Photocatalytic degradation of imidacloprid using Ag2O/CuO composites.

Imidacloprid is one of the most commonly used neonicotinoid pesticides that has been identified as a neurotoxin for various non-target organisms. It binds to the central nervous system of organisms, causing paralysis and eventually death. Thus, it is imperative to treat waterwaters contaminated with imidacloprid using an efficient and cost effective method. The present study presents Ag2O/CuO composites as excellent catalysts for the photocatalytic degradation of imidacloprid. The Ag2O/CuO composites were prepared in different compositions by adopting the co-precipitation method and used as a catalyst for the degradation of imidacloprid. The degradation process was monitored using UV-vis spectroscopy. The composition, structure, and morphologies of the composites were determined by FT-IR, XRD, TGA, and SEM analyses. The effect of different parameters i.e time, concentration of pesticide, concentration of catalyst, pH, and temperature on the degradation was studied under UV irradiation and dark conditions. The results of the study evidenced the 92.3% degradation of imidacloprid in only 180 minutes, which was 19.25 hours under natural conditions. The degradation followed first-order kinetics, with the half life of the pesticide being 3.7 hours. Thus, the Ag2O/CuO composite was an excellent cost-effective catalyst. The non-toxic nature of the material adds further benefits to its use. The stability of the catalyst and its reusability for consecutive cycles make it more cost effective. The use of this material may help to ensure an immidacloprid free environment with minimal use of resources. Moreover, the potential of this material to degrade other environmental pollutants may also be explored.

Surveillance and dietary risk assessment of endocrine-disrupting pesticides in eggplant/brinjal and cauliflower in Pakistan.

Several pesticides (used in vegetable production) have recently been identified as potential endocrine disruptors. The current study aimed to determine the consumer exposure risk associated with eating contaminated vegetables. The European Union-citrate buffered QuEChERS extraction protocol, validated in accordance with the European Union guidelines, was used to monitor selected endocrine-disrupting pesticides in eggplant/brinjal (Solanum melongena L.) and cauliflower (Brassica oleracea) marketed in Rawalpindi/Islamabad, Pakistan. A total of 80 and 69 percent of eggplant/brinjal (n = 25) and cauliflower (n = 26) samples were found contaminated, respectively. Sixty-five percent of cauliflower samples were found non-contaminated with both European Union (EU) and Codex Alimentarius Commission (CAC) maximum residue limits (MRL), while 20 % of brinjal samples were found to be non-compliant with EU-MRL. Both vegetables contained high levels of the androgen antagonist chlorpyrifos and the thyroid hormone inhibitor cyhalothrin-lambda. The estimated acute health risk associated with dietary exposure to chlorpyrifos and cyhalothrin-lambda in cauliflower for both males and females was found to be greater than 200 % of the FAO/WHO Joint Meeting on Pesticide Residues' (JMPR) established acute reference dose. The estimated chronic health risk for all studied endocrine-disrupting pesticides (0-5.27 %) indicates zero to very low health risk for studied population groups.

Analysis of multiple pesticide residues in market samples of okra and associated dietary risk assessment for consumers.

European Union Reference Laboratory method for Fruits and Vegetables (EURL-FV-2010-M1) for the quantification of pesticide residues was verified for the determination of multiple pesticide residues in okra. The targeted pesticides were extracted using acetonitrile with citrate buffer salts followed by cleanup with primary secondary amine (PSA) and analyzed on LC-MS/MS. The recoveries for all the targeted pesticides were within an acceptable range of 70.1-116.6% and precision in terms of RSD was 0.3-18.1%, respectively. The limit of quantification ranged from 0.002 mg/kg for carbofuran to 0.5 mg/kg for α-cypermethrin. The status of pesticide residues in okra (n = 21) available to consumers in the main markets of Pakistan has been determined by using this verified method. Sixty-two percent of the tested samples were contaminated out of which three samples were non-compliant with European Union maximum residue limits (EU-MRL). The pesticides violating the EU-MRL were bifenthrin, thiamethoxam, and triazophos. For all the detected pesticides, estimated daily intake (EDI) ranged between 1.40 × 10-6 and 1.78 × 10-4 mg/kg of body weight, chronic exposure risk (%ADI) ranged from 0.0073 to 1.8%, and acute exposure risk (%ARfD) ranged from 0.01 to 24.20%. The results exhibited insignificant risk from chronic exposure and minor to medium level of risk from acute exposure of these pesticides to human health.

Method optimization and validation for the routine analysis of multi-class pesticide residues in Kinnow Mandarin and fruit quality evaluation.

The present study describes the selection of a sensitive multi-residue method that can be used for the routine testing of pesticides in Kinnow Mandarin. The citrate-buffered QuEChERS extraction followed by primary secondary amines and C18 clean-up was found suitable for the analysis of fifty four pesticides. The limit of quantification for the selected pesticides was lower than maximum residue limits (MRLs) set by European Union, Codex Alimentarius Commission (CAC), and twelve other countries. The method's accuracy ranged from 74.4 to 112% and expanded uncertainty ranged from 7.5 to 49.6%. The validated method was applied to Kinnow Mandarin samples, collected from 22 export units of district Sargodha, Pakistan. Almost 27% of the samples (n = 22) were exceeding the CAC-MRLs. The index of quality for residues (IqR), for 64% of the samples, was considered adequate. The study indicates the need for regular monitoring to protect public health and ensure safe and consistent trade.

Determination of pesticide residues in dates using UHPLC-QqQ-MS/MS: method development and validation.

A modified, efficient, and sensitive acetate-buffered QuEChERS extraction method was developed for the quantitative study of 16 commonly applied multiclass pesticides on date palm fruit. The date palm fruit samples were rehydrated by adding water during comminution. Samples were extracted with acidified acetonitrile, buffered with acetate salt. To minimize the matrix interferences, clean-up of the rehydrated samples was optimized by comparison with different sorbents (alumina, silica gel, florisil, primary secondary amine (PSA), and chitosan). The method validation parameters were evaluated as per European Union (EU) guidelines (SANTE/12682/2019). For 16 pesticides, % recovery of 69 to 121.8% with an associated precision (RSD ≤ 20%) was achieved at the fortification levels that were 0.5 to 2 times of European Union maximum residue limits (EU-MRLs). The validated method was successfully employed for the analysis of date palm fruit samples (n = 20) collected from various markets. Forty percent (40%) of samples (n = 8) were found to be contaminated with various pesticides. The most frequently detected residues were carbofuran, carbaryl, metalaxyl, tebuconazole, triazophos, and pyriproxyfen. The concentration of all the detected pesticides in real samples was below the EU-MRLs.

Zn2+ and Cd2+ assisted photo-catalytic degradation of chlorpyrifos in soil.

The Cd2+ and Zn2+ assisted photo-catalytic degradation of soil incorporated chlorpyrifos (CLP) was reported in current study. The soil samples fortified with CLP and metals were irradiated in photo-reactor for different time intervals to check maximum degradation. Soil samples extracted with acetonitrile were analyzed by HPLC. The results of the study revealed a complete mineralization of insecticide from soil that followed first-order Langmuir-Hinshelwood (L-H) kinetic model. The CLP degradation rate in soil was higher in photoreactor than control with variation in half-life from 41 days to 20 days. The degradation of CLP in photoreactor was 5 fold augmented after Zn2+ fortification of soil while Cd2+ had negligible effect on CLP photodegradation. Thus Zn2+ fortification of soil will not only replenish the important nutrient for plant growth but will also help in alleviating the harmful effects of CLP on soil flora and fauna by enhancing its rate of photodegradation.

Screening of multiclass pesticide residues in honey by SPE-GC/MSD: a pilot study.

Analytical method for the monitoring of residues of multiclass pesticides (variable chemical structure and chromatographic behavior) in honey has been optimized and in-house validated in the present study. Chemical confirmation of 35 selected pesticides (in-hive-treated pesticides and pesticides applied for agricultural practices in vicinity of apiaries) has been successfully achieved with the acetonitrile extraction/partitioning and cleanup by modified US EPA solid-phase extraction (SPE) protocol following analysis on the GC/MS DRS Pesticide Screener. The applied extraction procedure has given acceptable recoveries with an associated precision (RSD) for selected pesticides within the range as suggested by SANTE at MQL of 10 µg kg-1. Potential matrix effect for selected analytes was calculated by using honey from five different floral sources. The optimized method was used to determine levels of pesticide residues in honey samples randomly collected from 26 different apiaries in Pakistan. Residues of nine selected pesticide (dichlorvos, mevinphos, ethalfluralin, trifluralin, lindane, chlorpyrifos-methyl, dieldrin, profenofos, 4,4-DDE) were frequently detected in the ranges of 3-48.8 µg kg-1 in 26.9% of analyzed samples (n = 26) and 15.3% of the studied samples exceeded maximum residue limits (MRLs). In-hive-treated acaricides, i.e., coumaphos, tau-fluvalinate, and malathion, were not detected in any of the analyzed honey samples.

Monitoring and distribution patterns of pesticide residues in soil from cotton/wheat fields of Pakistan.

The excessive use of hazardous pesticides for massive cotton and wheat production has deteriorated the quality of Okara district's soil. Thus, in order to sustain the production of good-quality food, it is essential to determine the residue levels of pesticides in the agricultural soil and define their possible sources. Thus, the present study focused on the determination of selected pesticides in the soil samples obtained from cotton/wheat fields by using the modified multi-residue pesticide analysis method based on GCMS and HPLC-UV. Most of soil samples were found to be highly contaminated with imidacloprid, chlorpyrifos, and α-cypermethrin residues. Selected pesticides were significantly correlated with each other at p < 0.05 except imidacloprid, which was negatively correlated with triazophos, MCPA methyl ester, selected pyrethroid pesticides, and their metabolite. Soil pH and phosphate levels were significantly positively correlated while sulfate content was negatively correlated with most of selected pesticides. The varimax normalized factor analysis divides the selected pesticides to the two major factors that explained 87.19% of the total variance which evidenced that pesticide in the same cluster shared a common source in the soil. A significant negative correlation of chlorpyrifos in the second factor pointed towards a source different from other pesticides. Factor and cluster analysis indicated that sulfate levels of soil positively affected the persistence/ mobility of imidacloprid.

Distribution and source apportionment studies of heavy metals in soil of cotton/wheat fields.

Heavy metals enriched agricultural soils have been the subject of great concern because these metals have potential to be transferred to the soil solution and afterward accumulated in food chain. To study the trace metal persistence in crop soil, 90 representative soil samples were collected and analyzed for heavy metal (As, Cd, Cu, Fe, Mn, Ni, Pb, and Zn) and anions (chloride, nitrates, phosphates and sulfates). Cluster and factor analysis techniques were used for the source identification of these excessive heavy metal levels and ecological risk was determined with potential ecological risk assessment. The degree of enrichment of eight studied heavy metals in comparison with the corresponding background levels decreased in order: Cd > Pb > Fe > Ni > Mn > As > Cu ~ Zn. Arsenic and cadmium exhibited 1.30- and 1.64-fold exceeded levels than threshold limits set by National environment quality standards, respectively. Cd in cotton field's soil may lead to higher potential risk than other heavy metals. On overall basis, the cumulative mean potential ecological risk for the district (207.75) corresponded to moderate risk level with higher contributions from As and Pb especially from Cd. Cadmium formed strong positive correlation with phosphate content of soil at p < 0.01. Cluster analysis indicated that Cluster 1 (extremely polluted) probably originated from anthropogenic inputs of phosphate fertilizer and past usage of arsenical pesticides.

Cu(2+) and Fe(2+) mediated photodegradation studies of soil-incorporated chlorpyrifos.

The influences of Cu(2+) and Fe(2+) on the photodegradation of soil-incorporated chlorpyrifos were investigated in the present study. The soil samples spiked with chlorpyrifos and selected metal ions were irradiated with UV light for different intervals of time and analyzed by HPLC. The unsterile and sterile control soil samples amended with pesticides and selected metals were incubated in the dark at 25 °C for the same time intervals. The results of the study evidenced that photodegradation of chlorpyrifos followed the first-order kinetics. The dissipation t0.5 of chlorpyrifos was found to decrease from 41 to 20 days under UV irradiation. The rate of chlorpyrifos photodegradation was increased in the presence of both metals, i.e., Cu(2+) and Fe(2+). Thus, initially observed t0.5 of 19.8 days was decreased to 4.39 days in the case of Cu(+2) and 19.25 days for Fe(+2). Copper was found to increase the rate of photodegradation by 4.5 orders of magnitude while the microbial degradation of chlorpyrifos was increased only twofold. The microbial degradation of chlorpyrifos was only negligibly affected by Fe(2+) amendment. The studied trace metals also affected the abiotic degradation of the pesticide in the order Cu(2+) > Fe(2+).

Photodegradation of α-cypermethrin in soil in the presence of trace metals (Cu2+, Cd2+, Fe2+ and Zn2+).

The influence of trace metals (Cu(2+), Zn(2+), Cd(2+) and Fe(2+)) on the photodegradation of α-cypermethrin (α-CYM) in agricultural soil was studied. The soil samples were spiked with α-cypermethrin with/without the presence of metal ions, irradiated under a UV irradiation chamber for a regular period of time and analyzed by using HPLC. The dark control sterile and unsterile soil samples spiked with α-cypermethrin and selected trace metals were incubated for the same interval of time at 25 °C. The results obtained indicated that α-cypermethrin photodegradation followed biphasic kinetics. α-cypermethrin photodegradation half-lives (t1/2) were increased to 0.71 and. 4.5 hours from 0.64 hours respectively in the presence of elevated Zn(2+) and Cu(2+) concentrations. Fe(2+) and Cd(2+) increased the photodegradation reaction kinetics from -1.078 h(-1) to -1.175 h(-1) and -1.397 h(-1) and varied the t1/2 from 0.64 ± 1.41 to 0.59 ± 2.07 and 0.49 ± 2.01 in the soil. Microbes also affected the degradation of α-cypermethrin in metal contaminated soil. The degradation rate was inhibited in unsterile soil and was found to be in the following order: Cd(2+)< Zn(2+)< Cu(2+)< Fe(2+). The degradation/persistence of α-cypermethrin was affected linearly with the increasing soil metal concentrations.