Abstract:

Extensive use of agricultural plastic film as greenhouse and ground cover with low recycling rates results in a significant increase of plastic fragments and microplastics in the soil, consequently affecting the sustainable utilization of agricultural land. This paper focuses on the growth scale, spatial-temporal distribution, and regional differences of agricultural plastic film based on statistical yearbooks.The generation pathways, distribution of microplastics from agricultural film and potential risks of microplastic to farmland in China are analyzed and summarized.Statistical data shows that there is a continuous increase of plastic film usage in China with an annual growth rate of approximately 6.51% during 1994 to 2020. Among them, there is a peak value of usage of agricultural plastic film observed at 2015, in which ground cover film accounted for over 50.0%. Ground cover film is a dominate source of microplastics in farmland soil, especially in the northwest arid oasis regions, reaching up to 38.0 kg∙hm⁻², Microplastics from agricultural film is generally generated through natural, agricultural, and biological pathway depending on microbial activity, plastic types, and environmental conditions. Overall, the long-term planting areas in the northwest and the intensive farming areas in North China, East China, and Southwest China face serious microplastic pollution with levels reaching up to 4.83×10⁴ ind∙kg⁻¹. The porous characteristic of soil allow microplastic particles to migrate through gravity settlement and rainwater infiltration, leading to the microplastic contamination of soil, migration of other pollutants carried by them and subsequent risks to soil structure, soil flora and fauna, microbial communities, and human health. Finally, both the technical development such as raising the lower limit of thickness of polyethylene agricultural film and drawing biodegradation standards, “plastic ban/restriction” policies provide a basis for upgrading the industrial structure of agricultural plastic film, favoring plastic pollution control in China. Source prevention, development of alternative techniques, and close-loop management of agricultural plastic film are effective methods to address current agricultural film pollution, while technological upgrading will be comprehensive solution to improve agricultural plastic pollution control in the future.

Key words: mulch film, micro-plastics, soil, temporal and spatial distribution, pollution prevention and control

摘要：

农用薄膜的长期使用和低回收利用导致遗留在土壤中塑料碎片与微塑料明显增加，严重影响了农业土壤的可持续利用。重点阐述了中国1994－2020年农用地膜的增长规模、时空分布及地区差异，总结了农膜微塑料的赋存特征与生成途径，分析了中国农田土壤微塑料污染的潜在风险。数据表明：1994－2020年中国塑料薄膜用量呈大幅度上升态势，年增长率约为6.51%，农用薄膜使用量在2015年到达峰值，之后逐渐下降，地膜占总使用量的50.0%以上。地膜覆盖是农田土壤中微塑料的直接来源，区域分布来看，西北干旱绿洲区是中国地膜使用量最高的区域，使用强度最高达38.0 kg∙hm⁻²。农膜微塑料的生成是残留地膜在自然、农业和生物多种途径共同作用的结果，其速率主要取决于微生物和塑料类型及环境条件。西北长期种植区及华北、华东和西南集约农区是中国微塑料污染较严重区域，最高可达4.83×10⁴ ind∙kg⁻¹。土壤的多孔特性使小颗粒微塑料通过重力沉降和降水渗透发生迁移，造成土壤微塑料污染及其携带的其他污染物的迁移扩散，对土壤结构、土壤动植物、微生物群落及人体健康造成不同程度的潜在风险。从中国农业“禁/限塑”政策与农膜、（微）塑料标准化检测发展历程来看，聚乙烯农膜厚度下限的提高和一系列生物降解标准的出台，为农用覆盖薄膜产业结构的调整与升级提供了基础，对于中国塑料污染治理工作起到了促进作用。当前，源头防控、替代技术和闭环管理是解决农用薄膜污染有效的措施，未来需要借助技术创新提升治理能力全面提升农业领域的塑料污染治理。

关键词: 地膜, 微塑料, 土壤, 时空分布, 污染治理