Biobeds for environmental protection from pesticide use--a review

Sustainable indigenous bio-mixture for restoration the soil point source pollution with special reference to chlorpyrifos

Improper pesticide handling is the main cause of contamination of the environment in agricultural systems. This could be caused by leakage of spraying liquid, leftovers, and inappropriate washing of spraying equipment. This study assessed the ability of suggested biomixture modules for remediate repetitive cycles of high chlorpyrifos doses. In three consecutive treatments, four tested modules were contaminated with 160 µg g-1 chlorpyrifos. Chlorpyrifos residues, dehydrogenase activity, and microbial respiration were continuously monitored for 22 weeks. Six bacterial consortia were isolated at the end of the experiment from four treated modules (B+3, BF+3, S+3, and SF+3) and two from untreated modules (B and S). The isolated consortium efficiency in degrading chlorpyrifos was studied. The results revealed that the best chlorpyrifos removal efficiency was achieved when using the stimulated biomixture module (BF) recorded 98%, 100%, and 89%, at the end of three chlorpyrifos treatments, respectively. Such removal efficiency was compatible with the biological activity results of the tested modules: dehydrogenase activity and microbial respiration. There was no difference in the efficiency among the S, B, and BF+3 consortia. The results presented here demonstrate that the combination of vermicompost, wheat straw, soil, and NPK (stimulated biomixture module) can successfully reduce the risk of a point source of pesticide pollution.

A review on the management of rinse wastewater in the agricultural sector

Pesticides have become indispensable compounds to sustain global food production. However, a series of sustainable agricultural practices must be ensured to minimize health and environmental risks, such as eco-friendly cultivation techniques, the transition to biopesticides, appropriate hygiene measures, etc. Hygiene measures should include the management of rinse wastewater (RWW) produced when cleaning agricultural equipment and machinery contaminated with pesticides (among other pollutants), such as sprayers or containers. Although some technical guidelines encourage the reuse of RWW in agricultural fields, in many cases the application of specialized treatments is a more environmentally friendly option. Solar photocatalysis was found to be the most widely studied physical-chemical method, especially in regions with intense solar radiation, generally using catalysts such as TiO2, Na2S2O8, and H2O2, operating for relatively short treatment periods (usually from 10 min to 9 h) and requiring accumulated radiation levels typically ranging from 3000 to 10000 kJ m-2. Biological treatments seem to be particularly suitable for this application. Among them, biobed is a well-established and robust technology for the treatment of pesticide-concentrated water in some countries, with operating periods that typically range from 1 to 24 months, and with temperatures preferably close to 20 °C; but further research is required for its implementation in other regions and/or conditions. Solar photocatalysis and biobeds are the only two systems that have been tested in full-scale treatments. Alternatively, fungal bioremediation using white rot fungi has shown excellent efficiencies in the degradation of pesticides from agricultural wastewater. However, greater efforts should be invested in gathering more information to consolidate these technologies and expand their use in the agricultural sector.

Biological treatment of pesticide-containing wastewater from coffee crops: selection and optimization of a biomixture and biobed design

The biopurification systems (BPS) or biobeds are employed for the treatment of pesticide-containing wastewater of agricultural origin. The use of these devices for pesticide removal requires the proper optimization of the composition of biomixtures (BPS active matrix) according to the target pesticides applied on a specific crop and the available materials used in their elaboration. This work aims to design a biomixture for the simultaneous treatment of several pesticides applied in coffee crops, according to local practices in Costa Rica. Three biomixtures containing either coffee husk, coconut fiber or rice husk (as the lignocellulosic substrate) were applied for the removal of 12 pesticides. The profiles of pesticide elimination and the mineralization of radiolabeled chlorpyrifos (14C-chlorpyrifos) revealed that the best performance was achieved with the coconut fiber biomixture, even though similar detoxification patterns were determined in every biomixture (according to immobilization in Daphnia magna and germination tests in Lactuca sativa). The optimization of this biomixture's composition by means of a central composite design permitted the definition of two optimal compositions (compost:soil:coconut fiber, % v/v) that maximized pesticide removal: i. 29:7.3:63.7 and ii. 11:7.3:81.7. The validation of these optimized compositions also included the use of an alternative soil from another coffee farm and resulted in overall DT50 values of 7.8-9.0 d for the pesticide mixture. Considering the removal kinetics in the optimized biomixture, a 1 m3 BPS prototype was dimensioned to be eventually used in local coffee farms. This work provides relevant information for the design and implementation of BPS at on-farm conditions for the treatment of pesticide-containing wastewater of a major crop.

Biodegradation of Iprodione and Chlorpyrifos Using an Immobilized Bacterial Consortium in a Packed-Bed Bioreactor

This work provides the basis for implementing a continuous treatment system using a bacterial consortium for wastewater containing a pesticide mixture of iprodione (IPR) and chlorpyrifos (CHL). Two bacterial strains (Achromobacter spanius C1 and Pseudomonas rhodesiae C4) isolated from the biomixture of a biopurification system were able to efficiently remove pesticides IPR and CHL at different concentrations (10 to 100 mg L^-1) from the liquid medium as individual strains and free consortium. The half-life time (T_1/2) for IPR and CHL was determined for individual strains and a free bacterial consortium. However, when the free bacterial consortium was used, a lower T_1/2 was obtained, especially for CHL. Based on these results, an immobilized bacterial consortium was formulated with each bacterial strain encapsulated individually in alginate beads. Then, different inoculum concentrations (5, 10, and 15% w/v) of the immobilized consortium were evaluated in batch experiments for IPR and CHL removal. The inoculum concentration of 15% w/v demonstrated the highest pesticide removal. Using this inoculum concentration, the packed-bed bioreactor with an immobilized bacterial consortium was operated in continuous mode at different flow rates (30, 60, and 90 mL h^-1) at a pesticide concentration of 50 mg L^-1 each. The performance in the bioreactor demonstrated that it is possible to efficiently remove a pesticide mixture of IPR and CHL in a continuous system. The metabolites 3,5-dichloroaniline (3,5-DCA) and 3,5,6-trichloro-2-pyridinol (TCP) were produced, and a slight accumulation of TCP was observed. The bioreactor was influenced by TCP accumulation but was able to recover performance quickly. Finally, after 60 days of operation, the removal efficiency was 96% for IPR and 82% for CHL. The findings of this study demonstrate that it is possible to remove IPR and CHL from pesticide-containing wastewater in a continuous system.

Actinobacteria bioaugmentation and substrate evaluation for biobeds useful for the treatment of atrazine residues in agricultural fields

Biopurification systems (BPS) or biobeds are bioprophylaxis systems to prevent pesticide point-source contamination, whose efficiency relies mostly on the pesticide removal capacity of the biomixture, the majority component of a BPS. The adaptation of the components of the biomixtures to local availabilities is a key aspect to ensure the sustainability of the system. In this work, the removal of atrazine (ATZ) was evaluated in biomixtures formulated with three sugarcane by-products as alternative lignocellulosic substrates. Based on the capacity of actinobacteria to tolerate and degrade diverse pesticides, the effect of biomixtures bioaugmentation with actinobacteria was evaluated as a strategy to enhance the depuration capacity of biobeds. Also, the effect of ATZ and/or the bioaugmentation on microbial developments and enzymatic activities were studied. The biomixtures formulated with bagasse, filter cake, or harvest residue, reached pesticide removal values of 37-41% at 28 d of incubation, with t_1/2 between 37.9 ± 0.4 d and 52.3 ± 0.4 d. The bioaugmentation with Streptomyces sp. M7 accelerated the dissipation of the pesticide in the biomixtures, reducing ATZ t_1/2 3-fold regarding the controls, and achieving up to 72% of ATZ removal. Atrazine did not exert a clear effect on microbial developments, although most of the microbial counts were less in the contaminated biomixtures at the end of the assay. The bioaugmentation improved the development of the microbiota in general, specially actinobacteria and fungi, regarding the non-bioaugmented systems. The inoculation with Streptomyces sp. M7 enhanced acid phosphatase activity and/or reversed a possible effect of the pesticide over this enzymatic activity.

A novel and affordable bioaugmentation strategy with microbial extracts to accelerate the biodegradation of emerging contaminants in different media

This study describes a new bioaugmentation alternative based on the application of aqueous aerated extracts from a biomixture acclimated with ibuprofen, diclofenac and triclosan. This bioaugmentation strategy was assayed in biopurification systems (BPS) and in contaminated aqueous solutions to accelerate the removal of these emerging contaminants. Sterilized extracts or extracts from the initial uncontaminated biomixture were used as controls. In BPS, the dissipation of 90% of diclofenac and triclosan required, respectively, 60 and 108 days less than in the controls. The metabolite methyl-triclosan was determined at levels 12 times lower than in controls. In the bioaugmented solutions, ibuprofen was almost completely eliminated (99%) in 21 days and its hydroxylated metabolites were also determined to be at lower levels than in the controls. The plasmidome of acclimated biomixtures and its extract appeared to maintain certain types of plasmids but degradation related genes became less evident. Several dominant OTUs found in the extract identified as Flavobacterium and Fluviicola of the phylum Bacteroidetes, Thermomicrobia (phylum Chloroflexi) and Nonomuraea (phylum Actinobacteria), may be responsible for the enhanced dissipation of these contaminants. This bioaugmentation strategy represents an advantageous tool to facilitate in situ bioaugmentation.

Detection of glyphosate residues in feed, saliva, urine and faeces from a cattle farm: a pilot study

Forty-two samples of feed, saliva, urines, and faeces collected from a cattle farm were investigated with the aim to evaluate the occurrence of glyphosate in faeces, urine and saliva. Glyphosate in the feed was also quantified to understand how it was assimilated by mammals. All cows excreted glyphosate in their faeces at concentrations between 57 and 983 ng g-1. In contrast, only 55% of urine and one sample of saliva tested positive. Most of the feeds demonstrated a non-negligible presence of glyphosate. In particular, a silage containing soybeans from genetically modified cultivation showed a concentration one order of magnitude higher than the other feeds. This study aims to provide the first complete determination of glyphosate in a cattle farm, considering the possible re-entry into the environment through the spreading of liquid and solid sewage and its possible impact on groundwater.

Metagenomic and Metatranscriptomic Analyses Reveal that Biobed Systems can Enrich for Antibiotic Resistance and Genetic Mobility Genes

Antibiotic resistance gene pollution in the environment has been identified as a potential contributor to the global issue of antibiotic resistance prevalence, creating a need to identify and characterize environmental reservoirs for antibiotic resistance genes. Because many polluted environments have been shown to contain elevated levels of antibiotic resistance genes, agriculturally-based pesticide bioremediation systems called 'biobeds' could serve as environmental reservoirs for antibiotic resistance genes, although this has never been extensively explored. Metagenomic and metatranscriptomic analyses of an on-farm biobed system sampled before and after a season of pesticide use demonstrated that in situ pesticide applications applied to biobeds can enrich for multidrug, sulfonamide, aminoglycoside, and beta-lactam resistance genes. Additionally, this study demonstrated an enrichment for genes associated with gene mobilization, such as genes involved in horizontal gene transfer and plasmid mobility, as well as transposons and integrases.

Multiresidue analysis of basic, neutral, and acidic pesticides in Biobeds’ biomixture

Contain between 1 and 3 bullet points highlighting the customization rather than the steps of the procedure.

An analytical methodology was adjusted and validated for the analysis of 15 selected pesticides currently employed in extensive agriculture. The main application of this methodology is studying the pesticides degradation behavior using biobeds as a friendly environmental tool for the treatment of wastewaters generated in fields. The scope of the method was selected based on the most used pesticides in soybean crops in Uruguay. The novelty of this work is the inclusion of neutral and acidic herbicides such as 2,4-D, clethodim, dicamba, together with fungicides and insecticides which are usually included in Multi Residue Methods. An acetonitrile extraction methodology without a clean-up step yielded acceptable results for all the analytes. The instrumental analysis was performed using HPLC-MS/MS. The selected methodology was validated according to the SANTE guidelines. The recoveries were between 65 and 130% with RSD < 20%. The instrumental LOQs were fixed at 1 µg/L for all the compounds except for clethodim, and the method LOQs were 1 mg/kg in biomixture dry basis. These LOQs values are acceptable for biodegradation studies in biobeds.

A multiresidue methodology was:

• Validated for 15 pesticides in biomixture.

• Acidic herbicides were included in the scope.

• The method was employed for the environmental monitoring of pesticide degradation in biobeds.

Biodegradation of pesticide-contaminated wastewaters from a formulation plant employing a pilot scale biobed

In this work, a pilot biobed was built up to treat pesticide-contaminated wastewaters discharged from a formulation plant. The pre-treated wastewater was spiked with additional pesticides in order to simulate a scenario of higher contamination: glyphosate, atrazine, imidacloprid, prometryn and carbendazim were added to reach a final Total Organic Carbon (TOC) concentration of 70 mg L^-1. An Intermediate Bulk Container (IBC) was filled with a biomixture of soil and foxtail millet stubble (50:50% v v^-1), and 200 l of the wastewater was added to the system recycling tank. The recirculation to the IBC was established for 12 h. After that (Day 0), the recirculation was turned on during the assay only to maintain the moisture for 180 days. Biomixture and wastewater samples were taken periodically to analyse pesticides and phytotoxicity in both matrices. In addition, hydrolytic and phenoloxidase activities, total bacteria and yeast and fungi communities were determined in the biomixture. The designed pilot scale biobed allowed to treat wastewaters with high concentration of pesticides reaching a complete removal of glyphosate, AMPA, atrazine, carbendazim and prometryn at 180 days. A good degradation percentage of the recalcitrant imidacloprid was achieved (60%) and the biomixture showed enough biological activity to continue treating additional wastewater. The root elongation index from the germination test showed low toxicity on day 180 both in biomixture and wastewater. The millet stubble resulted an appropriate lignocellulosic material to be used in biobeds to treat a wide variety of pesticides. The application of the seed germination test proved to be a low cost and simple tool to determine the end point of the process.

Highly Efficient Removal of Neonicotinoid Insecticides by Thioether-Based (Multivariate) Metal-Organic Frameworks

Circumventing the impact of agrochemicals on aquatic environments has become a necessity for health and ecological reasons. Herein, we report the use of a family of five eco-friendly water-stable isoreticular metal-organic frameworks (MOFs), prepared from amino acids, as adsorbents for the removal of neonicotinoid insecticides (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) from water. Among them, the three MOFs containing thioether-based residues show remarkable removal efficiency. In particular, the novel multivariate MOF {Sr^IICu^II₆[(S,S)-methox]_1.5[(S,S)-Mecysmox]_1.50(OH)₂(H₂O)}·36H₂O (5), featuring narrow functional channels decorated with both -CH₂SCH₃ and -CH₂CH₂SCH₃ thioalkyl chains-from l-methionine and l-methylcysteine amino acid-derived ligands, respectively-stands out and exhibits the higher removal efficiency, being capable to capture 100% of acetamiprid and thiacloprid in a single capture step under dynamic solid-phase extraction conditions-less than 30 s. Such unusual combination of outstanding efficiency, high stability in environmental conditions, and low-cost straightforward synthesis in 5 places this material among the most attractive adsorbents reported for the removal of this type of contaminants.

Pesticide treatment in biobed systems at microcosms level under critical moisture and temperature range using an Orthic Solonchaks soil from southeastern Mexico amended with corn husk as support

Agriculture effluents from cleaning and handling equipment used in pesticide applications can contaminate superficial and groundwater sources when not correctly disposed of. Biobeds using soil enriched with amendments represent a viable technology to control and minimize pesticide pollution of soil and water in farmlands. They are usually installed outdoors without protection, making them vulnerable to rain flooding, lack of moisture, drought, and intense heat or cold. Temperature (T) and moisture (M) of the biomixture are considered two of the most important physical factor affecting pesticide dissipation. This study aimed to evaluate the effect of T and M on the dissipation of five of the most used pesticides (carbofuran, atrazine, 2,4-D, diazinon, and glyphosate) in Yucatan State, Mexico. Three experiments using miniaturized biobeds considering optimal temperature and moisture (T of 30 ± 2 °C and 90% water holding capacity [WHC]) were performed. The optimal dissipation time and the effect of T, M variations, and volatilization was determined. The optimal dissipation time was over 14 days. Carbofuran was the least dissipated pesticide and glyphosate the most. The primary factor affecting pesticide dissipation was T (P < 0.05), reaching rates of dissipation of 99% at 45 °C. Variations of M in the biomixture were not significant on pesticide dissipation (P > 0.05). The white-rot fungi were observed; its presence was related to increments of T. Head Space analysis (at 45 °C) showed low pesticide volatilization (≤0.03%) for all pesticide used were quantified; water vapor condensation could reduce the pesticide volatilization for experimental conditions.

Substrate evaluation for biobeds in the degradation of ethylene bis-dithiocarbamate in wastewater from pesticide application in banana

The efficacy of biobeds was evaluated by testing three agricultural residues (sugarcane top, banana stem, and eucalyptus chip) as substrates for the degradation of ethylene bis-dithiocarbamate (EBDC) and ethylene thiourea (ETU) in wastewater from banana spraying. Acrylic columns with a capacity to treat 1 L/ea. of wastewater were used as experimental units. Each unit was filled with different proportions of the test substrate (30%, 50% and 70% v/v) and the difference in volume was made up of equal parts of sugar cane cachasse and Fluvisol soil. Subsequently, the units were contaminated with suspensions of 878 mgL^-1 of EBDC, and the dose was repeated periodically. The ETU concentration and leachate toxicity were evaluated every month for six months. The mixtures with 30% sugarcane top and 50% eucalyptus chip gave the best results, with leachable ETU concentrations down to a level protective of the environment, and toxicity down to background levels or nearly so. This was only found in mixtures with a high C:N ratio (20-25), thus, the effectiveness of the biobeds appears to be related to high lignolytic activity. .

Microbial Detoxification of Dimethoate and Methomyl Residues in Aqueous Media

The extensive and random application of major organic pollutants, mainly pesticides, threatens ecosystems and human health. The present study was conducted to isolate and identify microorganisms from some water resources contaminated with pesticides. We investigated the ability of the identified microbes to grow in water spiked with dimethoate and methomyl. We also evaluated the potential effect of the identified microbial isolates on dimethoate and methomyl biodegradation in water. In addition, the total detoxification of dimethoate and methomyl residues in water after treatment with the most effective microbial isolates was confirmed using toxicity tests and analyzing biochemical parameters and histopathological changes in the kidney and liver of treated rats. The microbial isolates were identified as Xanthomonas campestris pv. Translucens and Aspergillus fumigates. Results showed that X. campestris pv. Translucens and A. fumigatus grow in media supplemented with dimethoate and methomyl faster than in other media without both pesticides. About 97.8% and 91.2% of dimethoate and 95% and 87.8% of methomyl (initial concentration of both 5 mg L−1) were biodegraded within 32 days of incubation with X. campestris pv. Translucens and A. fumigatus, respectively. There was no remaining toxicity in rats treated with dimethoate- and methomyl-contaminated water with respect to biochemical parameters and histopathological changes. Collectively, the identified bacterial isolate showed high potential for the complete degradation of dimethoate and methomyl residues in water.

New analytical method for chlorpyrifos determination in biobeds constructed in Brazil: Development and validation

A quick and efficient method was optimized and validated to determine chlorpyrifos in biobeds using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Chlorpyrifos was extracted from the matrix with 30 mL of a mixture of acetone, phosphoric acid and water 98:1:1 (v/v/v). After homogenization, centrifugation and filtration, 125 µL of the extract was evaporated and reconstituted in 5 mL of methanol acidified with 0.1% acetic acid. Validation was performed by studying analytical curve linearity (r²), estimated instrument and method limits of detection and limits of quantification (LOD_i, LOD_m, LOQ_i and LOQ_m, respectively), accuracy, precision (expressed as relative standard deviation, RSD), and matrix effect. Accuracy and precision were determined from the amount of pesticide recovered from biobed blank samples (i.e. without pesticide residue) spiked with chlorpyrifos at three different concentrations (2, 10 and 50 mg kg^-1), with seven replicates at each concentration. For all three concentrations studied, the average recovery values obtained were between 96 and 115% with RSD values lower than 20%. The validated LOQ obtained was 2 mg kg^-1 (from recovery studies) and the matrix effect observed was lower than ±20%, which demonstrated that there was neither considerable suppression nor enhancement of the analyte signal. The biobed system efficiently degraded chlorpyrifos in both 1) simulation of accidental spillage and 2) application of diluted pesticide solution. In the latter case, all the values obtained at the final sampling time (14 months) were below the validated LOQ_m.

Leaching behaviour appraisal of eight persistent herbicides on a loam soil amended with different composted organic wastes using screening indices

The addition of organic wastes is a common agronomic practice in some Mediterranean regions to increase soil organic matter. In addition, they consume high amounts of agrochemicals. Hand-packed soil columns were used to evaluate the effect of three different composted organic soil amendments (agro-forestry, agro-industrial and animal manure) on the leachability of eight persistent herbicides. A new leaching index based on the amounts recovered from leachates and referred as Experimental Leaching Index (ELI) is proposed according to the mean annual precipitation in a specific place. This index is compared with others such as Groundwater Ubiquity Score (GUS), Relative Leaching Potential Index (RLPI) and Leachability Index (LIX), which only include degradation (DT₅₀) and sorption (K_OC) parameters. According to ELI, metribuzin is very mobile in all cases, while terbuthylazine, chlorotoluron and isoproturon present high leachability only in unamended soil reducing their leaching potential in amended soils. Aclonifen, oxyfluorfen, trifluralin and pendimethalin behave in all cases as immobile (non-leacher) compounds.

Bacterial ecotoxicity and shifts in bacterial communities associated with the removal of ibuprofen, diclofenac and triclosan in biopurification systems

The proliferation and possible adverse effects of emerging contaminants such as pharmaceutical and personal care products (PPCPs) in waters and the environment is a cause for increasing concern. We investigated the dissipation of three PPCPs: ibuprofen (IBP), diclofenac (DCF) and triclosan (TCS), separately and in mixtures, in the ppm range in biopurification system (BPS) microcosms, paying special attention to their effect on bacterial ecotoxicity, as well as bacterial community structure and composition. The results reveal that BPS microcosms efficiently dissipate IBP and DCF with 90% removed after 45 and 84 days of incubation, respectively. However, removal of TCS required a longer incubation period of 127 days for 90% removal. Furthermore, dissipation of the PPCPs was slower when a mixture of all three was applied to BPS microcosms. TCS had an initial negative effect on bacterial viability by a decrease of 34-43% as measured by live bacterial cell counts using LIVE/DEAD® microscopy; however, this effect was mitigated when the three PPCPs were present simultaneously. The bacterial communities in BPS microcosms were more affected by incubation time than by the PPCPs used. Nonetheless, the PPCPs differentially affected the composition and relative abundance of bacterial taxa. IBP and DCF initially increased bacterial diversity and richness, while exposure to TCS generally provoked an opposite effect without full recovery at the end of the incubation period. TCS, which negatively affected the relative abundance of Acidobacteria, Methylophilales, and Legionellales, had the largest impact on bacterial groups. Biomarker OTUs were identified in the BPS microcosms which were constrained to higher concentrations of the PPCPs and thus are likely to harbour degradation and/or detoxification mechanisms. This study reveals for the first time the effect of PPCPs on bacterial ecotoxicity and diversity in biopurification system microcosms and also facilitates the design of further applications of biomixtures to eliminate PPCPs.

Herbicides based on 2,4-D: its behavior in agricultural environments and microbial biodegradation aspects. A review

One of the main herbicides used in the agricultural environments is 2,4-dichlorophenoxyacetic acid (2,4-D). It is a synthetic plant hormone auxin employed in many crops including rice, wheat, sorghum, sugar cane, and corn to control wide leaf weeds. The indiscriminate use of pesticides can produce numerous damages to the environment. Therefore, this review has the objective to provide an overview on the main characteristics of the herbicides based on 2,4-D, mostly on the role of microorganisms in its degradation and its main degradation metabolite, 2,4- dichlorophenol (2,4-DCP). The remediation processes carried out by microorganisms are advantageous to avoid the pollution of the environment as well as to safeguard the population health.

Are there any risks of the disposal of pesticide effluents in soils? Biobed system meets ecotoxicology ensuring safety to soil fauna

The biobed is a purification system, which reduces soil pollution for receiving pesticide residues from handling and washing machinery in agricultural areas. The aims of this study were (1) to assess ecotoxicity effects over time to soil fauna, posed by Lorsban^® 480 BR (Chlorpyrifos) and Dithane^® NT (Mancozeb) residues when disposed of in a biobed system compared with two subtropical soils, and (2) to assess ecotoxicity effects over time to soil fauna simulating an accidental spillage with Lorsban^® 480 BR at the biobed. A semi-field experiment was conducted for 420 days in southern Brazil, testing continuous disposal of washing pulverization tanks in biobeds, Typic Haploperox or Typic Hapludults. In addition, different biobeds received a single dose (1 L) of Lorsban^® 480 BR to simulate an accidental spillage. Chronic ecotoxicity tests were performed using Folsomia candida, Eisenia andrei, and Enchytraeus crypticus in different sampling times for both experiments. F. candida was the most sensitive species. The biobed system was able to eliminate effects from residues of both pesticides over time in all species, which did not happen in both natural soils. In accidental spillage simulation, even 420 days after contamination, F. candida did not show reproduction. The biobeds can be a feasible alternative for the disposal and treatment residues of pesticides, also for handling and washing pesticides activities. The system was efficient in promoting degradation and reducing ecotoxicity effects posed by Lorsban^® 480 BR and Dithane^® NT for soil fauna. It is a safe alternative to avoid soil contamination.

Indigenous biobed to limit point source pollution of imidacloprid in tropical countries

Point pollution of pesticides originating from the washing of spraying machines could be controlled by biobed system and it is in use in temperate countries. The biobed system is yet to be established in tropical countries. An indigenous biobed system was prepared using local resources like rice straw, farm yard manures (FYM) and paddy field soil to suit the tropical climate. Lowermost 3 cm layer of the biobed system was filled with rice husk biochar to prevent leaching of pesticides from the system. This model system was tested with high doses of imidacloprid (178 mg/column), a commonly used pesticide against number of insect-pests in different crops, for its degradation. The bio-mix trapped a major part of the imidacloprid on the top most layer of the biobed column and only a very small part of imidacloprid recovered from the leachate. The biobed system could degrade 70.13% of applied imidacloprid within 15 days of the experiment and only 5.27% of the total pesticide recovered 90 days after incubation. Addition of biochar layer adsorbed imidacloprid from the outgoing leachate from the biobed column. Biomixture boosted microbial activity more particularly fungal population, which might be responsible for imidacloprid degradation. Microbial biomass carbon, and soil enzymes indicated faster dissipation of imidacloprid from the top layer of the biobed. This simple but efficient biobed system using local resources can fulfill the need of the small and marginal farmers of Asian countries for pesticide decontamination.

Bacteria amended clay biochar composite biobed system to treat agriculture runoff

An efficient adsorbent which can resolve the existing limitations of a biobed is of concern. In the present study, a composite is prepared by mixing and pyrolyzing clay and plant parts. This is finally converted to clay biochar composite with enhanced porosity and adsorption capacity. Composite consists of clay with sawdust or clay with powdered dry fruit of Acacia concinna. Among the different composites employed, clay/Acacia concinna (7.6/0.4) with higher structural stability was used as the biomix for biobed. The clay biochar composite (20%) bioaugmented with biosurfactant producing bacterial consortium was then mixed with sandy clay loam soil in a laboratory-scale biobed system. The study showed a COD removal of 95% and cypermethrin removal of 98%. Biodegradation of cypermethrin isomers in soil and clay biochar composite was observed. The study revealed that clay biochar composite amended with biosurfactant producing bacterial consortium is an efficient biomix for the biobed system.

Pesticide bioremediation in liquid media using a microbial consortium and bacteria-pure strains isolated from a biomixture used in agricultural areas

Microorganisms' role in pesticide degradation has been studied widely. Insitu treatments of effluents containing pesticides such as biological beds (biobeds) are efficient biological systems where biomixture (mixture of substrates) and microorganisms are the keys in pesticide treatment; however, microbial activity has been studied poorly, and its potential beyond biobeds has not been widely explored. In this study, the capacity of microbial consortium and bacteria-pure strains isolated from a biomixture (soil-straw; 1:1, v/v) used to treat agricultural effluents under real conditions were evaluated during a bioremediation process of five pesticides commonly used Yucatan Mexico. Atrazine, carbofuran, and glyphosate had the highest degradations (>90%) using the microbial consortium; 2,4-D and diazinon were the most persistent (DT50 = 8.64 and 6.63 days). From the 21 identified bacteria species in the microbial consortium, Pseudomonas nitroreducens was the most abundant (52%) according to identified sequences. For the pure strains evaluation 2,4-D (DT50 = 9.87 days), carbofuran (DT50 = 8.27 days), diazinon (DT50 = 8.80 days) and glyphosate (DT50 = 8.59 days) were less persistent in the presence of the mixed consortium (Ochrobactrum sp. DGG-1-3, Ochrobactrum sp. Ge-14, Ochrobactrum sp. B18 and Pseudomonas citronellolis strain ADA-23B). Time, pesticide, and strain type were significant (P < 0.05) in pesticide degradation, so this process is multifactorial. Microbial consortium and pure strains can be used to increase the biobed efficiency by inoculation, even in the remediation of soil contaminated by pesticides in agricultural areas.

Sub-Lethal Effects of Pesticides on the DNA of Soil Organisms as Early Ecotoxicological Biomarkers

This review describes the researches performed in the last years to assess the impact of pesticide sub-lethal doses on soil microorganisms and non-target organisms in agricultural soil ecosystems. The overview was developed through the careful description and a critical analysis of three methodologies based on culture-independent approaches involving DNA extraction and sequencing (denaturing gradient gel electrophoresis, DGGE; next-generation sequencing, NGS) to characterize the microbial population and DNA damage assessment (comet assay) to determine the effect on soil invertebrates. The examination of the related published articles showed a continuous improvement of the possibility to detect the detrimental effect of the pesticides on soil microorganisms and non-target organisms at sub-lethal doses, i.e., doses which have no lethal effect on the organisms. Considering the overall critical discussion on microbial soil monitoring in the function of pesticide treatments, we can confirm the usefulness of PCR-DGGE as a screening technique to assess the genetic diversity of microbial communities. Nowadays, DGGE remains a preliminary technique to highlight rapidly the main differences in microbial community composition, which is able to give further information if coupled with culture-dependent microbiological approaches, while thorough assessments must be gained by high-throughput techniques such as NGS. The comet assay represents an elective technique for assessing genotoxicity in environmental biomonitoring, being mature after decades of implementation and widely used worldwide for its direct, simple, and affordable implementation. Nonetheless, in order to promote the consistency and reliability of results, regulatory bodies should provide guidelines on the optimal use of this tool, strongly indicating the most reliable indicators of DNA damage. This review may help the European Regulation Authority in deriving new ecotoxicological endpoints to be included in the Registration Procedure of new pesticides.

Culture-Independent Analysis of Linuron-Mineralizing Microbiota and Functions in on-Farm Biopurification Systems via DNA-Stable Isotope Probing: Comparison with Enrichment Culture

Our understanding of the microorganisms involved in in situ biodegradation of xenobiotics, like pesticides, in natural and engineered environments is poor. On-farm biopurification systems (BPSs) treat farm-produced pesticide-contaminated wastewater to reduce surface water pollution. BPSs are a labor and cost-efficient technology but are still mainly operated as black box systems. We used DNA-stable isotope probing (DNA-SIP) and classical enrichment to be informed about the organisms responsible for in situ degradation of the phenylurea herbicide linuron in a BPS matrix. DNA-SIP identified Ramlibacter, Variovorax, and an unknown Comamonadaceae genus as the dominant linuron assimilators. While linuron-degrading Variovorax strains have been isolated repeatedly, Ramlibacter has never been associated before with linuron degradation. Genes and mobile genetic elements (MGEs) previously linked to linuron catabolism were enriched in the heavy DNA-SIP fractions, suggesting their involvement in in situ linuron assimilation. BPS material free cultivation of linuron degraders from the same BPS matrix resulted in a community dominated by Variovorax, while Ramlibacter was not observed. Our study provides evidence for the role of Variovorax in in situ linuron biodegradation in a BPS, alongside other organisms like Ramlibacter, and further shows that cultivation results in a biased representation of the in situ linuron-assimilating bacterial populations.

Microbial degradation of two highly persistent fluorinated fungicides - epoxiconazole and fludioxonil

Biodegradation of two highly persistent fluorinated fungicides, epoxiconazole (EPO) and fludioxonil (FLU), by microbial consortia enriched from estuarine sediment and agricultural soil is reported. After an enrichment period of 6 months, four microbial consortia were able to completely remove and defluorinate the fungicides in co-metabolic conditions. Defluorination was biologically mediated and results suggest it is not a primary catabolic step, as fungicide removal was always faster than its defluorination. Three of the four enriched consortia had similar biodegradation performances in the absence of a co-substrate. Biodegradation kinetics revealed that microbial degradation followed a first-order kinetics, with cultures being capable of biodegrading concentrations up to 10 mg L^-1 of EPO or FLU, in a maximum of 21 days. Estimated half-life values for these compounds were significantly lower than those reported in literature, highlighting the unique metabolic performance of the obtained consortia. Analysis of their microbial composition revealed that they integrate several bacterial species belonging to the Proteobacteria phylum, with the most common genera being Pseudomonas, Ochrobactrum and Comamonas. This is the first study providing clear evidence on the biodegradation of EPO and FLU, opening doors for the design of bioremediation technologies for the recovery of ecosystems polluted with such recalcitrant compounds.

Insights into the Function and Horizontal Transfer of Isoproturon Degradation Genes (pdmAB) in a Biobed System

Biobeds, designed to minimize pesticide point source contamination, rely mainly on biodegradation processes. We studied the interactions of a biobed microbial community with the herbicide isoproturon (IPU) to explore the role of the pdmA gene, encoding the large subunit of an N-demethylase responsible for the initial demethylation of IPU, via quantitative PCR (qPCR) and reverse transcription-PCR (RT-qPCR) and the effect of IPU on the diversity of the total bacterial community and its active fraction through amplicon sequencing of DNA and RNA, respectively. We further investigated the localization and dispersal mechanisms of pdmAB in the biobed packing material by measuring the abundance of the plasmid pSH (harboring pdmAB) of the IPU-degrading Sphingomonas sp. strain SH (previously isolated from the soil used in the biobed) compared with the abundance of the pdmA gene and metagenomic fosmid library screening. pdmA abundance and expression increased concomitantly with IPU mineralization, verifying its major role in IPU transformation in the biobed system. DNA- and RNA-based 16S rRNA gene sequencing analysis showed no effects on bacterial diversity. The pdmAB-harboring plasmid pSH showed a consistently lower abundance than pdmA, suggesting the localization of pdmAB in replicons other than pSH. Metagenomic analysis identified four pdmAB-carrying fosmids. In three of these fosmids, the pdmAB genes were organized in a well-conserved operon carried by sphingomonad plasmids with low synteny with pSH, while the fourth fosmid contained an incomplete pdmAB cassette localized in a genomic fragment of a Rhodanobacter strain. Further analysis suggested a potentially crucial role of IS6 and IS256 in the transposition and activation of the pdmAB operon.IMPORTANCE Our study provides novel insights into the interactions of IPU with the bacterial community of biobed systems, reinforces the assumption of a transposable nature of IPU-degrading genes, and verifies that on-farm biobed systems are hot spots for the evolution of pesticide catabolic traits.

Earthworms to improve glyphosate degradation in biobeds

In this work, earthworm effect on the efficiency of biobeds for glyphosate degradation was studied. Three biomixtures with and without the addition of earthworms (Eisenia fetida species) were evaluated. The initial concentration of glyphosate was 1000 mg/kg biomixture. Glyphosate and biological parameters were measured as a function of time. Earthworm survival, biomass, and reproduction were evaluated as well. All biomixtures that contain earthworms reached 90% of glyphosate degradation at 90 days in comparison with the biomixtures without earthworms that reached 80% approximately at the same time. Also, within the biomixtures that contained earthworms, glyphosate degradation rate was significantly higher in the one made up with soil and wheat stubble (Ws-E) showing excellent capacity for aminomethylphosphonic acid (AMPA) degradation, the main metabolite of glyphosate degradation. In addition, a study performed after the vermiremediation process showed that E. fetida can tolerate high glyphosate concentration without modifications in its life traits. It can be concluded that the use of E. fetida within the biobeds is an excellent combination to improve glyphosate and AMPA removal.

Pesticide-tolerant bacteria isolated from a biopurification system to remove commonly used pesticides to protect water resources

In this study, we selected and characterized different pesticide-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a pesticides mixture. The amplicon analysis of biomixture reported that the phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were predominant. Six strains grew in the presence of chlorpyrifos and iprodione. Biochemical characterization showed that all isolates were positive for esterase, acid phosphatase, among others, and they were identified as Pseudomonas, Rhodococcus and Achromobacter based on molecular and proteomic analysis. Bacterial growth decreased as both pesticide concentrations increased from 10 to 100 mg L^-1 in liquid culture. The Achromobacter sp. strain C1 showed the best chlorpyrifos removal rate of 0.072–0.147 d^-1 a half-life of 4.7–9.7 d and a maximum metabolite concentration of 2.10 mg L^-1 at 120 h. On the other hand, Pseudomonas sp. strain C9 showed the highest iprodione removal rate of 0.100–0.193 d^-1 a half-life of 4–7 d and maximum metabolite concentration of 0.95 mg L^-1 at 48 h. The Achromobacter and Pseudomonas strains showed a good potential as chlorpyrifos and iprodione-degrading bacteria.

Impaired pesticide removal and detoxification by biomixtures during the simulated pesticide application cycle of a tropical agricultural system

Biopurification systems (BPS) or biobeds have been developed to attenuate point-source contamination due to inappropriate pesticide handling or disposal of agricultural wastewaters. The biomixture used for this strategy should be able to remove different active ingredients but its efficiency can vary due to the constant load of pesticides from crop application programs. For that reason, the performance of biomixtures in conditions that mimic the real pesticide treatment before their implementation in field settings should be assayed. This study aimed to evaluate the removal and detoxifying capacity of a previously formulated biomixture (coconut fiber, 50% v/v; compost, 25%; and soil pre-exposed to pesticides, 25%) during a simulated cycle of pesticide application (93 days) for potato production. The scheme included a first application of linuron followed by a weekly alternated treatment of the mixtures chlorpyrifos/metalaxyl and malathion/dimethomorph, and antibiotics at day 72. The biomixture showed efficient removal of linuron (half-life <15 days), and a fluctuating transformation rate for the other compounds. A constant and sustained removal was observed for malathion and methalaxyl. In contrast, lower efficiency and accumulation was described for chlorpyrifos and dimethomorph. Following antibiotic treatment, changes on pesticide removal were observed only in the case of chlorpyrifos, whose removal was slightly enhanced. Furthermore, acute toxicity assays showed limited detoxification of the matrix, especially when compounds began to accumulate. Summarizing, our experiments showed that the proposed biomixture does not support a proper removal of the pesticides during the simulated application cycle of potato production. Further optimization of a biopurification system is required to guarantee the successful elimination of pesticide combinations when applied in field conditions.

Destination of pesticide residues on biobeds: State of the art and future perspectives in Latin America

Land-use intensification with a high demand for pesticides is a consequence of human population increase. Feasible alternatives for correct concentrated residues discharge are necessary to avoid soil and water resources contamination. Biobeds are in situ bioreactors for treating pesticide residues, used by several European and American countries due to its low cost and simple construction, whose efficiency has been scientifically proved for over 20 years. This review presents the state of the art of biobeds in Latin America (LA), identifying advances and future research needs. Factors affecting the efficiency of biobeds are discussed, like ideal temperature, moisture, and microbial communities, followed by methods for evaluating the bioreactor's efficiency. It was necessary to adapt this technology to the climatic and economic conditions of Latin-American countries, due to its European origins. Guatemala is the LA country that uses biobeds as official technology. Brazil, Argentina, Costa Rica and Chile are examples of countries that are actively investigating new substrates and pursuing legal aspects for the establishment of the biobeds. Robust scientific evidences may enable farmers start using this technology, which is an environmentally safe system to protect water resources.

Ecotoxicological test based on inhibition of fungal laccase activity: Application to agrochemicals and the monitoring of pesticide degradation processes

Ecotoxicological evaluations require the use of assays with several bioindicators from different trophic levels. Only a few ecotoxicological tests using fungi have been developed, reason why, detection of adverse effects from compounds that exert fungicide action may be overlooked. This work developed a toxicity test based on the inhibition of laccase enzymatic activity in the fungus Trametes versicolor. The test was applied to several fungicides and succeeded to determine inhibition values (half maximum effective concentration, EC₅₀) for most of them (flusilazole, imazalil, pyrimethanil, tetraconazole), though a clear dose-response was not evident for others (thiabendazole, metalaxyl). The application on atrazine (herbicide), imidacloprid (insecticide) and oxytetracycline (antibiotic), proved the proposed test is suitable towards other agrochemicals. The test was also used to estimate the detoxification resulting from two different approaches employed in the removal of agrochemicals. (a) First, in the liquid-phase elimination by fungal biomass simultaneously removing atrazine, imazalil, tebuconazole and triadimenol, the test showed a significant decrease in toxicity by biodegradation (adsorption contribution to detoxification was negligible). (b) Second, a solid-phase biomixture (used for pesticide degradation from agricultural wastewater) partially removed atrazine, imazalil, metalaxyl and pyrimethanil after 33 d; nonetheless, this system could not reduce the toxicity of the matrix, and higher laccase inhibition was detected after the treatment. The design test increases the battery of available bioassays to determine the toxicity of agrochemicals, and provides an interesting tool to monitor biodegradation processes.

Vermiremediation of Biomixtures from Biobed Systems Contaminated with Pesticides

Biobeds bioremediation systems are effectively used for minimizing pesticide point-source contamination. For keeping the biobed effectiveness, its biomixture needs to be replaced every so often. The exhausted biomixtures can contain pesticide residues and so they require a special treatment before being discharged into the environment. In this study, we explore the potential of vermiremediation for cleaning up biobed biomixtures contaminated with pesticides. Two biomixtures composed of soil:peat:straw (P) and soil:vermicompost of wet olive cake: olive tree pruning (O), contaminated with high loads of four pesticides, were used. Vermicomposting was carried out by Eisenia fetida earthworms for 12 weeks. Results showed that 50% and 70% of the earthworms colonized the contaminated P and O biomixtures, respectively, but the number of alive earthworms decreased with time just as their weight. The colonization of biomixtures did not significantly affect the dissipation of imidacloprid and tebuconazole, but increased 1.4 fold the dissipation of oxyfluorfen in both biomixtures and that of diuron in biomixture P. Although the presence of high loads of pesticides and the composition of the biomixtures limited the vermiremediation, satisfactory results were obtained for diuron and oxyfluorfen. Complementing vermiremediation with other remediation practices could improve the efficiency of this technology.

Simultaneous removal of neonicotinoid insecticides by a microbial degrading consortium: Detoxification at reactor scale

Neonicotinoid insecticides show high persistence in the environment, and standard biological approaches such as biopurification systems have shown mostly inefficient removal of such compounds. In this work, soil pre-exposed to imidacloprid was used to obtain presumptive imidacloprid-degrading consortia. Cometabolic enrichment yielded a microbial consortium composed of eight bacterial and one yeast strains, capable of degrading not only this compound, but also thiamethoxam and acetamiprid, as demonstrated in cross-degradation assays. The biological removal process was scaled-up to batch stirred tank bioreactors (STBR); this configuration was able to simultaneously remove mixtures of imidacloprid + thiamethoxam or imidacloprid + thiamethoxam + acetamiprid, reaching elimination of 95.8% and 94.4% of total neonicotinoids, respectively. Removal rates in the bioreactors followed the pattern imidacloprid > acetamiprid > thiamethoxam, including >99% elimination of imidacloprid in 6 d and 17 d (binary and ternary mixtures, respectively). A comprehensive evaluation of the detoxification in the STBR was performed using different biomarkers: seed germination (Lactuca sativa), bioluminescence inhibition (Vibrio fischeri), and acute oral tests in honeybees. Overall, ecotoxicological tests revealed partial detoxification of the matrix, with clearer detoxification patterns in the binary mixture. This biological approach represents a promising option for the removal of neonicotinoids from agricultural wastewater; however, optimization of the process should be performed before application in farms.

Efficiency of a low-cost pyramid-shaped solar still for pesticide removal from highly contaminated water

Water pollution by pesticides and other chemical contaminants is a subject of major importance due to the risk for human health and the environment. The search for remediation processes able to withdraw chemical contaminants from water and to allows water reuse is an urgent need. Herein, a simple and cheap system for pesticides removal was constructed and evaluated using water samples contaminated with two widely used herbicides (imazapic and imazethapyr, at g L^-1 level). Operation parameters and process efficiency, in terms of removal rate in the reclaimed water and degradation rate of pesticides in the dry residue, were quantitatively determined. The model was tested in real-world field experiments and was able to remove more than 99.95% of both contaminants from a 10 L solution containing 4.16 ± 0.94 g of imazethapyr and 1.31 ± 0.17 g of imazapic, generating reusable water with minimum volume loss (<2.5%). Liquid chromatography coupled to mass spectrometry was used to determine the herbicides content in all samples and to estimate the degree of degradation of the substances as well as the occurrence of transformation products of imazapic and imazethapyr. The system efficiency in removing contaminants of emerging concern from surface water was also evaluated. The process have generated output water with undetected levels for two fungicides present in a local river in Southern Brazil.

Effects of 2,4-D-based herbicide (DMA® 806) on sensitivity, respiration rates, energy reserves and behavior of tadpoles

Increased use of sugarcane pesticides and their destination to non-target environments in Brazil has generated concerns related to the conservation of more vulnerable groups, such as amphibians. Besides the high skin permeability, tadpoles are constantly restricted to small and ephemeral ponds, where exposure to high concentrations of pesticides in agricultural areas is inevitable. This study evaluated chronic effects caused by sub-lethal concentrations of 2,4-dichlorophenoxyacetic acid herbicide on energy storage, development, respiration rates, swimming performance and avoidance behavior of bullfrog tadpoles (Lithobates catesbeianus). Firstly, we conducted acute toxicity test (96 h) to estipulate sub-lethal concentrations of 2,4-D and evaluate the sensitivity of three tadpoles' species to this herbicide. Results showed that Leptodactylus fuscus presented the lowest LC₅₀ 96 h, 28.81 mg/L, followed by Physalaemus nattereri (143.08 mg/L) and L. catesbeianus (574.52 mg/L). Chronic exposure to 2,4-D (125, 250 and 500 μg/L) delayed metamorphosis and inhibited the growth of tadpoles at concentrations of 125 μg/L. Effects on biochemical reserves showed that 2,4-D increased total hepatic lipids in tadpoles, although some individual lipid classes (e.g. free fatty acids and triglycerides) were reduced. Protein and carbohydrates contents were also impaired by 2,4-D, suggesting a disruption on energy metabolism of amphibians by the herbicide. In addition to biochemical changes, respiration rates and swimming speed were also decreased after chronic exposure to 2,4-D, and these responses appeared to be correlated with the changes detected in the basic energy content. Avoidance test indicated that tadpoles of L. catesbeinus avoided the presence of 2,4-D, however they were unable to detect increasing gradients of the contaminant. Our data showed that chronic exposure to 2,4-D impaired biochemical, physiological and behavioral aspects of tadpoles, which may compromise their health and make them more vulnerable to environmental stressors in natural systems.

Expanding the use of biobeds: Degradation and adsorption of pesticides contained in effluents from seed-coating, bulb disinfestation and fruit-packaging activities

Agro-food industries that use pesticides constitute significant point sources for the contamination of natural water resources. Despite that, little is known about the treatment of their pesticide-contaminated effluents. Biobeds could be a possible solution for the depuration of these effluents. In this context, we explored the degradation and adsorption of pesticides used in seed-coating (carboxin (CBX), metalaxyl-M (MET-M), fluxapyroxad (FLX), fludioxonil (FLD)), bulb-dipping (chlorothalonil (CHT), thiabendazole (TBZ), FLD) and fruit-packaging activities (FLD) in a biomixture, used as biobed packing material, and in soil. The degradation of pesticides was tested individually and in mixtures relevant to their industrial use, while FLD was also tested at different concentrations (10, 20, and 150 mg kg^-1) representing its use in the different industries. CBX, FLD, and CHT, when applied individually, and all other pesticides when applied in mixtures, degraded more rapidly in biomixture than in soil. In most cases pesticides application in mixtures retarded their degradation. This was more pronounced in soil than in biomixture, especially for MET-M and FLD. CHT had the most prominent inhibitory effect on the degradation of TBZ and FLD. FLD degradation showed a dose-dependent pattern (DT₅₀ 42.4 days at 10 mg kg^-1 and 107.6 days at 150 mg kg^-1). All pesticides showed higher adsorption affinity in the biomixture (K_f = 3.23-123.3 g mL^-1) compared to soil (K_f = 1.15-31.2 g mL^-1). We provide initial evidence for the potential of the tested biomixture to remove pesticides contained in effluents produced by different agro-industrial activities. Tests in full-scale biobeds packed with this biomixture will unravel their full depuration potential for the treatment of these agro-industrial effluents.

Removal of triazines, triazoles and organophophates in biomixtures and application of a biopurification system for the treatment of laboratory wastewaters

Biopurification systems (BPS) have been barely explored for removing complex mixtures of pesticides. In this study, the potential of a biomixture to remove simultaneously a mixture of herbicides (triazines), fungicides (triazoles) and insecticides (organophosphates) is presented. Also, a BPS using the same biomixture was used for treating a pesticide testing laboratory wastewater containing a mixture of 38 compounds. Ecotoxicological assays were conducted on the BPS elutriates to investigate the mixture detoxification. A mixture (concentrations of 4-8 mg kg^-1) run in small-scale biomixture systems (SSB) for 128 d showed 59.3% removal of triazines, 68.5% of organophosphates and no elimination of triazoles. The treatment of the laboratory wastewater (individual concentrations range: 0.0036-0.25 mg kg^-1) in the pilot-scale BPS for 281 d resulted in the elimination pattern of organophosphates (90.0%) > triazoles (73.4%) > carbamates (71.3%) > triazines (54.3%). Complete detoxification towards Daphnia magna and partial detoxification in Lactuca sativa seeds germination occurred in the BPS. Although the pesticide mixture complexity is higher in the BPS, the lower concentrations found in this matrix, could explain removal differences between SSB and BPS and the apparent inhibition in the elimination of carbamates and some triazines observed in the latter. These findings suggest that disposal of pesticide-containing laboratory-wastewater should be done in separate containers, according to chemical groups before their treatment in separate BPS, in order to reduce treatment periods. Monitoring the treatment process in the BPS with a battery of ecotoxicological tests is strongly recommended.

Parameters affecting azoxystrobin and imidacloprid degradation in biobed substrates in the North Indian tropical environment

This study reports degradation of azoxystrobin (AZOXY) and imidacloprid (IMIDA) in the rice straw (RS)/corn cob (CC) and peat (P)/compost (C)-based biomixtures. The effect of biomixture preconditioning (10 days incubation prior to pesticide application), pesticide concentration and moisture content was evaluated. Results suggested that conditioning of biomixture greatly affected IMIDA degradation where half-life (t_1/2) was reduced by 5-9 times. This was attributed to higher microbial biomass carbon content and dehydrogenase activity in the conditioned biomixtures. Pesticide application in the conditioned biomixture did not show any negative impact on soil microbial parameters. Both pesticides degraded at faster rate in the rice straw-based biomixtures than in the corn cob-based biomixtures. Degradation slowed down with increase in initial concentration of pesticides in biomixture and 1.6-3.0 (AZOXY) and 2.4-3.6 (IMIDA) times increase in t_1/2 values was observed. The moisture content of biomixture showed positive effect on degradation which increased when moisture content was increased from 60 to 80% water holding capacity. The effect was significant for IMIDA degradation in the corn cob-based biomixtures and AZOXY degradation in the peat biomixtures. The rice straw-based biomixtures were better in degrading AZOXY and IMIDA and can be used in biopurification systems.

Removal of epoxiconazole and pyraclostrobin from highly contaminated effluent (grams per liter level): Comparison between ozone and solar still decontamination using real field conditions

Brazilian environmental legislation obliges the aeroagriculture operators to treat the effluents generated after aircraft washing. This effluent commonly contains high levels of pesticides (g L^-1) with potential to produce point source pollution. In the present study, we evaluated the efficiency of two systems on the removal of the fungicides epoxiconazole and pyraclostrobin from these effluents. The first system is based on ozonation and is currently suggested by regulatory authority. The second system is based on a pyramid-shaped solar still. The pesticides removal was monitored using liquid chromatography mass spectrometry to determine the mass quantity of both molecules throughout the treatment. After treatment with ozone treatment, the total mass of epoxiconazole decreased by 73% and pyraclostrobin decreased by 90.8%. The solar distillation system removed epoxiconazole and pyraclostrobin by >99.995 and 99.99%, respectively. The both systems proved to be efficient in the treatment of effluent containing residues of the fungicide Opera®, a formulation containing epoxiconazole and pyraclostrobin. The solar distillation system showed a higher degree of removal and presents the advantage of operating without energy sources, reagents or consumables.

Innovative application of biobed bioremediation systems to remove emerging contaminants: Adsorption, degradation and bioaccesibility

Biobed bioremediation systems (BBSs) are widely used to prevent point-source pesticide contamination of water. However, these systems have never been investigated for possible elimination of emerging contaminants (ECs). In this study, two biobed systems, involving biomixtures elaborated with soil and raw olive mill cake (SCP) or its vermicompost (SVP), were assayed to determine their effectiveness in removing the ECs diclofenac, ibuprofen and triclosan from effluent wastewater. Adsorption, incubation and bioaccesibility experiments were carried out. The SCP and SVP biomixtures showed greater adsorption capacity than the soil (S), used as reference. In SVP and S, the degradation rates of the ECs applied were similar and over 94% of these compounds was removed after 84 days of incubation. However, SCP biomixture had a lower removal rate and the percentage of ECs removed ranged from 32 to 68%. In SVP, the bioaccesible fraction (E) reveals that approximately 82% of triclosan and diclofenac adsorption occurred in bioaccesible sites, thus explaining the more efficient decontamination observed in this biomixture. The relationship established between the bioaccesible and biodegradable fractions suggests that E values are a useful tool for predicting the endpoints of ECs biodegradation in bioremediation systems. UPLC/Q-TOF-MS analysis of samples showed different metabolite products.

Glyphosate and aminomethylphosphonic acid degradation in biomixtures based on alfalfa straw, wheat stubble and river waste

The aim of the work was to evaluate novel biomixtures for their use on biopurification systems (BPS) in Argentina also called biobeds. Glyphosate and aminomethylphosphonic acid (AMPA) degradation was evaluated on biomixtures containing local materials: alfalfa straw (As), wheat stubble (Ws), river waste (Rw) and soil. Glyphosate, AMPA concentrations and biological activity were followed with time. Soil was used as control. Glyphosate initial concentration was 1000 mg kg-1. Glyphosate disappeared almost completely after 63 days in all tested biomixtures. For Ws, WsRw and AsRw glyphosate degradation was around 99% and for As 85%. The biomixture Ws showed the highest glyphosate degradation rate. In all cases AMPA was formed and degraded to concentrations between 60 and 100 mg kg-1. In the control with only soil, glyphosate was degraded 53% and AMPA concentration at the end of the test was 438 mg kg-1. We conclude that alfalfa straw, wheat stubble and river waste are local materials that can be used in the preparation of biomixtures since they showed higher glyphosate degradation capacity and less AMPA accumulation compared to the soil alone. Also, the presence of river waste did enhance the water retention capacity.

Kinetics and isotherm modeling of azoxystrobin and imidacloprid retention in biomixtures

The paper reports the kinetics and adsorption isotherm modeling for imidacloprid (IMIDA) and azoxystrobin (AZOXY) in rice straw (RS)/corn cob (CC) and peat (P)/compost (C) based biomixtures. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intraparticle diffusion models were used to describe the kinetics. The adsorption data were subjected to the Langmuir and the Freundlich isotherms. Results (r²_Adj values) suggested that the modified Elovich model was the best suited to explain the kinetics of IMIDA sorption while different models explained AZOXY sorption kinetics in different biomixtures (PFO in RS + C and RS + P; PSO in CC + P and Elovich in CC + C). Biomixtures varied in their capacity to adsorb both pesticides and the adsorption coefficient (K_d) values were 116.8-369.24 (AZOXY) and 24.2-293.4 (IMIDA). The Freundlich isotherm better explained the sorption of both pesticides. Comparison analysis of linear and nonlinear method for estimating the Freundlich adsorption constants was made. In general, r²_Adj values were higher for the nonlinear fit (AZOXY = 0.938-0.982; IMIDA = 0.91-0.970) than the linear fit (AZOXY = 0.886-0.993; IMIDA = 0.870-0.974) suggesting that the nonlinear Freundlich equation better explained the sorption. The rice straw-based biomixtures performed better in adsorbing both the pesticides and can be used in bio-purification systems.

Earthworms to assess the innocuousness of spent biomixtures employed for glyphosate degradation

In this study, the innocuousness of different biomixtures employed for glyphosate degradation was tested through Eisenia fetida earthworms. Eight biomixtures were prepared with local materials: alfalfa straw (AS), wheat stubble (WS), river waste (RW) and two different soils (A and B). Each biomixture was divided into two equal portions: one without glyphosate application (control substrate) and the other was sprayed with a commercial glyphosate formulation of 1,000 mg glyphosate a.i. kg-1 biomixture (applied substrate). The bioassay started when all sprayed biomixtures reached high percentages of glyphosate degradation (spent biomixtures). Three parameters were studied: survival, adults and juveniles biomass and reproduction. The results allowed the identification of three biomixtures (AWS, BWS and BWSRW) for good maintenance and development of E. fetida. In addition, at the end of the bioassay two of the viable biomixtures (AWS and BWS) showed the highest performance of juvenile earthworms compared to a reference soil. The Principal Component Analysis (PCA) indicated that the biomixtures containing high silt and clay percentages and minor density renders higher values of earthworm growth and reproduction. Therefore, these innocuous biomixtures can be used as organic amendments or recycled materials for new treatments on biobeds.

Organophosphorus pesticide mixture removal from environmental matrices by a soil Streptomyces mixed culture

The current study aimed to evaluate the removal of a pesticide mixture composed of the insecticides chlorpyrifos (CP) and diazinon (DZ) from liquid medium, soil and a biobed biomixture by a Streptomyces mixed culture. Liquid medium contaminated with 100 mg L^-1 CP plus DZ was inoculated with the Streptomyces mixed culture. Results indicated that microorganisms increased their biomass and that the inoculum was viable. The inoculum was able to remove the pesticide mixture with a removal rate of 0.036 and 0.015 h^-1 and a half-life of 19 and 46 h^-1 for CP and DZ, respectively. The sterilized soil and biobed biomixture inoculated with the mixed culture showed that Streptomyces was able to colonize the substrates, exhibiting an increase in population determined by quantitative polymerase chain reaction (q-PCR), enzymatic activity dehydrogenase (DHA) and acid phosphatase (APP). In both the soil and biomixture, limited CP removal was observed (6-14%), while DZ exhibited a removal rate of 0.024 and 0.060 day^-1 and a half-life of 29 and 11 days, respectively. Removal of the organophosphorus pesticide (OP) mixture composed of CP and DZ from different environmental matrices by Streptomyces spp. is reported here for the first time. The decontamination strategy using a Streptomyces mixed culture could represent a promising alternative to eliminate CP and DZ residues from liquids as well as to eliminate DZ from soil and biobed biomixtures.

Novel insights in biopurification system for dissipation of a pesticide mixture in repeated applications

A biopurification system based on the adsorption and degradation capacity of a biomixture to degrade a mixture of pesticides (atrazine, chlorpyrifos, iprodione; 50 mg kg^-1 each) in repeated applications (0, 30, and 60 days) was evaluated. Tanks of 1 m³ packed with a biomixture (ρ 0.29 g mL^-1) with and without vegetal cover were used. The biomixture contained soil, peat, and wheat straw in a proportion 1:1:2 by volume, respectively. Pesticide concentrations, biological activities (urease, phenoloxidase, and dehydrogenase), and microbial community changes (DGGE and qPCR) were evaluated periodically. Pesticide dissipation was higher in tanks with vegetal cover (> 95%) and no variation was observed after the three applications; contrarily, pesticide dissipation decreased in the tank without vegetal cover after each application. The presence of vegetal cover decreased the half-life of pesticides by at least twice. Biological activities were in general not affected by the application and reapplication of pesticides in the same treatment; however, they exhibited some differences between tanks containing and lacking the vegetal cover. High similarity between microbial groups (actinobacteria, bacteria, and fungi) was observed, suggesting no influence ascribable to the successive pesticide applications. The number of copies of bacteria and actinobacteria remained almost constant during the assay. However, the number of copies of fungi was significantly higher in the uncontaminated tank without vegetal cover.