Model based estimation of regional microplastic emissions from agriculture in Germany

, Henseler Martin, Brandes Elke, Kreins Peter.

The topic of microplastic (MP) contamination in agricultural soils has recently gained attention in science and society. Experimental studies indicate that microplastic (i.e., plastic particles ¡ 5mm) can have negative effects on soil physical properties and ecology, but an actual impairment of soil functions at current concentration levels in agricultural soils has yet to be shown. The most discussed agricultural sources for MP contamination of cropland are biosolids (sewage sludge and compost) applied as soil amendment to fields, as well as plastic film used in plasticulture. However, knowledge about how much MP has been accumulating in agricultural soils is scarce. Due to methodological challenges, MP analysis of field samples will continue to provide mainly point information in the foreseeable future. To quantify the various MP sources and pathways within and across ecosystems, data-driven models present crucial tools to scale up these analytic results to a landscape level and to simulate effects of mitigation measures. Some recent modelling studies have estimated MP emissions based on production and consumption statistics at national level. However, spatially explicit regional quantification of microplastic immissions into agricultural soils are virtually missing in the scientific literature. Using data on MP concentrations in biosolids from the literature in combination with national and regional statistics on sewage sludge, compost and organic waste production, as well as specialty crop areas, we estimated the spatial distributions of MP mass contents in agricultural soils in Germany originating from agricultural activities. Although these estimates are based on limited data availability, our results provide first indications about locations where detailed soil analysis could be useful to investigate in situ processes and impacts. The methodology can be applied to other regions and continuously adapted when more knowledge on relevant sources, transport, accumulation, and degradation rates of MP in soils will be gained in the future.

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