太湖流域滆湖围网拆除后沉积物营养盐和重金属空间分布特征及评价

为评估滆湖围网拆除工程实施效果,采用高密度网格化布点方法,系统分析滆湖沉积物营养盐和重金属的空间分布和污染特征;并基于有机氮评价方法、综合污染指数评价方法、重金属地质累积指数法和重金属潜在生态风险评价方法进行污染风险评价.结果 表明,滆湖沉积物总氮(TN)、总磷(TP)和总有机碳(TOC)的平均含量分别为(3709± ...

Spatial distribution and pollution assessment on the main nutrients and heavy metals in sediments of Lake Gehu, Taihu Basin after removing the aquaculture net*

In this study, the spatial distribution characteristics of the main nutrients and heavy metals in sediments of Lake Gehu after completely removing the aquaculture net were investigated using high-density sampling methods, and their potential ecological risks were assessed based on organic nitrogen index, integrated pollution index, geo-accumulation index (I_geo) and potential ecological risk index. Results showed that the average contents of TN, TP and TOC were (3709±1004) mg/kg, (1127±650) mg/kg and (78.39±23.88) mg/g, respectively. The spatial distribution characteristics of TN, TP and TOC were relatively consistent, generally, those of the middle and upper part of the lake was higher than those of the southern part except the northern. Integrated pollution index showed that the whole lake was heavily polluted, meanwhile, the lake-was severely TN-polluted and slightly TP-polluted in most areas. The average contents of heavy metals Zn, Cr, As, Pb, Ni, Cu and Cd were (170.62±47.25), (105.18±34.91), (68.55±10.86), (52.43±14.73), (44.04±11.93), (42.57±12.43) and (1.55±1.06) mg/kg, respectively. Generally, the heavy metal contents increased from south to north, from west to east, and reached the highest level in the northeast corner. I_geo and the potential ecological risk assessment indicated that Cd and As were the most polluted elements and led to high potential ecological risk. According to the result of I_geo, Cr and Ni were not polluted, while Cr, Ni, Cu, Zn and Pb were at a slight potential ecological risk. Since the aquaculture net was being demolished, there was no significant change in the nutrient content in the southwestern part of the lake, and the nutrient status in the southern end of the Gehu Lake area was significantly improved, but the nutrient status in the rest of the area had deteriorated to varying degrees; the heavy metal content has a great reduction, ranging from 29.50% to 80.45%, indicating that when the input of external pollution is controlled to a certain extent, the removal of the fence has a positive effect on the effect of controlling nitrogen and phosphorus and improving the pollution of heavy metals.