Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequen...Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.展开更多
An accurate mathematical representation of soil particle-size distribution(PSD) is required to estimate soil hydraulic properties or to compare texture measurements using different classification systems. However, man...An accurate mathematical representation of soil particle-size distribution(PSD) is required to estimate soil hydraulic properties or to compare texture measurements using different classification systems. However, many databases do not contain full PSD data,but instead contain only the clay, silt, and sand mass fractions. The objective of this study was to evaluate the abilities of four PSD models(the Skaggs model, the Fooladmand model, the modified Gray model GM(1,1), and the Fredlund model) to predict detailed PSD using limited soil textural data and to determine the effects of soil texture on the performance of the individual PSD model.The mean absolute error(MAE) and root mean square error(RMSE) were used to measure the goodness-of-fit of the models, and the Akaike's information criterion(AIC) was used to compare the quality of model fits. The performance of all PSD models except the GM(1,1) improved with increasing clay content in soils. This result showed that the GM(1,1) was less dependent on soil texture.The Fredlund model was the best for describing the PSDs of all soil textures except in the sand textural class. However, the GM(1,1) showed better performance as the sand content increased. These results indicated that the Fredlund model showed the best performance and the least values of all evaluation criteria, and can be used using limited soil textural data for detailed PSD.展开更多
Twenty-eight surface soil samples from 5 functional zones （park, traffic roadside, business/residential area, rural area, and industrial area） of Uruimqi, China were collected and analyzed for the concentrations of ...Twenty-eight surface soil samples from 5 functional zones （park, traffic roadside, business/residential area, rural area, and industrial area） of Uruimqi, China were collected and analyzed for the concentrations of 14 organochlorine pesticides （OCPs）, such as 3 isomers of hexachlorocyclohexane （HCHs） （α-HCH, β-HCH, and γ-HCH）, 4 dichlorodiphenyltrichloroethanes （DDTs） （p,p′-DDT and its metabolites p, p′-DDD （1,1-dichloro-2,2-bis（p-chlorophenyl）ethane） and p,p′-DDE （1,1-dichloro-2,2-bis（4-chorophenyl）ethylene）, and o, p′-DDT）, and methoxychlor, aiming to survey the residue levels and compositions of these 14 OCPs, to identify possible sources of the OCPs, and to assess their potential risks to human health and the environment in surface soils of Ur/imqi. The concentrations ranged from non-detected to 30.86μg kg^-1 for HCHs （sum of α-, β-, and γ-HCH）, from non-detected to 40.03 μg kg^-1 for DDTs （sum of p, p′-DDT, p, p′-DDD, p, p′-DDE, and o, p′-DDT）, and from non-detected to 11.95 μg kg^-1 for methoxychlor. The total concentrations of the OCPs ranged from 16.40 to 84.86 μg kg^-1, with a mean of 41.89 ± 16.25 μg kg^-1. According to the measured concentrations and occurrence rates of the 14 OCPs, DDTs, HCHs, and methoxychlor were the most dominant compounds. Among the 5 functional zones, the total concentration of OCPs was in the order of rural area 〉 traffic roadside 〉 park 〉 business/residential area 〉 industrial area. The different compositions of DDTs and HCHs indicated that the residues of these compounds in most soil samples originated from historical application, besides slight recent introduction at some sampling sites. The results of Pearson correlation analysis showed that soil total organic carbon played an important role in the residue levels of HCHs, but such relationships were not found with DDTs or other OCPs. The soil quality of Uriimqi was classified as Class I based on the guidelines of the Chinese Environmental Quality Standard for Soil （GB15618-1995）, indicating that the residue levels of OCPs have little risks to the environment and human health in the study area.展开更多
文摘Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.
基金supported by the Rice Research Institute, Rasht of Iran
文摘An accurate mathematical representation of soil particle-size distribution(PSD) is required to estimate soil hydraulic properties or to compare texture measurements using different classification systems. However, many databases do not contain full PSD data,but instead contain only the clay, silt, and sand mass fractions. The objective of this study was to evaluate the abilities of four PSD models(the Skaggs model, the Fooladmand model, the modified Gray model GM(1,1), and the Fredlund model) to predict detailed PSD using limited soil textural data and to determine the effects of soil texture on the performance of the individual PSD model.The mean absolute error(MAE) and root mean square error(RMSE) were used to measure the goodness-of-fit of the models, and the Akaike's information criterion(AIC) was used to compare the quality of model fits. The performance of all PSD models except the GM(1,1) improved with increasing clay content in soils. This result showed that the GM(1,1) was less dependent on soil texture.The Fredlund model was the best for describing the PSDs of all soil textures except in the sand textural class. However, the GM(1,1) showed better performance as the sand content increased. These results indicated that the Fredlund model showed the best performance and the least values of all evaluation criteria, and can be used using limited soil textural data for detailed PSD.
基金supported by the National Natural Science Foundation of China (No. 41101482)the Natural Science Foundation of Beijing, China (No. 8122021)
文摘Twenty-eight surface soil samples from 5 functional zones （park, traffic roadside, business/residential area, rural area, and industrial area） of Uruimqi, China were collected and analyzed for the concentrations of 14 organochlorine pesticides （OCPs）, such as 3 isomers of hexachlorocyclohexane （HCHs） （α-HCH, β-HCH, and γ-HCH）, 4 dichlorodiphenyltrichloroethanes （DDTs） （p,p′-DDT and its metabolites p, p′-DDD （1,1-dichloro-2,2-bis（p-chlorophenyl）ethane） and p,p′-DDE （1,1-dichloro-2,2-bis（4-chorophenyl）ethylene）, and o, p′-DDT）, and methoxychlor, aiming to survey the residue levels and compositions of these 14 OCPs, to identify possible sources of the OCPs, and to assess their potential risks to human health and the environment in surface soils of Ur/imqi. The concentrations ranged from non-detected to 30.86μg kg^-1 for HCHs （sum of α-, β-, and γ-HCH）, from non-detected to 40.03 μg kg^-1 for DDTs （sum of p, p′-DDT, p, p′-DDD, p, p′-DDE, and o, p′-DDT）, and from non-detected to 11.95 μg kg^-1 for methoxychlor. The total concentrations of the OCPs ranged from 16.40 to 84.86 μg kg^-1, with a mean of 41.89 ± 16.25 μg kg^-1. According to the measured concentrations and occurrence rates of the 14 OCPs, DDTs, HCHs, and methoxychlor were the most dominant compounds. Among the 5 functional zones, the total concentration of OCPs was in the order of rural area 〉 traffic roadside 〉 park 〉 business/residential area 〉 industrial area. The different compositions of DDTs and HCHs indicated that the residues of these compounds in most soil samples originated from historical application, besides slight recent introduction at some sampling sites. The results of Pearson correlation analysis showed that soil total organic carbon played an important role in the residue levels of HCHs, but such relationships were not found with DDTs or other OCPs. The soil quality of Uriimqi was classified as Class I based on the guidelines of the Chinese Environmental Quality Standard for Soil （GB15618-1995）, indicating that the residue levels of OCPs have little risks to the environment and human health in the study area.
