喀斯特地区供水水库营养演化历史重建

利用²¹⁰Pb-¹³⁷Cs年代学方法，结合洪水事件沉积层，综合建立了红枫湖沉积岩芯准确的年代学模型.在此基础上，通过测定沉积物多种地球化学指标（LOI、TOC、TN、C/N比、δ¹³C_org、BSi），结合历史文献记录和已有的水质监测数据，重建了1960~2016年红枫湖营养状态变化历史.结果表明，建库以来红枫湖水体经历了多次营养状态的显著转换.其中，1991年开始水体逐渐从中营养转向富营养化状态，主要是人类活动引起的内、外源营养物质输入显著增加所致，特别是网箱养鱼活动可能起到重要作用；2000年开始，水体逐渐转向中营养化，主要是一系列保护和治理措施的实施；2004年开始，水体再次逐渐恶化，转向富营养化状态，主要是外源污染物输入增加，加上内源底泥营养物质的重新释放；2009年以来，水质逐渐改善，处于中营养化状态，主要是外源污染得到有效控制，但表层营养物质含量较高，现阶段在减少外源污染物输入的同时，应重点加强底泥污染物的治理工作.

Reconstruction of trophic state changes in a karst water-supply reservoir

Based on ²¹⁰Pb-¹³⁷Cs dating and historical flood event records, we established an accurate chronology of a lake sediment core taken from the center of South Lake, the south part of Lake Hongfeng. On the basis of this chronology, the variations in the trophic status of Lake Hongfeng from 1960 to 2016AD were reconstructed by a comprehensive analysis of geochemical measurements (e.g. loss on ignition (LOI), total organic carbon (TOC), total nitrogen (TN), C/N ratio, stable carbon isotope of organic material (δ¹³C_org), and biological silicon (BSi)), water quality parameters, and reference data. During the analyzed period, several significant changes in primary productivity and trophic status were identified. From 1991 to 1999, the trophic status had gradually evolved to eutrophication and primary productivity had been increasing consistently, this was caused by enhanced anthropogenic nutrients inputs, especially cage fish culture, which might have played an important role in this eutrophication. From 2000 to 2003, due to the implementation of a series of protection and regulation policies, the trophic status had gradually changed to mesotrophic and primary productivity was decreasing gradually. From 2004 to 2008, the trophic status reversed to eutrophication, which corresponds to the increasing of exogenous nutrients input and re-emission of deposited nutrients. Since 2009, Lake Hongfeng had been mesotropher after much stricter water quality control policies had been implemented. Though water quality had been improved significantly, the nutrients content was still on a relatively high level due to the consistent re-emission, which demonstrated that future treatment should not only focus on the reduction of exogenous pollutants, but also the containment of the endogenous sediments.