The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated b...The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated by a modified Tessier sequential extraction technique.The results show that the chemical fraction of Pb in soil is mainly the Res fraction and followed by FMO fraction,and the WS,WO,FMO,and SO fractions in topsoils(0-10 cm) are higher than those in subsoils(30-40 cm).The sum of contents of WS and Ex fractions(SWE) in topsoils is significantly positively related with that in subsoils,indicating the strong mobility of Pb in WS and Ex fractions in soils,and the SWE in soils is higher than the German trigger value for the transfer path soil-plant,indicating the high bioavailability of Pb in soils of this area.Fortunately,SWE and the ratio of WS and Ex fractions(RWE) to the sum of all fractions generally decrease with the soil depth in soil profile and the RWE in soil profile is lower than 0.5%,indicating the low pollution risk for Pb in groundwater.In addition,soil particles,pH and Fe2O3 play an important role in the impact of mobility and chemical fractions of Pb in soils.展开更多
Field topography or microtopography plays an important role in achieving acceptable performance in border irrigation. Extension of conservation tillage across the North China Plain has resulted in change in field bott...Field topography or microtopography plays an important role in achieving acceptable performance in border irrigation. Extension of conservation tillage across the North China Plain has resulted in change in field bottom configuration. This study defined regular bottom configuration for border irrigation, and introduced three regular bottom configurations： border-strip irrigation （BSI）, border-furrow irrigation （BFI） and rill irrigation （RI）. The effects of regular bottom configuration on the hydraulic process and irrigation performance were evaluated by field experiments and a WinSRFR3.1 model. Results suggest that the WinSRFR3.1 model was capable of the simulation of BFI and RI, and that the hydraulic process and irrigation performance were diverse among BSI, BFI, and RI. BSI had the highest infiltration rate while BFI had the lowest infiltration rate; BSI took the most time to complete the water advance while BFI took the least time. As a result, BSI showed the worst irrigation performance while BFI gave the best irrigation performance. Different field bottom configurations mainly accounted for differences. We conclude that regular field bottom configuration is an important factor for acceptable performance in border irrigation.展开更多
基金Project(41103059) supported by the National Natural Science Foundation of ChinaProject(2010CB428806-2) supported by the National Basic Research Program of China
文摘The chemical fractions,i.e.,water soluble(WS),exchangeable(Ex),carbonate(Car),weakly organic(WO),Fe-Mn oxide(FMO),strongly organic(SO),residual(Res) fraction,of Pb in irrigated soils in South China were investigated by a modified Tessier sequential extraction technique.The results show that the chemical fraction of Pb in soil is mainly the Res fraction and followed by FMO fraction,and the WS,WO,FMO,and SO fractions in topsoils(0-10 cm) are higher than those in subsoils(30-40 cm).The sum of contents of WS and Ex fractions(SWE) in topsoils is significantly positively related with that in subsoils,indicating the strong mobility of Pb in WS and Ex fractions in soils,and the SWE in soils is higher than the German trigger value for the transfer path soil-plant,indicating the high bioavailability of Pb in soils of this area.Fortunately,SWE and the ratio of WS and Ex fractions(RWE) to the sum of all fractions generally decrease with the soil depth in soil profile and the RWE in soil profile is lower than 0.5%,indicating the low pollution risk for Pb in groundwater.In addition,soil particles,pH and Fe2O3 play an important role in the impact of mobility and chemical fractions of Pb in soils.
基金the Knowledge Innovation Program,Chinese Academy of Sciences (No.KSCX2-EW-B-1andKSCX1-YW-09-06)
文摘Field topography or microtopography plays an important role in achieving acceptable performance in border irrigation. Extension of conservation tillage across the North China Plain has resulted in change in field bottom configuration. This study defined regular bottom configuration for border irrigation, and introduced three regular bottom configurations： border-strip irrigation （BSI）, border-furrow irrigation （BFI） and rill irrigation （RI）. The effects of regular bottom configuration on the hydraulic process and irrigation performance were evaluated by field experiments and a WinSRFR3.1 model. Results suggest that the WinSRFR3.1 model was capable of the simulation of BFI and RI, and that the hydraulic process and irrigation performance were diverse among BSI, BFI, and RI. BSI had the highest infiltration rate while BFI had the lowest infiltration rate; BSI took the most time to complete the water advance while BFI took the least time. As a result, BSI showed the worst irrigation performance while BFI gave the best irrigation performance. Different field bottom configurations mainly accounted for differences. We conclude that regular field bottom configuration is an important factor for acceptable performance in border irrigation.
