these different data for Kd and we found that predictions were more accurate with Kd obtained by rainfall simulation particularly for lindane and simazine. We improved the modelisation for atrazine and methidathion. Nevertheless, the relative error between observed and predicted concentrations was not the same according to the pesticide, which made prediction of risk dependent on pesticides classes of behaviour.
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Cheng, Chien Chuan, Re Ching Lin, Wei Tsai Chang, Ying Chung Chen, Kuo Sheng Kao, and Chung Jen Chung. "Electromechanical Coupling Coefficient of SAW on Proton-Exchanged and Annealed LiNbO3 Waveguides." Advanced Materials Research 311-313 (August 2011): 1957–60. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1957.
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We had investigated the electromechanical coupling coefficient (K2) of surface acoustic wave (SAW) on proton-exchanged (PE) and annealed PE (APE) z-cut LiNbO3 waveguides using octanoic acid. The penetration depth of hydrogen assumed to be equal to the waveguide depth (d) was measured by secondary-ion mass spectrometry (SIMS). The frequency response of SAW was measured with a network analyzer. The annealing process was carried out in a horizontal furnace kept at 400°C for 2 h under a dry O2 gas flow. The change of K2 in PE and APE samples fabricated under different conditions was dependent on kd, where k was the wavenumber. The experimental results showed that the variation of K2 in PE samples was significantly decreased with the increase of kd. The reduction of K2 may be due to the reduced piezoelectric coefficients in the PE layer. On the other hand, the variation of K2 in APE samples also exhibited the decreased tendency after annealing. It indicated that the annealing process could not restore the reduction of K2 caused by the PE process.
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Sánchez-Martín, Maria J., and Maria Sáanchez-Camazano. "Adsorption of Chloridazon by Soils and their Components." Weed Science 39, no. 3 (September 1991): 417–22. http://dx.doi.org/10.1017/s0043174500073161.
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The effect of soil composition on adsorption of chloridazon by 18 samples of natural soils, with different chemical and textural characteristics, obtained from west-central Spain, was investigated. The effect of removal of organic matter on adsorption and adsorption of the herbicide by the active components of the soils (montmorillonite and humic acid) was also studied. A highly significant correlation was found between the distribution coefficient (Kd) and organic matter content when all the soils or the soils with organic matter content >2% were considered. According to the determination coefficients (r2), organic matter content accounted for 72% of the variance in adsorption in the former case and 92% in the latter. In soils with an organic matter content <2%, there was no correlation between Kd and organic matter content. A significant correlation was observed between Kd and smectite content for soils containing smectite in their clay fraction. Both simple and multiple correlations showed that clay content, excluding the smectite fraction, had a relatively small effect on adsorption of the herbicide. Adsorption of chloridazon by oxidized soils, montmorillonite, and humic acid confirms the effect of organic matter and smectite on adsorption in natural soils.
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Nababan, B., D. Ulfah, and J. P. Panjaitan. "Light propagation, coefficient attenuation, and the depth of one optical depth in different water types." IOP Conference Series: Earth and Environmental Science 944, no. 1 (December 1, 2021): 012047. http://dx.doi.org/10.1088/1755-1315/944/1/012047.
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Abstract The ocean color satellite can only sense a water column up to one optical depth. However, literatur regarding the depth of one optical depth is very limited to none. This study aimed to determine light propagation, attenuation coefficient (Kd), and the depth of one optical depth in different water types. We used in situ data of downwelling irradiance (Ed) with depths taken using the instrument of submersible marine environmental radiometer (MER) in the northeastern gulf of mexico (NEGOM) in April 2000. We also used SeaWiFS data such as water leaving radience (Lw ), remote sensing refectance (Rrs), and chlorophyll-a concentration (Chla). The results showed that the light propagation pattern generally decreased with increasing depth. The reduction in light intensity with depth was very strong in the red wavelengths, lower in the green wavelengths, and the lowest in the blue wavelengths. In contrast, Kd values were generally found the lowest at the blue wavelengths, slightly increase at the purple and green wavelengths, and the highest at the red wavelengths. The depth of one optical depth in the case-1 waters was found as deep as 39.79 m (λ=475 nm), followed by intermediate water of 31.79 m (λ=475 nm), and in the case-2 waters of 16.08 m (λ=490 nm). Both Kd (490) in situ and modelled results showed a good correlation (r=0.83-0.84) and R2 values of 0.68-0.71.
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Roussel-Debet, S., and K. Beaugelin-Seiller. "Distribution coefficient Kd of transuranics in soils : Experimental determination and consequences for dose assessment." Radioprotection 37, no. C1 (February 2002): C1–297—C1–302. http://dx.doi.org/10.1051/radiopro/2002055.
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Staunton, S. "Sensitivity analysis of the distribution coefficient, Kd, of nickel with changing soil chemical properties." Geoderma 122, no. 2-4 (October 2004): 281–90. http://dx.doi.org/10.1016/j.geoderma.2004.01.014.
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Février, L., A. Martin-Garin, and E. Leclerc. "Variation of the distribution coefficient (Kd) of selenium in soils under various microbial states." Journal of Environmental Radioactivity 97, no. 2-3 (October 2007): 189–205. http://dx.doi.org/10.1016/j.jenvrad.2007.04.005.
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Kumar, Anil, and Avinash Thakur. "Statistical Optimization of Lactic Acid Extraction Using Green Solvent and Mixed Extractants (TOA and TOMAC)." Chemical Engineering Research Bulletin 21, no. 1 (June 4, 2020): 20–35. http://dx.doi.org/10.3329/cerb.v21i1.47369.
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Since some previous years, reactive extraction has become more attractive and competitive technique for the separation and purification of lower carboxylic acids from fermentation broth as well as from dilute aqueous streams. This paper shows the results of investigation of reactive extraction of lactic acid (LA) from an aqueous solution using the synergistic mixture of the extractants (TOA (tri-n-octylamine) and TOMAC (Tri-n-octylmethylammonium chloride)) and a non-toxic and biocompatible green solvent (soybean oil). Three-level Box-Behnken design (BBD) under response surface methodology (RSM) was opted for the experimental design and to interpret the mutual effect of seven independent process parameters on the LA distribution coefficient (KD). The maximum values of LA distribution coefficient (KD=2.51) and its extraction efficiency (ηη=71.5%) were obtained for the optimum values of various process parameters such as 0.02 [M] initial LA concentration (CC1), 0.5 (v/v) extractant ratio (α), 28.66% (v/v) mixed extractants concentration (ψ), 2 (v/v) phase ratio (φ), 270C temperature (T), 102 rpm stirring speed (ω), and 63 mincontact time (τ). This present investigation will provide a noble discussion on LA reactive extraction using green solvent and on various influencing process parameters for gaining the enhanced value of LA distribution coefficient (KD).
Chemical Engineering Research Bulletin 21(2019) 20-35
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Pedroso Curtarelli, Victor, Cláudio Clemente Faria Barbosa, Daniel Andrade Maciel, Rogério Flores Júnior, Felipe Menino Carlos, Evlyn Márcia Leão de Moraes Novo, Marcelo Pedroso Curtarelli, and Edson Filisbino Freire da Silva. "Diffuse Attenuation of Clear Water Tropical Reservoir: A Remote Sensing Semi-Analytical Approach." Remote Sensing 12, no. 17 (September 1, 2020): 2828. http://dx.doi.org/10.3390/rs12172828.
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The diffuse attenuation coefficient of downwelling irradiance (Kd) is an essential parameter for inland waters research by remotely sensing the water transparency. Lately, Kd semi-analytical algorithms substituted the empirical algorithms widely employed. The purpose of this research was to reparametrize a semi-analytical algorithm to estimate Kd and then apply it to a Sentinel-2 MSI time-series (2017–2019) for the Três Marias reservoir, Brazil. The results for the Kd semi-analytical reparametrization achieved good accuracies, reaching mean absolute percentage errors (MAPE) for bands B2, B3 and B4 (492, 560 and 665 nm), lower than 21% when derived from in-situ remote sensing reflectance (Rrs), while for MSI Data, a derived MAPE of 12% and 38% for B2 and B3, respectively. After the application of the algorithm to Sentinel-2 images time-series, seasonal patterns were observed in the results, showing high Kd values at 492 nm during the rainy periods, mainly in the tributary mouths, possibly due to an increase in the surface runoff and inflows and outflow rates in the reservoir watershed.
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Campbell, L. S., A. Chimedtsogzol, and A. Dyer. "Species sensitivity of zeolite minerals for uptake of mercury solutes." Mineralogical Magazine 70, no. 4 (August 2006): 361–71. http://dx.doi.org/10.1180/0026461067040341.
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AbstractThe uptake of inorganic Hg2+ and organometallic CH3Hg+ from aqueous solutions by 11 different natural zeolites has been investigated using a batch distribution coefficient (Kd) method and supported by a preliminary voltammetric study. The effect of mercury concentration on the Kd response is shown over an environmentally appropriate concentration range of 0.1–5 ppm inorganic and organometallic Hg using a batch factor of 100 ml g-1 and 20 h equilibration. Analcime and a Na-chabazite displayed the greatest methylmercury uptakes (Kd values at 1.5 ppm of 4023 and 3456, respectively), with mordenite as the smallest at 578. All uptake responses were greater for methylmercury than for the inorganic mercuric nitrate solutions, suggesting a distinctive sensitivity of zeolites to reaction with different types of solute species. It is likely that this sensitivity is attributable to the precise nature of the resultant Hg-zeolite bonds. Additionally, both the Si-Al ratio and the Na content of the initial natural zeolite samples are shown to influence the Kd responses, with positive correlations between Kd and Na content for all zeolites excluding mordenite.
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Zhang, Pei Cong, Shi Jun Ni, Ke Hui Qiu, Jun Feng Li, Miao Deng, and Yu Chong Qiu. "Impact of Soil Surface Charge Properties on Migration Behavior of Radioactive Uranium, Strontium and Cesium." Advanced Materials Research 781-784 (September 2013): 2215–20. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.2215.
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Static adsorption experiments were conducted to understand the impact of soil surface charge characteristics, such as pH, AEC and CECp values, on migration behavior of radioactive Uranium, Strontium and Cesium. The results demonstrate that distribution coefficient of Uranium (U-Kd value) increases with decreasing initial pH of solution, and increases with increasing AEC values for acidic clay and silty clay that were studied; distribution coefficients of Strontium and Cesium appear to be positively correlated with CECp values of and total contents of montomorillonite and illite in the soil.
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Prasad, D., J. G. Henry, and P. Elefsiniotis. "Nitrogen Removal from Anaerobically Treated Leachate." Water Quality Research Journal 20, no. 1 (February 1, 1985): 138–48. http://dx.doi.org/10.2166/wqrj.1985.012.
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Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of nitrogen by ammonia desorption from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, Kd for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9 , 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120 and 190 cm3/sec/L. Results indicated that nitrogen removal by ammonia desorption from the effluent of anaerobic filters treating leachate was feasible. Removals exceeding 90% were obtained with 8 hours aeration at a pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals for this leachate under various operating conditions.
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Mutavdžić Pavlović, Dragana, Kristina Tolić Čop, Helena Prskalo, and Mislav Runje. "Influence of Organic Matter on the Sorption of Cefdinir, Memantine and Praziquantel on Different Soil and Sediment Samples." Molecules 27, no. 22 (November 18, 2022): 8008. http://dx.doi.org/10.3390/molecules27228008.
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Pharmaceuticals are known for their great effects and applications in the treatment and suppression of various diseases in human and veterinary medicine. The development and modernization of science and technologies have led to a constant increase in the production and consumption of various classes of pharmaceuticals, so they pose a threat to the environment, which can be subjected to the sorption process on the solid phase. The efficiency of sorption is determined by various parameters, of which the physicochemical properties of the compound and the sorbent are very important. One of these parameters that determine pharmaceutical mobility in soil or sediment is the soil–water partition coefficient normalized to organic carbon (Koc), whose determination was the purpose of this study. The influence of organic matter, suspended in an aqueous solution of pharmaceutical (more precisely: cefdinir, memantine, and praziquantel), was studied for five different types of soil and sediment samples from Croatia. The linear, Freundlich, and Dubinin–Raduskevich sorption isotherms were used to determine specific constants such as the partition coefficient Kd, which directly describes the strength of sorbate and sorbent binding. The linear model proved to be the best with the highest correlation coefficients, R2 > 0.99. For all three pharmaceuticals, a positive correlation between sorption affinity described by Kd and Koc and the amount of organic matter was demonstrated.
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Xing, Xiaogang, Emmanuel Boss, Jie Zhang, and Fei Chai. "Evaluation of Ocean Color Remote Sensing Algorithms for Diffuse Attenuation Coefficients and Optical Depths with Data Collected on BGC-Argo Floats." Remote Sensing 12, no. 15 (July 23, 2020): 2367. http://dx.doi.org/10.3390/rs12152367.
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The vertical distribution of irradiance in the ocean is a key input to quantify processes spanning from radiative warming, photosynthesis to photo-oxidation. Here we use a novel dataset of thousands local-noon downwelling irradiance at 490 nm (Ed(490)) and photosynthetically available radiation (PAR) profiles captured by 103 BGC-Argo floats spanning three years (from October 2012 to January 2016) in the world’s ocean, to evaluate several published algorithms and satellite products related to diffuse attenuation coefficient (Kd). Our results show: (1) MODIS-Aqua Kd(490) products derived from a blue-to-green algorithm and two semi-analytical algorithms show good consistency with the float-observed values, but the Chla-based one has overestimation in oligotrophic waters; (2) The Kd(PAR) model based on the Inherent Optical Properties (IOPs) performs well not only at sea-surface but also at depth, except for the oligotrophic waters where Kd(PAR) is underestimated below two penetration depth (2zpd), due to the model’s assumption of a homogeneous distribution of IOPs in the water column which is not true in most oligotrophic waters with deep chlorophyll-a maxima; (3) In addition, published algorithms for the 1% euphotic-layer depth and the depth of 0.415 mol photons m−2 d−1 isolume are evaluated. Algorithms based on Chla generally work well while IOPs-based ones exhibit an overestimation issue in stratified and oligotrophic waters, due to the underestimation of Kd(PAR) at depth.
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Ouyang, Shuang Long, Shu Zhan Li, Shu Kui Zhou, Hua Li, Hai Hao Jiang, and Wen Jing Deng. "Numerical Simulation on U(VI) in Uranium Tailing Impoundment Affected by Acid Rain." Advanced Materials Research 986-987 (July 2014): 713–18. http://dx.doi.org/10.4028/www.scientific.net/amr.986-987.713.
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As acid rain getting more and more serious, increasing attention is given to environmental effect assessment of uranium tailings under the condition of acid rain. In the paper, influence of acid rain to partitioning coefficient (Kd) of U(VI) in soil was studied, and migration of radionuclide uranium in soil was simulated by computer. The static experiment results showed that the Kd value of U(VI) in soil reaches minimum value when pH is 2.0. When 2.0<pH<3.5, the Kd showed a rising tendency;The Kd in soil reaches maximum value when pH is 3.5. And when 3.5<pH<8.0, the Kd showed a decreasing tendency. This paper has taken a large uranium tailings impoundment in South China as an example studied by VisualModflow. After setting up models of groundwater movement and radionuclide migration in the study area, migration tendency of radionuclide U(VI) was simulated and pollution of radionuclide to environment was predicted. The results of simulation show that the migration of uranium speed to be the slowest when pH = 2.0, and the figure to be the fastest when pH = 3.5. Furthermore, maximum speed is about 1.24 times of minimum speed.