天目湖沙河水库尿素含量及其时空分布特征分析

The abundance and spatial-temporal distribution of urea in Shahe Reservoir,Liyang,China

为探索尿素在淡水生态系统中的作用,于2013年3月—2014年2月调查了江苏溧阳天目湖沙河水库及中田河入库河口中,尿素氮和不同形态氮素的含量和分布特征.结果表明,沙河水库中尿素普遍存在,全库年平均尿素氮浓度为0.016 mg·L-1(0.007—0.029 mg·L-1);河、库尿素氮含量在不同月份波动较大,施肥期的2月、6月、11月含量较高,而在非施肥期含量较低,且河、库含量更加接近;沙河水库尿素氮的空间分布随季节变化而变化,一般在下游旅游集中区和上游靠近农业区出现尿素氮含量高值.此外,沙河水库溶解性氮以无机氮库为主,有机氮占29.09%,硝态氮是库体的主要氮形态;其中尿素氮占总氮、溶解性总氮、溶解性有机氮和生物可利用氮的年平均百分比分别为1.80%、2.21%、8.31%、3.54%.相关分析表明,沙河水库尿素含量与溶解氧含量呈显著负相关,与溶解性有机氮呈显著正相关.研究表明,天目湖沙河水库尿素含量的时空变化主要受外源输入(人类活动)的影响,其时间变化规律与农业活动密切相关,空间分布差异主要受污染源(河道入库口、农业、旅游业和养殖业)分布及其活动的影响.

To explore the role of urea in freshwater ecosystems, we analyzed various nitrogen contents in the water samples collected in the reservoir and Zhongtian upstream channel of Shahe Reservoir, Liyang, China from March, 2013 to February, 2014. The results showed that urea was ubiquitous in Shahe Reservoir, and the annual mean concentration of urea nitrogen in the whole reservoir was 0.016 mg·L^-1 （0.007-0.029 mg·L^-1）; Urea nitrogen content of river and lake was volatile in different moths, high in the fertilization period （February, June, and November）, and low in the non-fertilization period. Meanwhile, urea nitrogen content in reservoir was similar to that in input river during the non-fertilization season. The spatial distribution of urea nitrogen changed with the seasons, with the highest content usually appearing in downstream near tourism sites and upstream near the agricultural runoff. The dissolved nitrogen （DTN） was dominated by inorganic nitrogen, and the organic nitrogen accounted for only 29.09% of the DTN in Shahe Reservoir. Besides, nitrate was the primary nitrogen form of reservoir. The average annual percentage of urea nitrogen was 1.80% to total nitrogen, 2.21% to dissolved nitrogen, 8.31% to dissolved organic nitrogen, and 3.54% to bioavailable nitrogen. Correlation analysis showed that urea content in Shahe Reservoir was significantly negatively correlated with dissolved oxygen content, and was significantly positively correlated with dissolved organic nitrogen. This research showed that the spatial and temporal variation of urea content in Shahe Reservoir was mainly influenced by external input （human activity）. The temporal variation of urea was closely related to agricultural activity, and the differences in spatial distribution was mainly influenced by the distribution and activity of different pollution sources （river estuary, agricultural, tourism and farming）.