人类活动对杭州城乡复合系统陆源氮排海的驱动分析

Terrestrial nitrogen discharges to the ocean derived from human activities in Hangzhou Area,China

对过去28年间(1980～2008)杭州城乡复合系统陆源氮(N)向杭州湾的排量进行了系统的估算,并分析了陆源N增加的社会经济驱动力及相应的控制对策.结果表明,杭州城乡复合系统陆源N排海量从1980年的1.1×104t增加到2008年的3.7×104t,其中,农业面源污染对于N排海量的贡献在28年间一直保持在50%左右,但生活污水的点源N排放量却迅速增加,其2008年的贡献率已达到42%.目前,农田过量施肥、养殖业废水排放及与种植业的N循环脱钩、生活污水处理率低以及污水处理厂出水N浓度标准过宽等是杭州城乡复合系统陆源N排海量迅速增加的主要原因.杭州城乡复合系统陆源N排海量与GDP增长趋势之间的关系显示出污染控制技术和政策调控的功能得到了强化.杭州城乡复合系统的排N量仅占杭州湾陆源N总量的38%,杭州与周边的嘉兴、宁波、绍兴和部分上海地区在2008年共有超过10×104t的活性N排入杭州湾.通过技术革新、政策调整以及环保意识建立来对快、慢变量(相对系统动态而言,发生快速、慢速变化的因子,通常相当于直接驱动与间接驱动力)进行协调控制,是推动杭州湾区域经济环境可持续发展的关键对策.

Nitrogen loads from Hangzhou Area （HA） to Hangzhou Bay were estimated for the past 28 years,and the socioeconomic drivers and control strategies for the increasing N loads were analyzed. The results showed that N loads from HA to Hangzhou Bay had increased from 1.1×104 t in 1980 to 3.7×104 t in 2008. The contribution of agricultural nonpoint sources was constant at about 50% of total N loads during the 28-year period,while the contribution of point source domestic wastewater increased up to 42% in 2008. Over-fertilization from agricultural practices,livestock and aquaculture N emissions and their decoupling from cropland in N cycling,as well as a low domestic wastewater treatment percentage and lax N effluent standards of wastewater treatment plants,are the main reasons for the observed increase. The trend between N loads and the Gross Domestic Product （GDP） indicated that the pollution control technology and policy in the HA has improved since the 1990s and significant differences were observed from the early 2000s. In addition,N loads from the HA only contributed to 38% of total N loads to Hangzhou Bay,which was over 10×104 t N including N loads from nearby Jiaxing,Ningbo,Shaoxing and Shanghai. Comprehensive regulations on rapid/slow variables （factors that change fast/slow relative to system dynamics,usually related to direct and indirect driving forces） through pollution control technology updates,policy regulation,and public environmental protection awareness are key strategies for economic and environmental sustainable development of the Hangzhou Bay area. Much like the low carbon economy,a low N society is needed to ensure future sustainable development.