Occurrence and Ecological Risk of Alkylamine Triazines in Chinese Estuarine Sediments: An Emerging Class of Persistent, Mobile, and Toxic Substances.

Identifying persistent, mobile, and toxic (PMT) substances from synthetic chemicals is critical for chemical management and ecological risk assessment. Inspired by the triazine analogues (e.g., atrazine and melamine) in the original European Union's list of PMT substances, the occurrence and compositions of alkylamine triazines (AATs) in the estuarine sediments of main rivers along the eastern coast of China were comprehensively explored by an integrated strategy of target, suspect, and nontarget screening analysis. A total of 44 AATs were identified, of which 23 were confirmed by comparison with authentic standards. Among the remaining tentatively identified analogues, 18 were emerging pollutants not previously reported in the environment. Tri- and di-AATs were the dominant analogues, and varied geographic distributions of AATs were apparent in the investigated regions. Toxic unit calculations indicated that there were acute and chronic risks to algae from AATs on a large geographical scale, with the antifouling biocide cybutryne as a key driver. The assessment of physicochemical properties further revealed that more than half of the AATs could be categorized as potential PMT and very persistent and very mobile substances at the screening level. These results highlight that AATs are a class of PMT substances posing high ecological impacts on the aquatic environment and therefore require more attention.

Prediction of atrazine degradation in soil based on XGBoost model.

We established the optimal model by using the automatic machine learning method to predict the degradation efficiency of herbicide atrazine in soil, which could be used to assess the residual risk of atrazine in soil. We collected 494 pairs of data from 49 published articles, and selected seven factors as input features, including soil pH, organic matter content, saturated hydraulic conductivity, soil moisture, initial concentration of atrazine, incubation time, and inoculation dose. Using the first-order reaction rate constant of atrazine in soil as the output feature, we established six models to predict the degradation efficiency of atrazine in soil, and conducted comprehensive analysis of model performance through linear regression and related evaluation indicators. The results showed that the XGBoost model had the best performance in predicting the first-order reaction rate constant (k). Based on the prediction model, the feature importance ranking of each factor was in an order of soil moisture > incubation time > pH > organic matter > initial concentration of atrazine > saturated hydraulic conductivity > inoculation dose. We used SHAP to explain the potential relationship between each feature and the degradation ability of atrazine in soil, as well as the relative contribution of each feature. Results of SHAP showed that time had a negative contribution and saturated hydraulic conductivity had a positive contribution. High values of soil moisture, initial concentration of atrazine, pH, inoculation dose and organic matter content were generally distributed on both sides of SHAP=0, indicating their complex contributions to the degradation of atrazine in soil. The XGBoost model method combined with the SHAP method had high accuracy in predicting the performance and interpretability of the k model. By using machine learning method to fully explore the value of historical experimental data and predict the degradation efficiency of atrazine using environmental parameters, it is of great significance to set the threshold for atrazine application, reduce the residual and diffusion risks of atrazine in soil, and ensure the safety of soil environment.

Swellable microneedle-coupled light-addressable photoelectrochemical sensor for in-situ tracking of multiple pesticides pollution in vivo.

In vivo monitoring of multiple pesticide contamination is of great significance for evaluating the health risks of different pesticides, agricultural production safety, and ecological and environmental assessment. Here, we report a hydrogel microneedle array coupled light-addressable photoelectrochemical sensor for tracking multiple pesticide uptake and elimination in living animals and plants, holding three prominent merits: i) enables in-situ detection of in vivo pesticides, avoiding cumbersome and complex sample transportation and handling processes; ii) allows repeated in vivo sampling of the same organism, improving tracking test controllability and accuracy; iii) avoids lethal sampling, providing a better understanding of the pesticides fate in living organisms. The coupled sensor is mechanically robust for withstanding more than 0.35 N per needle and highly swellable (800 %) for timely extraction of sufficient in vivo solution for analysis. For proof-of-concept, it achieves in-situ detection of atrazine, acetamiprid, and carbendazim efficiently and quantitatively in artificial agarose skin models, mouse skin interstitial fluids, and plant leaves with little inflammatory reaction. This simple, highly integrated, minimally invasive, and high-throughput in vivo monitoring method is ideal for future field environmental monitoring and plant and animal disease diagnosis.

Degradation of Atrazine by an Anaerobic Microbial Consortium Enriched from Soil of an Herbicide-Manufacturing Plant.

Atrazine is an important herbicide that has been widely used for weed control in recent decades. However, with the extensive use of atrazine, its residue seriously pollutes the environment. Therefore, the microbial degradation and detoxification of atrazine have received extensive attention. To date, the aerobic degradation pathway of atrazine has been well studied; however, little is known about its anaerobic degradation in the environment. In this study, an anaerobic microbial consortium capable of efficiently degrading atrazine was enriched from soil collected from an herbicide-manufacturing plant. Six metabolites including hydroxyatrazine, deethylatrazine, N-isopropylammelide, deisopropylatrazine, cyanuric acid, and the novel metabolite 4-ethylamino-6-isopropylamino-1,3,5-triazine (EIPAT) were identified, and two putative anaerobic degradation pathways of atrazine were proposed: a hydrolytic dechlorination pathway is similar to that seen in aerobic degradation, and a novel pathway initiated by reductive dechlorination. During enrichment, Denitratisoma, Thiobacillus, Rhodocyclaceae_unclassified, Azospirillum, and Anaerolinea abundances significantly increased, dominating the enriched consortium, indicating that they may be involved in atrazine degradation. These findings provide valuable evidence for elucidating the anaerobic catabolism of atrazine and facilitating anaerobic remediation of residual atrazine pollution.

Coinoculation of arbuscular mycorrhizal fungi and rhizobia stimulates atrazine dissipation by changing the atrazine-degrading bacterial community at the soil aggregate scale.

As a potential low-cost and environmentally friendly strategy, bioremediation of herbicide polluted soil has attracted increasing attention. However, there is a lack of knowledge regarding the response of the atrazine-degrading bacterial community to coinoculation of arbuscular mycorrhizal (AM) fungi and rhizobia for atrazine dissipation. In this study, a pot experiment was conducted with AM fungi Glomus mosseae (AM), rhizobia Rhizobium trifolii TA-1 (R) and their coinoculation (AMR) with atrazine. In each treatment, the atrazine-degrading bacterial community of four soil size aggregates, namely large macroaggregates (LMa), small macroaggregates (SMa), microaggregates (Mia) and primary particles (P) were investigated. The results showed that the atrazine residue concentration was lowest in AMR, and that in LMa was also significantly lower than that in the other smaller aggregate sizes. Overall, inoculation, the aggregate fraction and their interaction had significant effects on soil TN, SOC, AP and pH. For the atrazine-degrading bacterial community, the Chao1 index increased with decreasing particle size, but the Shannon index decreased. Moreover, the abundances of the dominant atrazine-degrading bacterial genera Arthrobacter, Bacillus, Marmoricola and Nocardioides in the Mia and P particle size groups were greater than those in the LMa and SMa groups in each treatment. The bacterial communities in the Mia and P particle sizes in each treatment group were more complex. Therefore, coinoculation of AM fungi and rhizobia stimulated atrazine dissipation by changing the atrazine-degrading bacterial community, and the response of the atrazine-degrading bacterial community to each aggregate size varied depending on its distinct soil physicochemical properties.

Degradation of atrazine, glyphosate, and 2,4-D in soils collected from two contrasting crop rotations in Southwest Chaco, Argentina.

Argentina stands as one of the leading consumers of herbicides. In a laboratory incubation experiment, the persistence and production of degradation metabolites of Atrazine, 2,4-D, and Glyphosate were investigated in a loamy clay soil under two contrasting agricultural practices: continuous soybean cultivation (T1) and intensified rotations with grasses and legumes (T2). The soils were collected from a long-term no-till trial replicating the influence of the meteorological conditions in the productive region. The soil was enriched with diluted concentrations of 6.71, 9.95, and 24 mg a.i./kg-1 of soil for the respective herbicides, equivalent to annual doses commonly used in the productive region. Samples were taken at intervals of 0, 0.5, 1, 2, 4, 6, 8, 16, 32, and 64 days, and analysis was conducted using high-resolution liquid chromatography UPLC MS/MS. An optimal fit to the first-order kinetic model was observed for each herbicide in both rotations, resulting in relatively short half-lives. Intensified crop sequences favored the production of biotic degradation metabolites. The impact of the high frequency of soybean cultivation revealed a trend of soil acidification and a reduced biological contribution to attenuation processes in soil contamination.

Characteristics of bacterial community and extracellular enzymes in response to atrazine application in black soil.

The ecological functioning of black soil largely depends on the activities of various groups of microorganisms. However, little is known about how atrazine, a widely used herbicide with known harmful effects on the environment, influences the microbial ecology of black soil, and the extracellular enzymes related to the carbon, nitrogen and phosphorus cycles. Here, we evaluated the change in extracellular enzymes and bacterial community characteristics in black soil after exposure to various concentrations of atrazine. Low concentrations of applied atrazine (10 - 20 mg kg-1) were almost completely degraded after 120 days. At high concentrations (80 - 100 mg kg-1), about 95% of the applied atrazine was degraded over the same period. Additionally, linear fitting of data indicated that the total enzymatic activity index (TEI) and bacterial α-diversity index were negatively correlated with atrazine applied concentration. The atrazine had a greater effect on bacterial beta diversity after 120 days, which differentiated species clusters treated with low and high atrazine concentrations. Soil bacterial community structure and function were affected by atrazine, especially at high atrazine concentrations (80 - 100 mg kg-1). Key microorganisms such as Sphingomonas and Nocardioides were identified as biomarkers for atrazine dissipation. Functional prediction indicated that most metabolic pathways might be involved in atrazine dissipation. Overall, the findings enhance our understanding of the factors driving atrazine degradation in black soil and supports the use of biomarkers as indicators of atrazine dissipation.

Exposure to atrazine by drinking water and the increased risk of neonatal complications in consequence: a meta-analysis.

This meta-analysis evaluates the association between atrazine (ATR) exposure and small for gestational age (SGA), preterm birth (PTB), and low birth weight (LBW). A comprehensive search was done on academic databases (e.g. PubMed, Scopus, Embase, and Google Scholar) to achieve all pertinent studies up to May 2023. A pooled odd ratio (OR) and corresponding 95% confidence interval (CI) were applied to evaluate this correlation. As a result, five eligible studies met the inclusion criteria and were included in our study, and the result of the present meta-analysis showed that ATR exposure increased the risk of SGA (OR = 1.11; 95% CI = 1.03-1.20 for highest versus lowest category of ATR), PTB (OR = 1.16; 95% CI = 1.03-1.30), and LBW (OR = 1.26; 95% CI = 1.10-1.44). This meta-analysis suggests that ATR in drinking water may be a risk factor for SGA, PTB, and LBW.

Carbon and hydrogen isotopic evidence for atrazine degradation by electro-activated persulfate: Radical contributions and comparisons with heat-activated persulfate.

The activation ways of persulfate (PS) were dominate for pollutant degradation and energy consumption. For the first time, this research compared electro-activated PS and heat-activated PS from the perspective of isotope fractionation, in order to "fingerprinted" and precisely interpretate reaction contributions and degradation pathways. As results, PS can be electrochemically activated with atrazine (ATZ) removal rates of 84.8% and 88.8% at pH 4 and 7. The two-dimensional isotope plots (ɅC/H) values were 6.20 at pH 4 and 7.46 at pH 7, rather different from that of SO4·- -dominated process with ɅC/H value of -4.80 at pH 4 and -23.0 at pH 7, suggesting the weak contribution of SO4·-. ATZ degradation by electro-activated PS was controlled by direct electron transfer (DET) and ·OH radical, and ·OHPS (derived from PS activation) played the crucial role with contributing rate of 63.2%-69.1%, while DET and ·OHBDD (derived from electrolysis of H2O) contributed to 4.5-7.9% and 23.0%-30.8%, respectively. This was different from heat activation of PS, of which the latter was dominated by SO4·- with contributions of 83.9%-100%. The discrepant dominating reactive oxygen species should be responsible for their different degradation capabilities and pathways. This research provided isotopic interpretations for differences of PS activation mode, and further efforts can be made to realize the selective degradation by enhancing the specific reaction process.

Fluorometric Assay of Tyrosinase and Atrazine Based on the Use of Carbon Dots and the Inhibition of Tyrosinase Activity.

Sensitive and convenient strategy of tyrosinase (TYR) and its inhibitor atrazine is in pressing demand for essential research as well as pragmatic application. In this work, an exquisite label-free fluorometric assay with high sensitivity, convenience and efficiency was described for detecting TYR and the herbicide atrazine on the basis of fluorescent nitrogen-doped carbon dots (CDs). The CDs were prepared via one-pot hydrothermal reaction starting from citric acid and diethylenetriamine. TYR catalyzed the oxidation of dopamine to dopaquinone derivative which could quench the fluorescence of CDs through a fluorescence resonance energy transfer (FRET) process. Thus, a sensitive and selective quantitative evaluation of TYR can be constructed on the basis of the relationship between the fluorescence of CDs and TYR activity. Atrazine, a typical inhibitor of TYR, inhibited the catalytic activity of TYR, leading to the reduced dopaquinone and the fluorescence was retained. The strategy covered a broad linear range of 0.1-150 U/mL and 4.0-80.0 nM for TYR and atrazine respectively with a low detection limit of 0.02 U/mL and 2.4 nM/mL. It is also demonstrated that the assay can be applied to detect TYR and atrazine in spiked complex real samples, which provides infinite potential in application of disease monitoring along with environmental analysis.

Bio-engineered sensing of Atrazine by green CdS quantum dots: Evidence from electrochemical studies and DFT simulations.

The present investigation reports a comprehensible and responsive strategy for identifying atrazine in several conditions using an extensive electrochemical method. CdS Quantum dots were synthesized via a greener approach, and their formation was endorsed by numerous characterization techniques such as FTIR, SEM, Raman, UV-Vis, and XRD. Owing to the splendid electrocatalytic behavior, Green CdS quantum dots (QDs) of crystallite size ∼2 nm was opted as the sensor material and were, therefore, incorporated on the bare carbon paste electrode's surface. The developed sensor demonstrated an impressive outcome for atrazine sensing accompanied by superior selectivity and sensitivity. The lower detection limit (LLOD) of 0.53 µM was attained using the developed sensor in a linear concentration range of 10-100 µM. Furthermore, the practical pertinence of the developed sensor was examined on distilled water, wastewater, and fresh liquid milk, resulting in a tremendous retrieval of atrazine (91.33-99.8%).

Bioinformatics analysis of the potential mechanisms of Alzheimer's disease induced by exposure to combined triazine herbicides.

BACKGROUND: The development of Alzheimer's disease (AD) is promoted by a combination of genetic and environmental factors. Notably, combined exposure to triazine herbicides atrazine (ATR), simazine (SIM), and propazine (PRO) may promote the development of AD, but the mechanism is unknown. AIM: To study the molecular mechanism of AD induced by triazine herbicides. METHODS: Differentially expressed genes (DEGs) of AD patients and controls were identified. The intersectional targets of ATR, SIM, and PRO for possible associations with AD were screened through network pharmacology and used for gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis. The binding potentials between the core targets and herbicides were validated by molecular docking and molecular dynamics. RESULTS: A total of 1,062 DEGs were screened between the AD patients and controls, which identified 148 intersectional targets of herbicides causing AD that were screened by network pharmacology analysis. GO and KEGG enrichment analysis revealed that cell cycling and cellular senescence were important signalling pathways. Finally, the core targets EGFR, FN1, and TYMS were screened and validated by molecular docking and molecular dynamics. CONCLUSION: Our results suggest that combined exposure to triazine herbicides might promote the development of AD, thereby providing new insights for the prevention of AD.

Human health risk assessment based on direct and indirect exposure to endocrine disrupting herbicides in drinking, ground, and surface water in Croatia.

The recognition of certain herbicides as endocrine disrupting compounds has raised concerns due to their ability to interfere with the normal functioning of the endocrine system, which regulates various physiological processes in organisms. The objective of this study was to assess the possible human health risks associated with terbuthylazine and endocrine-disrupting herbicides atrazine, acetochlor, and metolachlor in the drinking, surface, and groundwater of the Zagreb city region, Croatia. We relied on advanced statistical methods and principal component analysis (PCA), which revealed higher levels of atrazine and acetochlor in drinking and groundwater samples and higher presence of metolachlor and terbuthylazine in surface waters. To evaluate the danger to human health, various exposure scenarios have been assessed. The risk of direct human exposure to analyzed herbicides through drinking or bathing with drinking (tap) or groundwater, as well as from recreational activities like swimming in rivers, streams, and lakes, has been quantified. In addition to these direct exposure scenarios, indirect ones based on consumer goods, fruits, and vegetables, treated with surface and groundwater for irrigation, were assessed to investigate the danger to human health. Judging by the reported herbicide levels there was no significant risk of carcinogenic (CR ≤ 1 × 10-6) or non-carcinogenic (HI < 1) diseases, not even when we assessed the so-called "cocktail effect" of combined the herbicide exposure in different waters.

Bioaccumulation of pesticide residue in earthworms collected from the agricultural soils of Kuttanad-a unique agroecosystem in India.

Earthworms encompass significant soil faunal biomass and have tremendous potential to provide vital ecosystem services. Earthworms are considered bioindicators of chemical contaminants and can provide early warnings of ecosystem deterioration. Studies pertaining to the accumulation of pesticide residues in earthworm in biomass in agrarian ecosystems are scarce. The Kuttanad agroecosystem (KAE), situated on the southwest coast of India, is one of the few regions globally supporting farming on land below the mean sea level. This investigation was conducted to assess the bioaccumulation of pesticide residues in earthworms from the KAE. The earthworms species Glyphidrilus annandalei collected from agricultural soils of the study area were analyzed for the presence of pesticides residues such as α-BHC, γ-BHC, atrazine, heptachlor, α-chlordane, γ-chlordane, 4,4-DDE, 4,4-DDD, 4,4-DDT, ß-endosulfan, and endrin ketone in their biomass. Analysis of the earthworm samples using a gas chromatograph revealed the presence of ten pesticide residues with notable concentrations (α-BHC, 0.36 ng/g; γ-BHC, 0.41 ng/g; heptachlor, 0.10 ng/g; atrazine, 0.89 ng/g; α-chlordane, 0.07 ng/g; γ-chlordane, 0.10 ng/g; 4,4-DDE, 0.05 ng/g; 4,4-DDD, 0.11 ng/g; 4,4-DDT, 0.31 ng/g; ß-endosulfan, 0.19 ng/g; and endrin ketone, 0.13 ng/g). Six groups of pesticide residues are ΣBHC, ΣDDT, atrazine, Σchlordane, endrin ketone, and ß-endosulfan were observed during bioaccumulation factor analysis, and the results show the following trend: atrazine > ΣBHC > ΣDDT > Σchlordane > Σendosulfan > Σendrin. As earthworms are a crucial component of this region's food chains, bioaccumulation of pesticide residues in earthworms can pause adverse consequences. Increasing trends in pesticide application in the KAE and bioaccumulation of pesticide residues in earthworm biomass can affect the entire food web.

Pollution characteristics, ecological and health risks of herbicides in a drinking water source and its inflowing rivers in North China.

This study measured the pollution characteristics and ecological and health risks of 19 herbicides found in drinking water sources and their inflowing rivers. The targeted herbicides were prevalent in the study area, but most concentrations were well below 10 ng L-1. Acetochlor and atrazine were the dominant herbicides, although their levels were much lower than previously reported. Total herbicide residual levels were greater in April than in December and increased from upstream to downstream, resulting in the highest pollution levels found in the reservoirs, likely due to herbicides delivered from upstream and dense agricultural planting in the surrounding areas. Only atrazine and ametryn presented moderate ecological risks, while the summed risk quotients (ΣRQs) of each sample were >0.1, indicated that the total herbicide levels represented a moderate risk in all samples. For the human health risks, the risk quotients (RQ) of all target herbicides, the total RQs of each sample, and estimated life-stage RQs were far smaller than the 0.2 threshold, indicating the absence of human health risks when the water was consumed at any stage of life. However, early life stages exhibited 3-6 times higher RQ values than adulthood and should not be overlooked. And crucially, the synergistic or antagonistic effects of mixed herbicides are not well understood, and further research is needed to understand the impact of these herbicides on the ecosystem and human health, particularly possible affects in early life stages, such as infants and children.

Promoted dissipation and detoxification of atrazine by graphene oxide coexisting in water.

The herbicide atrazine (ATZ) has a detrimental effect on the health of aquatic ecosystems and has become a global concern in recent years. But the understanding of its persistence and potential toxicity under combined pollution, especially in the coexistence of other emerging pollutants, remains limited. In this work, the dissipation and transformation of ATZ in combination with graphene oxide (GO) in water were investigated. Results showed that dissipation rates of ATZ dramatically increased by 15-95% with half-lives shortened by 15-40% depending on initial concentrations of ATZ, and the products were mainly toxic chloro-dealkylated intermediates (deethylatrazine (DEA) and deisopropylatrazine (DIA)), but their contents were significantly lower under the coexistence of GO compared to ATZ alone. In the presence of GO, the nontoxic dechlorinated metabolite hydroxyatrazine (HYA) was detected earlier than 2-9 days, and ATZ transformation into HYA was increased by 6-18% during 21-day incubation periods. This study indicated that the coexistence of GO enhanced the dissipation and detoxification of ATZ. From a remediation standpoint, GO-induced hydrolytic dechlorination of ATZ can reduce its ecological toxicity. But the environmental risks of ATZ for aquatic ecosystem under the coexistence of GO should still be given the necessary prominence due to the potential hazard of ATZ adsorbed on GO and the predominant degradation products (DEA and DIA).

Atrazine decontamination by a newly screened psychrotroph Paenarthrobacter sp. KN0901 in an aquatic system: Metabolic pathway, kinetics, and hydroponics experiment.

Atrazine residues running off the fields and entering water resources are a major threat to food security and the ecosystem. In this study, a psychrotrophic functional strain named KN0901 to remove atrazine residues was screened. KN0901 could degrade 30 mg·L-1 atrazine in 4 days at 15ºC with 105 CFU·mL-1 incubation. The phylogenetic results showed KN0901 belonged to Paenarthrobacter sp. PCR results showed that the functional genes consist of trzN, atzB, and atzC, suggesting atrazine was transformed to cyanuric acid by KN0901. KN0901 could degrade atrazine without adding exogenous carbon and nitrogen sources. What's more, KN0901 could tolerate extreme low temperature (5ºC) and high atrazine concentration (100 mg·L-1). When growth and degradation curves were compared, the results indicated the length of lag time showed significant correlation to atrazine degradation rate. The hydroponic experiments showed that the toxicity of atrazine was significantly reduced with KN0901 treatment. The study provided an effective, economic, and eco-friendly bioremediation measure to address atrazine contamination.

Treatment of atrazine-containing wastewater by algae-bacteria consortia: Signal transmission and metabolic mechanism.

Atrazine is a toxic endocrine disruptor. Biological treatment methods are considered to be effective. In the present study, a modified version of the algae-bacteria consortia (ABC) was established and a control was simultaneously set up to investigate the synergistic relationship between bacteria and algae and the mechanism by which atrazine is metabolized by those microorganisms. The total nitrogen (TN) removal efficiency of the ABC reached 89.24% and the atrazine concentration was reduced to below the level recommended by the Environment Protection Agency (EPA) regulatory standards within 25 days. The protein signal released from the extracellular polymeric substances (EPS) secreted by the microorganisms triggered the resistance mechanism of the algae, and the conversion of humic acid to fulvic acid and electron transfer constituted the synergistic mechanism between the bacteria and algae. The mechanism by which atrazine is metabolized by the ABC mainly consists of hydrogen bonding, H-pi interactions, and cation exchange with atzA for hydrolysis, followed by a reaction with atzC for decomposition to non-toxic cyanuric acid. Proteobacteria was the dominant phylum for bacterial community evolution under atrazine stress, and the analysis revealed that the removal of atrazine within the ABC was mainly dependent on the proportion of Proteobacteria and the expression of degradation genes (p < 0.01). EPS played a major role in the removal of atrazine within the single bacteria group (p < 0.01).

Atrazine and its degradation products in drinking water source and supply: Risk assessment for environmental and human health in Campinas, Brazil.

Atrazine is a broad-spectrum herbicide widely used worldwide to control grassy and broadleaf weeds. Atrazine's popularity is attributable to its cost-effectiveness and reliable performance. Relatedly, it is also an important micropollutant with a potential negative impact on biodiversity and human health. Atrazine has long been regularly detected in several environmental compartments, and its widespread use has resulted in ubiquitous and unpreventable contamination. Among pesticides sold in Brazil, atrazine has remained among the top-ranked active ingredients for the last several years. Thus, this study aimed to evaluate the occurrence of atrazine and three degradation products (hydroxyatrazine, desisopropylatrazine, and desethylatrazine) in surface water (Capivari and Atibaia rivers) and treated water, monthly sampling from two drinking water treatment plants in Campinas (São Paulo, Brazil). An analytical method using solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed to determine target compounds simultaneously. The method presented instrument quantification limits from 0.5 to 4.0 ng mL-1 and recovery values from 80 to 112%, with a maximum relative standard deviation of 6%. All analytes had a detection frequency of 100% from 2 to 2744 ng L-1. Statistical analysis showed no analyte removal after conventional water treatment. Also, the Capivari River showed greater analyte concentration than the Atibaia River. Performed risk assessments according to current Brazilian standards showed no human and environmental health risks. However, other risk assessment approaches may indicate potential risks, advocating for further research and ongoing surveillance.

Degradation pathways of atrazine by electrochemical oxidation at different current densities: Identifications from compound-specific isotope analysis and DFT calculation.

Current density was the key factor that impacted pollutant degradation by electrochemical oxidation, and reaction contributions at various current densities were non-negligible for the cost-effective treatments of organic pollutants. This research introduced compound specific isotope analysis (CSIA) into atrazine (ATZ) degradation by boron doped diamond (BDD) with current density of 2.5-20 mA/cm2, in order to provide "in-situ" and "fingerprint" analysis of reaction contributions with changed current densities. As results, the increased current density displayed a positive impact on ATZ removal. The ɅC/H values (correlations of Δδ13C and Δδ2H) were 24.58, 9.18 and 8.74 when current densities were 20, 4, and 2.5 mA/cm2, with ·OH contribution of 93.5%, 77.2% and 80.35%, respectively. While DET process favored lower current density with contribution rates up to ∼20%. What's more interesting, though the carbon and hydrogen isotope enrichment factors (εC and εH) were fluctuate, the ɅC/H linearly increased accompanied with applied current densities. Therefore, increasing current density was effective due to the larger ·OH contribution even though side reactions may occur. DFT calculations proved the increase of C-Cl bond length and the delocalization of Cl atom, confirming dechlorination reaction mainly occurred in the direct electron transfer process. While ·OH radical mainly attack the C-N bond on the side chain, which was more benefit to the fast decomposition of ATZ molecule and intermediates. It was forceful to discuss pollutant degradation mechanism by combining CSIA and DFT calculations. Target bond cleavage (i.e., dehalogenation reaction) can be conducted by changing reaction conditions like current density due to the significantly different isotope fractionation and bond cleavage.