闽江下游及河口溶解无机氮的季节分布及组成

Seasonal Distribution and Composition of Dissolved Inorganic Nitrogen in the Min River Downstream and the Estuary

为研究闽江下游及河口区溶解无机氮(DIN)的季节分布及组成,采集并分析了四季的表层水样。平面分布上,NO3-N不同季节有所不同;NH4-N及NO2-N不同季节分布特征基本一致,仓山区、鼓楼区附近的站位受城市污水影响而含量偏高。季节变化上,NO3-N南北段春季最高,河口段冬季最高;NH4-N南北段秋季远高于其它三个季节,河口段季节变化不大;NO2-N南北段及河口段季节变化不大。DIN组成上,南北段不同季节占比相似,DIN组成上未达到热力学平衡;河口段DIN组成季节变化不大,三态间基本达到热力学平衡。DIN[2]转化上,北段三氮之间相关性总体较弱,且与DO的相关性变化较大,三氮关系受复杂的来源、人类活动及生物化学过程影响;南段三氮之间的相关性较显著也较复杂;河口段三氮及DO之间的关系季节差异比较明显。此外,闽江下游及河口DIN年际增高及超标现象较严重。

In order to study the seasonal distribution and composition of dissolved inorganic nitrogen in the Min River downstream and estuary, surface water samples were collected at 28 stations in four seasons. According to the results, the distribution of NO3-N was different in different seasons. The distribution of NH4-N and NO2-N in NT (north tributary) and ST (south tributary) were basically the same in different seasons and the concentrations varied in a small range in ET. In terms of DIN composition, the percentages of different N species was similar between NT and ST, but the average percentage of NH4-N in ST was far higher than NT due to the different terrestrial input;the composition of DIN in NT and ST didn’t reach the thermodynamic equilibrium. In ET, the composition of DIN has reached the thermodynamic equilibrium. In terms of DIN transformation, the correlations between different N species were insignificant and the correlations between DIN and DO were varied a lot from season to season in NT, such phenomenon indicated the relationships between different N species were effected by complicated nitrogen sources, human activities and biochemical processes. In ST, the correlations were more significant but more complicated than NT, it indicated that the relationships between different N species were controlled by plant uptake, ammoniation and nitrification. In ET, the seasonal differences of the correlations were significant. Moreover, the excess and annual increase of DIN concentrations was quiet serious in the Min River downstream and the estuary.