State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
Department of Environmental Science, University of California, Riverside, CA 92521, USA.
Sci Total Environ. 2022 Oct 20;844:156853. doi: 10.1016/j.scitotenv.2022.156853. Epub 2022 Jun 22.
Microplastics in agricultural soils have become the research hotspot in recent years, however, the quantitative methods based on the traditional visual inspection may have a high false detection rate. Here we combined the laser direct infrared (LDIR) and Fourier-transform infrared (FTIR) methods to investigate the microplastics in farmland with long-term agricultural activities. The results showed that the total abundance of microplastics reached 1.98 ± 0.41 × 10, 1.57 ± 0.28 × 10, 1.78 ± 0.27 × 10, and 3.20 ± 0.41 × 10 particles/kg soil in cotton fields with film mulching of 5, 10, 20, and >30 years, respectively. LDIR results indicated that microplastics ranging from 10 to 500 μm accounted for 96.5-99.9 % of the total microplastic amounts in the soils. Additionally, a total of 26 polymer types of microplastics were detected, among which polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyamide (PA), and polytetrafluoroethylene (PTFE) were dominantly observed. For the microplastics detected by FTIR (500 μm-5 mm), PE polymer was majorly observed (88.0-98.9 %). Most microplastics were films (88.2 %), while fibers and pellets were also found. The reclaimed water from sewage treatment plants, the drip irrigation utilities, and the residual plastic film are the potential sources of microplastics in the farmland soils. By using the automated quantitative and identifiable approaches, this study suggested that the commonly used visual counting method may underestimate the microplastic contamination in agricultural soils.
农田土壤中的微塑料已成为近年来的研究热点，但基于传统目视检查的定量方法可能存在较高的假阳性率。本研究结合激光直接红外（LDIR）和傅里叶变换红外（FTIR）方法，调查了长期进行农业活动的农田中的微塑料。结果表明，覆膜棉田的微塑料总丰度分别达到了 1.98±0.41×10^5、1.57±0.28×10^5、1.78±0.27×10^5和 3.20±0.41×10^5 个/千克土壤。LDIR 结果表明，粒径在 10-500μm 之间的微塑料占土壤中总微塑料量的 96.5-99.9%。此外，共检测到 26 种类型的微塑料，其中聚乙烯（PE）、聚丙烯（PP）、聚氯乙烯（PVC）、聚酰胺（PA）和聚四氟乙烯（PTFE）占主导地位。FTIR 检测到的（500μm-5mm）微塑料主要为 PE 聚合物（88.0-98.9%）。大多数微塑料为薄膜（88.2%），也发现了纤维和颗粒。污水处理厂的再生水、滴灌设施和残留的塑料薄膜是农田土壤中微塑料的潜在来源。本研究采用自动化定量和可识别方法，表明常用的目视计数方法可能低估了农业土壤中的微塑料污染。
