洞庭湖表层沉积物营养盐空间分布及来源解析

在洞庭湖设置20个采样点,测定表层沉积物中总氮(TN)、总有机碳(TOC)和总磷(TP)浓度,分析营养盐浓度的空间分布特征,采用有机指数评价沉积物有机污染水平,并根据碳氮比(C/N)、 ¹⁵N同位素比例(δ ¹⁵N)解析沉积物中有机质来源。结果表明:洞庭湖表层沉积物TOC、TN及TP浓度平均值分别为13 260、1 046和368.85 mg/kg,不同营养盐浓度空间分布存在明显差异,但均呈现自西洞庭湖向东洞庭湖和南洞庭湖递减的趋势;洞庭湖表层沉积物20%采样点存在有机氮污染,但表层沉积物整体为清洁至尚清洁,未达到有机污染水平;表层沉积物C/N均值为13.22,沉积物中有机质主要来自外源输入;δ ¹⁵N解析进一步表明,陆域土壤中有机质是沉积物有机污染的主要来源,建议加强陆域土壤有机质流失的控制。

Spatial distribution and source analysis of surface sediment nutrients in Lake Dongting

A total of 20 samplings site were set in Lake Dongting to measure the concentrations of TOC, TN and TP in the surface sedeiments of the lake. The spatial distribution characteristics of nutrient concentration were analysed, the organic index was used to evaluate the organic pollution level of the sediments, and the source of organic matter in sediments were analysed according to C/N ration and 15N isotope ratio(δ 15N). The results showed that the average concentrations of TOC, TN and TP in the surface sediments of Lake Dongting were 13 260, 1 046 and 368.85 mg/kg, respectively. The spatial distributions of different nutrient concentrations were significantly different, but they all showed a decreasing trend from West Lake Dongting to East Lake Dongting and South Lake Dongting. Organic nitrogen pollution existed in 20% of surface sediments of Lake Dongting, but the overall surface sediments were clean to relatively clean, not up to the level of organic pollution. The average C/N ration value of the surface sediments was 13.22, and the organic matter in the sediments was mainly from the exogenous inputs. The analysis of δ 15N further indicated that organic matter in land soil was the main source of organic pollution in the sediments. It was suggested to strengthen the control of soil organic loss in land areas.