Persistent Pesticides Research Articles

Hafnium Polystyrene Composite Particles for the Detection of Organophosphate Compound

Organophosphate (OP) pesticides present a challenge for detection and identification in both the gas and liquid phase. The organophosphate esters are commonly used as persistent pesticides and nerve agents. Thus, it is highly desirable to develop methods for the detection of these compounds. Bragg diffraction of laser light from crystalline colloids of polystyrene spheres is observed for the detection of OPs. This was done by utilizing a simple method for the colloidal crystal arrays (CCA) based on a polystyrene (PS) core and a hafnium oxide (HfO2) shell sensing composite particles that detects the organophosphorus compound paraoxon (OP) of varying concentrations in aqueous solution. The molecular recognition agent for the sensor is hafnium, which is an inorganic compound that theoretically has an affinity for paraoxon. Energy Dispersive Analysis of X-rays (EDX) was used to characterize the PS coated HfO2 particles as well as for the confirmation of the presence of hafnium around the polystyrene core. Transmission electron microscopy (TEM) verified the presence of HfO2 clusters on polystyrene spheres. Reflectance measurements were carried out for varying concentrations of paraoxon from 0.024 ppm to 0.096 ppm, showing a characteristic shift in the reflectance peak from 470 to 483 nm. The peaks wavelength shift from right to left suggested that the distance between the crystals was increasing due to the addition of the concentration of paraoxon. Thus, it acts as a chemical sensor for paraoxon since hafnium has an affinity for phosphate groups. As a result, theoretical matches practical which suggests that hafnium acts as a chemical sensor for paraoxon. It was expressed that by increasing the paraoxon concentration, the reflectance peak increased linearly, making CCA a prospective technique for future chemical sensor research.

Pesticide Photolysis in Prairie Potholes: Probing Photosensitized Processes

Prairie pothole lakes (PPLs) are glacially derived, ecologically important water bodies found in central North America and represent a unique setting in which extensive agriculture occurs within wetland ecosystems. In the Prairie Pothole Region (PPR), elevated pesticide use and increasing hydrologic connectivity have raised concerns about the impact of nonpoint source agricultural pollution on the water quality of PPLs and downstream aquatic systems. Despite containing high dissolved organic matter (DOM) levels, the photoreactivity of the PPL water and the photochemical fate of pesticides entering PPLs are largely unknown. In this study, the photodegradation of sixteen pesticides was investigated in PPL waters sampled from North Dakota, under simulated and natural sunlight. Enhanced pesticide removal rates in the irradiated PPL water relative to the control buffer pointed to the importance of indirect photolysis pathways involving photochemically produced reactive intermediates (PPRIs). The steady-state concentrations of carbonate radical, hydroxyl radical, singlet oxygen, and triplet-excited state DOM were measured and second-order rate constants for reactions of pesticides with these PPRIs were calculated. Results from this study underscore the role of DOM as photosensitizer in limiting the persistence of pesticides in prairie wetlands through photochemical reactions.

The dissipation of three fungicides in a biobed organic substrate and their impact on the structure and activity of the microbial community

Biopurification systems (BPS) have been introduced to minimise the risk for point source contamination of natural water resources by pesticides. Their depuration efficiency relies mostly on the high biodegradation of their packing substrate (biomixture). Despite that, little is known regarding the interactions between biomixture microflora and pesticides, especially fungicides which are expected to have a higher impact on the microbial community. This study reports the dissipation of the fungicides azoxystrobin (AZX), fludioxonil (FL) and penconazole (PC), commonly used in vineyards, in a biomixture composed of pruning residues and straw used in vineyard BPS. The impact of fungicides on the microbial community was also studied via microbial biomass carbon, basal respiration and phospholipid fatty acid analysis. AZX dissipated faster (t1/2 = 30.1 days) than PC (t1/2 = 99.0 days) and FL (t1/2 = 115.5 days). Fungicides differently affected the microbial community. PC showed the highest adverse effect on both the size and the activity of the biomixture microflora. A significant change in the structure of the microbial community was noted for PC and FL, and it was attributed to a rapid inhibition of the fungal fraction while bacteria showed a delayed response which was attributed to indirect effects by the late proliferation of fungi. All effects observed were transitory and a full recovery of microbial indices was observed 60 days post-application. Overall, no clear link between pesticide persistence and microbial responses was observed stressing the complex nature of interactions between pesticides in microflora in BPS.

Pesticide Nonextractable Residue Formation in Soil: Insights from Inverse Modeling of Degradation Time Series

Formation of soil nonextractable residues (NER) is central to the fate and persistence of pesticides. To investigate pools and extent of NER formation, an established inverse modeling approach for pesticide soil degradation time series was evaluated with a Monte Carlo Markov Chain (MCMC) sampling procedure. It was found that only half of 73 pesticide degradation time series from a homogeneous soil source allowed for well-behaved identification of kinetic parameters with a four-pool model containing a parent compound, a metabolite, a volatile, and a NER pool. A subsequent simulation indeed confirmed distinct parameter combinations of low identifiability. Taking the resulting uncertainties into account, several conclusions regarding NER formation and its impact on persistence assessment could nonetheless be drawn. First, rate constants for transformation of parent compounds to metabolites were correlated to those for transformation of parent compounds to NER, leading to degradation half-lives (DegT50) typically not being larger than disappearance half-lives (DT50) by more than a factor of 2. Second, estimated rate constants were used to evaluate NER formation over time. This showed that NER formation, particularly through the metabolite pool, may be grossly underestimated when using standard incubation periods. It further showed that amounts and uncertainties in (i) total NER, (ii) NER formed from the parent pool, and (iii) NER formed from the metabolite pool vary considerably among data sets at t→∞, with no clear dominance between (ii) and (iii). However, compounds containing aromatic amine moieties were found to form significantly more total NER when extrapolating to t→∞ than the other compounds studied. Overall, our study stresses the general need for assessing uncertainties, identifiability issues, and resulting biases when using inverse modeling of degradation time series for evaluating persistence and NER formation.

Flows, floods, floodplains and river restoration

Returning water to rivers as environmental flows is now a major tool for restoration. Many plans for environmental flows have been modelled and devised but few have been delivered, at least in Australia. Nevertheless, as planned in the latest version of the Murray‐Darling Basin Authority’s (2011) Draft Basin Plan, water recovery for environmental flows is firmly advocated. In environmental flow planning, a key component to restore is periodic (seasonal) floods. Thus, in upland rivers that have been dammed, below-dam floods are seen as vital to reshape channels, to remove unnaturally high levels of sediments accumulated since dams were built and to improve water quality. An example of this is the restoration of the Snowy River below Jindabyne Dam (NSW Office of Water 2010). Environmental flows are released to lift base flow and to introduce variability that mimics pre-dam levels and the seasonal snow-melt flood. The flood is not of the magnitude of the pre-dam flows, but is designed to improve the river by remoulding the channel, removing accumulated sediments and detritus, improving water quality and rebuilding habitats typical of an upland river. In general, restoring floods in constrained upland rivers aims to improve channel conditions. Lowland rivers are usually floodplain rivers, which, in their intact state, regularly (seasonally) flood their floodplains. When the floodplains were flooded, as still occurs in the few remaining unregulated rivers (e.g. Ovens River, Victoria), there is a boom of primary production (bacteria, phytoplankton, macrophytes, tree growth) followed by a pulse of secondary production both of aquatic (zooplankton, macroinvertebrates, fish) and terrestrial fauna (e.g. birds, amphibians, reptiles). The high primary production is fuelled by nutrients coming in with the flood but also by nutrients and organic carbon released from the floodplain (Baldwin & Mitchell 2000). Flooded, intact floodplains are one of the most productive types of ecosystems in the world. The loss of that ecological production arising from river regulation and floodplain alienation in dammed lowland rivers is known, but its size and value are seldom acknowledged in developing outcomes for managed flows. Floods in upland rivers are pulse (sometimes intense) disturbances, whereas in floodplain rivers, floods are regenerative or restorative disturbances, notwithstanding some disruptions of the terrestrial biota (Lake et al. 2006). The ongoing viability of the biota of floodplain ecosystems lies in their capacity to capitalize on floods and to survive the dry periods between floods. To maintain the ecological integrity of floodplains, regular flooding covering the floodplain is essential.

Key parameters and practices controlling pesticide degradation efficiency of biobed substrates

We studied the contribution of each of the components of a compost-based biomixture (BX), commonly used in Europe, on pesticide degradation. The impact of other key parameters including pesticide dose, temperature and repeated applications on the degradation of eight pesticides, applied as a mixture, in a BX and a peat-based biomixture (OBX) was compared and contrasted to their degradation in soil. Incubation studies showed that straw was essential in maintaining a high pesticide degradation capacity of the biomixture, whereas compost, when mixed with soil, retarded pesticide degradation. The highest rates of degradation were shown in the biomixture composed of soil/compost/straw suggesting that all three components are essential for maximum biobed performance. Increasing doses prolonged the persistence of most pesticides with biomixtures showing a higher tolerance to high pesticide dose levels compared to soil. Increasing the incubation temperature from 15°C to 25°C resulted in lower t1/2 values, with biomixtures performing better than soil at the lower temperature. Repeated applications led to a decrease in the degradation rates of most pesticides in all the substrates, with the exception of iprodione and metalaxyl. Overall, our results stress the ability of biomixtures to perform better than soil under unfavorable conditions and extreme pesticide dose levels.

Long-term persistence of various 14C-labeled pesticides in soils

The fate of the 14C-labeled herbicides ethidimuron (ETD), methabenzthiazuron (MBT), and the fungicide anilazine (ANI) in soils was evaluated after long-term aging (9–17 years) in field based lysimeters subject to crop rotation. Analysis of residual 14C activity in the soils revealed 19% (ETD soil; 0–10 cm depth), 35% (MBT soil; 0–30), and 43% (ANI soil; 0–30) of the total initially applied. Accelerated solvent extraction yielded 90% (ETD soil), 26% (MBT soil), and 41% (ANI soil) of residual pesticide 14C activity in the samples. LC-MS/MS analysis revealed the parent compounds ETD and MBT, accounting for 3% and 2% of applied active ingredient in the soil layer, as well as dihydroxy-anilazine as the primary ANI metabolite. The results for ETD and MBT were matching with values obtained from samples of a 12 year old field plot experiment. The data demonstrate the long-term persistence of these pesticides in soils based on outdoor trials.

Assessing the chemical and biological accessibility of the herbicide isoproturon in soil amended with biochar

There is considerable current interest in using biochar (BC) as a soil amendment to sequester carbon to mitigate climate change. However, the implications of adding BC to agricultural soil for the environmental fate of pesticides remain unclear. In particular, the effect of biochars on desorption behavior of compounds is poorly understood. This study examined the influence of BC on pesticide chemical and biological accessibility using the herbicide isoproturon (IPU). Soils amended with 1% and 2% BC showed enhanced sorption, slower desorption, and reduced biodegradation of IPU. Addition of 0.1% BC had no effect on sorption, desorption or biodegradation of IPU. However, the mineralization of 14C-IPU was reduced by all BC concentrations, reducing by 13.6%, 40.1% and 49.8% at BC concentrations of 0.1%, 1% and 2% respectively. Further, the ratio of the toxic metabolite 4-isopropyl-aniline to intact IPU was substantially reduced by higher BC concentrations. Hydroxypropyl-β-cyclodextrin (HPCD) extractions were used to estimate the IPU bioaccessibility in the BC-amended soil. Significant correlations were found between HPCD-extracted 14C-IPU and the IPU desorbed (%) (r2=0.8518, p<0.01), and also the 14C-IPU mineralized (%) (r2=0.733; p<0.01) for all BC-amended soils. This study clearly demonstrates how desorption in the presence of BC is intimately related to pesticide biodegradation by the indigenous soil microbiota. BC application to agricultural soils can affect the persistence of pesticides as well as the fate of their degradation products. This has important implications for the effectiveness of pesticides as well as the sequestration of contaminants in soils.

Coelomic fluid: a complimentary biological medium to assess sub-lethal endosulfan exposure using 1H NMR-based earthworm metabolomics

Endosulfan is an environmentally persistent pesticide and has been shown to be genotoxic, neurotoxic and carcinogenic to surrounding organisms. Earthworms are widely used in environmental metabolomic studies to assess soil ecotoxicity. Previous nuclear magnetic resonance (NMR)-based metabolomic studies have analyzed earthworm tissue extracts after exposure to endosulfan and identified some key metabolic indicators that can be used as biomarkers of stress. However, some metabolites may have been masked due to overlap with other metabolites in the tissue extract. Therefore, in this study, the coelomic fluid (CF) and the tissue extract of the earthworm, Eisenia fetida, were both investigated using ¹H NMR-based metabolomics to analyze their metabolic profile in response to endosulfan exposure at three sub-lethal (below LC₅₀) concentrations. Principal component analysis determined the earthworm CF and earthworm tissue extract to both have significant separation between the exposed and control at the two highest sub-lethal endosulfan exposures (1.0 and 2.0 μg cm⁻²). Alanine, glycine, malate, α-ketoglutarate, succinate, betaine, myo-inositol, lactate and spermidine in the earthworm CF and alanine, glutamine, fumarate, glutamate, maltose, melibiose, ATP and lactate in earthworm tissue extract were all detected as having significant fluctuations after endosulfan exposure. An increase in ATP production was detected by the increase activity in the citric acid cycle and by anaerobic metabolism. A significant decrease in the polyamine, spermidine after endosulfan exposure describes an apoptotic mode of protection which correlates to a previous endosulfan exposure study where DNA damage has been reported. This study highlights that earthworm CF is a complementary biological medium to tissue extracts and can be helpful to better understand the toxic mode of action of contaminants at sub-lethal levels in the environment.

Potential for Abiotic Reduction of Pesticides in Prairie Pothole Porewaters

Prairie pothole lakes (PPLs) are critical hydrological and ecological components of central North America and represent one of the largest inland wetland systems on Earth. These lakes are located within an agricultural region, and many of them are subject to nonpoint-source pesticide pollution. Limited attention, however, has been paid to understanding the impact of PPL water chemistry on the fate and persistence of pesticides. In this study, the abiotic reductive transformation of seven dinitroaniline pesticides was investigated in PPL sediment porewaters containing naturally abundant levels of reduced sulfur species (i.e., bisulfide (HS(-)) and polysulfides (S(n)(2-))) and dissolved organic matter (DOM). Target dinitroanilines underwent rapid degradation in PPL porewaters and were transformed into corresponding amine products. While the largest fraction of the transformation could be attributed to reduced sulfur species, experimental evidence suggested that other reactive entities in PPL porewaters, such as DOM and mineral phases, might also affect the reaction rates of dinitroanilines. Results from this study highlight the importance of reductive transformation as an abiotic natural attenuation pathway for pesticides entering the PPL sedimentary environment.

Immobilization of Pseudomonas sp. strain ADP: A stable inoculant for the bioremediation of atrazine

Storage and delivery of beneficial microorganisms are fundamental issues determining their value and effectiveness for a wide range of industrial and environmental purposes. One such application is the use of bacteria for the remediation of soil pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and persistent pesticides. Liquid cultures of a candidate for atrazine degradation in soil and water, Pseudomonas sp. strain ADP (3.67×109 colony-forming units, cfu/mL), when stored at 4 and 25°C, showed a 1 log reduction in cfu/mL occurs after approximately 4 and 2weeks, respectively. When immobilized onto natural zeolite from two sources (a New Zealand and an Australian quarry) and stored in open containers exposed to the atmosphere, survival at 25°C was poor. However, when the cells were immobilized onto the Australian zeolite with xanthan gum and stored in closed containers, survival at 25°C was superior to control cells stored at 4°C. The initial growth medium, zeolite substratum and immobilization matrix excipients all appear to play an important role in the stabilization of Pseudomonas sp. strain ADP. The bacteria immobilized onto Australian zeolite with xanthan remained viable within 1 log unit of initial cfu/g loading and retained their ability to degrade atrazine (as measured by zone clearance on atrazine containing plates) for at least 10weeks at 25°C.

Degradation and Detoxification of Persistent Organic Pollutants in Soils by Plant Alkaloid Anabasine

The development of a technology employing materials containing specific alkaloids from biomasses of agricultural production would be extremely beneficial and relatively inexpensive for the remediation of polluted soils and may represent a possible new industrial and commercial opportunity. We have studied detoxification and degradation of persistent chloroorganic pesticides by using plant extracts, which contained alkaloids. Reactions DDT with alkaloid Anabasine and extractive sum of alkaloids, isolated from ground up part plant Anabasis аphylla proceed more easy without solvent. It is established, that at interaction alkaloids of Anabasis aphylla with pesticide DDT occurs degradation to formation of less toxic DDE. Results the carried out researches on studying interaction sum of alkaloids, isolated from ground up part plant Anabasis Ahylla, with DDT in various ratio (1:1, 2:1, 3:1) have shown, that thus there are detoxification pesticide DDT on 35% - 45%, 75% - 80% and 80% - 85% according to formation dichlorodiphenyldichloroethylene (DDE), and in presence humic acids the degree degradation achieves to 95% - 97%.

Steviaside Containing Plant as Deconstractive (Degradative) Agent for Persistent Organic Pollutants

Steviaside containing plant extracts have been used for degradation of persistent chloroorganic pesticides. Reactions between DDT and Steviaside or sum of extractive substances isolated from ground up part of plant Stevia were studied to give of less toxic DDE. Herein researches on studying interaction sum of polysaccharides of Stevia with DDT in various ratios resulted also. The GC-MS and GLC methods were used for analyzing degradation degree of pesticides and to determine obtained compounds. Treat HCCH by water extract of Stevia basically formed tetrachlorocyclo-hexadiene (HCH) with 86.9% yield and in particularly formed of tri-, tetrachlorobenzenes. The HCH formed in 79.7% on treat pesticide by 80% Steviaside. Degradation of HCCH and DDT by water extract of Stevia in a presence of Ana-basine in a ratio of 2:1:1 occur to degrade of HCCH up to 70-80%, and DDT on 25% - 30%.

Concerns of Environmental Persistence of Pesticides and Human Chronic Diseases

Copyright: © 2012 Mostafalou S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The connection between exposure to pesticides, chemicals used to control pests, and incidence of the chronic diseases affecting public health has been under attention of scientists in the recent years. Chronic diseases arisen from unknown sources have been identified as the leading cause of death in the world or the health problems that negatively affect quality of life. Based on the first Global Status Report on Noncommunicable Diseases released by the World Health Organization (WHO) in 2010, cancer, cardiovascular disease, chronic respiratory diseases, and diabetes were announced of killing tens of millions people in 2008 and surprisingly most of them occurred under age of 60. Irrespective of identified risk factors like inheritance, physical inactivity, rich diet, smoking, and alcoholism, investigations continue to explore the role of environmental contaminants in developing these disorders [1].

Evaluation of soil contamination in intensive agricultural areas by pesticides and organic pollutants: south-eastern Spain as a case study

A comprehensive survey of the occurrence and fate of pesticides and organic contaminants in soils from an intensive agricultural area devoted to horticultural production in plastic-based greenhouses has been performed to determine if the operation under integrated pest management practices has contributed to reduce the levels of these compounds. Almería province (south-eastern Spain) was selected for the case study. 38 agricultural soil samples (each sample corresponds to an independent private greenhouse) of areas working under integrated pest management (IPM) programs have been analyzed in order to evaluate their contamination fate. Sampling was designed to cover an area of about 400 km(2). Pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phenolic compounds and di-(2-ethylhexyl)phthalate (DEHP) were monitored. The obtained results were compared to other studies reported in Spain and Europe. Among relevant persistent pesticides, DDTs and endosulfans were mainly found and the results indicated historical application, although recent application of endosulfan was rarely detected. PAHs were also found but to a lesser extent and derived from pyrogenic sources. DEHP levels were considerably higher in comparison to the other monitored analytes. The evaluation revealed that despite the use of IPM programs, pesticide and organic contaminants are still being detected in this type of agricultural soil, although at relatively low concentration levels. In general, the contamination rate was similar or lower in comparison to other agricultural areas from nearby regions or countries. However, further monitoring studies should be carried out to establish the possible reduction in contamination by the selected compounds.

Pesticide removal from waste spray-tank water by organoclay adsorption after field application: an approach for a formulation of cyprodinil containing antifoaming/defoaming agents

Many reports on purification of water containing pesticides are based on studies using unformulated active ingredients. However, most commercial formulations contain additives/adjuvants or are manufactured using microencapsulation which may influence the purification process. Therefore, the main objective of this work was to develop and test a pilot scheme for decontaminating water containing pesticides formulated with antifoaming/defoaming agents. The Freundlich adsorption coefficients of formulation of cyprodinil, a new-generation fungicide, onto the organoclay Cloisite 20A have been determined in the laboratory in order to predict the efficiency of this organoclay in removing the fungicide from waste spray-tank water. Subsequently, the adsorption tests were repeated in the pilot system in order to test the practical operation of the purification scheme. The laboratory adsorption tests successfully predicted the efficiency of the pilot purification system, which removed more than 96% cyprodinil over a few hours. The passing of the organoclay-cyprodinil suspension through a layer of biomass gave 100% recovery of the organoclay at the surface of the biomass after 1 week. The organoclay was composted after the treatment to try to break down the fungicide so as to allow safe disposal of the waste, but cyprodinil was not significantly dissipated after 90 days. The purification scheme proved to be efficient for decontaminating water containing cyprodinil formulated with antifoaming/defoaming agents, but additional treatments for the adsorbed residues still appear to be necessary even for a moderately persistent pesticide such as cyprodinil. Furthermore, a significant conclusion of this study concerns the high influence of pesticide formulations on the process of purification of water containing these compounds, which should be taken into account when developing innovative decontamination schemes, especially for practical applications.

Assessing the Endosulfan Contamination in an Unconfined Aquifer

Groundwater samples were analyzed in order to elucidate the fate of endosulfan in the soil and its release mechanism into water of an unconfined aquifer. Residual alfa endosulfan was determined in all the wells; however, beta endosulfan was below 0.001 μg/L. Maximum adsorption rates of alfa and beta endosulfan were 91%-86% on the topsoil; 87%-91% on the subsoil, respectively. About 13%-23% desorption rate on the topsoil and subsoil exhibited the probability of endosulfan movement in the soil. The study showed that a hydrophobic-moderately persistent pesticide can reach to groundwater despite the high clay content of soil.

Discriminating Multiple Impacts of Biogas Residues Amendment in Selectively Decontaminating Chloroacetanilide Herbicides

There is increasing concern about modifications to pesticide persistence in soil from the application of organic wastes as fertilizers. This study was conducted to discriminate the multiple effects of biogas residues (BR) amendment, including soil nutrients, soil microbial activity and biodiversity, and adsorption and degradation of chloroacetanilide herbicides (acetochlor, metolachlor, and butachlor). Addition of BR to soil increased the release of organic materials (i.e., dissolved organic carbon, dissolved organic nitrogen, and active phosphorus). It not only stimulated soil microorganisms and caused changes to microorganism diversity but also increased herbicide adsorption. Such multiple effects led to selective decontamination of chloroacetanilide herbicides, depending on herbicide structures and BR amendment levels. Stereoselectivity in degradation of acetochlor and metolachlor with biphasic character was magnified by BR amendment, which was well explained by integrating the impacts of BR amendment. Interestingly, BR amendment induced significant accumulation of herbicidally active aS,CS-metolachlor, facilitating the utilization of herbicidal activity.

Reduction of the movement and persistence of pesticides in soil through common agronomic practices

Laboratory and field studies were conducted in order to determine the leaching potential of eight pesticides commonly used during pepper cultivation by use of disturbed soil columns and field lysimeters, respectively. Two soils with different organic matter content (soils A and B) were used. Additionally, soil B was amended with compost (sheep manure). The tested compounds were cypermethrin, chlorpyrifos-methyl, bifenthrin, chlorpyrifos, cyfluthrin, endosulfan, malathion and tolclofos-methyl. In soil B (lower organic matter content), only endosulfan sulphate, malathion and tolclofos-methyl were found in leachates. For the soil A (higher organic matter content) and amended soil B, pesticide residues were not found in the leachates. In addition, this paper reports on the use of common agronomic practices (solarization and biosolarization) to enhance degradation of these pesticides from polluted soil A. The results showed that both solarization and biosolarization enhanced the degradation rates of endosulfan, bifenthrin and tolclofos-methyl compared with the control. Most of the studied pesticides showed similar behavior under solarization and biosolarization conditions. However, chlorpyrifos was degraded to a greater extent in the solarization than in biosolarization treatment. The results obtained point to the interest in the use of organic amendment in reducing the pollution of groundwater by pesticide drainage and in the use of solarization and biosolarization in reducing the persistence of pesticides in soil.

Assessment of pesticide residues in commonly used vegetables in Hyderabad, Pakistan

The aim of present study was to assess pesticide residues in vegetables in the Hyderabad region of Pakistan. The concentrations of six pesticides were determined by gas chromatography coupled with mass selective detector (GC–MSD) in locally produced vegetables purchased from wholesale markets. A total of 200 samples of eight vegetables viz. cauliflower, green chilli, eggplant, tomato, peas, bitter gourd, spinach and apple gourd were analyzed for pesticide residues. The results indicated that almost all samples were contained pesticides, only 39% contained pesticide residues at or below maximum residue limits (MRLs), and 61% contained pesticide residues above MRLs. From the six analyzed pesticides, carbofuran and chlorpyrifos were found above to MRLs with concentrations ranging from 0.01–0.39 and 0.05–0.96 mg/kg, respectively. The results provided important information on the current pesticide contamination status of some commonly used vegetables and pointed an urgent need to control the use of some excessively applied and potentially persistent pesticides, such as carbofuran and chlorpyrifos.