Field-scale dissipation of tebuconazole in a vineyard soil amended with spent mushroom substrate and its potential environmental impact

The Behavior of Terbuthylazine, Tebuconazole, and Alachlor during Denitrification Process

Pesticide compounds can influence denitrification processes in groundwater in many ways. This study observed behavior of three selected pesticides under denitrifying conditions. Alachlor, terbuthylazine, and tebuconazole, in a concentration of 0.1 mL L-1, were examined using two laboratory denitrifications assays: a "short" 7-day and a "long" 28-day test. During these tests, removal of pesticides via adsorption and biotic decomposition, as well as the efficiency of nitrate removal in the presence of the pesticides, were measured. No considerable inhibition of the denitrification process was observed for any of the pesticides. On the contrary, significant stimulation was observed after 21 days for alachlor (49%) and after seven days for terbuthylazine (40%) and tebuconazole (36%). Adsorption was in progress only during the first seven days in the case of all tested pesticides and increased only negligibly afterwards. Immediate adsorption of terbuthylazine was probably influenced by the mercuric chloride inhibitor. A biotic loss of 4% was measured only in the case of alachlor.

Changes in vineyard soil parameters after repeated application of organic-inorganic amendments based on spent mushroom substrate

The changes of physicochemical and biochemical parameters of a silty loam (S1) and sandy loam (S2) vineyard soils added with spent mushroom substrate (SMS) or SMS composted with ophite (OF) as rock dust (SMS + OF) were studied. Two doses of SMS or SMS + OF (25 and 100 Mg ha^-1) were applied for two consecutive years (2020-2021) and changes of soil physicochemical parameters, and dehydrogenase activity (DHA), respiration (RES), microbial biomass (BIO), and the phospholipid fatty acids (PLFAs) profile were assayed on a temporal basis. The results showed an increase in soil organic carbon (OC) content, total and mineralised N, P, and K, especially when the highest SMS dose was applied to soils. Repeated application caused OC content over time up to 2.3 times higher than initial content in the silty loam soil. This increase was not observed in sandy soil, possibly due to a higher bioavailability of OC, as indicated by the evolution of extractable humic acid/fulvic acid pools. In both soils, all biochemical parameters increased after amendment, being favoured both by the OC and by the presence of OF. Significant positive correlations were found between DHA, RES and BIO, and OC content especially in the first part and then levelled off after the second dose application. Total bacterial or fungal PLFAs patterns reflected the variation of BIO by SMS application. The higher growth of fungi vs. bacterial community in amended soils was recorded after the first SMS application, although the opposite effect occurred after the second application, with similar results in both soils. The findings indicate that the application of SMS or SMS + OF in vineyard soils could be an appropriate agronomic management practice for maintaining soil sustainability, although doses and application times of these amendments should first be evaluated depending on soil texture.

Using bibliometrics to analyze the state of art of pesticide use in vineyard agrosystems: a review

The production of wine dates to ancient civilization and has heavily influenced different landscapes around the globe. Nowadays, wine is still an important sector in terms of land use and income source in many countries, more specifically in the European Mediterranean region. However, to control pests and regulate wine growth, the extensive use of pesticides is common. The effects and persistence of agrochemicals in the environment is well known and defined in scientific literature as well as the environmental and human health risks of these compounds. The purpose of this review was to do a state of art of worldwide production of academic literature using bibliometric principles and analysis to identify thematic areas of this type of agriculture, and its challenges in a changing world. For this review, the focus is on current practices to see what may evolve for more sustainable viticulture. It was found that the three main producers of wine, i.e., Spain, France, and Italy, are also three top producers of scientific literature on this topic. The use of bibliometric methodologies defined the main thematic areas on this subject as follows: soil-plant transfer of agrochemicals, heavy metal accumulation in vineyard soils, management practices in viticulture, water pollution transport, effects of viticulture on the living part of soil, sustainable alternatives to pesticides. We found that Spain, France, and Italy work the most on developing sustainable alternatives for agricultural practices; however, sustainable alternatives and practices were also the least developed thematic in general.

Assessment of the eco-toxicological effects in zoxamide polluted soil amended with fertilizers-An indoor evaluation

Zoxamide is a benzamide fungicide applied to control diseases caused by oomycete fungi. Fertilizers are important agricultural supplies to adjust soil properties and increase nutrition. To investigate the impact of zoxamide and seven fertilizers urea, phosphate fertilizer, potash fertilizer, compound fertilizer, organic fertilizer, vermicompost and soya bean cakes on the soil environment, the enantioselective dissipation characteristics of zoxamide, soil enzyme activities, pH and N, P nutrition changes were comprehensively analyzed in our present study. The enantioseparation method was successfully validated to quantify the zoxamide enantiomers in soil by HPLC using Chiral NQ (2)-RH column. Our results demonstrated that the R-(-)- and S-(+)-zoxamide half dissipated in the range of 10.88-17.81 and 8.05-14.41 days, respectively. S-(+)-zoxamide disappeared faster in soil. The vermicompost accelerated the dissipation rate of S-(+)-zoxamide, while urea, phosphate, organic and vermicompost fertilizer increased the dissipation selectivity. Zoxamide and fertilizers other than urea caused soil acidification during 80 days. Zoxamide was beneficial to soil catalase, instead inhibited soil urease, dehydrogenase activities and available phosphorus content. No significant effects on sucrase activity and available nitrogen content were found by zoxamide. Vermicompost and soya bean cakes had lasting and outstanding performance in efficiently improving soil enzyme activity and N, P nutrition. The comprehensive understanding of the ecological impact induced by chiral pesticide enantiomers and fertilizers on soil is vital to ensure the sustainable development and safety of agricultural production.

Using biobeds for the treatment of fungicide-contaminated effluents from various agro-food processing industries: Microbiome responses and mobile genetic element dynamics

Agro-food processing industries generate large amounts of pesticide-contaminated effluents that pose a significant environmental threat if managed improperly. Biopurification systems like biobeds could be utilized for the depuration of these effluents although direct evidence for their efficiency are still lacking. We employed a column leaching experiment with pilot biobeds to (i) assess the depuration potential of biobeds against fungicide-contaminated effluents from seed-producing (carboxin, metalaxyl-M, fluxapyroxad), bulb-handling (thiabendazole, fludioxonil and chlorothalonil) and fruit-packaging (fludioxonil, imazalil) industries, (ii) to monitor microbial succession via amplicon sequencing and (iii) to determine the presence and dynamics of mobile genetic elements like intl1, IS1071, IncP-1 and IncP-1ε often associated with the transposition of pesticide-degrading genes. Biobeds could effectively retain (adsorbed but extractable with organic solvents) and dissipate (degraded and/or not extractable with organic solvents) the fungicides that were contained in the agro-industrial effluents with 93.1-99.98% removal efficiency in all cases. Lipophilic substances like fluxapyroxad were mostly retained in the biobed while more polar substances like metalaxyl-M and carboxin were mostly dissipated or showed higher leaching potential like metalaxyl-M. Biobeds supported a bacterial and fungal community that was not affected by fungicide application but showed clear temporal patterns in the different biobed horizons. This was most probably driven by the establishment of microaerophilic conditions upon water saturation of biobeds, as supported by the significant increase in the abundance of facultative or strict anaerobes like Chloroflexi/Anaerolinae, Acidibacter and Myxococcota. Wastewater application did not affect the dynamics of mobile genetic elements in biobeds whose abundance (intl1, IS1071, IncP-1ε) showed significant increases with time. Our findings suggest that biobeds could effectively decontaminate fungicide-contaminated effluents produced by agro-food industries and support a rather resilient microbial community.

Organic Amendment for the Recovery of Vineyard Soils: Effects of a Single Application on Soil Properties over Two Years

Spent mushroom substrate (SMS) is the organic residue generated during mushroom cultivation, and it is being produced in ever-greater quantities around the world. Different applications for this residue have been proposed for its valorization, but its application as a soil amendment could be one of the most sustainable. SMS improves soil quality by increasing its organic matter (OM), thereby enhancing the sustainability of agricultural systems. The objective of this work was to evaluate the effect of the application of two doses of SMS on the chemical, biochemical, and microbiological characteristics of two degraded vineyard soils in La Rioja (Spain) with different textures, as a new regenerative agricultural practice. The variations in organic carbon (OC), micro- and macronutrients, soil microbial biomass (BIO), respiration (RES), dehydrogenase activity (DHA), and the profile of phospholipid fatty acids (PLFAs) extracted from the soils were evaluated over two years. An initial increase in soil OC content was recorded in both soils, although the content that remained over time differed for each site. In general, SMS enhanced DHA, RES, and BIO in the soils, but the effect varied, possibly being conditioned by the availability of OC for soil microorganisms. In general, changes in the soils’ microbial structure after SMS application were not very significant over the two-year experimental period.

Seasonal variations in air concentrations of 27 organochlorine pesticides (OCPs) and 25 current-use pesticides (CUPs) across three agricultural areas of South Africa

For decades pesticides have been used in agriculture, however, the occurrence of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) is poorly understood in Africa. This study investigates air concentrations of OCPs and CUPs in three South African agricultural areas, their spatial/seasonal variations and mixture profiles. Between 2017 and 2018, 54 polyurethane foam-disks passive air-samplers (PUF-PAS) were positioned in three agricultural areas of the Western Cape, producing mainly apples, table grapes and wheat. Within areas, 25 CUPs were measured at two sites (farm and village), and 27 OCPs at one site (farm). Kruskal-Wallis tests investigated area differences in OCPs concentrations, and linear mixed-effect models studied differences in CUPs concentrations between areas, sites and sampling rounds. In total, 20 OCPs and 16 CUPs were detected. A median of 16 OCPs and 10 CUPs were detected per sample, making a total of 11 OCPs and 24 CUPs combinations. Eight OCPs (trans-chlordane, o,p'-/p,p'-dichlorodiphenyldichloroethylene (DDE)/dichlorodiphenyltrichloroethane (DDT), endosulfan sulfate, γ-hexachlorocyclohexane and mirex) and two CUPs (carbaryl and chlorpyrifos) were quantified in all samples. p,p'-DDE (median 0.14 ng/m³) and chlorpyrifos (median 0.70 ng/m³) showed the highest concentrations throughout the study. Several OCPs and CUPs showed different concentrations between areas and seasons, although CUPs concentrations did not differ between sites. OCPs ratios suggest ongoing chlordane use in the region, while DDT and endosulfan contamination result from past-use. Our study revealed spatial and seasonal variations of different OCPs and CUPs combinations detected in air. Further studies are needed to investigate the potential cumulative or synergistic risks of the detected pesticides.

Rapid In Situ Biomonitoring of Subsoil Contamination by Applying an Algae-Soaked Disc Seeding Assay

Various pollutants are pervasive in soil environments due to human activities, thereby damaging soil ecosystems. In this study, extension of a previously developed algae-soaked disc seeding assay for periodic evaluation of subsoil contamination over time was described. The assay can be used in different contamination configurations of silver nanoparticles in combination with examination of cell morphology, esterase activity, oxidative stress, and membrane permeability. In addition, we periodically attempted to repeat the algae-soaked disc seeding assay every three weeks. We evaluated applicability of this algae-soaked disc seeding assay using alga Chlamydomonas reinhardtii exposed to heterogeneous silver nanoparticle-contaminated soils. The results demonstrated that this assay is applicable for monitoring a change of subsoil contamination by periodic evaluation over time. The developed assay was identified as a periodically rapid in situ biomonitoring technique to measure subsoil contamination over time.

Assessment of pesticide inputs into surface waters by agricultural and urban sources - A case study in the Querne/Weida catchment, central Germany

Pesticide inputs into surface waters may cause harmful effects on aquatic life communities and substantially contribute to environmental pollution. The present study aimed at evaluating the input pathways in the Querne/Weida catchment (central Germany) to efficiently target mitigation measures of pesticide losses. Relevant pesticide substances were measured in surface waters in agricultural and urban surroundings and in soil samples within the catchment area. Pesticides application data from farmers were analyzed. Additionally, batch tests were performed to determine sorption and degradation of relevant pesticides for site specific soil properties. Frequency of detection, number of pesticides and maximum concentrations were much higher in the surface water samples in mainly urban surroundings compared to those in agricultural surrounding. The most frequently detected substances were glyphosate, AMPA, diflufenican and tebuconazole in surface water samples and diflufenican, boscalid, tebuconazole and epoxiconazole in the topsoil samples. Glyphosate and AMPA contributed to the highest concentrations in surface water samples (max. 58 μg L^-1) and soil samples (max. 0.19 mg kg^-1). In most cases, pesticide detections in surface water and soil were not consistent with application data from farmers, indicating that urban sources may affect water quality in the catchment area substantially. However, it was observed that pesticide substances remain in the soil over a long time supported by sorption on the soil matrix. Therefore, delayed inputs into surface waters could be suspected. For the implementation of reduction measures, both urban and agricultural sources should be considered. Novel findings of the study: pesticide detections were not consistent with application data from farmers, urban sources contributed substantially to pesticide pollution of surface waters.

Biochemical and Histopathological Alterations in Different Tissues of Rats Due to Repeated Oral Dose Toxicity of Cymoxanil

Simple Summary

Cymoxanil is a broad-spectrum fungicide used to protect many fruits, vegetables, and field crops against several fungal diseases. Investigating the potential hazards and toxicological effects of this fungicide is very important as cymoxanil can be a major human health concern. The present study investigated the effect of repeated oral doses of cymoxanil on different tissues of treated rats by measuring different biochemical parameters and investigating the histopathological changes. Interestingly, our study reported a dose-dependent effect of cymoxanil that was combined with marked alteration on biochemical enzymes. Moreover, the alteration was combined with marked histopathological changes in various tissues of treated rats, mainly liver, brain, and kidney tissues. Our study collectively reveals that cymoxanil can be a source of major concern for human health with respect to long-term and low dose exposure.

Abstract

Evaluating potential adverse health impacts caused by pesticides is an important parameter in human toxicity. This study focuses on the importance of subchronic toxicity assessment of cymoxanil fungicide in rats with special reference to target biochemical enzymes and histopathological changes in different tissues. In this regard, a 21-day toxicity study with repeated cymoxanil oral doses was conducted. It has been shown that low doses (0.5 mg/kg) were less effective than medium (1 mg/kg) and high (2 mg/kg) doses. Moreover, high dose dose-treated rats showed piecemeal necrosis in the liver, interstitial nephritis and tubular degeneration in the kidneys, interstitial pneumonia and type II pneumocyte hyperplasia in the lungs, gliosis, spongiosis, and malacia in the brain, and testicular edema and degeneration in the testes. Cymoxanil significantly increased AST, ALT, and ALP in serum and liver, indicating tissue necrosis and possible leakage of these enzymes into the bloodstream. Creatinine levels increased, indicating renal damage. Similarly, significant inhibition was recorded in brain acetylcholinesterase, indicating that both synaptic transmission and nerve conduction were affected. Importantly, these histopathological and biochemical alterations were dose-dependent. Taken together, our study reported interesting biochemical and histopathological alterations in different rat tissues following repeated toxicity with oral doses of cymoxanil. Our study suggests future studies on different pesticides at different concentrations that would help urge governments to create more restrictive regulations concerning these compounds’ levels.

Bacterial compatibility and immobilization with biochar improved tebuconazole degradation, soil microbiome composition and functioning

Tebuconazole is a widely used fungicide that may impair soil health. Presently, limited information is available on the bioremediation of tebuconazole-contaminated soil using biochar as a carrier for bacteria. In this study, we firstly isolated a tebuconazole-degrading strain and identified it as Alcaligenes faecalis WZ-2. Then, we used wheat straw-derived biochar as carrier to capture strain WZ-2 to assemble microorganism-immobilized composite. Finally, we investigated the effects of strain WZ-2 and biochar-immobilized WZ-2 on tebuconazole biodegradation, microbial enzyme activities and community composition in the contaminated soil. Results showed that, as compared to control, the strain WZ-2 and biochar-immobilized WZ-2 accelerated the degradation of tebuconazole, while reducing the half-life of tebuconazole from 40.8 to 18.7 and 13.3 days in soil, respectively. However, biochar alone than control slightly retarded the degradation of tebuconazole in soil. Though tebuconazole (10 mg/kg) negatively affected the soil enzyme activities (urease, dehydrogenase, and invertase) and microbiome community structure, the biochar-immobilized WZ-2 not only accelerated the degradation of tebuconazole but also restored native soil microbial enzyme activities and microbiome community composition. Our results suggest that a compatible combination of bacteria with biochar is an attractive and efficient approach for remediation of pesticide-contaminated soil and improvement of soil biological health.

Triazole resistance in Aspergillus fumigatus in crop plant soil after tebuconazole applications

Aspergillus fumigatus is the primary agent of invasive aspergillosis (IA) causing high morbidity and mortality in immunocompromised patients. Triazole resistance in A. fumigatus and its sources have gained wide attention. For several years, environmental fungicides use has been proposed as the major cause for triazole resistance in A. fumigatus. However, there are few studies on azole-resistant A. fumigatus (ARAF) selected by triazole fungicides in agricultural systems. We studied the possible emergence of ARAF in the field after exposure to triazole fungicide tebuconazole. Our results showed that exposure to tebuconazole in soil selects for resistance to triazoles in A. fumigatus. The probability of ARAF developing in soils depends upon the concentrations of tebuconazole after application. We suggest that tebuconazole applications should be minimized to reduce selective pressure for the generation of ARAFs.

Multiple Screening of Pesticides Toxicity in Zebrafish and Daphnia Based on Locomotor Activity Alterations

Pesticides are widely used to eradicate insects, weed species, and fungi in agriculture. The half-lives of some pesticides are relatively long and may have the dire potential to induce adverse effects when released into the soil, terrestrial and aquatic systems. To assess the potential adverse effects of pesticide pollution in the aquatic environment, zebrafish (Danio rerio) and Daphnia magna are two excellent animal models because of their transparent bodies, relatively short development processes, and well-established genetic information. Moreover, they are also suitable for performing high-throughput toxicity assays. In this study, we used both zebrafish larvae and water flea daphnia neonates as a model system to explore and compare the potential toxicity by monitoring locomotor activity. Tested animals were exposed to 12 various types of pesticides (three fungicides and 9 insecticides) for 24 h and their corresponding locomotor activities, in terms of distance traveled, burst movement, and rotation were quantified. By adapting principal component analysis (PCA) and hierarchical clustering analysis, we were able to minimize data complexity and compare pesticide toxicity based on locomotor activity for zebrafish and daphnia. Results showed distinct locomotor activity alteration patterns between zebrafish and daphnia towards pesticide exposure. The majority of pesticides tested in this study induced locomotor hypo-activity in daphnia neonates but triggered locomotor hyper-activity in zebrafish larvae. According to our PCA and clustering results, the toxicity for 12 pesticides was grouped into two major groups based on all locomotor activity endpoints collected from both zebrafish and daphnia. In conclusion, all pesticides resulted in swimming alterations in both animal models by either producing hypo-activity, hyperactivity, or other changes in swimming patterns. In addition, zebrafish and daphnia displayed distinct sensitivity and response against different pesticides, and the combinational analysis approach by using a phenomic approach to combine data collected from zebrafish and daphnia provided better resolution for toxicological assessment.

Modelling herbicides mobility in amended soils: Calibration and test of PRZM and MACRO

Addition of organic residues to soil is a current farming practice but it is not considered in the modelling studies for pesticide risk assessment at regulatory level despite its potential impact on the pesticide dynamics in soil. Thus, the objective of this work was to examine and to compare the ability of PRZM and MACRO pesticide fate models to simulate soil water content, and bromide (Br^-, tracer), chlorotoluron and flufenacet concentrations in the soil profiles (0-100 cm) of one agricultural soil, unamended (control soil, S), amended with spent mushroom substrate (S + SMS) or amended with green compost (S + GC). Based on a two-year field-scale dataset, the models were first calibrated against measurements of water and solutes contents in the soil profiles (first year) and then tested without any further model calibration by comparison with the field observations of the second year. In general, the performance of MACRO to simulate the whole dataset in the three soil treatments was higher than that of PRZM. MACRO simulated satisfactorily the water dynamics along the soil profiles whereas it was poorly described by the capacity model PRZM. Both models predicted very well the Br^- mobility in control and amended soils after dispersion parameters were fitted to observations. No calibration was necessary to reproduce correctly herbicides vertical distribution in the control soil profile. In the amended soils, MACRO simulations were highly correlated to the observed vertical distribution of flufenacet and chlorotoluron, but calibration of the K_d of chlorotoluron was needed. On the contrary, modelling with PRZM required calibration of K_d and DT₅₀ of both herbicides to obtain an acceptable agreement between observations and predictions in the amended soils. K_d and DT₅₀ calibration was based on the initial dissolved organic carbon contents (DOC) of amended soils. It allowed to take into account the processes that decrease the herbicides sorption on the soil and enhance their bioavailability, but that are not described in PRZM and MACRO (such as the formation of herbicide-DOC mobile complexes). This work showed that models such as PRZM and MACRO are able to simulate the fate of pesticides in amended soils. However, before using these models as predictive tools in large amended soil conditions, and especially in the regulatory context, further modelling studies should focus on other pedoclimatic-pesticides-organic residues combinations, and on longer periods.

Pesticide application inhibit the microbial carbonic anhydrase-mediated carbon sequestration in a soil microcosm

Heterotrophic system for carbon sequestration is gaining importance in the recent decades. Carbonic anhydrase (CA) is a major enzyme involved in carbon sequestration and biomineralization process. In this paper, we evaluate the effect of pesticide on CA activity using inhibitory assay. 2,4-D, being one of the most extensively used pesticide, being deleterious to soil health, its usage should be minimized to regain the soil health. Maximum inhibitory constant (K_i) was observed for 5% 2,4-D (49.53 mM) followed by 5% glyphosate (43.92 mM). The maximum Km increase with increase in pesticide concentration by 3.05-fold was in case of glyphosate which was higher than that of 2,4-D (2.08-fold) and dichlorvos (2.38-fold). Moreover, we evaluated the carbon sequestration using CA enzyme in the soil microcosm. In the present study, we identified the negative impact of 2,4-D on carbonic anhydrase produced by Bacillus halodurans PO15. The inhibition was a mixed type and had significantly lowered the carbon reduction to about 2.38 ± 0.17% in a soil microcosm study. Based on the molecular docking, the inhibition was contributed due to weak H-bonding interaction with amino acid residues (Gly65, Gly95, Val147, Ser150 and Gly65, Ser146, and Ser150).

Microbiological and biochemical properties of soil polluted with a mixture of spiroxamine, tebuconazole, and triadimenol under the cultivation of Triticum aestivum L

Pesticide contamination is one of the most serious threats for agricultural soils. Excessive pesticide levels in soil can exert negative effects on soil-dwelling organisms by decreasing their bioavailability and, consequently, lowering soil quality. This study aimed to evaluate the effect of a mixture of spiroxamine, tebuconazole, and triadimenol (S + Te + Tr) on the biological activity of soil determined based on the proliferation of microorganisms and their diversity, enzymatic activity of soil, and resistance of Triticum aestivum L. A pot experiment was performed on sandy loam (pH 7.0) treated with four doses of the tested active ingredients: 0.000, 0.092, 2.76, 13.80, and 27.60 mg kg^-1. Soil without the fungicide served as the control sample. The tested fungicide induced changes in the biological activity of soil. When administered to the soil in the highest dose (27.60 mg kg^-1 DM of soil), it inhibited its biological activity. It significantly inhibited the proliferation of organotrophs, actinomycetes, and fungi, but still the most susceptible to its effects turned out to be fungi. Fungicide dose of 27.60 mg kg^-1 decreased counts of organotrophic bacteria, actinomycetes, and fungi by on average 0.009 log, 0.100 log, and 0.282 log, respectively, compared to the control sample. Administration of the S + Te + Tr mixture to soil decreased also values of colony development index (CD) determined for all tested groups of microorganisms. Values of the ecophysiological diversity index (EP) decreased in the case of organotrophs and actimomycetes and increased in the case of fungi. The S + Te + Tr mixture inhibited activities of dehydrogenases, urease, and acid phosphatase. Significant changes were also reported in the growth of spring wheat. The resistance index (RS) calculated based on plant yield demonstrated spring wheat to be very susceptible to the tested preparation administered to soil in doses of 13.80 and 27.60 mg kg^-1.

Adsorption Thermodynamics and Dynamics of Three Typical Dyes onto Bio-adsorbent Spent Substrate of Pleurotus eryngii

Dyeing wastewater is very hard to treat, and adsorption could be a good choice. Spent substrate of Pleurotus eryngii (SSPE) was first used to adsorb malachite green, safranine T and methylene blue from aqueous solutions, and the corresponding adsorption isotherm, thermodynamics and dynamics models were simulated. More than 93% of the dyes were removed with solutions with 100 mg/L of initial dye concentration, 1 g of SSPE and pH of 6.0 after adsorption for 4 h. Freundlich isotherm models fit better the adsorption data than Langmuir models. Adsorption of the dyes onto SSPE was a spontaneous exothermic process based on an adsorption thermodynamics model. SSPE could adsorb the dyes rapidly, and a second-order kinetics model fit better with the adsorption data than a pseudo first-order kinetics model. Accordingly, SSPE could be a good bio-adsorbent for the removal of malachite green, safranine T and methylene blue from the aqueous solution.

Recycling organic residues in soils as amendments: Effect on the mobility of two herbicides under different management practices

The addition of organic residues to soil to increase its organic matter content is considered as a viable option for sustainable food production in soils sensitive to degradation and erosion. However, the recycling of these organic residues in agricultural soils needs to be previously appraised because they can modify the behaviour of pesticides when they are simultaneously applied in agricultural practices. This study evaluated the changes in the mobility and persistence of two herbicides, triasulfuron and prosulfocarb, after two repeated applications in field experimental plots in an unamended soil and one amended with green compost (GC) for seven months. Different factors were studied: i) soil without amendment (S), ii) soil amended with two doses of GC (∼12 t C ha^-1, S + GC1 and 40 t C ha^-1, S + GC2), and iii) soils unamended and amended with different irrigation conditions: non-irrigated and with additional irrigation (2.8 mm per week). After the first application of herbicides, the results initially indicated no significant effects of soil treatments or irrigation conditions for triasulfuron mobility in agreement with the residual concentrations in the soil profile. The effect of irrigation was noted after one month of herbicide application and the effect of the soil treatment was significant after two months because the persistence of triasulfuron in S + GC2 was maintained until 50% of the applied amount. For prosulfocarb, the influence of soil amendment was significant for the initial persistence of the herbicide in S + GC2, higher than in S or S + GC1, in agreement with its adsorption constants for this soil. However, dissipation or leaching of the herbicide over time was not inhibited in this soil. After the repeated application of herbicides, the influence of the treatment of soils and/or irrigation was significant for the leaching and dissipation of both herbicides. The initial dissipation/degradation or leaching of herbicides was higher than after the first application, although persistence was maintained after five months of application in amended soils for triasulfuron and in unamended and amended soils for prosulfocarb. The results confirm that high doses of GC increased the persistence of both herbicides. This practice may offer the possibility of applying a tailored dose of GC to soil for striking a balance between residual concentrations and the soil agronomic effect.

The dissipation and microbial ecotoxicity of tebuconazole and its transformation products in soil under standard laboratory and simulated winter conditions

Tebuconazole (TBZ) is a widely used triazole fungicide at EU level on cereals and vines. It is relatively persistent in soil where it is transformed to various transformation products (TPs) which might be environmentally relevant. We assessed the dissipation of TBZ in soil under contrasting incubation conditions (standard vs winter simulated) that are relevant to its application scheme, determined its transformation pathway using advanced analytical tools and ¹⁴C-labeled TBZ and assessed its soil microbial toxicity. Mineralization of ¹⁴C-triazole-ring-labeled TBZ was negligible but up to 11% of ¹⁴C-penyl-ring-labeled TBZ evolved as ¹⁴CO₂ within 150 days of incubation. TBZ persistence increased at higher dose rates (×10 compared to the recommended agronomical dose ×1) and under winter simulated conditions compared to standard incubation conditions (at ×1 dose rate DT₅₀ of 202 and 88 days, respectively). Non-target suspect screening enabled the detection of 22 TPs of TBZ, among which 17 were unknown. Mass spectrometry analysis led to the identification of 1-(4-chlorophenyl) ethanone, a novel TP of TBZ, the formation of which and decay in soil was determined by gas chromatography mass spectrometry. Three hypothetical transformation pathways of TBZ, all converging to 1H-1,2,4-triazole are proposed based on suspect screening. The ecotoxicological effect of TBZ and of its TPs was assessed by measuring by qPCR the abundance of the total bacteria and the relative abundance of 11 prokaryotic taxa and 4 functional groups. A transient impact of TBZ on the relative abundance of all prokaryotic taxa (except α-proteobacteria and Bacteroidetes) and one functional microbial group (pcaH-carrying microorganisms) was observed. However the direction of the effect (positive or negative) varied, and in certain cases, depended on the incubation conditions. Proteobacteria was the most responsive phylum to TBZ with recovery observed 20 days after treatment. The ecotoxicological effects on the soil microorganisms were not correlated with 1-(4-chlorophenyl) ethanone.

Acute and chronic toxicity of pesticides on tadpoles of Physalaemus cuvieri (Anura, Leptodactylidae)

Brazil is the largest consumer of pesticides in the world. However, knowledge on how these pesticides affect wildlife is scarce. Among the vertebrates, amphibians are particularly important in research to assess the impact of pesticides because of the correlation between pesticide and the decline of these species. This study aimed to evaluate the acute and chronic toxicity of commercial formulations of pesticides, i.e., atrazine (herbicide), cypermethrin (insecticide), and tebuconazole (fungicide) in Physalaemus cuvieri tadpoles. Eggs were collected in nature and cultivated under controlled conditions in the laboratory. Toxicity tests were carried out under standard conditions to determine the lethal concentration (LC₅₀) after 96 h of exposure and to determine the effect of sublethal concentrations after 7 days. In addition, we performed swimming activity tests on tadpoles exposed to sublethal concentrations. The lethal concentration (LC₅₀) was 19.69 mg/L for atrazine, 0.24 mg/L for cypermethrin and 0.98 mg/L for tebuconazole. In the acute test, atrazine showed lower toxicity than cypermethrin and tebuconazole for P. cuvieri. Swimming activity was affected at sublethal doses of atrazine and cypermethrin, but was not after exposure to tebuconazole. Cypermethrin was the insecticide that most altered the swimming activity of the individuals tested. The risk evaluation analysis indicated risks for tadpoles exposed to three tested pesticides, specially cypermethrin.

Application of green compost as amendment in an agricultural soil: Effect on the behaviour of triasulfuron and prosulfocarb under field conditions

Herbicides are essential in agricultural systems for maintaining crop yields, as weeds compromise grain production. Furthermore, the application of organic amendments to soil is an increasingly frequent agricultural practice for avoiding irreversible soil degradation. However, this practice could modify the behaviour of the herbicides applied, with implications for their absorption by weeds. This study evaluated the dissipation, persistence and mobility of the herbicides triasulfuron and prosulfocarb in a sandy clay loam soil unamended and amended with green compost (GC) in a field experiment using single or combined commercial formulations of both herbicides. The study was carried out in experimental plots (eight treatments × three replicates) corresponding to unamended soil and soil amended with GC, untreated and treated with the herbicide formulations Logran^®, Auros^® and Auros Plus^® over 100 days. The half-life (DT₅₀) of triasulfuron applied individually was 19.4 days, and increased in the GC-amended soil (46.7 days) due to its higher adsorption by this soil, although non-significant differences between DT₅₀ values were found when it was applied in combination with prosulfocarb. Prosulfocarb dissipated faster than triasulfuron under all the conditions assayed, but non-significant differences were observed for the different treatments. The analysis of the herbicides at different soil depths (0-50 cm) after their application confirmed the leaching of both herbicides to deeper soil layers under all conditions, although larger amounts of residues were found in the 0-10 and 10-20 cm layers. The application of GC to the soil increased the persistence of both herbicides, and prevented the rapid leaching of triasulfuron in the soil, but the leaching of prosulfocarb was not inhibited. The influence of single or combined formulations was observed for triasulfuron, but not for prosulfocarb. The results obtained highlight the interest of obtaining field data to design rational joint applications of GC and herbicides to prevent the possible decrease in their effectiveness for weeds or the risk of water contamination.

Adsorption-desorption and hysteresis phenomenon of tebuconazole in Colombian agricultural soils: Experimental assays and mathematical approaches

The adsorption-desorption, hysteresis phenomenon, and leachability of tebuconazole were studied for Inceptisol and Histosol soils at the surface (0-10 cm) and in the subsurface (40-50 cm) of an agricultural region from Colombia by the batch-equilibrium method and mathematical approaches. The experimental K_fa and K_d (L kg^-1) values (7.9-289.2) decreased with depth for the two Inceptisols and increased with depth for the Histosol due to the organic carbon content, aryl and carbonyl carbon types. Single-point and desorption isotherms depended on adsorption reversibility and suggested that tebuconazole showed hysteresis; which can be adequately evaluated with the single-point desorption isotherm and the linear model using the hysteresis index HI. The most suitable mathematical approach to estimate the adsorption isotherms of tebuconazole at the surface and in the subsurface was that considering the combination of the n-octanol-water partition coefficient, pesticide solubility, and the mass-balance concept. Tebuconazole had similar moderate mobility potential as compared with the values of other studies conducted in temperate amended and unamended soils, but the risk of the fungicide to pollute groundwater sources increased when the pesticide reached subsurface soil layers, particularly in the Inceptisols.

Leaching of two fungicides in spent mushroom substrate amended soil: Influence of amendment rate, fungicide ageing and flow condition

A study has been conducted on the leaching of two fungicides, tebuconazole and cymoxanil, in a soil amended with spent mushroom substrate (SMS), with an evaluation of how different factors influence this process. The objective was based on the potential use of SMS as a biosorbent for immobilizing pesticides in vulnerable soils, and the need to know how it could affect the subsequent transport of these retained compounds. Breakthrough curves (BTCs) for ¹⁴C-fungicides, non-incubated and incubated over 30days, were obtained in columns packed with an unamended soil (S), and this soil amended with SMS at rates of 5% (S+SMS5) and 50% (S+SMS50) under saturated and saturated-unsaturated flows. The highest leaching of tebuconazole (>50% of the total ¹⁴C added) was found in S when a saturated water flow was applied to the column, but the percentage of leached fungicide decreased when a saturated-unsaturated flow was applied in both SMS-amended soils. Also a significant decrease in leaching was observed for tebuconazole after incubation in the column, especially in S+SMS50 when both flows were applied. Furthermore, cymoxanil leaching was complete in S and S+SMS when a saturated flow was applied, and maximum peak concentrations were reached at 1pore volume (PV), although BTCs showed peaks with lower concentrations in S+SMS. The amounts of cymoxanil retained only increased in S+SMS when a saturated-unsaturated flow was applied. A more relevant effect of SMS for reducing the leaching of fungicide was observed when cymoxanil was previously incubated in the column, although mineralization was enhanced in this case. These results are of interest for extending SMS application on the control of the leaching of fungicides with different physicochemical characteristics after different ageing times in the soil and water flow conditions applied.

Biocide Runoff from Building Facades: Degradation Kinetics in Soil

Biocides are common additives in building materials. In-can and film preservatives in polymer-resin render and paint, as well as wood preservatives are used to protect facade materials from microbial spoilage. Biocides leach from the facade material with driving rain, leading to highly polluted runoff water (up to several mg L^-1 biocides) being infiltrated into the soil surrounding houses. In the present study the degradation rates in soil of 11 biocides used for the protection of building materials were determined in laboratory microcosms. The results show that some biocides are degraded rapidly in soil (e.g., isothiazolinones: T_1/2 < 10 days) while others displayed higher persistence (e.g., terbutryn, triazoles: T_1/2 ≫ 120 days). In addition, mass balances of terbutryn and octylisothiazolinone were determined, including nine (terbutryn) and seven (octylisothiazolinone) degradation products, respectively. The terbutryn mass balance could be closed over the entire study period of 120 days and showed that relative persistent metabolites were formed, while the mass balances for octylisothiazolinone could not be closed. Octylisothiazolinone degradation products did not accumulate over time suggesting that the missing fraction was mineralized. Microtox-tests revealed that degradation products were less toxic toward the bacterium Aliivibrio fischeri than their parent compounds. Rain is mobilizing these biocides from the facades and transports them to the surrounding soils; thus, rainfall events control how often new input to the soil occurs. Time intervals between rainfall events in Northern Europe are shorter than degradation half-lives even for many rapidly degraded biocides. Consequently, residues of some biocides are likely to be continuously present due to repeated input and most biocides can be considered as "pseudo-persistent"-contaminants in this context. This was verified by (sub)urban soil screening, where concentrations of up to 0.1 μg g^-1 were detected for parent compounds as well as terbutryn degradation products in soils below biocide treated facades.

Influence of Herbicide Triasulfuron on Soil Microbial Community in an Unamended Soil and a Soil Amended with Organic Residues

The effect of organic amendments and pesticides on a soil microbial community has garnered considerable interest due to the involvement of microorganisms in numerous soil conservation and maintenance reactions. The aim of this work was to assess the influence on a soil microbial community of the simultaneous application of the herbicide triasulfuron at three doses (2, 10, and 50 mg kg-1), with an organic amendment [sewage sludge (SS) or green compost (GC)]. Dissipation kinetics, soil microbial biomass, dehydrogenase activity (DHA) and respiration, and the profile of phospholipid fatty acids (PLFAs) extracted from the soil, were determined in unamended (S) soil and amended (S+SS and S+GC) ones. Triasulfuron dissipation followed the single first-order kinetics model. Half-life (DT50) values were higher in the amended soils than in the unamended one for the 10 and 50 mg kg-1 doses. The dissipation rates were lower in the S+GC soil for the three herbicide doses applied. In general, soil biomass, DHA and respiration values increased in SS- and GC-amended soils compared to the unamended one. DHA values decreased (S and S+SS) or increased (S+GC) with the incubation time of soil with herbicide at the different doses applied. Respiration values increased with the herbicide doses applied and decreased with the incubation time, although maximum values were obtained for soils treated with the highest dose after 70 days of incubation. PLFA analysis indicated different effects of triasulfuron on the soil microbial community structure depending on the organic amendments. While the increasing triasulfuron doses resulted in deeper alterations in the S soil, the time after triasulfuron application was the most important variation in the S+SS and S+GC soils. The overall results indicate that the soil amendment has an effect on herbicide dissipation rate and the soil microbial community. Initially, a high dose of triasulfuron had detrimental effects on the soil microbial community, which is important in the case of the long-term use of this compound.

Dissipation and adsorption of isoproturon, tebuconazole, chlorpyrifos and their main transformation products under laboratory and field conditions

Assessment of dissipation constitutes an integral part of pesticides risk assessment since it provides an estimate of the level and the duration of exposure of the terrestrial ecosystem to pesticides. Within the frame of an overall assessment of the soil microbial toxicity of pesticides, we investigated the dissipation of a range of dose rates of three model pesticides, isoproturon (IPU), tebuconazole (TCZ), and chlorpyrifos (CHL), and the formation and dissipation of their main transformation products following a tiered lab-to-field approach. The adsorption of pesticides and their transformation products was also determined. IPU was the least persistent pesticide showing a dose-dependent increase in its persistence in both laboratory and field studies. CHL dissipation showed a dose-dependent increase under laboratory conditions and an exact opposite trend in the field. TCZ was the most persistent pesticide under lab conditions showing a dose-dependent decrease in its dissipation, whereas in the field TCZ exhibited a biphasic dissipation pattern with extrapolated DT90s ranging from 198 to 603.4days in the ×1 and ×2 dose rates, respectively. IPU was demethylated to mono- (MD-IPU) and di-desmethyl-isoproturon (DD-IPU) which dissipated following a similar pattern with the parent compound. CHL was hydrolyzed to 3,5,6-trichloro-2-pyridinol (TCP) which dissipated showing a reverse dose-dependent pattern compared to CHL. Pesticides adsorption affinity increased in the order IPU<TCZ<CHL. IPU transformation products showed low affinity for soil adsorption, whereas TCP was weakly adsorbed compared to its parent compound. The temporal dissipation patterns of the pesticides and their transformation products will be used as exposure inputs for assessment of their soil microbial toxicity.

Impact of Spent Mushroom Substrates on the Fate of Pesticides in Soil, and Their Use for Preventing and/or Controlling Soil and Water Contamination: A Review

Intensive crop production involves a high consumption of pesticides. This is a cause of major environmental concern because the presence of pesticides in water is becoming increasingly common. Physicochemical methods based on soil modification with organic residues have been developed to enhance the immobilization and/or degradation of pesticides in agricultural soils, which may control both the diffuse and the point pollution of soils and waters. This review summarizes the influence of spent mushroom substrate (SMS) on the environmental fate of pesticides when both are simultaneously applied in agriculture. The processes of adsorption, leaching and dissipation of these compounds in SMS-amended soils were evaluated at laboratory and field scale. Relationships were established between the experimental parameters obtained and the properties of the soils, the SMS, and the pesticides in order to determine the effect that the application of SMS in agricultural soils has on the environmental impact of pesticides. Accordingly, this review highlights the use of SMS as a strategy for the prevention and/or control of soil and water contamination by pesticides to strike a balance between agricultural development and the use of these compounds.

Effect of different rates of spent mushroom substrate on the dissipation and bioavailability of cymoxanil and tebuconazole in an agricultural soil

Physicochemical methods to immobilize pesticides in vulnerable soils are currently being developed to prevent water contamination. Some of these methods include the use of different organic residues to modify soils because they could limit the transport of pesticides and/or facilitate their dissipation. Spent mushroom substrate (SMS) may be used for these purposes. Accordingly a study was conducted under laboratory conditions to know the dissipation and bioavailability of the fungicides cymoxanil and tebuconazole over time in a vineyard soil amended with two rates of spent mushroom substrate (SMS) (5% and 50% (w/w)), selected to prevent the diffuse or point pollution of soil. The dissipation of cymoxanil was more rapid than that of tebuconazole in the different soils studied. The dissipation rate was higher in the amended soil than in the unamended one for both compounds, while no significant differences were observed between the amended soils in either case. An apparent dissipation occurred in the amended soil due to the formation of non-extractable residues. Bound residues increased with incubation time for tebuconazole, although a proportion of this fungicide was bioavailable after 303days. The major proportion of cymoxanil was tightly bound to the amended soil from the start, although an increasing fraction of bound fungicide was bioavailable for mineralization. Soil dehydrogenase activity was significantly affected by SMS application and incubation time; however, it was not significantly modified by fungicide application. The significance of this research suggests that SMS applied at a low or high rate to agricultural soil can be used to prevent both the diffuse or point pollution of soil through the formation of non-extractable residues, although more research is needed to discover the time that fungicides remain adsorbed into the soil decreasing either bioavailability (tebuconazole) or mineralization (cymoxanil) in SMS-amended soils.

The potential of organic substrates based on mushroom substrate and straw to dissipate fungicides contained in effluents from the fruit-packaging industry - Is there a role for Pleurotus ostreatus?

Citrus fruit-packaging plants (FPP) produce large wastewater volumes with high loads of fungicides like ortho-phenylphenol (OPP) and imazalil (IMZ). No methods are in place for the treatment of those effluents and biobeds appear as a viable alternative. We employed a column study to investigate the potential of spent mushroom substrate (SMS) of Pleurotus ostreatus, either alone or in mixture with straw and soil plus a mixture of straw /soil to retain and dissipate IMZ and OPP. The role of P. ostreatus on fungicides dissipation was also investigated by studying in parallel the performance of fresh mushroom substrate of P. ostreatus (FMS) and measuring lignolytic enzymatic activity in the leachates. All substrates effectively reduced the leaching of OPP and IMZ which corresponded to 0.014-1.1% and 0.120-0.420% of their initial amounts respectively. Mass balance analysis revealed that FMS and SMS/Straw/Soil (50/25/25 by vol) offered the most efficient removal of OPP and IMZ from wastewaters respectively. Regardless of the substrate, OPP was restricted in the top 0-20cm of the columns and was bioavailable (extractable with water), compared to IMZ which was less bioavailable (extractable with acetonitrile) but diffused at deeper layers (20-50, 50-80cm) in the SMS- and Straw/Soil-columns. PLFAs showed that fungal abundance was significantly lower in the top layer of all substrates from where the highest pesticide amounts were recovered suggesting an inhibitory effect of fungicides on total fungi in the substrates tested. Our data suggest that biobeds packed with SMS-rich substrates could ensure the efficient removal of IMZ and OPP from wastewaters of citrus FPP.

Identification and characterization of tebuconazole transformation products in soil by combining suspect screening and molecular typology

Pesticides generate transformation products (TPs) when they are released into the environment. These TPs may be of ecotoxicological importance. Past studies have demonstrated how difficult it is to predict the occurrence of pesticide TPs and their environmental risk. The monitoring approaches mostly used in current regulatory frameworks target only known ecotoxicologically relevant TPs. Here, we present a novel combined approach which identifies and categorizes known and unknown pesticide TPs in soil by combining suspect screening time-of-flight mass spectrometry with in silico molecular typology. We used an empirical and theoretical pesticide TP library for compound identification by both non-target and target time-of-flight (tandem) mass spectrometry, followed by structural proposition through a molecular structure correlation program. In silico molecular typology was then used to group TPs according to common molecular descriptors and to indirectly elucidate their environmental parameters by analogy to known pesticide compounds with similar molecular descriptors. This approach was evaluated via the identification of TPs of the triazole fungicide tebuconazole occurring in soil during a field dissipation study. Overall, 22 empirical and 12 yet unknown TPs were detected, and categorized into three groups with defined environmental properties. This approach combining suspect screening time-of-flight mass spectrometry with molecular typology could be extended to other organic pollutants and used to rationalize the choice of TPs to be investigated towards a more comprehensive environmental risk assessment scheme.

Changes in the persistence of two phenylurea herbicides in two Mediterranean soils under irrigation with low- and high-quality water: A laboratory approach

The disappearance of two phenylurea herbicides, chlorotoluron (CHL) and isoproturon (IPU), in two Mediterranean soils, an agricultural calcareous soil (S5) and an organic forest soil (S2), was assessed under irrigation with high- and low-quality water. Irrigation with wastewater, as opposed to irrigation with high-quality water, increased the degradation rate of both herbicides in both soils. For each soil, the decay rate of IPU was always higher than that of CHL, and both pesticides disappeared more rapidly from S5 with lower clay and organic carbon content than from S2. The degradation rate was inversely related with pesticide sorption on soil, because increased sorption would reduce pesticide bioavailability for decomposition. In most cases the residual concentration in soil of both phenylurea herbicides was better fitted to a bi-exponential decay model than to first-order or first-order with plateau models. Dehydrogenase activity, used as an indication of microbial activity, was very high in S2 in comparison with S5, but was not related to pesticide disappearance.

Dissipation of the fungicide hexaconazole in oil palm plantation

Hexaconazole is a potential fungicide to be used in the oil palm plantation for controlling the basal stem root (BSR) disease caused by Ganoderma boninense. Therefore, the dissipation rate of hexaconazole in an oil palm agroecosystem under field conditions was studied. Two experimental plots were treated with hexaconazole at the recommended dosage of 4.5 g a.i. palm(-1) (active ingredient) and at double the recommended dosage (9.0 g a.i. palm(-1)), whilst one plot was untreated as control. The residue of hexaconazole was detected in soil samples in the range of 2.74 to 0.78 and 7.13 to 1.66 mg kg(-1) at the recommended and double recommended dosage plots, respectively. An initial relatively rapid dissipation rate of hexaconazole residues occurred but reduced with time. The dissipation of hexaconazole in soil was described using first-order kinetics with the value of coefficient regression (r (2) > 0.8). The results indicated that hexaconazole has moderate persistence in the soil and the half-life was found to be 69.3 and 86.6 days in the recommended and double recommended dosage plot, respectively. The results obtained highlight that downward movement of hexaconazole was led by preferential flow as shown in image analysis. It can be concluded that varying soil conditions, environmental factors, and pesticide chemical properties of hexaconazole has a significant impact on dissipation of hexaconazole in soil under humid conditions.

Application of mesotrione at different doses in an amended soil: Dissipation and effect on the soil microbial biomass and activity

The aim of this work was to estimate the dissipation of mesotrione applied at three doses (2, 10 and 50 mg kg(-1) dw) in an unamended agricultural soil, and this same soil amended with two organic residues (green compost (C) and sewage sludge (SS)). The effects of herbicide and organic residue on the abundance and activity of soil microbial communities were also assessed by determining soil microbial parameters such as biomass, dehydrogenase activity (DHA), and respiration. Lower dissipation rates were observed for a higher herbicide dose. The highest half-life (DT50) values were observed in the SS-amended soil for the three herbicide doses applied. Biomass values increased in the amended soils compared to the unamended one in all the cases studied, and increased over the incubation period in the SS-amended soil. DHA mean values significantly decreased in the SS-amended soil, and increased in the C-amended soil compared to the unamended ones, under all conditions. At time 0 days, respiration values were significantly higher in SS-amended soils (untreated and treated with mesotrione) than in the unamended and C-amended soils. The effect of mesotrione on soil biomass, DHA and respiration was different depending on incubation time and soil amendment and herbicide dose applied. The results support the need to consider the possible non-target effects of pesticides and organic amendments simultaneously applied on soil microbial communities to prevent negative impacts on soil quality.

Field versus laboratory experiments to evaluate the fate of azoxystrobin in an amended vineyard soil

This study reports the effect that adding spent mushroom substrate (SMS) to a representative vineyard soil from La Rioja region (Spain) has on the behaviour of azoxystrobin in two different environmental scenarios. Field dissipation experiments were conducted on experimental plots amended at rates of 50 and 150 t ha(-1), and similar dissipation experiments were simultaneously conducted in the laboratory to identify differences under controlled conditions. Azoxystrobin dissipation followed biphasic kinetics in both scenarios, although the initial dissipation phase was much faster in the field than in the laboratory experiments, and the half-life (DT50) values obtained in the two experiments were 0.34-46.3 days and 89.2-148 days, respectively. Fungicide residues in the soil profile increased in the SMS amended soil and they were much higher in the top two layers (0-20 cm) than in deeper layers. The persistence of fungicide in the soil profile is consistent with changes in azoxystrobin adsorption by unamended and amended soils over time. Changes in the dehydrogenase activity (DHA) of soils under different treatments assayed in the field and in the laboratory indicated that SMS and the fungicide had a stimulatory effect on soil DHA. The results reveal that the laboratory studies usually reported in the literature to explain the fate of pesticides in amended soils are insufficient to explain azoxystrobin behaviour under real conditions. Field studies are necessary to set up efficient applications of SMS and fungicide, with a view to preventing the possible risk of water contamination.

Dissipation, metabolism and sorption of pesticides used in fruit-packaging plants: Towards an optimized depuration of their pesticide-contaminated agro-industrial effluents

Wastewaters from the fruit-packaging industry constitute a serious point source contamination with pesticides. In the absence of effective depuration methods, they are discharged in municipal wastewater treatment plants or spread to land. Modified biobeds could be an applicable solution for their treatment. We studied the dissipation of thiabendazole (TBZ), imazalil (IMZ), ortho-phenylphenol (OPP), diphenylamine (DPA) and ethoxyquin (EQ), used by the fruit-packaging industry, in anaerobically digested sewage sludge, liquid aerobic sewage sludge and in various organic substrates (biobeds packing materials) composed of soil, straw and spend mushroom substrate (SMS) in various volumetric ratios. Pesticide sorption was also determined. TBZ and IMZ showed higher persistence especially in the anaerobically digested sewage sludge (DT50=32.3-257.6d), in contrast to OPP and DPA which were rapidly dissipated especially in liquid aerobic sewage sludge (DT50=1.3-9.3d). EQ was rapidly oxidized mainly to quinone imine (QI) which did not persist and dimethyl ethoxyquinoline (EQNL, minor metabolite) which persisted for longer. Sterilization of liquid aerobic sewage sludge inhibited pesticide decay verifying the microbial nature of pesticide dissipation. Organic substrates rich in SMS showed the highest dissipation capacity with TBZ and IMZ DT50s of ca. 28 d compared to DT50s of >50 d in the other substrates. TBZ and IMZ showed the highest sorption affinity, whereas OPP and DPA were weakly sorbed. Our findings suggest that current disposal practices could not guarantee an efficient depuration of effluents from the fruit-packaging industry, whereas SMS-rich biobed organic substrates show efficient depuration of effluents from the fruit-packaging industry via accelerated dissipation even of recalcitrant fungicides.

Modeling fungicides mobility in undisturbed vineyard soil cores unamended and amended with spent mushroom substrates

The performance of the pesticide fate model PRZM to predict the fate of two fungicides, penconazole and metalaxyl, and the major metabolite of metalaxyl (CGA-62826), in amended and unamended vineyard soils was tested from undisturbed soils columns experiments. Three different treatments were tested in two soils: control soil (unamended), and soil amended with fresh or composted spent mushroom substrates, which correspond to common agricultural practices in Spain. Leaching experiments were performed under non-saturated flow conditions. The model was parameterized with laboratory and literature data, and using pedotransfer functions. It was first calibrated for water flow against chloride breakthrough curves. The key parameter was the hydrodynamic dispersion coefficient (DISP). No leaching of penconazole, the most hydrophobic fungicide, was observed. It remained in the top 0-8 cm of the column. In any case, simulations were highly correlated to the experimental results. On the contrary, metalaxyl and its metabolite were consistently found in the leachates. A calibration step of the Kd of metalaxyl and CGA-62826 and of DISP for CGA-62826 was necessary to obtain good prediction of the leaching of both compounds. PRZM generally simulated acceptable metalaxyl vertical distribution in the soil profiles although results were overestimated for its metabolite. Nevertheless, PRZM can be reasonably used to assess the leaching (through breakthrough curves) and vertical distribution of fungicides in amended soils, knowing their DISP values.

Pesticide mobility and leachate toxicity in two abandoned mine soils. Effect of organic amendments

Abandoned mine areas, used in the past for the extraction of minerals, constitute a degraded landscape which needs to be reintegrated to productive or leisure activities. However these soils, mainly composed by silt or sand and with low organic matter content, are vulnerable to organic and inorganic pollutants posing a risk to the surrounding ecosystems and groundwater. Soils from two mining areas from Andalusia were evaluated: one from Nerva (NCL) in the Iberian Pyrite Belt (SW Andalusia) and another one from the iron Alquife mine (ALQ) (SE Andalusia). To improve soil properties and fertility two amendments, stabilised sewage sludge (SSL) and composted sewage sludge (CSL), were selected. The effect of amendment addition on the mobility of two model pesticides, thiacloprid and fenarimol, was assessed using soil columns under non-equilibrium conditions. Fenarimol, more hydrophobic than thiacloprid, only leached from native ALQ, a soil with lower organic carbon (OC) content than NCL (0.21 and 1.4%, respectively). Addition of amendments affected differently pesticide mobility: thiacloprid in the leachates was reduced by 14% in NCL-SSL and by 4% in ALQ-CSL. Soil OC and dissolved OC were the parameters which explained pesticide residues in soil. Chemical analysis revealed that leachates from the different soil columns did not contain toxic element levels, except As in NCL soil. Finally ecotoxicological data showed moderate toxicity in the initial leachates, with an increase coinciding with pesticide maximum concentration. The addition of SSL slightly reduced the toxicity towards Vibrio fischeri, likely due to enhanced retention of pesticides by amended soils.

Use of raw or incubated organic wastes as amendments in reducing pesticide leaching through soil columns

Soil amendment with organic wastes is becoming a widespread management practice since it can effectively solve the problems of uncontrolled waste accumulation and improve soil quality. However, when simultaneously applied with pesticides, organic wastes can significantly modify the environmental behaviour of these compounds. This study evaluated the effect of sewage sludges (SS), grape marc (GM) and spent mushroom substrates (SMS) on the leaching of linuron, diazinon and myclobutanil in packed columns of a sandy soil with low organic matter (OM) content (<1%). Soil plus amendments had been incubated for one month (1 m) or 12 months (12 m). Data from the experimental breakthrough curves (BTCs) were fitted to the one-dimensional transport model CXTFIT 2.1. All three amendments reduced leaching of linuron and myclobutanil relative to unamended soil. SMS was the most effective in reducing leaching of these two compounds independent of whether soil was incubated for 1 m or 12 m. Soil amendments increased retardation coefficients (Rexp) by factors of 3 to 5 for linuron, 2 to 4 for diazinon and 3 to 5 for myclobutanil relative to unamended soil. Leaching of diazinon was relatively little affected by soil amendment compared to the other two compounds and both SS and SMS amendment with 1m incubation resulted in enhanced leaching of diazinon. The leaching data for linuron and myclobutanil were well described by CXTFIT (mean square error, MSE<4.9·10(-7) and MSE<7.0·10(-7), respectively) whereas those of diazinon were less well fitted (MSE<2.1·10(-6)). The BTCs for pesticides were similar in soils incubated for one month or one year, indicating that the effect of amendment on leaching persists over relatively long periods of time.

The influence of filter mud compost and Tithonia diversifolia leaves on the dissipation of diuron in soils within the Nzoia River Drainage Basin, Kenya

The aim of the study was to evaluate the environmental impact of filter mud compost and Tithonia diversifoila amendments on the dissipation of diuron in sugarcane cultivated soils. Filter mud compost is the by-product of sugarcane processing, while T. diversifoila is a common local plant that grows within the study region. The dissipation of diuron was significantly enhanced with DT(50) of 15 and 16 days (p < 0.05) in soils amended with filter mud compost and T. diversifoila, respectively compared to 26 days in non-amended soils. Residues of 0.93 %, 1.83 % and 5.40 % of the initial applied diuron were recorded at the end of the experiment in the three treatments, respectively. The residues of 3,4-dichlorophenylmethylurea metabolite were 22.93 %, 25.92 % and 30.93 %, while 10.19 %, 12.19 % and 15.46 % of 3,4-dichloroaniline metabolite remained in soil after 112 days in the three treatments, respectively.

Dissipation of fungicides in a vineyard soil amended with different spent mushroom substrates

The degradation kinetics and formation of metabolites for fungicides of different chemical classes (iprovalicarb, metalaxyl, penconazole, and pyrimethanil) and determination of bound residues for metalaxyl and penconazole were studied in both an unamended vineyard soil and in the same soil amended with two spent mushroom substrates (composted (C-SMS1) and fresh (F-SMS2)). The degradation kinetics was fitted to single first-order or first-order multicompartment patterns. Degradation rates decreased in C-SMS1-amended soils for all fungicides as compared to unamended soil, but in F-SMS2-amended soils, they decreased only for iprovalicarb and penconazole. The DT(50) values were higher by up to 1.8 (metalaxyl), 3.8 (pyrimethanil), 4.1 (iprovalicarb), and >1000 (penconazole) times in the soil plus C-SMS1 compared to those for soil plus F-SMS2 or unamended soil. The dissipation mechanism recorded the highest mineralization in the unamended soil for (14)C-metalaxyl and (14)C-penconazole, with the highest formation of nonextractable residues in the F-SMS2-amended soil for (14)C-metalaxyl. The results are consistent with (1) the chemical characteristics of each SMS (total and soluble organic carbon) controlling sorption and the bioavailability of fungicides and (2) the microbial activity of SMS-amended soils, which affects fungicide biodegradation. The findings of this work highlight the potential of SMS amendments with different characteristics to decrease or increase the degradation rate of a fungicide in a vineyard soil.

Effect of olive-mill waste addition to soil on sorption, persistence, and mobility of herbicides used in Mediterranean olive groves

Laboratory and field experiments were conducted to evaluate the effect of olive-mill waste (OMW) addition to a Mediterranean olive grove soil on sorption, persistence, and mobility of two herbicides which are simultaneously applied for weed control in olive groves: terbuthylazine (TA) and fluometuron (FM). Laboratory batch sorption experiments showed that OMW addition to the soil at rates of 5 and 10% (w/w) greatly enhanced the sorption of both herbicides, thus suggesting that amendment with OMW could be useful to enhance the retention and reduce the mobility of FM and TA in the soil. Incubation experiments showed that OMW increased the persistence of FM and had little effect on the long persistence of TA in the soil studied. A demonstration field experiment was also conducted in field plots with a slope of about 5%, either unamended or amended with OMW at a rate of 10 kg m⁻², and then treated with a commercial formulation containing a mixture of TA and FM. Extraction of field soil samples, taken from different soil depths (0-5, 5-10, 10-20, and 20-30 cm) at different times after herbicide application, showed that both TA and FM moved deeper in unamended soil than in OMW-amended soil, and that OMW addition affected the persistence of FM in the toplayer, increasing its half-life from 24 to 58 days, while having little effect on the persistence of TA. Thus, data obtained under real field conditions were consistent with those obtained under controlled laboratory conditions. Preliminary herbicide runoff data indicated that the total herbicide runoff losses were also reduced upon OMW addition. Addition of OMW could be beneficial in reducing the mobility of TA and FM in olive grove soils, and also in increasing the persistence of FM in soils where this herbicide could be rapidly degraded.