Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, 14850, USA.
Department of Natural Resources, Cornell University, Ithaca, NY, 14850, USA.
Environ Sci Pollut Res Int. 2019 Jul;26(21):21797-21807. doi: 10.1007/s11356-019-04663-8. Epub 2019 May 27.
Microplastics, particles less than 5 mm in size, are an emerging contaminant in waterways worldwide. Most microplastic studies focus on spatial trends in concentration, but in systems as dynamic as rivers, to draw conclusions from existing spatial studies, we must first examine how microplastic concentrations may change with time and flow conditions. In this study, we investigate how microplastic concentrations change over a 24-h period and between seasonally high and low flows. We do this in two streams, controlling for wastewater treatment strategy: one stream in a watershed where waste is treated with septic systems and the other receiving wastewater treatment plant effluent. We hypothesized that a stream with wastewater treatment plant effluent would exhibit higher and more variable microplastic concentrations than a stream in a watershed with septic systems. Results indicate, however, that there is no significant difference between the two streams despite their differing treatment strategies. Additionally, no significant variation in concentrations was measured over two 24-h sampling campaigns. There was, however, significantly higher concentrations measured in summer low flow conditions relative to spring high flow conditions across both sampled streams (p value <0.001), indicating that increases in stream discharge unrelated to storm events dilute and decrease measured microplastic concentrations. From this, we learn that pairing measured concentrations with a description of flow conditions at sampling time is a requisite for a robust microplastic literature that allows for comparisons between existing spatial studies and extrapolations to global loads.
微塑料是一种粒径小于 5 毫米的新兴污染物，在全球水道中普遍存在。大多数微塑料研究都集中在浓度的空间趋势上，但在像河流这样动态的系统中，要从现有空间研究中得出结论，我们必须首先研究微塑料浓度如何随时间和水流条件而变化。在这项研究中，我们调查了微塑料浓度在 24 小时内和季节性高、低流量之间的变化情况。我们在两个溪流中进行了研究，控制了废水处理策略：一个溪流所在的流域使用化粪池系统处理废物，另一个溪流则接收废水处理厂的废水。我们假设，与使用化粪池系统的流域中的溪流相比，接收废水处理厂废水的溪流中微塑料浓度会更高且更具变异性。然而，结果表明，尽管这两个溪流的处理策略不同，但它们之间没有显著差异。此外，在两次为期 24 小时的采样活动中，浓度没有明显变化。然而，在两个采样溪流中，夏季低流量条件下的浓度明显高于春季高流量条件下的浓度（p 值<0.001），这表明与风暴事件无关的溪流排放增加会稀释并降低测量的微塑料浓度。由此可知，将测量浓度与采样时的水流条件描述相结合是建立稳健的微塑料文献的必要条件，这可以使现有空间研究之间进行比较，并将其外推到全球负荷。
