寒旱区湖泊冰封期有机碳氮同位素研究

为了探究寒旱区湖泊悬浮物和沉积物中颗粒有机碳氮稳定同位素来源与环境相关性，于2019年1月对南海湖冰封期悬浮物和表层沉积物有机δ¹³C、δ¹⁵N及C/N值进行了测定.结果表明：南海湖冰封期悬浮有机质δ¹³C的变化范围为-31.94‰~-27.87‰，δ¹⁵N变化范围为15.16‰~18.66‰，C/N变化范围为3.90~5.13.沉积物δ¹³C值变化范围为-25.39‰~-18.83‰，δ¹⁵N值变化范围为7.04‰~13.66‰，C/N值变化范围为7.66~12.23.悬浮有机质δ¹³C和δ¹⁵N最高值分别出现在进水口区和湖心岛区，沉积物则都为湖心岛区表层沉积物.端元混合模型分析表明，冰封期悬浮有机质主要由内源水生藻类主导，水质保护区藻类贡献率达到82.33%，与该区域浮游植物丰度最高相符.表层沉积物有机质的主要来源为内源水生植物，在水质保护区贡献率高达89.7%.相关性分析表明，在冰封期内悬浮有机质与表层沉积物δ¹³C、δ¹⁵N并没有明显的相关性，在低温情况下悬浮物δ¹⁵N与温度（P<0.025）、硝态氮（P<0.019）呈显著负相关，与亚硝态氮呈显著正相关（P<0.034）.原因主要与外源贡献率和生物作用的同位素效应有关.悬浮物δ¹³C和COD呈极显著正相关（P<0.008），与盐度呈显著正相关（P<0.046），COD和悬浮物δ¹³C很可能具有同源性，在湖泊冰封期具有一定的环境指示意义.

Organic carbon and nitrogen isotopes of lakes in cold and arid region during the frozen period

In order to explore the environmental significance of the particulate organic as the source of stable isotopic carbon and nitrogen in suspended solids and sediments of the Lake in cold and arid regions, the contents of δ¹³C, δ¹⁵N and C/N ratio of suspended solids and surface sediments in Nanhai Lake during the ice-sealing period were determined in January 2019. The results showed that, δ¹³C, δ¹⁵N, C/N in the suspended organic matters varied in the range of -31.94‰~-27.87‰, 15.16‰~18.66‰, and 3.90~5.13, respectively, while in the sediments varied in the range of -25.39‰~-18.83‰, 7.04‰~13.66‰, and 7.66~12.23, respectively. The peak values of the δ¹³C and δ¹⁵N contents in the suspended organic substances appeared in the water entering area and the islands in the center of the lake, respectively, while in sediments, both the peak values appeard in the latter. The end-member mixing model showed, the suspended organic matter in the frozen period was mainly originated from the endogenous aquatic algae, which contributed 82.33% of the total suspended organic matters in the water conservation area, being consistent with the highest abundance of phytoplankton in the area. The main source of organic matters in the surface sediments was endogenous aquatic plants, which contributed 89.7% of the total organic matters in the water conservation area. Analyses showed that there was no significant correlation between suspended organic matter and δ¹³C, δ¹⁵N in the surface sediments during the freezing period. At low temperature, there exist significant negative correlation between the suspended δ¹⁵N and temperature (P<0.025) as well as nitrate nitrogen (P<0.019), positive correlation between the suspended δ¹⁵N and the nitrite nitrogen (P<0.034). These maybe due to the exogenous contribution rate and the isotopic effect of biological action. There was an extremely significant positive correlation between δ¹³C and COD in suspended matter (P<0.008), and a significant positive correlation between δ¹³C and salinity (P<0.046). The COD and suspended ¹³C are likely to have homology and have a certain environmental indication in the lake ice-sealing period.