Chlorpyrifos In Soil Research Articles

The situation of chlorpyrifos in Mexico: a case study in environmental samples and aquatic organisms.

Chlorpyrifos (CPF) is one of the most commonly used organophosphate pesticides. Because CPF was described as a toxic compound without safe levels of exposure for children, certain countries in Latin America and the European Union have banned or restricted its use; however, in Mexico it is used very frequently. The aim of this study was to describe the current situation of CPF in Mexico, as well as its use, commercialization, and presence in soil, water, and aquatic organisms in an agricultural region of Mexico. Structured questionnaires were applied to pesticide retailers to determine the sales pattern of CPF (ethyl and methyl); in addition, monthly censuses were conducted with empty pesticide containers to assess the CPF pattern of use. Furthermore, samples of soil (48 samples), water (51 samples), and fish (31 samples) were collected, which were analyzed chromatographically. Descriptive statistics were performed. The results indicate that CPF was one of the most sold (3.82%) and employed OP (14.74%) during 2021. Only one soil sample was found above the CPF limit of quantification (LOQ); in contrast, all water samples had CPF levels above the LOQ (x̄ = 4614.2ng/L of CPF). In the case of fish samples, 6.45% demonstrated the presence of methyl-CPF. In conclusion, the information obtained in this study indicates the need for constant monitoring in the area, since the presence of CPF in soil, water, and fish constitutes a threat to the health of wildlife and humans. Therefore, CPF should be banned in Mexico to avoid a serious neurocognitive health problem.

Ecological safety evaluation of chlorpyrifos on agricultural soil: Effects on soil microbes

The health of farmland soils is directly related to the proper application of pesticides. Chlorpyrifos is a widely used broad-spectrum organophosphorus insecticide, and its ecological security risk to farmland soils requires evaluation. A trial was conducted to study the effects of chlorpyrifos on soil microbes in a wheat–maize rotation field. A 45 % chlorpyrifos emulsion was sprayed at the recommended and dual doses, after which the chlorpyrifos residue, soil microbial content, bacterial community structure, functional microbial abundance, and enzyme activities were measured. The results showed that chlorpyrifos had a half-life of 8.94–9.88 and 2.17–2.18 days in soil for wheat and maize, respectively. Although the final chlorpyrifos residues in the crop grains were lower than the maximum residue limit recommended by the Chinese government, soil fungal abundance was significantly inhibited, and the structure and function of soil bacterial communities were disturbed. Furthermore, the quantities of nitrification-related genera (Acidobacteria GP4 and Acidobacteria GP6) and functional genes (AOB-amoA and AOA-amoA) decreased, whereas those of denitrification-related functional genes (nirS and nirK) and urease activity increased. Gemmatimonas and alkaline phosphatase involved in phosphorus cycling were activated, and the abundance of cbbLR and cbbLG genes involved in carbon fixation decreased. The integrated biomarker response index showed that nirK and β-glucosidase were the most sensitive indicators in wheat and maize stages. The present study provides toxicological data and theoretical guidance for the ecological safety evaluation and rational application of chlorpyrifos in soil.

Comparison of peroxodisulfate and peroxymonosulfate activated by microwave for degradation of chlorpyrifos in soil: Effects of microwaves, reaction mechanisms and degradation products

The combination of microwave (MW) and persulfate (PS, including peroxodisulfate (PDS) and peroxymonosulfate (PMS)) has been proved to be a potential method for degradation of organic pollutant. In this study, the degradation of chlorpyrifos (CPF) in soil by MW/PDS and MW/PMS was investigated. As a result, a synergistic effect was created between MW and PS. Compared with conventional heating (CH) providing thermal effect, MW also played a special non-thermal effect for PDS activation, causing superior CPF degradation by MW/PDS. However, the similar degradation efficiency of CPF in MW/PMS system and CH/PMS system indicated mainly a thermal effect was played by MW in MW/PMS system. The generation of reactive oxygen species (ROS) was explored in detail, SO4•− and •OH, generated in water, was the main ROS in MW/PDS system, and 1O2, generated in soil/water interface, was the main ROS in MW/PMS system. 100:1 of PS to CPF molar ratio, 1:1 of water and soil mass ratio were selected as appropriate reaction conditions. Environmental factors including pH and humic acid showed different effects on CPF degradation in MW/PDS system and MW/PMS system. Moreover, the degradation products were different due to different selectivity of ROS, reaction pathways were predicted based on Gaussian calculation and detected products. In addition, toxicity prediction, energy estimation and the applicability in different types of soils were investigated for practical significance of CPF degradation by MW/PS. Therefore, MW/PS provides a promising approach for remediation of CPF-contaminated soils.

Chlorpyrifos Occurrence and Toxicological Risk Assessment: A Review.

Chlorpyrifos (CPF) was the most frequently used pesticide in food production in the European Union (EU) until 2020. Unfortunately, this compound is still being applied in other parts of the world. National monitoring of pesticides conducted in various countries indicates the presence of CPF in soil, food, and water, which may have toxic effects on consumers, farmers, and animal health. In addition, CPF may influence changes in the population of fungi, bacteria, and actinomycete in soil and can inhibit nitrogen mineralization. The mechanisms of CPF activity are based on the inhibition of acetylcholinesterase (AChE) activity. This compound also exhibits reproductive toxicity, neurotoxicity, and genotoxicity. The problem seems to be the discrepancy between the actual observations and the final conclusions drawn for the substance’s approval in reports presenting the toxic impact of CPF on human health. Therefore, this influence is still a current and important issue that requires continuous monitoring despite its withdrawal from the market in the EU. This review traces the scientific reports describing the effects of CPF resulting in changes occurring in both the environment and at the cellular and tissue level in humans and animals. It also provides an insight into the hazards and risks to human health in food consumer products in which CPF has been detected.

Remediation of chlorpyrifos in soil using immobilized bacterial consortium biostimulated with organic amendment

Pesticides released into the environment have become a danger to the mother earth arousing a worldwide alert to initiate remediation at the point sources of contamination in an ecofriendly way. The recent advances in bioremediation technology using microbial consortium have been found effective for the treatment of pesticides in soil. In this context, the present study evaluates and compares the ability of an assembled bacterial consortium C5 (Staphylococcus warneri CPI 2, Pseudomonas putida CPI 9 and Stenotrophomonas maltophilia CPI 15) to remove chlorpyrifos in soil in its free cells state and immobilized state on wood chips. Chlorpyrifos degradation by C5 was studied via a pot study experiment with completely randomized block design. A comparative analysis of degradation, total microbial count and dehydrogenase activity was performed in soils with and without chlorpyrifos application history and under amendment with a mix of cow dung and mushroom spent as biostimulant. Based on ANOVA results, the treatments T3 and T7, both received immobilized C5 and biostimulant were found to be the best giving complete degradation of 125 mg kg−1 of chlorpyrifos in 30 days. All the studied factors – degradation, microbial count and dehydrogenase activity were higher in the soil with chlorpyrifos exposure history. The results presented here highlight the potential use of wood chip immobilized consortium C5 biostimulated with a mix of cow dung and mushroom spent for remediating chlorpyrifos effectively in contaminated soil.

Comparison of Mw/Pds System and Mw/Pms System for Degradation of Chlorpyrifos in Soil: Mechanism and Products

Comparison of Mw/Pds System and Mw/Pms System for Degradation of Chlorpyrifos in Soil: Mechanism and Products

Biodegradation of chlorpyrifos using isolates \xa0from contaminated agricultural soil, its kinetic studies

Extensive pesticides use is negatively disturbing the environment and humans. Pesticide bioremediation with eco-friendly techniques bears prime importance. This study evaluates the bioremediation of chlorpyrifos in soil using indigenous Bacillus cereus Ct3, isolated from cotton growing soils. Strains were identified through ribotyping (16s rRNA) by Macrogen (Macrogen Inc. Geumchen-gu, South Korea). Bacillus cereus Ct3 was resistant up to 125 mg L−1 of chlorpyrifos and successfully degraded 88% of chlorpyfifos in 8 days at pH 8. Bacillus cereus Ct3 tolerated about 30–40 °C of temperature, this is a good sign for in situ bioremediation. Green compost, farmyard manure and rice husk were tested, where ANOVA (P < 0.05) and Plackett–Burman design, results indicated that the farm yard manure has significant impact on degradation. It reduced the lag phase and brought maximum degradation up to 88%. Inoculum size is a statistically significant (P < 0.05) factor and below 106 (CFU g−1) show lag phase of 4–6 days. Michaelis–Menten model results were as follows; R2 = 0.9919, Vmax = 18.8, Ks = 121.4 and Vmax/Ks = 0.1546. GC–MS study revealed that chlorpyrifos first converted into diethylthiophosphoric acid and 3,5,6-trichloro-2-pyridinol (TCP). Later, TCP ring was broken and it was completely mineralized without any toxic byproduct. Plackett–Burman design was employed to investigate the effect of five factors. The correlation coefficient (R2) between experimental and predicted value is 0.94. Central composite design (CBD) was employed with design matrix of thirty one predicted and experimental values of chlorpyrifos degradation, having “lack of fit P value” of “0.00”. The regression coefficient obtained was R2 = 0.93 which indicate that the experimental vales and the predicted values are closely fitted. The most significant factors highlighted in CBD/ANOVA and surface response plots were chlorpyrifor concentration and inoculum size. Bacillus cereus Ct3 effectively degraded chlorpyrifos and can successfully be used for bioremediation of chlorpyrifos contaminated soils.

Detection and Quantification of Chlorpyrifos in Soil, Milk, Dip Wash, Spray Race Residues Using High Performance Liquid Chromatography in Selected Dairy Farms in Kenya

Organophosphate acaricides are well known for their extensive use in livestock for the management of Ticks and Tick borne diseases. However, the intensive use of Chlorpyrifos causes environmental pollution due to their residues accumulation. The study was aimed at detection and quantification of Chlorpyrifos in soil, dip wash, spray race residues, milk and milk products from Kilifi, Nakuru and Kajiado Counties. A baseline survey was conducted through a cross-sectional study using questionnaire, formal interview and personal observation to collect data and information on the use and type of acaricides. Thereafter soil, dip wash, spray race residues, milk and milk products from the farmers using acaricides containing Chlorpyrifos as the active compound were collected, analyzed and quantified for the presence of Chlorpyrifos using HPLC. Data obtained was stored in excel spread sheets coded and analyzed using Statistical Package for social Scientists (SPSS). Chemicals used for killing ticks included TRIATIX (12), DUODIP (11), and STELADONE (7) among others with majority of the farmers spraying once a week. Out of 11 samples collected from spray race and dip wash, 7 samples were positive for Chlorpyrifos. Nine (9) samples from the analyzed 27 samples of milk and milk products were Chlorpyrifos positive. Chlorpyrifos was also detected in 6 samples out of the 28 soil samples whereas 5 water samples from the 25 collected sample were positive of chlorpyrifos. Chlorpyrifos was not detected in milk and milk product from Kajiado County. However, the concentration of Chlorpyrifos ranged between 1.000±0.242 mgL^-1 and 2.854±0.149 mgL^-1 in Nakuru County and between 1.930±0.106 mgL^-1 and 2.017±0.049 mgL^-1 in Kilifi County. The positive soil samples were from Nakuru County with concentration ranges between 0.915±0.048 mgL^-1 to 8.556±0.549 mgL^-1. The Nakuru water samples had chlorpyrifos concentration ranging between 0.888±0.180 mgL^-1 to 1.870±0.0243 mgL^-1. The dip wash and spray race samples had a Chlorpyrifos ranges of 0.918±0.217 mgL^-1 (Kajiado County) and 3.282±0.140 mgL^-1 (Nakuru County). The study concludes that there is accumulation of Chlorpyrifos in soil, water, dip wash and spray race and milk and milk products beyond the acceptable limit set at 0 to 0.01 mg/kg body weight by WHO. The concentration of Chlorpyrifos in Nakuru County were found to be higher cozampared to Kilifi and Kajiado County. Surveillance, monitoring and regulation on the use of Chlorpyrifos in manufacturing acaricides is highly recommended.

Soil persistence and environmental risk assessment of chlorpyrifos under different organic manuring in the tropical sugarcane ecosystem

ABSTRACT Chlorpyrifos has label claim against sugarcane termites and is applied as a soil drench at planting. The organic manures viz., composted coir pith, farmyard manure, press mud and sugarcane trash are also applied at the time of planting mainly to conserve the soil moisture in the tropical environment. The organic manures may have some impact on the persistence of chlorpyrifos in the soil. Hence, the persistence of chlorpyrifos in the manurial soils was studied by employing the single-step sample preparation method and GC-ECD. The initial deposits of chlorpyrifos were 0.325–0.383 µg/g across the treatments involved in the study. The residues were quantified up to 75 days after treatment (DAT) and were below 0.01 µg/g on 90th DAT. The soil half-lives of chlorpyrifos were in the range of 19.8–21.0 days in the manured soils as against 18.7 days in the control soil. Thus, the organic manures applied at planting did not play any significant role in influencing the persistence of chlorpyrifos in the sandy clay loam soil of tropical sugarcane ecosystem. Further, the chlorpyrifos residues were not detected in the sugarcane leaf and stalk, indicating that there was no significant uptake by the plant from the soil. The calculated risk quotient values indicated that the chlorpyrifos residues may pose an unacceptable risk to earthworms during the first week of its application and thereafter, there could be a moderate level of risk in the tropical sugarcane environment.

Adsorption-desorption of chlorpyrifos in soils and sediments from the Rufiji Delta, Tanzania

Batch adsorption-desorption equilibrium techniques were used to investigate the adsorption capacity and influence of salinity on partitioning of the insecticide chlorpyrifos between water and soil or water and sediments from the Rufiji Delta. The data were fitted to different adsorption-desorption models and the hysteresis index was calculated using the ratio between the Freundlich exponents for desorption and adsorption, and secondly, the difference in area under the normalized adsorption and desorption isotherms using the maximum adsorbed and solution concentrations. The data showed non-linear adsorption and that chlorpyrifos was strongly adsorbed to soil and sediments from the Rufiji Delta. The linearized adsorption coefficient (KD) and Freundlich adsorption coefficient (Kf) correlated significantly with organic carbon content. Chlorpyrifos adsorption as well as hysteresis calculated by both methods decreased with salinity (i.e. the sediment adsorbs increasing amounts of chlorpyrifos with decreasing salinity). This indicates that settling of freshwater sediments is among the major removal pathways of the chemical from the water column, but increased turbulence during high tides may resuspend settled sediment simultaneously increasing salinity and re-dissolve chlorpyrifos. However, discharge of fresh water, particularly during heavy rains, increases the trapping efficiency of the sediments. The theoretical approach developed showed that the Langmuir model describes the desorption data better than the Freundlich model, and that a better index of hysteresis is one that considers areas under the adsorption and desorption isotherms, provided the desorption isotherm is described by the normalized Langmuir isotherm and the adsorption isotherm by the normalized Freundlich isotherm.

Degradation of chlorpyrifos in soil using laccase immobilized iron oxide nanoparticles and their competent role in deterring the mobility of chlorpyrifos.

Covalent-immobilization of the laccase enzyme onto the iron oxide nanoparticles was achieved using N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDAC) as cross-linkers. The presence of sulphur moeity in the laccase immobilized nanoparticles (LNPs) observed through Scanning Electron Microscopy- Energy dispersive X-ray spectroscopy (SEM-EDS) spectra confirmed the immobilization of laccase enzyme. The TEM analysis of iron oxide nanoparticles (FNPs), chitosan coated iron nanoparticles (CNPs) and laccase immobilized nanoparticles (LNPs) confirmed their sizes around 12, 15 and 20nm, respectively. The effect of LNPs in degrading chlorpyrifos under field conditions was studied by simulating the conditions in a column. Column A, which was used as control showed more leaching of chlorpyrifos as compared to column B containing LNPs. The sorption coefficient (Kd) value obtained for control (column A) and LNPs containing column B were 21.6 and 112.3L/kg, respectively. LNPs altered the Kd values of soil thereby showing lesser leaching potential. Higher the Kd value, lesser will be the leaching potential in the ground water. Copper in laccase enzyme resulted in hydrolysis of chlorpyrifos. Chitosan used for coating on FNPs and soil organic matter resulted in the adsoption of chlorpyrifos. Current results will allow a better assessment of the role of LNPs as a competent deterrent in chlorpyrifos mobility and degradation.

Mesoporous structured molecularly imprinted polymer with restricted access function for highly selective extraction of chlorpyrifos from soil

Mesoporous structured molecularly imprinted polymers combined with restricted access materials (RAM-M-MIPs) were synthesized in this work, then RAM-M-MIPs were used as adsorbents in matrix solid phase dispersion (MSPD) to extract chlorpyrifos residues from soil. The RAM-M-MIPs with mesoporous structure increased adsorptive capacity and accelerated adsorption rate. At the same time, the RAM-M-MIPs with restricted access function showed good exclusion effect toward humic acid in the soil. In addition, the characteristics of RAM-M-MIPs were measured and the optimal experimental conditions of MSPD were explored. In MSPD, the extraction and clean-up procedures can be finished simultaneously, which saved the extraction time. The analyte eluted from soil was determined by LC–MS/MS. The recoveries were in the range of 93.5–106.1% and the relative standard deviations were in the range of 2.8–5.7% at the spiked soil levels of 0.10–10.00 ng g−1, the detection limit was 0.015 ng g−1. Based on these analytical validation results, the developed method can be a useful method to determine chlorpyrifos in soil.

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.

Low-density polyethylene microplastics as a source and carriers of agrochemicals to soil and earthworms

Environmental contextMicroplastics, long recognised as contaminants in aquatic ecosystems, are increasingly of environmental concern for terrestrial ecosystems. This study focuses on the potential of microplastics to act as carriers of agrochemicals and the subsequent effects on soil biota. The results indicate the need for further studies into how soil properties influence both the degradation of microplastics and their role as pollutant carriers. AbstractMicroplastics (MPs) are of environmental concern to marine ecosystems owing to the evidence of their presence in and adverse effects on organisms, but studies to address this problem on soils and its biota are scarce. Several questions can arise related to this major environmental problem and its impact on terrestrial ecosystems, mainly, whether MPs can transport contaminants (e.g. pesticides) to the soil matrix and if they can be a carrier of pesticides to soil biota. To contribute to the understanding of these issues, earthworms (Eisenia fetida) were exposed for 14 days to soil containing two different sized MPs (5mm and 0.25 µm–1mm) that were either previously sprayed or not with chlorpyrifos (CPF). Acetylcholinesterase (AChE) activity and thiobarbituric acid reactive substances (TBARS) were measured to track the exposure of the earthworms to MPs, both non-sprayed and sprayed with CPF. The behaviour of the earthworms in the test containers and the movement of MPs in the soil were assessed. The concentration of CPF in soil at the end of the experiment differed between the treatments with MPs of different sizes (17.9ngg−1 and 2442ngg−1 for large and small MPs, respectively). Despite the ability of the MPs to release CPF to the soil, the earthworms avoided the contaminated MPs at the highest contaminant level. At a lower concentration of CPF (large MPs), the earthworms avoided the MPs, but the contact time with contaminated soil was higher, as shown by the enhanced level of TBARs and AChE inhibition. However, no evidence of MPs uptake was recorded, thus it was not demonstrated that MPs can be carriers of pesticides to earthworms.

Translocation of chlorpyrifos residue from soil to Korean cabbage

The loss of residual chlorpyrifos in soil and the amount translocated to Korean cabbage were investigated in this study. Field trials with Korean cabbage were carried out in two greenhouses located in Yongin (Field 1) and Gwangju (Field 2). Soil and Korean cabbage samples were collected on different days following the treatment of soil with chlorpyrifos at two different rates. The initial amounts of residue in soil were 1.15 and 3.58 mg/kg, and these decreased to 0.22 and 0.49 mg/kg at 36 days after treatment (DAT) in Field 1. These values were 20.9 and 59.3 mg/kg, decreasing to 3.03 and 5.24 mg/kg at 43 DAT in Field 2, respectively. In Field 1, the half-life of chlorpyrifos was approximately 15.0 and 10.2 days in soil treated with 0.12 and 0.24 g a.i./m2, respectively. In Field 2, the half-life of chlorpyrifos was approximately 27.7 and 9.6 days following application of 0.36 and 0.72 g a.i./m2, respectively. When compared with the initial concentration in soil, the absorption ratio of chlorpyrifos residue to Korean cabbage was 0.93–6.01 and 0.57–2.61%, respectively. Therefore, safe management guidelines for chlorpyrifos in soil used to cultivate Korean cabbage may be suggested as 3.3 mg/kg regarding the maximum residue limit of chlorpyrifos on Korean cabbage (0.2 mg/kg).

Optimization of the Use of His₆-OPH-Based Enzymatic Biocatalysts for the Destruction of Chlorpyrifos in Soil.

Applying enzymatic biocatalysts based on hexahistidine-containing organophosphorus hydrolase (His6-OPH) is suggested for the decomposition of chlorpyrifos, which is actively used in agriculture in many countries. The application conditions were optimized and the following techniques was suggested to ensure the highest efficiency of the enzyme: first, the soil is alkalinized with hydrated calcitic lime Ca(OH)2, then the enzyme is introduced into the soil at a concentration of 1000 U/kg soil. Non-equilibrium low temperature plasma (NELTP)-modified zeolite is used for immobilization of the relatively inexpensive polyelectrolyte complexes containing the enzyme His6-OPH and a polyanionic polymer: poly-l-glutamic acid (PLE50) or poly-l-aspartic acid (PLD50). The soil’s humidity is then increased up to 60–80%, the top layer (10–30 cm) of soil is thoroughly stirred, and then exposed for 48–72 h. The suggested approach ensures 100% destruction of the pesticide within 72 h in soils containing as much as 100 mg/kg of chlorpyrifos. It was concluded that using this type of His6-OPH-based enzyme chemical can be the best approach for soils with relatively low humus concentrations, such as sandy and loam-sandy chestnut soils, as well as types of soil with increased alkalinity (pH 8.0–8.4). Such soils are often encountered in desert, desert-steppe, foothills, and subtropical regions where chlorpyrifos is actively used.

Use of okara in the bioremediation of chlorpyrifos in soil: Effects on soil biochemical properties

The main objective of this manuscript was to study the bioremediation capacity of okara (a byproduct of soy milk production) in soils contaminated by organic xenobiotics. To this aim, and under controlled laboratory conditions, a soil was contaminated with chlorpyrifos insecticide at a dose of 5lha−1. Okara was added to this contaminated soil in two different manners: (1) pure okara (Op); and (2) a biostimulant/biofertilizer made from pure okara using the pH-stat technique. Several enzymatic activities (dehydrogenase, urease, β-glucosidase and phosphatase) and the evolution of the insecticide in soil were studied over an 80-day period. The results suggested that both forms of okara stimulated soil microorganisms and accelerated the degradation of chlorpyrifos in soil. It was, however, the biostimulant/biofertilizer that showed the greatest acceleration in insecticide degradation, possibly due to its higher content in low molecular weight (<300Da) peptides, easily available to soil microorganisms.

Removal of pesticides and ecotoxicological changes during the simultaneous treatment of triazines and chlorpyrifos in biomixtures

Biopurification systems constitute a biological approach for the treatment of pesticide-containing wastewaters produced in agricultural activities, and contain an active core called biomixture. This work evaluated the performance of a biomixture to remove and detoxify a combination of three triazine herbicides (atrazine/terbuthylazine/terbutryn) and one insecticide (chlorpyrifos), and this efficiency was compared with dissipation in soil alone. The potential enhancement of the process was also assayed by bioaugmentation with the ligninolytic fungi Trametes versicolor. Globally, the non-bioaugmented biomixture exhibited faster pesticide removal than soil, but only in the first stages of the treatment. After 20 d, the largest pesticide removal was achieved in the biomixture, while significant removal was detected only for chlorpyrifos in soil. However, after 60 d the removal values in soil matched those achieved in the biomixture for all the pesticides. The bioaugmentation failed to enhance, and even significantly decreased the biomixture removal capacity. Final removal values were 82.8% (non-bioaugmented biomixture), 43.8% (fungal bioaugmented biomixture), and 84.7% (soil). The ecotoxicological analysis revealed rapid detoxification (from 100 to 170 TU to <1 TU in 20 d) towards Daphnia magna in the biomixture and soil, and slower in the bioaugmented biomixture, coinciding with pesticide removal. On the contrary, despite important herbicide elimination, no clear detoxification patterns were observed in the phytotoxicity towards Lactuca sativa. Findings suggest that the proposed biomixture is useful for fast removal of the target pesticides; even though soil also removes the agrochemicals, longer periods would be required. On the other hand, the use of fungal bioaugmentation is discouraged in this matrix.

Dissipation of Chlorpyrifos in a Malaysian Agricultural Soil: A Comparison between a Field Experiment and Simulation by the VARLEACH and PERSIST Models

A comparison of the dissipation of chlorpyrifos in a Malaysian agricultural soil was undertaken using data from a field experiment and simulation by the PERSIST model. The study was carried out at an oil palm estate located close to the Kuala Lumpur International Airport (KLIA), Sepang, Selangor (for field experiment). The plots were treated with chlorpyrifos at the manufacturer’s recommended dosage. Soil samples were collected according to the sampling schedule at intervals of 0, 1, 3, 7, 14, 21, 30, 60 and 90 days. Residues of chlorpyrifos in soil from the field trial were analyzed in the laboratory. Simulation of chlorpyrifos leaching and persistency was done using two computer-run software VARLEACH and PERSIST. Generally, predicted data for chlorpyrifos residue obtained using the VARLEACH and PERSIST models was found to be well matched with the observed data from the field trial. The PERSIST Prediction for chlorpyrifos residue in soils planted with oil palm trees was found to be accurate and conformed to the results observed in the field trial.

Dissipation Kinetics of Chlorpyrifos in Soils of a Vegetable Cropping System under Different Cultivation Conditions

Dissipation kinetics of chlorpyrifos in the near-neutral paddy soils of a vegetable cropping system under greenhouse, screenhouse and field conditions was studied using a rapid analytical method. The recoveries of chlorpyrifos were between 86.5% and 105.5% with relative standard deviations for repeatability between 6.6% and 9.1% at fortification levels of 0.01, 0.1 and 1 mg/kg in the soil. The limit of detection of the method was 0.004 mg/kg and the limit of quantification was found to be 0.01 mg/kg. The dissipation rates of chlorpyrifos followed the first-order kinetics and the half-life was 6.96, 6.04 and 5.20 days in the soil under greenhouse, screenhouse and field conditions, respectively. The dissipation rates of chlorpyrifos in the soil varied with different cultivation conditions. Chlorpyrifos in the soil dissipated slower in a greenhouse and screenhouse than in the open field, which was likely attributed to the hermetic environment in the greenhouse and screenhouse.