北运河系地表水近10年来水质变化及影响因素分析

北运河系为北京市区最重要的排水系统,其水质优劣对城市环境及下游地区有着重要影响,通过2001～2010年间地表水的监测数据、水资源量的统计数据、社会经济的统计数据以及污水处理厂的监测数据来分析影响北运河系水质的原因.结果表明,北运河各排水支流水质均较差,主要污染指标为耗氧型有机污染物及NH4+-N等,丰水期水质好于枯水期,凉水河、温榆河、通惠河等支流的水质严重影响着北运河的水质;北运河系各河段水质在2006年后出现好转,但2006～2010年之间污染指标浓度稳定在Ⅴ类标准以上,水质的进一步改善变得困难;经济的发展、人口的增加对北京市水环境造成了巨大的压力,是造成水质难以彻底改善的主要原因之一;缺少生态补水是河系水质较差的主要原因,降水可以缓解污染,却与地表水径流造成的非点源污染形成矛盾,但对北运河来说,降水仍起到了稀释作用;污水处理率的提高改善了水质,但进一步的水质改善还需要提高污水处理效率,尤其是郊区污水处理率.

Surface Water Quality of Beiyun Rivers Basin and the Analysis of Acting Factors for the Recent Ten Years

As the most important drainage system, the quality of the Beiyun rivers basin play a great role on the city's environment and the areas of down streams, the acting factors were analyzed by the monitoring data of surface water, statistical data of water resources and socioeconomy, monitoring data of municipal treated sewerage, during the year from 2001 to 2010.The results show that the water quality of every branch is very poor. It was found that organics of oxygen consumption and ammonia nitrogen are the most important pollutants. The water quality is better during high flow period than rainless period, and highly depends on the branch water quality of Liangshui river, Wenyu river and Tonghui river. The branch water quality once got better after 2006, however, the concentration of pollutant parameters stands static above standard V during the year from 2006 to 2010, and it is very difficult to make the surface water quality improved. Economic development and population explosion put a great pressure on the water environment, and result that water quality is hard to thoroughly improved. Lack of clean water is another factor in contribution to poor water quality, precipitation can reduce the water pollution but the pollution of non-pointed source of surface water runoff will arise, and to Beiyun river, the pollution is diluted by the precipitation. Water quality is improved by the ratio of sewage disposed, but further results depends on the ratio improving especially in suburb areas.