Yu Yongxiang, Zhang Zihan, Zhang Yanxia, Jia Hongtao, Li Yaying, Yao Huaiying
Research Center for Environmental Ecology and Engineering, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, 206 Guanggu 1st road, Wuhan 430205, China; Key Laboratory of Urban Environment and Health, Ningbo Observation and Research Station, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Zhejiang Key Laboratory of Urban Environmental Processes and Pollution Control, CAS Haixi Industrial Technology Innovation Center in Beilun, Ningbo 315830, China.
Research Center for Environmental Ecology and Engineering, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, 206 Guanggu 1st road, Wuhan 430205, China.
Chemosphere. 2023 Mar;316:137837. doi: 10.1016/j.chemosphere.2023.137837. Epub 2023 Jan 11.
Plastic mulched agricultural fields in Xinjiang are regarded as potential "hotspots" of microplastic (MP) contamination in China, whereas the abundance of MPs in this region is still unclear. As a carbonaceous material, current conventional methods for measuring soil organic carbon (SOC) generally do not separate the MPs from soils, which probably overestimated the soil carbon (C) sequestration. In this study, 77 agricultural soil samples under plastic film mulching were collected in Xinjiang. Afterward, the average abundance of agricultural MPs and the contribution of microplastic-carbon (MP-C) to the SOC pool were evaluated. The abundance of MPs was 12,589 pieces kg soil (ranging from 4198 to 47,420 pieces kg soil), and small-sized (<0.5 mm) plastic particles accounted for 93.3% of the total MPs. Interestingly, the soil salt content was positively related to the proportion of 0.1-0.5 mm MP but negatively correlated with the proportion of 0.02-0.1 mm MP, indicating that soil salinization probably controlled the degradation process of plastic residues. The average content of MP-C in the 0-20 cm layer was 25.33 kg ha (ranging from 1.60 to 192.57 kg ha), which had a contribution of 1.59‰ (ranging from 0.05 to 14.24‰) to the SOC pool. Accordingly, we roughly estimated that the MP-C storage (0-20 cm layer) was approximately 88.66 Gg in the plastic film mulching fields of Xinjiang. Although MP is undeniably organic C, this environmental pollution cannot be regarded as "true" soil C storage, which induces the overestimation of soil C sequestration in agricultural fields. Therefore, our results highlighted that MP-C should be subtracted when estimating SOC sequestration in plastic film mulching fields of Xinjiang.
新疆的地膜覆盖农田被视为中国微塑料（MP）污染的潜在“热点”地区，然而该地区微塑料的丰度仍不明确。作为一种含碳物质，目前测量土壤有机碳（SOC）的传统方法通常不会将微塑料从土壤中分离出来，这可能高估了土壤碳（C）固存。在本研究中，在新疆采集了77个地膜覆盖下的农业土壤样本。随后，评估了农业微塑料的平均丰度以及微塑料碳（MP-C）对SOC库的贡献。微塑料的丰度为每千克土壤12589个（范围为每千克土壤4198至47420个），小尺寸（<0.5毫米）塑料颗粒占微塑料总量的93.3%。有趣的是，土壤盐分含量与0.1 - 0.5毫米微塑料的比例呈正相关，但与0.02 - 0.1毫米微塑料的比例呈负相关，这表明土壤盐渍化可能控制着塑料残留物的降解过程。0 - 20厘米土层中MP-C的平均含量为每公顷25.33千克（范围为每公顷1.60至192.57千克），对SOC库的贡献为1.59‰（范围为0.05至14.24‰）。据此，我们粗略估计新疆地膜覆盖农田中MP-C储量（0 - 20厘米土层）约为88.66千兆克。虽然微塑料不可否认是有机碳，但这种环境污染不能被视为“真正的”土壤碳储存，这会导致对农田土壤碳固存的高估。因此，我们的结果强调，在估算新疆地膜覆盖农田的SOC固存时应减去MP-C。
