Organic fertilizer from recycled biowaste was identified as a vehicle for entry of microplastic particles into the environment.

Microplastic contamination of aquatic ecosystems is a high priority research topic, whereas the issue on terrestrial ecosystems has been widely neglected. At the same time, terrestrial ecosystems under human influence, such as agroecosystems, are likely to be contaminated by plastic debris. However, the extent of this contamination has not been determined at present. Via Fourier transform infrared (FTIR) analysis, we quantified for the first time the macro- and microplastic contamination on an agricultural farmland in southeast Germany. We found 206 macroplastic pieces per hectare and 0.34 ± 0.36 microplastic particles per kilogram dry weight of soil. In general, polyethylene was the most common polymer type, followed by polystyrene and polypropylene. Films and fragments were the dominating categories found for microplastics, whereas predominantly films were found for macroplastics. Since we intentionally chose a study site where microplastic-containing fertilizers and agricultural plastic applications were never used, our findings report on plastic contamination on a site which only receives conventional agricultural treatment. However, the contamination is probably higher in areas where agricultural plastic applications, like greenhouses, mulch, or silage films, or plastic-containing fertilizers (sewage sludge, biowaste composts) are applied. Hence, further research on the extent of this contamination is needed with special regard to different cultivation practices.

Environmental context: Microplastics are of increasing environmental concern following reports that they occur worldwide from the arctic to the deep sea. However, a reliable methodology that facilitates an automated measurement of abundance and identity of microplastics is still lacking. We present an analytical protocol that applies focal plane array detector-based infrared imaging of microplastics enriched on membrane filters applicable to investigations of microplastic pollution of the environment. The pollution of the environment with microplastics (plastic pieces 10-mm diameter) of filters with microplastics from marine plankton and sediment samples. The measurement with a high lateral resolution allowed for the detection of particles down to a size of 20 μm in only a fractional part of time needed for chemical mapping. The integration of three band regions facilitated the pre-selection of potential microplastics of the ten most important polymers. Subsequent to the imaging the review of the infrared spectra of the pre-selected potential microplastics was necessary for a verification of plastic polymer origin. The approach we present here is highly suitable to be implemented as a standard procedure for the analysis of small microplastics from environmental samples. However, a further automatisation with respect to measurement and subsequent particle identification would facilitate the even faster and fully automated analysis of microplastic samples.