鄱阳湖表层沉积物有机碳、氮同位素特征及其来源分析

通过对鄱阳湖及其主要入湖河流(赣江、抚河、信江、修水及饶河)15个表层沉积物样品中有机碳(TOC)、氮(TN)、C/N值、δ13C及δ15N含量的测定,分析探讨了鄱阳湖及其主支流沉积物有机质和氮素来源.结果表明:鄱阳湖湖区表层沉积物中TOC的含量(干重)在0.63%~1.86%之间,平均值为(1.15±0.35)%(n=9),比其主支流TOC含量高; TN含量变化范围为0.06%~0.16%,平均值为(0.10±0.03)%(n=9),各入湖河流表层沉积物有机质TN含量处在0.03%~0.08%之间,平均值为(0.06±0.02)%(n=6).鄱阳湖湖区沉积物中有机质的碳、氮稳定同位素变化范围分别为-25.66‰~-12.56‰和3.51‰~6.27‰,平均值分别为(-22.48±4.10)‰和(4.71±0.95)‰(n=9).各入湖河流沉积物δ13C和δ15N值含量范围分别为-25.24‰~-19.55‰和0.94‰~4.64‰,平均值分别为(-23.27±2.42)‰和(3.19±1.30)‰(n=6).有机质来源分析表明:土壤有机质、水生维管束植物和浮游植物是鄱阳湖及其主要入湖河流沉积有机质主要的3种来源,其中土壤有机质的贡献最大;土壤有机质和人工合成肥料是其沉积物氮素主要来源,对于入湖河流来说,人工合成肥料贡献更大.

Compositions and sources of stable organic carbon and nitrogen isotopes in surface sediments of Poyang Lake.

Fifteen surface sediment samples from the Poyang Lake and its main tributaries (Ganjiang River, Fuhe River, Xinjiang River, Xiushui River and Raohe River) were used to investigate organic carbon and nitrogen isotopes. In addition, the sources of organic matter and nitrogen in the surface sediments were analyzed. The total organic carbon (TOC) content in the lake, averages (1.15±0.35)% (n=9) in a range of 0.63% to 1.86%, was higher than that of its main tributaries. The total nitrogen (TN) content in the Poyang Lake area and its main tributaries was in the ranges of 0.06%~0.16% and 0.03%~0.08% with an average value of (0.10±0.03)% (n=9) and (0.06±0.02)% (n=6), respectively. The organic carbon isotope composition (δ13C) ranged from -25.66‰ to -12.56‰ (average (-22.48±4.10)‰), whereas the nitrogen isotope composition (δ15N) was from 3.51‰ to -6.27‰ (average (4.71±0.95)‰) in the Poyang Lake area surface sediments. The δ13C and δ15N values ranged from -25.24‰ to -19.55‰ (average (-23.27±2.42)‰) and 0.94‰ to 4.64‰ (average (3.19±1.30)‰) in the main tributaries surface sediments, respectively. Soil organic matter, aquatic vascular plant and phytoplankton were the main sources of the sediment organic matter in the Poyang Lake and its main tributaries, while the contribution of soil organic matter was biggest. The sources of nitrogen in the sediment were mainly from soil organic matter and synthetic fertilizer. The contribution of synthetic fertilizer was found to be a significant source for the tributaries sediment.