滇池流域营养盐沉积百年历史重构及源解析

Historical Reconstruction and Source Analysis of Nutrient Deposits over the Past 100 Years in Dianchi Lake Basin

以滇池流域双龙库区为研究靶区,对水库0~70 cm深沉积物柱进行放射性核素、营养盐及碳稳定性同位素的分析,结合定年结果及人类活动历史变化,解析沉积物中营养盐历史演变及其对人类活动的响应,追溯沉积物有机质来源,进行有机污染的评价。结果表明,(210)^Pb_(ex)比活度随深度增加呈现衰减趋势并具有一定的负向指数拟合关系,而沉积速率略有波动整体呈上升趋势,记录了双龙地区1860年以来的沉积历史。沉积柱中各营养盐浓度分别为总氮(TN)为0.58×10^(3)~4.54×10^(3)mg/kg;总磷(TP)为0.12×10^(3)~0.55×10^(3)mg/kg;总有机碳(TOC)为0.49%~4.34%。剖面变化趋势均呈自上而下递减,沉积物营养盐浓度的增加与不同时期人类活动密切相关,反映了建库前后人为活动对生态环境演变的影响。根据C/N(4.39~9.57)和δ^(13)C(-24.96‰~-21.36‰)两者结果可以推断有机质来源为陆生C_(3)植物与内源混合输入。利用有机指数和有机氮指标评价沉积物污染的历史变化,表明双龙水库20世纪60年代后始终存在有机氮污染。且随着近年人类活动加剧,有机指数和有机氮增加,水质恶化严重。

In this study,the sediment samples collected from the Shuanglong Reservoir were analyzed for the concentrations of(210)^Pb_(ex),;Cs,total organic carbon(TOC),total nitrogen(TN),total phosphorus(TP)and stable isotopes(δ^(13)C).The distribution characteristics with depth and impact factors were discussed.The level of organic pollution in studied area,sources of organic matter and nitrogen were analyzed.Results showed that the;Pb concentration decreased with depth and a negative exponential curve fitting(R^(2)=0.520)was found.The accumulation rate presented an increase trend and being affected by human activities significantly.The concentration of TN was between 0.58×10^(3)and 4.54×10^(3)mg/kg.The TP concentration ranged from 0.12×10^(3) to 0.55×10^(3)mg/kg.The TOC concentration was within 0.49%to 4.34%.The nutrient contents were much higher in the surface layers(0-15 cm)and decreased with depth.The increase in nutrient concentrations were closely related to the intensive human activities.The results of C/N andδ^(13)C suggested that endogenous plankton and terrestrial C_(3) plants might be the main source of sedimentary OM.The pollution index evaluation was also applied in the Shuanglong Reservoir.According to the results of organic index and organic nitrogen index,the historical changes in pollution states have been revealed.Through the organic nitrogen index,it stayed level IV,reflecting the serious organic nitrogen pollution level in the Shuanglong Reservoir.Moreover,the tendency towards worsening environmental pollution recently,with the intensifying human activities.