南湖水系水-沉积物磷时空分布、影响因素及控制对策

位于嘉兴市中心城区的南湖及周边水体(简称南湖水系)是杭嘉湖水网的重要组成部分。根据历史监测资料及现场调查结果,分析了南湖水系水-沉积物中磷的时空分布、形态组成及其影响因素。结果表明,南湖水体总磷(TP)浓度为0.121~0.388 mg/L,高值多出现在入湖河道附近,且夏季TP浓度显著高于其他季节;南湖周边水体TP浓度为0.026~0.588 mg/L,高值多出现在西、北部河网;颗粒态磷(PP)是南湖水系中磷的主要赋存形态。南湖水系表层沉积物中TP浓度为479.91~3 456.55 mg/kg,显著高于我国东部部分湖泊,TP浓度呈现由南湖向周边河网逐渐减小的分布趋势;沉积物中的磷以无机磷(IP)为主,且生物可利用IP形态总和在IP中的占比(59.23%)高于较稳定的IP形态(40.77%)。水体中的磷与水体悬浮物浓度呈显著正相关,受到内源释放和外源输入的共同影响,应着力于降低水体悬浮物浓度,通过实施底泥疏浚,结合水生植物恢复,达到降低水体磷浓度的目的。

Spatio-temporal distribution,influencing factors and control strategies of phosphorus in water-sediment of Nanhu Lake water system

Nanhu Lake water system located in the downtown of Jiaxing City is an important part of the Hangzhou-Jiaxing water network. Based on the historical monitoring data and field investigation, the spatio-temporal distribution and morphological composition of phosphorus in water and sediment of Nanhu Lake and the surrounding river network were analyzed, and the influencing factors were discussed. The results showed that total phosphorus (TP) concentrations in Nanhu Lake were between 0.121 and 0.388 mg/L, with the high concentrations mostly near the river at the mouth of the lake, and TP concentrations in summer were significantly higher than those in other seasons. TP concentrations in the surrounding waters were between 0.026 and 0.588 mg/L, with the high concentrations in the western and northern parts. Particulate phosphorus (PP) was the major species of phosphorus in water system of Nanhu Lake. TP content in the surface sediments of Nanhu Lake and its surrounding river network ranged from 479.91 to 3 456.55 mg/kg, which was higher than that of several lakes in eastern China, and it showed a decreasing trend of TP content from the lake to the surrounding river network. Inorganic P (IP) was dominant in the sediments, of which the proportion of sum of the bioavailable IP fractions in IP contents (59.23%) was higher than the proportion of relatively stable IP fraction (40.77%). There was a significant positive correlation between phosphorus and suspended solids in water, which was affected by internal release and external inputs. According to the results, the phosphorus contamination in Nanhu Lake and the surrounding water should be controlled by decreasing the suspended matter contents in the water and implementing sediment dredging, combining with the restoration of aquatic plants.