Richardson College for the Environment, Department of Environmental Studies and Sciences and Department of Chemistry, The University of Winnipeg, Winnipeg, MB, Canada R3B 2E9.
Sci Total Environ. 2013 Feb 15;445-446:64-78. doi: 10.1016/j.scitotenv.2012.11.100. Epub 2013 Jan 11.
Nutrient enrichment and loadings of pharmaceuticals and agrochemicals into freshwater systems are common concerns, especially for water bodies receiving wastewater inputs. In the rural communities of Morden and Winkler of Manitoba, Canada, sewage lagoons discharge their wastewater directly into Dead Horse Creek, a small tributary of the Red River that empties into Lake Winnipeg. This lagoon approach to managing rural wastewaters is common across the North American Prairies. Therefore, this study aimed to assess the hazards of lagoon treatment releases at this model site. This was done by characterizing the nutrients, organic micropollutants (i.e., pesticides, pharmaceuticals) and standard water quality parameters in the creek prior to and following lagoon discharge events over a number of years (2009-2011). Measured concentrations of nutrients were compared to regulatory expectations and micropollutants were assessed using hazard quotients. As expected, concentrations of nitrogen and phosphorus species were greatest in sites downstream of the sewage outfall immediately following discharge events. Pharmaceutical and agricultural chemicals were detected at concentrations between 0.5 and 90 ng/L. Detection frequencies and concentrations matched typical use patterns. Those compounds used predominately for human medicine were detected at downstream sites following discharge events, while those used in an agricultural setting were detected at relatively consistent levels over time at sites both upstream and downstream of the outfall location. Hazard quotients calculated for micropollutants of interest indicated minimal toxicological risk to aquatic biota in the creek, with only erythromycin and diazinon presenting a potential concern to aquatic algae and invertebrates. Concentrations of nutrients exceeded Canadian guideline thresholds during release, but returned to background levels once discharges ceased. Therefore, it is advisable that wastewater treatment and management strategies such as constructed wetlands and/or staggered releases be used in order to minimize the hazard posed by nutrient pulses in Dead Horse Creek and other similar systems.
营养物质的富集以及药品和农用化学品向淡水系统中的负荷是常见的关注点，尤其是对于接收废水输入的水体而言。在加拿大马尼托巴省的莫登和温克勒的农村社区，污水处理池将其废水直接排入死马溪，死马溪是雷德河的一条小支流，最终流入温尼伯湖。这种处理农村废水的方法在北美大平原地区很常见。因此，本研究旨在评估该模型地点的污水处理池排放物的危害。为此，本研究在几年内（2009-2011 年），对死马溪在污水处理池排放前后的多年进行了特征描述，以评估其水质参数、有机微量污染物（即农药、药品）和标准水质参数。所测量的营养物质浓度与监管期望进行了比较，并用危害系数评估了微量污染物。如预期的那样，在污水排放口的下游，氮和磷的浓度在排放事件后立即达到最高值。在浓度为 0.5 至 90ng/L 的范围内检测到了药品和农用化学品。检测到的频率和浓度与典型的使用模式相匹配。那些主要用于人类医学的化合物在排放事件后被检测到出现在下游站点，而那些在农业环境中使用的化合物则在排放口上下游的站点中随着时间的推移保持相对稳定的水平被检测到。对于感兴趣的微量污染物计算出的危害系数表明，死马溪中的水生生物面临的毒理学风险很小，只有红霉素和二嗪农对水生藻类和无脊椎动物可能构成潜在威胁。在释放过程中，营养物质的浓度超过了加拿大的指导阈值，但一旦排放停止，浓度就会恢复到背景水平。因此，建议采用人工湿地和/或交错释放等废水处理和管理策略，以尽量减少死马溪和其他类似系统中营养物质脉冲带来的危害。
