合肥市十八联圩湿地表层沉积物营养盐与重金属分布及污染评价

十八联圩是南淝河入巢湖湖口区一处由"退耕还湿"形成的大型人工湿地.为了解其表层沉积物营养盐与重金属分布和污染特征,于2018年7月采集湿地内部和外部毗邻水体共72个位点的沉积物样品进行调查,并对污染来源进行了分析.结果表明,在十八联圩湿地内部水体中,表层沉积物总氮(TN)、总磷(TP)和有机质(OM)平均含量分别为2 108. 87mg·kg~(-1)、1 448. 82 mg·kg~(-1)和86. 2 g·kg~(-1),而在外部水体中,分别为2 305. 81 mg·kg~(-1)、1 268. 46 mg·kg~(-1)和59. 9 g·kg~(-1).重金属Mn、Cr、Cu、Pb、Cd、As和Hg在湿地内、外部水体中的平均含量分别为462. 58、42. 12、21. 69、18. 05、0. 63、5. 67和0. 059 mg·kg~(-1); 381. 61、36. 85、24. 74、30. 70、2. 49、6. 47和0. 035 mg·kg~(-1).湿地内水体表层沉积物,在营养盐污染评价中,TN整体处于轻度至中度污染水平,TP整体处于重度污染水平,营养盐整体处于中度至重度污染水平;在有机污染指数评价中,OM整体处于中度至重度污染水平;在重金属潜在生态风险评价中,潜在生态风险指数(RI)和潜在生态风险系数(Eir)表明,部分区域的Cd与Hg具有一定的生态风险.而湿地外毗邻水体表层沉积物的营养盐水平同样较高,且重金属污染严重,所有位点均达到强生态风险以上.

Distribution and Pollution Assessment of Nutrients and Heavy Metals in Surface Sediments from Shibalianwei Wetland in Hefei, Anhui Province, China

Shibalianwei is a large constructed wetland formed at the estuary of the Nanfei River adjoining Lake Chaohu. To investigate the distribution and pollution characteristics of nutrients and heavy metals in surface sediments of Shibalianwei Wetland, sediment samples were collected from 72 sites in July 2018. The source of the pollution was analyzed. Our results showed that the average contents of total nitrogen (TN), total phosphorus (TP), and organic matter (OM) in surface sediments of Shibalianwei were 2108.87 mg·kg^-1, 1448.82 mg·kg^-1, and 86.2 g·kg^-1, respectively; in the external water system of the wetland, they were 2305.81 mg·kg^-1, 1268.46 mg·kg^-1, and 59.9 g·kg^-1, respectively. The average contents of heavy metals of Mn, Cr, Cu, Pb, Cd, As, and Hg in Shibalianwei were 462.58, 42.12, 21.69, 18.05, 0.63, 5.67, and 0.059 mg·kg^-1, respectively; in the external water bodies, they were 381.61, 36.85, 24.74, 30.70, 2.49, 6.47, and 0.035 mg·kg^-1, respectively. In the assessments of nutrient pollution of internal water bodies of Shibalianwei, TN was at mild to moderate pollution levels, TP was at a heavy pollution level, and the comprehensive pollution index (FF) indicated that nutrients in Shibalianwei were at moderate to heavy pollution levels. The assessment results of the organic pollution index (OI) were consistent with the FF. The potential ecological risk assessments of heavy metals showed that both Cd and Hg reached certain ecological risks, which were indicated by RI and E_rⁱ. For external water bodies, the nutrient levels were also high and heavy metal pollution was relatively serious, indicating high ecological risks.