基于压力-状态-响应和物元可拓模型的城市河流健康评价

城市河流作为人类活动和自然过程相互作用强烈的区域,承受着人类资源开发利用和污染物排放的压力,但近些年来随着对河流健康的重视,针对城市河流实施了大量的生态治理措施。综合考虑人类正负面影响对河流健康状态的影响,进行河流健康状态的评价,对于城市河流的修复效果检验和管理保护具有重要意义。以南京市鼓楼区典型城市河流西北护城河为研究区,根据河流周边土地利用类型、物理形态差异及城市管网分布将其划分为6个河段,考虑人类修复措施对河流健康水平的影响,构建了基于压力-状态-响应(Pressure-State-Response,PSR)模型的城市河流健康评价指标体系,采用物元可拓模型确定了河段健康等级,并根据各等级综合关联度之间的距离判断河流健康水平的发展趋势。结果表明:压力、状态以及响应准则层的权重分别为0.458、0.311、0.231,压力指标为影响城市河流健康水平的主要因素;西北护城河6个河段的健康水平表现出较强的空间异质性,河段A-F的健康等级分别为中等、健康、亚健康、中等、亚病态和病态,流经公园绿地的河段健康水平明显高于流经居民住宅区的河段,河段B、C、D的健康水平有进一步提升的趋势,而河段A、E、F的健康状态则有进一步恶化的趋势,需要进行重点关注。

Health assessment of urban river based on pressure-state-response and matter-element extension model

Urban rivers, located in the strong interaction area of human activities and natural processes, are under great pressure of human resource development and utilization and pollutant discharge. In recent years, people have adopted a series of management measures to improve the health of urban rivers. However, current methods about urban river health assessment mainly focus on the pressures from human activities. The positive measures taken by humans to restore the ecology of urban rivers are usually neglected. Thus, the assessment results cannot fully reflect the real river health state and may mislead the management and protection of urban rivers. Therefore, both of the negative and positive human activities should be considered when constructing the assessment index system of urban river health, which can provide a more scientific and accurate assessment result. In this study, a typical urban river (the Northwest-Moat) in Nanjing City was selected as the study area. Considering the spatial heterogeneity of river health, we divided the Northwest-Moat into six reaches according to the river''s surrounding architecture environment, its morphological characteristics and distribution of urban pipe network. A pressure-state-response (PSR) model was then proposed to construct the health index system with the consideration of human restoration measures on river health. The matter-element extension model was used to determine the final grade of each river reach and judge the development trend of each river reach''s health. The results showed that the weights of pressure, state and response criterion layer were 0.458, 0.311 and 0.231 respectively. The pressure indices were the main impact factors of river health, when compared to the state indices and response indices. The health levels of six river sections showed great spatial heterogeneity, and the health grades from reach A to reach F were moderate, health, sub-health, moderate, sub-illness and illness respectively. The health grades of the river reaches that run through parks were significantly higher than those run through residential areas. The health level of reach B, reach C and reach D has a tendency for further improvement, while the health status of reach A, reach E and reach F has a tendency for further deterioration. Therefore, more attentions should be paid to the reach A, reach E and reach F to improve their health status in future studies. Overall, the proposed method in the study, which combined PSR model and matter-element extension model, could effectively assess the ecosystem health status and change trend of urban rivers and would provide scientific guidance for future ecological restoration.