Büngener Lina, Postila Heini, Löder Martin G J, Laforsch Christian, Ronkanen Anna-Kaisa, Heiderscheidt Elisangela
Water, Energy and Environmental Engineering, Faculty of Technology, 90014 University of Oulu, Finland.
Water, Energy and Environmental Engineering, Faculty of Technology, 90014 University of Oulu, Finland.
Sci Total Environ. 2023 Dec 10;903:166334. doi: 10.1016/j.scitotenv.2023.166334. Epub 2023 Aug 15.
Microplastics (MPs) are an anthropogenic pollutant of emerging concern prominent in both raw and treated municipal wastewater as well as urban and agricultural run-off. There is a critical need for the mitigation of both point- and diffuse sources, with treatment wetlands a possible sustainable nature-based solution. In this study, the possible retention of MPs in treatment wetlands of the widely used surface flow (SF) type was investigated. In- and outflow water, as well as atmospheric deposition, at a full-scale reed-based SF wetland (operating as a polishing phase of municipal wastewater treatment) was analyzed for MPs in a size range of 25-1000 μm. FPA-based μFT-IR spectroscopic imaging was used in combination with automated data analysis software, allowing for an unbiased assessment of MP numbers, polymer types and size distribution. Inflow water samples (secondary treated wastewater) contained 104 MPs m and 56 MPs m in sampling campaigns 1 and 2, respectively. Passage through the SF wetland increased the MP concentration in the water by 92 % during a rain intense period (campaign 1) and by 43 % during a low precipitation period (campaign 2). The MP particle numbers, size and polymer type distribution varied between the two sampling campaigns, making conclusions around the fate of specific types of MPs in SF wetlands difficult. Atmospheric deposition was measured to be 590 MPs m week during the rain-intense period. Our findings point towards atmospheric deposited MPs as an important factor in the fate of MPs in SF wetlands, causing an increase of MP concentrations, and potentially explaining the variations observed in MP concentrations in wetland effluent and removal efficiency. Furthermore, atmospheric deposition might also be a reason for the considerable inter-study variation regarding MPs removal efficiency in SF wetlands found in the available literature.
微塑料（MPs）是一种新兴的人为污染物，在未经处理和经过处理的城市废水中以及城市和农业径流中都很突出。迫切需要减轻点源和非点源污染，处理湿地可能是一种可持续的基于自然的解决方案。在本研究中，调查了广泛使用的表面流（SF）型处理湿地中微塑料的可能截留情况。对一个全尺寸芦苇基表面流湿地（作为城市污水处理的抛光阶段）的进水、出水以及大气沉降进行了分析，以检测尺寸范围为25 - 1000微米的微塑料。基于傅里叶变换红外光谱成像（FPA-based μFT-IR）与自动数据分析软件相结合，能够对微塑料数量、聚合物类型和尺寸分布进行无偏评估。进水样本（二级处理后的废水）在采样活动1和2中分别含有104个/立方米和56个/立方米的微塑料。在降雨强烈时期（活动1），通过表面流湿地使水中微塑料浓度增加了92%，在低降水时期（活动2）增加了43%。两次采样活动中微塑料颗粒数量、尺寸和聚合物类型分布有所不同，因此很难得出关于特定类型微塑料在表面流湿地中归宿的结论。在降雨强烈时期，测得大气沉降为每周590个/立方米。我们的研究结果表明，大气沉降的微塑料是表面流湿地中微塑料归宿的一个重要因素，导致微塑料浓度增加，并可能解释了湿地出水微塑料浓度和去除效率中观察到的变化。此外，大气沉降也可能是现有文献中关于表面流湿地微塑料去除效率研究间存在显著差异的一个原因。
