Browsing by Author "Silva, Vera"
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- Dynamics of pesticide residues in soils during the growing season: a case study in peach orchards, east-central PortugalPublication . Veloso, Abel; Silva, Vera; Osman, Rima; Simões, M.P.; Monteiro, M.C.H.; Violette GeissenPermanent crops rely heavily on pesticides. Their short-term behaviour has already been characterised under laboratory conditions. However, their degradation in the field is still poorly understood. Furthermore, studies that relate pesticide residues in soil with their application history are still scarce, despite their relevance for inferring the historical and diffuse dimensions of pollution. This work explores the spatial and temporal dynamics of pesticide residues in soil under the light of their application records and the accuracy of the predicted environmental concentrations (PEC). To achieve these purposes, 270 soil samples were collected at 5 sampling times over the 2022 growing season, in 18 peach orchards from east-central Portugal. Moreover, the data extracted from the application records was used to obtain predicted levels which were compared with the measured results. A total of 37 residues were analysed. Overall, 32 of these were detected back in, at least, one sample. Glyphosate and AMPA were the most frequently found and had the highest median concentrations. The comparison between predicted and measured environmental concentrations (MEC) suggests that pesticide decay was generally slower than expected. Glyphosate, AMPA, fluopyram and tebuconazole showed a high potential for resulting in background concentrations in soil. Our results highlight the need for regular and comprehensive monitoring, being recommended long-term assessments of the persistence and fate of pesticides under realistic conditions. Furthermore, our results also stress the necessity of more studies on reasons for PEC-MEC mismatch, a factor of concern considering the regulatory relevance of PEC values.
- Tracking the source of microplastics in soil : An exploratory case study in peach orchards from east‑central PortugalPublication . Veloso, Abel; Silva, Vera; Huerta Lwanga, Esperanza; Beriot, Nicolas; Monteiro, M.C.H.; Simões, M.P.; Geissen, VioletteIn the last 20 years, world plastic production has increased rapidly, reaching 4.00 × 1011 kg in 2022. However, less than 10% was recycled. Moreover, most conventional plastics are persistent and, therefore, remain in the environment long after their release. Although most studies on microplastic contamination focus on a single environmental compartment, an integrated and multicompartment approach is highly recommended considering the multitude of interactions between those compartments. This study addresses this knowledge gap, investigating the presence and potential sources of microplastics (MP) in agricultural soils under typical conditions of the Mediterranean region, characterised by dry summers and relatively moist and mild winters (Csa according to the Köppen-Geiger classification). For this, 19 orchards from east-central Portugal were used as case study sites, and a total of 111 samples were analysed. Soil content in MP was assessed in 3 soil layers (0–5, 5–15 and 15–25 cm). To quantify potential sources to soil, information from farmers was used, and samples from irrigation water, atmospheric deposition and manure were analysed. Optical assessment with the assistance of a stereomicroscope was used for MP quantification. The 0–5 cm soil layer showed a lower content (average of 2.2 particles·g−1) and higher particle sizes (average of 168 μm) than deeper soil layers. The identified sources contributed with 1.02 × 105 particles·m−2·year−1. Irrigation water was the main source, representing 55.9% of the aforemen-tioned input rate encountered for the 3 identified MP sources. Additional knowledge is needed regarding the possible variation in MP content throughout the year and between years and the polymer identification, not only in samples collected from soil but also from its main contamination sources. Furthermore, this study should be extended to other crops and regions as part of broader soil health monitoring.