梁子湖沉积物营养盐的空间分布特征及其污染评价

采集梁子湖柱状沉积物,分析其硝氮、亚硝氮、氨氮、总氮和总磷的空间分布特征,并评价其污染程度.结果表明:梁子湖表层沉积物(0~5 cm)总氮、总磷、氨氮、硝氮、亚硝氮的含量范围依次为598~1372 mg·kg~(-1)、323~804 mg·kg~(-1)、60.7~142 mg·kg~(-1)、4.16~31.6 mg·kg~(-1)和0.001~2.29 mg·kg~(-1).湖心区营养盐含量较低,湖区西部营养盐含量高于湖区东南部.人类活动和污染物输入强度对梁子湖表层沉积物营养盐的空间分布特征有较大影响.沉积物硝氮、亚硝氮含量从深层到浅层递增,在2~3 cm处达到峰值,这表明梁子湖流域在该沉积时期的营养物污染较为严重.沉积物5~10 cm深度的氨氮含量为各深度中的最高值,但因水生生物对氨氮的优先吸收作用,其含量均在150 mg·kg~(-1)以下.同一区域的沉积物总氮、总磷含量的垂向变化特征相似,来自地壳释放的磷使得总磷含量的垂向波动幅度远大于总氮,这揭示了梁子湖沉积物中氮、磷的富集很可能来自同源污染物.该流域发达的水产养殖业是导致沉积物中氮、磷富集的原因之一.表层沉积物总氮和总磷的标准指数变化范围分别为1.09~2.49和0.54~1.34,梁子湖环境质量受到氮素的影响更为严重.湖区表层沉积物总氮、总磷的含量范围分别为598~1372 mg·kg~(-1)和323~804 mg·kg~(-1),均已超出我国东部浅水湖泊沉积物的营养物阈值参考范围,对湖泊生态系统构成了一定的威胁,需要格外关注.

Spatial distribution and pollution evaluation of nutrients in the sediments of Liangzi Lake

Sediments from Liangzi Lake were collected and analyzed to study the spatial distribution and pollution risk evaluation of the nutrients. The results show that: the content range of TN,TP,NH₃-N,NO₃-N,NO₂-N of the surface sediments (0~5 cm) in Liangzi Lake was respectively 598~1372 mg·kg^-1, 323~804 mg·kg^-1, 60.7~142 mg·kg^-1,4.16~31.6 mg·kg^-1 and 0.001~2.29 mg·kg^-1. Nutrients content was higher in the western lake than that in the southeastern lake, while it was very low in the center of the lake. Human activity and pollutant input strength had a great influence on the spatial distribution of nutrients of the surface sediments in Liangzi Lake. The content of NH₃-N and NO₃-N of the sediments in Liangzi Lake increased from the deep layer to the shallow layer, and reached the peak at the depth of 2~3 cm, which implied that the scale of modern industry and agriculture in Liangzi Lake Basin reached an unprecedented scale in this depositional period. NH₃-N content of the sediments was higher at the depth of 5~10 cm than other layers. And the NH₃-N content of all the sediments was below 150 mg·kg^-1 because of the preferentially absorption by aquatic plants. The distribution characteristic of TN and TP of the sediments was similar in the vertical direction, which revealed that the enrichment of TN and TP in the sediments may come from the homologous pollutants. Developed aquaculture in Liangzi Lake Basin was one of the reasons leading to the accumulation of TN and TP in the sediment. Besides, phosphorus in sediments coming from the crustal activity caused a greater fluctuation of TP content than TN in the vertical direction. The variation range of the standard index of TN and TP of the sediments in Liangzi Lake were 1.09~2.49 and 0.54~1.34, suggesting that the environmental quality in Liangzi Lake Basin was more seriously influenced by nitrogen. The content of TN and TP of the sediments in Liangzi Lake was ranging respectively 598~1372 mg·kg^-1 and 323~804 mg·kg^-1, which had been beyond their threshold range in eastern shallow lakes in China, posing a threat to the ecosystem of the lake.