Abstract
Soil erosion is a potentially important source of microplastic (MP) entering aquatic ecosystems. However, little is known regarding the erosion and transport processes of MP from agricultural topsoils. The aim of this study is to analyze the erosion and transport behavior of MP during heavy rainfall events, whereas a specific focus is set to preferential MP transport and MP-soil interactions potentially leading to a more conservative transport behavior. The study is based on a series of rainfall simulations on paired-plots (4.5 m × 1.6 m) of silty loam and loamy sand located in Southern Germany. The simulations (rainfall intensity 60 mm h−1) were repeated 3 times within 1.5 years. An amount of 10 g m−2 of fine (MPf, size 53–100 μm) and 50 g m−2 of coarse (MPc, size 250–300 μm) high-density polyethylene as common polymer was added to the topsoil (<10 cm) of the plots. The experiments show a preferential erosion and transport of the MP leading to a mean enrichment ratio of 3.95 ± 3.71 (MPc) and 3.17 ± 2.58 (MPf) in the eroded sediment. There was a higher MP enrichment on the loamy sand but a higher sediment delivery on the silty loam resulting in nearly equal MP deliveries from both soil types. An increasing interaction with mineral soil particles or aggregates leads to a decreasing MP delivery over time. Within 1.5 years, up to 64% of the eroded MP particles were bound to soil particles. Overall, more of the MPc was laterally lost via soil erosion, while for the MPf the vertical transport below the plough layer was more important. In general, our study indicates that arable land susceptible to soil erosion can be a substantial MP source for aquatic ecosystems.
Highlights
In the Anthropocene, plastic has replaced many traditional materials such as wood, glass and metal
The study is based on a series of rainfall simulations on paired-plots (4.5 m × 1.6 m) of silty loam and loamy sand located in Southern Germany
In case of the MP particles tested in our experiment we found preferential erosion and transport in comparison to the mineral soil, reflected in a mean enrichment ratio > 1 during all rainfall simulation (RS) (Fig. 5)
Summary
In the Anthropocene, plastic has replaced many traditional materials such as wood, glass and metal. Soil contamination should be treated with the same global concern as marine and freshwater ecosystems, since arable soils alone are likely to contain more MP than the oceans (de Souza Machado et al, 2018; Nizzetto et al, 2016b; Rillig and Lehmann, 2020). Whether the accumulation of MP in the soil leads to a permanent sink (until the plastic disintegrates after centuries), or is lost again through leaching into the groundwater or through surface runoff and erosion, is often discussed, but it is hardly quantified (Mai et al, 2018; Nizzetto et al, 2016a; Rillig et al, 2017a). In the Rhône River, a peak in plastic transport was measured a few days after precipitation events, indicating that surface runoff may have an important effect of MP input to water bodies compared to other processes (Castro-Jiménez et al, 2019)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
