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
Sequential extraction is used effectively to determine the chemical forms of heavy metals. Since few studies have been conducted in calcareous soils of Iran, the current research has been carried out to evaluate the e...Sequential extraction is used effectively to determine the chemical forms of heavy metals. Since few studies have been conducted in calcareous soils of Iran, the current research has been carried out to evaluate the effect of moisture regimes and incubation time on the chemical forms of cadmium in two calcareous soils. Treatments included three levels of cadmium (0, 30 and 60 mg/kg of soil as CdSo4), three incubation times (2, 4 and 8 weeks), two soils (clay and sandy clay loam) and two moisture regimes (Water-logged and Field capacity). The experiment was performed as factorial on the basis of randomized complete blocks design with two replications. At 2, 4, and 8 weeks after treatment, the Tessier et al. (1979) sequential extraction method was applied to measure the cadmium concentration in water soluble-exchangeable (WsEx.), iron and manganese oxide (Fe-MnOx.), carbonate (Car.), organic matter (Om.) and residual forms (Res.). The results showed depending on the soil texture, 68 to 72 percent of the cadmium was in water soluble-exchangeable and iron-manganese oxide forms. Flooding condition decreased the concentration of cadmium in water soluble + exchangeable form and increased the concentration of cadmium in the forms of Fe-Mn oxides, carbonate and organic matter. Concentration of cadmium in residual form was higher in clay soil. In sandy clay loam soil, water soluble-exchangeable, carbonate and organic matter forms were higher than clay soil. The iron-manganese oxides form showed no significant difference in two soils at field capacity regime. In flooding conditions, the concentration of the water soluble-exchangeable form decreased and the concentration of other forms increased. In contrast to the oxidizing conditions at the reduction conditions, no significant difference was observed in the residual and organic matter forms in two soils.展开更多
A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not on...A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.展开更多
Sequential extraction method was used to analyze and distinguish various chemical bound forms of copper and zine in rape and wheat.The results show that in these two crops,copper was mainly in the form of wate soluble...Sequential extraction method was used to analyze and distinguish various chemical bound forms of copper and zine in rape and wheat.The results show that in these two crops,copper was mainly in the form of wate soluble and ethanol soluble, which can be easily transferred in crops.The total content of various chemical bound forms of copper was higher in aboveground part than in underground part,and their content was decreased in the order of water soluble form(W.S.form)>residual form (Re.form)>ethanol soluble form(Eth.S.form)>acid soluble form (A.S.form). Zinc was mainly in the form of acid soluble, which is hard to be transferred in crops.The total content of various chemical bound forms of zinc was lower in aboveground part than in roots, and their content was decreased in the order of A.S.form>Re.form>W.S.form>Eth.S.form.In comparing with copper,a large amount of zinc was enriched in seeds and pods of rape.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.
文摘Sequential extraction is used effectively to determine the chemical forms of heavy metals. Since few studies have been conducted in calcareous soils of Iran, the current research has been carried out to evaluate the effect of moisture regimes and incubation time on the chemical forms of cadmium in two calcareous soils. Treatments included three levels of cadmium (0, 30 and 60 mg/kg of soil as CdSo4), three incubation times (2, 4 and 8 weeks), two soils (clay and sandy clay loam) and two moisture regimes (Water-logged and Field capacity). The experiment was performed as factorial on the basis of randomized complete blocks design with two replications. At 2, 4, and 8 weeks after treatment, the Tessier et al. (1979) sequential extraction method was applied to measure the cadmium concentration in water soluble-exchangeable (WsEx.), iron and manganese oxide (Fe-MnOx.), carbonate (Car.), organic matter (Om.) and residual forms (Res.). The results showed depending on the soil texture, 68 to 72 percent of the cadmium was in water soluble-exchangeable and iron-manganese oxide forms. Flooding condition decreased the concentration of cadmium in water soluble + exchangeable form and increased the concentration of cadmium in the forms of Fe-Mn oxides, carbonate and organic matter. Concentration of cadmium in residual form was higher in clay soil. In sandy clay loam soil, water soluble-exchangeable, carbonate and organic matter forms were higher than clay soil. The iron-manganese oxides form showed no significant difference in two soils at field capacity regime. In flooding conditions, the concentration of the water soluble-exchangeable form decreased and the concentration of other forms increased. In contrast to the oxidizing conditions at the reduction conditions, no significant difference was observed in the residual and organic matter forms in two soils.
基金supported by the National Natural Science Foundation of China (No. 51376109)
文摘A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.
文摘Sequential extraction method was used to analyze and distinguish various chemical bound forms of copper and zine in rape and wheat.The results show that in these two crops,copper was mainly in the form of wate soluble and ethanol soluble, which can be easily transferred in crops.The total content of various chemical bound forms of copper was higher in aboveground part than in underground part,and their content was decreased in the order of water soluble form(W.S.form)>residual form (Re.form)>ethanol soluble form(Eth.S.form)>acid soluble form (A.S.form). Zinc was mainly in the form of acid soluble, which is hard to be transferred in crops.The total content of various chemical bound forms of zinc was lower in aboveground part than in roots, and their content was decreased in the order of A.S.form>Re.form>W.S.form>Eth.S.form.In comparing with copper,a large amount of zinc was enriched in seeds and pods of rape.
