城市群水污染物排放的驱动因素及尺度效应

Driving factors and scale effects of water pollutant discharge in the urban agglomeration

揭示水污染物排放的驱动因素及尺度效应是研究城市群演化环境效应的重要议题,也是实现城市群水污染物协同减排和水环境协同治理的重要前提。以长三角城市群的305个县域为例,选取化学需氧量(COD)和氨氮(NH_(3)-N)两项特征污染物指标,在2011—2016年水污染物排放时空格局分析基础上,采用空间滞后模型(SLM)和空间误差模型(SEM)评估城市群水污染物排放的驱动因素,构建多尺度地理加权回归(MGWR)模型诊断驱动力的尺度效应及空间异质性。结果显示:常住人口规模、城镇化水平和经济发展水平对水污染物排放呈现全域层面的正向驱动,而工业化水平、社会固定资产投资、外商直接投资、地方财政分权程度以局部的微观作用为主;固定资产投资在杭嘉湖及沿海地区对COD和NH_(3)-N排放均呈较强正向驱动,工业化水平在太湖流域及浙江全域对COD排放呈正向驱动;外商直接投资对NH_(3)-N排放呈局部抑制作用,外资投入的“污染光环”效应在苏北、皖北、浙南等城市群边缘区较为突出;地方财政分权在城市群中心区对COD排放具有明显抑制作用,反映出地方环保意识提升和多层级环境规制强约束的积极影响。建议引导绿色生产生活方式以降低水污染物排放基数,在工业生产、资本投入和财政收支等领域嵌入环境倒逼机制,系统构建与水环境承载力相适应的城市群高质量发展格局。

Revealing the driving factors and scale effects of water pollutant discharges is of great importance in the study of the environmental consequences of urban agglomeration evolution.It is also a prerequisite for ensuring collaborative water pollutant reduction and environmental governance in urban agglomerations.This study,taking 305 counties in the Yangtze River Delta(YRD)as an example,selects Chemical Oxygen Demand(COD)and Ammonia Nitrogen(NH_(3)-N)as two distinctive pollutant indicators,and uses the Spatial Lag Model(SLM)and Spatial Error Model(SEM)to estimate the driving factors of water pollutant discharges in 2011 and 2016.Then the Multiscale Geographically Weighted Regression(MGWR)model is constructed to diagnose the scale effect and spatial heterogeneity of the driving factors.The findings show that the size of permanent population,the level of urbanization,and economic development level show positive global-scale impacts on water pollutant discharges,while the level of industrialization,social fixed assets investment,foreign direct investment,and local fiscal decentralization are dominated by micro impacts at the local scale.The spatial heterogeneity of local influencing factors mainly presents the following characteristics.Social fixed assets investment has a strong positive effect on both COD and NH_(3)-N discharges in the Hangzhou-Jiaxing-Huzhou region and coastal area of the YRD;industrialization has a positive effect on COD discharges in the Taihu Lake basin and Zhejiang province;foreign direct investment has a local inhibitory effect on NH_(3)-N discharge,and the"pollution halo"effect of foreign investment is more prominent in the marginal areas of the YRD such as northern Jiangsu,northern Anhui,and southern Zhejiang;local fiscal decentralization has a noticeable inhibitory effect on COD discharge in the central part of the YRD,reflecting the positive impacts of improved local environmental awareness and stronger constraints of multi-level environmental regulations in the urban agglomeration.Therefore,it is recommended to take green production and living style to reduce the discharge base of water pollutants,to embed environmental push-back mechanism in the fields of industrial production,capital investment and financial income and expenditure,and to establish systematically a high-quality development pattern of urban agglomerations that is compatible with the carrying capacity of the water environment.