| 摘要: |
| 【目的】研究微塑料对农田土壤团聚体稳定性和有机碳矿化的影响，为农膜高残留农地土壤结构的稳定性和农业生态风险评价提供理论依据。【方法】在陕西省延安市安塞县采集低有机质水平的农田土壤（CK），通过添加有机肥后得到高有机质水平土壤（S），在以上2种有机质水平土壤中分别添加不同含量（0.06，0.64，1.92，3.20，6.40 g/kg）、粒径分别为25 μm和1 mm的聚乙烯微塑料（PE-MPs），以不添加微塑料的CK和S作为对照，制成土壤团聚体后进行室内培养，测定水稳性团聚体含量、平均重量直径、微生物量碳含量及有机碳矿化速率，并构建结构方程模型量化微塑料粒径、含量及土壤有机质水平对土壤团聚体稳定性的影响。【结果】①与对照组CK相比，在低有机质水平的土壤中添加0.06 g/kg粒径25 μm PE-MPs后1~5个月，水稳性团聚体含量明显增加，增幅最大可达24.98%；添加粒径1 mm PE-MPs，培养1个月后土壤水稳性团聚体含量增加，培养3~5个月后土壤水稳性团聚体含量降低。与对照组S相比，在高有机质水平土壤中添加粒径25 μm PE-MPs培养1~5个月后，水稳性团聚体含量总体无显著变化；添加粒径1 mm PE-MPs培养1~5个月后，水稳性团聚体含量总体有所提高。②添加25 μm PE-MPs，可使高、低有机质水平土壤团聚体的有机碳矿化速率最大分别提高15.84%和38.64%，添加1 mm PE-MPs会导致团聚体土壤有机碳矿化速率降低，最大降幅达33.17%。③构建的结构方程模型显示，微塑料粒径、含量及土壤有机质水平会通过影响有机碳矿化速率和土壤微生物碳含量，进而间接影响粒径≥0.25 mm水稳性团聚体含量（WR0.25），以上三者对WR0.25的总效应系数分别为0.065，-0.055和0.310。【结论】PE-MPs会降低低有机质贫瘠土壤的团聚体稳定性，增加土壤结构退化的风险;但可增强高有机质水平土壤的团聚体稳定性。 |
| 关键词: 微塑料残留 土壤有机质 团聚体 有机碳矿化 |
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| 基金项目:国家自然科学基金项目（42177345) |
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| Effects of microplastics on soil aggregate stability and soil organic carbon mineralization |
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LI Shujie,ZUO Zhenjiang,HAO Wanglin,et al
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| Abstract: |
| 【Objective】This study explored the effects of microplastics on stability of farmland soil aggregates and organic carbon mineralization to provide basis for soil structure stability and agro-ecological risk assessment of farmland with high agricultural film residues.【Method】Farmland soil with low organic matter level (CK) was collected in Ansai County,Yan’an,Shaanxi,and the soil with high organic matter level (S) was obtained by the addition of organic fertilizer.Soil aggregates were obtained by adding polyethylene microplastics (PE-MPs) at different levels (0.06,0.64,1.92,3.20 and 6.40 g/kg) with particle sizes of 25 μm and 1 mm,respectively.CK and S without microplastics were used as controls.Soil aggregates were cultured indoors.Then,the content of water stability aggregates,mean weight diameter,content of microbial biomass carbon and the rate of organic carbon mineralization were determined.The structural equation model was constructed to quantify the effects of microplastic particle size,concentration and soil organic matter level on soil aggregates.【Result】① Compared with CK,the addition of 0.06 g/kg 25 μm PE-MPs to soil with low organic matter level increased the content of water stable aggregates significantly after 1-5 months,with a maximum increase of 24.98%.The addition of 1 mm PE-MPs increased the content of soil water stable aggregates after 1 month,while decreased it after 3-5 months.Compared with S,there was no significant change in the content of water stable aggregates after 1-5 months in soils with high organic matter level by adding 25 μm PE MPs.The content of water stable aggregates was increased by adding 1 mm PE-MPs after 1-5 months.② The addition of 25 μm PE-MPs increased the mineralization rate of organic carbon in high and low organic matter level soil aggregates by 15.84% and 38.64%.The addition of 1 mm PE-MPs decreased the mineralization rate of soil organic carbon in soil aggregates,with a maximum decrease of 33.17%.③ The constructed structural equation model showed that size and content of microplastic particle and level of soil organic matter indirectly affected WR0.25 by influencing the mineralization rate of organic carbon and the content of microbial biomass carbon,and the total effect coefficients were 0.065,-0.055 and 0.310,respectively.【Conclusion】PE-MPs reduced the stability of poor soil aggregates with low organic matter levels and increased the risk of soil structural degradation,while enhanced the stability of soil aggregates with high organic matter levels. |
| Key words: microplastics residue soil organic matter aggregates organic carbon mineralization |
