大气湿沉降对长江口水域营养盐的贡献

Contribution of Atmospheric Wet Deposition to Nutrients in the Yangtze Estuary

为研究我国长江口大气湿沉降对近海水域营养盐的贡献,2004年6月-2005年5月于长江口水域崇明岛收集31个大气湿沉降样品,采用分光光度法测定溶解性NH4^＋、NO3^-、NO2^-、PO4^3-和SiO3^2-。结果表明,大气湿沉降中营养盐月平均浓度变化较大,NH4^＋和NO3^-浓度较高。营养盐湿沉降通量具有明显的季节性,总无机氮（TIN）、PO43^-和SiO3^2-的湿沉降通量分别为52.02、0.17、0.10mmol/（m^2·a）,NH4＋是TIN的主要贡献者,占TIN的70.9%。由于大气湿沉降中营养盐的浓度和组成比例与长江口表层海水有显著的差别,可使海水表层的营养盐结构、盐度、pH等发生改变,从而影响到浮游植物生长和种群结构,甚至会引发赤潮。

The 31 wet deposition samples were collected at Chongming Island from June 2004 to May 2005 in the Yangtze Estuary, and dissolved species of nutrients （ NH4^＋ , NO3^- , NO2^-, PO4^3- and SiO3^2-） in the rainwater were analyzed by Speetrophotometry. The results showed that there were significant differences among monthly average concentration of nutrient elements, and the nitrogen content in the rainwater was rather high. The wet deposition flux was 52.02 mmol/（m^2·） for the total inorganic nitrogen （TIN）, 0.17 mmol/（m^2·a）for phosphate and 0.10 mmol/（m^2·a）for silicate. The wet deposition fluxes for TIN were larger than that for PO4^3- and SiO3^2- . NH4^＋ was the dominant form of TIN, occupying 70.9% of TIN. The proportion of nutrients in the wet deposition and seawater had obvious differences. The rainwater can change the nutrients structure, salinity, pH, phytoplankton production and biologic community in the surface seawater, and this phenomenon may lead to the red tide directly.