Muirhead R W, Davies-Colley R J, Donnison A M, Nagels J W
AgResearch Ltd., Private Bag, Mosgiel 50034, New Zealand.
Water Res. 2004 Mar;38(5):1215-24. doi: 10.1016/j.watres.2003.12.010.
Stream sediments have been recognised as an in-channel store of faecal contamination that can be mobilised during floods or other sediment-disturbing events. We studied this store of faecal contamination by creating artificial floods during dry weather when, in the absence of overland flow from the catchment, the only source of faecal bacteria was stores within the channel. Artificial floods, created by releasing water from a supply reservoir, increased the E. coli concentration in the water column by two orders of magnitude, from a background level of 10(2) cfu per 100 mL to over 10(4) cfu per 100 mL. The bacterial peak concentrations and yields declined systematically through a triplicate flood series. The size of the total in-channel store, calculated as the sum of yields of an infinite series of artificial floods, was approximately 10(8) cfu m(-2) of streambed area. Direct measurements of sediment E. coli found few sites (only those associated with cattle crossings) with areal concentrations as high as 10(8) cfu m(-2), consistent with flood yields. Concentrations of E. coli in the biofilms on exposed rocks were orders of magnitude lower, indicating that exposed rocks were not a source of E. coli released by the artificial floods.
河流沉积物已被确认为粪便污染的河道内储存库，在洪水或其他扰动沉积物的事件中，这些污染可能会被释放出来。我们通过在干旱天气制造人工洪水来研究这种粪便污染储存库，在这种情况下，由于集水区没有坡面径流，粪便细菌的唯一来源是河道内的储存物。通过从供水水库放水制造的人工洪水，使水柱中的大肠杆菌浓度增加了两个数量级，从每100毫升10² 菌落形成单位的背景水平增加到每100毫升超过10⁴ 菌落形成单位。在三次重复的洪水系列中，细菌峰值浓度和产量系统性下降。通过计算一系列无限次人工洪水的产量总和得出的河道内总储存量大小约为每平方米河床面积10⁸ 菌落形成单位。对沉积物中大肠杆菌的直接测量发现，很少有地点（只有那些与牲畜过河点相关的地点）的面浓度高达每平方米10⁸ 菌落形成单位，这与洪水产量一致。暴露岩石上生物膜中的大肠杆菌浓度要低几个数量级，这表明暴露岩石不是人工洪水释放大肠杆菌的来源。
