微塑料对稻田土壤温室气体排放和微生物群落的影响

微塑料因在土壤环境中广泛存在及其潜在的生态风险而受到越来越多的关注。微塑料的赋存会改变土壤理化性质,并对土壤微生物群落及其驱动的生物地球化学过程产生影响,而相关研究尚处于起步阶段。可生物降解塑料作为传统塑料的替代品,越来越多地应用于农业活动,并释放到土壤中。然而,可生物降解微塑料对土壤微生物特性产生影响的研究鲜有报道。基于此,本试验以我国三江平原水稻田土壤为研究对象,选取了2种常见的微塑料为试验材料,分别为传统型微塑料聚丙烯(Polypropylene,PP)和可降解微塑料聚乳酸(Polylactic acid,PLA),进行了为期41d的微宇宙培养实验,旨在分析不同浓度与类型的微塑料对土壤可溶性有机碳(Dissolved Organic Carbon,DOC)含量及官能团特征、温室气体排放以及微生物群落结构的差异性影响。结果表明,传统型微塑料PP与可降解微塑料PLA添加均对土壤理化性质与微生物群落产生显著影响。其中,微塑料添加大体上增加了土壤DOC含量,PLA的促进作用较为明显,且增加含量与微塑料添加量呈正相关;PP和PLA均影响土壤DOC分子结构,削弱了土壤团聚化程度并促进了大分子量DOC化合物的生成;微塑料的添加促进土壤CH₄排放,而有效抑制了土壤CO₂排放;微塑料显著改变了土壤细菌和真菌群落的丰富度与多样性。相关分析结果表明,土壤CO₂累计排放量与芳香族化合物结构及疏水性等官能团特征、变形菌门(Proteobacteria)与放线菌门(Actinobacteria)均呈显著正相关关系。以上结果表明,微塑料添加改变了土壤DOC含量及官能团特征与微生物环境,进而影响土壤温室气体排放。本研究为今后微塑料对土壤地球化学和微生物特性的影响研究提供了科学的思路,同时也有助于评估微塑料对土壤生态系统的生态风险。

Effect of microplastics on greenhouse gas emissions and microbial communities in paddy soils

Microplastics have received increasing attention due to their extensive presence in soil environments and the potential ecological risks. The presence of microplastics in soil can alter its physical and chemical properties, impacting the soil microbial communities and the carbon biogeochemical processes it drives. Research in this area is still in its early stages. Biodegradable plastics, as substitutes for traditional plastics, are increasingly being used in agricultural activities and subsequently released into the soil. However, there is scarce research on the impact of biodegradable microplastics on soil microbial characteristics. Based on this, this experiment took the paddy soils in the Sanjiang Plain of China as the research subjects. Two common types of microplastics were selected as experimental materials: conventional microplastic polypropylene (PP) and biodegradable microplastic polylactic acid (PLA). A 41-day microcosm cultivation experiment was conducted to analyze the differential effects of various concentrations and types of microplastics on soil dissolved organic carbon (DOC) content, functional group characteristics, greenhouse gas emissions, and microbial community structure. The results indicated that both PP and PLA had significant impacts on the soil physicochemical properties and microbial communities. In general, the addition of microplastics resulted in an increased content of DOC in the soil, with PLA having a more pronounced effect. Moreover, a significant positive correlation was observed between the increased DOC levels and the amounts of microplastics added. the effect of microplastics on soil DOC was significantly positively correlated with the amount added (P < 0.05). Both PP and PLA influenced the molecular structure of DOC, weakening the degree of soil aggregation and promoting the formation of high molecular weight DOC compounds. The addition of microplastics promoted soil methane (CH₄) emissions and effectively inhibited soil carbon dioxide (CO₂) emissions. Microplastics in the soil significantly altered the abundance and diversity of soil bacterial and fungal communities. The results of the correlation analysis indicated that the cumulative CO₂ emissions were significantly positively correlated with the structural features and hydrophobicity of aromatic compounds (P < 0.05), as well as with the phyla Proteobacteria and Actinobacteria. The results indicated that the addition of microplastics altered soil DOC content and functional group characteristics as well as the microbial environment, thereby influencing soil greenhouse gas emissions. This study can contribute to the current understanding of the ecological risks of microplastics contamination to the soil ecosystems Additionally, it provides a scientific framework for future research on the impact of microplastics on soil geochemistry and microbial characteristics.