Enhanced degradation of spiro-insecticides and their leacher enol derivatives in soil by solarization and biosolarization techniques

Abatement of pesticides residues in commercial farm soils by combined ozonation-solarization treatment

The widespread use of pesticides against agricultural pest and diseases introduces these pollutants and their transformation products into soils. The toxicity and permanence of these substances make it necessary for the development of remediation strategies in order to mitigate contamination and to further protect consumers. This work was aimed to evaluate the applicability of ozonation-solarization technology in the degradation of pesticide residues in commercial farm soils. The trial was conducted in two exploitations devoted during decades to tomato cultivation under greenhouse and net systems. Treatments were carried out using a pipping network (both superficial and sub-superficial) that delivered ozone in gaseous state after covering the soil with gas-tight plastic film to avoid ozone leaks to atmosphere. Control soil treatments, without ozone exposure, were also conducted. After 40 days of treatment, mean degradation percentages of about 55-61% for both cultivation systems were obtained, when the reduction of these pollutants in the control soils was about 8-15%. Ozonation-solarization impact was also assessed by changes on soil physical-chemical properties. Results suggest that ozonation in combination with solarization technique could be considered as a feasible approach for the remediation of pesticide-polluted farm soils.

Remediation of triazole, anilinopyrimidine, strobilurin and neonicotinoid pesticides in polluted soil using ozonation and solarization

This study aimed to investigate the effectiveness of ozonation and solarization techniques for the removal of different types of pesticides from soil during the summer season. The effect of two experimental parameters (temperature and ozone application mode) on the pesticide degradation was evaluated. The results showed that solarization (S), solarization with surface ozonation (SOS), and solarization with deep ozonation (SOD) enhanced pesticide degradation rates in comparison with the control (untreated soil, C). The triazole, anilinopyrimidine, strobilurin and neonicotinoid pesticides showed similar behaviour under S and SOS conditions. The highest decrease was found in SOD, indicating the significant effect of temperature and ozone application mode on the efficiency of the ozonation treatment. Thus, a higher soil temperature and a longer accumulated time at high temperature in treatments S, SOS and SOD were observed due to solarization process. In addition, the removal efficiency was enhanced with exposure time. Finally, the main 15 transformation products were identified during SOD treatment. The results suggest that solarization combined with ozonation techniques allows decontamination of soil containing pesticide residues.

Solar photocatalysis as strategy for on-site reclamation of agro-wastewater polluted with pesticide residues on farms using a modular facility

One of the consequences of phytosanitary treatments applied to crops is the generation of a great volume of agro-wastewater having pesticide residues. These pollutants can be considered a serious threat to the environment and human health due to their capacity to affect distant areas remaining for a long time after their application. We have assessed the degradation of five pesticides in agro-waste water produced in two farms by the cleaning pesticide containers and phytosanitary treatment equipment used in the farms. For this purpose, a pilot facility was installed in both farms and advanced oxidation treatments were conducted using natural sunlight by means of Na₂S₂O₈ and heterogeneous photocatalysis (TiO₂/Na₂S₂O₈). The remaining percentages obtained at the end of the experiments ranged from 5 to 90.1% for chlorantraniliprole, 5 to 82.3% for difenoconazole, 0.02 to 19.1% for metalaxyl, 1.4 to 74.4% for myclobutanil, and 0.3 to 61% for triadimenol. We observed a correlation between the higher remaining percentages and the total initial concentration of pollutant because of other commercial formulations applied in the farms. The results showed that this equipment could be used to eliminate or reduce the presence of pesticide residues in agro-waste water using an innovative facility installed in the farms and a renewable and economical source of energy (sunlight).

Combined ozonation and solarization for the removal of pesticides from soil: Effects on soil microbial communities

Pesticides have been used extensively in agriculture to control pests and soil-borne diseases. Most of these pesticides can persist in soil in harmful concentrations due to their intrinsic characteristics and their interactions with soil. Soil solarization has been demonstrated to enhance pesticide degradation under field conditions. Recently, ozonation has been suggested as a feasible method for reducing the pesticide load in agricultural fields. However, the effects of ozonation in the soil microbial community have not been studied so far. Here, we evaluate the combined effects of solarization and ozonation on the microbial community of a Mediterranean soil. For this purpose, soil physico-chemical characteristics and enzyme activities and the biomass (through analysis of microbial fatty acids) and diversity (through 16S rRNA and ITS amplicon sequencing) of soil microbial communities were analyzed in a 50-day greenhouse experiment. The degradation of the pesticides was increased by 20%, 28%, and 33% in solarized soil (S), solarized soil with surface ozonation (SOS), and solarized soil with deep ozonation (SOD), respectively, in comparison to control (untreated) soil. Solarization and its combination with ozonation (SOS and SOD) increased the ammonium content as well as the electrical conductivity, while enzyme activities and soil microbial biomass were negatively affected. Despite the biocidal character of ozone, several microbial populations with demonstrated pesticide-degradation capacity showed increases in their relative abundance. Overall, the combination of solarization plus ozone did not exacerbate the effects of solarization on the soil chemistry and microbial communities, but did improve pesticide degradation.

The lipid metabolism alteration of three spirocyclic tetramic acids on zebrafish (Danio rerio) embryos

Spirocyclic tetramic acids are widely used in controlling phytophagous mite species throughout the world. the data set is incomplete and provides insufficient evidence for drawing the same conclusion for fish. To fill the gap whether these acaricides alter lipid metabolism on vertebrates, zebrafish embryos exposed to a series concentration of pesticides, the developmental effects, enzyme activities and levels of gene expression were assessed, battery of biomarker utilized by the integrated biomarker response (IBRv2) model. The 96 h-LC₅₀ of spirodiclofen, spiromesifen and spirotetramat were 0.14, 0.12 and 5.94 mg/L, respectively. Yolk sac deformity, pericardial edema, spinal curvature and tail malformation were observed. Three spirocyclic acids were unfavouring the lipid accumulation of by inhibited the acetyl-CoA carboxylase (ACC), fatty acid synthesis (FAS), fatty acid binding proteins (FABP2) and lipoprotein lipase (LPL) activity. The total cholesterol (TCHO) level significantly decreased in the 0.072 mg/L spirodiclofen group and 0.015 and 0.030 mg/L in the spiromesifen groups. No expected change in spirotetramat group on the TCHO and triglycerides (TGs) levels for any of the treatments. The mRNA levels of the genes related to lipid metabolism also significantly altered. In both spirodiclofen and spiromesifen, ACC achieved the highest scores among a battery of biomarkers using integrated biomarker response (IBRv2). The results suggest that spiromesifen was the most toxic for embryos development and spirodiclofen was the most toxic for lipid metabolism in embryos. The 0.07 mg/L of spirodiclofen, 0.05 mg/L of spiromesifen and 2.00 mg/L would cause malformation on zebrafish embryos. This study will provide new insight that fatty acid metabolism may be a suitable biomarker for the spirocyclic tetramic acids in fish species.