Paraquat Concentration Research Articles

Risk Assessment and Protective Effect of Respirators on Airborne Paraquat Exposure during Simulated Spraying Operations

Paraquat (PQ) is widely used as a herbicide in Thailand. The aim of this study was to evaluate the health risk and protective effect of respirators during simulated PQ spraying operations in an experimental chamber. Additional data were collected from the interviews of PQ sprayers. Airborne PQ concentrations were collected from an experimental spray chamber employing controlled-rate sprayers of solutions (paraquat dichloride in water) and were lower than 50 µg/m3 (the standard regulation). Air sampling through a polytetrafluoroethylene filter membrane was performed under the conditional settings of inside and outside respirators, and analysed by using a HPLC-UV detector following NIOSH method 5003. The average PQ concentrations inside the certified respirators (cartridge, cup-shaped mask, surgical mask) were significantly lower than those outside of the respirators (4.30 ± 2.63 µg/m3 vs. 19.12 ± 16.65 µg/m3), which was not found with convenient sponge masks. Human health risk assessment on short-term and long-term exposure following US.EPA guide estimation showed that cartridge respirators and cup-shaped masks significantly decreased the risk (hazard quotient) of adverse health effects (p-value < 0.05) among the PQ sprayers. As a result, the PQ sprayers should be aware of preventive action and use a qualified mask/respirator to protect against exposure to airborne PQ and chronic health effects.
 HIGHLIGHTS
 
 The estimated human health risk from paraquat (PQ) exposure lower than the occupational exposure limit (OEL: 50 µg/m3) during the spraying operation was unacceptable for some sprayers
 The average PQ concentrations inside the certified respirators (cartridge respirator and cup-shaped mask) were significantly lower than outside of the respirators that was not seen with the convenient sponge mask, a common type used by the sprayers
 The cartridge respirator and cup-shaped mask significantly decreased the risk estimation of the PQ sprayers with regard to adverse health effects both from short-term and long-term PQ exposure
 It is important for preventive action on exposure to PQ of the sprayers by the use of qualified respirators or masks to protect against inhalation of PQ and decrease health risks
 
 GRAPHICAL ABSTRACT

Highly Stable Photocatalytic Removal of Paraquat Dichloride using ZnO/TiO2 supported on PVC

This study presents on ZnO/TiO2 supported on PVC (ZnO/TiO2@PVC) in the photocatalytic removal of paraquat dichloride. The ZnO/TiO2@PVC was characterized using XRD, FESEM-EDX, FTIR, and AFM. Findings indicated that ZnO/TiO2@PVC allowed degradation of paraquat dichloride under UV irradiation by the rate of up to 73%. XRD pattern indicated the presence of both TiO2(anatase) and ZnO (zincite) crystalline as well as PVC amorphous structures. FESEM and AFM results revealed the observed shape and surface of TiO2 interconnected nanowires with ZnO nanorods uniformly distributed according to EDX mapping. The reduced surface roughness was also shown in the supported photocatalyst. FTIR analysis clearly demonstrate the combined spectra of immobilised ZnO/TiO2 powder catalyst onto the PVC in the composite. Kinetic study of the degradation process was performed according to pseudo-first-order and the influence of ZnO/TiO2 coating onto PVC polymer and initial paraquat concentration were investigated on the treatment performance. Under optimized condition (pH = 7, PQ =20 mg/L and catalyst coating =15%), the stability and reusability of the supported catalyst was also evaluated over ten sequential treatment runs, and the catalyst maintain high reactivity. High recyclability of the ZnO/TiO2@PVC composites as catalyst in photodegradation processes are also reported in this study.

Experimental design for the optimization of paraquat removal from aqueous media using a fixed-bed column packed with Pinus Eldarica stalks activated carbon

In this study, a fixed-bed column packed with an activated carbon (Pinus eldarica stalks (PES-AC)) was used to evaluate the performance of paraquat removal from wastewater. The effect of bed height, initial paraquat concentration, contact time, flow rate on the removal of paraquat was investigated using response surface methodology (RSM) based on central composite design (CCD). From the RSM model, the optimum experimental conditions to achieve 94.65% removal of paraquat were solution pH of 8.0, 6 mg L−1 of paraquat, 4 mL min−1 of flow rate, 0.8 cm of the bed height, and 40 min of contact time. The breakthrough data were significantly fitted with Thomas, bed depth services time (BDST), and Yoon–Nelson models. The high values of NBD (14.33, 32.29, and 54.46 mg L−1) and critical bed depth (0.396, 0.370, and 0.330 cm) obtained from BDST model revealed the high efficiency and suitability of the adsorbent. Adsorption of paraquat on PES-AC was strongly dependent on solution pH, indicating an electrostatic attraction mechanism.

Determination of Paraquat (Herbicide) Residue Level in Sandy Clay Loam Soil Using High Performance Liquid Chromatography

Pesticide is considered as the most widely used form of agricultural chemical. Pesticide residue is the remaining pesticide on or in soil after pesticide is applied on agriculture soil. Soil is a component that is crucial to life. The research purposely concerned on major effects that could be contributed from medium to unlimited application of pesticide. The soil samples were systematically collected from 5 plots and Paraquat residues concentrations were determined in dissimilar depth of soil layers. The herbicide used was Paraquat that contained Paraquat Dichloride. High Performance Liquid Chromatography (HPLC) analysis detected the peak area volumes of Paraquat in soil samples at level ranging from 0.3 to 5.9 mg/l. The concentration of Paraquat in sandy clay loam soil showed that herbicide leached downward to the depth of 15 cm. The maximum concentration of Paraquat residue was detected at 0 to15 cm of soil depth at 2.783 mg/l. In highly organic soils, adsorption is weaker and Paraquat remains herbicidally active for longer, up to 29 days in one trial on soil with 98% organic matter [1]. Oral dose, LD50 for human is equal to 40-60 mg/kg [2] while the lowest fatal dose recorded for human was 17 mg/kg, but even lower doses may be fatal for children [3].

Anthrahydroquinone-2-6-disulfonate is a novel, powerful antidote for paraquat poisoning

Paraquat (PQ) is a widely used fast-acting pyridine herbicide. Accidental ingestion or self-administration via various routes can cause severe organ damage. Currently, no effective antidote is available commercially, and the mortality rate of poisoned patients is exceptionally high. Here, the efficacy of anthrahydroquinone-2-6-disulfonate (AH2QDS) was observed in treating PQ poisoning by constructing in vivo and ex vivo models. We then explored the detoxification mechanism of AH2QDS. We demonstrated that, in a rat model, the PQ concentration in the PQ + AH2QDS group significantly decreased compared to the PQ only group. Additionally, AH2QDS protected the mitochondria of rats and A549 cells and decreased oxidative stress damage, thus improving animal survival and cell viability. Finally, the differentially expressed genes were analysed in the PQ + AH2QDS group and the PQ group by NextGen sequencing, and we verified that Nrf2’s expression in the PQ + AH2QDS group was significantly higher than that in the PQ group. Our work identified that AH2QDS can detoxify PQ by reducing PQ uptake and protecting mitochondria while enhancing the body's antioxidant activity.

Dichlorvos and Paraquat induced spatial avoidance response: A more realistic determinant of population decline of Oreochromis niloticus

The present study evaluated the ability of Dichlorvos and Paraquat to provoke avoidance response in fingerlings of Nile tilapia Oreochromis niloticus and estimate the population immediate decline (PID). The non-forced multi-compartmented system used for non-forced assays, were constructed to allow free movement of fishes along six compartments. Fishes (n=3 per compartment/treatment, totaling 18 per system) were exposed to a gradient of Dichlorvos (1.0, 2.0, 4.0, 5.0 and 6.0 mg L-1) and Paraquat (10.0, 30.0, 50.0, 70.0, 100.0 mg L-1) and their distribution were recorded at 20 min interval for a 3-h period. Mortalities recorded in forced exposures were 17% and 0% at lowest concentrations and, 67% and 83% at highest concentrations for Dichlorvos and Paraquat correspondingly. For non-forced exposure, fishes presented a significant (p < 0.005) gradient-dependent spatial avoidance for both pesticides after 3-h. They avoided the lowest concentrations of Dichlorvos and Paraquat (1.0 and 10.0 mg L-1) by 40% and 90% respectively and 100% at the highest concentrations for both pesticides. The PID was driven by avoidance behavior rather than mortality. This result indicates that the dangers of pesticide contamination is not only in their toxicity to organisms, but also, in habitat selection processes by organism resulting in serious environmental turbulence.

Verbascoside inhibits paraquate-induced pulmonary toxicity via modulating oxidative stress, inflammation, apoptosis and DNA damage in A549 cell

Paraquat (PQ), one of the most frequently used herbicides, can cause serious health problems in an exposed individual. In the present study, we investigated the protective effect of verbascoside (VB), a phenylpropanoid glycoside from lemon verbena, against PQ-induced A549 cell injury with a particular focus on the possible molecular pathways involved. A549 cells were exposed to PQ (300 µM) and different concentrations of VB (12.5, 25, and 50 µM). Cell viability, ROS content, the level of antioxidant enzymes (SOD, CAT and GPx) and inflammatory markers (IL-6 and TNF-α), as well as 8-OHdG, were detected using MTT assay and an ELISA kit. Western blotting and qRT-PCR were performed to measure the levels of caspase3 and NF-κB mRNA and protein expression. Exposure of cells to PQ caused viability loss and ROS increase. PQ also increased the levels of IL-6, TNF-α and 8-OHdG and decreased the antioxidant enzymes content. PQ treatment resulted in cell death by increasing the gene and protein expression level of caspase 3 and NF-κB. Treatment with VB notably increased cell survival, antioxidant enzymes activity, which concomitantly attenuated ROS, NF-κB and inflammatory mediator production. VB also inhibited apoptosis expression markers. These results indicated that VB could protect A549 cells against PQ induced cell injury by attenuation of ROS and inflammatory marker production and modulation of antioxidant enzymes. VB efficiently suppressed increased NF-κB and caspase-3 activity and formation of 8-OHdG and ultimately improved cell viability. Therefore, VB may be useful in the development of a new therapy for PQ-induced pulmonary toxicity.

A novel flowchart to predict mortality and analyse effectiveness of routinely used pharmacological regimens in paraquat poisoning.

Paraquat is responsible for an extremely high case-fatality rate poisoning. Mortality prediction remains a major issue since evidence to support benefits of routinely used treatments is lacking. We aimed to develop an easy-to-use prediction flowchart not requiring the ingestion time, for which accuracy is frequently questionable, and to evaluate the effectiveness of routinely used pharmacological therapies on mortality. We designed a two-centre cohort study including consecutive paraquat-poisoned adults with confirmed diagnosis based on serum/urine paraquat measurement. We built a flowchart using a multivariate analysis of death predictors and analysed the outcome according to the administered therapies. Overall, 256 patients were enrolled. Mortality rate was 75%. Independent death predictors on admission were serum creatinine (odds ratio [OR], 5.07; 95% confidence interval [CI], 1.97-13.05) and serum paraquat concentration (OR, 2.26; CI, 1.66-3.09). The area-under-the flowchart curve was 0.91. Overall sensitivity and specificity were 81.5% and 94.8%, respectively. More survivors than non-survivors of severe poisoning received methylprednisolone (P = 0.04). While not significantly differing in severity, methylprednisolone-treated patients had better survival (P = 0.04). To conclude, we defined an efficient flowchart to predict mortality in paraquat poisoning at presentation, even if ingestion time is undetermined. Methylprednisolone seems effective to improve the outcome, especially in the most severe cases.

The acute paraquat poisoning mortality (APPM) score to predict the risk of death in paraquat-poisoned patients

Context Mortality prediction in paraquat poisoning is a major issue since most prediction rules are inapplicable if the exact ingestion time cannot be determined and/or the serum paraquat concentration is not readily available, as in most countries. Therefore, we aimed to develop and validate a new prediction rule not requiring these two parameters. Methods We designed a 10-year observational cohort study including all consecutive paraquat-poisoned patients managed in two Taiwanese hospitals. We built one cohort to define and one cohort to validate this prediction rule. Parameters independently related to mortality determined using a multivariate analysis were used to formulate the Acute Paraquat Poisoning Mortality (APPM) score. Results Overall, 321 paraquat-poisoned patients were included, 156 in the derivation and 165 in the validation cohort. Mortality rates in the derivation and validation cohorts were 73% and 81%, respectively (p = 0.20). The three parameters chosen of 28-day mortality at presentation were urine paraquat level >10 ppm (using a colorimetric sodium dithionite-based test; odds ratio (OR), 12.70; 95% confidence interval (CI), 2.64–61.24), white blood cells >13.0 G/L (OR, 5.50; CI, 1.41–21.48) and blood glucose >140 mg/dL [7.8 mmol/L] (OR, 7.45; CI, 1.70–32.86). In the derivation cohort, the area under the ROC curve (AUC-ROC) of the APPM score did not significantly differ from AUC-ROCs of serum paraquat (0.95, p = 0.25) and the Severity Index of Paraquat Poisoning (0.95, p = 0.33). AUC-ROCs of the APPM score in the derivation and validation cohorts were 0.91 and 0.94, respectively. Conclusion We built and validated a reliable score to predict 28-day mortality in paraquat-poisoned patients at presentation, independently from the ingestion time and serum paraquat measurement.

Electrochemical determination of paraquat using a glassy carbon electrode decorated with pillararene-coated nitrogen-doped carbon dots

An electrochemical sensor (carboxylatopillar[5]arene-coated nitrogen-doped carbon dots, namely CCDs) based on carboxylatopillar[5]arene (CP[5]) functionalized nitrogen-doped carbon dots (N-CDs) has been developed in a facile and economic manner. To improve the performance of this electrochemical sensor in pesticide detection, the optimal solution pH (pH 7) and loading amount of CCDs on the electrode (0.50 mg/mL) have been determined. By virtue of the good conductivity of N-CDs and the molecular recognition property of CP[5], CCDs modified glassy carbon electrode, namely CCDs/GCE, shows excellent anti-interference capability, selectivity, stability, and reproducibility in the sensitive detection of paraquat. The peak currents are proportional to the paraquat concentration (from 0.1 µmol/L to 10 µmol/L) with a detection limit of 6.4 nmol/L (S/N = 3), indicating a great potential in pesticide detection. In comparison with the electrochemical sensors that require expensive metal nanoparticles and complex preparation processes, CCDs/GCE exhibits excellent detection capability of paraquat with lower cost and simpler preparation processes.

Paraquat promotes acute lung injury in rats by regulating alveolar macrophage polarization through glycolysis

The present study investigates whether paraquat (PQ) regulates polarization of alveolar macrophages through glycolysis and promotes the occurrence of acute lung injury in rats. In vivo, the PQ intraperitoneal injection was used to construct a model of acute lung injury in rats. In vitro, the study measured the effect of different concentrations of PQ on the viability of the alveolar macrophages, and explored the polarization and glycolysis metabolism of alveolar macrophages at different time points after PQ intervention. Compared with the normal control (NC) group, the lung pathological damage in rats increased gradually after PQ poisoning, reaching a significant degree at 48 h after poisoning. The PQ-poisoned rat serum showed increased expressions of interleukin-6 (IL-6), tumor necrosis factor- α (TNF-α), and M1 macrophage marker, iNOS, while the expression of interleukin-10 (IL-10) and M2 macrophage marker, Arg1, decreased. The toxic effect of PQ on alveolar macrophages was dose- and time-dependent. Compared with the NC group, IL-6 and TNF-α in the cell supernatant gradually increased after PQ intervention, while the IL-10 content gradually decreased. The PQ intervention in alveolar macrophages increased the expression of intracellular glycolysis rate-limiting enzyme pyruvate kinase isozymes M1/M2 (PKM1/M2), lactate, lactate/pyruvate ratio, and the polarization of alveolar macrophage towards M1. Inhibition of cellular glycolysis significantly reduced the PQ-induced alveolar macrophage polarization to M1 type. Thus, PQ induced increased polarization of lung macrophages toward M1 and decreased polarization toward M2, promoting acute lung injury. Therefore, it can be concluded that PQ regulates the polarization of alveolar macrophages through glycolysis.

Clinical research of the differences between hematocrit and serum albumin for evaluating the severity of acute paraquat poisoning

To investigate the clinical values of the differences between hematocrit and serum albumin (HCT-ALB) for evaluating the severity of patients with acute paraquat (PQ) poisoning. Patients with acute PQ poisoning admitted to the Second People's Hospital of Yunnan Province from January 2018 to December 2019 were enrolled, and healthy voluteers during the same period were selected as the control. The general information, poisoning dose and poisoning time of patients, as well as the HCT and serum ALB levels before blood product infusion, intravenous infusion, or hemopurification at admission were collected, and the HCT-ALB was calculated. According to the results of rapid semiquantitative test of PQ in urine at admission, the patients were divided into PQ low concentration group (0-10 mg/L) and PQ high concentration group (30-100 mg/L). The relationship between poisoning time, poisoning dose, HCT-ALB and the degree of acute PQ poisoning were analyzed, and Spearman method was used to analyze the grade correlation. A total of 295 patients with acute PQ poisoning were enrolled, including 118 cases in PQ low concentration group and 177 cases in PQ high concentration group, and another 200 healthy persons matched with PQ patients in gender and age (healthy control group). The poisoning time of PQ low concentration group was significantly longer than that of PQ high concentration group [hours: 11.0 (6.0, 60.0) vs. 8.0 (5.0, 20.5), P < 0.01], but the poisoning dose was significantly lower than that of PQ high concentration group [mL: 10.0 (5.8, 15.0) vs. 40.0 (20.0, 80.0), P < 0.01]. The HCT and HCT-ALB in PQ low and high concentration groups were significantly higher than those of the healthy control group [HCT: (43.14±4.41)%, (43.54±5.40)% vs. (42.14±2.15)%, HCT-ALB: 3.59±6.26, 5.94±7.80 vs. -7.26±3.55, all P < 0.01], but ALB was significantly lower than that of the healthy control group (g/L: 39.54±5.74, 37.60±7.15 vs. 49.40±3.41, both P < 0.01). With the increase of urine PQ concentration, the HCT and HCT-ALB further increased, and ALB further decreased. There were significant differences between PQ high concentration group and PQ low concentration group [HCT: (43.54±5.40)% vs. (43.14±4.41)%, HCT-ALB: 5.94±7.80 vs. 3.59±6.26, ALB (g/L): 37.60±7.15 vs. 39.54±5.74, all P < 0.05]. The poisoning severity of patients with acute PQ poisoning were negatively correlated with poisoning time and ALB (r values were -0.195 and -0.695, respectively, both P < 0.01), there were positively correlated with poisoning dose, HCT, and HCT-ALB (r values were 0.650, 0.256, 0.737, respectively, all P < 0.01), and the correlation between HCT-ALB and poisoning severity was the strongest. The HCT-ALB can reflect the poisoning severity of patients with acute PQ poisoning and indirectly reveal the pathological changes of microvessels in patients with acute PQ poisoning.

Rice response to sublethal concentrations of paraquat, glyphosate, saflufenacil, and sodium chlorate at multiple late-season application timings as influenced by exposure

AbstractIn Mississippi, rice reproduction and ripening often overlaps with soybean maturation, creating potential for herbicide exposure onto rice from desiccants applied to soybeans. Six independent studies were conducted concurrently at the Delta Research and Extension Center in Stoneville, MS, from 2016 to 2018 to determine the response of rice to sublethal concentrations of soybean desiccants during rice reproductive and ripening growth stages. Studies included the desiccants paraquat, glyphosate, saflufenacil, sodium chlorate, paraquat + saflufenacil, and paraquat + sodium chlorate applied at a rate equal to 1/10th of Mississippi recommendations. Treatments were applied at five different rice growth stages, beginning at 50% heading––defined as 0 d after heading (DAH)––with subsequent applications at 1-wk intervals (0, 7, 14, 21, and 28 DAH), up to harvest. Injury was observed 7 d after application (DAA), with five of six desiccants at all application timings. No injury was observed with glyphosate application across all rating intervals. Rough rice grain yield following all glyphosate applications was reduced by &gt;6%. In the studies evaluating paraquat, injury ranged from 5% to 18% at all evaluations, regardless of application timing. Rough rice grain yield was reduced &gt;12% 0 to 21 DAH, following paraquat application. Similar trends were observed with paraquat + saflufenacil and paraquat + sodium chlorate, with rice exhibiting yield decreases &gt;6% following an application 0 to 14 and 0 to 21 DAH, respectively. In studies evaluating saflufenacil and sodium chlorate, rough rice grain yield was &gt;95% of the untreated across all application timings Yield component trends closely resembled reductions observed in rough rice grain yield. Reductions in head rice yield were &gt;5% following applications of paraquat or paraquat + saflufenacil 0 to 14 and 0 to 21 DAH, respectively. Late-season exposure to sublethal concentrations of desiccant from 50% heading (0 DAH) to 28 DAH has an impact on rough rice grain yield, yield components, and head rice yield.

Exogenous salicylic acid mediated herbicide (Paraquat) resistance in cyanobacterial biofertilizer Microchaete sp. NCCU-342.

Paddy field farming remains the dominant form of growing rice in modern times as the rice is the staple food for over half the world's population and is closely associated with food security and political stability of many countries. Record increase in rice production have been observed since the start of the Green Revolution. India is one of the largest paddy producer and exporter in the world. However, constant use of chemical herbicide like paraquat had shown adverse impact on the rice yield. Non-target organisms of the habitat including cyanobacterial paddy biofertilizer face the herbicide toxicity and are unable to perform efficiently their role as biofertilizer. Therefore, in the present study, an attempt has been made to enhance the paraquat resistance in rice biofertilizer (Microchaete sp. NCCU-342) by exogenous addition of salicylic acid. Paraquat showed toxicity in Microchaete sp. NCCU-342 in a dose-dependent manner. Concentration of paraquat >1.0 μM exhibited lethal effect since the beginning. Through successive narrow range experiment, LD50 value of paraquat was obtained as 0.6 μM. Biomass exposed to paraquat (LD50 value) and salicylic acid (0.3 mM) showed mitigation in free radical production (2.20 % MDA and 1.69 % H2O2) and enhancement in the activity of the antioxidant enzymes activity, i.e. SOD, CAT, APX (137.76 %, 87.45 %, 118 %, respectively) and osmolytes (3.8 % proline and 21.51% sucrose). Thus, for sustainable agricultural practice, especially for paddy field cyanobacterial biofertilizer, application of salicylic acid or organism with higher salicylic acid production ability may be an alternative to overcome the paraquat toxicity.

Mechanistic Investigation of Xuebijing for Treatment of Paraquat-Induced Pulmonary Fibrosis by Metabolomics and Network Pharmacology.

After paraquat (PQ) poisoning, it is difficult to accurately diagnose patients’ condition by only measuring their blood PQ concentration. Therefore, it is important to establish an accurate method to assist in the diagnosis of PQ poisoning, especially in the early stages. In this study, a gas chromatography–mass spectrometry (GC–MS) metabonomics strategy was established to obtain metabolite information. A random forest algorithm was used to search for potential biomarkers of PQ poisoning, and data mining and network pharmacological analysis were used to evaluate the active components, drug–disease targets, and key pathways of Xuebijing (XBJ) injection in the treatment of PQ-induced pulmonary fibrosis. Targets from the network pharmacology analysis and metabolites from plasma metabolomics were jointly analyzed to select crucial metabolic pathways. Finally, molecular docking technology and in vitro experiments were used to verify the pathway targets to further reveal the potential mechanisms underlying the antipulmonary fibrosis effect of XBJ. Metabonomics studies showed that l-valine, glycine, citric acid, d-mannose, d-galactose, maltose, l-tryptophan, and arachidonic acid contributed more to the differentiation of different groups than other metabolites. Compared with the control group, the PQ poisoning group had higher levels of l-valine, glycine, citric acid, l-tryptophan, and arachidonic acid, and lower levels of d-mannose, d-galactose, and maltose. After treatment with XBJ injection, the relative levels of these metabolites were reversed. The network pharmacological analysis screened a total of 180 targets, mainly involving multiple signaling pathways and metabolic pathways, which jointly played an antipulmonary fibrosis effect. Based on the combined analysis of 180 targets and 8 different metabolites, arachidonic acid metabolism was selected as the key metabolic pathway. Molecular docking analysis showed that the XBJ compound had strong binding activity with the target protein. Western blot results showed that XBJ injection could reduce the inflammatory response by downregulating the expressions of p-p65, p-IKBα, and p-IKKβ, thus inhibiting the development of PQ-induced pulmonary fibrosis. In summary, the combined results from metabolomics and network pharmacology studies showed that Xuebijing has the characteristics of multitarget, multichannel, and multicomponent action in the treatment of pulmonary fibrosis caused by PQ.

Determination of the herbicide paraquat using the new Ag‐GO/CuO/GCE‐modified glassy carbon electrode by differential pulse voltammetry

AbstractFinding the synergistic electrochemical effect of cuprous oxide nanoparticle (CuO‐NP), Ag‐nanoparticle (Ag‐NP) on graphene oxide (GO) encouraged us to provide a novel modified glassy carbon electrode (GCE) for the determination of the herbicide paraquat (PQ) in solution. The necessary compounds were prepared by simple methods and characterized by scanning electronic microscopy, UV/Vis spectroscopy, and electrochemical impedance spectroscopy. The sensor showed good electrocatalytic activity toward the reduction of PQ. The cyclic voltammetric and DPV results showed that the oxidation and reduction processes of PQ are reversible and the Ag‐GO/CuO composition had good electrocatalytic performances in the determination of PQ. The responses of the electrochemical Ag‐GO/CuO/GCE were investigated for pH, type of supporting electrolyte, scan rate, and the response reproducibility of the system. Under the optimized conditions, a linear response over the concentration range of 0.40–650.0 μM of PQ was observed with a correlation coefficient (R2) of 0.999 and a detection limit of 0.07 μM. Reasonable recoveries between 99.2 and 105.0% were obtained for river water PQ content.

Use of Lens culinaris Med test as environmental bioindicator to identify the cytogenotoxic effect of paraquat pesticide.

Paraquat is the most widely used herbicide and the third most sold pesticide in the world, applied in more than 120 countries despite being banned in the European Union. It is a risk to ecosystems. The genotoxic effect of paraquat was evaluated using the Lens culinaris test. L. culinaris seeds were subjected to 6 concentrations of paraquat (0.1, 0.5, 1, 1.5, 1.5, 2, and 3 ppm) plus a control (distilled water). During 72 h, root development was measured every 24 h. After 3 days, root apices were analyzed to obtain the inhibition of the mitotic index, as well as the type and rate of chromosomal abnormalities present. A decrease in root growth of more than 50% (72 h of exposure) and an inhibition of the mitotic index of 2.9 times in the treatment with 3 ppm compared to the control were observed. The 2 ppm concentration presented all the anomalies found with a frequency of 84 ± 2.5 of micronuclei, 106 ± 3.5 of nuclear lesions, 14 ± 4.7 of nucleus absence, 8 ± 2.7 of telophase bridges, 7 ± 2.7 of binucleated cells, among others. It is also recommended to establish comparisons of L. culinaris with multiple biomarkers since it is presented as a practical and economic alternative.

Behavioural Responses and Mortality of Clarias gariepinus Juveniles Exposed to Acute Concentrations of Paraquat

Paraquat is the most common contact and non- selective herbicide for exterminating vegetative pest. Fish are ideal sentinels for detecting aquatic pollutants and are largely used as bio indicators of environmental pollution. This study is aimed to determine the behavioural changes, lethal concentrations (LCs) and mean lethal time (MLT) of paraquat exposed to Clarias gariepinus. A 96 hours renewable bioassay was conducted with various paraquat concentrations 0.0, 0.25, 0.50, 0.75, 1.0 and 1.25 mg/l. Behavioural changes and cumulative mortality were observed and recorded at 12, 24, 48, 72 and 96 hour. Behavioural changes such as air gulping, erratic swimming, loss of balance, excessive mucus secretion, discolouration and death were observed with severity increasing as concentration and duration of exposure increases. The LC50 values were decreased from 0.191mg/l (0.171 – 0.222) in 12 hour to 0.107mg/l (0.065 – 0.150) in 96 hour, while relative toxicity factor (TF) was increased from 1 to 1.79 times respectively. The 96hr MLT values were decreased from 91.18 hours (54.09-105.64) at the lowest concentration to 16.22 hours (9.06 – 25.15) at the highest concentration with relative toxicity time (RTT) increasing from 1 to 5.62 times. Herbicide should be apply with caution and studies on the sub lethal effects of paraquat on the haematological, biochemical and histological parameters of C. gariepinus juveniles will be necessary.

Ordered mesoporous silica (SBA-16) supporting titania (TiO2) nanoparticles for photodegradation of paraquat (PQ) herbicide

SBA-16, a kind of highly ordered mesoporous silica, was synthesized via a sol–gel method used as the supporter of TiO2 nanoparticles. With variation of Si/Ti molar ratios at 5.6, 1.4 and 0.7, SBA-16/TiO2 nanocomposites were prepared. In this study, pristine TiO2 was also synthesized as a control sample. Prior use, as-synthesized powders were calcined at 500 °C for 4 h. Physicochemical properties of the calcined powders were characterized by using various techniques. Degradation studies of a commercial paraquat (PQ) herbicide, having blue color from addition of the unknown dye, were performed using the SBA-16/TiO2 nanocomposites compared with the SBA-16 support and the pristine TiO2. Experimental results showed that the blue colors of the solutions were faded very quickly within 30 min when tested with SBA-16 and 5.6 SBA-16/TiO2 in dark conditions. The solutions were completely decolorized when the UV light was on for all composites and the pristine TiO2. The degradation of the dye was mainly depended on the adsorption process on SBA-16 surfaces. Photodegradation of PQ in the solutions was started by the nanocomposites and TiO2 tested under UV illumination conditions. The dye was completely degraded and the concentrations of PQ in the prepared solutions were reduced and reached to the maximum reduction at 70% within 24 h by 1.4 SBA-16/TiO2. Kinetic mechanisms for the differences of degradation characteristics by the catalysts under light-on and off conditions were studied, discussed and modelled.

Effect of paraquat dichloride application to the soil arthropods on the rice field, corn, and oil palm plantation

Paraquat dichloride is a non-selective contact herbicide currently used by farmers in Indonesia to control weeds on plantations, such as palm oil, rubber, and cocoa. There are only a few studies to date on the eco-toxicological aspects of paraquat. Therefore, the research aim was study the effect of paraquat application on soil arthropods on three commodities. The research conducted on the rice and corn fields, and oil palm plantations in two consecutive seasons. Treatments included three paraquat concentrations (4, 8, and 16 ml/l); carbendazim (2 g/l); and control, with five replicates. The number and abundance of soil arthropods observed using pitfall traps and the collection of outermost soil layers for each crop at 0, 2, 4, 8, and 12 weeks after application. The order number of soil arthropods collected from rice, oil palms, and corn in season 1 was 12, 13, and 16, respectively; and 10, 16, and 16 in season 2. The three most dominant groups of soil arthropods were collembola, mites, and ants. The population patterns of soil arthropods for those three commodities were similar. Paraquat was thought to be toxic to non-target organism, such as terrestrial arthropods. This research showed that paraquat had an effect on the presence and population of soil arthropods for certain time after application. However, after 8 to 12 weeks after application, the population increased slightly.