北京官厅水库流域农田地表径流生物可利用磷流失规律

在模拟降雨条件下(30-69mm/39min),对官厅水库流域玉米地和休闲地地表径流泥沙和生物可利用磷(BAP)流失进行了初步研究. 累积泥沙产量受雨强、坡度和作物覆盖影响,变幅为305.1-24933.4g/10m2;径流平均颗粒态生物可利用磷(BPP)、溶解态磷(SP)浓度都超出水体允许临界值0.02mg/L,表明流域农田地表径流对库区水体存在潜在污染危害;径流累积BAP流失达0.08-4.804g/10m2,估算的农田径流BAP流失达0.49kg/(hm2.a)以上. 79.7%以上的BAP是颗粒态的. 研究结果有助于采取措施减少农田径流向库区输入生物可利用磷、准确地评估流域农业管理实践对水库水质的影响.

Bioavailable Phosphorus Export by Surface Runoff from Agricultural Field Plots in Guanting Watershed,Beijing

Bioavailable P (BAP) in agricultural runoff represents P potentially available for algal uptake and consists of soluble P (SP) and a variable portion of particulate P (PP). Runoff and soil losses from agricultural fields were investigated as major nonpoint sources of phosphorus(P) entering Guanting Reservoir, Beijing. There is relatively little information on bioavailable P transport from cropland of Guanting watershed. Soil and bioavailable P in surface runoff from a series of plots in the waershed were evaluated under simulated rainfall conditions. The objectives of this study were to evaluate the effects of rainfall intensity, slope, crop cover, and fertilizer application on bioavailable P concentrations in surface runoff and eroded soil. Accumulated sediment yields varied from 305.1 to 24933.4g/10m2, depending on rainfall intensity, slope, crop cover, and fertilizer application. Weighted average concentrations of soluble P(SP) and particulate bioavailable P (BPP) were much higher than 0.02mg/L,the limiting concentration for lake (reservoir) water. This result showed the potential contamination of reservoir water from agricultural surface runoff. Accumulated BAP losses were 0.08-4.804g/10m2 for croplands. The estimated annual loss of BAP was more than 0.49kg/hm2 per year for croplands in Guanting watershed. Most of BAP loss was in the PP form, which accounted for more 79.7% of BAP loss from cropland. The large amount of BPP may constitute a long-term source of potentially bioavailable P in Guanting Reservoir.