沂蒙山区典型小流域特殊降雨的磷素输出特征

为揭示沂蒙山区不同降雨条件下的磷素流失规律,对当地孟良崮小流域2010年13场自然降雨径流量及磷素浓度的动态过程进行实地监测,研究了年内产生有效径流的首场和最大强度2场特殊降雨的径流、磷素输出负荷、初期冲刷效应及径流量同磷素负荷之间的关系.结果表明,首场降雨径流中溶解态有机磷(DOP)、溶解态无机磷(DIP)、溶解态全磷(DP)、颗粒态全磷(PP)和总磷(TP)浓度明显高于最大强度降雨,而其输出负荷分别为最大强度降雨的168%、54%、71%、48%和54%;2场降雨对小流域磷素年输出负荷有重要影响,DOP、DIP、DP、PP和TP的输出总量分别占整个雨季输出的48%、81%、70%、87%和81%,其中DIP占DP流失的77%,PP占TP流失的71%;2场降雨均存在污染物的初期冲刷效应,最大强度降雨的初期冲刷效应较首场降雨强烈;2场降雨的各磷素累积输出负荷同累积径流量之间均呈线性关系,且拟合度较好,但首场降雨各形态磷素直线方程的斜率均大于最大强度降雨.根据气象预报尽量减少在特殊降雨期间翻耕、施肥等农事活动,以及有针对性地建立沟渠、池塘等截污措施减少初期冲刷效应,是降低农业非点源污染的有效途径.

Output Characteristics of Non-point Phosphorus from a Typical Small Watershed in Yimeng Mountainous Area Under the Special Rainfall

The relationships between pollutant concentrations and precipitation-runoff combined with the first and maximum intensity natural rainfall events were monitored at the outlets of the Menglianggu watershed in 2010. The results showed that dissolved organic phosphorus (DOP), dissolved inorganic phosphorus (DIP), total dissolved phosphorus (DP), total particle phosphorus (PP) and total phosphorus (TP) concentrations in the first rainfall were higher than those in the maximum intensity rainfall which was the largest average rainfall intensity, but the output of phosphorusin the first rainfall was all higher than that in the maximum intensity rainfall except dissolved organic phosphorus. The DOP, DIP, DP, PP and TP in two special rainfall events contributed 48%, 81%, 70%, 87% and 81% of the total output of rainy season. DP and TP were mainly composed by DIP and PP respectively. The two special rainfalls have the first flush effect and the maximum intensity rainfall was stronger than the first rainfall, so the analysis of M (V) curve showed that the priority should be given to the interception of corresponding phosphorus under special events. The regression analysis results showed that a linear relation existed between runoff and nutrient output, but there were some differences which the slope of the linear equation of the first rainfall was higher than that of the maximum intensity rainfall. Reducing agricultural practices such as tillage and fertilization during special rainfall period and building canals, ponds are effective ways for mitigating agricultural non-point source pollution.