Effect of microplastics on silty loam soil properties and radish growth

Abstract

Microplastics (particles of plastics <5 mm) affect the physical, biological and hydrological properties of agricultural soil, as well as crop growth. We investigated the effect of the addition of three microplastics (high-density polyethylene (HDPE), polyvinyl chloride (PVC), and polystyrene (PS)) at a concentration of 5% (w/w) to a silty loam soil on selected soil properties and growth of radish (Raphanus sativus L. var. sativus). Changes in the soil properties and radish growth in three microplastic treatments were compared with the control. Soil properties (bulk density, hydraulic conductivity, sorptivity, water repellency) were estimated for each treatment at the beginning and at the end of the radish growing period (GP). The bulk density was significantly lower in the HDPE and PVC treatments compared to the control within the measurement at the beginning of the GP and in all microplastic treatments compared to the control at the end of the GP. The values of hydraulic conductivity and water sorptivity did not show significant differences between any treatments within the measurement at the beginning of GP, but they were significantly higher in the HDPE treatment compared to the control at the end of the GP. The growth of radish was characterized by the plant biomass and effective quantum yield of Photosystem II (Y (II)). We did not find a statistically significant difference in the total biomass of radish between any of the experimental treatments, maybe due to used concentration of microplastics. The mean value of Y (II) was significantly higher in all microplastic treatments compared to control only within the last measurement at the end of the GP. A statistically significant change of Y(II) in all microplastic treatments may indicate functional shift in soil properties; however, the measured values of the soil characteristics have not shown the significant changes (except for the bulk density values in all microplastic treatments and hydraulic conductivity together with sorptivity in HDPE treatment within the measurement at the end of GP).

Assessing Microplastic-Induced Changes in Sandy Soil Properties and Crop Growth

“…Hydraulic conductivity, which represents the ability of water to move through the soil, was significantly decreased in the HDPE and PVC treatments, supporting the hypothesis that microplastics decrease hydraulic conductivity. These results contrast the findings of our previous research in silt loam soil [15], suggesting that the impact of microplastics on hydraulic conductivity may vary depending on soil texture and the degree of water repellency induced by microplastics. The increased soil water repellency observed in this study indicates that water infiltration is impeded, potentially resulting in reduced water saturation and altered flow paths.…”

“…Our previous research in silty loam soil [15] revealed that all three types of microplastic contamination (HDPE, PVC, and PS) significantly reduced the bulk density measured after the growing period (GP), while HDPE treatment increased hydraulic conductivity and water sorptivity. Statistically significant changes in soil water repellency (SWR) and radish growth in the microplastic treatments were not observed at the end of GP.…”

Minimal Impacts of Microplastics on Soil Physical Properties under Environmentally Relevant Concentrations

“…Similar to that found in our study, Botyanszká et al reported a generally insignificant increase in soil water repellency in terms of water drop penetration time, when 5% w/w of polyethylene (<400 μm), polyvinyl chloride (<400 μm), and polystyrene (<400 μm) granules were added into a silt loam soil. However, a significant increase in water repellency has been reported by Cramer et al, who found that the contact angle of quartz sand increased from 30° to 40° and 50° by the amendment of polyethylene terephthalate granules (25–75 μm) at concentrations of 0.35 and 1.05% w/w, respectively.…”

“…Normality and equal variance assumptions were met by the data as assessed with Shapiro-Wilk's test and Levene's test, respectively. Statistical analyses were done with R. 26…”

Interactions of natural and anthropogenic drivers and hydrological processes on local and regional scales: A review of main results of Slovak hydrology from 2019 to 2022

“…Laboratory and field research on the shrinking and swelling processes in heavy soils was focused on the East Slovakian Lowland. Botyanszká et al (2022) investigated the effect of the microplastics in silty loam soil on selected soil properties and the growth of radishes. Still, the measured values of the soil characteristics have not shown significant changes.…”