土壤性质对砂土亚表层磷迁移的影响

The soil factors influencing the potential migration of dissolved and particulate phosphorus （P） from structurallyweak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were extracted from two types of soils to make the colloid-bound forms of P solution. Eight sandy soils with diverse properties were collected for packing soil columns. The effects of influent solutions varying in concentrations of colloids, P, and electrolyte, on the transport of P and quality of leachates were characterized. P migration in the soils was soil property-dependent. High soil electrical conductivity values retarded the mobility of colloids and transportability of colloid-associated P （particulate P）. Soil electrical conductivity was negatively correlated with colloids and reactive particulate P （RPP） concentrations in the leachates, whereas, the total reactive P （TRP） and dissolved reactive P （DRP） concentrations in the leachates were mainly controlled by the P adsorption capacity and the P levels in the subsoil. The reactive particulate P in the leachates was positively correlated with the colloidal concentration. Increased colloidal concentration in the influent could significantly increase the colloidal concentration in the leachates. Elevated P concentration in the influent had little effect on P recovery in the leachates, but it resulted in significant increases in the absolute P concentration in the leachates.

Effects of soil properties on phosphorus subsurface migration in sandy soils

The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater.A laboratory-designed large soil tank with periodic and continuous infiltration models,respectively,was used to simulate the migration of the contaminants NHa and NO3 in a soil and groundwater system,including unsaturated and saturated zones.The unsaturated soil zone had a significant effect on removing NH4 and NO3 infiltrated from the surface water.The patterns of breakthrough curves of NH4 and NO3 in the unsaturated zone were related to the infiltration time.A short infiltration time resulted in a single sharp peak in the breakthrough curve,while a long infiltration time led to a plateau curve.When NHa and NO3 migrated from the unsaturated zone to the saturated zone,an interfacial retardation was formed,resulting in an increased contaminant concentration on the interface.Under the influence of horizontal groundwater movement,the infiltrated contaminants formed a contamination-prone area downstream.As the contaminants migrated downstream,their concentrations were significantly reduced.Under the same infiltration concentration,the concentration of NO3 was greater than that of NH4 at every corresponding cross-section in the soil and groundwater tank,suggesting that the removal efficiency of NH4 was greater than that of NO3 in the soil and groundwater system.