Prevalence of microplastics in agricultural soils in southern Portugal

Microplastic contamination in soils is increasingly being recognised worldwide, yet Mediterranean agricultural systems remain poorly investigated. This work provides the first dataset of microplastic pollution in agricultural soils from Portugal, focusing on associations between polymer types and land-use history across four areas from a local farm with different agricultural practices. We collected 20 soil samples (five per zone). Each sample was processed in duplicate, yielding 40 analytical units. These were collected across four zones of a Cucurbitaceae farm in the Algarve region and analysed following conventional protocols to minimise cross-contamination. Concentrations ranged from 0 to 320 particles/kg, with a median of 80 particles/kg. Eight polymer types were identified, mainly polypropylene (PP, 31%), polyester (PES, 19%), and polyethylene (PE, 15%). Fibres were the most dominant (54%), followed by films and fragments, with the majority of particles ranging from 100 to 500 µm. White and transparent particles accounted for half of the observations. The polymer composition and particle morphologies differed across the four areas, consistent with their documented land-use histories and distinct levels of plastic use. These contrasts indicate that each zone exhibits a specific microplastic signature that reflects the intensity and type of agricultural practices applied over time. The study is limited by its farm-scale scope and the focus on surface soils (0–5 cm), yet it provides a robust baseline for future large-scale investigations in Mediterranean agricultural systems. While causal links cannot be firmly established, the results provide valuable insights into potential agricultural drivers of soil contamination in Mediterranean systems and highlight the need for improved plastic management in agriculture.