水源水库沉积物碳氮磷分布特征及污染评价

Distribution characteristics of carbon,nitrogen and phosphorus in sediments of water source reservoir and pollution assessment

茜坑水库作为深圳市重要的水源水库,对当地经济发展和社会稳定有着重要作用.为探究茜坑水库沉积物中营养物质的空间分布特征及污染状况,测定了茜坑水库14个点位表层沉积物中总氮(TN)、总磷(TP)和总有机碳(TOC)的含量,分析了TN、TP、TOC之间的相关性及TOC/TN,并对沉积物污染状况进行了评价.结果表明,茜坑水库表层沉积物TN平均含量为3442 mg·kg^(−1),TP平均含量为1648 mg·kg^(−1),TOC平均含量为1.477%,碳、氮、磷污染严重且空间分布差异明显,旧库区主库及库湾碳、氮、磷含量均大于新库区.相关性分析表明,TOC与TN、TOC与TP、TN与TP均呈显著正相关关系(P<0.05,r^(2)分别为0.95,0.63,0.69),表明茜坑水库表层沉积物氮磷多以有机形式存在,且氮磷具有同源性.TOC/TN表明茜坑水库沉积物中的有机质多来自于藻类,还有一小部分来自水生生物.综合污染指数和有机指数评价结果均表明茜坑水库各个点位沉积物污染程度严重,氮、磷、有机质具有潜在的内源释放的风险.

As an important water source reservoir in Shenzhen,Xikeng Reservoir plays an important role in local economic development and social stability.To explore the spatial distribution characteristics and pollution status of nutrients in the sediments of the Xikeng Reservoir,this study determined the total nitrogen(TN),total phosphorus(TP)and total organic carbon(TOC)of the surface sediments at 14 points in the Xikeng Reservoir,analyzed the correlation between TN,TP,TOC and TOC/TN,and evaluated the sediment pollution.The results showed that the average content of TN in the surface sediments of Xikeng Reservoir was 3442 mg·kg^(−1),the average content of TP was 1648 mg·kg^(−1),the average content of TOC was 1.477%,the pollution of carbon,nitrogen,and phosphorus was serious and the spatial distribution difference was obvious.The carbon,nitrogen and phosphorus contents of the main reservoir and reservoir bay in the old reservoir area were higher than those in the new reservoir area.The correlation showed that TOC and TN,TOC and TP,TN and TP were all significantly positively correlated(P<0.05,r^(2) was 0.95,0.63,0.69,respectively),indicated that the nitrogen and phosphorus in the surface sediments of Xikeng Reservoir mostly existed in organic form,and nitrogen and phosphorus had homology.TOC/TN indicated that the organic matter in the sediments of Xikeng Reservoir mostly came from algae,and a small part came from aquatic organisms.The evaluation results of the comprehensive pollution index and the organic index indicated that the sediment pollution at each point of the Xikeng Reservoir was serious,and there were potential risks of internal release of nitrogen,phosphorus,and organic matter.