镇江市古运河和金山湖河湖上覆水体和沉积物氮及有机质分布特征及污染评价

Distribution Characteristics and Pollution Evaluation of Nitrogen and Organic Matter in Overlying Water and Sediment of Guyun River and Jinshan Lake in Zhenjiang City

镇江市位于长江和京杭大运河"十字黄金水道"的交汇处,是我国历史上最为重要的水上交通枢纽之一,区域内水量充沛、河网密布.近年来,该区域水环境存在不同程度的退化,故调查镇江市主要河湖水体及沉积物污染现状,将为当地水环境质量的改善提供重要的基础数据.基于此,本研究选择镇江市典型河湖水体共21个点位(金山湖10个点位,古运河及其支流共11个点位),在冬夏两季采集上覆水及沉积物样品测定其理化指标和氮素含量,并通过有机指数及有机氮对沉积物污染程度进行评价.结果表明:(1)上覆水总氮(TN)浓度在冬夏季节分别介于1.95~15.71 mg·L^(-1)和0.64~12.09 mg·L^(-1)之间,平均值为4.01 mg·L^(-1)和4.07 mg·L^(-1),平均值浓度高于地表水Ⅴ类标准.上覆水氨氮(NH^(+)_(4)-N)浓度在季节上均表现为冬季<夏季,空间上则表现为河流>湖泊;(2)沉积物TN含量在冬夏两季分别介于394.61~3288.09 mg·kg^(-1)和869.21~3598.04mg·kg^(-1)之间,平均值为1928.58 mg·kg^(-1)和2068.40 mg·kg^(-1).湖泊沉积物TN、NH^(+)_(4)-N、硝态氮(NO^(-)_(3)-N)和有机氮(Org-N)含量均表现为冬季>夏季,而河流沉积物TN平均含量为冬季<夏季,NH^(+)_(4)-N和NO^(-)_(3)-N则表现为冬季>夏季,表明河流沉积物在季节上的分布规律更为复杂;空间上,冬夏两季沉积物NO^(-)_(3)-N表现为湖泊>河流,NH^(+)_(4)-N含量则表现为湖泊<河流.C/N结果表明研究区域沉积物有机质主要来源于内源污染;(3)湖泊和河流沉积物超过60%点位属于有机氮污染Ⅳ水平,即存在有机氮污染,而超过70%和54.55%的湖泊和河流沉积物处于有机指数Ⅱ类水平,即较清洁水平,表明镇江市河湖沉积物主要为氮素污染.以上研究结果将为镇江市河流水体及沉积物氮素控制提供重要的基础数据.

Zhenjiang City is located in the intersection of the Yangtze River and the Beijing-Hangzhou Grand Canal,which is the most important water transportation hub in China,with abundant water resources and a dense river network.In recent years,the water quality in this region has declined with the rapid development of the economy and enhanced anthropogenic activity.Therefore,it is crucial to understand the state of water and sediment pollution in rivers and lakes of Zhenjiang City,which can provide important basic data for improving the water environment quality for this region.In total,21 sampling sites (including 10 sites from Jinshan Lake and 11 sites from the ancient canal) in Zhenjiang City were selected,and overlying water and sediment samples were sampled in winter and summer,respectively.In addition,the physical and chemical parameters of overlying water and sediment samples were determined,respectively,and the organic index as well as organic nitrogen index were analyzed in order to evaluate the degree of sediment contamination in this region.Results showed that (1) The TN concentration of overlying water changed from 1.95 mg·L^(-1)to 15.71mg·L^(-1)in the winter and from 0.64 mg·L^(-1)to 12.09 mg·L^(-1)in the summer,with mean values of 4.01 mg·L^(-1)and 4.07 mg·L^(-1),respectively,which are higher than those of the surface waterⅤclass standard.In addition,the ranked order of NH^(+)_(4)-N was as follows:winterlake;(2) the TN content in the sediment samples ranged from 394.61 mg·kg^(-1)to 3 288.09mg·kg^(-1)and from 869.21 mg·kg^(-1)to 3 598.04 mg·kg^(-1),respectively,with the mean values of 1 928.58 mg·kg^(-1)and 2 068.40mg·kg^(-1).The ranked order of TN,NH^(+)_(4)-N,NO^(-)_(3)-N,and Org-N was as follows:winter>summer for lake sediment samples.For river sediment samples,the ranked order of TN was wintersummer,indicating more complicated seasonal distribution for river sediment.In addition,the NO^(-)_(3)-N content was higher in lake sediment than in river sediment,whereas that of NH^(+)_(4)-N was higher in river sediment than in lake sediment.The C/N ratio results indicated that the organic matter in sediments primarily resulted from endogenous pollution in this region;(3) Results of organic nitrogen index confirmed that 60%sediment samples from the lake in winter and the river in summer belong to theⅣpollution level,indicating that organic nitrogen pollution existed in these samples.The results of organic index confirmed that 70% and 54.55%sediments samples belong totheⅡpollution level,indicating that the sediments were not severely polluted in rivers and lakes of Zhenjiang City.The results demonstrate that sediments in rivers and lakes of Zhenjiang City are mainly polluted by nitrogen.Our findings provide important basic data for nitrogen control schemes in river water and sediment in Zhenjiang City.