From plastic mulching to microplastic pollution : An effect assessment of microplastics in the soil-plant system

Abstract

Effect of plastic mulching on the accumulation and distribution of macro and micro plastics in soils of two farming systems in Northwest China 23 Effect of plastic mulching on the accumulation and distribution of macro and micro plastics in soils of two farming systems in Northwest China 25Effect of plastic mulching on the accumulation and distribution of macro and micro plastics in soils of two farming systems in Northwest China 29Effect of plastic mulching on the accumulation and distribution of macro and micro plastics in soils of two farming systems in Northwest China 31 calculated by image J, 1 pixel = 0.585/60 mm (microscope at 6.4 X Zoom). The picture of the setup for identification MPs is presented in supplementary Figure S2.5. Limitation of microplastic extraction methodOnly MPs from LDPE or MPs with density < 1 g•cm -3 were able to be extracted due to the water reagent. MPs with densities higher than 1 g•cm -3 (e.g. PVC 1.45 g•cm -3 ) were not able to be extracted (Nuelle et al., 2014). However, this method provides a validated method for estimating the presence of LDPE-MPs in the soil. Data analysisThe arcsine square root transformation was applied to the mass and number of MaPs pieces to avoid violating the underlying assumptions of normality. One-way analyses of variances (ANOVAs) were applied to compare the mass and number of MaPs pieces between different fields within the same selected region and different soil layers within the same field, followed by the application of an LSD post hoc test at the p < 0.05 level. MaPs mass (kg•ha -1 ) and number (p•ha -1 ) were presented as "means ± standard deviations". MPs that were detected in the fields were presented in raw data in the unit of p•kg -1 soil due to the highly random distribution of the particles and no statistical test was performed.