Department of Geography, Portland State University.
Department of Environmental Science and Management, Portland State University.
Sci Total Environ. 2022 Aug 10;833:155143. doi: 10.1016/j.scitotenv.2022.155143. Epub 2022 Apr 8.
While microplastics are a pollutant of growing concern in various environmental compartments, less is known regarding the sources and delivery pathways of microplastics in urban rivers. We investigated the relationship between microplastic concentrations and various spatiotemporal factors (e.g., land use, arterial road length, water velocity, precipitation) in two watersheds along an urban-rural gradient in the Portland metropolitan area. Samples were collected in August, September, and February and were analyzed for total microplastic count and type. Nonparametric statistics were used to evaluate potential relationships with the explanatory variables, derived at both the subwatershed and near stream scales. In August, microplastic concentrations were significantly higher than in February. August concentrations also negatively correlated with flow rate, suggesting that lower flow rates may have facilitated the accumulation of microplastics. Smaller size microplastic particles (< 100 μm) were found more in August than September and February, while larger size particles were more dominant in February than the other months. Microplastic concentrations were positively related to 24-h antecedent precipitation in February. Negative correlations existed between wet season microplastic concentrations and agricultural lands at the near stream level. The results indicate that near stream variables may more strongly influence the presence and abundance of microplastics in Portland's waterways than subwatershed-scale variables. Fragments were the most commonly observed microplastic morphology, with a dominance of gray particles and the polymer polyethylene. The findings of this study can inform management decisions regarding microplastic waste and identify hotspots of microplastic pollution that may benefit from remediation.
虽然微塑料是各种环境介质中越来越受关注的污染物，但对于城市河流中微塑料的来源和输送途径知之甚少。我们调查了波特兰都会区城乡梯度沿线两个流域中微塑料浓度与各种时空因素（如土地利用、动脉道路长度、水流速度、降水）之间的关系。在 8 月、9 月和 2 月采集样本，并分析总微塑料计数和类型。非参数统计用于评估与解释变量之间的潜在关系，这些变量是在子流域和近溪流尺度上得出的。8 月，微塑料浓度明显高于 2 月。8 月的浓度与流速呈负相关，表明较低的流速可能促进了微塑料的积累。8 月发现的小于 100μm 的微塑料颗粒比 9 月和 2 月多，而较大尺寸的颗粒在 2 月比其他月份更为常见。2 月，微塑料浓度与 24 小时前期降水呈正相关。近溪流尺度的湿季微塑料浓度与农业用地呈负相关。结果表明，与子流域尺度变量相比，近溪流变量可能更强烈地影响波特兰水道中微塑料的存在和丰度。碎片是最常见的微塑料形态，以灰色颗粒和聚合物聚乙烯为主。本研究的结果可以为微塑料废物的管理决策提供信息，并确定可能需要修复的微塑料污染热点。
