Trifluralin: photolysis under sunlight conditions and reaction with HO* radicals

Photolytic degradation of commonly used pesticides adsorbed on silica particles

The currently used pesticides are mostly semi-volatile organic compounds. As a result, a fraction of them can be adsorbed on atmospheric aerosol surface. Their atmospheric photolysis is poorly documented, and gaps persist in understanding their reactivity in the particle phase. Laboratory experiments were conducted to determine the photolysis rates of eight commonly used pesticides (i.e., cyprodinil, deltamethrin, difenoconazole, fipronil, oxadiazon, pendimethalin, permethrin, and tetraconazole) using a flow reactor. These pesticides were individually adsorbed on hydrophobic silica particles and exposed to a filtered xenon lamp to mimic atmospheric aerosols and sunlight irradiation, respectively. The estimated photolysis rate constants ranged from less than (3.4 ± 0.3) × 10-7 s-1 (permethrin; >47.2 days) to (3.8 ± 0.2) × 10-5 s-1 (Fipronil; 0.4 days), depending on the considered compound. Moreover, this study assessed the influence of pesticide mixtures on their photolysis rates, revealing that certain pesticides can act as photosensitizers, thereby enhancing the reactivity of permethrin and tetraconazole. This study underscores the importance of considering photolysis degradation when evaluating pesticide fate and reactivity, as it can be a predominant degradation pathway for some pesticides. This contributes to an enhanced understanding of their behavior in the atmosphere and their impact on air quality.

In-package cold plasma treatment to extend the shelf life of food

Conventional food preservation methods such as heat treatment, irradiation, chemical treatment, refrigeration, and coating have various disadvantages, like loss of food quality, nutrition, and cost-effectiveness. Accordingly, cold plasma is one of the new technologies for food processing and has played an important role in preventing food spoilage. Specifically, in-package cold plasma has become a modern trend to decontaminate, process, and package food simultaneously. This strategy has proven successful in processing various fresh food ingredients, including spinach, fruits, vegetables, and meat. In particular, cold plasma treatment within the package reduces the risk of post-processing contamination. Cryoplasm decontamination within packaging has been reported to reduce significantly the microbial load of many foods' spoilage-causing pathogens. However, studies are needed to focus more on the effects of in-package treatments on endogenous enzyme activity, pest control, and removal of toxic pesticide residues. In this review, we comprehensively evaluated the efficacy of in-package low-temperature plasma treatment to extend the shelf life of various foods. The mechanisms by which cold plasma interacts with food were investigated, emphasizing its effects on pathogen reduction, spoilage mitigation, and surface modification. The review also critically assessed the effects of the treatments on food quality, regulatory considerations, and their potential as viable technologies to improve food safety and packaging life. In-package cold plasma treatment could revolutionize food storage when combined with other sophisticated technologies such as nanotechnology.

Influence of pesticide mixture on their heterogeneous atmospheric degradation by ozone and OH radicals

Pesticides in the atmosphere can exist in both gaseous and particulate phases due to their semi-volatile properties. They can undergo degradation when exposed to atmospheric oxidants like ozone and hydroxyl radicals. The majority of studies on the atmospheric reactivity of pesticides study them in combination, without considering potential mixture effects that could induce uncertainties in the results. Therefore, this study aims to address this gap, through laboratory studies using a flow reactor, and by evaluating the degradation kinetics of pendimethalin mixed with folpet, tebuconazole, and S-metolachlor, which were simultaneously adsorbed on hydrophobic silica particles that mimic atmospheric aerosols. The comparison with other mixtures, including pendimethalin, from the literature has shown similar reactivity with ozone and hydroxyl radicals, indicating that the degradation kinetics of pesticides is independent of the mixture. Moreover, the degradation rates of the four pesticides under study indicate that they are not or slightly degraded by ozone, with half-lives ranging from 29 days to over 800 days. In contrast, when exposed to hydroxyl radicals, tebuconazole exhibited the fastest reactivity, with a half-life of 4 days, while pendimethalin had a half-life of 17 days.

Adsorption of Phenoxyacetic Herbicides from Water on Carbonaceous and Non-Carbonaceous Adsorbents

The increasing consumption of phenoxyacetic acid-derived herbicides is becoming a major public health and environmental concern, posing a serious challenge to existing conventional water treatment systems. Among the various physicochemical and biological purification processes, adsorption is considered one of the most efficient and popular techniques due to its high removal efficiency, ease of operation, and cost effectiveness. This review article provides extensive literature information on the adsorption of phenoxyacetic herbicides by various adsorbents. The purpose of this article is to organize the scattered information on the currently used adsorbents for herbicide removal from the water, such as activated carbons, carbon and silica adsorbents, metal oxides, and numerous natural and industrial waste materials known as low-cost adsorbents. The adsorption capacity of these adsorbents was compared for the two most popular phenoxyacetic herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA). The application of various kinetic models and adsorption isotherms in describing the removal of these herbicides by the adsorbents was also presented and discussed. At the beginning of this review paper, the most important information on phenoxyacetic herbicides has been collected, including their classification, physicochemical properties, and occurrence in the environment.

Bioremediation of a trifluralin contaminated soil using bioaugmentation with novel isolated bacterial strains and cyclodextrin

Trifluralin (TFL) is a highly persistent with a strong adsorption capacity on soil particles herbicide. This study was to isolate microbial consortia and bacterial strains from a soil with a historical application of pesticides to evaluate their potential to degrade TFL in soil. Different bioremediation techniques were considered for increasing the effectiveness of TFL degradation in soil. These techniques consisted of: i) biostimulation, using a nutrients solution (NS); ii) bioaugmentation, using a natural microbial consortium (NMC), seven individual bacterial strains isolated from NMC, and an artificial bacterial consortium formed by the seven TFL-degrading bacterial strains (ABC); iii) bioavailability enhancement, using a biodegradable compound, a randomly methylated cyclodextrin, RAMEB. Biostimulation using NS leads up to 34 % of soil TFL biodegraded after 100 d. When the contaminated soil was inoculated with NMC or ABC consortia, TFL loss increased up to 62 % and 74 %, respectively, with DT₅₀ values (required time for the pollutant concentration to decline to half of its initial value) of 5.9 and 11 d. In the case of soil inoculation with the isolated individual bacterial strains, the extent of TFL biodegradation ranged widely from 2.3 % to 55 %. The most efficient bacterial strain was Arthrobacter aurescens CTFL7 which had not been previously described in the literature as a TFL-degrading bacterium. Bioaugmentation with CTFL7 bacterium was also tested in the presence of RAMEB, provoking a drastic increase in herbicide biodegradation up to 88 %, achieving a DT₅₀ of only 19 d. Cyclodextrins had never been tested before for enhancement of TFL biodegradation. An ecotoxicity assay was performed to confirm that the proposed bioremediation techniques were also capable to reduce toxicity. A Microtox® test showed that after application A. aurescens CTF7 and A. aurescens CTF7 + RAMEB, the TFL-contaminated soil, which initially presented acute toxicity, became non-toxic at the end of the biodegradation experiments.

Finding Fluorine: Photoproduct Formation during the Photolysis of Fluorinated Pesticides

The photolysis of pesticides with different fluorine motifs was evaluated to quantify the formation of fluorinated products in buffered aqueous systems, advanced oxidation (AOP) and reduction processes (ARP), and river water. Simulated sunlight quantum yields at pH 7 were 0.0033, 0.0025, 0.0015, and 0.00012 for penoxsulam, florasulam, sulfoxaflor, and fluroxypyr, respectively. The bimolecular rate constants with hydroxyl radicals were 2 to 5.7 × 1010 M-1 s-1 and, with sulfate radicals, 1.6 to 2.6 × 108 M-1 s-1 for penoxsulam, florasulam, and fluroxypyr, respectively. The rate constants of sulfoxaflor were 100-fold lower. Using quantitative 19F-NMR, complete fluorine mass balances were obtained. The maximum fluoride formation was 53.4 and 87.4% for penoxsulam and florasulam under ARP conditions, and 6.1 and 100% for sulfoxaflor and fluroxypyr under AOP conditions. Heteroaromatic CF3 and aliphatic CF2 groups were retained in multiple fluorinated photoproducts. Aryl F and heteroaromatic F groups were readily defluorinated to fluoride. CF3 and CF2 groups formed trifluoroacetate and difluoroacetate, and yields increased under oxidizing conditions. 19F-NMR chemical shifts and coupling analysis provided information on hydrogen loss on adjacent bonds or changes in chirality. Mass spectrometry results were consistent with the observed 19F-NMR products. These results will assist in selecting treatment processes for specific fluorine motifs and in the design of agrochemicals to reduce byproduct formation.

Herbicide Drift from Genetically Engineered Herbicide-Tolerant Crops

In recent years, off-target herbicide drift has been increasingly reported to lead to damage to nontarget vegetation in the U.S. These reports have coincided with the widespread adoption of genetically modified crops with new herbicide-tolerance traits. Planting crops with these traits may indirectly lead to increased drift both by increasing the use of the corresponding herbicides and by facilitating their use as postemergence herbicides later in the season. While extensive efforts have aimed to reduce herbicide drift, critical uncertainties remain regarding the physiochemical phenomena that drive the entry of herbicides into the atmosphere as well as the atmospheric processes that may influence short- and long-range transport. Resolving these uncertainties will support the development of effective approaches to reduce herbicide drift.

Trifluralin residues in soils from main cotton fields of China and associated ecological risk

Trifluralin is a widely used dinitroaniline herbicide in cotton fields of China but is highly persistent in the environment and can act as a biotoxin and cause genotoxicity to terrestrial organisms, including humans. In this study, the concentrations and distribution of trifluralin residues in 139 soil samples from the major cotton-producing areas of China were investigated. The trifluralin concentrations ranged from ND (not detected) to 66.39 μg/kg dry weight (dw), with a geometric mean of 4.13 μg/kg dw. The detection frequency of trifluralin in Hebei (75%) was higher than that in Xinjiang (66%) and Shandong (40%), but the mean trifluralin concentration was highest in Xinjiang (5.98 μg/kg dw), followed by Hebei (5.06 μg/kg dw) and Shandong (3.19 μg/kg dw). No trifluralin residues were detected in cotton soil in Anhui, Jiangxi and Hunan. The residual amount of trifluralin in soil was significantly correlated with the soil organic matter content. The risk quotient method was used to evaluate the ecological risks associated with trifluralin. Results indicated that trifluralin in all the samples had a low risk to earthworms, but trifluralin in same cotton soils showed high risks to wheat, barley and lucerne. Overall, our work is helpful to understand the residual situation of trifluralin in Chinese cotton soil, to assess the environmental risk of trifluralin, and to control the use and safety of trifluralin in cotton field cultivation.

Photocatalytic Degradation of Trifluralin in Aqueous Solutions by UV/S2O82− and UV/ZnO Processes: A Comparison of Removal Efficiency and Cost Estimation

Trifluralin is one of the most widely used herbicides, being accounted as the cause of cancer in human. In the present research, the UV/S2O82− and ZnO/UV processes’ efficiency in the removal of trifluralin was investigated. A lab scale equipped with a UV lamp was applied. The parameters were studied, including initial trifluralin concentration (0.4–1.2 mg/L), contact time (20–60 min), S2O82− concentration (20–60 μM), and ZnO concentration (50–150 mg/L). The remained trifluralin concentration was measured by HPLC. This study proved the trifluralin removal of 92.90 ± 1.6% and 87.91 ± 19.22% for UV/S2O82− and UV/ZnO processes in the best operation conditions (contact time of 60 min, the persulfate concentration of 40 μM, and the ZnO concentration of 100 mg/L). The optimal trifluraline concentrations were 1.2 mg/L and 0.6 mg/L for UV/S2O82− and UV/ZnO processes, respectively. In both processes, the removal efficiency of trifluralin increased significantly with increasing contact time. The findings exhibited that both processes UV/S2O82− and UV/ZnO followed the zero-order kinetic. The electrical energy consumed of UV/S2O82 and UV/ZnO was about 43.95 and 20.41 Kwh/kg, respectively. The results show that UV/S2O82− and ZnO/UV processes were appropriate as the effective treatment method for trifluralin removal. Therefore, it is proposed to study the performance of these processes as an environmentally friendly practice in full scale with real wastewater.

Quantification and risk assessment of pesticides in southern Brazilian air samples using low-volume sampling and rapid ultrasound-assisted extraction

Brazil is one of the largest pesticide consumers in the world. In the last few years, the use of permissive environmental laws and newly authorized pesticide formulations has been enlarged. Thus, the intensive and inadequate use of pesticides may present a risk to human health since these compounds may move between environmental compartments. Outdoor air samples were collected using low-volume samplers at Arapongas city in the state of Paraná, Brazil, between February and November of 2017. Polyurethane foam (PUF) cartridges were presented as a good choice to collect pesticides from atmospheric gas phase samples when compared to styrene-divinylbenzene (XAD-2). Lower limits of quantitation were obtained with PUF cartridges, which allowed a greater number of samples to be quantified in PUF than in XAD-2. Atrazine and trifluralin were quantified for the first time in Brazilian air samples. The levels of concentration ranged between 192-1731 pg m^-3 (chlorpyrifos), 136-1345 pg m^-3 (atrazine) and 184-1189 pg m^-3 (trifluralin). Alachlor has been out of market in Brazil since 2013, and thus it was not detected in any gas phase sample. The highest daily inhalation exposure was observed in infants, 1 × 10^-6 mg kg^-1 d^-1 for atrazine, chlorpyrifos and trifluralin. None of the analyzed pesticides were associated with a hazardous quotient (HQ) > 1, considering the worst-case scenario for infants, indicating that there is no risk associated with the exposed population. Cancer risk assessment for trifluralin resulted in values below 1 × 10^-6, therefore not indicating any significant risk to human health.

Predicting the rate constants of semivolatile organic compounds with hydroxyl radicals and ozone in indoor air

Semivolatile organic compounds (SVOCs) in air can react with hydroxyl radicals (OH), nitrate radicals (NO₃) and ozone (O₃). Two questions regarding SVOC reactivity with OH, NO₃ and O₃ in the gas and particle phases remain to be addressed: according to the existing measurements in the literature, which are the most reactive SVOCs in air, and how can the SVOC reactivity in the gas and particle phases be predicted? In the present study, a literature review of the second-order rate constant (k) was carried out to determine the SVOC reactivity with OH, NO₃ and O₃ in the gas and particle phases in ambient and indoor air at room temperature. Measured k values were available in the literature for 90 polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organophosphates, dioxins, di(2-ethylhexyl)phthalate (DEHP) and pesticides including pyrifenox, carbamates and terbuthylazine. PAHs and organophosphates were found to be more reactive than dioxins and PCBs. Based on the obtained data, quantitative structure-activity relationship (QSAR) models were developed to predict the k value using quantum chemical, molecular, physical property and environmental descriptors. Eight linear and nonlinear statistical models were employed, including regression models, bagging, random forest and gradient boosting. QSAR models were developed for SVOC/OH reactions in the gas and particle phases and SVOC/O₃ reactions in the particle phase. Models for SVOC/NO₃ and SVOC/O₃ reactions in the gas phase could not be developed due to the lack of measured k values for model training. The least absolute shrinkage and selection operator (LASSO) regression and random forest models were identified as the most effective models for SVOC reactivity prediction according to a comparison of model performance metrics.

Persistence of pesticides-based contaminants in the environment and their effective degradation using laccase-assisted biocatalytic systems

Inevitable use of pesticides due to modern agricultural practices and the associated worldwide environmental pollution has called the special attention of the researchers to overcome the persistence, recalcitrance, and multi-faceted toxicity of pesticides-based emerging contaminants. Some restricted use pesticides (RUPs) are highly toxic and carcinogenic chemicals that can be easily accumulated into non-target organisms, including humans, aquatic invertebrates, algae, and microbes. With regard to physicochemical strategies, enzymes-mediated bioremediation is a compelling and meaningful strategy for biodegradation and biotransformation of pesticides into harmless chemical species. Oxidoreductases hydrolases and transferases are among the most representative classes of enzymes pursued and engineered for this purpose. Ligninolytic enzymes, particularly laccases, are of exceptional interest due to high efficiency, specificity, eco-sustainability, and wide-ranging substrates. However, the use of native enzymes is often hindered in industrial processes for the effective removal of refractory compounds by their high cost and susceptibility. Many of these drawbacks can be addressed by enzyme immobilization on some suitable support materials. Increase in stability, reusability, reduction of product inhibition, enhanced activity, specificity, and easier product separation are amid the desirable characteristics of immobilization to construct biocatalysts for continuous systems. This review summarizes recent and up-to-date literature on the use of enzymes, explicitly, free as well as immobilized laccases in the degradation of different pesticides. In the first part, source and occurrence of pesticides in the environment, their types, and associated detrimental effects on the ecosystem/human health are comprehensively described. Afterward, we highlighted the use of different enzymes with a particular emphasis on laccase for the degradation and detoxification of an array of pesticides. Finally, the review is closed with concluding remarks, and possible future direction is proposed in this very important research arena. In conclusion, it is envisioned that effective deployment of laccase-assisted biocatalytic systems for the degradation or removal of diverse pesticides and related contaminants will help to better understand the persistence and removal fate of these hazardous pollutants. Moreover, the current research thrust presented in this review will additionally evoke researcher to engineer robust and sustainable processes to remediate pesticides-contaminated environmental matrices effectively.

Heterogeneous degradation of pesticides by OH radicals in the atmosphere: Influence of humidity and particle type on the kinetics

Pesticides can be adsorbed on the surface of atmospheric aerosol, depending on their physicochemical properties. They can be degraded by atmospheric oxidants such as OH radicals but the influence of some environmental parameters on the degradation kinetics, especially relative humidity and particle surface type, is not well understood. Heterogeneous degradation by OH radicals of eight commonly used pesticides (i.e., difenoconazole, tetraconazole, cyprodinil, fipronil, oxadiazon, pendimethalin, deltamethrin, and permethrin) adsorbed on hydrophobic and hydrophilic silicas at a relative humidity ranging from 0% to 70% was studied. Under experimental conditions, only cyprodinil, deltamethrin, permethrin, and pendimethalin were degraded by OH radical in atmospheric relevant concentration. Second-order kinetic constants calculated for the pesticides degraded by OH radicals ranged from (1.93 ± 0.61) × 10^-13 cm³ molecule^-1 s^-1 (permethrin, hydrophobic silica, 30% RH) to (4.08 ± 0.27) × 10^-12 cm³ molecule^-1 s^-1 (pendimethalin, hydrophilic silica, 0% RH). Results obtained can contribute to improve the understanding of the atmospheric fate of pesticides and other semi-volatile organic compounds in the particulate phase and they highlight the importance of taking humidity and particle type into account for the determination of pesticides atmospheric half-lives.

Atmospheric OH oxidation chemistry of trifluralin and acetochlor

Trifluralin and acetochlor are two nitrogen-containing current use herbicides. While both herbicides have been observed in the atmosphere and have the potential to undergo atmospheric oxidation before deposition to off-target areas, the atmospheric photooxidation chemistry of these species is poorly understood. We use an oxidative flow reactor to expose the two herbicides to increasing concentrations of OH radicals, detecting pesticides and products using an iodide chemical ionization mass spectrometer. We identify new oxidation products and propose photooxidation mechanisms for trifluralin and acetochlor. Both herbicides contain reduced organic nitrogen atoms, and their OH oxidation produces isocyanic acid. While aerosol was observed in the flow reactor only for acetochlor, our results indicate that OH oxidation of neither herbicide would contribute to secondary organic aerosol formation under typical ambient atmospheric conditions. However, high wall losses of both pesticides in the flow reactor suggests that partitioning to pre-existing aerosol may occur and enable subsequent transport in the atmosphere.

Hydrolysis and Photolysis Kinetics, and Identification of Degradation Products of the Novel Bactericide 2-(4-Fluorobenzyl)-5-(Methylsulfonyl)-1,3,4-Oxadiazole in Water

Hydrolysis and photolysis kinetics of Fubianezuofeng (FBEZF) in water were investigated in detail. The hydrolysis half-lives of FBEZF depending on pH, initial concentration, and temperature were (14.44 d at pH = 5; 1.60 d at pH = 7), (36.48 h at 1.0 mg L⁻¹; 38.51 h at 5.0 mg L⁻¹; and 31.51 h at 10.0 mg L⁻¹), and (77.02 h at 15 °C; 38.51 h at 25 °C; 19.80 h at 35 °C; and 3.00 h at 45 °C), respectively. The photolysis half-life of FBEZF in different initial concentrations were 8.77 h at 1.0 mg L⁻¹, 8.35 h at 5.0 mg L⁻¹, and 8.66 h at 10.0 mg L⁻¹, respectively. Results indicated that the degradation of FBEZF followed first-order kinetics, as the initial concentration of FBEZF only had a slight effect on the UV irradiation effects, and the increase in pH and temperature can substantially accelerate the degradation. The hydrolysis Ea of FBEZF was 49.90 kJ mol⁻¹, which indicates that FBEZF belongs to medium hydrolysis. In addition, the degradation products were identified using ultra-high-performance liquid chromatography coupled with an Orbitrap high-resolution mass spectrometer. One degradation product was extracted and further analyzed by ¹H-NMR, ¹³C-NMR, ¹⁹F-NMR, and MS. The degradation product was identified as 2-(4-fluorobenazyl)-5-methoxy-1,3,4-oxadiazole, therefore a degradation mechanism of FBEZF in water was proposed. The research on FBEZF can be helpful for its safety assessment and increase the understanding of FBEZF in water environments.

Atmospheric OH Oxidation of Three Chlorinated Aromatic Herbicides

Chlorinated phenoxy acids are a widely used class of herbicides and have been found in remote regions far from sources. However, the atmospheric chemistry of these compounds is poorly understood. We use an oxidative flow reactor coupled to chemical ionization mass spectrometry to investigate OH oxidation of two chlorinated phenoxyacid herbicides (2-methyl-4-chlorophenoxyacetic acid (MCPA) and mecoprop-p) and one chlorinated pyridine herbicide (triclopyr). OH radicals add to the aromatic rings of the three herbicides, produce peroxides via hydrogen abstraction, or fragment at the ether bond. OH oxidation of MCPA produced two potentially toxic compounds: chlorosalicylaldehyde and chlorosalicylic acid. We use standards to validate the detection of these oxidation products by acetate CIMS and quantify the reaction rate. Oxidation of triclopyr produced a known endocrine disruptor, 3,5,6-trichloro-2-pyridinol. Thus, while some OH oxidation products are less toxic than the parent molecules (e.g., C₁-₅ carboxylic acids), others may be as or more toxic than the parent herbicide. We determine effective rate coefficients for OH addition to the aromatic ring ( k_OH) for mecoprop-p of 1.5 (±0.7) × 10^-12 cm³ molecules^-1 s^-1 and for MCPA of 2.6 (±0.3) × 10^-12 cm³ molecules^-1 s^-1. The atmospheric lifetimes with respect to OH are thus long enough that photochemistry may be relevant to the environmental fate of these pesticides.

Occurrence and distribution of trifluralin, ethalfluralin, and pendimethalin in soils used for long-term intensive cotton cultivation in central Greece

In the present study, a soil monitoring program was undertaken in Greek cotton cultivated areas in 2012. Twenty-seven soil samples were collected from the entire Thessaly plain in early summer of 2012, corresponding to approximately three months (current use of pendimethalin), up to one year (for the banned ethalfluralin), and three years (for the also banned trifluralin), after the last dinitroaniline application. Low but not negligible levels of dinitroanilines were detected, ranging from 0.01 to 0.21 μg g^-1 d.w. for trifluralin and 0.01-0.048 μg g^-1 d.w. for pendimethalin, respectively. Trifluralin was the herbicide most frequently detected (44.4%). The high historic application of trifluralin and its high persistence and accumulation potential is in line with the abundance of the detected residues. The present data indicate that soil samples contain extractable residues of banned trifluralin, but based on the comparison of the theoretical PECplateau for trifluralin (0.277 µg g^-1) and the maximum Measured Environmental Concentration, it was concluded that the detected residues should be attributed to previous years' application. The latter suggested the need for continual monitoring of the dinitroaniline family of pesticides, including the banned substances, aiming thus to an improved environmental profile for agricultural areas.

Pesticide residue concentration in soil following conventional and Low-Input Crop Management in a Mediterranean agro-ecosystem, in Central Greece

The present study was focused on the comparative evaluation of pesticide residues, determined in soil samples from Kopaida region, Greece before and after the implementation of Low-Input Crop Management (LCM) protocols. LCM has been suggested as an environmental friendly plant protection approach to be applied on crops growing in vulnerable to pollution ecosystems, with special focus on the site specific problems. In the case of the specific pilot area, the vulnerability was mainly related to the pollution of water bodies from agrochemicals attributed to diffuse pollution primarily from herbicides and secondarily from insecticides. A total of sixty-six soil samples, were collected and analyzed during a three-year monitoring study and the results of the determined pesticide residues were considered for the impact evaluation of applied plant protection methodology. The LCM was developed and applied in the main crops growing in the pilot area i.e. cotton, maize and industrial tomato. Herbicides active ingredients such as ethalfluralin, trifluralin, pendimethalin, S-metolachlor and fluometuron were detected in most samples at various concentrations. Ethalfluralin, which was the active ingredient present in the majority of the samples ranged from 0.01 μg g(-1) to 0.26 μg g(-1) soil dry weight. However, the amount of herbicides measured after the implementation of LCM for two cropping periods, was reduced by more than 75% in all cases. The method of analysis was based on the simultaneous extraction of the target compounds by mechanical shaking, followed by liquid chromatography mass spectrometric and gas chromatography electron capture (LC-MS/MS and GC-ECD) analysis.

Gas-phase and particulate products from the atmospheric degradation of the organothiophosphorus insecticide chlorpyrifos-methyl

The phosphorothioate structure is highly present in several organophosphorus pesticides. However, there is insufficient information about its degradation process after the release to the atmosphere and the secondary pollutants formed. Herein, the atmospheric reaction of chlorpyrifos-methyl (o,o-dimethyl o-(3,5,6-trichloropyridin-2-yl) phosphorothioate), is described for semi-urban or rural locations. The photo-oxidation under low NOx conditions (5-55 ppbV) was reproduced in a large outdoor simulation chamber, observing a rapid degradation (lifetime<3.5 h). The formation of gaseous products and particulate matter (aerosol yield 2-8%) was monitored. The chemical composition of minor products (gaseous and particulate) was studied, identifying 15 multi-oxygenated derivatives. The most abundant products were ring-retaining molecules such as o,o-dimethyl o-(3,5,6-trichloropyridin-2-yl) phosphorothioate, dimethyl 3,5,6-trichloropyridin-2-yl phosphate, o-methyl o-(3,5,6-trichloropyridin-2-yl) hydrogen phosphorothioate, 3,5,6-trichloropyridin-2-yl dihydrogen phosphate, 3,5,6-trichloropyridin-2-ol, and 3,5,6-trichloropyridine-2,4-diol. An atmospheric degradation mechanism has been proposed based on an oxidation started with OH-nucleophilic attack to P=S bond. The results have been extrapolated to other organothiophosphorus molecules, such as malathion, parathion, diazinon and methidathion, among many others, to estimate their photo-oxidative degradation and the expected products.

Products and mechanisms of the heterogeneous reaction of three suspended herbicide particles with NO₃ radicals

Over 60% of herbicides are capable of disrupting the endocrine and/or reproductive systems of animals. These herbicides may be released into the atmosphere in both gas and particulate phases, but most of their degradation processes in the atmosphere are not well known. In this study, the heterogeneous reactions of suspended isopropalin, trifluralin, and alachlor particles with NO₃ radicals were investigated using an online vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer. The reaction products for the three herbicides were determined by the assistance of the gas chromatography-mass spectrometer analysis. Mono-dealkylated derivatives were detected as the main reaction products of isopropalin and trifluralin. In addition, an α-amino alcohol product was detected for isopropalin. The carbonylation derivative and the nitro-substituted derivative were the main reaction products observed for alachlor. The reaction mechanism of NO₃ radical-induced N-dealkylation for isopropalin was clarified by density functional theory calculations. It began with the H-abstraction from the N-propyl group, followed by the formation of the α-peroxypropyl radical, α-propyloxy radical, and α-amino alcohol, as well as by the collapse of the α-amino alcohol. The oxidation mechanism for trifluralin is similar to that of isopropalin, whereas the mechanism for alachlor involves carbonylation and nitro-substitution. These results provided insights on the chemical transformation of these herbicides in the atmosphere. The data generated from this study can be used as fundamental information for future studies on their toxic effects to the environment.

A review of new and current-use contaminants in the Arctic environment: evidence of long-range transport and indications of bioaccumulation

Systematic monitoring of persistent organic pollutants (POPs) in the Arctic has been conducted for several years, in combination with assessments of POP levels in the Arctic, POP exposure and biological effects. Meanwhile, environmental research continues to detect new contaminants some of which could be potential new Arctic pollutants. This study summarizes the empirical evidence that is currently available of those compounds in the Arctic that are not commonly included in chemical monitoring programmes. The study has focused on novel flame retardants, e.g. alternatives to the banned polybrominated diphenyl ethers (PBDEs), current-use pesticides and various other compounds, i.e. synthetic musk compounds, siloxanes, phthalic acid esters and halogenated compounds like hexachlorobutadiene, octachlorostyrene, pentachlorobenzene and polychlorinated naphthalenes. For a number of novel brominated flame retardants, e.g. 2,3-bibromopropyl-2,4,6-tribromophenyl ether (DPTE), bis(2-ethylhexyl)tetrabromophthalate (TBPH), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), 1,2-bis(2,4,6-tribromophenoxy)-ethane (BTBPE), decabromodiphenyl ethane (DBDPE), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBBz), transport to the Arctic has been documented, but evidence of bioaccumulation is sparse and ambiguous. For short-chain chlorinated paraffins and dechlorane plus, however, increasing evidence shows both long-range transport and bioaccumulation. Ice cores have documented increasing concentrations of some current-use pesticides, e.g. chlorpyrifos, endosulfan and trifluralin, and bioaccumulation has been observed for pentachloroanisole, chorpyrifos, endosulfan and metoxychlor, however, the question of biomagnification remains unanswered.

Gas-phase degradation of the herbicide ethalfluralin under atmospheric conditions

The gas-phase degradation of ethalfluralin, N-ethyl-α,α,α-trifluoro-N-(2-methylallyl)-2,6-dinitro-p-toluidine, a widely used herbicide, was investigated under atmospheric conditions at the large outdoor European simulation chamber (EUPHORE) in Valencia, Spain. The photolysis of ethalfluralin was investigated under solar radiation and the mean photolysis rate coefficient was determined: J(ethalfluralin)=(1.3±0.2)×10(-3) s(-1) (JNO2=8×10(-3) s(-1)). The rate coefficients for the reactions of hydroxyl radicals and ozone with ethalfluralin in the dark were also measured under atmospheric conditions using the relative rate and the absolute rate technique, respectively. The rate coefficients values for the reactions of kOH(ethalfluralin)=(3.5±0.9)×10(-11)cm(3)molecule(-1)s(-1), and kO3(ethalfluralin)=(1.6±0.4)×10(-17) cm(3) molecule(-1) s(-1) were determined at 300±5 K and atmospheric pressure. The results show that removal of ethalfluralin from the atmosphere by reactions with OH radicals (τ ~ 4 h) or ozone (τ ~ 25 h) is slow compared to loss by photolysis. The available kinetic data suggest that the gas-phase tropospheric degradation of ethalfluralin will be controlled mainly by photolysis and provide an estimate for the tropospheric lifetime of approximately 12 min. The atmospheric implications of using ethalfluralin as a herbicide are discussed.

Mechanized and natural soil-to-air transfer of trifluralin and prometryn from a cotton field in Las Cruces, New Mexico

Two pre-emergence herbicides (trifluralin and prometryn) were applied on a cotton field in Las Cruces, New Mexico, and their atmospheric particle and gas-phase concentrations were measured during mechanized soil preparation and natural wind erosion sampling events before and after herbicide application. Air sampling was conducted using samplers mounted at various heights from the ground and at various locations on the field. During mechanized soil management with a disk harrow, sampling occurred at two distances from the tractor ("near-source", 4 m downwind and "far-source", 20-100 m from the disking tractor). Natural background (no disking) sampling events occurred during daytime and at night. Both herbicides were quantifiable for all postapplication sampling events, including background sampling that occurred 8, 38, and 40 days after herbicide application. Average concentrations in both the gas and particle phases ranged from about 10 to 350 ng/m(3). Averaging by event type, mean total prometryn concentrations were 2 (night background) to 8 (near-source) times higher than the corresponding trifluralin concentrations. Prometryn/trifluralin ratios were higher in airborne samples than in soil, indicative of trifluralin losses during daytime sampling, possibly via atmospheric reactions. Prometryn particle phase mass fractions were generally higher than those for trifluralin for all sampling events, consistent with Kair/soil-oc partition coefficients, and particle-phase mass fractions were higher for near-source disking and daytime background sampling compared to far-source and nighttime. Daytime natural background prometryn concentrations could be as high as those measured during disking, and background samples showed significant relationships to meteorological parameters (air temperature, relative humidity, and dewpoint). Mechanical disturbance by tilling operations reduced the ability to predict airborne herbicide concentrations on the basis of meteorological conditions. Prometryn concentrations were higher for larger particle sizes (Dp > 1.8 μm), while no clear patterns with particle size were observed for trifluralin. Trifluralin concentrations in the smallest size bin (PM0.18) were 2-50 times higher than prometryn for the three disking events where an impactor was used, indicating the importance of measuring size-resolved herbicide distributions in future studies.

Gas-phase and particulate products from the atmospheric degradation of an isoxazole fungicide

The isoxazole structure is present in several pesticides. However, there is a lack of information about its degradation products after the release to the atmosphere. The main atmospheric reactions of hymexazol (5-methylisoxazol-3-ol), selected as representative model, were investigated at a large outdoor simulation chamber. The predominant products of atmospheric degradations were gaseous nitrogen derivates (nitric acid, nitrogen dioxide, nitrogen oxide, nitrous acid, and peroxyacetylnitrate), ozone, and small oxygenated compounds (formic acid, formaldehyde, and methylglyoxal). The aerosol yields were lower than 5%, and an OH rate-dependence was observed in the nucleation, particle growth, and size distribution. Also, the chemical composition of minor multi-oxygenated products was studied for OH-photo-oxidations. More than 20 products were detected in the gas or particulate phase. The most abundant were heterocyclic cleavage products with C4-chain and oxygenated moieties at positions 1 and 3, such as 3,4-dioxobutanoic acid, 3-oxobutanoic acid, and 3-oxobutanal. The suggested reaction pathway is the opening of heterocycle ring by the cleavage of N-O bond and C-N bond, releasing nitrogen oxides.

Heterogeneous oxidation of terbuthylazine by "dark" OH radicals under simulated atmospheric conditions in a flow tube

In order to investigate the heterogeneous oxidation kinetics of the herbicide terbuthylazine (TERB), a stable and reproducible generation system of "dark" hydroxyl radical in the gas phase was developed and optimized using a PTR-MS. TERB was adsorbed on silica particles, which were coated on the walls of a flow tube. The hydroxyl radical was produced in the dark through the ozonolysis of 2,3-dimethyl-2-butene (DMB). The radical concentration was determined applying two different methods of calculation based on the monitoring of (i) a gaseous compound used as a tracer, m-xylene; (ii) one of the OH radical precursors, DMB. The obtained gaseous OH radical concentration in the reactor was (9.0 ± 4.0) × 10(7) radical cm(-3). Exposing TERB to the oxidant for 1-14 h, a heterogeneous kinetic constant of kOH = (1.5 ± 0.8) × 10(-13) cm(3) molecule(-1) s(-1) was found at 26 °C and RH < 1%. As a result, the heterogeneous oxidation of TERB by OH radicals seems to be much slower (by a factor of 63) when the organic compound is present in the particulate phase than when it reacts in homogeneous gas phase.

Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean

Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from <MDL to 111 pg/L. Latitudinal trends of α-endosulfan, chlorpyrifos, and dicofol in seawater were roughly consistent with their latitudinal trends in air. Trifluralin in seawater was relatively high in the Sea of Japan (35.2° N) and evenly distributed between 36.9 and 72.5° N, but it remained below the detection limit at the highest northern latitudes in Chukchi Sea. In contrast with other CUPs, concentrations of chlorothalonil and dacthal were more abundant in Chukchi Sea and in East Asia. The air-sea gas exchange of CUPs was generally dominated by net deposition. Latitudinal trends of fugacity ratios of α-endosulfan, chlorothalonil, and dacthal showed stronger deposition of these compounds in East Asia than in Chukchi Sea, while trifluralin showed stronger deposition in Chukchi Sea (-455 ± 245 pg/m(2)/day) than in the North Pacific (-241 ± 158 pg/m(2)/day). Air-sea gas exchange of chlorpyrifos varied from net volatilizaiton in East Asia (<40° N) to equilibrium or net deposition in the North Pacific and the Arctic.

Studies on atmospheric degradation of diazinon in the EUPHORE simulation chamber

The gas phase atmospheric degradation of diazinon has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. The rate constant for reaction of diazinon with OH radicals was measured using a conventional relative rate method with di-n-buthylether as reference compound being k = (3.5 ± 1.2) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 302 ± 10 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of diazinon is mainly controlled by reaction with OH radicals, and that the tropospheric lifetime with respect to the OH reaction is estimated to be around 4h whereas its lifetime with respect to the photolysis is higher than 1d under our conditions. Significant aerosol formation was observed following the reaction of diazinon with OH radicals, and the main carbon-containing products detected in the particle phase were hydroxydiazinon, hydroxydiazoxon and 2-isopropyl-6-methyl-pyrimidinyl-4-ol.

Degradation of organophosphorus pesticide induced by oxygen plasma: effects of operating parameters and reaction mechanisms

The degradation effectiveness and degradation mechanism of representative organophosphorus (OP) pesticide during oxygen plasma treatment have been studied. The identification and quantitative determination of OP pesticide, the degradation mechanisms for OP pesticide destruction, its destruction intermediates, and by-products were performed using gas chromatography/mass spectrometry (GC/MS). Plausible mechanisms of the degradation are discussed. Experimental results indicate that oxygen plasma treatment has noticeable effects on OP pesticide with satisfactory degradation efficiency, which mainly depends on related operating parameters including plasma treatment time, discharge power, distance from the center of the induction coil, and concentrations of OP pesticide. It was found that OP pesticide was degraded into less-toxic compounds, and free radical reaction and addition reaction were to be the dominated the degradation mechanisms for OP pesticides treated by oxygen plasma. Therefore, our results suggest that oxygen plasma is suitable for degradation of OP pesticide.

Kinetics and mechanism of the degradation of two pesticides in aqueous solutions by ozonation

This study evaluated the reaction kinetics and degradation mechanism of the pesticides bromoxynil and trifluralin during conventional ozonation. The second-order rate constants for the direct molecular ozone and hydroxyl radical reactions with bromoxynil and trifluralin were determined using a rapid-scan stopped-flow spectrophotometry, competition kinetics, and an organic substrate monitoring method. High reactivity toward ozone and hydroxyl radicals was observed for bromoxynil and trifluralin. The second-order rate constants for the reaction with ozone were about 10(2)M(-1)s(-1). The values of the second-order rate constants for the reaction between hydroxyl radicals and bromoxynil and trifluralin in ultrapure water at 20 degrees C were estimated to be around 8.4x10(9) and 7.5x10(9)M(-1)s(-1), respectively. The identification of oxidation by-products generated during ozonation was also addressed. It was found that hydroxylation and debromination were the primary pathways for the bromoxynil degradation, whereas hydroxylation and dealkylation were found to be the major mechanisms for trifluralin oxidation.

Ozonation of trifluralin particles: an experimental investigation with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer

The ozonation of trifluralin coated on azelaic acid particles is investigated with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer. The suspended trifluralin particles with the mean diameter of 270nm react with approximately 100ppm ozone in an aerosol reaction chamber under ambient pressure and room temperature (1atm, 298K). The time-of-flight mass spectra of the trifluralin particles and the solid state ozonides are obtained. The assignments of the mass spectra reveal that the major primary ozonides of trifluralin particles are 2,6-dinitro-N-propyl-N-propanoyl-4-(trifluoromethyl) benzamine and 2,6-dinitro-N-(propan-2(and 3)-ol)-N-propyl-4-(trifluoromethyl) benzamine. The major secondary ozonides of trifluralin 2-ethyl-7-nitro-5-(trifluoromethyl) benzimidazole-3-oxide, 2,6-dinitro-N-propyl-4-(trifluoromethyl) benzenamine and 2,6-dinitro-N-(formyl)-N-propyl-4-(trifluoromethyl) benzamine are observed. The primary ozonides are directly resulted from the oxidation of N-propyl groups. The pathways of the primary ozonation are proposed in the paper.

Comparison of annual dry and wet deposition fluxes of selected pesticides in Strasbourg, France

This work summarizes the results of a study of atmospheric wet and dry deposition fluxes of Deisopropyl-atrazine (DEA), Desethyl-atrazine (DET), Atrazine, Terbuthylazine, Alachlor, Metolachlor, Diflufenican, Fenoxaprop-p-ethyl, Iprodione, Isoproturon and Cymoxanil pesticides conducted in Strasbourg, France, from August 2000 through August 2001. The primary objective of this work was to calculate the total atmospheric pesticide deposition fluxes induced by atmospheric particles. To do this, a modified one-dimensional cloud water deposition model was used. All precipitation and deposition samples were collected at an urban forested park environment setting away from any direct point pesticide sources. The obtained deposition fluxes induced by atmospheric particles over a forested area showed that the dry deposition flux strongly contributes to the total deposition flux. The dry particle deposition fluxes are shown to contribute from 4% (DET) to 60% (cymoxanil) to the total deposition flux (wet+dry).