Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nu...Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25oC, and samples were collected at 1, 7, and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concen-trations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.展开更多
The effects of sorbed phosphate on the kinetics of Cu￣2+ secondary adsorption on three major types ofsoils in southern and Central China were studied using the batch method and flow (or miscible displacement)techniqu...The effects of sorbed phosphate on the kinetics of Cu￣2+ secondary adsorption on three major types ofsoils in southern and Central China were studied using the batch method and flow (or miscible displacement)techniques. Both of the methods showed that diffusions were the ratedetermining steps in the Cu￣2+ adsorp-tion by the soils. By the flow method, the course of Cu￣2+ adsorption kinetics consisted of two steps-sn initialrapid process and a later slow process of Cu￣2+ adsorption; while by the batch method, the 90% of Cu￣2+adsorption reaction was found to finish within first 1 minute. The results obtained using the flow method alsoindicated that for red soil and yellow-brown soil, Cu￣2+ adsorptions during the initial reaction periods wererestrained when the soils sorbed phosphate, whereas the adsorption reactions were stimulated at the finaltime. For grey Chao soil, sorbed phosphate retarded the Cu￣2+ adsorption in the whole reaction period. Theresults obtained using the batch method and flow techniques all implied that the different effects of sorbedphosphate would be attributed to its effects on Cu￣2+ ion diffusion in soil solution.展开更多
文摘Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25oC, and samples were collected at 1, 7, and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concen-trations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.
文摘The effects of sorbed phosphate on the kinetics of Cu￣2+ secondary adsorption on three major types ofsoils in southern and Central China were studied using the batch method and flow (or miscible displacement)techniques. Both of the methods showed that diffusions were the ratedetermining steps in the Cu￣2+ adsorp-tion by the soils. By the flow method, the course of Cu￣2+ adsorption kinetics consisted of two steps-sn initialrapid process and a later slow process of Cu￣2+ adsorption; while by the batch method, the 90% of Cu￣2+adsorption reaction was found to finish within first 1 minute. The results obtained using the flow method alsoindicated that for red soil and yellow-brown soil, Cu￣2+ adsorptions during the initial reaction periods wererestrained when the soils sorbed phosphate, whereas the adsorption reactions were stimulated at the finaltime. For grey Chao soil, sorbed phosphate retarded the Cu￣2+ adsorption in the whole reaction period. Theresults obtained using the batch method and flow techniques all implied that the different effects of sorbedphosphate would be attributed to its effects on Cu￣2+ ion diffusion in soil solution.
