Pesticide Concentrations In Soil Research Articles

A screening study of the spatial distribution and cumulative toxicity of agricultural pesticides in the European Union’s waters

Pesticides can be an important stressor to aquatic ecosystems, and their use is strictly regulated in the European Union (EU). However, data on the use of pesticides are rather limited and poorly available, and monitoring is often insufficient to characterize their actual exposure and impact. The aim of the work presented here is to harness the limited data available and assess, for the first time, the distribution of concentrations and toxicity of 148 pesticide active substances (AS) for the whole EU. Starting from available estimates of pesticide use in agriculture and a simple screening-level model of their fate and transport, we quantify pesticide concentrations in soil and water. A comparison with monitoring data shows that predicted water concentrations are in plausible orders of magnitude, hence the model can be regarded as a first-approximation representation of the distribution of pesticides in the environment. The toxicity of individual pesticide active substances (AS) is characterized by their concentrations divided by the respective no observed effect concentrations (NOEC) for aquatic organisms, which represents the “toxic units” (TU) of each AS. The cumulative toxicity of pesticides in soils and streams of the EU is obtained by summing the TU of individual AS. We estimate that the toxicity of individual AS is generally well below 0.1 TU, indicating relatively safe environmental exposure. However, the cumulative toxicity of a mixture of AS can exceed 0.1 toxic units (TU) for more than 27% of the length of the EU’s stream network, and 1 TU for more than 4%. The cumulative toxicity at a given location is driven by only a handful of AS, but these differ from site to site reflecting the variability of pesticide use. Still, we estimate that only about 20 AS out of 148 appear among the top contributors to cumulative toxicity in most cases. While our assessment suggests a relatively widespread risk due to pesticide pollution, it also points to the important limitations concerning knowledge of pesticide use and monitoring of pesticide occurrence in the environment. These limitations need to be addressed in order to evaluate more accurately the effectiveness of EU pesticide policies. The assessment represents a proof-of-concept of a method that can be applied in support of the monitoring of pesticide policies implementation in the EU and elsewhere, once pesticide use can be estimated.

Modeling volatilization emissions of soil-applied pesticides under agricultural field conditions

Pesticides can volatilize from treated soil to the atmosphere causing increased environmental pollution and human exposure. Exposure assessment to airborne pesticides requires reasonable predictions of pesticide emissions. Understanding the volatilization behavior due to changes in environmental conditions can help in assessing the risk uncertainty and designing better mitigation strategies. In this study, we developed a mechanistic model that can be used to predict the hourly volatilization emissions from pesticide-treated soil at different environmental conditions. Pesticide properties and local environmental conditions drive the transport processes at the soil-air interface within the model.The numerical model simultaneously calculates the soil fluxes of heat, moisture, and pesticide at the soil-air interface with inputs of hourly meteorological data. The initial condition of pesticide concentration in soil is obtained from the applied mass during treatment. The numerical model was compared with an analytical model and with field observations for a soil injected fumigant and two surface applied pesticides.The model performance of 14 pesticides under stagnant conditions against the Jury's analytical model showed reasonable agreement with values for the coefficient of determination (R2) ranging from 0.76 to 0.99. The model was a good predictor of the field-scale volatilization of a fumigant (1,3-dichloropropene) application when compared to observations (R=20.8). Both the timing of the peak and the temporal variability of the measured volatilization of the fumigant were captured by the model when the fumigant was incorporated at a depth of 46 cm in the soil column. The model also showed reasonable agreement with the measured volatilization of two surface-treated pesticides, though site-specific meteorological data was unavailable for these observations.The results indicate that the modeling approach could be a useful tool to evaluate the impact of location-specific meteorological conditions on the field volatility of pesticides and determine the emissions for risk assessment.

Typical Pesticide Residues and Their Risk Assessment in Farmland Environment of Different Plant Types in Shaya County, Xinjiang

In order to investigate the characteristics of typical pesticide residues in farmland soil of different plant types in Shaya County and to evaluate the level of human health risk and ecological risk caused by pesticide residues, a total of 55 samples of plants, soil, and water from nine areas of Shaya county were collected on September 29, 2020. The occurrence levels of 47 typical pesticides in the samples were analyzed using gas chromatography-mass spectrometry (GC-MS). The results showed that a total of 23 pesticides were detected in three environmental media, and the maximum concentrations of pesticides in soil, plants, and water were 70.58 μg·kg-1, 1832.18 μg·kg-1, and 188.53 μg·L-1, respectively. The levels of pesticide residues in the three environmental media in Shaya county were characterized as plants>water>soil. From the detection of pesticides in different plant types, P1, P2, P6, and P8 in the center of the county were the most seriously polluted. The plants with a high pesticide load level in the corresponding areas were cotton, walnut, red jujube, and poplar, and the pesticides with a high concentration contribution were hexachlorocyclohexanes, chlorpyrifos, cyhalothrin, fluvalinate, metalaxyl, difenoconazole, and procymidone. The human health risks of adults and children caused by oral intake, skin contact, and respiratory inhalation were evaluated. The results showed that oral intake was the main exposure route, and the risk level of children was significantly higher than that of adults but was within the acceptable range. The ecological risk level of earthworms in soil was subsequently evaluated. The results showed that the potential ecological risk level of a single pesticide was low, and the potential ecological risk level of bifenthrin was the largest. The calculation of the total ecological risk of mixed pesticides showed that areas P1, P4, P7, and P9 were at moderate risk, whereas other areas were at low risk. Therefore, the use of some pesticides in Shaya County should be restricted.

Development and application of a numerical dynamic model for pesticide residues in apple orchards.

Limited understanding of the fate of pesticides in apple orchards may lead to recurring pests or pose risks to food safety. In this study, through a field experiment conducted in an apple orchard, a dynamic plant uptake model, coupled with a soil water model, was developed to simulate measured pesticide concentrations in soil and different plant compartments. Results showed that the overall model could adequately describe the data set of four pesticides in the apple orchard. An estimated 15%-24.7% of applied pesticides were deposited on leaves and 0.37%-0.58% on fruits. Decreasing pesticide concentrations in fruits were observed after pesticide application, with 9.6%-64.8% of this decrease explained by biodegradation, 29.8%-75.8% by fruit growth dilution and 11.3%-47.6% by wash-off. Furthermore, a first estimation of dietary risks indicated that ingestion of the apples may not represent an acute or chronic risk to human health. The dynamic plant uptake model, coupled with the tipping buckets soil water model, could successfully be fitted to describe to the data set for the fate of four pesticides applied in an apple orchard. The contribution of different pathways to pesticide concentration was highly influenced by precipitation, fruit growth dilution and the characteristics of different pesticides. This model can improve our understanding of pesticide fate in apple orchards and has great potential for supporting food safety assessment and decision-making to minimize impacts arising from pesticide applications. © 2022 Society of Chemical Industry.

Modeling pesticides in global surface soils: Exploring relationships between continuous and discrete emission patterns

Continuous pesticide emission at constant rate does not occur in reality, but can be a useful and simple concept in modeling studies. To explore the relationship between continuous and discrete emission patterns, we introduced a simple equivalent approach based on a comparison of simulated surface soil pesticide concentrations. The simulated results indicate that, at high soil pesticide dissipation rates and low emission frequencies, the average concentrations under the continuous and discrete emission scenarios were very similar. We demonstrated that the continuous emission model that used the simple average method to calculate the emission rate always overestimated the simulated pesticide concentrations in the surface soil compared to the discrete emission model when using a one-year period based on agricultural practices. In addition, we incorporated the equivalent approach into the USEtox model (a screening-level tool), which can approximate the average pesticide concentrations in surface soil using the time-integrated fate factors at different emission frequencies. The results indicate that the continuous-emission simulations agree with the discrete emission for at least 90% of the selected pesticides based on annual or semi-annual emission patterns. Further studies into other topics, such as random emission patterns and simulation periods, are required to improve the model. Nevertheless, the equivalent approach presented in this study can aid in transforming discrete emission patterns into continuous-emission-based models and improve surface soil pesticide management.

Historical Pesticide Purchases for a New Jersey Apple Orchard from 1931-1936 and 1943-1945 with Notes on Remnant “Legacy” Pesticide Concentrations in Soil

For more than a century (1905-1998) the Smith Farm in East Brunswick, New Jersey was well-known. At its peak it was the largest apple orchard in the state. The father and son proprietors, George and Lawrence Smith, were innovators, pioneering new and improved orchard management and apple growing techniques, and were dubbed “Apple Kings” and “Master Farmers” for their work. In 1998, the pesticide purchase records at the farm from 1931-1936 and 1943-1945 were serendipitously rescued from a dumpster. The receipts and other materials provide a historical glimpse of two time periods marked by rapid and significant changes in agricultural pesticides from largely naturally derived, to synthetic, a legacy of World War II chemical innovation. As cutting-edge orchardists, the Smith’s employed and experimented with the most up to date pest control methods of their time and their pesticide purchases reflect that. However, many of the chemicals used at the farm remain in soils for long periods after application. Soil sampling in 1998 identified extensive contamination from these “legacy” pesticides, an issue plaguing orchards across the United States. In 1999, with the oversight of the New Jersey Department of Environmental Protection, the contaminated orchard soils were remediated as part of a process to develop the property for housing. The orchard is long gone now, and in its place there is a housing development known as Apple Ridge Estates (with streets named after apple varieties). The history of the pesticide purchases at the farm may provide an important lesson about how one generation’s innovation may be seen as a subsequent generation’s curse.

Working toward sustainable agricultural intensification in the Red River Delta of Vietnam

D ense networks of rivers, canals, ditches, dikes, sluice gates, and compartmented fields have enabled the farms of the Red River Delta to produce 18% of Vietnam's rice ( Oryza sativa ) crop (figure 1), 26% of the country's vegetable crops, and 20% of capture and farmed aquaculture (Redfern et al. 2012). Agriculture in this fertile delta was transformed in the 11th and 13th century AD by large-scale hydraulic projects to protect the delta from flooding and saltwater intrusion, and provide field drainage during the wet season and crop irrigation in the dry season (Tinh 1999). The 20th century brought advancements in agricultural science globally—new crops and livestock genetics, inorganic fertilizers, mechanization, and pesticides that could double and triple food production per unit of land. It was the diesel pump combined with post-Vietnam War agricultural collectivization from 1975 to 1988 that brought the Green Revolution to the Red River Delta. Yet the very success of this agricultural revolution capable of feeding more people brought unintended harm to the waters, soil, coastal mangrove forests, and delta ecosystems that made it all possible. Intensification of fish production destroyed wetland habitats; polluted waterways; and led to eutrophication, biotic depletion, and increased disease (Nguyen 2017; Ahmed and Thompson 2019). Exponential increases in shrimp ( Penaeus monodon ) farming devastated mangrove forests that protected against coastal erosion and mitigated the impacts of sea level rise (Joffre et al. 2015; Ahmed and Thompson 2019). Pesticide concentrations in soil and sediments were found to be high and persistent in rice fields (Braun et al. 2018). The need to take the Green Revolution to the next level using innovation and technologies to create sustainable agricultural systems has …

Real-time forecasting of pesticide concentrations in soil

Forecasting pesticide residues in soils in real time is essential for agronomic purposes, to manage phytotoxic effects, and in catchments to manage surface and ground water quality. This has not been possible in the past due to both modelling and measurement constraints. Here, the analytical transient probability distribution (pdf) of pesticide concentrations is derived. The pdf results from the random ways in which rain events occur after pesticide application. First-order degradation kinetics and linear equilibrium sorption are assumed. The analytical pdfs allow understanding of the relative contributions that climate (mean storm depth and mean rainfall event frequency) and chemical (sorption and degradation) properties have on the variability of soil concentrations into the future. We demonstrated the two uncertain reaction parameters can be constrained using Bayesian methods. An approach to a Bayesian informed forecast is then presented. With the use of new rapid tests capable of providing quantitative measurements of soil concentrations in the field, real-time forecasting of future pesticide concentrations now looks possible for the first time. Such an approach offers new means to manage crops, soils and water quality, and may be extended to other classes of pesticides for ecological risk assessment purposes.

Monitoring of Pesticides Level in Agricultural Soils using Validated Method

Agricultural soil serves as a natural medium for the growth of a variety of edible crops and vegetables. Likewise, systematic assessment of agricultural soil becomes mandatory as it reflects direct linkage with the food chain and health of living beings. In the past few decades, it has been detected with the presence of various environmental contaminants being heavy metals and pesticides. The current research focuses on the investigation of different pesticides viz., organophosphorous (OPPs) and organochlorine (OCs) in agricultural soils of Amritsar (India) using gas chromatograph. All soil samples (except south zone) were found to be contaminated with one or the other pesticide. The linearity was observed over the range from 0.1 to 1.0 mg L-1 for all pesticides. The coefficient of determination (r2) was observed in the range of 0.916 to 0.999. The LODs, based on signal-to-noise (S/N) ratio of 3, ranged from 0.003 to 0.009 mg L-1. The precision of the proposed method was presented and accepted with an RSD greater than 20%. This report pertains to the presence of alarming concentrations of pesticides in soils of Amritsar (India).

Variation of United States environmental regulations on pesticide soil standard values

To specify the maximum allowable pesticide concentration in soil, pesticide residential soil regulatory guidance values (RGVs) have been promulgated by U.S. state regulatory jurisdictions to protect human health. A total of 12,451 RGVs for 456 identified pesticides adopted by 46 states were analyzed to evaluate whether there is the agreement among pesticide standard values regulated by the U.S.-related jurisdictions. Among them 62 pesticides with at least 50 RGVs were defined as the commonly regulated pesticides, and seven pesticides with at least 100 RGVs were defined as the most commonly regulated pesticides. A total of 12 states have provided over 500 pesticide soil RGVs and Texas alone has provided at least 1140 RGVs. Results indicate that these pesticide soil RGVs promulgated by the U.S. state jurisdictions for an individual pesticide could vary in a wide range of over six (DDT), seven (alpha-HCH), or even nine (Dieldrin) orders of magnitude. On the other hand, all of the seven most commonly regulated pesticides have a large RGV data cluster in which the state jurisdiction RGVs shared the U.S. Environmental Protection Agency (U.S. EPA) standards. To examine whether those pesticide soil RGVs could protect human health, cancer and non-cancer risk uncertainty bounds were calculated for the seven most commonly regulated pesticides. Results show that for the most commonly regulated pesticides, a total of 265 (41.8% of the total) soil RGVs exceeded the cancer risk uncertainty upper bounds and 30 (4.5% of the total) soil RGVs are above the non-cancer risk uncertainty bounds, which indicates that those RGVs cannot protect human health when exposing to the pesticides from soil.

Genotoxicity assessments of alluvial soil irrigated with wastewater from a pesticide manufacturing industry.

In this study, organochlorine pesticides (OCP) and heavy metals were analyzed from wastewater- and groundwater- irrigated soils (control samples) by gas chromatography (GC) and atomic absorption spectrophotometry (AAS), respectively. Gas chromatographic analysis revealed the presence of high concentration of pesticides in soil irrigated with wastewater (WWS). These concentrations were far above the maximum residue permissible limits indicating that alluvial soils have high binding capacity of OCP. AAS analyses revealed higher concentration of heavy metals in WWS as compared to groundwater (GWS). Also, the DNA repair (SOS)-defective Escherichia coli K-12 mutant assay and the bacteriophage lambda system were employed to estimate the genotoxicity of soils. Therefore, soil samples were extracted by hexane, acetonitrile, methanol, chloroform, and acetone. Both bioassays revealed that hexane-extracted soils from WWS were most genotoxic. A maximum survival of 15.2% and decline of colony-forming units (CFUs) was observed in polA mutants of DNA repair-defective E. coli K-12 strains when hexane was used as solvent. However, the damage of polA (-) mutants triggered by acetonitrile, methanol, chloroform, and acetone extracts was 80.0, 69.8, 65.0, and 60.7%, respectively. These results were also confirmed by the bacteriophage λ test system as hexane extracts of WWS exhibited a maximum decline of plaque-forming units for lexA mutants of E. coli K-12 pointing to an elevated genotoxic potential. The lowest survival was observed for lexA (12%) treated with hexane extracts while the percentage of survival was 25, 49.2, 55, and 78% with acetonitrile, methanol, chloroform, and acetone, respectively, after 6 h of treatment. Thus, our results suggest that agricultural soils irrigated with wastewater from pesticide industries have a notably high genotoxic potential.

Local organochlorine pesticide concentrations in soil put into a global perspective

In this work, agricultural and background soil concentrations of p,p′-DDT, p,p′-DDE, HCB, α-, β- and γ-HCH from 1993 to 2012 were collected from 73 peer-reviewed publications, and analysed statistically. For the period 2003–2012 and for all chemicals, the mean concentration in agricultural soil is significantly higher than the concentration in background soil. In addition to the statistical analysis, concentrations of p,p′-DDT and α-HCH in soils were calculated with a global environmental fate and transport model. A decrease in the mean soil concentration from the first decade to the second was observed with the model, but this decrease is not visible in the measured concentrations, which could result from ongoing use of p,p′-DDT and α-HCH Furthermore, modelled background soil concentrations are generally lower than measurements. This implies that background soil may have received p,p′-DDT and α-HCH through additional routes not described by the model such as spray drift.

Outcome of the Public Consultation on the draft EFSA Guidance Document for predicting environmental concentrations of active substances of plant protection products and transformation products of these active substances in soil

Outcome of the Public Consultation on the draft EFSA Guidance Document for predicting environmental concentrations of active substances of plant protection products and transformation products of these active substances in soil

Towards the ecological profiling of a pesticide contaminated soil site for remediation and management

Ecological profiling of a contaminated system is the first and foremost requirement for any kind of in situ restoration activities. Therefore, in the present study, we sought to validate simple, adequate and consistent inventorying and monitoring methods for the ecological characterization of a hexachlorocylcohexane (HCH) isomers contaminated soil site in Lucknow, North India. The abundance and diversity of plant species, microbial biomass, total organic carbon, soil dehydrogenase activity, pesticide concentration in soil and plant species as well as the occurrence of ecologically sensitive species such as earthworms, honey bees and butterflies in contaminated and non-contaminated soil sites were studied. FTIR analysis was done for assessing the variation of functional groups present in soil. Furthermore, the germination assays of selected seeds were conducted in both HCH-contaminated and non-contaminated soils. Interestingly, there was a significant difference (p≤0.01) observed for the studied variables in HCH-contaminated site in comparison to the non-contaminated soil site and they were negatively correlated with the level of HCH contamination. Twenty five plant species were reported from the control site; whereas in the case of HCH-contaminated site, it was reduced to seven species. The presence of α-, β-, γ- and δ-HCH isomers in the soil samples of contaminated sites were varied from 5.18–12.45, 30.15–68.77, 6.93–16.55 and 0.75–7.54mgkg−1, respectively, whereas the concentrations of ∑HCH in plant samples were varied from 2.78 to 12.47mgkg−1. The germination percentages of all the test plants were significantly low in contaminated soil. Most interestingly, honeybees, earthworms and butterflies were not spotted in the contaminated sites. The study indicates that proposed way of ecological characterization is appropriate for (i) knowing the extent and level of HCH isomers contamination (ii) knowing the adaptive capacity of the contaminated soil system and (iii) for adopting suitable methodical frame works for the in situ restoration of contaminated soil sites.

Spatial distribution, ecological risk evaluation and potential sources of organochlorine pesticides from soils in India

This study was conducted in an attempt to unravel the concentration level, distribution pattern and potential sources of organochlorine pesticide (OCP) residues in the soil samples from northwestern part of Hyderabad city, India. Soil samples were extracted for pesticide residues using Soxhlet extraction procedure. The sample extracts were analyzed by gas chromatograph coupled with quadruple mass spectrometry (GC–qMS). The results reveal that the δ-HCH, p,p′-DDE, endrin ketone and endosulfan sulfate were most frequently detected, while Heptachlor epoxide and p,p′-DDD were least identified pesticides. The total concentrations of organochlorine pesticides in soils vary from 129 to 1,001 μg kg−1—dry weight. The ratio of (DDD + DDE)/DDT in the soils range from 0.74 to 7.81 which indicates the usage of DDT in the recent past. However, the ratio of DDD/DDE in the soils is <1, which implies that the primary source of p,p′′-DDE was probably from DDT. The average ratios of α-/γ-HCH are lower than 1, which suggest that the lindane has been used recently in the soils of the study area. Also, the total organic carbon shows significant positive correlation with the total concentration of OCPs. This study provides a first time systematic baseline data on OCPs in the soils that could be useful to evaluate the impact on the groundwater as well as risk assessment on human health.

Determination of polar pesticides in soil by micellar electrokinetic chromatography using QuEChERS sample preparation

The optimal conditions for the separation of pesticides of the following classes: phenoxy carboxylic acids, sim-triazines, triazinones, chloroacetamides, urea derivatives, neonicotinoids, carbamates, triazoles, imidazoles, benzimidazoles, and phosphorus organic compounds by micellar electrokinetic chromatography have been selected. A method for determining 27 polar pesticides in soil using QuEChERS sample preparation has been developed. The recovery of pesticides was from 31 to 104%. The lower limits of the found pesticide concentrations in soil taking into account preconcentration were 0.01–0.4 mg/kg. The relative standard deviation of the results of analysis does not exceed 10%.

Obsolete pesticides and application of colonizing plant species for remediation of contaminated soil in Kazakhstan

In Kazakhstan, there is a problem of finding ways to clean local sites contaminated with pesticides. In particular, such sites are the deserted and destroyed storehouses where these pesticides were stored; existing storehouses do not fulfill sanitary standards. Phytoremediation is one potential method for reducing risk from these pesticides. Genetic heterogeneity of populations of wild and weedy species growing on pesticide-contaminated soil provides a source of plant species tolerant to these conditions. These plant species may be useful for phytoremediation applications. In 2008-2009 and 2011, we surveyed substances stored in 80 former pesticide storehouses in Kazakhstan (Almaty oblast) to demonstrate an inventory process needed to understand the obsolete pesticide problem throughout the country, and observed a total of 354.7t of obsolete pesticides. At the sites, we have found organochlorine pesticides residues in soil including metabolites of dichlorodiphenyltrichloroethane and isomers of hexachlorocyclohexane. Twenty-four of the storehouse sites showed pesticides concentrations in soil higher than maximum allowable concentration which is equal to 100μgkg(-1) in Kazakhstan. Seventeen pesticide-tolerant wild plant species were selected from colonizing plants that grew into/near the former storehouse's pesticides. The results have shown that colonizing plant annual and biannual species growing on soils polluted by pesticides possess ability to accumulate organochlorine pesticide residues and reduce pesticide concentrations in soil. Organochlorine pesticides taken up by the plants are distributed unevenly in different plant tissues. The main organ of organochlorine pesticide accumulation is the root system. The accumulation rate of organochlorine pesticides was found to be a specific characteristic of plant species and dependent on the degree of soil contamination. This information can be used for technology development of phytoremediation of pesticide-contaminated soils.

EXPOSURE ASSESSMENT AND HEALTH EFFECTS ASSOCIATED TO PESTICIDES BURIED NEAR AN URBAN COMMUNITY IN COLOMBIA

Background/aims: Organophosphate and organochlorine pesticides have been associated with neurological and respiratory effects in agricultural communities, but few studies have been conducted in buried pesticides deposited close to human settlements. An urban neighborhood and a school with &gt;1,500 children was settled in a former agricultural area of 44ha in Cartagena-Colombia. During construction, several containers with pesticides were found. Contaminated soils and containers were removed and confined to an area close by. Our objective was to evaluate exposure to and potential health effects of these buried pesticides on surrounding communities. Methods: Concentrations of pesticides in soil and air were determined. A health risk assessment was done modeling soil concentrations found at the pesticides confined area. Respiratory diseases data was obtained, and tests for pulmonary and neurological function were applied in children(n=389) and adults(n=440) at the exposed and a control area. Levels of pesticides in serum and their metabolites in urine were determined in a subsample of children. Results: Presence of DDT isomers and metabolites were found in one soil sample and chlorpyrifos was reported in one air sample. Risk modeling suggests risk inside the confined area by different routes of exposure. Although individuals at the exposed area reported more frequently severe dyspnea(children OR:2.97; IC95%:1.0-8.97) and wheezing (adults OR:2.10; IC95%:1.13-3.90) evidence of lung function effects was not demonstrated by spirometry. There were not differences in intellectual performance. Pesticides in blood serum were mostly below detection limits, and only significant levels of pp-DDE were found, although at concentrations similar to non-exposed populations. Conclusions: A confined area with buried pesticides but not direct contact with population is a potential source of risk. However, no evidence of exposure to pesticides was found in this area. Increased reports of respiratory symptoms could be explained by increased risk perception or other environmental exposures in the area.

Sorption of hydrophobic pesticides on a Mediterranean soil affected by wastewater, dissolved organic matter and salts

Irrigation with treated wastewaters as an alternative in countries with severe water shortage may influence the sorption of pesticides and their environmental effects, as wastewater contains higher concentrations of suspended and dissolved organic matter and inorganic compounds than freshwater. We have examined the sorption behaviour of three highly hydrophobic pesticides (the herbicide pendimethalin and the insecticides α-cypermethrin and deltamethrin) on a Mediterranean agricultural soil using the batch equilibration method. We considered wastewater, extracts from urban sewage sludge with different dissolved organic carbon contents, and inorganic salt solutions, using Milli Q water as a control. All pesticides were strongly retained by soil although some sorption occurred on the walls of the laboratory containers, especially when wastewater and inorganic salt solutions were used. The calculation of distribution constants by measuring pesticide concentrations in soil and solution indicated that pendimethalin sorption was not affected whereas α-cypermethrin and deltamethrin retention were significantly enhanced (ca. 5 and 2 times, respectively) when wastewater or salt solutions were employed. We therefore conclude that the increased sorption of the two pesticides caused by wastewater cannot be only the result of its dissolved organic carbon content, but also of the simultaneous presence of inorganic salts in the solution.

Multipesticide Residue Assessment of Agricultural Soil and Water in Major Farming Areas in Benguet, Philippines

This study investigated the concentration and presence of pesticide residues in water and soil in Benguet, which is a vegetable producing region in the Philippines. Seventy-eight samples and 49 water samples were taken from different farms covering three municipalities in the province of Benguet and were analyzed using gas chromatography. Meteorological conditions of temperature and humidity were also taken. Thirty-four of the soil samples were found to be positive for pesticide residues. The most significant pesticide type with the highest concentration was technical endosulfan, with a mean concentration of 0.025 mg/kg, followed by endosulfan sulfate (0.015 mg/kg), chlorpyrifos (0.01 mg/kg), profenofos (0.003 mg/kg), chlorothanil, cypermethrin, and cylohathrin (all at 0.002 mg/kg). One water sample was found to be positive for pesticide residue of chlorpyrifos in municipality 2 at a concentration of 0.07 mg/L. The data also showed that endosulfan, which is restricted in the Philippines and banned in other countries, was found to be the most prevalent pesticide used (17.7%) and the second highest in concentration (0.015 mg/kg) in soil samples. The study also showed a relationship between temperature and pesticide concentration in soil. In conclusion, pesticide residues were found in soil and water samples in the farming areas of Benguet.