洪泽湖表层沉积物氮形态分布及影响因素

Distribution and Influence Factors of Nitrogen Form in Surface Sediment of Lake Hongze

为探究洪泽湖不同区域沉积物中各形态氮的分布特征及影响因素,文章采用分级浸取的方法将沉积物中氮分为离子交换态氮(IEF-N)、弱酸可浸取态氮(WAEF-N)、强碱浸取态氮(SAEF-N)、强氧化剂浸取态氮(SOEF-N)和非转化态氮(NTN),并运用多元统计分析研究沉积物的理化性质与各形态氮的关系。结果表明:沉积物可转化态氮(TTN)的含量为377.84~1 085.08 mg/kg,均值为765.93 mg/kg,占总氮(TN)的69.76%,是总氮的主要组成部分,洪泽湖沉积物中氮具有较高的潜在释放风险。各类可转化态氮的含量大小顺序为WAEF-N>SOEF-N>SAEF-N>IEF-N。IEF-N与TN的相关性较低,说明沉积物中TN高低并不一定能代表湖泊内源氮污染释放程度的高低。除了IEF-N和SAEF-N,其余形态氮的空间分布特征均与TN一致,即西湖区>成子湖等中部湖区>东部敞水区。TTN、SOEF-N、NTN分别与TOC、TN均具有极显著相关性(p<0.01),IEF-N与TOC、pH均具有显著相关性(p<0.05),粒度与各形态氮之间的相关性不显著。

A sequential extraction method was employed to determine and divide nitrogen forms into ion exchangeable form nitrogen(IEF-N), weak acid extractable form nitrogen(WAEF-N), strong alkali extractable form nitrogen(SAEF-N), strong oxidant extractable form nitrogen(SOEF-N) and non-extractable form nitrogen(NTN), in sediments from different areas of Lake Hongze for exploring its distribution characteristics and influence factors of various forms of sediment nitrogen.Moreover, multivariate statistical analysis was used to investigate the relationship between physical and chemical properties of sediments and various forms of nitrogen. The results showed that the transferable total nitrogen(TTN) content in the sediments ranged from 377.84 mg/kg to 1085.08 mg/kg with a mean value as 765.93 mg/kg, accounting for 69.76% of the total nitrogen(TN). TTN was a main part of TN, indicating the nitrogen in sediment of Lake Hongze has a high potential release risk. The sequence of each transformable nitrogen according to concentration was WAEF-N>SOEF-N>SAEF-N>IEF-N.The low correlation between IEF-N and TN suggested that TN in sediments cannot totally represent the release extend of endogenous nitrogen pollution in lake. The spatial distribution trends of all nitrogen forms but IEF-N and SAEF-N were consistent with that of TN, following as West Lake Area>Central Lake Area Including Lake Chengzi>Eastern Open Water Area. TTN, SOEF-N and NTN are extremely significantly correlated with TOC and TN, respectively(p<0.01), and IEF-N is significantly correlated with TOC and pH, respectively(p<0.05). Particle size had a weak correlationship with all different nitrogen forms.