西辽河流域不同土地利用结构沙土磷解吸特征

采用小型回填式土柱淋溶试验方法，研究了西辽河流域沙土的磷解吸特征.结果表明，西辽河流域沙土的磷解吸特征符合Freundlich和Langmuir解吸等温式；沙土磷的解吸比率(D_r)在0.32～0.98之间，平均值为0.70；最大解吸量(D_m)与饱和吸附量(Г_m)呈极显著正相关；沙土对磷的吸附方式以物理吸附为主，解吸可逆性较强.被吸附的磷在环境中较易发生淋失，仍然存在一定的环境风险.土壤中w(有机质)和w(团聚体)对磷的固持能力有较大影响；不同土地利用结构磷的D_r排序为农田(0.64)=草地(0.64)＜林地(0.67)＜沙荒地(0.91)，农田、草地和林地磷淋失的环境风险较小；沙荒地磷淋失的环境风险最大，D_r与土壤中w(粗黏粒)，w(黏粒)和w(有机质)呈极显著负相关. 

Desorption Characteristics of Phosphorus from Different Used Sandy Soil in Western Liao River Basin

Desorption characteristics of phosphorus from different used sandy soil in Western Liao River Basin were studied by a small backfilled earth-pillar experiment.Results indicate that the phosphorus desorption characteristics of the Western Liao River Basin sandy soil conform to the Freundlich and Langmuir desorption isotherms.Dr(phosphorus desorptive ratio) of the sandy soil was between 0.32 and 0.98,with an average of 0.70.There was a highly significant positive correlation between Dm(phosphorus maximum desorption) and Гm(phosphorus saturated sorption).The modes of phosphorus sorption to sandy soil are based on physical sorption,which is easy to leach out of the environment,and reversible desorption is relatively strong.Therefore,there is a certain risk to the environment.Mass percentage of soil organic matter and aggregates have a great impact on fixed or maintained phosphorus capacity.The results of the phosphorus desorption experiments on different land use structures show that the order of Dr is: farmland(0.64) = grassland(0.64) < forestland(0.67) < sandy wasteland(0.91).The environmental risk to farmland,grassland and forestland is relatively low,whereas the environment risk to sandy wasteland is the maximum.There are highly obvious negative correlations between Dr and mass percentages of soil organic matter,clay and coarse clay.