Bioinformatics analysis of the potential mechanisms of Alzheimer's disease induced by exposure to combined triazine herbicides.

BACKGROUND: The development of Alzheimer's disease (AD) is promoted by a combination of genetic and environmental factors. Notably, combined exposure to triazine herbicides atrazine (ATR), simazine (SIM), and propazine (PRO) may promote the development of AD, but the mechanism is unknown. AIM: To study the molecular mechanism of AD induced by triazine herbicides. METHODS: Differentially expressed genes (DEGs) of AD patients and controls were identified. The intersectional targets of ATR, SIM, and PRO for possible associations with AD were screened through network pharmacology and used for gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis. The binding potentials between the core targets and herbicides were validated by molecular docking and molecular dynamics. RESULTS: A total of 1,062 DEGs were screened between the AD patients and controls, which identified 148 intersectional targets of herbicides causing AD that were screened by network pharmacology analysis. GO and KEGG enrichment analysis revealed that cell cycling and cellular senescence were important signalling pathways. Finally, the core targets EGFR, FN1, and TYMS were screened and validated by molecular docking and molecular dynamics. CONCLUSION: Our results suggest that combined exposure to triazine herbicides might promote the development of AD, thereby providing new insights for the prevention of AD.

National Assessment of Long-Term Groundwater Response to Pesticide Regulation.

Quantitative assessments of long-term, national-scale responses of groundwater quality to pesticide applications are essential to evaluate the effectiveness of pesticide regulations. Retardation time in the unsaturated zone (Ru) was estimated for selected herbicides (atrazine, simazine, and bentazon) and degradation products (desethylatrazine (DEA), desisopropylatrazine (DIA), desethyldesisopropylatrazine (DEIA), and BAM) using a multidecadal time series of groundwater solute chemistry (∼30 years) and herbicide sales (∼60 years). The sampling year was converted to recharge year using groundwater age. Then, Ru was estimated using a cross-correlation analysis of the sales and the frequencies of detection and exceedance of the drinking water standard (0.1 µg/L) of each selected compound. The results showed no retardation of the highly polar, thus mobile, parent compounds (i.e., bentazon), while Ru of the moderately polar compounds (i.e., simazine) was about a decade, and their degradation products showed even longer Ru. The temporal trends of the degradation products did not mirror those of the sale data, which were attributed to the various sale periods of the parent compounds, sorption of the parent compounds, and complex degradation pathways. The longer Ru in clayey/organic sediments than in sandy sediments further confirmed the role of soil-specific retardation as an important factor to consider in groundwater protection.

Combination of microwave-assisted solvent extraction and effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction and its application in the extraction of triazine pesticides from apple samples.

In the current study, a combination of microwave-assisted solvent extraction combined with effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction has been developed as a new sample pretreatment method. The offered method was used for the extraction of five triazine pesticides (atrazine, propazine, cyanazine, ametryn, and simazine) from apple samples before their determination by gas chromatography-flame ionization detection. For this purpose, briefly, the apple sample was contacted with a suitable acidified extraction solvent and the mixture was exposed to microwave irradiations. Then, the supernatant was taken and mixed with a few microliters of a low-density deep eutectic solvent. The supernatant phase containing the extracted analytes was injected into a sodium bicarbonate solution filled into a syringe. Consequently, the effervescence reaction occurs and the analytes were extracted into the fine droplets of extractant dispersed throughout the solution. Afterward, an aliquot of this phase was analyzed by the chromatographic system. Satisfactory outcomes include high enrichment factors (228-261) and extraction recoveries (67-87%), good repeatability (relative standard deviations equal to or less than 3.2% and 5.3% for intra- and inter-day precisions), and low limits of detection (0.4-0.7 ng/g) and quantification (1.4-2.3 ng/g) were acquired under the best experimental situations.

Isolation of 2 simazine-degrading bacteria and development of a microbial agent for bioremediation of simazine pollution.

Simazine was one of the most commonly used herbicides and was widely used to control broadleaf weeds in agriculture and forestry. Its widespread use had caused wide public concern for its high ecological toxicity. In order to remove simazine residues, 2 strains capable of effectively degrading simazine were isolated from the soil and named SIMA-N5 and SIMA-N9. SIMA-N5 was identified as Bacillus licheniformis by 16SrRNA sequence analysis, and SIMA-N9 was Bacillus altitudinis. According to the degradation ratio of simazine in a certain period of time, the degradation ability of different strains was evaluated. The degradation efficiency of simazine (5 mg/L) by SIMA-N9 could reach about 98% in 5d, and the strain SIMA-N5 could reach 94% under the same conditions. In addition, the addition of Pennisetum rhizosphere soil during the process of degrading simazine by strain SIMA-N9 could effectively improve the degradation efficiency. The strain SIMA-N9 has been developed as a microbial agent for the bioremediation of simazine contamination in soil. The new microbial agent developed by using SIMA-N9 has achieved satisfactory application effects. Based on the research results already obtained in this study, it was considered that strain SIMA-N9 and its live bacterial agent could play an important role in bioremediation of simazine pollution. This study could not only provide a set of solutions to the simazine pollution, but also provide a reference for the treatment of other pesticide pollution.

Simultaneous determination of simazine, cyanazine, and atrazine in honey samples by dispersive liquid-liquid microextraction combined with high-performance liquid chromatography.

A rapid and simple sample preparation method was developed for simultaneous determination of three triazine herbicides in honey samples. The selected herbicides were extracted from honey samples by ionic liquid dispersive liquid-liquid microextraction, separated on a C18 column (250 mm × 4.6 mm id, 5 µm) using acetonitrile and H2 O as the mobile phase with gradient elution, and then detected by high-performance liquid chromatography. The parameters, such as the type and volume of the extraction and disperser solvent, ion strength, pH, extraction time, and centrifuge time were optimized in order to provide the excellent extraction performance. Good linearity was showed for all the target herbicides over the tested concentration range with correlation coefficient higher than 0.994. Three spiked levels (0.005, 0.05, 0.10 mg/kg) were applied for determination of the recoveries of the targets in honey samples in the range of 80-103% with relative standard deviations not larger than 10.6%. The limits of quantification for the analytes ranged between 1.5 and 4.0 µg/kg. The developed method was applied for determination of the target compounds residues in real samples.

Synthesis of Isotopically Labeled (13)C3-Simazine and Development of a Simultaneous UPLC-MS/MS Method for the Analysis of Simazine in Soil.

The isotope dilution mass spectrometry (IDMS) is a highly efficient method for tackling the ion suppression in complex matrix by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), but a lack of commercial internal standards is a limiting factor for these analyses. Herein, an economical and efficient strategy for the synthesis of (13)C3-simazine via a three-step procedure was developed. The isotope-labeled internal standard was used for determination of simazine residue in soil samples. The quantitation method has a limit of detection of 0.015 µg/kg and quantitation of 0.08 µg/kg. The inter-day and intra-day precision of the method were below 4.6%. Recovery values were ranged between 92.9% and 99.2%. All the samples obtained from six provinces in China contained from 1 to 62 µg/kg of simazine.

Estimated Levels of Environmental Contamination and Health Risk Assessment for Herbicides and Insecticides in Surface Water of Ceará, Brazil.

Methodology using solid phase extraction and high performance liquid chromatography (SPE-C18/HPLC-DAD) was applied to pesticide determinations in ten water reservoirs in the semidarid region of northeastern Brazil. The validated method was suitable for determination of herbicides and insecticide in surface water. The recovery efficiency of atrazine, methyl-parathion and simazine was approximately 70%. The method also showed good linearity and selectivity with correlation coefficients (R) greater than 0.99. The limits of detection were below the maximum residue limits (MRLs) established by government agencies. Studied reservoirs showed presence of atrazine at mean levels from 7.0 to 15.0 µg/L. Simazine and methyl parathion were not detected during the period. The atrazine levels measured from this semiarid region are of the same magnitude as those found in regions with moderate to high agricultural activity. According to detected atrazine concentrations, the annual health risk to humans was insignificant. However, the control of herbicides is important to maintain the quality of water in the reservoirs of Ceará, Brazil.

Microchip capillary electrophoresis based electroanalysis of triazine herbicides.

The number of pesticides used in agriculture is increasing steadily, leading to contamination of soil and drinking water. Herein, we present a microfluidic platform to detect the extent of contamination in soil samples. A microchip capillary electrophoresis system with in-channel electrodes was fabricated for label-free electroanalytical detection of triazine herbicides. The sample mixture contained three representative triazines: simazine, atrazine and ametryn. The electropherogram for each individual injection of simazine, atrazine and ametryn showed peaks at 58, 66 and 72 s whereas a mixture of them showed distinct peaks at 59, 67 and 71 s respectively. The technique as such may prove to be a useful qualitative and quantitative tool for the similar environmental pollutants.

Simultaneous voltammetric determination of four triazine herbicides in water samples with the aid of chemometrics.

A novel differential pulse voltammetry (DPV) method was developed for the simultaneous analysis of herbicides in water. A mixture of four herbicides, atrazine, simazine, propazine and terbuthylazine was analyzed simultaneously and the complex, overlapping DPV voltammograms were resolved by several chemometrics methods such as partial least squares (PLS), principal component regression (PCR) and principal component-artificial networks (PC-ANN). The complex profiles of the voltammograms collected from a synthetic set of samples were best resolved with the use of the PC-ANN method, and the best predictions of the concentrations of the analytes were obtained with the PC-ANN model (%RPET = 6.1 and average %Recovery = 99.0). The new method was also used for analysis of real samples, and the obtained results were compared well with those from the GC-MS technique. Such conclusions suggest that the novel method is a viable alternative to the other commonly used methods such as GC, HPLC and GC-MS.

Effect of ammonium on liquid- and gas-phase protonation and deprotonation in electrospray ionization mass spectrometry.

The electrospray ionization (ESI) is a complex process and there has been a long debate regarding the gas-phase effect on ion generation in the process. In this paper we investigated the effect of liquid chromatographic mobile phase additives (formic acid, aqueous ammonia and their combination) on the ESI signal intensities for a wide variety of compounds. The addition of a trace amount of aqueous ammonia to the common formic acid-methanol mobile phase significantly enhances the ESI signals of protonated molecules and suppresses the formation of sodium adduct ions. This effect is well observed for the compounds containing the -N-C=O group but not for those without N or O atoms. The ESI signal intensity of deprotonated molecules increases with increase in pH of the mobile phase for neutral compounds, such as substituted urea, whereas this trend is not observed for acidic compounds such as phenoxy acids. The mechanistic analysis regarding liquid- and gas-phase protonation and deprotonation is discussed.

Simazine transport in undisturbed soils from a vineyard at the Casablanca valley, Chile.

Simazine is a soil-active herbicide that has been applied worldwide in agricultural soils, being the second most commonly detected herbicide in groundwater and surface waters. Although its use has been restricted in many countries of Europe, it is still applied in many locations around the world in orchards, vineyards and forestry. Therefore, it is important to study its fate and transport in the environment. This paper investigates simazine transport in undisturbed bare soils from a vineyard at the Casablanca valley, Chile. In the study site, shallow groundwater tables (<1.0 m depth) and high simazine levels (>15 µg L(-1)) in the groundwater were observed and thus, there is potential for simazine to be transported further away through the saturated zone. The soils from the study site were characterized and the hydrodynamic transport parameters were determined. Column leaching experiments showed that the two-site chemical non-equilibrium model correctly represented simazine transport. It was found that 36.3% of the adsorption sites achieve instantaneous equilibrium and that the first-order kinetic rate of the non-equilibrium sites was 6.2 × 10(-3) h(-1). Hydrus 2D was used to predict the transport of simazine in the study site under natural field conditions. Simulation results showed that simazine concentrations at depths shallower than 2.1 m are above the maximum contaminant level of 4 µg L(-1) (defined by the U.S. Environmental Protection Agency). The timing of herbicide application was found to be important on simazine leaching and the main processes involved in simazine transport were degradation and adsorption, which accounted for 95.78 and 4.19% of the simulated mass of pesticide, respectively. A qualitative agreement in the timing and magnitude of simazine concentration was obtained between the simulations and the field data. Therefore, the model utilized in this investigation can be used to predict simazine transport and is a valuable tool to assess agricultural practices to minimize environmental impacts of simazine.

Transition metal-doped germanium oxide nanozyme with enhanced enzyme-like activity for rapid detection of pesticide residues in water samples.

Designing highly active nanozymes for bioanalysis and environmental sensing remains a challenge. In this study, transition metal, palladium (Pd) and iron (Fe), doped germanium oxide (GeO2) nanozyme was designed and optimized. Compared with the pristine GeO2 nanozyme, the transition metal doped GeO2 nanozyme have lower Michaelis-Menten constants and higher catalytic activity, indicating that the Pd and Fe doped GeO2 nanozyme not only enhance their affinity for the substrate but also improve its catalytic activity. In addition, a colorimetric sensor based on the GeO2@Pd-H2O2-TMB system was constructed for the visual detection of simazine in water samples due to the good affinity between TMB and simazine. This sensor has good selectivity and sensitivity with a detection limit of 6.21 µM because of the highest catalytic performance of GeO2@Pd nanozyme. This study broadens the application of nanozymes in environmental field and other nanozymes can also be enhanced in activity by simple transition metal doping.

Catchment sourcing urban pesticide pollution using constructed wetlands in Melbourne, Australia.

A survey of 111 urban constructed stormwater wetlands (median watershed area = 86.8 ha) was conducted to identify the major pesticides present and to determine their major catchment sources (residential, industrial, commercial, sporting ovals) and associations with catchment imperviousness. Melbourne, Australia, has separate stormwater and sewerage systems and these wetlands are designed to treat urban stormwater. To maximise the pesticides that could be detected, three types of passive samplers (POCIS, Chemcatcher® SDB-XC and Chemcatcher® C18) were deployed, along with collection of fine sediments. A total of 231 pesticides were screened using these methods. Pesticides that were detected in >5 % of wetlands were checked to determine their registered use in urban areas using an Australian government database (PubCris). Twenty-five pesticides were detected in >5 % of wetlands: 4 pesticides were associated with non-urban land uses (agriculture and forests), another 4 pesticides had no known registered use in urban areas and 17 were associated with urban areas. The pesticides associated with urban areas were the herbicides simazine, diuron, metolachlor, bromacil, propyzamide and paclobutrazol, the fungicides tebuconazole, propiconazole, metalaxyl, trifloxystrobin, iprodione and carbendazim and the insecticides fipronil, bifenthrin, chlorantraniliprole, thiamethoxam and permethrin. Atrazine was also detected in 59 % of wetlands but has not been registered for urban uses in Australia since 2010. It's presence in Melbourne may be due to legacy issues or aerial transportation from rural areas where it's still widely used in crop cultivation. Generally, the major urban catchment source of pesticides is from residential areas (particularly fipronil and simazine), most likely in wood preservatives, paints and from weed or insect control. Many of these widely used pesticides were correlated with increased catchment imperviousness. Some pesticides (bromacil and imidacloprid) were correlated with commercial premises and chlorantraniliprole was correlated with the presence of sporting ovals in the catchment. No pesticides were specifically correlated with industrial areas. The use of passive samplers and fine sediments, in conjunction with detailed land use mapping of stormwater wetland catchments is very effective and efficient in monitoring and sourcing pesticide contamination in urban environments.

Effects of long-term exposure to simazine in real concentrations on common carp (Cyprinus carpio L.).

The effects of a 90 day simazine exposure at concentrations of 0.06 (reported concentration in Czech rivers), 1, 2, and 4 µg L⁻¹ were assessed in one-year-old common carp (Cyprinus carpio L.). Its influence on biometric parameters, hematology, blood biochemistry, liver biomarkers, and histology was investigated. Biometric parameters of common carp exposed to simazine at 0.06 µg L⁻¹ showed no differences from untreated fish. Simazine concentrations of 1, 2, and 4 µg L⁻¹ caused significant (p<0.01) increase of hepatosomatic indices relative to controls. Hematological profiles showed significant (p<0.01) decrease in leukocyte count relative to controls at all concentrations. Biochemical profiles of common carp exposed to simazine at all concentrations showed significant (p<0.01) increase in activity of alkaline phosphatase. In addition, at concentrations of 1 and 2 µg L⁻¹, there was a significant increase in alanine aminotransferase (p<0.05), and, at 4 µg L⁻¹, a significant increase in total protein (p<0.05), albumins (p<0.05), and alanine aminotransferase (p<0.05) compared with controls. Renal histology revealed severe hyaline degeneration of the epithelial cells of caudal kidney tubules in fish at all exposure levels compared to controls. Chronic exposure of common carp to simazine caused significant shifts in hematological, biochemical, and biometric profiles, and histopathological changes. The results of this study indicate that chronic exposure of simazine has altered multiple physiological indices in fish hematology and biochemistry, which potentially may be a biomarker of simazine toxicity; however, before these parameters are used as special biomarkers for monitoring residual simazine in aquatic environment, more detailed experiments in laboratory need to be performed in the future.

Household herbicide use as a source of simazine contamination in urban surface waters.

Contamination of urban surface waters by herbicides is an increasing concern; however, sources of contamination are poorly understood, hindering the development of mitigation and regulatory strategies. Impervious surfaces, such as concrete in driveways and paths are considered an important facilitator for herbicide runoff to urban surface waters following applications by residential homeowners. This study assessed the transferability of a herbicide from concrete pavers treated with an off-the-shelf product, containing simazine as the active herbicide, marketed for residential homeowner application to impervious surfaces. Commercially available pavers were treated according to label directions and the effects of exposure time prior to irrigation, repeated irrigations, and dry time between irrigations on transferability of simazine to runoff were assessed. Simazine transferability was greatest when receiving an initial irrigation 1 h after application, with concentrations in runoff reduced by half when exposure times prior to the first irrigation were >2 days. Concentrations remained stable for repeated irrigations up to 320 days and exposures to outdoor conditions of 180 days prior to a first irrigation. Dry time between irrigations significantly influenced simazine transfer to runoff. Dry periods of 140 days resulted in approximately a 4-times increase in simazine transferability to runoff. These results suggest that herbicides used by homeowners, or any other users, on impervious surfaces are available to contaminate runoff for prolonged time periods following application at concentrations that may pose risks to aquatic life and for reuse of harvested runoff on parks and gardens. Regulators should consider the potential of hard surfaces to act as reservoirs for herbicides when developing policies and labelling products.

Unraveling the occurrence of contaminants of emerging concern in groundwater from urban setting: A combined multidisciplinary approach and self-organizing maps.

In recent decades, changes in human behavior and new technologies have introduced thousands of new compounds into the environment called "contaminants of emerging concern" (CEC). These compounds have been detected in different environmental compartments such as soil, surface water, air, and groundwater. The presence of these contaminants in groundwater may pose risks to human health when used as potable water. In some urban areas in Brazil, groundwater is normally consumed without previous treatment. This study aimed to use statistical analysis by self-organizing maps (SOM) to evaluate the trends of CEC in urban groundwater systems. A total of 23 CEC compounds including pesticides, pharmaceuticals, and hormones were determined in groundwater samples using solid phase extraction and liquid chromatography-mass spectrometry. The CEC most frequently detected were atrazine and degradation products, fipronil, simazine, tebuconazole, hexazinone, and caffeine in concentrations up to 300 ng L-1. All studied compounds were detected in groundwater at least in one sample. Patterns in the data through SOM have shown a strong positive correlation between atrazine, hexazinone, simazine, tebuthiuron, 2-hydroxyatrazine, and 17ß-estradiol. The hormones estrone and testosterone also show a positive correlation due to their similar chemical properties. On the other hand, caffeine was detected in 90% of the samples, likely due to a population habit of taking daily a hot drink made of yerba mate associated with low rates of treated domestic sewage in the study area.

Surface water contamination from pesticide mixtures and risks to aquatic life in a high-input agricultural region of Brazil.

The environmental risks of pesticides found in surface waters of an important agricultural basin in Brazil were estimated by adopting two approaches: individual pesticides risk quotients (RQ) and concentration addition model for pesticide mixtures (∑RQs) contained in each water sample. Monitoring was carried out in the Mogi Guaçu River basin, Brazil, from October 2017 to May 2018. Four sampling points were selected in the Mogi Guaçu River and seven in its tributaries A multiresidue method with solid-phase extraction and subsequent analysis by UPLC-ESI-QqQ-MS/MS was developed to quantify 19 pesticides. Herbicides, except for simazine, presented the highest detection frequencies with values above 70%. Tebuthiuron was found in all 55 analyzed samples, presenting the highest concentration (6437 ng L-1) over the monitoring period. Fungicides and insecticides showed similar detection frequency (DF) values, ranging from 1.8% to 21.8%. Tebuconazole and carbofuran were the fungicides and insecticides most frequently detected, respectively. January 2018 sampling showed the highest total concentration of pesticides, differing from March 2018 and May 2018 (p < 0.05). The MG2 > TMG8 > MG1 > TMG6 sites showed the highest concentration total of pesticides while MG4 > TMG4 > TMG3 (p < 0.05) sites showed the lowest values: MG4 > TMG4 > TMG3 (p < 0.05). Most pesticide occurrences presented no risks to aquatic organisms. Only 19 out of the 175 pesticide occurrences > LOQ presented individual risks to aquatic biota. Contrary to the results obtained by the individual risk assessment, most pesticide mixtures presented risks to aquatic biota. In 36 out of the 55 samples analyzed during monitoring, pesticide mixtures presented risks to aquatic life.

Liquid extraction surface analysis (LESA) of food surfaces employing chip-based nano-electrospray mass spectrometry.

An automated surface-sampling technique called liquid extraction surface analysis (LESA), coupled with infusion nano-electrospray high-resolution mass spectrometry and tandem mass spectrometry (MS/MS), is described and applied to the qualitative determination of surface chemical residues resulting from the artificial spraying of selected fresh fruits and vegetables with representative pesticides. Each of the targeted pesticides was readily detected with both high-resolution and full-scan collision-induced dissociation (CID) mass spectra. In the case of simazine and sevin, a mass resolution of 100,000 was insufficient to distinguish the isobaric protonated molecules for these compounds. When the surface of a spinach leaf was analyzed by LESA, trace levels of diazinon were readily detected on the spinach purchased directly from a supermarket before they were sprayed with the five-pesticide mixture. A 30 s rinse under hot running tap water appeared to quantitatively remove all remaining residues of this pesticide. Diazinon was readily detected by LESA analysis on the skin of the artificially sprayed spinach. Finally, incurred pyrimethanil at a level of 169 ppb in a batch slurry of homogenized apples was analyzed by LESA and this pesticide was readily detected by both high-resolution mass spectrometry and full-scan CID mass spectrometry, thus showing that pesticides may also be detected in whole fruit homogenized samples. This report shows that representative pesticides on fruit and vegetable surfaces present at levels 20-fold below generally allowed EPA tolerance levels are readily detected and confirmed by the title technologies making LESA-MS as interesting screening method for food safety purposes.

Norflurazon and simazine removal from surface water using a constructed wetland.

Norflurazon and simazine are pre-emergent herbicides detected frequently in surface water associated with South Florida agricultural canals and drainage water. This study investigated the potential use of a 1.34 ha constructed wetland for removing these herbicides from surface water. The total length of the wetland was 400 m and width was 35 m. A surface water flow rate of 740 L/min was maintained in the system using a pump. The plant community within the system consisted primarily of Panicum repens, Alternanthera philoxeroides, and Bacopa caroliniana. Norflurazon and simazine, derived from commercial formulations, were injected (51.1 g active ingredient each) directly into the water pumped into the wetland over a 2 h period. Water samples were collected from the wetland upstream of the dosing system at 3 h intervals from the beginning through 360 h and at the exit point at 1, 2, and 3 h intervals for the periods of 0-24, 25-48 and 49-360 h after dosing, respectively. The herbicides were extracted using C-18 cartridges and were analyzed by GC-TSD. The total mass of each herbicide discharged from the system was estimated by multiplying the concentration by the total volume discharged during the sampled period. Neither herbicide was detected in the inflow water during the entire study. Norflurazon was first detected at the exit 19 h after dosing and simazine after 23 h. Discharge patterns of the two herbicides differed dramatically. Norflurazon tended to bleed off from the wetland with no distinct peak concentration. However, the mobile fraction of simazine was discharged over a 58 h period. Mean/maximum/median detectable concentrations of the herbicides were 3.9 ± 1.7/8.1/3.4 µg L(-1) for norflurazon, and 11.9 ± 6.8/23.6/12.0 µg L(-1) for simazine, respectively. The total masses of norflurazon and simazine discharged from the exit during the 15 day study were 51.7 and 26.9 g, indicating 0% and 47.4% removal from the surface water by the system.

Bead-immobilized Pseudomonas stutzeri Y2 prolongs functions to degrade s-triazine herbicides in industrial wastewater and maize fields.

Functional durability of bio-augmented microbes in contaminated fields remains a major challenge in bioremediation. In the present study, various immobilization materials and compositional combinations were designed and compared to enhance the functional durability of Pseudomonas stutzeri sp. Y2 for degradation of simazine, one of the most used herbicides, in industrial wastewater and maize fields. Among four combinations of materials tested, the optimal combination obtained from the orthogonal array trials was 14% polyvinyl alcohol (PVA), 1-3% sodium alginate (SA), 2% activated carbon (AC), and 1-2% Y2 cells (PSC-Y2), which yielded 1.7 fold faster degradation of simazine at 50 mg L-1 than that by free Y2 cells in the industrial wastewater. The degradation half-lives (DT50) of simazine (10 mg L-1) by free Y2 cells and PSC-Y2 was 1.1 d and 5.3 d in laboratory soil, respectively. The DT50 of simazine by PSC-Y2 at the recommended and double dosages of simazine (0.45 and 0.9 g ai·m-2) was 17.2 d and 12.4 d in the maize fields, respectively, in comparison with 23 d and 17.4 d by free Y2 cells. In addition, the PSC-Y2 degraded 100% of atrazine and terbuthylazine, and 96% of propazine at an initial concentration of 50 mg L-1 each in 4 days. This study provides an immobilization strategy to stabilize bacteria and prolong bacterial functions to treat s-triazine herbicides contaminated water and soil.