九龙江口湿地表层沉积物氮的形态分布特征

利用连续提取法对九龙江口湿地表层沉积物中不同形态氮含量进行了测定,探究了滨海湿地表层沉积物中氮形态及其与沉积物理化性质的相关关系.结果表明:九龙江口滨海湿地沉积物中w(TN)达到12.67 mg/g,可转化态氮(EFN)质量分数〔w(EFN)〕占w(TN)的18.78%.有机硫化物结合态氮(OSFN)和碳酸盐结合态氮(CFN)是九龙江口滨海湿地沉积物EFN的主要形态,w(OSFN)和w(CFN)分别占w(EFN)的37.82%和36.97%.不同潮水位和植被类型沉积物中的w(TN)和w(EFN)呈现差异性,表现为高潮位>中潮位>低潮位,红树林>其他植被类型(北部互花米草、红树与互花米草混交和南部互花米草)>光滩.w(CFN),w(OSFN),w(EFN)和w(TN)存在显著相关关系,表明w(TN)和w(EFN)的增加主要来源于OSFN和CFN.w(OSFN),w(EFN)和w(TN)与w(OM)存在显著相关关系,表明河口滨海湿地有机质的累积、矿化,可增加沉积物中的w(OSFN),w(EFN)和w(TN),从而对滨海湿地氮生物地球化学过程产生重要影响.

Distribution Characteristics of Nitrogen Forms in Surface Sediments of Jiulongjiang Estuary Wetland

To examine the correlation between nitrogen forms and physicochemical properties of surface sediments in urban coastal wetlands,using the Jiulongjiang estuary wetland as a case study,the amount of each nitrogen form in the surface sediments was determined based on nitrogen fractions isolated by sequential chemical extraction.The results showed that total nitrogen(TN) content of the sediments was 12.67 mg g,and the mass percentage of the exchangeable form nitrogen(EFN) in the TN of the sediments was 18.78%.Organic sulfide form nitrogen(OSFN) and carbonate form nitrogen(CFN) were the predominant forms of the EFN,of which the percentages were 37.82% and 36.97%,respectively.Significant differences in both the TN and EFN contents of the sediments were observed among different tidal levels and vegetations,which showed that high tidal level > medium tidal level > low tidal level,and mangrove > spartina and mixed spartina mangrove plantation > bare mudflat.The contents of CFN,OSFN,EFN,TN were significantly correlated to each other,indicating that the increased levels of TN and EFN originated from OSFN and CFN.The contents of OSFN,EFN,TN were significantly correlated to OM content,implying that the accumulation and mineralization of organic matter in this coastal wetland could increase the levels of OSFN,EFN and TN of the sediments,and then make a great impact on the nitrogen biogeochemical process in the coastal wetland.