摘要
摘要:近年来, 微塑料污染成为全球关注的热点问题。在农田生态系统中地膜覆盖、灌溉用水、有机肥施用等措施在提升作物产量的同时, 都会导致塑料残留。因耕作和紫外线辐射, 残留塑料逐步破碎降解, 形成微塑料(直径<5 mm), 进入土壤、作物与食物链系统, 威胁生态系统健康。本文系统总结了农田微塑料的来源、丰度、迁移特点和检测方法, 重点关注了微塑料在农田生态系统中对作物生长发育、微生物活性、土壤养分循环及温室气体排放等方面的影响。微塑料对作物-土壤-微生物系统产生的主要影响为: 1)微塑料含有的毒性添加剂(即增塑剂)与携带的有害物质(如有机污染物、重金属和病原体)随塑料颗粒在土壤中迁移, 可改变土壤理化性质, 并为微生物提供新生态栖息地, 对作物生长、土壤酶和微生物活性造成影响; 2)微塑料含有大量碳(通常约为90%), 影响其他元素(如氮和磷)循环, 进而影响微生物活性。土壤性质改变也间接影响CO₂、N₂O和CH₄形成。由于聚合物类型、大小、形状和浓度的高度可变性, 微塑料对作物生产和土壤生物地球化学过程的影响及其机制有待深入探究。本文还展望了未来农田生态系统微塑料的研究方向和重点。
关键词:微塑料/
农田生态系统/
作物/
微生物/
土壤养分循环
Abstract:Microplastics (MPs) pollution has attracted global attention in recent years. Despite the remarkable benefits arising from the production of plastic for film mulching, irrigation, and organic fertilizer application, there are increasing concerns associated with the vast amount of plastic entering the agroecosystems and its subsequent potential environmental problems. More specifically, MPs (particles<5 mm in size), typically formed from the disintegration of larger plastic debris by tillage and UV radiation, accumulate in agroecosystems and eventually enter the food chain, threatening human and animal health. On the basis of the current evidence, we summarized the source, abundance, mitigation, and detection methods of MPs in agroecosystems. We evaluated the potential ecological risks of MPs to crop growth, microbial activity, soil nutrient cycling, and greenhouse gas emissions. It is found that MPs could either directly or indirectly impact the plant-soil-microbe interactions once incorporated into soil, through the following mechanisms: First, owing to their chemical inertia and structural characteristics, MPs have been recognized as carriers of hazardous substances (e.g., organic pollutants, heavy metals, and pathogens), in addition to their toxic additives (i.e., plasticizers). After making contact with the soil, the migration of plastic particles likely facilitates the transport of sorbed contaminants and contributes to a great ecological risk for crop growth, enzyme activity, and microbial activity. MPs could also alter soil physicochemical properties, that is, they may change the soil aggregation stability, bulk density, and water holding capacity, resulting in diverse effects on microbial functions and plant growth. MPs could also serve as a novel ecological habitat for microorganisms living at the soil-plastic interface (i.e., microplastic spheres), allowing the formation of unique microbial communities. The second mechanism involves the fact that MPs are particles that contain a high carbon content, typically around 90%, making them relatively unique in relation to other pollutants as they can drive diverse consequences for other element cycles (e.g., nitrogen and phosphorus). Direct effects are likely to be minimal because MPs contain mostly negligible amounts of nitrogen and phosphorus. However, alterations in soil structure and physicochemical properties would be expected to change microbial processes, including the nitrogen and phosphorus related enzymes, since soil properties indirectly control soil oxygen availability, which in turn influences CO₂, N₂O, and CH₄ formation. Due to the high degree of variability in polymer type, size, shape, and concentration, the impacts of MPs on soil biogeochemical processes and their underlying mechanisms remain unclear, and further detailed research is therefore needed. Thus, we propose some research priorities regarding the future challenges of MPs in agroecosystems.
Key words:Microplastics/
Agroecosystems/
Crops/
Microorganisms/
Soil nutrient cycle



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