Four phenylurea herbicides (PUHs) were assessed for degradation and transformation into N-nitrosodimethylamine (NDMA) under three oxidation conditions (chlorine (Cl₂), chlorine dioxide (ClO₂), and ozone (O₃)) from an aqueous solution. Removal ratios correlated with the numbers of halogen elements contained in PUHs (isoproturon ₍₀₎ > chlorotoluron ₍₁ Cₗ₎ > diuron ₍₂ Cₗ₎ > fluometuron ₍₃ F₎), and the degradation efficiencies of oxidants from fastest to slowest were: O₃, ClO₂, and Cl₂. NDMA can be generated directly from the ozonation of PUHs. Further, compared with chloramination alone, ozonation prominently promoted NDMA formation potential (NDMA-FP) during post-chloramination, and NDMA-FPs increased approximately 23–68 times than those during ozonation only at 2.5 mg/L O₃ over 10 min; molar yields of NDMA from highest to lowest were 11.1% (isoproturon), 1.17% (chlorotoluron), 1.0% (diuron), and 0.73% (fluometuron). The PUH degradation kinetics data during ozonation agreed with the pseudo-first-order model. The rate constant kₒbₛ were 0.31 × 10⁻³–19.8 × 10⁻³ s⁻¹. The kₒbₛ and removal ratios of PUHs during ozonation partially scaled with the mass, LogKₒw, and Henry’s constants of PUHs. Comparisons of measured NDMA-FPs with calculated NDMA-FPs from residual PUH after oxidation showed that the intermediates produced during ozonation facilitated NDMA-FPs; this contribution was also observed for chlorotoluron and isoproturon during ClO₂ oxidation. Examination of reaction mechanisms revealed that tertiary amine ozonation, N-dealkylation, hydroxylation, the cleavage of N–C bonds, ammonification, and nitrification occurred during the ozonation of PUHs, and the dimethylamine (DMA) functional groups could be decomposed directly and transformed into NDMA via the formation of the intermediate unsymmetrical dimethylhydrazine. NDMA is also formed from the reaction between DMA and phenylamino-compounds. Clarifying primary degradation products of PUHs and transformation pathways of NDMA during oxidation processes is useful to optimize treatment processes for water supplies.

Chlorotoluron (Chl) is a phenylurea herbicide and is widely used for controlling weeds. While it has brought great benefits to crop production, it has also resulted in contamination to ecosystem. In this study, we investigated accumulation of chlorotoluron (Chl) and biological responses of wheat plants as affected by dissolved organic matter (DOM). Wheat seedlings grown under 10 mg kg−1 Chl for 4 d showed a low level of chlorophyll accumulation and damage to plasma membrane. The growth was inhibited by exposure of chlorotoluron. Treatment with 50 mg DOC kg−1 DOM derived either from sludge (DOM-SL) or straw (DOM-ST) attenuated the chlorotoluron toxicity to plants. Both DOMs decreased activities of catalase, peroxidase and superoxide dismutase in Chl-treated seedlings. However, an increased glutathione S-transferases activity was observed under the same condition. Wheat plants treated with Chl in the presence of DOM accumulated less Chl than those treated with Chl alone. Moreover, in the presence of DOM, bioconcentration factor (BCF) decreased whereas translocation factors increased. Analyses with FT-IR spectra confirmed the regulatory role of DOMs in reducing Chl accumulation in wheat. Dissolved organic matter (DOM) as a soil amendment can reduce herbicide accumulation in crops.

The present pilot study aimed to provide an overview of organic contaminant concentration levels in the littoral ecosystems of the Pertuis seas. The study determined the concentrations of twenty-nine pesticides, six nonylphenols and seven polybrominated diphenyl ethers (PBDEs) in sediments, seawater, Pacific oysters and blue mussels. Oysters accumulated a higher number of pesticides than blue mussels. Indeed, alpha BHC (0.60–0.72 ng/g, ww), chlorfenvinphos (1.65–2.12 ng/g, ww), chlorpyrifos (0.79–0.93 ng/g, ww), chlortoluron (2.50–4.31 ng/g, ww), metolachlor (up to 0.38 ng/g, ww) and parathion (0.56–0.69 ng/g, ww) were quantified in oysters whereas only alpha BHC (0.24–0.31 ng/g, ww), was quantified in mussels. The present results also revealed that the POPs detected in water or sediments were not ultimately found accumulated in bivalves. Other molecules such as methylparathion and BDE47 were quantified in sediments. These molecules, BDE99 and one nonylphenol (OP2OE) were quantified in seawater. Finally, the comparison with the available environmental guidelines showed that the values measured were at concentrations not considered to cause adverse effects at the populations' level except for chlortoluron in seawater (15–50 ng/L).

Pesticides are still widely used by agriculture, leading to the exposure of surface water. This may be the case for fish ponds located in farmland landscapes. To address this issue, the present study investigated the contamination by pesticides of fish ponds located in the mixed agriculture-pond landscape of the Dombes area, France. Ten ponds were selected in water catchments with a gradient of 3–57 ha of cropland with maize and winter cereals as the dominant crops. A total of 197 water samples were collected in the ponds during the fish production season over 3 years. Recently used pesticides were the most frequent residues occurring. Occurrences greater than 0.1 µgL⁻¹ particularly concerned chlorotoluron and S-metolachlor. Maximum observed concentrations were slightly above 3 µgL⁻¹ for S-metolachlor, acetochlor, and dimethenamide, all herbicides allowed for maize cultivation. Isoproturon and chlorotoluron, herbicides allowed in cereal crops, reached up to 1.2 and 1.0 µgL⁻¹, respectively. We found a significant positive effect of crop area in catchments on the pond contamination frequency by pesticides and more significantly on the contamination frequency by broad-spectrum herbicides (glyphosate and AMPA residues). The cumulative antecedent rainfall was best correlated to the frequency of highest contaminations (> 0.5 µgL⁻¹). In such a hydrological context, the crop area within catchment was identified as a good indicator of fish pond exposure to pesticide residues. Finally, we proposed to adapt some mitigation measures to reduce fish pond contamination.

Since the end of the 1980s, white shrimps (Palaemon longirostris) from the Gironde estuary have exhibited exoskeletal malformations, mainly involving cephalothorax, rostrum, scaphocerites and uropods. An 8-month study was carried out in 2015. Each month, 200 individuals were sampled and examined for exoskeletal malformations. Temporal variations in malformation frequency were noted, particularly during the breeding period, along with decreases in the size of non-deformed shrimps related to the appearance of juveniles in breeding sites, and high mortality among deformed shrimps. A significant increase in proportions of deformed shrimp was observed, relating particularly to the size (and therefore the age) of individuals. No significant difference was found between shrimp proportions with different numbers of malformations (one to four) for a fixed size class, nor was there any variation in proportions within different size classes for a fixed number of malformations. This would appear to indicate that the number of malformations is acquired and new malformations do not seem to appear during the life cycle, except for the smallest (youngest) shrimps. The malformation spectrum showed no significant differences between the biggest and smallest individuals for the different malformation associations, except for those involving cephalothorax, rostrum and uropods. This would suggest that some malformation associations lead to a higher mortality rate in shrimps subjected to them, due to greater impairment of feeding and/or swimming behaviour. Multiple component analysis of the different types of malformation showed correlations between exoskeletal pieces (rostrum and cephalothorax) and appendixes (scaphocerites and uropods). Regarding metal contamination in shrimp, no significant difference was highlighted between deformed and non-deformed shrimps. Organic pollutants were not measured in tissues. Certain herbicides such as metolachlore and chlortoluron were detected at high concentrations in the Gironde estuary during the breeding period corresponding to the higher occurrence of exoskeletal malformations.

Based on the enhancing effect of chitosan (CS) on luminol-dissolved oxygen chemiluminescence (CL) reaction, a flow injection (FI) luminol–CS CL system was established. It was found that the increase of CL intensity was proportional to the concentrations of CS ranging from 0.7 to 10.0 μmol l⁻¹. In the presence of chlortoluron (CTU), the CL intensity of luminol–CS system could be obviously inhibited and the decrements of CL intensity were linearly proportional to the logarithm of CTU concentrations ranging from 0.01 to 70.0 ng ml⁻¹, giving the limit of detection 3.0 pg ml⁻¹ (3σ). At a flow rate of 2.0 ml min⁻¹, the whole process including sampling and washing could be accomplished within 36 s, offering a sample throughput of 100 h⁻¹. The proposed FI–CL method was successfully applied to the determination of CTU in soil samples with recoveries ranging from 95.0 % to 105.3 % and the relative standard deviations (RSDs) of less than 4.0 %.

Transgenic Arabidopsis thaliana plants were generated by introduction of the human P450 CYP1A2 gene, which metabolizes a number of herbicides, insecticides and industrial chemicals. Transgenic A. thaliana plants expressing CYP1A2 gene showed remarkable resistance to the phenylurea herbicide chlortoluron (CTU) supplemented either in plant growth medium or sprayed on foliar parts of the plants. HPLC analyses showed a strong reduction in CTU accumulation in planta supporting the tolerance of transgenic lines to high concentrations of CTU. Besides increased herbicide tolerance, expression of CYP1A2 resulted in no other visible phenotype in transgenic plants. Our data indicate that CYP1A2 can be used as a selectable marker for plant transformation, allowing efficient selection of transgenic lines in growth medium and/or in soil-grown plants. Moreover, these transgenic plants appear to be useful for herbicide resistance as well as phytoremediation of environmental contaminants.

The ability of a plant cytochrome P450 to bind and metabolise plant endogenous molecules and xenobiotics was investigated. The work was performed on the yeast-expressed CYP73A1, a cinnamate 4-hydroxylase isolated fromHelianthus tuberosus. CYP73 controls the general phenylpropanoid pathway and is likely to be one of the most abundant sources of P450 in the biosphere. The enzyme shows a high selectivity toward plant secondary metabolites. Nevertheless, it oxygenates several small and planar xenobiotics with low efficiency, including an herbicide (chlorotoluron). One xenobiotic molecule, 2naphthoic acid, is hydroxylated with an efficiency comparable to that of the physiological substrate. This reaction was used to devise a fluorimetric test for the rapid measurement of enzyme activity. A series of herbicidal molecules (hydroxybenzonitriles) are shown to bind the active site without being metabolised. These molecules behave as strong competitive inhibitors of CYP73 with a Kᵢ in the same micromolar range as the Kₘ for the physiological substrate. It is proposed that their inhibition of the phenylpropanoid pathway reinforces their other phytotoxic effects at the level of the chloroplasts. All our results indicate a strong reciprocal interaction between plant P450s and xenobiotics.

The frequency and mass concentrations of 13 herbicide micropollutants (triazines, phenylureas, chloroacetanilides and trifluralin) were investigated during 2014 in surface, ground and drinking waters in the area of the city of Zagreb and its suburbs. Herbicide compounds were accumulated from water by solid-phase extraction using either octadecylsilica or styrene-divinylbenzene sorbent cartridges and analysed either by high-performance liquid chromatography with UV-diode array detector or gas chromatography with mass spectrometric detection. Atrazine was the most frequently detected herbicide in drinking (84 % of samples) and ground (61 % of samples) waters in mass concentrations of 5 to 68 ng L⁻¹. It was followed by metolachlor and terbuthylazine, the former being detected in 54 % of drinking (up to 15 ng L⁻¹) and 23 % of ground (up to 100 ng L⁻¹) waters, and the latter in 45 % of drinking (up to 20 ng L⁻¹) and 26 % of ground (up to 25 ng L⁻¹) water samples. Acetochlor was the fourth most abundant herbicide in drinking waters, detected in 32 % of samples. Its mass concentrations of 107 to 117 ng L⁻¹ in three tap water samples were the highest of all herbicides measured in the drinking waters. The most frequently (62 % of samples) and highly (up to 887 ng L⁻¹) detected herbicide in surface waters was metolachlor, followed by terbuthylazine detected in 49 % of samples in mass concentrations of up to 690 ng L⁻¹, and atrazine detected in 30 % of samples in mass concentrations of up to 18 ng L⁻¹. The seasonal variations in herbicide concentrations in surface waters were observed for terbuthylazine, metolachlor, acetochlor, chlortoluron and isoproturon with the highest concentrations measured from April to August.

The evaluation of sediments, concerning to pesticides, constitutes an important step for the understanding of the principal sources of contamination of the surface water. Hence, the purpose of this study was to evaluate for the first time the occurrence, distribution and risk of pesticides in sediments of the Alqueva reservoir, the largest reservoir in the Europe. For this purpose, the occurrence of 22 pesticides and some of their degradation products was determined in surficial sediments of the Alqueva reservoir. To assess the potential risk on ecosystem, the measured concentrations of pesticides were compared with regulatory and toxicological benchmarks. Of the 22 pesticides analysed, only 8 were detected. Diuron was the pesticide detected in greater concentration, followed by terbuthylazine and chlortoluron. The sediments most polluted by pesticides were from Lucefécit, constituted totally by fine particles (<0.063 mm) and with high values of organic matter, and are located nearby large agricultural fields. The risk assessment allowed us to conclude that the sediments from the Alqueva reservoir presented low risk, concerning to pesticides, for the various communities that integrate the aquatic ecosystems. However, some of the compounds detected present a high potential for bioaccumulation that may lead to their bioamplification in the trophic chain, reaching concentrations higher than their acceptable daily intake, putting, in this way the populations at risk.