巢湖重污染汇流湾区沉积物营养盐分布与释放风险

南淝河、十五里河等多条入湖河道的向心型分布使巢湖西北部湖区形成汇流湖湾,了解该水域沉积物中营养盐累积分布及其释放风险,对评估污染状况具有重要意义. 于该研究湾区设置17个采样点,对沉积物营养盐含量及形态分布进行了调查分析,并使用静态释放方法对沉积物营养盐释放风险进行了研究. 结果表明:研究湾区表层沉积物中w(TN)和w(TP)分别为1 399.3~3 739.4和607.9~1 602.3 mg/kg,均远高于巢湖沉积物中w(TN)、w(TP)的平均值；w(NH₄+-N)占w(TN)的5.62%~17.60%,16个采样点的w(Al-P)占w(TP)的50%以上,由此导致沉积物中NH₄+-N和PO₄3--P释放通量较大,分别达到14.27~128.24和0.07~13.00 mg/(m2·d),并且在各河口区域释放风险相对高于湾区其他区域；氮、磷含量垂向分析显示,营养盐污染累积始于20世纪50年代(沉积物深度为24 cm),自80年代到90年代后期营养盐积累速率急速加剧. 沉积物中高含量的氮、磷营养盐及NH₄+-N和PO₄3--P释放通量导致该研究湾区沉积物成为巢湖水体的潜在污染源,因此亟需进行以各河口区域为重点的营养盐污染整治. 

Distribution and Release Risk of Nutrients in the Sediments of Heavily Polluted Confluence Bay of Chaohu Lake

The confluence bay region was formed in the northwest of Chaohu Lake because of the radial distribution of several inflow rivers, such as Nanfei River, Shiwuli River, etc. It is therefore very meaningful to know the cumulative distribution and release risk nutrients in this area for the pollution status evaluation. Hence, 17 sediment samples were collected to analyze the nutrient concentration and formations. In addition, the release risk of the nutrients from the sediments was evaluated using the statistical cultivation. The results showed that:1) the w(TN) and w(TP) ranged from 1399.3 to 3739.4 mg/kg and from 607.9 to 1602.3 mg/kg, respectively. The two parameters were higher than their mean values in the sediment of Chaohu Lake. 2) The ratios of w(NH₄+-N) to w(TN) were from 5.62% to 17.60%. Meanwhile, the ratio of w(Al-P) to w(TP) exceeded 50% in 16 sampling sites. The release fluxes of NH₄+-N and PO₄3--P reached 14.27-128.24 and 0.07-13.00 mg/(m2·d) respectively, because of the high ratios of w(NH₄+-N) and w(Al-P). Moreover, nutrient release risks in the estuaries of Chaohu Lake were much higher than that in other areas in the bay. 3) The vertical distributions patterns of w(TN) and w(TP) indicated that the accumulation of nutrients initiated from the 1950s (a correspondent sediment depth of 24 cm) and accelerated sharply in the 1980s to the late 1990s. Therefore, sediments in the confluence bay was a vital pollution source to the water body of Chaohu Lake because of the high levels of w(TN) and w(TP) and the considerable release fluxes of NH₄+-N and PO₄3--P. In conclusion, urgent measures must be taken to control the nutrients pollution in the bay, especially in the estuaries.