The photocatalytic degradation of the insecticide fenitrothion was performed in the water solution in the presence of TiO2 by UV illumination. NMR spectrocopy showed that the decomposition of the initial substrate and all intermediates formed to the mineralization end products is completed in 66.3 hours. This fact was used to establish the possible mechanisms of the degradation process. The obtained results show that this method may have an important application in the removal of fenitrothion from water.

Here we investigate the photodegradation of structurally similar organophosphorus pesticides; methyl-parathion and fenitrothion in water (20 °C) and ice (−15 °C) under environmentally-relevant conditions with the aim of comparing these laboratory findings to limited field observations. Both compounds were found to be photolyzed more efficiently in ice than in aqueous solutions, with quantum yields of degradation being higher in ice than in water (fenitrothion > methyl-parathion). This rather surprising observation was attributed to the concentration effect caused by freezing the aqueous solutions. The major phototransformation products included the corresponding oxons (methyl-paraoxon and fenitroxon) and the nitrophenols (3-methyl-nitrophenol and nitrophenol) in both irradiated water and ice samples. The presence of oxons in ice following irradiation, demonstrates an additional formation mechanism of these toxicologically relevant compounds in cold environments, although further photodegradation of oxons in ice indicates that photochemistry of OPs might be an environmentally important sink in cold environments. Photodegradation of methyl-parathion and fenitrothion in water and ice under environmentally-relevant conditions is described.

We assessed the contamination, dynamics, and health risks of the pesticides cyanazine, simetryn, fenarimol, isoprothiolane, diazinon, irgarol, fenitrothion, and diuron in marine samples (seawater, sediments, plankton, fish, and other edible organisms) at various locations in the Seto Inland Sea in Japan in 2016 and 2017. Pesticide concentrations were highest at sampling sites close to the coastline, and mean concentrations in seawater were slightly higher in surface water than in bottom water. All eight pesticides were detected in plankton. Diazinon concentrations (77–387 ng/g dw) were highest in sediments and cyanazine was the most frequently detected pesticide (88%, n = 17) in sediments. Only cyanazine (2.7–41.9 ng/g dw), simetryn (1.0–34.3 ng/g dw), and diazinon (6.3–308.8 ng/g dw) were detected in fish and other edible marine organisms. Based on the calculated bioconcentration factor, the results showed that plankton, fish, and marine animals bioaccumulated pesticides. The highest hazard quotients were calculated for diazinon in red seabream and greenling, indicating a possible risk to consumers. It is, therefore, imperative to promote strict implementation of pollution control, integrated pest management practices, and policy formulation on pesticides. Usage of diazinon must be controlled and monitored to ensure large residues do not reach aquatic ecosystems and marine coastlines.

Amphibians are the most important vulnerable non-target vertebrate group that are affected by pesticides. Most previous studies have confirmed the destructive effects of pesticides. But, so far, no comprehensive studies have been carried out in Iran. Therefore, to estimate the mortality rate of frogs during the growing season in different cultivating systems, we examined the presence of pesticides in water and substrate as indicators of habitat quality and in the liver tissue of Marsh frog Pelophylax ridibundus (Pallas, 1771), enclosed in the prepared cages at five rice paddy fields in Mazandaran province, Iran. The measurement of pollution was done using mass gas chromatography method and statistical analyses by Minitab software. Furthermore, the probable movement pattern of free frogs was analyzed using capture-mark-recapture method. Thirteen pesticides were detected both in the habitat and in frogs’ liver tissue. Among them ß-Mevinphos, Fenitrothion, Bromofos, and Trifluralin had the most frequent occurrence in liver tissue, and Diazinon with concentrations up to 517.8 μg/Kg had the highest concentration. Furthermore, there is a significant correlation (R² > 0.96) between water quality and frogs’ contamination, whereas, no correlation was observed between substrate pollution and frogs’ contamination. Pesticide concentrations were higher in two stations but lower than lethal doses to frogs, so that no mortality was observed at any of the stations. However, some specimens had a considerable muscle atrophy. Despite no significant movement pattern was detected, we can expect that if this trend continues, in a long term, they will face a reduction in the survival rate.

The photochemical degradation of two widely used organophosphorothioate insecticides, fenitrothion and diazinon, was investigated in aqueous solutions containing three separate dissolved constituents commonly found in natural waters (NO 3 − , CO 3 2− and dissolved organic matter (DOC)). The effect of these constituents on pesticide photodegradation was compared to degradation in “constituent-free” pure water. Solutions were irradiated in an Atlas solar simulator fitted with a UV-filtered Xenon arc lamp with light irradiances (500 W m−2) measured using a spectral radiometer to allow derivation of quantum yields of degradation. Fenitrothion absorbs light within the solar UV range (λ, 295–400 nm) and underwent direct photolysis in pure water whereas diazinon (λ max ∼250 nm) showed no observable loss over the experimental period. However, photodegradation conforming to pseudo-first-order kinetics was observed for both chemicals in the presence of the dissolved constituents (at concentrations typically observed in natural waters), with the rates of photodecay observed in the order of NO 3 − > CO 3 2− ≅ DOC, with the highest rates observed in the 3 mM NO 3 − solutions (k Fen = 0.155 ± 0.041 h−1; k Dia = 0.084 ± 0.0007 h−1). For diazinon this rate was comparable to fenitrothion photolysis in pure water (k fen 0.072 ± 0.0078 h−1), highlighting the importance of NO 3 − on a non-photolabile pesticide, with indirect photodegradation probably attributable to the light-induced release of aqueous hydroxyl radicals (·OH) from NO 3 − . Suwannee river fulvic acid (serving as DOC) did not statistically affect the rate of photodecay for fenitrothion relative to its photolysis in MilliQ water, although measured rates in DOC solutions were slightly lower. However, measurable rates of photodecay were apparent for diazinon in the DOC solutions, indicating that fulvic acid, possibly in the form of “excited” triplet-state-DOC plays a role in diazinon transformation. Hydrolysis was not apparent for fenitrothion (in buffered solutions of pH 5–9) but was notable for diazinon at the lower pHs of 5 and 3 (k Dia-hyd 0.3414 h−1 at pH 3 and 0.228 h−1 at pH 5), resulting in the formation of the degradate, 2-isopropyl–6-methyl–4-pyrimidinol. This work highlights the importance of dissolved constituents on abiotic photodegradation of pesticides and it is recommended that these constituents be incorporated into laboratory-based fate-testing regimes.

The bacterial strain Sphingobium sp. YW16, which is capable of degrading monocrotophos, was isolated from paddy soil in China. Strain YW16 could hydrolyze monocrotophos to dimethylphosphate and N-methylacetoacetamide and utilize dimethylphosphate as the sole carbon source but could not utilize N-methylacetoacetamide. Strain YW16 also had the ability to hydrolyze other organophosphate pesticides. A fragment (7067 bp) that included the organophosphorus hydrolase gene, opdA, was acquired from strain YW16 using the shotgun technique combined with SEFA-PCR. Its sequence illustrated that opdA was included in TnopdA, which consisted of a transpose gene, a putative integrase gene, a putative ATP-binding protein gene, and opdA. Additionally, a conjugal transfer protein gene, traI, was located downstream of TnopdA. The juxtaposition of TnopdA with TraI suggests that opdA may be transferred from strain YW16 to other bacteria through conjugation. OpdA was able to hydrolyze a wide range of organophosphate pesticides, with the hydrolysis efficiency decreasing as follows: methyl parathion > fenitrothion > phoxim > dichlorvos > ethyl parathion > trichlorfon > triazophos > chlorpyrifos > monocrotophos > diazinon. This work provides the first report of opdA in the genus Sphingobium.

Biofilters have been shown to be efficient for removing pollutants from different water effluents, but little information is available about their capacity to remove highly polar pesticides from agricultural run-off waters. In this study, we assess the capacity of three different biofilter-supporting materials (sand, peat soil, and pine bark) to remove five phenoxyacid herbicides (mecoprop, dicamba, MCPA, dichlorprop and 2,4-D) and five non-ionic pesticides (atrazine, simazine, fenitrotion, diazinon, and alachlor) from real agricultural run-off waters. The experimental design included three columns 120 cm in length and 15 cm in diameter, each filled with 100 cm of one of the selected supporting materials. After 30 days of acclimation, the columns were fed with agricultural run-off water spiked at 10 μg L⁻¹ with each of the studied pesticides for 20 days at a hydraulic loading rate (HLR) of 0.32 m day⁻¹. The results show that the sand filter was the best supporting material for removing phenoxyacid herbicides (77% on average), whereas peat soil and pine bark were best for removing non-ionic pesticides (72% on average). The attenuation of mecoprop and dichlorprop correlated negatively with the enantiomeric fraction. Therefore, this study shows that the use of waste-to-product materials in biofilter systems is a good solution for removing pollutants from agricultural run-off waters.

Vegetated filter strips (VFSs) are planted at the edge of agricultural fields to reduce pesticide run-off and its consequent potential toxicological effects on ecosystem biota; however, little attention has been paid to date to the attenuation of highly polar and ionisable pesticides such as phenoxyacid herbicides. This study assesses the effect of soil moisture, run-off flow and vegetation on the attenuation of MCPA, mecoprop, dicamba, dichlorprop, fenitrothion, atrazine and simazine by VFSs. Reactors measuring 5 m long by 0.1 m wide were each filled with 60 kg of soil from a real field VFS. VFSs planted with Phragmites australis and unvegetated control reactors were assessed. After a simulated rainfall event of 50 mm, two hydraulic loading rates (HLRs) were assessed (1 and 2 cm h⁻¹). These results were compared to those from the same systems under water-saturated conditions. The results show that VFSs reduced the peak inlet concentration and pesticide mass by more than 90 % and that the presence of vegetation increased that attenuation (82–90 % without vegetation and 90–93 % with vegetation, on average). The laboratory-scale study showed that such attenuation was due to sorption into the soil. The toxicity units of pesticides fell by more than 90 % in all cases, except under the water-saturated conditions, in which the decrease was lower (16 vs 54 %, for unvegetated and vegetated reactors). Therefore, the presence of vegetation was shown to be effective for reducing mass discharge of ionisable and highly polar pesticides into surface-water bodies.