Nano- and colloidal plastics in soil: input, plant uptake and risk assessment

Plastic pollution has been identified as a key to soil health.

Yet, information on inputs and concentrations in agricultural soil is limited to microplastics (> 1 m-5 mm) or larger particles, but nothing is known about submicron plastics, including colloidal plastics (CPs; 1-1000 nm) and nanoplastics (NPs; 1-100 nm), due to a lack of analytical methods.

This is critical because mainly submicron plastics harm soil biota, are taken up by plants, and thus pose a risk to human health via the food chain.

As plastic pollution is rising, we urgently need to quantify submicron plastics in agricultural soils and the resulting plant uptake and contamination of our food to safeguard our food production.

Hence, the NanoSoil project is designed to test the following hypotheses: i) submicron plastics can be routinely detected using Field Flow Fractionation (FFF) with adaptions from environmental colloid tracing, ii) agricultural practices (compost and sludge application, wastewater irrigation, plastic mulching) are main pathways for submicron plastics into soil, as well as iii) the use of so-called biodegradable foils in agriculture.

I further hypothesize that iv) uptake and accumulation of CPs and NPs in crops are polymer- and plant-specific, temperature- and humidity-dependent, with mainly NPs reaching edible parts.

To quantify submicron plastics, I will i) optimize a recently developed method using FFF and pyrolysis gas chromatography.

This method will then ii+iii) be used on soil samples from agricultural fields with known plastic input pathways for conventional and biodegradable plastics, including an Europe-wide survey and existing controlled field trials. Finally, iv) plant uptake will be assessed for representative crops.

With my combined expertise in nanoparticle and plastic analysis in soil, NanoSoil will for the first time generate data that will form the basis for all future environmental fate and ecotoxicology studies of plastics and a robust risk assessment.