School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia.
Sci Total Environ. 2022 Apr 20;818:151813. doi: 10.1016/j.scitotenv.2021.151813. Epub 2021 Nov 20.
Hiking and trail running are increasingly popular and could present a significant source of microplastics on recreational trails in nature reserves, wilderness areas and conservation areas. Deposition may be concentrated on trail surfaces, however sampling techniques for microplastics on soil or rock surfaces have not yet been developed. In this study, sampling strategies were evaluated for microplastics on three types of recreational trail surfaces - asphalt, compacted soil, and a loose overlay of soil. We spiked trail surfaces with pink rubber microplastics and collected samples using a handheld vacuum, manual sweeping, and gel lifter tape. Spiked and in situ microplastics were extracted from soil samples using density separation (NaI, ρ = 1.6 g cm) with organic matter digestion (30% HO), then visualised and counted using stereomicroscopy. The gel lifter tape yielded the highest recovery of spiked and counts of in situ microplastics on asphalt (118% ± 15%, 3183 ± 830 microplastics per 40 cm) and compacted soil (127% ± 7%, 333 ± 106 microplastics per 40 cm). Sweeping produced quantitative recovery for spiked microplastics on compacted soil (88% ± 13%) but yielded significantly fewer in situ microplastics (148 ± 40 microplastics per 40 cm) than the tape. Sweeping was the only technique to achieve quantitative recovery of spiked microplastics in the loose overlay of soil (110% ± 14%) when soil carbon was 0.8% ± 0.3%, however increasing soil carbon was associated with reduced microplastic recovery. Preliminary assessment indicated quantification of microplastics smaller than 100 μm was not possible with any of the methods tested. Sweeping and the gel lifter tape were both effective for evaluating microplastic deposition and spatial distribution on recreational trails, depending on the properties of the trail.
徒步旅行和越野跑越来越受欢迎，它们可能成为自然保护区、荒野地区和保护区休闲步道上微塑料的重要来源。微塑料可能会集中在步道表面，但尚未开发出用于土壤或岩石表面微塑料的采样技术。在这项研究中，我们评估了三种休闲步道表面（沥青、压实土壤和松散土壤覆盖层）上微塑料的采样策略。我们在步道表面撒上粉红色橡胶微塑料，然后使用手持真空吸尘器、手动清扫和凝胶刮刀采集样本。用密度分离（密度为 1.6 g/cm 的 Nal）和有机物消化（30%HO）从土壤样品中提取掺入和原位微塑料，然后使用立体显微镜对其进行可视化和计数。凝胶刮刀从沥青（118%±15%，40 cm 内 3183±830 个微塑料）和压实土壤（127%±7%，40 cm 内 333±106 个微塑料）中回收掺入和原位微塑料的效果最好。清扫对压实土壤中掺入微塑料的定量回收效果较好（88%±13%），但原位微塑料的回收率明显较低（40 cm 内 148±40 个微塑料）。清扫是唯一一种在土壤碳含量为 0.8%±0.3%时能定量回收松散土壤覆盖层中掺入微塑料的技术，但随着土壤碳含量的增加，微塑料的回收率会降低。初步评估表明，在所测试的方法中，无法对小于 100 μm 的微塑料进行定量评估。清扫和凝胶刮刀都可以有效地评估休闲步道上微塑料的沉积和空间分布，具体取决于步道的特性。
