沙土不同粒径微团聚体对磷的富集特征

流失的水土是污染物的重要载体,为估算沙土吸附态磷流失量,采用平衡吸附法研究了沙土不同粒径微团聚体对磷的富集特征.结果表明,不同粒径微团聚体对磷的富集系数为:黏粒(3.79)＞粉粒(2.98),沙土中微团聚体对磷的富集作用比较强,其原因有三:细粒级微团聚体中腐殖质含量显著高于粗粒级；细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集,在复合体结构中存在孔隙填充方式磷吸附；粘粒和粉粒中的铁铝键有机矿质复合体所占比例显著高于其它粒级,在对磷吸附中发挥重要作用,其吸附机制除孔隙填充方式外,还存在铁铝氧化物及水化氧化物对磷的配位吸附.不同粒径团聚体对磷的吸附分配系数和富集系数均与腐殖质总量呈显著正相关(p＜ 0.01,r分别为0.854和0.954)；西辽河流域沙土在暴雨径流中黏粒级和粉粒级冲泻质泥沙所携载的吸附态磷质量分数可分别按1269.15 mg·kg-1和997.53 mg·kg-1估算,黏粒和粉粒级微团聚体对磷的富集系数(Er)可分别按3.79和2.98计算.

Enrichment characteristics of phosphorus on micro-aggregates in different sizes of sandy soil

Loss of soil and water were significant carriers of pollutant. In order to estimate loss flux of phosphorus in adsorption state, enrichment characteristic of phosphorus on micro-aggregate in different sizes of sandy soil was investigated by batch experiments of equilibrium adsorption. Results indicated that enrichment ratio of clay (3.79) was higher than that of silt (2.98). The enrichment effect of phosphorus on micro-aggregates of sandy soil was relatively strong, which may be due to three reasons. Firstly, organic matter content of fine grain size aggregates was higher than that of coarse grain size aggregates. Secondly, organic matter of fine grain size aggregates was enriched by forming complex with clay mineral, and a sorption mode with pore filling existed in the complex structures. Thirdly, the content of Fe/Al-bound complex in clay or silt was relatively higher and played an important role in phosphorus sorption on sandy soil. Apart from micro-hole filling, the sorption mechanism of phosphorus can be also through hydration oxide coordination. There were significantly positive correlations between adsorption partition coefficient, enrichment ratio and total organic matter content, with the correlation coefficient of 0.854 and 0.954, respectively. The mass percentages of adsorption-state phosphorus carried by clay and silt from sandy soil in the Xiliao River under heavy rainfall condition were estimated as 1269.15 mg·kg^-1 and 997.53 mg·kg^-1 respectively,and the enrichment ratio of clay and silt were estimated as 3.79 and 2.98 respectively.