长江流域湖泊富营养化发展趋势与展望

Lake eutrophication development trend and perspectives in Changjiang River Basin

随着国家对生态环境问题的重视和保护治理力度的加大,中国河流与湖泊水质状态的变化及控源截污等治理措施的成效,已日益成为关注焦点。通过收集不同行业、部门与科研单位对长江干流水质和流域内若干典型湖泊水质及富营养化的监测资料,分析发现在最近十余年时间内,长江流域乃至全国河流水质已显著改善,但湖泊水质的提升不明显,富营养化和蓝藻水华无明显改善,部分湖泊甚至还有所加重。造成这种状况的主要原因包括水体自身特性与外部驱动两个方面:①湖泊水流交换速度较河流慢,使污染物和营养盐更容易在湖泊中滞留,底部长期蓄积的氮磷等营养盐极易因风浪等扰动而再次释放产生内源污染,极大延缓或抵消了湖泊水质的恢复;②在全球气候变化的背景下,蓝藻水华暴发时间提前、持续时间延长、暴发频率增加,进一步加剧了富营养化湖泊蓝藻水华的产生强度。长江中下游地区浅水湖泊富营养化控制和蓝藻水华治理将是一个漫长而艰巨的任务。

With the country attaches more attention on the ecological environment and strengthens regulation on environmental protection,changes in the water quality of China s rivers and lakes and the effectiveness of control measures such as pollution control have increasingly become the focus.Through the monitoring data collection from different industries,departments and scientific research units on the Changjiang River main stream and a number of water quality and eutrophication data of typical lakes in the basin,it is found that in the last decade or so,the Changjiang River Basin and even the whole country wide water quality of rivers have improved significantly,but the lake water quality enhancement is less obvious,eutrophication and cyanobacterial blooms have not been significantly improved,and some lakes are even aggravated.The main reasons for this situation include the characteristics of the water body itself and the external drive in two aspects:①The water exchange rate in the lake is slower than rivers,so that pollutants and nutrients are more likely to be retained in the lakes.At the same time,nitrogen,phosphorus and other nutrients have deposited at the bottom of lakes for a long time,which are very easy to be released again due to the wind and waves and other disturbances to produce endogenous pollution,thus greatly slowing down or offsetting the recovery of the water quality in the lakes.②Under the background of global climate change,the time of cyanobacterial bloom outbreaks is advanced,the duration is prolonged,and the frequency of outbreaks is increased,which further aggravate the intensity of cyanobacterial bloom production in eutrophic lakes.The control of eutrophication and cyanobacterial bloom management in shallow lakes in the middle and lower reaches of Changjiang River would be a long and arduous task.