Pesticide contamination in groundwater bodies in the Júcar River European Union Pilot Basin (SE Spain)

m-Cresol,a pesticide intermediate, induces hepatotoxicity and behavioral abnormalities in zebrafish larvae through oxidative stress, apoptosis

m-Cresol is mainly used as a pesticide intermediate. It is industrially used in the production of insecticides including boronone and fenthion. It is also an intermediate for color film, resins, plasticizers and fragrances. However, m-cresol has the potential to cause environmental contamination if released accidentally. The molecular mechanism of m-cresol mediated hepatotoxicity remains unclear. In this study, zebrafish larvae were used to comprehensively study the hepatotoxicity of m-cresol and explore its molecular mechanism. After 72 hpf of fertilization, zebrafish larvae were exposed to 0.2 mM,0.4 mM, and 0.6 mM of m-cresol. Varying degrees of liver injury and behavioral abnormalities were observed. The hepatotoxicity of zebrafish larvae may be induced by oxidative stress pathway and apoptosis of cell.

Exposure to pyrazosulfuron-ethyl induces immunotoxicity and behavioral abnormalities in zebrafish embryos

Pyrazosulfuron-ethyl is one of the most widely used herbicides in agriculture and can be widely detected in aquatic ecosystems. However, its biosafety, including its potential toxic effects on aquatic organisms and its mechanism, is still poorly understood. As an ideal vertebrate model, zebrafish, the effect of pyrazosulfuron-ethyl on early embryonic development and immunotoxicity of zebrafish can be well evaluated. From 10 to 72 h post fertilization (hpf), zebrafish embryos were exposed to 1, 5, and 9 mg/L pyrazosulfuron-ethyl which led in a substantial reduction in survival, total length, and heart rate, as well as a range of behavioral impairments. In zebrafish larvae, the number of neutrophils and macrophages was considerably decreased and oxidative stress levels increased in a dose-dependent way after pyrazosulfuron-ethyl exposure. And the expression of immune-related genes, such as TLR-4, MyD88 and IL-1β, were downregulated by pyrazosulfuron-ethyl exposure. Moreover, pyrazosulfuron-ethyl exposure also inhibited motor behavior. Notch signaling was upregulated after exposure to pyrazosulfuron-ethyl, while inhibition of Notch signaling pathway could rescue immunotoxicity. Therefore, our findings suggest that pyrazosulfuron-ethyl has the potential to induce immunotoxicity and neurobehavioral changes in zebrafish larvae.

Remediation of groundwater contaminated with dye using carbon dots technology: Ecotoxicological and microbial community responses

Groundwater pollution poses a serious threat to the main source of clean water globally. Nanoparticles have the potential for remediation of polluted aquifers; however, environmental safety concerns associated with in situ deployments of such technology include potential detrimental effects on microorganisms in terms of toxicity and functional disruptions. In this work, we evaluated a new and ecofriendly approach using carbon dots (CDs) as Fenton-like catalysts to catalyse the degradation of dye-containing groundwater samples. This investigation aimed at evaluating the efficacy of a novel remediation technology in terms of dye degradation and toxicity reduction while assessing its impacts on aquatic microorganisms. Uncontaminated Australian groundwater samples were spiked with methylene blue and incubated in the dark, at 18 °C, under slow agitation, using CDs at 0.5 mg mL^-1 and H₂O₂ at 73.5 mM for 25 h. The dye degradation rate was determined as well as the toxicity of the treated solutions using the Microtox® bioassay. Further, to determine the changes in the groundwater microbial community, 16 S rRNA sequencing was used and evenness and diversity indices were analysed using Pielou's evenness and Simpson index, respectively. This study revealed that dye-containing groundwater were effectively treated by CDs showing a degradation rate of 78-82% and a significant 4-fold reduction in the toxicity. Characterisation of the groundwater microbiota revealed a predominance of at least 60% Proteobacteria phylum in all samples where diversity and evenness were maintained throughout the remediation process. The results showed that CDs could be an efficient approach to treat polluted groundwater and potentially have minimum impact on the environmental microbiome.

Occurrence of Banned and Currently Used Herbicides, in Groundwater of Northern Greece: A Human Health Risk Assessment Approach

The presence of pesticide residues in groundwater, many years after their phase out in European Union verifies that the persistence in aquifer is much higher than in other environmental compartments. Currently used and banned pesticides were monitored in Northern Greece aquifers and a human health risk assessment was conducted. The target compounds were the herbicides metolachlor (MET), terbuthylazine (TER), atrazine (ATR) and its metabolites deisopropylatrazine (DIA), deethylatrazine (DEA) and hydroxyatrazine (HA). Eleven sampling sites were selected to have representatives of different types of wells. Pesticides were extracted by solid-phase extraction and analyzed by liquid chromatography. MET was detected in 100% of water samples followed by ATR (96.4%), DEA and HA (88.6%), DIA (78.2%) and TER (67.5%). ATR, DIA, DEA, HA, MET and TER mean concentrations detected were 0.18, 0.29, 0.14, 0.09, 0.16 and 0.15 μg/L, respectively. Obtained results were compared with historical data from previous monitoring studies and temporal trends were assessed. Preferential flow was the major factor facilitating pesticide leaching within the month of herbicide application. Moreover, apparent age of groundwater and the reduced pesticide dissipation rates on aquifers resulted of long-term detection of legacy pesticides. Although atrazine had been banned more than 18 years ago, it was detected frequently and their concentrations in some cases were over the maximum permissible limit. Furthermore, human health risk assessment of pesticides was calculated for two different age groups though drinking water consumption. In all examined wells, the sum of the HQ values were lower than the unity. As a result, the analyzed drinking water wells are considered safe according to the acute risk assessment process. However, the presence of atrazine residues causes concerns related with chronic toxicity, since ATR R values were greater than the parametric one of 1 × 10⁻⁶ advised by USEPA, for both age groups.

Overarching issues on relevant pesticide transformation products in the aquatic environment: A review

The intensification of agricultural production during the last decades has forced the rapid increase in the use of pesticides that finally end up in the aquatic environment. Albeit well-documented, pesticides continue to raise researchers' attention, because of their potential adverse impacts on the environment and, inevitably, humans. Once entering the aquatic bodies, pesticides undergo biotic and abiotic processes, resulting in transformation products (TPs) that sometimes are even more toxic than the parent compounds. A substantial shift of the scientific interest in the TPs of pesticides has been observed since their environmental fate, occurrence and toxicity is still in its formative stage. In an ongoing effort to expand the existing knowledge on the topic, several interesting works have been performed mostly in European countries, such as France, Germany, Italy, Switzerland, Greece, and Spain that counts the highest number of relevant publications. Pesticide TPs have been also studied to a lesser extent in Asia, North and South America. To this end, the main objective of this review is to delineate the global occurrence, fate, toxicity as well as the analytical challenges related to pesticide TPs in surface, ground, and wastewaters, with the view to contribute to a better understanding of the environmental problems related with TPs formation. The concentration levels of the TPs, ranging from the low ng/L to high μg/L scale and distributed worldwide. Ultimately, an attempt to predict the acute and chronic toxicity of TPs has been carried out with the aid of an in-silico approach based on ECOSAR, revealing increased chronic toxicity for the majority of the identified TPs, despite the change they underwent, while a small portion of them presented serious acute toxicity values.

Numerical Modeling of Groundwater Pollution by Chlorpyrifos, Bromacil and Terbuthylazine. Application to the Buñol-Cheste Aquifer (Spain)

Chlorpyrifos, Bromacil and Terbuthylazine are commonly used as insecticides and herbicides to control weeds and prevent non-desirable growth of algae, fungi and bacteria in many agricultural applications. Despite their highly negative effects on human health, environmental modeling of these pesticides in the vadose zone until they reach groundwater is still not being conducted on a regular basis. This work shows results obtained by version 5.08 of the Pesticide Root Zone Model (PRZM5) numerical model to simulate the fate and transport of Chlorpyrifos, Bromacil and Terbuthylazine between 2006 and 2018 inside the Buñol-Cheste aquifer in Spain. The model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. The simulation process was designed for a set of twelve scenarios considering four application doses for each pesticide. Results show that the maximum concentration value for every scenario exceeds the current Spanish Maximum Concentration Limit (0.1 μg/L). Numerical simulations were able to reproduce concentration observations over time despite the limited amount of available data.

Hepatotoxic Effects of Atrazine on Clarias gariepinus (Burchell, 1822): Biochemical and Histopathological Studies

The hepatotoxic effects of sub-lethal concentrations of atrazine (2.5, 25, 250, and 500 μg L^-1) on Clarias gariepinus juveniles were assessed for 28 days in a quality-controlled laboratory procedure. The study was designed to determine the effects of atrazine on selected liver function biomarkers: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin (ALB) and total protein (TP), and to analyze the liver tissues of the fish using a quantitative and qualitative histology-based health assessment protocol. The levels of ALB and TP in exposed specimens were observed to decrease with increasing concentrations of atrazine. However, the activities of ALT, AST, and ALP showed significant (p < 0.05) increase with increasing concentrations of atrazine. Hepatic assessment of the liver tissues revealed marked histopathological alterations, including structural changes (necrotic/apoptotic liver tissue, poor hepatic cord structure, and loss of normal architecture) in 52.2% of the liver tissues in the treatment groups; plasma alterations (vacuolation or fat inclusions, 22.9%) of hepatocytes; hypertrophied hepatocyte (55.2%); nuclear alterations (52.1%); focal necrosis (16.7%); complete degeneration of hepatocytes (60.45%); sinusoids congested with red blood cells or vascular congestion (70.8%); and karyolysis of the nucleus (18.8%). Findings from this study suggest that atrazine interferes with liver function markers and disrupts the normal architectural and structural components of the liver resulting in noninfectious liver injury. This condition resulted in repeated cycles, cell deaths, and inflammation, which could result in the eventual death of the exposed fish if exposure duration was prolonged.

Pesticides and their degradates in groundwater reflect past use and current management strategies, Long Island, New York, USA

Long Island, New York, has a mix of urban/suburban to agricultural/horticultural land use and nearly 3 million residents that rely on a sole-source aquifer for drinking water. The analysis of shallow groundwater (<40 m below land surface) collected from 54 monitoring wells across Long Island detected 53 pesticides or pesticide degradates. Maximum concentrations for individual pesticides or pesticide degradates ranged from 3 to 368,000 ng/L. The highest concentrations and most frequent pesticide detections occurred in samples collected from the pesticide management (PM) network, set in an agricultural/horticultural area in eastern Long Island with coordinated pesticide management by state and local agencies. The other two networks (Suffolk and Nassau/Queens) were set in suburban and urban areas, respectively, and had less frequent detections and lower pesticide concentrations than the PM network. Pesticide detections and concentration patterns (herbicide, insecticide, or fungicide) differed among the three networks revealing broad differences in land use. The predominance of fungicides metalaxyl, 1H-1,2,4-triazole (propiconazole/myclobutanil degradate), and 4-hydroxychlorothalonil (HCTL, chlorothalonil degradate) in samples from the PM network reflects their intensive use in agricultural settings. Total fungicide concentrations in the PM network ranged from <10 to >300,000 ng/L. The widespread detection of imidacloprid and triazine herbicides, simazine and atrazine, reveal a mixture of current and past use pesticides across the Long Island region. Low concentrations (<200 ng/L) of the triazines in the Suffolk and Nassau/Queens networks may reflect a change in land use and application. Acetanilide herbicides and aldicarb have been discontinued for 20 and 40 years, respectively, yet the concentrations of their degradates were among the highest observed in this study. Acetanilide (total concentrations up to 10,000 ng/L) and aldicarb degradates (up to 270 ng/L) are present in the PM network at much lower concentrations than previous Long Island studies and reflect changes in agricultural practices and pesticide management.

Thiophanate-methyl induces severe hepatotoxicity in zebrafish

Thiophanate-methyl (TM) is widely used all over the world and is a typical example of pesticide residues, which can be detected in the soil, and even in vegetables and fruits. However, the molecular mechanisms underlying the hepatotoxicity of TM are not well understood. In this study, we utilized zebrafish to comprehensively evaluate the hepatotoxicity of TM and explore how the molecular mechanisms of hepatotoxicity are induced. The zebrafish larvae were exposed in 6.25, 12.5 and 25 mg/L TM from 72 to 144 hpf, while the adults were exposed in 2, 4 and 6 mg/L TM for 28 days. Here, we found that 12.5 and 25 mg/L TM induces specifically serious hepatotoxicity but not the toxicity of other organs in zebrafish larvae and adults. Moreover, it might triggered hepatotoxicity by activating the caspase-3 through apoptotic pathways and oxidative stress in zebrafish. Subsequently, this resulted in a metabolic imbalance in the zebrafish's liver. In conclusion, our results disclosed the fact that TM may induce severe hepatotoxicity by mediating activation of caspase-3 and oxidative stress in zebrafish.

Determination of glyphosate and glufosinate in corn using multi-walled carbon nanotubes followed by ultra high performance liquid chromatography coupled with tandem mass spectrometry

Glyphosate (Glyp) and glufosinate (Gluf) are widely used herbicides around the world, and their effects on human health and detection of levels have drawn increasing attention. The present study was to establish a method to determine the contents of Glyp and Gluf from corn using multi-walled carbon nanotubes (MWCNTs) followed by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The corn samples were purified by MWCNTs, then the analytes reacted with 9-fluorenylmethylchloroformate (FMOCCl) of acetonitrile solution (20.0 g/L) at 50 °C water bath in a borate buffer solution (50.0 g/L, pH=9) to generate FMOC derivative products. After the derivatization, HSS T3 was used as the separation column, with acetonitrile and 0.05% ammonia as the mobile phase, and multiple reaction monitoring (MRM) mode with negative electrospray ionization (ESI-) was adopted. The validation parameters showed good verification results, with both of their quantitative limits (LOQ) as 0.005 mg/kg, recoveries between 90.3% and 95.4%, intra-day relative standard deviations (RSDs) in the ranges of 1.24% and 3.35%, and inter-day RSDs between 3.56% and 6.06%. The analytical method, developed in this study, has high accuracy and sensitivity, and is suitable for the simultaneous detection of Glyp and Gluf in corn.

Spatio-temporal distribution and ecological risk assessment of pesticides in the water resources of Abou Ali River, Northern Lebanon

The objective of this study is to assess the occurrence, spatial, and temporal distribution of forty-eight multiclass pesticides in surface and groundwater samples of the Abou Ali River, located in the North of Lebanon. A 3-year monitoring program (six batches from August 2015 to March 2017) was implemented, and thirty sampling points were selected along the river for analysis. The analysis was executed using a previously developed and optimized solid-phase micro-extraction (SPME) gas-chromatography-mass spectrometry (GC-MS) method. Statistical analysis, using Kolmogorov-Smirnov, Kruskal-Wallis, and Dunnet T3 multiple comparison tests, was applied to compare mean concentrations of pesticides between the different sampling sites and the batches taken. The pesticides that had the highest frequency of detection in the surface and groundwater samples were alachlor, α-endosulfan, and methomyl. For surface water samples, high mean concentrations were perceived for two stations in the upper stream (S5 and S7), two stations (S11 and S14) in the middle stream, and one station (S16) in the lower stream of the river. The highest mean concentrations were observed in October 2015 and August 2016, the time of the year which correlates with the period of pesticide application. Considering groundwater samples, high mean concentrations of pesticides were detected in sites G4, G9, G10, and G12 and during October 2015 and March 2016, following the rainy season. Ecotoxicological risk assessment using the risk quotient (RQ) methodology revealed high risk for five pesticides under average conditions and fourteen under extreme conditions. This study presents, for the first time, a statistical analysis showing the quantification of pesticides in the water resources of the Abou Ali River. In conclusion, it reveals the need to apply a complete pesticide monitoring program, not only for the Abou Ali River but for all the water resources in Lebanon.

Detection of herbicides in water bodies of the Samambaia River sub-basin in the Federal District and eastern Goiás

The objective of this study was to identify and quantify herbicide residues in water samples of rain, cisterns, streams, ponds, springs, semi-artesian wells, dams and a river in the Rio Samambaia sub-basin in the Federal District and eastern Goiás. A total of 287 samples were collected from 20 farms in the sub-basin in the rainy (February, summer) and dry (August, winter) seasons in 2016. Aminomethylphosphonic acid (AMPA, a glyphosate metabolite), clethodim, chlorimuron-ethyl, diuron, fluazifop acid (a fluazifop-p-butyl metabolite and the active ingredient), haloxyfop acid (a haloxyfop-methyl metabolite and the active ingredient), imazamox, mesotrione, metsulfuron, nicosulfuron and pendimethalin were not identified in any water sample. In the rainy season, approximately 99% of the samples contained residues at least one of the evaluated herbicides; in the dry season (, 100% of the samples contained residues of at least one of the evaluated herbicides. When considering only detection frequency, metribuzin, atrazine, clomazone and haloxyfop-methyl were the main herbicides found in the water of the Samambaia River sub-basin. In turn, based on levels higher than the limit of quantification, the main compounds detected were atrazine, clomazone, haloxyfop-methyl and glyphosate. In both seasons, the highest relative concentrations of herbicides for the rainy and dry seasons were found in spring water, 25% and 56%, respectively, and dam water, 23% and 16%, respectively.

Immunotoxicity and transcriptome analysis of zebrafish embryos in response to glufosinate-ammonium exposure

Glufosinate-ammonium (Gla) is a broad-spectrum and non-selective herbicide that widely used in many countries worldwide, but the biological safety including potentially negative effects on aquatic organisms remains largely unknown. In this study, we investigated the immunotoxic effects of Gla exposure on zebrafish embryos. Firstly, Gla markedly decreased the survival rate and caused a series of morphological malformations in a dose-dependent manner. Meanwhile, the number of macrophages and neutrophils was substantially reduced upon Gla exposure. In addition, the levels of oxidative stress were changed and the antioxidant enzyme activities such as CAT and SOD were elevated with the increase of Gla concentrations. Secondly, comparative transcriptome analysis identified 1, 366 differentially expressed genes (DEGs) including 789 up-regulated and 577 down-regulated in zebrafish embryos after Gla exposure. KEGG pathway analysis revealed that metabolic pathways such as drug metabolism-cytochrome P450 was markedly regulated and proteolysis, oxidation-reduction process, and peptidase activity were significantly enriched by the GO analysis. Besides, 55 immunity-related genes were identified in the DEGs, and we found that the genes in the metabolism, redox and immunity display an unique expression profilings by clustering analysis. Finally, 8 inflammatory cytokines and chemokines were further confirmed and they were differentially regulated after Gla exposure. In summary, a global survey of zebrafish defense against glufosinate was performed, and a large number of gene expression levels regarding metabolism, redox, and immunity-related genes were acquired from RNA-Seq. This study provides valuable informations for future elucidating the molecular mechanism of herbicide induced immunotoxicity in aquatic ecosystems.

Investigation of pesticides and their transformation products in the Júcar River Hydrographical Basin (Spain) by wide-scope high-resolution mass spectrometry screening

The Water Framework Directive 2000/60/EC implemented by the European Union established as the main objectives to achieve a "good ecological and chemical status" of the surface water and a "good quantitative and chemical status" of groundwater bodies. One of the major pressures affecting water bodies comes from the use of pesticides and their potential presence in the water ecosystems. For this purpose, the reliable determination of pesticides and their transformation products (TPs) in natural waters (both surface and groundwater) is required. The high number of compounds potentially reaching the aquatic environment makes extraordinary difficult, if not impossible, to investigate all these compounds even using the most powerful analytical techniques. Among these, liquid chromatography coupled to high-resolution mass spectrometry is emphasized due to its strong potential for detection and identification of many organic contaminants thanks to the accurate-mass full spectrum acquisition data. This work focuses on wide-scope screening of many pesticides and their TPs in surface water and groundwater samples, collected between March and May 2017, in the Júcar River Hydrographical Basin, Spain. For this purpose, a home-made database containing more than 500 pesticides and TPs was employed. Analyses performed by liquid chromatography coupled to quadrupole-time of flight mass spectrometry (LC-QTOF MS) allowed the identification of up to 27 pesticides and 6 TPs. The most detected compounds in groundwater were the herbicides atrazine, simazine, terbuthylazine, and their TPs (atrazine-desethyl, terbumeton-desethyl and terbuthylazine-desethyl). Regarding surface water, the fungicides carbendazim, thiabendazole and imazalil, the herbicide terbutryn and the TP terbumeton-desethyl were also detected. These results illustrate the wide use of these compounds (in the present or in the recent past) in the area under study and the vulnerability of the water bodies, and are in accordance with previous findings in other water bodies of the different Spanish Hydrographic systems.

Electrochemical removal of Terbuthylazine:Boron-Doped Diamond anode coupled with solid polymer electrolyte

Terbuthylazine (TBA) has replaced atrazine in many EU countries, becoming one of the most frequently detected pesticides in natural waters. TBA is a compound of emerging concern, due to its persistence, toxicity and proven endocrine disruption activity to wildlife and humans. Techniques applied in water treatment plants remove only partially this herbicide and poor attention is given to the generation and fate of by-products, although some of them have demonstrated an estrogenic activity comparable to atrazine. This paper summarizes the environmental occurrence of TBA and its main metabolite desethylterbuthylazine and reports the performance of an innovative electrochemical cell equipped with a solid polymer electrolyte (SPE) sandwiched between a Ti/RuO₂ cathode and a Boron-Doped Diamond anode, operating at constant current, in the treatment of an aqueous solution of TBA. The herbicide removal in the first 30 min of treatment increases from 42% to 92% as the applied current is increased from 100 to 500 mA. The rate of degradation at 500 mA decreases between 30 and 60 min, with a final abatement of 97%. An 89% removal was reached at 100 mA when the initial TBA concentration was raised from 0.1 to 4 mg L^-1 and less than 1% of the herbicide was converted in desethylterbuthylazine and minor metabolites. No chemicals are needed, no sludge is produced. Further research is encouraged, as this technology may be promising for the achievement of a zero-discharge removal of different emerging pollutants as pesticides, pharmaceuticals and personal care products.

Terbuthylazine and desethylterbuthylazine: Recent occurrence, mobility and removal techniques

The herbicide terbuthylazine (TBA) has displaced atrazine in most of EU countries, becoming one of the most regularly used pesticides and, therefore, frequently detected in natural waters. The affinity of TBA for soil organic matter suggests prolonged contamination; degradation leads to the release of the metabolite desethylterbuthylazine (DET), which has higher water solubility and binds more weakly to organic matter compared to the parent compound, resulting in higher associated risk for contamination of groundwater resources. Additionally, TBA and DET are chemicals of emerging concern because of their persistence and toxicity towards aquatic organisms; moreover, they are known to have significant endocrine disruption capacity to wildlife and humans. Conventional treatments applied during drinking water production do not lead to the complete removal of these chemicals; activated carbon provides the greatest efficiency, whereas ozonation can generate by-products with comparable oestrogenic activity to atrazine. Hydrogen peroxide alone is ineffective to degrade TBA, while UV/H₂O₂ advanced oxidation and photocatalysis are the most effective processes for oxidation of TBA. It has been determined that direct photolysis gives the highest degradation efficiency of all UV/H₂O₂ treatments, while most of the photocatalytic degradation is attributed to OH radicals, and TiO₂ solar-photocatalytic ozonation can lead to almost complete TBA removal in ∼30 min. Constructed wetlands provide a valuable buffer capacity, protecting downstream surface waters from contaminated runoff. TBA and DET occurrence are summarized and removal techniques are critically evaluated and compared, to provide the reader with a comprehensive guide to state-of-the-art TBA removal and potential future treatments.

Lignin and ethylcellulose in controlled release formulations to reduce leaching of chloridazon and metribuzin in light-textured soils

In this research, controlled release formulations (CRFs) of the herbicides chloridazon and metribuzin, identified as potential leachers, have been evaluated in soils with different texture. To prepare the CRFs, ethylcellulose (EC) and dibutylsebacate (DBS) have been used as coating agents in lignin-polyethylene glycol based formulations. Mobility experiments have been carried out in two light textured soils (sandy and sandy-loam). Breakthrough curves have shown that the use of CRFs reduces the presence of chloridazon and metribuzin in the leachate compared to technical and commercial products, being the lignin CRF coated with EC and DBS the most efficient to diminish the herbicide leaching. Mass balance study has shown a higher amount of chloridazon and metribuzin recovered in soils when these herbicides were tested as CRFs compared to technical and commercial products. The gradual release of herbicides from the CRFs resulting in a rather available levels of chloridazon and metribuzin in soil for a longer time. A good correlation between percentages of herbicide recovered in leachates and T₅₀ values (time corresponding to 50% release of herbicide in water) was obtained, which allows to select the most appropriate CRF in each agro-environmental practice to reduce the potential pollution of groundwater by chloridazon and metribuzin.

Pesticide occurrence in the waters of Júcar River, Spain from different farming landscapes

A combined methodology to identify and quantify farming chemicals in the entire Júcar River basin has been developed. The procedure consisted of the application of environmental forensic criteria associating laboratory analytical samples, cartographic analysis using Geographical Information Systems (GIS) and synthetic statistical analysis. Sampling involved the collection of 15 samples in surface waters distributed alongside the Júcar River and its two main tributaries (Cabriel and Magro Rivers). The analytical procedure involves generic sample extraction and selective determination of up to 50 target pesticides by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Geographical analysis was performed by mixing both sampling points with analytical results and land use-cover layers for the year 2011. PCA and descriptive statistical analysis was further performed combining land use/cover information and pesticides results to determine correlation between dominant agricultural practices (irrigation and rain fed farming) and location of sampling points. Out of 50 pesticides, 20 were identified and 18 presented concentrations higher than the limits of quantification in surface waters, with a large dispersion in concentrations: from 0.05ng/L (terbuthylazine-2 hydroxy) to 222.45ng/L (imazalil). Statistical analyses reveals that there is a correlation between the percentage of land devoted to irrigation farming, whereas correlations are weaker when analysing the relationship of pesticides in rain fed dominated areas.

Hydrogeological characteristics influencing the occurrence of pesticides and pesticide metabolites in groundwater across the Republic of Ireland

Pesticide contamination of water is a potential environmental issue which may impact the quality of drinking water. The full extent of pesticide contamination is not fully understood due to complex fate pathways in the subsurface. Groundwater pesticide occurrence was investigated at seven agricultural sites in different hydrogeological settings to identify where pesticide occurrence dominated in temperate maritime climatic conditions. In Ireland, six cereal dominated sites in the South East and one grassland site in the West were investigated. Soil and subsoils varied from acid brown earths with high permeability to clay and silt rich tills with lower permeability. Over a 2year monitoring period, 730 samples were collected from a network of dedicated wells and springs across the seven sites. Multi-nested piezometers were installed in intergranular, fissured and karstic type aquifers to target shallow, transition and deeper groundwaters. Several springs were also sampled and the network included a confined aquifer. Groundwater was analysed for nine pesticide active ingredients and eight metabolites. Mecoprop and 2,4-D were the most frequently detected active ingredients above the instrument detection limit, accounting for 36% and 26% of the 730 samples collected and analysed. Phenoxyacetic acid was the most frequently detected and widespread metabolite found in 39% of samples collected at all seven sites. Where the European Union drinking water standard of 0.1μg/L was exceeded, metabolites accounted for the majority of exceedances with 3,5-dichlorobenzoic acid (DBA) and phenoxyacetic acid (PAC) dominating. Highest detections were encountered in sites with well drained soils underlain by gravel and limestone aquifers and within gravel lenses in lower permeability subsoil. Across the seven sites pesticide detections were mostly associated with metabolites and the environmental impact of many of these is unknown as they have received little attention in groundwater previously.