氮同位素示踪贵州红枫湖河流季节性氮污染

NITROGEN ISOTOPE STUDIES ON SEASONAL NITROGEN POLLUTION OF INFLOWING RIVERS OF HONGFENG LAKE, GUIZHOU PROVINCE

利用氮同位素技术对贵州红枫湖各输入、输出河流氮污染状况和季节性变化规律进行了研究,并通过对输入河流和输出河流的氮对比,探讨红枫湖的氮负荷变化。农业输入河流季节氮污染变化较小,以低硝酸盐、低铵盐含量为特征,其氮同位素组成较小,位于农业源范围之内(<+10‰)。工业污染河流氮污染呈干季和雨季变化:干季(冬春季)以高硝酸盐、高铵盐含量和高氮同位素组成(>+10‰)为特征,雨季(夏季)则相似于农业输入河流。因而利用氮同位素组成可以对不同类型河流氮污染源进行可靠识别。

Nitrogen isotopic technique was used to study the situation and seasonal change of nitrogen pollution in inflowing rivers and an outflowing river of Hongfeng Lake in this paper. Seasonal variations of nitrogen in agricultural-irrigation inflowing rivers are small, characterized by low concentrations of ammonium and nitrate. Their nitrogen isotopic values are lower than +10‰, reflecting an agricultural source. Different characteristics of nitrogen in dry and wet seasons were found in industry-polluted rivers. In dry seasons (Winter and Spring), industry-polluted rivers show high concentrations of ammonium and nitrate, and nitrogen isotopic values (>+10‰), while in wet seasons (summer), a similar trend was observed in these two kinds of rivers. Therefore, nitrogen isotopic composition is a reliable tool to trace nitrogen sources of rivers. Changes in nitrogen loads in Hongfeng Lake were also discussed based on the comparison of nitrogen (isotopes) between the inflowing rivers and the outflowing river.