Microplastics in vineyard soils: First insights from plastic-intensive viticulture systems

In the terrestrial environment, microplastics in specialty cropping systems have not been studied so far. Viticulture as a potential plastic-intensive management form and a land use with high erosion risks, plays an important role in transport and distribution of material to other terrestrial and aquatic systems. This paper is a first investigation of microplastics in vineyard soils, assessing the spatial distribution and composition of microplastics in organically and conventionally managed viticulture, and relates it to the macroplastic collected at the vineyards. Topsoils (0-10, 10-30 cm) and plastic particles on soil surfaces from eight vineyard lots were sampled. Four of the vineyards were under organic and four underconventional management and they were all located in the Moselle and Saar Wine Region (Rhineland-Palatinate, Germany). Microplastic analysis was performed via μFTIR chemical imaging after wet-chemical microplastic extraction from soil samples. The mean microplastic concentration was 4200 ± 2800 p kg^-1 (mean ± SD), with detected mean sizes of 230 μm ± 300 μm. Most abundant polymers were PP (35.2 %), PA (25.3 %) and PE (15.5 %). The distribution pattern showed higher microplastic concentration in topsoil, at middle and bottom slope position. The smallest particle sizes were found in subsoil samples and bottom position. Thus, erosion is assumed to be a potential downhill transport pathway. According to our dataset, management seems to have no significant influence on microplastic abundance, but affects polymer composition. Polymer composition of micro- and macroplastics partly coincide, thus in-situ fragmentation, is considered the major input source. Based on our findings, we recommend further investigation of plastic pathways in speciality crop systems like viticulture.