退耕还湖后湿地土壤对磷的吸附解吸特性

以安徽菜子湖区不同退耕年限(3、5、9和11年)湿地为研究对象,以相邻油菜地和原始湿地为对照(共6个样地),研究退耕还湖后湿地土壤对磷的吸附解吸特性变化.结果表明: 退耕湿地土壤对磷的等温吸附曲线与Langmuir和Freundlich吸附方程拟合程度均达极显著水平(P<0.01);6个样地土壤对磷的最大吸附量(X_m)、吸附常数(K)和最大缓冲容量(MBC)范围分别为478～1074 mg·kg^-1、0.14～0.61和68.6～661.5 mg·kg^-1,且退耕湿地的这些参数均随着退耕年限的延长而升高,但未达到原始湿地水平;6个样地土壤磷的平均解吸率为6.2%～14.6%,且退耕湿地土壤磷解吸率随着退耕年限的延长呈先增高后降低的趋势,但均显著高于原始湿地.表明随着退耕年限的增加,湿地土壤对外源磷的固持能力不断增强,而土壤有机质和粘粒含量是影响湿地土壤对外源磷固持能力的重要因子.

Characteristics of phosphorus adsorption and desorption of soils from wetlands recovered from farmlands in Caizi Lake.

In this study, topsoil samples were collected from wetlands recovered from farmlands respectively for 3, 5, 9 and 11 years around Caizi Lake, Anhui, China. Their characteristics of adsorption and desorption of phosphorus were examined with comparison to soils sampled from an adjacent vegetable farmland and a non cultivated wetland. Phosphorus adsorption curves of all studied soils could be modeled by Langmuir and Freundlich equations (P<0.01). The maximum P adsorption (X_m), adsorption constant K and maximum buffer capacity (MBC) of all the 6 soil samples were in the ranges of 478-1074 mg·kg^-1, 0.14-0.61 and 68.6-661.5 mg·kg^-1, respectively. These three parameters all tented to increase with the recovered years but did not reach the values of the non cultivated wetland. However, the P desorption rate ranging from 6.2% to 14.6%, increased first and then decreased with the recovered years and was significantly higher than that of the non-cultivated wetland. It was concluded that the P immobilization would increase with the recovery years of cultivated wetlands, which could be affected by the soil organic carbon and clay contents of the wetland soil.