Surfrider Foundation Europe, 33, allée du Moura, 64200 Biarritz, Pyrénées-Atlantiques, France.
Surfrider Foundation Europe, 33, allée du Moura, 64200 Biarritz, Pyrénées-Atlantiques, France.
Sci Total Environ. 2020 May 20;718:137319. doi: 10.1016/j.scitotenv.2020.137319. Epub 2020 Feb 15.
Many studies have been conducted to quantify microplastic contamination, but only a few of them have actually the sampling methodology and associated uncertainties. This study seeks to examine the influence of sampling strategy on the confidence interval of river microplastic estimates. 16 samples are collected in the Gave de Pau River (southwestern France) during a three-hour window with a 330-μm mesh size net. Three different exposure times (3, 5 and 7 min) allow for a respective filtration rate by the net of 35.6 m (3 samples), 59.4 m (10 samples), and 83.2 m (3 samples) of water. Organic matter contained in samples is removed by hydrogen peroxide oxidation. The plastic particles are then counted and classified under a binocular microscope. The microplastic concentrations vary between 2.64 and 4.24 microplastics/m, with a median value of 3.26 microplastics/m. Statistical analysis does not show differences in microplastic concentrations for the three exposure times. This result seems to demonstrate that a filtration of approx. 35 m of water is sufficient under similar conditions (similar flow condition and degree of microplastic contamination) and can help reduce sampling and sample processing time. Other analyses, based on 10 filtrations of 59.4 m, show that the higher the number of samples, the lower the confidence interval. For triplicates, the mean confidence interval reaches 15% of the median value. Thus, collecting triplicates would seem to offer a reasonable optimum, in combining an acceptable error percentage and time efficiency. These results might depend on the microplastic load of the river, therefore making it necessary to conduct similar analyses on other rivers. This study reports for the first time uncertainties related to microplastic sampling in rivers. Such findings will serve to set up long term monitoring, highlight spatial differences between sites and improve the accuracy of annual microplastic fluxes in rivers.
许多研究已经对微塑料污染进行了量化，但只有少数研究实际涉及采样方法和相关不确定性。本研究旨在研究采样策略对河流微塑料估计置信区间的影响。在法国西南部的加夫德保河（Gave de Pau River）进行了三个小时的采样，使用 330 微米网眼尺寸的网采集了 16 个样本。三个不同的暴露时间（3、5 和 7 分钟）允许网以 35.6 米（3 个样本）、59.4 米（10 个样本）和 83.2 米（3 个样本）的速度过滤水。通过过氧化氢氧化去除样品中的有机物。然后在双目显微镜下对塑料颗粒进行计数和分类。微塑料浓度在 2.64 到 4.24 个微塑料/米之间，中位数为 3.26 个微塑料/米。统计分析显示三个暴露时间的微塑料浓度没有差异。这一结果似乎表明，在类似条件下（相似的水流条件和微塑料污染程度），过滤约 35 米的水就足够了，并且可以帮助减少采样和样品处理时间。基于 59.4 米的 10 次过滤的其他分析表明，样本数量越多，置信区间越低。对于三重样本，平均值置信区间达到中位数的 15%。因此，采集三重样本似乎是一个合理的最佳选择，既可以接受误差百分比，又可以提高时间效率。这些结果可能取决于河流的微塑料负荷，因此有必要在其他河流上进行类似的分析。本研究首次报告了河流中微塑料采样的不确定性。这些发现将有助于建立长期监测，突出站点之间的空间差异，并提高河流中每年微塑料通量的准确性。
