Residual deposition of pesticides in agricultural soils: a case study from the adjoining area of Chandigarh, India

Pesticide contamination of agricultural soils has emerged as a global environmental concern due to its potential impact on soil quality, food safety, and ecosystem health. Despite increasing pesticide use worldwide, information on the occurrence and distribution of residual pesticides in agricultural soils remains limited in many regions. This study aimed to determine the occurrence and concentration of selected pesticide residues (aldrin, malathion, chlorpyrifos, phorate, and λ-cyhalothrin) in agricultural soils using gas chromatography-mass spectrometry (GC-MS). The present study was conducted to identify pesticide residues in nearby agricultural soils of Chandigarh, India. In the present study, environmental monitoring of 105 commonly sprayed pesticides was conducted on soil samples collected from seven villages of Chandigarh, India. A total of 105 samples were analysed for pesticide residues, and the measured concentrations were compared with the Maximum Residue Limits (MRLs) set by the Food Safety and Standards Authority of India (FSSAI) and European regulations. From the total soil samples collected from agricultural fields in different sites, 54 samples were found contaminated with aldrin, chlorpyrifos, λ-cyhalothrin, hexachlorocyclohexane, malathion, and phorate. Of the 54 samples, 34 were found to exceed the MRLs. The findings provide baseline data on pesticide contamination, contribute to regional residue monitoring efforts, and support evidence-based strategies for sustainable pesticide management and environmental protection. Also, the present study can provide policymakers, authorities, farmers, and consumers with valuable insights and awareness.

Pesticides are indispensable for modern agriculture; however, their indiscriminate and repeated use has resulted in the accumulation of residues in agricultural soils worldwide. Soil acts as both a sink and a secondary source of pesticide contamination, allowing persistent compounds to remain in the environment for years and potentially transfer to crops, groundwater, and surrounding ecosystems. A global assessment estimated that approximately 64% of the world’s agricultural land is at risk of pesticide pollution, with nearly 31% classified as high risks, particularly in regions characterised by intensive agriculture, high biodiversity, and water scarcity (1, 2). The agricultural sector is essential to human survival, yet the growing global population is affecting food supplies. Chemicals are commonly used in agriculture to manage pests and unwanted plants, thereby increasing food production. While they are crucial for crop protection in agriculture, their use has negative impacts on human and environmental health. Pesticides reduce pests that damage crops, animals, and agricultural production. Chemical pesticides may cause harm to unintended species due to their lack of selectivity and long-term persistence in the environment. These may contaminate the environment, including soil, by leaching, flow, percolation, and pulverisation, affecting both organisms and the entire ecosystem. Pesticide contamination is now a major concern worldwide. News related to pesticide contamination is frequently published in newspapers, magazines, and scientific journals.

Although pesticides are essential for reducing losses caused by weeds, diseases, and pests, growing concerns about their detrimental impacts on human and environmental health demand a rigorous analysis of their usage patterns. Even though India uses 0.4 kg of pesticides per acre, which is less than China’s 1.83 kg, concerns with pesticide residue contamination in the food chain need immediate attention. Significant geographical differences in pesticide use further emphasise the need for more consistent and environmentally friendly farming methods (3). Rapid population growth and a strong emphasis on achieving food-grain self-sufficiency have forced Indian farmers to rely heavily on pesticides. Due to their low cost and broad-spectrum toxicity, Dichloro-Diphenyl-Trichloroethane (DDTs)are useful in controlling pests and infections (4, 5). However, some characteristics, such as persistency, volatility, and atmospheric distribution through long-range transportation (6), have resulted in the contamination of air, water, soil, and food (7–10). Organic pesticide residues have been found in large quantities in Indian soil (11–19), water (20–25), and crops (26–28). The fate of organochlorine pesticides (OCPs) in soils has also been widely examined in the context of land use and cropping patterns. The levels of these contaminants found in several agricultural soil samples were quite high (11–13, 15, 29, 30).

Nowadays, everything from food to groundwater and drinking water is heavily contaminated with OCPs; therefore, knowing the environmental fate of OCP residues is critical. Although OCPs have been used in India for over 30 years, there is relatively little information on their presence in air, soil, and water systems. Pesticides can be classified according to a variety of parameters, including their target pest, chemical composition, soil persistence (half-life), the spectrum of action, mechanism of entrance into the target pest, mode of formulation, the toxicity of the active molecule, and volatilisation behavior (31, 32). Today, the Indian pesticide industry comprises more than 125 large- and medium-scale basic producers and over 500 pesticide formulation units. Pesticide formulations produced in the country are mainly of conventional types, with dusting powders accounting for 85% of the market, followed by water-soluble dispersible powders (12%) and emulsifiable concentrates (2%) (33). Granular formulations, which offer advantages such as lower drift, ease of application, and enhanced safety, are still in their infancy in India. Most pesticide-producing units belong to the small-scale industry (SSI) sector (34–36). India has 293 registered pesticides, yet 104 of these are banned or restricted in one or more countries globally (37). India ranks 12th globally in pesticide use, yet, according to 2017 data, its per capita pesticide use remains low compared to other nations (38).

In India, insecticides account for the largest share of pesticide consumption, followed by herbicides and fungicides (Figure 1). However, in global pesticide use patterns, herbicides hold the largest share, followed by fungicides & bactericides, rodenticides, and insecticides. India is the fourth-largest producer of insecticides and pesticides worldwide (39). Among all pesticides, chlorpyrifos is the most commonly used in India, with its usage increasing over the years. The primary classes of insecticides used in India are organized in the following order: Organophosphates, Neonicotinoids, and Pyrethroids (39).

Pesticide consumption intensity is highest in Punjab, Haryana, and Uttar Pradesh, the key agricultural states of India. However, these states are experiencing negative growth in pesticide use, possibly due to increased awareness and adoption of sustainable agricultural practices. Between 2021–22 and 2022-23, the area under cultivation in India increased by 5.63%, while pesticide usage grew by 11.25%, indicating a disproportionate rise in pesticide dependence (40) (Figure 2).

There is limited information on the simultaneous occurrence of OCPs [aldrin, hexachlorocyclohexane (HCH)], organophosphorus(OPP) (chlorpyrifos, malathion, phorate), and pyrenoids (λ-cyhalothrin) pesticides in agricultural soils and how their persistence is influenced by soil properties such as pH, organic carbon, and texture. Additionally, data linking residue levels with ecological risk in intensively cultivated areas remains scarce, highlighting the need for integrated monitoring and risk assessment.

The key objective of this study is 1) To determine the occurrence and concentrations of selected pesticide residues (aldrin, HCH, malathion, chlorpyrifos, phorate, and λ-cyhalothrin) in the agricultural soils using GC-MS. 2) To evaluate the distribution and frequency of pesticide residues in agricultural soils from the study area. 3) To identify the predominant pesticide residues and assess their persistence in agricultural soils. 4) To generate baseline data on pesticide contamination for future environmental monitoring and management.

This study provides a comprehensive GC-MS-based assessment of residual deposition of multiple pesticide classes (OCPs, OPPs, and phenylpyrazoles) in agricultural soils. Integrating residue analysis with soil physicochemical properties improves understanding of pesticide persistence and distribution under local agricultural conditions. The study also establishes baseline data for the study region, contributing to future environmental monitoring and sustainable pesticide management. The study provides essential baseline data on pesticide residues in agricultural soils, supporting environmental monitoring, informed pesticide management, and sustainable agricultural practices. Also, provides current information on pesticide contamination in agricultural soils.

Study sites

To conduct a reconnaissance survey of farmers’ perceptions of pesticide use and to collect soil samples for analysis, seven villages in the suburban area of Chandigarh were selected and are listed in Table 1 (Figure 3). In these villages, major crops are grown, such as paddy, wheat, vegetables, fruits, etc.

Pesticides analysis

Collection and sample preparation

Samples of soil (105) were collected from agricultural land in the seven villages of Chandigarh from 2022-23. The quantity of samples collected was 300–500 grams. Soil samples were collected at the 0–15 cm depth, and results were consistent across all seven villages. A composite of multiple sub-samples from a field formed a soil sample. The sample collection was performed in clean, transparent, airtight polyethene bags to prevent cross-contamination. The collected samples were taken to the Soil Ecosystem and Restoration Ecology Lab, Department of Botany, Panjab University, Chandigarh. Each sample was mixed properly and homogenised. All samples were kept in a dry, cool place until extraction and sample preparation (41).

Chemicals and reagents

Pesticide standards were obtained from Sigma-Aldrich, with certified purities and uncertainty values listed on each. The pesticide data, including classification, GC-MS/MS technical data, were used as reported in Wood (42) and the Pesticide Properties Database A to Z (43). Organic solvents, including acetonitrile, n-hexane, acetone, methanol, and dichloromethane, were purchased from Fisher Scientific (HPLC-grade). Anhydrous magnesium sulphate (MgSO 4) and sodium sulphate (Na 2 SO 4) were purchased from Merck Life Science, India. Sodium chloride (NaCl), primary secondary amine (PSA), C18, and graphite carbon black (GCB) were purchased from Agilent Technologies (USA).

Preparation of soil samples

Soil samples were mixed to ensure consistency, with each sample weighing 20 g, and placed in a 250-ml round-bottom flask. To facilitate extraction, 50 ml of methanol (CH 3 OH) was added, and the flasks were shaken for one hour at 160 rpm (revolutions per minute) to enhance the interaction between the soil and methanol. After shaking, the flasks were left to rest for 30 minutes to allow the soil to settle, ensuring only the clear supernatant was used. Then, 20 ml of the supernatant was pipetted and filtered through Na 2 SO 4 to remove moisture and impurities. The Na 2 SO 4 bed was rinsed with 10 ml of methanol to maximise yield, and this rinse was combined with the filtered supernatant. The collected solution was evaporated under a vacuum at 500 mm Hg and 50 °C to gently remove methanol without degrading the compounds. Finally, the sample was reconstituted with 1 mL of n-hexane, preparing it for GC-MS analysis. Extraction, purification of extracts, and analysis were performed according to the USEPA-3540C soil analysis method (44, 45).

Analysis of pesticide residues

Pesticide determination in extracted samples was performed using GC-MS. GC Model 7890A (Agilent Technologies) with mass (5975C inert XL EI/CI MSD) triple axis detector was used for pesticide residue analysis.

Column specification and operating conditions of gas chromatography

From the 1 ml sample extract, 1 μl was injected into the GC-MS to verify the presence of pesticide residues under the following conditions: 1 μl at 300˚C. Quantitative analysis was conducted using a GC-ECD under conditions specified by the EPA. Various concentrations of standards were also injected. After processing the samples through multiple extraction steps, the final, concentrated, and cleaned sample was analyzed using a gas chromatograph with an electron capture detector, which is specific and highly sensitive to halogenated compounds. One μl of each extract was injected into the injection port using a microsyringe. Pesticide analysis was performed using a capillary gas chromatography system (Agilent 173 Technologies) 7890 with an electron capture detector (GC-ECD). The analytical column was a 30 m HP5-MS fused silica capillary column (30 × 0.25 mm × 0.25 μm film thickness). The temperature program for pesticide analysis started at 60 °C, then increased to 180 °C at 30 °C per minute, then to 280 °C at 10 °C per minute, and held for 10 minutes. In the electron capture detector, the radiation source was Ni63, the detector temperature was 350 °C, and the carrier gas was hydrogen, with nitrogen (99.99%) as the make-up gas (46).

Pesticide contamination and its retention in soil

For the present study, we analyzed soil samples for six pesticides: aldrin, chlorpyrifos, λ-cyhalothrin, hexachlorocyclohexane, malathion, and phorate. From the total soil samples collected from agricultural fields in different sites, 54 samples were found contaminated with aldrin, chlorpyrifos, λ-cyhalothrin, hexachlorocyclohexane, malathion, and phorate. 34 of 54 samples were found to be above the MRLs. All soil samples collected from V1, V2, V7, V5, and V4 were found to contain various pesticide residues (Figures 4, 5). Further, soil samples from V3 and V6 were the least contaminated. Maximum positive samples of V1, V7, V2, and V5 were above MRL values. Frequencies and pesticide concentration ranges found in the tested soil samples are shown in Table 2. Of the positive samples, 10 were contaminated with phorate, with concentrations ranging from 0.03 to 0.33 mg/kg, and 6 exceeded the MRL (0.05 mg/kg). Fifteen samples were contaminated with malathion at concentrations ranging from 0.02 to 10.89 mg/kg, and seven exceeded the MRL (0.05 mg/kg). As many as fifteen samples were found to be contaminated with chlorpyrifos at concentrations ranging from 0.08 to 6.42 mg/kg, and all samples exceeded the MRL (0.03 mg/kg). Seven soil samples were contaminated with HCH at concentrations ranging from 0.01 to 0.04 mg/kg. Furthermore, three samples were found to be contaminated with aldrin at concentrations ranging from 0.01 to 0.03 mg/kg. Three samples were found to be contaminated with λ-cyhalothrin, with concentrations ranging from 0.01 to 0.08 mg/kg, and all exceeded the MRL (0.01 mg/kg).

Among these 54 positive soil samples, phorate was present in 10 samples, malathion in 15, chlorpyrifos in 15, HCH in 6, λ-cyhalothrin in 5, and aldrin in 3 soil samples with detection percentages of 9.52, 13.33, 5.71, 2.85, and 4.76, respectively. Samples found contaminated with chlorpyrifos and λ-cyhalothrin were above MRL. In contrast, samples contaminated with phorate, malathion, and HCH were found above MRL, except for four, seven, and three samples for phorate, malathion, and HCH, respectively, as per values of the Environmental Protection Agency [(8081(OC& Pyrethroids); 8141(OP&ON) soil] for soil samples. The maximum number of detected pesticide residues was recorded in V1, V2, and V7. A minimum number of pesticides were observed in V3 (Table 3).

Pesticides used in agriculture are primarily stored in the soil. Pesticides and their metabolites leave persistent residues in soil, even though only about 10% of the applied amount reaches the target organisms. Pesticides, including fumigants, herbicides, insecticides, and nematicides, are applied directly to the soil to manage plant diseases and pests. However, once a pesticide molecule enters the soil, its fate in the ecosystem is primarily determined by soil characteristics, pesticide properties, and prevailing weather conditions. All soil samples collected from V1, V2, V7, V5, and V4 were found to contain various pesticide residues. At the V1, V2, and V7 sites, all six pesticide residues were detected. Results showed that chlorpyrifos was the most abundant pesticide present in soil samples. Maximum concentrations of chlorpyrifos were found in V1 at 6.42 mg/kg, and the minimum concentration of chlorpyrifos was reported in V4 at 0.31 mg/kg. All chlorpyrifos samples were above the MRL (0.03 mg/kg). The range of chlorpyrifos observed in the agricultural soil of Chandigarh was 0.08 to 6.42 mg/kg. The chlorpyrifos concentrations in this study were significantly lower than those reported by Mishra et al. (45) for pesticide residues in farmland soil from different districts of Haryana, ranging from 0.10 to 7.42 mg/kg and higher than those reported by Pahal et al. (47) for pesticide residue in the soil of Fatehgarh Sahib, Punjab, i.e., 0.0065 mg/kg. Kumar et al. (48) also reported a chlorpyrifos concentration of 8.67 μg/kg in agricultural soil in Delhi. Also, Arora et al. (49) reported chlorpyrifos in agricultural soils from Sonipat and Kaithal (averages of 3 μg/kg and 1 μg/kg, respectively). They also reported this pesticide in the soil of Dehradun, specifically in Modipuram, with concentrations ranging from 2 to 5 μg/kg. Mishra et al. (19) also reported chlorpyrifos contamination (0.018–0.058 mg/kg and 0.002-0.014 mg/kg) in the soil of Karnal and Rohtak, Haryana, respectively.

The highest concentration of malathion was recorded in V1 at 10.89 mg/kg, and the lowest was observed in V6 at 0.02 mg/kg, which was below the MRL (0.05 mg/kg). A total of 14 positive samples for malathion contamination were recorded, of which only 50% exceeded the MRL. Pesticide λ-cyhalothrin was reported from V1, V2, and V7. The minimum concentration was recorded at V7 (0.01 mg/kg), and the maximum at V1 (0.06 mg/kg). The pesticide concentration recorded in the present study was lower than reported by Mishra et al. (45). Mishra et al. (19) also reported λ-cyhalothrin (0.016 mg/kg and 0.0044-0.0283 mg/kg) contamination in the soil of Karnal and Rohtak, respectively. However, all observed concentrations of this pesticide at the selected study sites exceeded the MRL (0.01 mg/kg). A total of 10 samples were reported as positive for phorate; however, only 6 exceeded the MRL (0.05 mg/kg). The highest concentration of phorate contamination was observed in V1 at 0.33 mg/kg, followed by V7 at 0.28 mg/kg. Mishra et al. (45) reported 20 positive samples from different districts of Haryana, all of which exceeded the MRL. He observed that 90 samples were contaminated, of which 57 contained multiple residues. Among these 90 positive soil samples, phorate was present in 5 samples, malathion in 20, chlorpyrifos in 44, pendimethalin in 11, butachlor in 25, endosulphan-I in 12, DDT isomer in 47, λ-cyhalothrin in 3, fipronil in 1, atrazine in 6, retilachlor in 62, propiconazole in 2, triazophos in 1 soil sample with detection percentage of 5.49, 21.98, 48.35, 12.08, 27.47, 13.19, 51.65, 3.30, 1.09, 6.59, 68.13, 2.20, 1.09, respectively. Samples found contaminated with phorate, malathion, endosulfan, and λ-cyhalothrin were above MRL. In contrast, samples contaminated with chlorpyrifos, DDT, and atrazine were found above the MRL, except for one sample each for chlorpyrifos and DDT, and three samples for atrazine, as per the Environmental Protection Agency’s soil sampling values.

The HCH contamination range observed at the selected study site was 0.01-0.04 mg/kg. Only 4 positive samples exceeded the MRL (0.01 mg/kg). HCH contamination was recorded in V1, V2, V4, V5, and V7. The highest and lowest concentrations were observed in V7 and V4, at 0.04 mg/kg and 0.01 mg/kg, respectively. The lowest recorded contamination was found for aldrin; only 5 soil samples showed aldrin contamination, ranging from 0.01 to 0.03 mg/kg. The highest concentration was recorded from V1 and V2 at 0.03 mg/kg. Khuman et al. (50) reported the presence of HCH and Aldrin in surface soil samples from the agricultural, coastal, and backwater transects along the southwest coast of India. They observed that organochlorine pesticide concentrations in soil were in the order agricultural > coastal > backwaters transect. The ranges of HCH and aldrin were recorded as ND-123 ng/g and ND-108 ng/g, respectively. The presence and distribution of a few organochlorine pesticides in the paddy fields of the Kuttanad agroecosystem were examined by Shruti et al. (51). She reported the presence of aldrin in soil at a range of 1.93-2.73 ng/g. Similarly, Jacob & Resmi (52) conducted a field study in the cardamom plantations of Idukki district, South India, to estimate and predict the persistence of pesticide residues in the soil environment. They observed that residues of endosulfan, DDT, and organophosphorus pesticides were present in soil samples at 31.6%, 29%, and 21%, respectively. They reported contamination with chlorpyrifos and quinalphos in a cardamom plantation, ranging from 0.01 to 0.589 mg/kg. The estimation of pesticide residues in the soil of Jalgaon district, Maharashtra, was reported by Baride et al. (53). They recorded Aldrin contamination in the soil, with an average concentration of 0.03 ppb. Mahdavian & Somashekar (54) reported HCH in agricultural soil from Chamarajanagar district, Karnataka, India, with an average concentration of 19.8 μg/kg.

From the present study, we concluded that farmers in the study areas had good knowledge about the safe use of pesticides; however, they did not regularly use protective clothing during pesticide application. This may increase the risk of pesticide exposure among the farmers. Given these issues, there is an urgent need for careful surveillance of soil contamination with pesticides in the V1, V2, and V7 villages. Furthermore, the growing reliance on agrochemicals, such as pesticides and fertilisers, to increase crop production heightens the risk to various environmental components. Regular monitoring and analysis are required to ensure that pesticide levels in soil and other components do not exceed permissible limits, therefore safeguarding public health and preventing pesticide bioaccumulation in the food chain.

Monitoring and management

The increased use of pesticides for pest and weed control in V1, V2, and V7 led to soil contamination in these areas. Regular monitoring, stricter enforcement of contamination limits, and exploration of alternative pest and weed management methods are crucial to reducing pesticide exposure and ensuring environmental safety. Pesticide contamination in the study area underscores the pressing need for systematic monitoring and for stricter enforcement of pesticide-use regulations. Regular training programs on safe pesticide use should be held in the suburban areas of Chandigarh to educate farmers and protect them from the self-reported toxic effects of pesticides.

Overall, the soil’s physicochemical characteristics indicate a need for improved soil management practices in Chandigarh to support sustainable agricultural productivity and environmental health. Routine soil testing, combined with the adoption of conservation practices, is essential for maintaining long-term soil quality and ecosystem health. Thus, biopesticides are emerging as a crucial component of sustainable pest management in India; however, their adoption remains limited despite policy support and growing consumer demand for residue-free produce (55). Biopesticides have also been the subject of attention in current policy and scientific discussions because of their significant compatibility with green chemistry, One Health programs, the Sustainable Development Goals, and sustainable agriculture (56).

The evaluation of pesticide concentrations in soil samples from the agricultural area of Chandigarh, UT, reveals varying levels of contamination, with chlorpyrifos, malathion, phorate, HCH, aldrin, and λ-cyhalothrin exceeding permissible limits in some samples. All chlorpyrifos samples are above the MRL. λ-Cyhalothrin is an insecticide used for household pest control and in agricultural fields. A total of five samples were reported as positive for pesticides. Of the five pesticide-positive samples, three exceeded acceptable limits, indicating unsafe use. This suggests that pesticides have detrimental effects on beneficial soil microbiota, particularly at high exposure levels. Among the seven villages, V1 has the highest level of soil pesticide contamination. All six pesticides were detected in the soil samples from V1, V2, and V7. A minimum number of contaminated samples were found in the soil of V3. Only three pesticides were observed in V3, i.e., Chlorpyrifos, Malathion, and Phorate.

Among the study areas, V1 and V7 consistently exhibited the highest contamination levels, highlighting the influence of prolonged pesticide use. These findings emphasise the urgent need for effective integrated pest management, targeted interventions, and regular monitoring to balance agricultural benefits with environmental and public health safety. These insights underscore the importance of sustainable pest management and policies that promote safe and productive agricultural practices.

To augment agricultural productivity and profitability for farmers, it is imperative to optimise the application of sanctioned pesticides while encouraging the utilisation of bio-pesticides. The application of pesticides differs markedly among various crops and geographical areas. Also, the Ministry of Agriculture regulates the production, distribution, importation, exportation, and use of pesticides in India in accordance with the Insecticides Act of 1968 and the Insecticides Rules of 1971. All insecticides, encompassing fungicides and herbicides, included in the Schedule must get registration from the Central Insecticides Board & Registration Committee (CIB&RC). Central and state governments possess the right to ban the sale, distribution, or use of pesticides in certain areas and for specified durations by notifications in the official gazette. The regulation also requires the reporting of insecticide-related poisonings, which may result in sales restrictions if considered essential for public safety. This legislation enforces fines for the sale of misbranded pesticides or violations of licensing regulations. The processes for registration and licensing are standardised; the process for banning or forbidding pesticides is distinct.

Implicating remarks and future recommendations:

Implementing integrated pest management techniques to reduce pesticide contamination.

Farmers should be educated about the potential hazards of using harmful or persistent pesticides. Awareness activities should be created to educate agricultural workers about alternative plant protection strategies. The administration and government should make such facilities easily accessible to interested farmers.

Establishing regular monitoring systems to ensure compliance with permissible contamination limits in soil, water, and food items.

Promoting organic farming practices and minimising the reliance on chemical fertilisers and pesticides. Integrated Pest Management (IPM) plans should be followed by society and agricultural workers to reduce pesticide levels in the environment.

Employing soil amendment techniques, such as biochar application or phytoremediation, to reduce pesticide contamination in soils.

Regular monitoring and assessment of soil health to track changes in contamination levels over time.

Implementing dietary guidelines and promoting alternative food sources in communities at high risk.

Strict action against sellers of banned or spurious pesticides. Stringent laws should be enacted and implemented efficiently.

Using advanced analytical techniques to more accurately identify contamination sources and pathways, thereby mitigating health risks and safeguarding public health in the study regions.

Conducting long-term studies to evaluate the cumulative effects of pesticide exposure on ecological and human health, particularly soil components. If soil ecosystems are pesticide-free, then they cannot establish the triangular relationships between humans, the environment, and ecosystems that lead to pesticide contamination.