The main objective of this study was to learn the leachability of three widely used triazole fungicides (flutriafol, myclobutanil and triadimenol) in clay-loam soil to assess the risk of groundwater pollution by means of leaching potential indices (LPIs). For this, sorption, degradation and leaching experiments were conducted in a lab to evaluate the behaviour of the fungicides in a typical semiarid Mediterranean soil (calcareous Regosol). The sorption study was carried out following the batch equilibrium method. The degradation test was performed in aerobic and dark conditions (21 °C) for 60 days. Finally, the leaching potential was assessed using disturbed soil columns. Samples of soil and water were analysed by HPLC-MS². Low adsorption in the soil (log KOC ≤ 2.5) was observed for the three fungicides. The half-lives ranged from 79 to 136 days for triadimenol and flutriafol, respectively, showing moderate to high persistence in soil. All fungicides were detected in leachates with percentages ranging from 12% (triadimenol) to 26% (myclobutanil) of the initial mass added. Concentrations found in total leachates (13, 17 and 23 µg L⁻¹ for triadimenol, flutriafol and myclobutanil, respectively) were in all cases higher than the maximum admissible concentration (0.1 µg L⁻¹) established by the EU for groundwater. In accordance with the screening indices used (GUS, RLPI, LIX and ELI), all fungicides behave as mobile or very mobile compounds. The findings suggest that the studied fungicides are candidates to pollute groundwater resources, mainly in areas with intensive yearly rainfall regimes.

We have demonstrated the potential leaching of eight compounds, one insecticide (flonicamid) and seven fungicides (myclobutanil, penconazole, boscalid, difenoconazole, trifloxystrobin, pyraclostrobin and fenpyroximate) trough a typical Mediterranean soil (Calcaric regosol). The concentrations found in leaching water were in all cases above the limit set by the EU in groundwater (0.1 μg L⁻¹). For this, the efficiency of different homogeneous (photo-Fenton and photo-Fenton-like) and heterogeneous (ZnO and TiO₂) photocatalytic systems was tested in deionized water to choose the most appropriate treatment to remove pesticide residues from leaching water. The efficiency was in the order: ZnO + S₂O₈²⁻ (pH 7) > TiO₂+ S₂O₈²⁻ (pH 7) > ZnO (pH 7) > TiO₂ (pH 7) > Fe³⁺ (pH 3) > Fe³⁺ (pH 5) > Fe²⁺ (pH 3) > Fe²⁺ (pH 5). Thus, in the subsequent experiment we focus on the efficacy of solar heterogeneous photocatalysis (ZnO/Na₂S₂O₈ and TiO₂/ Na₂S₂O₈) on their removal from leaching water. A fast removal was observed for all pesticides at the end of the photoperiod, noticeably higher in the case of ZnO system, with the exception of flonicamid, a recalcitrant pesticide where the degradation rate only reached about 20% after 240 min of solar exposure. Although the mineralisation of the initial dissolved organic carbon was not complete due to the presence of interfering substances in the leaching water, the conversion rate under ZnO/Na₂S₂O₈ treatment was about 1.3 times higher than using TiO₂/Na₂S₂O₈.

Sulfonylurea herbicides are widely used for weed control in agriculture, and they are suspected to alter microbial communities and activities in the soil. This study investigates the impact of two sulfonylurea herbicides chlorsulfuron and sulfosulfuron on microbial community and activity in two different soils taken from two sites in west part of the Slovak Republic. The soil from the Malanta site was silt-loam luvisol with pH₍H₂O₎ 5.78 while the soil from the Stefanov site was sandy-loam regosol with pH₍H₂O₎ 8.25. These soils were not treated by sulfonylurea herbicides at least for 2 years prior to the study. In laboratory assay, the herbicides were applied to soil in their maximal recommended doses 26 and 25 g per hectare of chlorsulfuron and sulfosulfuron, respectively. Their effect was evaluated on the 3rd, 7th, 14th, 28th, 56th, and 112th day after application to soil. Illumina high-throughput amplicon sequencing of the 16S rRNA gene and ITS region was used to monitor changes on prokaryotic and fungal community composition. Enzymatic activity was evaluated using 11 substrates. Physiological profile of microbial community was analyzed using Biolog© ecoplates. Significant changes in enzymatic activity caused by the application of herbicides were found during the first 28 days. The application of herbicides altered the activity of cellobiohydrolase, arylsulphatase, dehydrogenase, phosphatase, and FDA hydrolase. Chlorsulfuron caused a more varying response of enzymatic activity than sulfosulfuron, and observed changes were not the same for both soils. In Malanta soil, chlorsulfuron decreased dehydrogenase activity while it was increased in the Stefanov soil. Phosphatase activity was decreased in both soils on 7th and 14th day. There were only minor changes in prokaryotic or fungal community or physiological profiles regarding pesticide application. Differences between soils and incubation time explained most of the variability in these parameters. Diversity indices, physiological parameters, and enzymatic activity decreased over time. The results have shown that chlorsulfuron and sulfosulfuron can affect the function and activity of the soil microbial community without significant change in its composition.