Eco-environmental evolutionprocess during the past century in Lake Changdang, Lake Taihu Basin

Abstract

社会经济转型产生的多重人为驱动力对太湖流域的生态环境和服务功能造成了深远的负面影响.湖泊沉积记录有助于探索流域人与环境长期相互作用过程，为生态修复提供理论支撑.本研究通过对太湖流域长荡湖沉积岩芯有机质、营养盐和重金属元素等指标的系统分析，在²¹⁰Pb定年结果的基础上，结合地球化学标准化方法以及流域人类活动资料，解析了近100年来湖泊的富营养化和重金属污染过程、特征与主要驱动因素.结果显示，长荡湖岩芯沉积指标呈相似的三阶段历史变化，1950s之前，沉积物有机碳、总氮和磷较为稳定，湖泊营养水平较低，对应人类活动影响较弱的准自然演化阶段；随后湖泊进入人为主导的过渡阶段，特别是在1970s，湖泊营养水平、藻类生产力以及重金属污染程度（Cd>>Sb>Cu≈Pb≈Zn）均显著升高，直接受到流域人口增加、农业集约化、工业化和城镇化导致的污染排放的影响.1980s以后，类似于太湖流域大多数湖泊，长荡湖已经大幅偏离自然演化基线，处于高度富营养化、重污染的状态，威胁流域生态安全.本研究进一步指出，深入理解湖泊生态环境历史演变过程及人为影响有助于湖泊-流域系统的可持续管理.;Multiple anthropogenic stressors generated by the socioeconomic transitions have far-reaching negative impacts on the water environment and ecosystem services in the Lake Taihu Basin. Lake sediment records contribute to exploring the interactions between humans and the environment and supporting the ecological restoration in catchments. Based on the analyses of sedimentary organic matter, nutrients and major heavy metal elements in the core of Lake Changdang in the Lake Taihu Basin, combining with ²¹⁰Pb dating results, geochemical normalization and historical documents of human activity in the catchment, this study explored the processes, characteristics and main driving factors of lake eutrophication and heavy metal pollution over the past 100 years. The results show that multiple cores proxies have similar three-stage historical changes. Before the 1950s, sediment organic carbon, total nitrogen and phosphorus were relatively stable, and lake nutrient level was low, corresponding to the quasi-natural evolution phase with the weak influence of human activities. Subsequently, the lake entered into a transition phase dominated by human impacts. Particularly in the 1970s, lake nutrient level, algal productivity and heavy metal pollution (Cd>>Sb>Cu≈Pb≈Zn) increased significantly, which were directly affected by the pollutant discharge resulted from the increase in population, agricultural intensification, industrialization and urbanization in the catchment. Since 1980s, Lake Changdang has deviated from the natural evolution baseline and maintained a state of high eutrophication and heavy pollution, threatening the ecological security of the catchment. This study further highlights that understanding the historical process of lake eco-environmental evolution and anthropogenic impacts helps sustainable lake catchment management.