2010-2017年太湖总磷浓度变化趋势分析及成因探讨

近年来，太湖流域各省市政府加大治理力度，流域水体水质取得明显好转，氨氮浓度和总氮浓度呈大幅度下降趋势，然而太湖水体总磷浓度呈上升趋势.为探讨太湖总磷浓度升高的原因，采用太湖流域管理局2010年以来的水质水量实测数据、遥感监测数据等，分别从太湖入湖河流污染负荷量、水生植被和蓝藻与总磷浓度的关系3个方面进行相关性分析.结果表明，入湖河流总磷浓度高于太湖水体总磷浓度，且磷不易出湖，逐年总磷净入湖量持续累积与太湖总磷浓度有明显的正相关性，入湖污染负荷量大是太湖总磷浓度居高不下的根本原因；水生植被可吸收湖泊沉积物中的营养盐，并抑制底泥再悬浮从而降低内源性营养盐的释放，东太湖水生植被的大量减少，一方面减少了沉水植物对磷元素的吸收，另一方面增加了风浪对底泥的扰动再悬浮，造成磷元素释放，是造成湖水总磷浓度升高的重要因素；近年来太湖蓝藻密度呈上升趋势，受其影响，总磷浓度也有上升，蓝藻水华加快湖体磷循环，藻类密度增加也是太湖总磷浓度升高的影响因素之一.

Variation trend of total phosphorus and its controlling factors in Lake Taihu, 2010-2017

In recent years, the water quality of water bodies in Lake Taihu Basin has improved significantly because that all provinces and municipalities in the basin have intensified their efforts in pollution governance. In Lake Taihu, the concentration of ammonia nitrogen and total nitrogen showed a significant downward trend, while a upward trend for the concentration of total phosphorus (TP). To explore the reasons for such TP increase, this paper used the measured data and remote sensing data between 2010 to 2017 from Lake Taihu Basin Authority of Ministry of Water Resources. We analyzed the correlation between the pollution load of inflow river, aquatic vegetation and cyanobacteria and the TP. The results showed that the TP in the inflow rivers was higher than those in the Lake Taihu, and TP was not easy to remove from the lake. There was a significant positive correlation between the continuous accumulation of TP loading and the epilimnetic TP in Lake Taihu. It is concluded that the basic factor of the high TP concentration is the large amount of phosphorus loading into the lake. Aquatic vegetation can absorb nutrients from lake sediments and inhibit the resuspension of sediment so as to reduce the release of endogenous nutrients. The substantial decrease of aquatic vegetation led to the increase of TP concentration in East Lake Taihu. Recently the abundance of blue-green algae in Lake Taihu showed an increasing trend. Under such circumstance, the monitoring TP also increased.