Prediction of future microplastic accumulation in agricultural soils

Summary

Using 176 years of soil data from the Broadbalk winter wheat experiment at Rothamsted Research, this analysis reveals exponential accumulation of microplastics in agricultural soils, accelerated significantly by inorganic fertiliser application. Poisson regression models forecast that fertilised soils will accumulate to 169 mg kg⁻¹ within 50 years and over 1159 mg kg⁻¹ within 100 years, approaching concentrations used in experimental studies. The findings underscore the urgency of mitigation strategies and inform the design of global change experiments.

Regional applicability

This study is directly applicable to United Kingdom conditions, being based on long-term Rothamsted Research trials conducted at a single location in south-eastern England. The findings are most transferable to similar temperate arable systems in northern Europe; applicability to other climates or farming systems would require validation, though the exponential trend may be widespread given the ubiquity of agricultural inputs worldwide.

Key measures

Annual microplastic accumulation rate (counts and mass per kg soil, w/w); projected microplastic concentrations at 50 and 100 years; 95% confidence intervals

Outcomes reported

The study quantified exponential accumulation of microplastics in agricultural soils from 1846–2022 and projected future concentrations under different fertiliser regimes using Poisson regression modelling. Forecasts indicated fertilised soils will reach 168.9 mg kg⁻¹ in 50 years and 1159 mg kg⁻¹ in 100 years.

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