Plastic pollution has become a growing concern for environmental and human’s health in recent years. Their presence in aquatic ecosystems has long been revealed, but lately research suggests that the soil compartment might be highly polluted as well, with compost being one of the major sources or pathways for plastic pollution, especially at reduced sizes. In Geneva, microplastic pollution was already evaluated in industrial compost, but the situation about field side compost was not yet explored. Therefore, this work focused on the evaluation of concentrations and characterisation of microplastic particles in field side composts in Geneva. Four different field side composts were sampled in Geneva and sieved with sizes from > 5 mm until 63 µm. The fractions sizes handleable with tweezer were visually sorted, and the smaller ones were treated with degradation and density separation processes. All the icroplastic particles were analysed with infrared spectroscopy.

The results revealed concentrations between 19.5 and 131.5 microplastic particles per 100 g of compost, and the presence of conventional plastics in every compost. However, the increase of microplastic particles’ concentrations with the diminution of the size could not be evaluated

sufficiently, as well as the permanence or degrading potential of certain plastic types.

Further work is needed to evaluate those aspects, especially for the degrading conditions of

plastics (conventional and compostable ones), and a regular monitoring should be established

to provide a broader view of the situation.