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Considering that pesticides have been used in Europe for over 70 years, a system for monitoring pesticide residues in EU soils and their effects on soil health is long overdue. In an attempt to address this problem, we tested 340 EU agricultural topsoil samples for multiple pesticide residues. These samples originated from 4 representative EU case study sites (CSS), which covered 3 countries and four of the main EU crops: vegetable and orange production in Spain (S-V and S-O, respectively), grape production in Portugal (P-G), and potato production in the Netherlands (N-P). Soil samples were collected between 2015 and 2018 after harvest or before the start of the growing season, depending on the CSS. Conventional and organic farming results were compared in S-V, S-O and N-P. Soils from conventional farms presented mostly mixtures of pesticide residues, with a maximum of 16 residues/sample. Soils from organic farms had significantly fewer residues, with a maximum of 5 residues/sample. The residues with the highest frequency of detection and the highest content in soil were herbicides: glyphosate and its main metabolite AMPA (P-G, N-P, S-O), and pendimethalin (S-V). Total residue content in soil reached values of 0.8 mg kg-1 for S-V, 2 mg kg-1 for S-O and N-P, and 12 mg kg-1 for P-G. Organic soils presented 70-90% lower residue concentrations than the corresponding conventional soils. There is a severe knowledge gap concerning the effects of the accumulated and complex mixtures of pesticide residues found in soil on soil biota and soil health. Safety benchmarks should be defined and introduced into (soil) legislation as soon as possible. Soil remediation techniques should be developed to keep the levels of pesticide residues below such benchmarks. Furthermore, the process of transitioning to organic farming should take into consideration the residue mixtures and their residence time in soil.

Pesticides are heavily used in agriculture to reduce crop losses due to pests, weeds and pathogens. The intensive and long-term use of pesticides raises major health and environmental concerns since a substantial part of applied pesticides does not reach the target and is distributed into the environment instead. Exposure data (i.e. data on occurrence and levels of different pesticide residues), a pre-requisite to perform comprehensive and cumulative pesticide risk assessments, are scarce and fragmented, especially for soil. As analysing all EU soils for pesticide residues is not realistic, the contamination status of EU soils has to be inferred. Given pesticide use data limitations, the representative uses of the active substances (a.s.) allowed in the EU market, which cover different application schemes and recommended application rates, can be used as a proxy to estimate the type and amount of pesticide residues in EU soils. These representative uses are also considered in the calculation of predicted environmental concentrations in soil (PECs), the closest to a soil quality indicator when it comes to residues in soils of currently used pesticides. Although both pesticide representative uses and PECs are publicly available, this information is presented for individual a.s., in respective EU dossiers, which up to now were never compiled into a database and explored as such. Therefore, our study provides the first predictions on the total pesticide content in EU soils, calculated for 8 different crops (i.e. cereals, maize, root crops, non-permanent industrial crops, permanent crops, grapes, dry pulses-vegetables-flowers, and temporary grassland), 3 EU regions (i.e. Northern, Central and Southern Europe), and 2 pesticide use scenarios (i.e. all pesticides applied and no herbicides used). Such predictions are integrated into the Soil Quality Mobile App SQAPP, a recently launched and freely available tool that integrates existing soil quality information (covering both soil properties and soil threats) and provides tailored recommendations to improve soil quality. Furthermore, we present soil quality thresholds for all these crop-region-use combinations in terms of the number of active substances and the total pesticide content expected in soil. Our results indicate a much higher variety of products allowed in cereals than in other crops, yet the highest pesticide load is expected in dry pulses-vegetables-flowers and in grapes. At the most heavy use scenario (i.e. all allowed substances are applied, at the same time, and at the worst recommended use patterns), pesticide input can exceed 1,200 kg a.s. ha-1 year-1 (dry pulses-vegetables-flowers). Pesticide input is expected to be the highest in Southern Europe, and the lowest in Northern Europe or Central Europe, depending on crop type. Predicted pesticide levels in soil were in line with application data, with the highest contents in dry pulses-vegetables-flowers, and in Southern Europe. Predictions-based thresholds resulted in very low soil protection, especially when compared to measured data in literature, and measurement-based thresholds. Finally, our results reinforce the need of monitoring and surveillance programs for pesticide residues in soil, proper risk evaluation procedures for mixtures, as well as the need to establish threshold methodologies for pesticides.

Viticulture, which plays a major role in the economy of several EU countries, is highly dependent of pesticides. In the São Lourenço experimental catchment, located in an important wine-growing region in Portugal, vineyards are the dominant land cover. Previous studies in this catchment showed the presence of different pesticide residues in surface water and erosion rates in vineyards of up to 30 Mg ha-1 y-1. However, information on the presence of pesticide residues in topsoils and water-eroded sediments are lacking, not just in this catchment but in general. To address these knowledge gaps, we conducted two soil sampling campaigns (fall 2015, fall 2016) and a field runoff-erosion experiment (winter 2015). We sampled 3 vineyards in the first campaign and 9 in the second, both covering different soil types (humic cambisols, calcic cambisols and chromic luvisols). Soil samples were collected within and between the vine rows, at the top, middle and bottom of the slope, and at two soil depths (0-2 and 15 cm). The runoff-erosion experiment involved 9 plots of ~12 m2; pesticide residues were monitored in topsoil and eroded sediments at six occasions after important rainfall events (>50 mm). 47 prioritized pesticide residues were analysed in 162 soil and 108 sediment samples. The levels of residues in soil were compared with their predicted environmental concentrations (PECs), calculated according to European Food Safety Authority (EFSA) pesticide application recommendations and to local farmers records. All soil samples contained pesticide residues, dimethomorph, glyphosate and its metabolite AMPA being the most frequent detected compounds. Measured levels of the different residues in soil occasionally exceeded predictions. Pesticide levels seemed related to slope position, generally being higher at the bottom than at the top or middle of the slopes, but not to the position within or between vine rows. Soil depth played a noticeable role in pesticide levels, with 80% lower concentrations of glyphosate and tebuconazole at 15 cm than 0-2 cm depth. For dieldrin (the only long-banned pesticide detected), the concentration was higher at 15 than 0-2 cm depth. Sediments had fewer compounds than soils, but the frequencies with which they were detected were similarly high. Pesticide levels were significantly higher in sediments than soils, especially in the case of the finest sediments (