多场次模拟暴雨下3种草坪坡地微塑料迁移特征

Migration Characteristics of Microplastics in Three Kinds of Lawn Slope Land Under Multiple Simulated Rainstorm

[目的]探明降雨径流和水分入渗下的微塑料在坡地草坪内的迁移特征,为草坪截存微塑料估算及城市草坪选择提供依据。[方法]通过人工模拟多场暴雨,在径流小区上研究了3种坡地草坪微塑料的径流迁移和土内垂直迁移特征。[结果]绝大多数微塑料保留在草地内;微塑料迁移量随着径流的增加和消减阶段而相应变化,但径流稳定阶段微塑料迁移量呈波动式下降趋势;随着降雨场次的增加,微塑料迁移量及其波动显著降低;微塑料粒径减小其径流迁移量增大,但小于0.5 mm后微塑料迁移量无差异。微塑料向土内最大迁移深度集中在15 cm内;随着降雨场次增加,迁移深度无明显增加;迁移粒径主要是<0.25 mm的微塑料,但其10 cm以下迁移量不足0—5 cm的1%,0—5 cm土壤内微塑料在上坡位淋失,在下坡位富集。[结论]微塑料迁移与径流过程和水分入渗规律并不完全一致,且短期降雨引起的微塑料水平和垂直迁移比较少,白三叶草地微塑料的迁移量最少,黑麦草草地最多,狗牙根的水平迁移和垂直迁移量居中。

[Objective]Exploring the migration characteristics of microplastics under rainstorm runoff and water infiltration in sloping lawns,providing a basis for estimating the interception of microplastics in lawns and selecting urban lawns.[Methods]The characteristics of microplastic migration with runoff and vertical migration in soil of three kinds of sloping grassland were studied on runoff plots by artificial simulation of multiple rainstorms.[Results]The vast majority of microplastics remained in the grassland.The migration quantity of microplastics changed with the increase and decrease of runoff,but the migration of microplastics in the stable stage of runoff showed a fluctuating downward trend.With the increase of rainfall events,the migration and fluctuation of microplastics decreased significantly.The runoff migration increased with the decrease of microplastic particle size,but there was no difference in the migration of microplastics when the particle size was less than 0.5 mm.The vertical migration depth of microplastics concentrated within 15 cm.With the increase of rainfall,the depth did not increase significantly.The particle size of microplastics with vertical migration was mainly<0.25 mm,and the migration amount below 10 cm was less than 1%of 0—5 cm.The microplastics in 0—5 cm soil leached in the uphill position and enriched in the downhill position.[Conclusion]Short-term rainfall causes less horizontal and vertical migration of microplastics,and the migration of microplastics in white clover grassland is the least,is the most in ryegrass grassland,and the horizontal migration and vertical migration in Bermuda grass are in the middle.