厦门市氮素流动与水环境负荷演变特征

The evolution characteristics of nitrogen flow and water environment load in Xiamen

人类活动造成大量氮素在城市生态系统中聚集,从而对水环境质量造成不利影响.作为一个复合生态系统,城市各系统对水环境的影响呈现不同的变化特征及趋势.本研究以厦门市为例,构建了城市氮流动模型,计算了水环境氮负荷,并通过情景分析的方法探讨了减缓城市水环境氮污染的策略.结果表明,1995—2015年厦门市水环境总氮负荷呈现上升-下降-上升式波动变化,总量介于8800～11100 t之间,主要受地表水氮负荷影响显著,而地下水变化相对稳定.在城市化进程中,城市各系统对水环境产生了不同程度的影响,农作物生产系统、污水处理系统及大气氮沉降是水环境氮污染的主要排放源,年均贡献率达69.0%.农作物生产系统和污水处理系统变化较显著,前者对水环境氮负荷的贡献率从1995年的22.3%下降到2015年的7.0%,后者由1995年的9.7%逐渐上升到2015年的40.7%.情景分析可知,提高城市废物、废水的资源化和综合化利用效率是减少城市水环境氮污染的重要途径.

Large amount of reactive nitrogen generated by human activities accumulates in urban ecosystem, causing negative effects on water environment quality. As a complex system, different subsystems of the city have different impacts on urban water environment, and these impacts have taken on different characteristics and trends. This study constructed an urban nitrogen flow model, which is applied to calculate its water nitrogen load in Xiamen City. Further, we explored the strategies for mitigating nitrogen pollution in urban water environment through scenario analysis. The results show that: during 1995-2015, the total nitrogen load in water environment of Xiamen ranged from 8800 to 11100 t, which shows a fluctuation of rising, decreasing and then rising. It mainly affected by nitrogen load of surface water, and the groundwater change is relatively stable. In the process of urbanization, different subsystems have caused different effects on urban water environment. Crop production, sewage treatment and atmospheric deposition were the main sources of nitrogen pollution in water environment, with annual average contribution of 69% to the total water nitrogen load. The contribution of crop production dropped from 22.3% in 1995 to 7.0% in 2015, while that of sewage treatment increased from 9.7% in 1995 to 40.7% in 2015. According to scenario analysis, improving the recycling of municipal solid waste and sewage and optimizing the industrial structure could be an important way to reduce the nitrogen pollution in the urban water environment.