Purpose

Microplastics have been widely reported to contaminate aquatic environments, particularly impacting marine organisms, but little is known of microplastic contamination of the soil environment. This study compared the distribution of microplastics in forest, urban, and agricultural soils, investigating the reasons for differences in abundance associated with land use.

Materials and methods

We analyzed distribution and abundance of microplastics in 100 soils, representing different land use types that include forest, urban (traffic and residence), and agriculture the environs of Yeoju City. Sampling plots were located on a systematic grid with 2.5 km × 2.5km spacing. Topsoil (0–5 cm) was collected with a hand auger and samples were pretreated by drying, density separation using ZnCl₂ solution, organic matter digestion, and decompression filtration. Abundance of microplastics was measured by counting using a digital stereo microscope; microplastics were grouped by shapes (fragment, film, fiber, and sphere) and color (black, red, green, blue, yellow, white, and transparent). Fourier-transform infrared spectroscopy (FT-IR) analysis was used to identify polymer type of the microplastics.

Results and discussion

Soils of Yeoju contained an average 700 pieces·kg⁻¹ of microplastics, but this greatly varied with land use types. Roadside soils had more microplastics (1108 pieces kg⁻¹), mostly black styrene-butadiene rubber (SBR) fragments associated with tire dust. Unexpectedly, the largest amount of microplastics was detected not from urban soils but from an upland soil (3440 pieces kg⁻¹). The mean abundance of microplastics in agricultural soil was 664 pieces kg⁻¹, varying with farming types; the highest abundance was at orchard sites, followed by upland, greenhouse, and then paddy field sites. Polyethylene (PE) and polypropylene (PP) were identified from microplastics sampled at upland, greenhouse, and orchard sites, while SBR-derived microplastics were found more widely in all farmland soils, implicating that mulching film usage and farm machinery.

Conclusions

Soil microplastic contamination is significant and widespread in urban and agricultural soils of Yeoju, but differs in form and distribution, according to the locality of traffic and farming. Atmospheric fallout to forest soils is quantified and found to be significantly impacted by microplastics. The use of mulching film as a source of PE and PP presents particular concern in terms of the effects of microplastic contamination on soil quality, health, and functionality in agroecosystems.

中文翻译：

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森林，城市和农业土壤的塑料污染：以大韩民国Ye州市为例

目的

广泛报道了微塑料会污染水生环境，特别是影响海洋生物，但对土壤环境的微塑污染知之甚少。这项研究比较了森林，城市和农业土壤中微塑料的分布，调查了与土地利用相关的丰度差异的原因。

材料和方法

我们分析了100种土壤中微塑料的分布和丰富度，代表了土地，森林，城市（交通和居住地）和农业的主要土地利用类型，以及Ye州市的周边地区。采样区位于2.5 km×2.5 km间距的系统网格上。用手动螺旋钻收集表土（0-5厘米），并通过干燥，使用ZnCl ₂溶液的密度分离，有机物消化和减压过滤对样品进行预处理。通过使用数字体视显微镜计数来测量微塑料的丰度；微塑料按形状（碎片，薄膜，纤维和球形）和颜色（黑色，红色，绿色，蓝色，黄色，白色和透明）分组。使用傅立叶变换红外光谱（FT-IR）分析来鉴定微塑料的聚合物类型。

结果和讨论

o州的土壤平均含有700块·kg ^-1的微塑料，但这随土地利用类型而有很大差异。路边的土壤中含有更多的微塑料（1108个/ kg ^-1），主要是黑色的丁苯橡胶碎片（SBR）与轮胎灰尘有关。出乎意料的是，不是从城市土壤中而是从陆地土壤中检测到最多的微量塑料（3440个kg ^-1）。农业土壤中微塑料的平均丰度为664个kg ^-1，因农作类型而异；丰度最高的是果园，其次是高地，温室，然后是稻田。聚乙烯（PE）和聚丙烯（PP）是从高地，温室和果园地点采样的微塑料中鉴定出来的，而SBR衍生的微塑料在所有农田土壤中的分布更为广泛，这意味着覆盖膜的使用和农机具。

结论

在micro州的城市和农业土壤中，土壤中的微量塑料污染非常严重且分布广泛，但根据交通和农业的所在地，其形态和分布有所不同。对森林土壤的大气沉降进行了量化，并发现其受到微塑料的显着影响。就微生物污染对农业生态系统中土壤质量，健康和功能的影响而言，使用覆盖膜作为PE和PP的来源引起了特别关注。