Table_1_Change in microplastic concentration during various temporal events downstream of a combined sewage overflow and in an urban stormwater creek.docx

Changes in microplastic concentrations were examined during various temporal events including heavy rain and snowmelt in a river and an urban stream receiving stormwater. Additionally, microplastic concentrations were measured in an urban river during an active combined sewage overflow event. Microplastic concentrations downstream of a combined sewage outfall were observed to increase seven times compared to ambient conditions. During heavy rainfall an increase of 50 times the microplastic concentration was observed in the urban creek with microplastic concentrations doubling in the urban river. However, the largest increase in microplastic concentration at both locations was observed during the primary snowmelt of spring, with microplastic concentrations increasing 114 times in the urban creek and 11 times in the urban river. These results suggest that more research is required to further establish the influence of both combined sewage overflows and snowmelt as a major temporal conduit of microplastics to freshwater environments.

本研究针对受纳雨水径流的河流与城市溪流，对强降雨、春季融雪等不同时段的微塑料（microplastic）浓度变化开展了监测。此外，本研究还对发生活跃合流制污水溢流（Combined Sewage Overflow）事件的城市河段，测定了微塑料浓度。监测结果显示，合流制排污口（Combined Sewage Outfall）下游的微塑料浓度较背景环境浓度升高7倍。强降雨期间，城市溪流中的微塑料浓度升至原浓度的50倍，城市河段的微塑料浓度则翻倍。然而，两处监测点位的微塑料浓度增幅峰值均出现在春季首次融雪时段：城市溪流的微塑料浓度升至原浓度的114倍，城市河段的微塑料浓度升至原浓度的11倍。上述研究结果表明，仍需开展更多研究，以进一步明确合流制污水溢流与融雪作为微塑料向淡水环境输入的主要时间性传输通道的影响。