三峡库区水体中可溶性C、N变化及影响因素

Change and Influencing Factors of Dissolved Carbon and Dissolved Nitrogen in Water of the Three Gorges Reservoir

为了解三峡库区水体中可溶性C、N的变化,本研究于2011年3月至2012年8月在三峡水库涪陵段进行了每周一次的水样采集,分析其中可溶性C、N成分的变化及其来源特征.结果表明,库区水中DOC浓度范围为0.64~9.07 mg·L^(-1),且有明显的季节变化,表现为:夏季>春季、秋季>冬季,DOC年入库总量为1.78×109kg,入库量具有与浓度相似的季节变化趋势;DTN的浓度范围为2.59~4.35 mg·L^(-1),春季>冬季>夏季>秋季,年入库总量为1.32×109kg,入库量的季节变化特征:夏季>秋季>春季>冬季,其中DON、NO-3-N分别占DTN的30.35%~63.45%、35.87%~67.72%.DOC受降水和温度的影响明显,水中DOC主要来自外源输入,春季、夏季降雨径流其外源输入量增加,而秋季、冬季则内源贡献有所增加;DTN受人为排放和水体稀释的影响相对较大.相关分析表明,DOC与DON呈显著负相关(P<0.05),通常以DOC/DON比值反映水中DOM的来源,库区DOC/DON范围为0.35~7.28,DOM来源具有明显的季节特征.夏季DOC/DON较高,DOM主要来自流域侵蚀;冬季DOC/DON较低,DOM主要来自生活污水排放和内源现场产生;春季、秋季DOC/DON介于两者之间,DOM来源包括流域侵蚀、生活污水排放及现场产生等.

In order to understand the changes of dissolved carbon and dissolved nitrogen in the water of Three Gorges Reservoir, this research was carried out once a week by the bank of Yangtze River in Fuling beach from March 2011 to August 2012, and the variation characteristics of dissolved C, N composition and their source were analyzed. The results showed that the concentration of DOC ranged from 0.64 mg· L^-1 to 9.07 mg· L^-1 , and had obvious seasonal change ： summer 〉 spring and autumn 〉 winter. Annual total input of DOC was 1.78 × 10^9 kg, the seasonal change trend of the total input of DOC was similar to that of the concentration of DOC; The concentration of DTN ranged from 2.59 mg· L^-1 to 4.35 mg· L^-1： spring 〉 winter 〉 summer 〉 autumn, annual total input was 1.32 × 109 kg,the seasonal input changed in the order of summer 〉 autumn 〉 spring 〉 winter, among them DON, NO3- -N accounted for 30. 35% -63.45% and 35.87% -67.72% , respectively. DOC was affected by precipitation and air temperature, and mainly came from the exogenous input, in the spring and summer its exogenous input increased with the increase of rainfall runoff, but in the autumn and winter the endogenous contribution increased; DTN was relatively affected by human emissions and water dilution. Correlation analysis showed that there was a significant negative correlation between DOC and DON （P 〈 0.05） , DOC/DON ratio usually reflects the source of the DOM, the DOC/DON in the water of three gorges reservoir ranged from 0.35 to 7.28, the source of DOM had obvious seasonal characteristics. DOC/DON was the highest in summer, and the DOM mainly came from watershed erosion; DOC/DON was the lowest in winter, and the DOM mainly came from living sewage and endogenous field; the DOC/DON ratios in spring and autumn were higher than those in winter and lower than those in summer, and the DOM sources included watershed erosion, living sewage and endogenous field.