An investigation was conducted to identify the characteristics of heavy metals in orange ecosystem in three areas in the Three Gorge Reservoir Region by using the modified Tessier sequential extraction procedure.The c...An investigation was conducted to identify the characteristics of heavy metals in orange ecosystem in three areas in the Three Gorge Reservoir Region by using the modified Tessier sequential extraction procedure.The contents of Cu and Pb in different speciation fractions of the soils can be ordered as the Residual(F6)>Reducible(F4)>Oxidable(F5)>Water soluble(F1)>Carbonate(F3)>Exchangeable(F2),and the contents of Zn and Ni follow the order of the Residual(F6)>Oxidable(F5)>Reducible(F4)>Water soluble(F1)>Carbonate(F3)> Exchangeable(F2),and those of Cd follow the order of the Reducible(F4)>Oxidable(F5)>Exchangeable(F2)> Carbonate(F3)>Residual(F6)>Water soluble(F1).The concentrations of Cu in the different organs of oranges follow the increasing sequence of pulp>leaf>pericarp,those of Zn and Ni following the increasing sequence of leaf >pulp>pericarp,and those of Pb and Cd follow the increasing sequence of leaf>pericarp>pulp.Correlation degrees of different forms of same heavy metals in soils are according to the order of Cu>Zn>Cd>Pb>Ni.Correlation degrees of different heavy metals in same forms are according to the order that the forms of Reducible(F4),Oxidable(F5) and Residual(F6) are higher than the forms of Water soluble(F1),Exchangeable(F2) and Carbonate(F3).There are either positive or negative correlations between heavy metals in leaves and in pulp,while there are all positive correlations between heavy mentals in leaves and in pericarp.There are significant correlations between the concentrations of some heavy metals in leaves,pericarp or pulp,and those in speciation fractions in the soils.展开更多
The exchange of mercury(Hg) across the air-water interface is an important part of Hg biogeochemical cycle.Mercury fluxes across the air-water interface in paddy fields were measured by a Dynamic Flux Chamber(DFC) cou...The exchange of mercury(Hg) across the air-water interface is an important part of Hg biogeochemical cycle.Mercury fluxes across the air-water interface in paddy fields were measured by a Dynamic Flux Chamber(DFC) coupled with a Lumex multifunctional mercury analyzer RA-915+ at two sites(Chengjiang(CJ) and Caoshang(CS)) in Beibei,Chongqing,China in 2008.The results showed that mercury emission followed a power-law relationship with solar radiation and air temperature,and it increased exponentially with water temperature at both sites.Mercury emission was mainly influenced by the solubility of gaseous elemental Hg,photo-thermal effect,electron activity(Eh) and air Hg concentrations.Solar radiation made the greatest direct contribution to mercury emission during the daytime(0.80),with an 83.60% contribution,whereas at nighttime the water temperature(0.72) contributed to 71.65% of emissions.The temperature gradient between water and air might also influenced mercury emission across the air/water interface at nighttime.These findings suggest that paddy fields could act as a significant source of atmospheric mercury,and it can contribute significantly to the atmospheric mercury in a local region.展开更多
基金supported by the National Natural Science Foundation of China (No. 40573065)the Science and Technology Committee of Chongqing Foundation (No. 7335)
文摘An investigation was conducted to identify the characteristics of heavy metals in orange ecosystem in three areas in the Three Gorge Reservoir Region by using the modified Tessier sequential extraction procedure.The contents of Cu and Pb in different speciation fractions of the soils can be ordered as the Residual(F6)>Reducible(F4)>Oxidable(F5)>Water soluble(F1)>Carbonate(F3)>Exchangeable(F2),and the contents of Zn and Ni follow the order of the Residual(F6)>Oxidable(F5)>Reducible(F4)>Water soluble(F1)>Carbonate(F3)> Exchangeable(F2),and those of Cd follow the order of the Reducible(F4)>Oxidable(F5)>Exchangeable(F2)> Carbonate(F3)>Residual(F6)>Water soluble(F1).The concentrations of Cu in the different organs of oranges follow the increasing sequence of pulp>leaf>pericarp,those of Zn and Ni following the increasing sequence of leaf >pulp>pericarp,and those of Pb and Cd follow the increasing sequence of leaf>pericarp>pulp.Correlation degrees of different forms of same heavy metals in soils are according to the order of Cu>Zn>Cd>Pb>Ni.Correlation degrees of different heavy metals in same forms are according to the order that the forms of Reducible(F4),Oxidable(F5) and Residual(F6) are higher than the forms of Water soluble(F1),Exchangeable(F2) and Carbonate(F3).There are either positive or negative correlations between heavy metals in leaves and in pulp,while there are all positive correlations between heavy mentals in leaves and in pericarp.There are significant correlations between the concentrations of some heavy metals in leaves,pericarp or pulp,and those in speciation fractions in the soils.
基金supported by the National Natural Science Foundation of China (40673063 and40973079)the "211" Ecology National Key Discipline of Southwest UniversityPostgraduates’ Science & Technological Innovation Fund of Southwest University (kb2010019)
文摘The exchange of mercury(Hg) across the air-water interface is an important part of Hg biogeochemical cycle.Mercury fluxes across the air-water interface in paddy fields were measured by a Dynamic Flux Chamber(DFC) coupled with a Lumex multifunctional mercury analyzer RA-915+ at two sites(Chengjiang(CJ) and Caoshang(CS)) in Beibei,Chongqing,China in 2008.The results showed that mercury emission followed a power-law relationship with solar radiation and air temperature,and it increased exponentially with water temperature at both sites.Mercury emission was mainly influenced by the solubility of gaseous elemental Hg,photo-thermal effect,electron activity(Eh) and air Hg concentrations.Solar radiation made the greatest direct contribution to mercury emission during the daytime(0.80),with an 83.60% contribution,whereas at nighttime the water temperature(0.72) contributed to 71.65% of emissions.The temperature gradient between water and air might also influenced mercury emission across the air/water interface at nighttime.These findings suggest that paddy fields could act as a significant source of atmospheric mercury,and it can contribute significantly to the atmospheric mercury in a local region.