The combined pollution of heavy metal Pb^2＋ and bensulfuron-methyl （BSM）, originating from chemical herbicides, in agroecological environments has become commonplace in southern China. The adsorption of BSM on thre...The combined pollution of heavy metal Pb^2＋ and bensulfuron-methyl （BSM）, originating from chemical herbicides, in agroecological environments has become commonplace in southern China. The adsorption of BSM on three paddy soils in the presence of Pb^2＋ was examined using high-performance liquid chromatograph （HPLC）. Results indicated that adsorption of BSM could accurately be described by a Freundlich isotherm equation with correlation constant （R） 〉 0.98, irrespective of the presence of spiked Pb^2＋. Of the various factors influencing BSM sorption, soil pH appeared to be the most influential. The constant Kf of Freundlich isotherm equation tended to increase with increasing Pb^2＋ concentration in soil which indicated that the spiked of Pb^2＋ in paddy soils would promote the sorption of BSM. AGo of BSM in three paddy soils was less than 40 kJ/mol in all treatments, indicating the adsorption of BSM is mainly physical in nature. The elution of soil dissolved organic matter （DOM） enhanced the adsorption of BSM in paddy soils. The mechanisms involved in the promotion effects of the spiked Pb^2＋ on BSM adsorption might be the modified surface characteristics of paddy soil solids due to the soil acidification and the increase of soil organic matter concentration because of DOM binding.展开更多
The water-level fluctuation zone(WLFZ) has been considered as a hotspot for mercury(Hg) methylation. Flooding-tolerant herbs are gradually acclimated to this water-land ecotone, tending to form substantial root system...The water-level fluctuation zone(WLFZ) has been considered as a hotspot for mercury(Hg) methylation. Flooding-tolerant herbs are gradually acclimated to this water-land ecotone, tending to form substantial root systems for improving erosion resistance. Accompanying rhizosphere microzone plays crucial but unclear roles in methylmercury(Me Hg) formation in the WLFZ. Thus, we conducted this study in the WLFZ of the Three Gorges Reservoir, to explore effects of the rhizosphere of a dominant flooding-tolerant herb(bermudagrass) on Me Hg production. The elevated Hg and Me Hg in rhizosphere soils suggest that the rhizosphere environment provides favorable conditions for Hg accumulation and methylation. The increased bioavailable Hg and microbial activity in the rhizosphere probably serve as important factors driving Me Hg formation in the presence of bermudagrass. Simultaneously, the rhizosphere environments changed the richness, diversity, and distribution of hgc A-containing microorganisms. Here, a typical ironreducing bacterium( Geobacteraceae) has been screened, however, the majority of hgc A genes detected in rhizosphere, near-, and non-rhizosphere soils of the WLFZ were unclassified. Collectively, these results provide new insights into the elevated Me Hg production as related to microbial processes in the rhizosphere of perennial herbs in the WLFZ, with general implications for Hg cycling in other ecosystems with water-level fluctuations.展开更多
Methylmercury （MeHg） is an organic form of the global pollutant mercury （Hg） which readily accumulates in fish tissue. A majority of Hg methylation is a result of microbial activity and the abundance of inorganic ...Methylmercury （MeHg） is an organic form of the global pollutant mercury （Hg） which readily accumulates in fish tissue. A majority of Hg methylation is a result of microbial activity and the abundance of inorganic Hg within the water reservoirs （Eckley et al., 2017）. Compared to natural lakes and rivers, reservoirs have elevated Hg levels from the decompo- sition of recently flooded organic material which promote Hg release and enhance microbial methylation of Hg （Eckley et al., 2017）. Microorganisms containing the gene clusters hgcA and hgcB, such as sulfate reducing bacteria （SRB） and iron reducing bacteria （FeRB）.展开更多
Effects of nitrogen-containing biodegradation enhancers(methyl diethanolamine oleate(MDEAO) and oleic diethanolamide(ODEA)) on the adsorption of n-hexadecane in soil were studied by laboratory batch experiments. The p...Effects of nitrogen-containing biodegradation enhancers(methyl diethanolamine oleate(MDEAO) and oleic diethanolamide(ODEA)) on the adsorption of n-hexadecane in soil were studied by laboratory batch experiments. The partition coefficients(K_d values) of n-hexadecane sorption in soil-water system and those partition coefficients normalized to organic matter(K_(oc) values) were both determined. The adsorption isotherm curve of n-hexadecane in soil-water system was plotted. The measured results demonstrated that K_(oc) values changed in the soil-water system with different enhancers but are relatively invariant for the soil at the same site. The K_d values rose with the increase of the organic matter content in different soil. The average values of K_(oc) in the soil-water system with MDEAO, ODEA,and blank soil were 0.412, 0.252,and 0.309, respectively. The critical micelle concentration of ODEA and MDEAO was 0.7 mg/L and 1.9 mg/L, respectively,denoting that the solubilization capacity of ODEA was much stronger than MDEAO in the soil-water system. Consequently,the adsorption of MDEAO onto the solid surface increased the organic matter content in soil,which could make it more effective in enhancing the n-hexadecane adsorption. On the contrary, ODEA could inhibit the adsorption of n-hexadecane because of its less adsorption rate onto the soil particle surface and higher concentration in the soil-water system. According to the correlation coefficients, it was found that both the Henry linear and the Freundlich nonlinear isotherm sorption models were fitted to the data very well, however the Freundlich model was better than the Henry model.展开更多
Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and processes.In this study,PSD ...Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and processes.In this study,PSD of three clayey soils collected from the topsoil(0-20 cm) of Vertisols in Northern China was analyzed using the N_2 adsorption(NA) and mercury intrusion porosimetry(MIP) methods.The effect of soil organic matter(SOM) on the PSD of clayey soils was also evaluated.The differential curves of pore volume of clayey soils by the NA method exhibited that the pores with diameter < 0.01 μm accounted for more than 50%in the pore size range of 0.001 to 0.1 μm.The differential pore curves of clayey soils by the MIP method exhibited three distinct peaks in pore size range of 60 to 100,0.3 to 0.4 and 0.009 to 0.012 μm,respectively.In the three clayey soils,the ultramicropores(5-0.1μm) were determined to be the main pore class(on average 35.5%),followed by macropores(> 75 μm,31.4%),cryptopores(0.1-0.007μm,16.0%),micropores(30-5 μm,9.7%) and mesopores(75-30 μm,7.3%).The SOM greatly affected the pore structure and PSD of aggregates in clayey soils.In particular,SOM removal reduced the volume and porosity of 5-100 μm pores while increased those of <5 μm pores in the 5-2 and 2-0.25 mm aggregates of clayey soils.The increase in the volume and porosity of < 5 μm pores may be attributed to the disaggregation and partial emptying of small pores caused by the destruction of SOM.展开更多
This paper studies the characteristics and mechanism of the adsorption of methylence blue from aqueous solution by humic acid which was extracted from swampy soil in Zhongdian of Yunnan in two methods.The result shows...This paper studies the characteristics and mechanism of the adsorption of methylence blue from aqueous solution by humic acid which was extracted from swampy soil in Zhongdian of Yunnan in two methods.The result shows that the adsorption could fit the langmuir model.Humic acids extracted in two methods has the similar pattern of adsorption,but the Humic acid by sodium pyrophosphate has better adsorption because of its bigger specific surface area.The adsorptive constant and thermodynamic parameters have been evaluated in different temperatures.Furthermore the mechanism of adsorption on the humic acid has been discussed.展开更多
基金supported by the National Nature Science Foundation for Distinguished Young Scholars of China(No. 40425007)the National Natural Science Founda-tion of China (No. 40371062, 40771100)the Natural Science Foundation of Zhejiang Province (No. Y5080180)
文摘The combined pollution of heavy metal Pb^2＋ and bensulfuron-methyl （BSM）, originating from chemical herbicides, in agroecological environments has become commonplace in southern China. The adsorption of BSM on three paddy soils in the presence of Pb^2＋ was examined using high-performance liquid chromatograph （HPLC）. Results indicated that adsorption of BSM could accurately be described by a Freundlich isotherm equation with correlation constant （R） 〉 0.98, irrespective of the presence of spiked Pb^2＋. Of the various factors influencing BSM sorption, soil pH appeared to be the most influential. The constant Kf of Freundlich isotherm equation tended to increase with increasing Pb^2＋ concentration in soil which indicated that the spiked of Pb^2＋ in paddy soils would promote the sorption of BSM. AGo of BSM in three paddy soils was less than 40 kJ/mol in all treatments, indicating the adsorption of BSM is mainly physical in nature. The elution of soil dissolved organic matter （DOM） enhanced the adsorption of BSM in paddy soils. The mechanisms involved in the promotion effects of the spiked Pb^2＋ on BSM adsorption might be the modified surface characteristics of paddy soil solids due to the soil acidification and the increase of soil organic matter concentration because of DOM binding.
基金the funding support from the National Natural Science Foundation of China (No. 41877384 )the Fundamental Research Funds for the Central Universities (No. XDJK2017B035 )Chongqing Graduate Scientific Research Innovation Project (No. CYS21112 ) for its support。
文摘The water-level fluctuation zone(WLFZ) has been considered as a hotspot for mercury(Hg) methylation. Flooding-tolerant herbs are gradually acclimated to this water-land ecotone, tending to form substantial root systems for improving erosion resistance. Accompanying rhizosphere microzone plays crucial but unclear roles in methylmercury(Me Hg) formation in the WLFZ. Thus, we conducted this study in the WLFZ of the Three Gorges Reservoir, to explore effects of the rhizosphere of a dominant flooding-tolerant herb(bermudagrass) on Me Hg production. The elevated Hg and Me Hg in rhizosphere soils suggest that the rhizosphere environment provides favorable conditions for Hg accumulation and methylation. The increased bioavailable Hg and microbial activity in the rhizosphere probably serve as important factors driving Me Hg formation in the presence of bermudagrass. Simultaneously, the rhizosphere environments changed the richness, diversity, and distribution of hgc A-containing microorganisms. Here, a typical ironreducing bacterium( Geobacteraceae) has been screened, however, the majority of hgc A genes detected in rhizosphere, near-, and non-rhizosphere soils of the WLFZ were unclassified. Collectively, these results provide new insights into the elevated Me Hg production as related to microbial processes in the rhizosphere of perennial herbs in the WLFZ, with general implications for Hg cycling in other ecosystems with water-level fluctuations.
文摘Methylmercury （MeHg） is an organic form of the global pollutant mercury （Hg） which readily accumulates in fish tissue. A majority of Hg methylation is a result of microbial activity and the abundance of inorganic Hg within the water reservoirs （Eckley et al., 2017）. Compared to natural lakes and rivers, reservoirs have elevated Hg levels from the decompo- sition of recently flooded organic material which promote Hg release and enhance microbial methylation of Hg （Eckley et al., 2017）. Microorganisms containing the gene clusters hgcA and hgcB, such as sulfate reducing bacteria （SRB） and iron reducing bacteria （FeRB）.
基金the financial support of the Science Foundation for Post-doctoral Researchers, Chongqing, China (project No. Xm2016078)the Natural Science Foundation of Chongqing (project No.CSTC2017jcyjAX0058)
文摘Effects of nitrogen-containing biodegradation enhancers(methyl diethanolamine oleate(MDEAO) and oleic diethanolamide(ODEA)) on the adsorption of n-hexadecane in soil were studied by laboratory batch experiments. The partition coefficients(K_d values) of n-hexadecane sorption in soil-water system and those partition coefficients normalized to organic matter(K_(oc) values) were both determined. The adsorption isotherm curve of n-hexadecane in soil-water system was plotted. The measured results demonstrated that K_(oc) values changed in the soil-water system with different enhancers but are relatively invariant for the soil at the same site. The K_d values rose with the increase of the organic matter content in different soil. The average values of K_(oc) in the soil-water system with MDEAO, ODEA,and blank soil were 0.412, 0.252,and 0.309, respectively. The critical micelle concentration of ODEA and MDEAO was 0.7 mg/L and 1.9 mg/L, respectively,denoting that the solubilization capacity of ODEA was much stronger than MDEAO in the soil-water system. Consequently,the adsorption of MDEAO onto the solid surface increased the organic matter content in soil,which could make it more effective in enhancing the n-hexadecane adsorption. On the contrary, ODEA could inhibit the adsorption of n-hexadecane because of its less adsorption rate onto the soil particle surface and higher concentration in the soil-water system. According to the correlation coefficients, it was found that both the Henry linear and the Freundlich nonlinear isotherm sorption models were fitted to the data very well, however the Freundlich model was better than the Henry model.
基金supported by the National Key Basic Research Program(973 Program) of China (No.2011CB100502)
文摘Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and processes.In this study,PSD of three clayey soils collected from the topsoil(0-20 cm) of Vertisols in Northern China was analyzed using the N_2 adsorption(NA) and mercury intrusion porosimetry(MIP) methods.The effect of soil organic matter(SOM) on the PSD of clayey soils was also evaluated.The differential curves of pore volume of clayey soils by the NA method exhibited that the pores with diameter < 0.01 μm accounted for more than 50%in the pore size range of 0.001 to 0.1 μm.The differential pore curves of clayey soils by the MIP method exhibited three distinct peaks in pore size range of 60 to 100,0.3 to 0.4 and 0.009 to 0.012 μm,respectively.In the three clayey soils,the ultramicropores(5-0.1μm) were determined to be the main pore class(on average 35.5%),followed by macropores(> 75 μm,31.4%),cryptopores(0.1-0.007μm,16.0%),micropores(30-5 μm,9.7%) and mesopores(75-30 μm,7.3%).The SOM greatly affected the pore structure and PSD of aggregates in clayey soils.In particular,SOM removal reduced the volume and porosity of 5-100 μm pores while increased those of <5 μm pores in the 5-2 and 2-0.25 mm aggregates of clayey soils.The increase in the volume and porosity of < 5 μm pores may be attributed to the disaggregation and partial emptying of small pores caused by the destruction of SOM.
文摘This paper studies the characteristics and mechanism of the adsorption of methylence blue from aqueous solution by humic acid which was extracted from swampy soil in Zhongdian of Yunnan in two methods.The result shows that the adsorption could fit the langmuir model.Humic acids extracted in two methods has the similar pattern of adsorption,but the Humic acid by sodium pyrophosphate has better adsorption because of its bigger specific surface area.The adsorptive constant and thermodynamic parameters have been evaluated in different temperatures.Furthermore the mechanism of adsorption on the humic acid has been discussed.
