聚乙烯微塑料浓度对黑土团聚体特征及其稳定性的影响

陈荣桓; 余瑶; 黄珊; 陈荣龙; 贾焮凯; 陈延华; 薛萐; 刘萌娟; 杨晓梅

doi:10.19336/j.cnki.trtb.2021122106

摘要:

目的微塑料会与土壤颗粒及团聚体相互作用而影响土壤的稳定性，探究微塑料浓度对黑土团聚体特征及其稳定性的影响，以期为农田土壤（微）塑料污染及土壤健康评价提供数据基础。

方法通过大豆盆栽实验，研究自然条件下不同微塑料浓度（0%、0.1%、0.5%、1%、2%、5%）对黑土团聚体组成、团聚体稳定性（大团聚体含量R_{> 0.25}）、土壤团聚体特征指标（平均质量直径MWD、几何均重直径GMD、分形维数FD）的影响。

结果不同微塑料浓度处理中，< 0.25 mm的机械稳定性团聚体含量比例最小，且 > 2 mm和 < 0.25 mm的团聚体含量比例随着微塑料浓度的增加而增加；> 2 mm的水稳性团聚体含量比例最小，< 0.25 mm的水稳性团聚体含量比例随着微塑料浓度的增加而增加；但在1%浓度时，机械稳定性和水稳性团聚体含量比例均与其他浓度的趋势相反；无植物种植的团聚体变化与种植物的相似。土壤大团聚体（R_{> 0.25}）的含量比例随着微塑料浓度的增加而显著减小，当微塑料浓度为1%时，其含量比例略低于对照试验（CK）。不同采样期，大豆成熟期的土壤机械稳定性团聚体和水稳性团聚体的MWD、GMD均比花期的小，而花期的团聚体分形维数比成熟期高，表明随着大豆生长及微塑料的作用，土壤团聚体稳定性降低。通过相关性分析表明，MWD与GMD呈极显著正相关关系，且二者均与FD值呈极显著负相关，即土壤团聚体MWD和GMD总体显著增大，FD值则显著减小，从而表征土壤颗粒团聚性下降。此外，当土壤中微塑料浓度为1%时，土壤团聚体分形维数最小，即土壤团聚作用增强。

结论土壤中微塑料累积浓度越高，对土壤团聚体产生的破坏作用越强，导致土壤颗粒间聚合能力减弱，土壤中微塑料浓度为1%是否可作为影响黑土团聚体稳定性变化的阈值还有待后续研究，以期为全面评估微塑料对土壤质量的影响提供依据。

Abstract:

Objective Microplastics interact with soil particles and aggregates and affect soil stability. It is of great significance to investigate the effect of microplastic concentration on the characteristics and stability of black soil aggregates,

Method Soybean pot experiment was conducted at the different microplastics concentrations l (0%, 0.1%, 0.5%, 1%, 2%, 5%) in soil under natural conditions. The indices of aggregates, such as macroaggregate content (R_{> 0.25}), mean weight diameter (MWD), geometric mean diameter (GMD) and fractal dimension (FD) of Black soil aggregates were observed and analyzed.

Result In different treatments of microplastic concentration, the content proportion of mechanical stable aggregates with particle < 0.25 mm was the lowest, and the content proportion of aggregates with particle > 2 mm and < 0.25 mm increased with the increase of microplastic concentration. The content proportion of water-stable aggregates with particle > 2 mm was the lowest, and the content proportion of water-stable aggregates with particle < 0.25 mm increased with the increase of microplastic concentration. However, the content proportion of mechanical and water stable aggregates was contrary to the trend of other concentrations in the treatment with 1% microplastic. Planting was similar to the change of aggregates without planting. The content proportion of soil macroaggregates (R_{> 0.25}) decreased significantly with the increase of microplastic concentration, except for the content proportion in treatment with 1% of microplastic addition. Regarding to the different sampling periods, the MWD and GMD of soil mechanical and water stable aggregates at soybean maturity stage were lower than that at flowering stage while FD at soybean maturity stage were greater than that at flowering stage, indicating that the stability of soil aggregates reduced with the plant and microplastic interaction. Correlation analysis showed that MWD and GMD were significantly positively correlated, and both of them were significantly negatively correlated with FD, indicating that the capacity of soil aggregating declined. In addition, our findings showed that FD was the lowest in the treatment with 1% of microplastic addition among other treatments, indicating that soil aggregate stability seems improved at this level.

Conclusion The higher the cumulative concentration of microplastics in soil is, the stronger the damage of soil aggregates will occur, and the aggregation ability of soil particles is weakened. Whether the microplastics concentration of 1% in soil could be the threshold of microplastic effect on black soil aggregate stability. Further work should be done to explore the interaction of microplastic on soil quality.

聚乙烯微塑料浓度对黑土团聚体特征及其稳定性的影响

Effect of Polyethylene Microplastic Concentration on the Characteristics and Stability of Black Soil Aggregates