鄱阳湖水体悬浮有机质碳氮同位素分布特征及来源探讨

通过对鄱阳湖及其入湖河流(赣江、抚河、信江、修水及饶河)水体悬浮有机质碳、氮同位素含量的测定,分析了鄱阳湖及其入湖河流水体悬浮有机质碳同位素(δ13CPOM)和氮同位素(δ15NPOM)时空分布特征,探讨了其水体悬浮有机质和氮素来源.结果表明,鄱阳湖区枯水期δ13CPOM、δ15NPOM值分布范围分别为-26.59‰~-24.91‰(n=9)和5.88‰~17.49‰(n=9),丰水期分别为-27.10‰~-25.88‰(n=9)和2.99‰~19.69‰(n=9);入湖河流水体枯水期δ13CPOM、δ15NPOM值变化范围分别为-27.79‰~-25.22‰(n=6)和2.87‰~9.26‰(n=6),丰水期分别为-28.07‰~-26.02‰(n=6)和2.12‰~8.75‰(n=6).有机质来源分析表明:C3植物是鄱阳湖区及其入湖河流水体悬浮有机质的主要来源;而氮素来源比较复杂,在不同季节和不同的地点也不尽相同,生活污水、化肥及其土壤流失氮是鄱阳湖区水体悬浮颗粒物氮素的3种主要来源;化肥、陆源有机质及其土壤流失氮是其入湖河流水体悬浮颗粒物氮素的3种主要来源.

Distribution and sources of stable organic carbon and nitrogen isotopes in suspended particulate organic matter of Poyang Lake

Fifteen samples from the Poyang Lake and its main tributaries (Ganjiang River, Fuhe River, Xinjiang River, Xiushui River and Raohe River) were collected to analyze organic carbon and nitrogen isotopes in suspended particles. In addition, the sources of organic matter and nitrogen in the suspended particulate organic matter were analyzed. The results showed that the organic carbon isotope composition (δ13CPOM) ranged from -26.59‰ to -24.91‰(n=9) and -27.10‰ to -25.88‰ (n=9) whereas the nitrogen isotope composition (δ15NPOM) was from 5.88‰ to 17.49‰ and 2.99‰ to 19.69‰ in low water period and high water period, respectively in Poyang Lake area. In the suspended particulate organic matter of the main tributaries, the δ13CPOM values ranged from -27.79‰ to -25.22‰(n=6) and -28.07‰ to -26.02‰(n=6)whereas the δ15NPOM was from 2.87‰ to 9.26‰ and 2.12‰~8.75‰ in low water period and high water period, respectively. The C3 plants were the main sources of the suspended particulate organic matter in Poyang Lake and its main tributaries. The sources of nitrogen in the suspended particulate organic matter were complex. Domestic sewage, chemical fertilizer and soil erosion were the main sources of nitrogen in the suspended particulate organic matter in the Poyang Lake. Whereas the chemical fertilizer, terrestrial organic matter and soil erosion were the main sources of nitrogen in the suspended particulate organic matter in its main tributaries.