安徽省石塘湖过去百余年湖水总磷浓度的定量重建

Quantitative Reconstruction of the History of Total Phosphorus Concentrations in Shitang Lake,Anhui Province Over the Past 100 Years

湖水总磷浓度对湖泊富营养化有很好的预警作用,历史湖水总磷浓度的定量重建能揭示湖泊营养演化历史。依据安徽省石塘湖沉积物钻孔的高分辨率硅藻研究结果,结合长江中下游湖泊硅藻-总磷转换函数模型,定量重建了其过去百余年来硅藻组合演替与历史湖水总磷浓度的变化过程。结果表明:石塘湖硅藻经历了从颗粒直链藻(Aulacoseira granulate)优势组合(1867—1981年)向富营养属种高山直链藻(Aulacoseira alpigae)优势组合(1981年以来)的变化。1981年以前,水体ρ(总磷)为50～60μg.L-1,湖泊一直维持在中等营养水平;1981年之后水体ρ(总磷)呈现明显升高趋势(>100μg.L-1),硅藻组合以高山直链藻占绝对优势,同时伴有喜好富营养环境的属种如极微小环藻(Cyclotella atomus)、梅尼小环藻(Cyclotella meneghiniana)、谷皮菱形藻(Nitzschia palea)和汉斯冠盘藻(Stephanodiscus hantzschii)等的增加,标志着湖泊富营养化的发生。20世纪80年代以来,农业及城市生活污水排放、农业化学肥料的大量使用以及过度养殖是硅藻种群转变和富营养化发生的主要根源。增温在一定程度上也影响着硅藻群落变化和富营养化的加重。根据重建的硅藻-水体总磷浓度结果,提出石塘湖治理的营养物基准水体ρ(总磷)为60μg.L-1,为该湖整治和修复方案的制定提供可参考的目标,也为当地大量类似湖泊的治理提供重要参考。

Total phosphorous （TP） concentration is a good indicator of lake eutrophication, and quantitative reconstruction of the history of variation of TP concentration of water in the lake may reveal the history of nutrient evolution of the lake. Based on the high-resolution study of diatom fossil in drill cores of sediments in that lake coupled with the functional model for diatom-TP conversion for lakes in the middle and lower reaches of the Yangtze River, succession of diatom composition in and history of nutrient evolution of the Shitang Lake was quantitatively reconstructed. Results show that diatom flora experienced change from Aulacoseira granulata-dominated composition （prior to 1981 ） to Aulacoseira alpigaedominated one （ after 1981 ）. Prior to 1981, TP concentration remained around 50-60 μg · L^-1, indicating a medium nutrition level, while after 1981, TP concentration increased rapidly to 〉100 μg · L^-1 , and the diatom community was dominated by A. alpigae accompanied with an increasing proportion of eutrophy-phil diatoms, such as Cyclotella atomus, Cyclotella meneghiniana, Nitzschia palea, Stephanodiscus hantzschii, which indicated the beginning of eutrophication of the lake. Since the 1980s increasing discharge of domestic sewage, application of chemical fertilizers and expansion of aquaculture have become the major causes of the eutrophication and the change in diatom flora. To a certain extent, the global warming is another contributor. On the basis of the findings, the TP of 60 μg · L^-1 is proposed to be the baseline for management of eutrophication of the Shitang Lake. This study also offers reliable reference for setting up targets for management and remediation of the lake and a large number of similar lakes in this area.