我国典型城镇化滨海小流域水体环境与生态耦合响应机制

This project aims to explore environmental and ecological responses to urbanization at a small watershed scale. The project will run a long term monitoring of environmental quality and ecological indicators (microbial community structure and nitrogen cycle) in surface water and sediment in a typical urbanizing small watershed in southern Chinese coast. It aims to characterize the spectrum of contaminants and possible coupling mechanisms between environmental quality and ecological function in response to urbanization, integrating with the natural abundance stable isotope fingerprints of typical contaminants (Pb and NO3--N). The temporal-spatial pattern of environmental quality and ecological function shifts will be explored with scenario analysis of rain events on the composition and level of contaminants instream. The small watershed consists of five sub-watersheds with varying levels of urbanization. The urbanization gradient in the watershed makes it possible to quantify shifts in environmental quality and ecological function in response to urbanization. The project will provide a valuble methodology for studying urbanization impacts on environmental and ecological degradation at a watershed scale. The findings from the project will contribute to the development of environmental and ecological management and practices in urbanizing watersheds.

本申请项目以小流域城镇化进程的环境和生态耦合响应机制为主题，通过对城镇化进程中的南方典型滨海小流域水体地表水与沉积物环境质量和以微生物群落与氮循环为生态响应指标的长期定位监测，结合典型污染物（Pb和NO3--N）稳定性同位素指纹等技术，研究城镇化进程中小流域地表水和沉积物污染物谱与负荷水平及其时空变异，揭示环境质量变化与生态响应的耦合关系；以降雨事件为情景分析，结合景观单元土壤源典型污染物与雨水径流输入典型污染物间多源贡献模型计算，阐释城镇化小流域景观单元和景观格局历史变化对水体污染物谱及其输入的影响机制。供试典型小流域由五个不同城镇化水平的次级流域组成，构成流域城镇化梯度，得以定量或半定量化研究环境质量和生态功能的城镇化效应。本研究将为流域城镇化环境和生态退化研究提供方法论，并为城镇化流域环境和生态管理提供科学依据。

本项目以南方典型滨海小流域为对象，在原有长期监测平台的基础上，应用流域研究法和梯度研究法相结合，研究了流域城镇化过程对流域多介质环境质量退化的驱动，揭示了流域内源和由大气输入外源污染物对流域环境质量退化的贡献。结合Pb稳定性同位素组成分析技术，城镇化过程使流域地表水、沉积物和土壤重金属负荷下降，但经污染大气输入的相关污染物在流域上游被山体阻挡沉降，引起上游环境介质特征重金属水平上升。地表水氮磷浓度受大气沉降影响，尤其受无雨期长短调控。而研究流域下游因开发扰动土壤表面，导致相关子流域沉积物颗粒大小中值增大，该单一指标可灵敏地表征区域开发强度。流域表层土壤和各子流域沉积物的氮循环连续过程活性表明，流域土壤氨化作用强于硝化作用，导致各子流域地表水以氨态氮为主；但可能由于研究流域环境介质重金属污染水平较低，氮循环活性未表现出土壤、地表水和沉积物的耦合关系，即与本项目申请假设不一致，更为敏感表征人类活动对生态功能退化的生态学或生物学指标有待进一步发掘和研究。本项目完成为流域尺度人类活动的环境影响研究提供了有效的研究方法论。