题名：Vertical Dissolved Inorganic Nitrogen Fluxes in Marsh and MudflatAreas of the Yangtze Estuary
领域：ENVIRONMENTAL SCIENCES 三区
来源：Journal of Environmental Quality
发表年代：2014年
作者：Huanguang Deng, Dongqi Wang,* Zhenlou Chen, Jie Liu, Shiyuan Xu, and John R. White
摘要：Nitrogen (N) is a dominant macronutrient in many river-dominatedcoastal systems, and excess concentrations can drive eutrophication,the effects of which can include hypoxia and algal blooms. TheYangtze River in China transports a large amount of dissolvedinorganic N. Therefore, it is important to understand the role ofthe marsh and mudflat areas within the estuary on processing thisexogenous N load. In situ dissolved inorganic nitrogen (DIN)fluxes across the sediment–water interface were determinedmonthly at Chongming Island at two sites (a vegetated marsh andan unvegetated mudflat) and were compared with rates from apreviously published laboratory incubation study by our researchgroup. Results from the in situ study showed that NO3- flux ratescomprised the major component of total DIN flux, ranging from 55to 97%. No significant difference was observed in the N flux ratesbetween the marsh and mudflat sites. Overall, sediment at bothsites served as a sink of DIN from surface water with mean flux ratesof -178 mmol m-2 h–1 and -165 mmol m-2 h–1 for the marsh andmudflat, respectively. In general, DIN flux rates were not significantlycorrelated with DIN concentrations and other measured parameters(temperature, dissolved oxygen, salinity, and pH) of surface water.The in situ measured fluxes of NO3- and NO2- in this study werenot significantly different from those of our previous laboratoryincubation (p > 0.05), whereas NH4+ fluxes in situ were significantlylower than those from the laboratory core incubations (p < 0.05).This result suggests that caution should be used when extrapolatingrates from laboratory incubation methods to the field because therates might not be equivalent.
