龙窝湖湿地不同土地利用方式土壤养分和重金属污染特征

Characteristics of soil nutrients and heavy metal pollution in wetlands under different land use patterns in Longwo Lake of Wuhu City,Anhui Province,China

为了解人类活动对城市湿地土壤生态环境的影响，本文分析了芜湖市龙窝湖不同利用方式下湿地土壤养分、重金属含量的差异，并采用污染指数法和潜在生态风险指数法对重金属污染特征和潜在生态风险进行了评价。结果表明：不同利用方式下湿地土壤养分和重金属含量差异显著，总体上网围养殖湿地、塘式养殖湿地、垃圾倾倒处下游湿地和沟渠湿地土壤养分和重金属含量显著高于湖泊中心湿地和耕作湿地；龙窝湖不同类型湿地表层土壤均存在较高或严重的cd污染和中等cu污染，网围养殖湿地、塘式养殖湿地、垃圾倾倒处下游湿地和沟渠湿地表层土壤存在中等Pb和zn污染，但网围养殖湿地、塘式养殖湿地和垃圾倾倒处下游湿地表层土壤Cd含量显著超过土壤环境质量标准（二级）；综合污染指数显示，垃圾倾倒处下游湿地（27．35）、网围养殖湿地（26．23）和塘式养殖湿地（25．48）存在严重重金属污染，而沟渠湿地（10．49）、湖泊中心湿地（8．56）和耕作湿地（8．49）处于中等重金属污染，其中cd对各种利用类型湿地土壤重金属污染贡献率达49．O％-76．4％；综合潜在生态风险指数显示，垃圾倾倒处下游湿地（633）、网围养殖湿地（625）和塘式养殖湿地（588）存在很高潜在生态风险，而沟渠湿地（174）、耕作湿地（149）和湖泊中心湿地（144）处于高潜在生态风险，其中cd对各种利用类型湿地综合潜在生态风险指数贡献率达88．6％～96．2％。水产养殖和垃圾倾倒是龙窝湖湿地土壤氮磷等养分和重金属污染的主要来源．土壤养分与重金属污染存在一定的耦合关系。

Soil nutrient and heavy metal contents in wetlands under different land-use patterns were analyzed and the index of soil heavy metal pollution and the potential ecological risk index were calculated to assess the effects of land-use patterns on soil ecology and environment in Long- wo Lake of Wuhu City. The results showed that land-use patterns had significant effects on soil nutrient and heavy metal contents in the wetlands. In general, soil nutrient and heavy metal con- tents in net fishery wetland （NFW）, pond fishery wetland （PFW）, rubbish dumping wetland （RDW） and ditch wetland （DW） were significantly higher than in farming wetland （FW） and lake wetland （LW）. All wetlands were seriously or very seriously polluted with Cd and moderate- ly polluted with Cu, while NFW, PFW, DW, RDW, and DW were moderately polluted with Pband Zn. Only soil Cd contents in NFW, PFW, and RDW seriously exceeded the second level of soil quality standard in China （GB 15618-1995 ）. Integrated pollution indexes indicated that RDW, NFW, and PFW were exposed to serious heavy metal pollution and DW, FW, and LW were exposed to moderate heavy metal pollution. Integrated potential ecological risk indexes indi- cated that RDW, NFW, and PFW had a very serious potential ecological risk and DW, FW, and LW had a serious potential ecological risk, mainly due to the high potential ecological risk of Cd with contribution of 88.6% -96.2%. Fishery and rubbish dumping were the main sources of soil nutrient and heavy metal pollution. Soil nutrient and heavy metal pollution had a coupling rela- tionship in the studied region.