拉鲁湿地沉积物碳氮磷分布及污染风险评价

Distribution of Carbon,Nitrogen and Phosphorus in Sediments of Lhalu Wetland in Dry and Wet Seasons and It′s Pollution Risk Assessment

拉鲁湿地是世界海拔最高、面积最大的城市天然湿地,为研究其沉积物污染的变化规律,于2018年12月(枯水期)和2019年5月(丰水期)分别采集了拉鲁湿地中59和48个点位的沉积物,分析总氮(TN)、总磷(TP)和总有机物(OM)的空间分布特征及其化学计量比,并运用综合污染指数法和有机污染指数法对其进行污染风险评价。结果表明,枯水期拉鲁湿地TN、TP和OM含量总体高于丰水期。枯水期沉积物TN、TP和OM含量分别为0.18~6.35、0.33~2.88和27.18~268.98 g·kg^(-1);TN和OM含量高的区域主要出现在拉鲁湿地的中西部和东部,而TP含量高的区域主要在西部和中西部。枯水期沉积物碳氮比(C/N)为15.04~85.31,北部显著高于其他区域(P<0.05);丰水期沉积物C/N比为3.09~97.46,西部显著低于其他区域(P<0.05)。枯水期和丰水期沉积物C/N比>10,说明沉积物中有机质都是以外源为主,且丰水期沉积物具有矿化作用。拉鲁湿地北部没有有机污染,其他区域均存在不同程度的污染。

Lhalu wetland is the world's highest and largest natural wetland in city.In order to study the changes of its sediment pollution,the sediments from 59 and 48 points of Lhalu wetland were collected in December 2018(dry season)and May 2019(wet season),respectively,which were analyzed for the spatial distribution characteristics and stoichiometric ratio of total nitrogen(TN),total phosphorus(TP)and total organic matter(OM).In addition,pollution risk assessment was carried out by the comprehensive pollution index method and organic pollution index.Results show that the content of TN,TP and OM in sediments were higher in wet season than in dry season.The content of TN,TP and OM in sediment in dry season was 0.18-6.35 g·kg^(-1),0.33-2.88 g·kg^(-1)and 27.18-268.98 g·kg^(-1),respectively.The highest content of TN and OM was found in middle-west and east of Lhalu wetland.However,the highest content of TP was found in west and middle-west of Lhalu wetland.The ratio of C/N in dry season was 15.04-85.31,which was significantly higher in the north part than in other parts of the Lhalu wetland(P<0.05).The ratio of C/N in wet season was 3.09-97.46,which was significantly lower in the west part than in the other parts of the Lhalu wetland(P<0.05).The ratio of C/N of the wetland was higher than 10,which suggests that the organic matters in dry and wet seasons were from outside.The OM in the sediments was mineralized during the wet season.The Lhalu wetland is relatively clean in the north,while some degrees of pollution were found in other parts of the wetland.