The study was to investigate the adsorption behavior of arsenite (As(HI)) and arsenate (As(V)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with b...The study was to investigate the adsorption behavior of arsenite (As(HI)) and arsenate (As(V)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As(HI) adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As(Ⅲ) was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As(Ⅴ) adsorption-pH curves at different ionic strengths (a characteristic pH) are obtained for both soils. It was noted that above this pH, the adsorption of As(Ⅴ) was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE (soil point of zero salt effect) of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils.展开更多
In this study, biochars from rice straw(Oryza sativa L.) were prepared at 200–600?C by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and ...In this study, biochars from rice straw(Oryza sativa L.) were prepared at 200–600?C by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and to examine the adsorption capacities of the biochars for a heavy metal, copper(Ⅱ)(Cu(Ⅱ)), and an organic insecticide of cyromazine, as well as to further reveal the adsorption mechanisms.The results obtained with batch experiments showed that the amount of Cu(Ⅱ) adsorbed varied with the pyrolysis temperatures of rice straw biochar. The biochar produced at 400?C had the largest adsorption capacity for Cu(Ⅱ)(0.37 mol kg-1) among the biochars,with the non-electrostatic adsorption as the main adsorption mechanism. The highest adsorption capacity for cyromazine(156.42 g kg-1) was found in the rice straw biochar produced at 600?C, and cyromazine adsorption was exclusively predominated by surface adsorption. An obvious competitive adsorption was found between 5 mmol L-1Cu(II) and 2 g L-1cyromazine when they were in the binary solute system. Biochar may be used to remediate heavy metal- and organic insecticide-contaminated water, while the pyrolysis temperature of feedstocks for producing biochar should be considered for the restoration of multi-contamination.展开更多
Cultivated tea(Camellia sinensis) plants acidify the rhizosphere, and Aluminum(Al) toxicity is recognized as a major limiting factor for plant growth in acidic soils. However, the mechanisms responsible for rhizospher...Cultivated tea(Camellia sinensis) plants acidify the rhizosphere, and Aluminum(Al) toxicity is recognized as a major limiting factor for plant growth in acidic soils. However, the mechanisms responsible for rhizosphere acidification associated with Al have not been fully elucidated. The present study examined the effect of Al on root-induced rhizosphere acidification, plasma membrane H^+-adenosine triphosphatase(H^+-ATPase) activity, and cation-anion balance in tea plant roots. The exudation of H^+from tea plant roots with or without Al treatment was visualized using an agar sheet with bromocresol purple. The H^+-ATPase activity of plasma membranes isolated from the roots was measured after hydrolysis using the two-phase partition system. The Al treatment strongly enhanced the exudation of H^+, and the acidification of tea plant roots by Al was closely associated with plasma membrane H^+-ATPase activity. The root plasma membrane H^+-ATPase activity increased with Al concentration. The Al content, amount of protons released, and H^+-ATPase activity were significantly higher in roots treated with Al than in those untreated. The results of the cation-anion balance in roots showed an excess of cations relative to anions, with the amount of excess cation uptake increasing with increasing Al concentrations. These suggest that Al-enhanced proton release is associated with plasma membrane H^+-ATPase activity and excess cation uptake. Findings of this study would provide insights into the contributing factors of soil acidification in tea plantations.展开更多
Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investiga...Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investigated to determine the main factors that affect their distribution and relationship with Mn(Ⅱ)plant toxicity.Fresh soybean roots were reacted with Mn(Ⅱ)in solutions,and Mn(Ⅱ)adsorbed on the roots was differentiated into exchangeable,complexed,and precipitated forms through sequential extraction with KNO3,EDTA,and HCl.The exchangeable Mn(Ⅱ)content on the roots was the highest,followed by the complexed and precipitated Mn(Ⅱ)contents.Mn(Ⅱ)toxicity to the roots was greater at pH 5.5 than at pH 4.2 due to the larger amount of exchangeable Mn(Ⅱ)at higher pH.The cations Al3+,La3+,Ca2+,Mg2+,and NH4+competed with Mn(Ⅱ)for cation exchange sites on the root surfaces and thus reduced exchangeable Mn(Ⅱ)on the roots,in the order Al3+,La3+>Ca2+,Mg2+>NH4+.Al3+ and La3+ at 100μmol L-1 decreased exchangeable Mn(Ⅱ)by 80%and 79%,respectively,and Ca2+ and Mg2+at 1 mmol L-1 decreased exchangeable Mn(Ⅱ)by 51%and 73%,respectively.Organic anions oxalate,citrate,and malate reduced free Mn(Ⅱ)concentration in solution through formation of complexes with Mn(Ⅱ),efficiently decreasing exchangeable Mn(Ⅱ)on the roots;the decreases in exchangeable Mn(Ⅱ)on the roots were 30.9%,19.7%,and 10.9%,respectively,which was consistent with the complexing ability of these organic anions with Mn(Ⅱ).Thus,exchangeable Mn(Ⅱ)was the dominant form of Mn(Ⅱ)on the roots and responsible for Mn(Ⅱ)toxicity to plants.The coexisting cations and organic anions reduced the exchangeable Mn(Ⅱ)content,and thus they could alleviate Mn(Ⅱ)toxicity to plants on acid soils.展开更多
基金supported by the Knowledge Innovation Program Foundation of the Chinese Academy of Sciences (No. KZCX2-YW-409)the National Natural Science Foundation of China (No. 20577054)
文摘The study was to investigate the adsorption behavior of arsenite (As(HI)) and arsenate (As(V)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As(HI) adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As(Ⅲ) was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As(Ⅴ) adsorption-pH curves at different ionic strengths (a characteristic pH) are obtained for both soils. It was noted that above this pH, the adsorption of As(Ⅴ) was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE (soil point of zero salt effect) of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils.
基金supported by the National Natural Science Foundation of China (Nos.41371245 and 41230855)the National Key Technology R&D Program of China (No.2012BAJ24B06)
文摘In this study, biochars from rice straw(Oryza sativa L.) were prepared at 200–600?C by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and to examine the adsorption capacities of the biochars for a heavy metal, copper(Ⅱ)(Cu(Ⅱ)), and an organic insecticide of cyromazine, as well as to further reveal the adsorption mechanisms.The results obtained with batch experiments showed that the amount of Cu(Ⅱ) adsorbed varied with the pyrolysis temperatures of rice straw biochar. The biochar produced at 400?C had the largest adsorption capacity for Cu(Ⅱ)(0.37 mol kg-1) among the biochars,with the non-electrostatic adsorption as the main adsorption mechanism. The highest adsorption capacity for cyromazine(156.42 g kg-1) was found in the rice straw biochar produced at 600?C, and cyromazine adsorption was exclusively predominated by surface adsorption. An obvious competitive adsorption was found between 5 mmol L-1Cu(II) and 2 g L-1cyromazine when they were in the binary solute system. Biochar may be used to remediate heavy metal- and organic insecticide-contaminated water, while the pyrolysis temperature of feedstocks for producing biochar should be considered for the restoration of multi-contamination.
基金supported by the National Natural Science Foundation of China (Nos. 31600558 and 31400587)the Natural Science Foundation of Jiangsu, China (No. BK20160590)+1 种基金the Earmarked Fund for Modern Agro-industry Technology Research System of China (No. CARS-19)the Agricultural Science and Technology Innovation Fund of Jiangsu, China (No. CX(13)5016)
文摘Cultivated tea(Camellia sinensis) plants acidify the rhizosphere, and Aluminum(Al) toxicity is recognized as a major limiting factor for plant growth in acidic soils. However, the mechanisms responsible for rhizosphere acidification associated with Al have not been fully elucidated. The present study examined the effect of Al on root-induced rhizosphere acidification, plasma membrane H^+-adenosine triphosphatase(H^+-ATPase) activity, and cation-anion balance in tea plant roots. The exudation of H^+from tea plant roots with or without Al treatment was visualized using an agar sheet with bromocresol purple. The H^+-ATPase activity of plasma membranes isolated from the roots was measured after hydrolysis using the two-phase partition system. The Al treatment strongly enhanced the exudation of H^+, and the acidification of tea plant roots by Al was closely associated with plasma membrane H^+-ATPase activity. The root plasma membrane H^+-ATPase activity increased with Al concentration. The Al content, amount of protons released, and H^+-ATPase activity were significantly higher in roots treated with Al than in those untreated. The results of the cation-anion balance in roots showed an excess of cations relative to anions, with the amount of excess cation uptake increasing with increasing Al concentrations. These suggest that Al-enhanced proton release is associated with plasma membrane H^+-ATPase activity and excess cation uptake. Findings of this study would provide insights into the contributing factors of soil acidification in tea plantations.
基金supported by the National Natural Science Foundation of China (No. 41230855)
文摘Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investigated to determine the main factors that affect their distribution and relationship with Mn(Ⅱ)plant toxicity.Fresh soybean roots were reacted with Mn(Ⅱ)in solutions,and Mn(Ⅱ)adsorbed on the roots was differentiated into exchangeable,complexed,and precipitated forms through sequential extraction with KNO3,EDTA,and HCl.The exchangeable Mn(Ⅱ)content on the roots was the highest,followed by the complexed and precipitated Mn(Ⅱ)contents.Mn(Ⅱ)toxicity to the roots was greater at pH 5.5 than at pH 4.2 due to the larger amount of exchangeable Mn(Ⅱ)at higher pH.The cations Al3+,La3+,Ca2+,Mg2+,and NH4+competed with Mn(Ⅱ)for cation exchange sites on the root surfaces and thus reduced exchangeable Mn(Ⅱ)on the roots,in the order Al3+,La3+>Ca2+,Mg2+>NH4+.Al3+ and La3+ at 100μmol L-1 decreased exchangeable Mn(Ⅱ)by 80%and 79%,respectively,and Ca2+ and Mg2+at 1 mmol L-1 decreased exchangeable Mn(Ⅱ)by 51%and 73%,respectively.Organic anions oxalate,citrate,and malate reduced free Mn(Ⅱ)concentration in solution through formation of complexes with Mn(Ⅱ),efficiently decreasing exchangeable Mn(Ⅱ)on the roots;the decreases in exchangeable Mn(Ⅱ)on the roots were 30.9%,19.7%,and 10.9%,respectively,which was consistent with the complexing ability of these organic anions with Mn(Ⅱ).Thus,exchangeable Mn(Ⅱ)was the dominant form of Mn(Ⅱ)on the roots and responsible for Mn(Ⅱ)toxicity to plants.The coexisting cations and organic anions reduced the exchangeable Mn(Ⅱ)content,and thus they could alleviate Mn(Ⅱ)toxicity to plants on acid soils.