微塑料对亚热带不同富铁程度红壤团聚体稳定性及碳氮磷化学计量特征的影响

Effects of microplastics on stability of aggregates and stoichiometric characteristics of carbon,nitrogen,phosphorus in subtropical red soils with different iron enrichment degrees

【目的】探究微塑料对不同富铁程度红壤结构和碳氮磷化学计量特征的影响,为指导红壤地区土壤质量提升和污染管理提供理论依据。【方法】以亚热带红壤为研究对象,通过室内培养试验添加0、0.1%、1.0%质量的低密度聚乙烯(M_(0)、M_(1)、M_(2))和0、10、20 g/kg质量的铁(Fe_(0)、Fe_(1)、Fe_(2))分别模拟微塑料的污染水平和红壤富铁程度,研究不同富铁条件下微塑料污染红壤的水稳性团聚体分布特征和碳氮磷化学计量特征。【结果】在Fe_(0)条件下,与M_(0)相比,M_(1)的粒径>0.25 mm团聚体含量(WSA)、平均重量直径(MWD)和几何平均直径(GMD)均降低,M_(2)的WSA、MWD、GMD均显著增高;在Fe_(1)条件下,M_(0)、M_(1)和M_(2)三者的团聚体稳定性指标均显示彼此之间没有显著性差异;在Fe_(2)条件下,M_(1)和M_(2)均可显著降低土壤团聚体的WSA、MWD和GMD。对碳氮磷含量及其化学计量特征而言,Fe_(0)条件下M_(1)和M_(2)可显著提高土壤有机碳含量(SOC);Fe_(1)和Fe_(2)条件下微塑料处理对SOC没有显著影响。土壤全氮含量(TN)则为Fe_(0)和Fe_(1)条件下M_(1)和M_(2)均显著降低,但Fe_(2)条件下微塑料处理对TN无显著性影响;土壤全磷含量(TP)均表现为M_(0)>M_(1)>M_(2)。土壤养分变化最终导致所有微塑料处理的C/N、C/P、N/P均显著升高(Fe_(0) M_(1)、Fe_(2) M_(1)和Fe_(2) M_(2)除外)。【结论】不同处理对土壤团聚体稳定性的影响效果不尽相同。在当前原状红壤条件下,低微塑料污染可以降低土壤团聚体的稳定性,高微塑料污染则可以增加土壤团聚体的稳定性。在相对轻富铁红壤条件下,低、高微塑料污染对土壤团聚体稳定性均无显著性影响。在相对高富铁的红壤条件下,低、高微塑料污染均可降低土壤团聚体稳定性。土壤团聚体结构的变化致使土壤的碳氮磷化学计量特征也产生了较明显的差异,总体呈现为微塑料污染可显著提升红壤的C/N、C/P、N/P。

【Objective】The present paper aimed to investigate the effects of microplastics on the structure and carbon,nitrogen,phosphorus stoichiometric characteristics of red soil with different levels of iron enrichment,and to provide theoretical basis for guiding the improvement of soil quality and pollution management in red soil areas.【Method】Using subtropical red soil as the research object,low density polyethy⁃lene(M_(0),M_(1),M_(2))with 0,0.1%,1.0%mass and iron(Fe_(0),Fe_(1),Fe_(2))with 0,10 and 20 g/kg mass were added through indoor cultivation experiments to simulate the pollution level of microplastics and the degree of iron enrichment in red soil.The distribution characteris⁃tics of water stable aggregates and the stoichiometric characteristics of carbon,nitrogen and phosphorus in red soil polluted by microplastics under different iron enrichment conditions were studied.【Result】Under the condition of Fe_(0),compared with M_(0),the aggregate content(WSA),mean weight diameter(MWD)and geometric mean diameter(GMD)of M_(1) with particle size>0.25 mm decreased,and the WSA,MWD and GMD of M_(2) increased significantly;Under Fe_(1) conditions,there was no significant difference in the stability indicators of aggregates among M_(0),M_(1) and M_(2);Under Fe_(2) conditions,both M_(1) and M_(2) significantly reduced the WSA,MWD and GMD of soil aggre⁃gates.In terms of carbon,nitrogen and phosphorus content and their stoichiometric characteristics,M_(1) and M_(2) under Fe_(0) conditions could significantly increase soil organic carbon content(SOC);Under Fe_(1) and Fe_(2) conditions,microplastic treatment had no significant effect on SOC.The total nitrogen content(TN)of the soil decreased significantly under Fe_(0) and Fe_(1) conditions,while microplastic treatment had no significant effect on TN under Fe_(2) conditions;The total phosphorus content(TP)of the soil showed M_(0)>M_(1)>M_(2).The changes in soil nu⁃trients ultimately led to a significant increase in C/N,C/P and N/P of all microplastic treatments(except for Fe_(0)M_(1),Fe_(2)M_(1) and Fe_(2)M_(2)).【Conclusion】The effects of different treatments on the stability of soil aggregates vary.Under the current existing red soil conditions,low mi⁃cro plastic pollution can reduce the stability of soil aggregates,while high micro plastic pollution can increase the stability of soil aggregates.Under relatively light iron rich red soil conditions,both low and high microplastic pollution have no significant impact on the stability of soil aggregates.Under relatively high iron rich red soil conditions,both low and high microplastic pollution can reduce the stability of soil aggre⁃gates.Moreover,the changes in soil aggregate structure under different treatments led to significant differences in the stoichiometric charac⁃teristics of carbon,nitrogen and phosphorus in the soil.Overall,microplastic pollution can significantly improve the C/N,C/P and N/P of red soil.