基于水劣化足迹的城市发展的水环境效应评价——以北京市为例

水劣化足迹是反映污染物排放对水质影响程度的一种评价方法和指标.为了评估和揭示北京市城市发展的水环境效应,本文基于水劣化足迹评价的方法框架,发展和完善相关模型和参数,选取关键污染因子,对北京市2004—2013年水体酸化足迹、水体富营养化足迹和水体生态毒性足迹进行了评价,进而对水劣化足迹与部分城市发展指标的相关关系进行了分析.结果显示:12004—2013年北京市水酸化足迹逐年减小,由2004年的19.1×107kg SO_2eq减少到2013年的8.7×107kg SO_2eq,污染排放对水体酸化的影响有所减弱;2水体富营养化足迹在2004—2009年和2010—2013年两个时间段内总体均呈现减少趋势,但后一时间段内水体富营养化绝对值总体高于前一时间段.2004—2009年,水体富营养化足迹减少了约1.5×10~7kg NO_3eq,而从2010—2013年减少了约0.8×107kg NO_3~-eq;2011年至2013年期间,基于新增污染物(氨氮、总氮和总磷)计算的水体富营养化足迹减少了2.4×10~7kg NO_3eq.从其组成来看,水体富营养化的关键因素为总磷;3选取铅(Pb)、汞(Hg)、铬(Cr)、镉(Cd)、砷(As)5种重金属污染物,对北京市2011—2013年的水体生态毒性足迹进行评价发现,水体生态毒性足迹从4234.7×106m3H_2O eq增加到4653.1×106m3H2O eq.从其组成来看,重金属水体生态毒性足迹的关键污染因子为镉(Cd);4水劣化足迹与城市发展特征指标的关系分析显示,人口数量增速减缓、产业结构调整(第二产业向第三产业转化)以及农业化肥用量的减少,对于水劣化足迹的改善有积极作用.

Water environmental impact assessment of urban development based on water degradation footprint: a case study of Beijing

Water degradation footprint describes the effect of pollutant emission to water quality, and human activities during urban development, such as domestic and industrial effluents, which can have various impacts on water degradation. To analyze the impacts of human activities on water quality, the present study developed the frame and coefficients of water degradation footprint assessment, and adopted life cycle assessment (LCA)-based water degradation footprint of Beijing from 2004 to 2013. The results show that the water acidification footprint decreased annually, declining from 19.1×10⁷ kg SO₂ eq (2004) to 8.7×10⁷ kg SO₂ eq in 2013. Simultaneously, water eutrophication footprint of NO_x varied in two stages. For stage-1, the water eutrophication footprint decreased about 1.5×10⁷ kg NO₃^- eq from 2004 to 2009 and decreased about 0.8×10⁷ kg NO₃^- eq in the later 4 years (stage-2). In 2011-2013, the water eutrophication footprint with the pollutants of NH₃-N, total nitrogen (TN) and total phosphorus (TP) was assessed, and results show that water eutrophication footprint declined about 2.4×10⁷ kg NO₃^- eq in this 3 years, and TP had the largest contribution to water eutrophication. Besides, water ecotoxicity footprint of 5 kinds of heavy metal pollutants was analyzed within the period of 2011-2013. The results show that the water ecotoxicity footprint increased from 4234.7×10⁶ m³ H₂O eq (2011) to 4653.1×10⁶ m³ H₂O eq (2013), and cadmium is the critical factor for heavy metal water ecotoxicity. Based on the results of the assessment, the correlation between water degradation footprints and some urban development indices was analyzed. It''s found that the slowdown of population growth, decrease of chemical fertilizer consumption, as well as the adjustment of industrial structure would facilitate the decrease of water degradation footprint.