Vienna University of Technology, Institute for Water Quality, Resources and Waste Management, Karlsplatz 13/226, Vienna, Austria.
Water Sci Technol. 2010;61(4):1053-63. doi: 10.2166/wst.2010.566.
Two transient pollution events were monitored in a pastoral stream in southwestern Kenya to evaluate their relative contribution to diffuse pollution. Peak loads of pollutants during storm-induced transients were within 3-4 orders of magnitude higher than the short-lived (30-60 minutes) diurnal episodes provoked by in-stream activities of people and livestock. Transient yields were striking during storm-induced events; 778,000, 8,400, 550 and 100 kg day(-1) for suspended solids, BOD(5), total P and total N, respectively, compared to wet weather base flow (150, 30, 0.8 and 1.4 kg day(-1), for the same parameters, respectively). Two forms of concentration-discharge relationships were observed: increases in concentration for turbidity, suspended solids, BOD(5), total P and the faecal indicator bacteria at the peak of the stream hydrograph, and concurrent decreases in concentration for conductivity and total N. Following each storm-induced transient event, a marked improvement in water quality was observed within 48-72 hrs of the receding limb of the stream hydrograph before the next base low was established. It was concluded that storm-induced transients are exceedingly important for the mobilization of pollutants from diffuse sources but both transient events affect stream-channel processes, especially water quality, with the possibility of attendant consequences on the health of riparian inhabitants.
在肯尼亚西南部的一条牧溪中监测到两次短暂的污染事件，以评估它们对漫射污染的相对贡献。在风暴引起的瞬态期间，污染物的峰值负荷比由人类和牲畜在溪流中活动引起的短暂（30-60 分钟）日变化高出 3-4 个数量级。在风暴引起的事件中，瞬态产量非常显著；悬浮固体、BOD（5）、总磷和总氮的排放量分别为 778,000、8,400、550 和 100 千克/天，而湿天气基流（同一参数）的排放量分别为 150、30、0.8 和 1.4 千克/天。观察到两种浓度-流量关系：在河流流量图的峰值处，浊度、悬浮固体、BOD（5）、总磷和粪便指示菌的浓度增加，而电导率和总氮的浓度同时降低。在每次风暴引起的瞬态事件之后，在河流流量图的退水支腿之后的 48-72 小时内，观察到水质明显改善，直到下一个基本低流量建立。结论是，风暴引起的瞬态对从漫射源中动员污染物非常重要，但两次瞬态事件都影响溪流通道过程，特别是水质，可能对河岸居民的健康产生伴随的后果。
