Factors governing spatial and temporal patterns of pesticide compounds (pesticides and metabolites) concentrations in chalk aquifers remain unclear due to complex flow processes and multiple sources. To uncover which factors govern pesticide compound concentrations in a chalk aquifer, we develop a methodology based on time series analyses, uni- and multivariate statistics accounting for concentrations below detection limits. The methodology is applied to long records (1996–2013) of a restricted compound (bentazone), three banned compounds (atrazine, diuron and simazine) and two metabolites (deethylatrazine (DEA) and 2,6–dichlorobenzamide (BAM)) sampled in the Hesbaye chalk aquifer in Belgium. In the confined area, all compounds had non-detects fractions >80%. By contrast, maximum concentrations exceeded EU's drinking-water standard (100 ng L−1) in the unconfined area. This contrast confirms that recent recharge and polluted water did not reach the confined area, yet. Multivariate analyses based on variables representative of the hydrogeological setting revealed higher diuron and simazine concentrations in the southeast of the unconfined area, where urban activities dominate land use and where the aquifer lacks protection from a less permeable layer of hardened chalk. At individual sites, positive correlations (up to τ=0.48 for bentazone) between pesticide compound concentrations and multi-annual groundwater level fluctuations confirm occurrences of remobilization. A downward temporal trend of atrazine concentrations likely reflects decreasing use of this compound over the last 28 years. However, the lack of a break in concentrations time series and maximum concentrations of atrazine, simazine, DEA and BAM exceeding EU's standard post-ban years provide evidence of persistence. Contrasting upward trends in bentazone concentrations show that a time lag is required for restriction measures to be efficient. These results shed light on factors governing pesticide compound concentrations in chalk aquifers. The developed methodology is not restricted to chalk aquifers, it could be transposed to study other pollutants with concentrations below detection limits.

Fish cultivation in rice fields is a valuable resource in some rural areas of the world. Fish is a source of protein and an additional source of income for local farmers. However, the use of pesticides may impact fish and consumer health. The aim of this study was to evaluate exposure and effect biomarkers in native fish inhabiting a rice field during a production cycle. Samples of fish, water and sediment from a rice field in Santa Fe, Argentina were collected during a cultivation season (at the beginning: November 2017, in the middle: December 2017 and at the end: February 2018). At each sampling period, fish biomarkers of effect (biometric indices, hematological parameters, energy reserves, oxidative stress and neurotoxicity) were assessed together with pesticide screening in water, sediment, and fish samples. Only herbicides were present in water and sediment samples in agreement with land treatment before rice sowing stage, where only herbicides were applied. In general, the greatest water concentrations of bentazone, glyphosate and aminomethylphosphonic acid (AMPA), and the lowest sediment glyphosate and AMPA levels were observed at the beginning of the farming cycle. Fish bioaccumulated AMPA residues at all sampling periods and showed biological responses to cope with a stressful environment. Alterations in hematological parameters, mobilization of energetic reserves and activation of the antioxidant system were detected. However, no oxidative damage nor neurotoxic effects were present along the production cycle. Under a real exposure scenario, the present work demonstrates that biological changes are induced in fish to cope with stressors present in a rice field. Fish-rice coculture is an efficient and ecologically sustainable approach to increase food supplies, and a better understanding of the effect of this particular environment on fish would allow a greater and safer development of this promising productive activity in South American rice producing countries.

Two LC-MS/MS methods including different sample preparation and quantitative processes showed a good agreement for analysis of the herbicides MCPA, mecoprop, isoproturon, bentazon and chloridazon, and the metabolite chloridazon-methyl-desphenyl (CMD) in estuarine waters. Due to different sensitivity of the methods only one could be used to analyze marine samples. The transport of these compounds to the Baltic Sea via ten German estuaries and their distribution between coastal water and sediments was studied. The results showed that all selected compounds can be transported to the Baltic Sea (0.9–747ng/L). Chloridazon, bentazon, isoproturon and CMD were detected (0.9–8.9ng/L) in the coastal waters and chloridazon and isorproturon in the sediments (5–136pg/g d.w.). Levels of contaminants in the sediments could be influenced by the total organic carbon content. Concentrations observed in the Baltic Sea are most likely not high enough to cause acute effects, but long term effect studies are strongly recommended.

Microcosms, each consisting of 2L natural surface seawater maintained in 2.3-L glass bottles, were immersed at a depth of 6m. The renewal of 10% of microcosm volumes was carried out every other day. Phytoplankton-containing seawater was used for renewal (previously filtered through 25-, 50- or 200-μm cut-off). Phytoplankton community pigment analysis (by HPLC) and flow cytometry analysis were performed. After 13days, data exhibited phytoplankton characteristics in microcosms in the same range as that of the natural surrounding sea water over the same period. Furthermore, in these microcosms, a negative correlation was observed between the filtration cut-off used for renewal water, and the total cell count. Herbicides were tested as commercial mixtures at 1, 10 and 100μgL⁻¹ active substance. Both Frontier® (dimethenamid) and Basamais® (bentazon) induced significant modifications of the phytoplankton populations at every concentration tested. Such results suggest a possible disturbance in polluted coastal areas.

Microcosms, each consisting of 2 L natural surface seawater maintained in 2.3-L glass bottles, were immersed at a depth of 6 metres. The renewal of ten percent of microcosm volumes was carried out every other day. Phytoplankton-containing seawater was used for renewal (previously filtered through 25-, 50- or 200-μm cut-off). Phytoplankton community pigment analysis (by HPLC) and flow cytometry analysis were performed. After 13 days, data exhibited phytoplankton characteristics in microcosms in the same range as that of the natural surrounding sea water over the same period. Furthermore, in these microcosms, a negative correlation was observed between the filtration cut-off used for renewal water, and the eukaryote cell count. Herbicides were tested as commercial mixtures at 1, 10 and 100 μg.L-1 active principal. Both Frontier® (dimethenamid) and Basamais® (bentazon) induced significant modifications of the phytoplankton populations at every concentration tested. Such results suggest a possible disturbance in polluted coastal areas.

Herbicides are hazardous organic pollutants that contribute to the risk of environmental contamination. The aim of this work was to investigate the synergistic effect of silver (Ag) and gold (Au) bimetallic nanoparticles deposited on palygorskite (PAL) in the presence of TiO₂ for photodegradation of bentazone (BTZ) herbicide under UV light. Ag and Au@Ag nanoparticles exhibited an average size below 75 nm and surface charge values less than − 30 mV. UV-Vis spectroscopy indicates the formation of core@shell bimetallic nanoparticles. XRD results showed the interactions between the NPs and the palygorskite structure. SEM images clearly illustrate the presence of small spherical particles distributed in the clay fibers. The control of the size and distribution of the nanoparticles played an important role in the properties of the composites. The degradation of the herbicide BTZ showed that nanoparticles, clay, and only TiO₂ did not produce satisfactory results; however, when Ag-Pal and Au@Ag-Pal were in the presence of the TiO₂, the degradation was efficient. The best photodegradative system was Au@Ag-Pal+TiO₂, which was maintained after the third cycle. The bentazone photodegradation using Au@Ag-PAL+TiO₂ exhibited toxicity against Artemia salina. Therefore, Au@Ag-PAL+TiO₂ photocatalyst showed that the synergy of bimetallic nanoparticles deposited on clay for enhanced photodegradation activity of bentazone herbicide.

Soil texture and soil organic carbon (OC) influence the bacterial microenvironment and also control herbicide sorption. A field-scale exploratory study was conducted to investigate the potential interaction between soil texture parameters, herbicides, and soil bacterial richness and diversity. Glyphosate and bentazon were used to evaluate the herbicidal effect on bacterial community under different conditions created by clay and OC gradients in a loamy field. Metabarcoding by high-throughput sequencing of bacterial rDNA was used to estimate bacterial richness and diversity using OTUs, abundance-based coverage (ACE), Shannon diversity index, and phylogenetic diversity. In general, bacterial richness and diversity increased after bentazon application and decreased after glyphosate application. There was no significant effect for field locations with Dexter n (the ratio between clay and OC) values below 4.04 (the median of the values in the field study). The correlation coefficient (r) between bacterial richness and clay decreased after bentazon application, but increased after glyphosate application. Correlations between Dexter n and bacterial indices followed the same pattern, decreasing after bentazon application and increasing after glyphosate application. This indicated that the specific chemical nature of individual herbicides affected bacterial communities. This study reinforced the importance of including soil physical and chemical characteristics to explain the influence of pesticides on the variation in soil bacterial communities in agroecosystems.

In a study on the behaviour of pesticides in a soil–plant–water system, the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for analysing pesticide or metabolite residues in soil and maize (leaves, roots and kernels) was optimized and validated. The pesticides bentazone, chloridazon and terbuthylazine and their metabolites bentazone-methyl, chloridazon-desphenyl, chloridazon-methyl-desphenyl, terbuthylazine-desethyl and terbuthylazine-2-hydroxy were selected in this study. The QuEChERS extracts obtained from soil and maize matrices and the collected leachate were analysed by liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS) using a high-performance liquid chromatography and an ultra-high-performance liquid chromatography (UHPLC) analytical column. As expected, shorter run times and higher sensitivity were achieved with the UHPLC column. Validation studies focused on recovery, repeatability, matrix effects, limits of detection and quantification. Recoveries (and repeatability relative standard deviation (RSD)) of the spiked samples were in the range of 55 to 98 % (7.4–18) in soil, 23 to 101 % (1.7–20) in maize and 82 to 105 % (4.4–25) in leachate. Quantification limits were lower than 3.0 μg kg⁻¹ in soil, 7.3 μg kg⁻¹ in maize and 0.080 μg l⁻¹ in leachate.

Regulators need a reliable, precise and easy to use tool for predicting the occurrence of pesticides in drain water and catchments in agricultural areas. Occurrence depends on a wide range of substance and site specific factors and this study presents a simple model built on the results from simulations of a detailed model system that does not neglect or omit any of these factors. A drainage dominated sub-catchment (0.03 km²) of the Lillebaek catchment (4.4 km²) on Funen, Denmark, represented by the catchment model MIKE SHE is considered. Detailed analyses have been made with respect to geological and hydrodynamic conditions as well as measurements of pesticide concentrations in ground and surface waters. Maximum concentrations in drain water, the time for reaching this concentration and the time interval for exceeding the limit value have been derived empirically from MIKE SHE simulations using degradation rates and sorption coefficients values for 37 pesticides included in the Danish PATE database. The relatively hydrophilic bentazon and hydrophobic pendimethalin are used as model pesticides for illustration. A simple tool applicable for a wide range of pesticides has thus been designed based on detailed analyses of a limited number of pesticides. The user requirements are degradation rates, sorption coefficients, application rates and regulatory limit values for the pesticides of interest.

This study proposed the optimization of a laccase-mediator system to reduce pesticide levels (bentazone, carbofuran, diuron, clomazone, tebuconazole, and pyraclostrobin) on aqueous medium. Firstly, the mediator concentration of 1 mM was established (average removal of 36%). After that, seven redox-mediating compounds, namely, 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, gallic acid, protocatechuic acid, and vanillin, were compared regarding their removal efficiency. The highest removal (77%) was achieved with the laccase-vanillin system. After this screening, the optimization was carried out by a 2² full factorial design. Variables under study were the enzyme (laccase) activity and vanillin concentration. Maximum removal (53–85%) was achieved with 0.95 U/mL laccase and 1.8 mM vanillin. Pesticide removal in reaction media was fitted to the first-order kinetics equation with an average half-time life of 2.2 h. This is the first study of the use of this natural compound as a mediator in the degradation of the pesticides under investigation. The results of this study contribute, with alternative methods, to decrease pesticide levels since they are highly persistent in aqueous samples and, as a result, mitigate the environmental impact.