GB Standard Testing for Pesticide Residues in Soil: Methods, Standards, and Applications

Soil pesticide residue testing to Chinese national standards (GB) is the core technical basis for evaluating farmland safety, classifying contaminated land, and demonstrating regulatory compliance under China's Soil Pollution Prevention and Control Law. Using validated standards such as GB 15618-2018, GB 36600-2018, and the corresponding HJ analytical methods, accredited third-party laboratories quantify organochlorine, organophosphorus, and current-use pesticide residues in soil at trace levels. This article explains the applicable national standards, sample types, testing items, analytical methods, quality control requirements, and typical applications of GB-based soil pesticide residue testing.

Technical Overview

Soil pesticide residue testing to Chinese national standards (GB, abbreviated from "Guobiao") is the primary technical basis for evaluating soil environmental quality, classifying contaminated farmland, and supporting land-use decisions in China. The regulatory framework is driven by the Soil Pollution Prevention and Control Law, effective January 1, 2019, and the Action Plan for Soil Pollution Prevention issued by the State Council in 2016, which mandate risk screening, detailed investigation, and remediation verification for both agricultural land and development land.

Two risk control standards define the evaluation criteria. GB 15618-2018 establishes risk screening values and risk control values for agricultural land, covering, among other parameters, total hexachlorocyclohexane (HCH/BHC), total DDT, and benzo(a)pyrene. GB 36600-2018 establishes risk screening values and intervention values for development land across 85 parameters, including a wide range of legacy organochlorine pesticides such as aldrin, dieldrin, endrin, heptachlor, chlordane, mirex, and toxaphene. Results below the screening values generally indicate acceptable human health risk, while exceedances trigger detailed investigation and, where necessary, risk management or remediation measures.

• GB 15618-2018 — Soil environmental quality: risk control standard for soil contamination of agricultural land
• GB 36600-2018 — Soil environmental quality: risk control standard for soil contamination of development land
• HJ/T 166-2004 — Technical specification for soil environmental monitoring (sampling design, frequency, and QA requirements)
• GB/T 14550-2003 — Soil quality: determination of BHC and DDT by gas chromatography
• HJ 835-2017 — Soil and sediment: determination of organochlorine pesticides by GC-MS
• HJ 921-2017 — Soil and sediment: determination of organochlorine pesticides by gas chromatography
• HJ 1023-2019 — Soil and sediment: determination of triazine herbicides by high performance liquid chromatography

Accredited third-party laboratories performing this testing typically hold CMA (China Metrology Accreditation) and CNAS accreditation to ISO/IEC 17025, which ensures that the reported data are legally valid for regulatory submissions, land transactions, and remediation acceptance.

Testing Samples

Farmland Soil

Surface soil from paddy fields, dryland, and vegetable production bases is the most common matrix. Sampling is usually performed on a grid basis at the plow layer depth of 0–20 cm, following the layout requirements of HJ/T 166-2004 and the farmland monitoring specification NY/T 395-2012, with composite samples used to characterize each grid unit.

Orchard, Tea Plantation, and Greenhouse Soil

Soils from orchards, tea gardens, and protected greenhouse cultivation are frequently tested because of intensive and repeated pesticide application. These matrices often show accumulated residues of persistent insecticides and fungicides, and results support safe-utilization zoning of production bases.

Development Land and Former Industrial Sites

Soil from former pesticide manufacturing plants, formulating facilities, chemical works, and storage areas is tested against GB 36600-2018 during detailed site investigations. Sampling typically extends to greater depths (for example 0–0.5 m, 0.5–1.5 m, and deeper intervals) to delineate vertical contamination profiles before redevelopment.

Sediment and Related Matrices

Most HJ method standards are jointly validated for soil and sediment, allowing the same analytical procedures to support river, lake, and pond sediment investigations in drainage areas affected by agricultural runoff.

In general, 500 g to 1 kg of soil is collected per sample into solvent-rinsed amber glass jars with PTFE-lined caps, transported cold and dark at approximately 4 °C, and extracted as soon as possible within the holding time specified by the applicable method.

Testing Items

Testing items are selected according to the land-use scenario, the governing risk control standard, and the suspected pesticide use history. Typical target groups include the following:

• Organochlorine pesticides (OCPs): HCH isomers (alpha-, beta-, gamma-, delta-BHC), DDT and its metabolites (p,p'-DDE, p,p'-DDD, o,p'-DDT, p,p'-DDT), aldrin, dieldrin, endrin, heptachlor and heptachlor epoxide, chlordane, endosulfan, methoxychlor, and hexachlorobenzene
• Organophosphorus pesticides (OPPs): chlorpyrifos, parathion, methyl parathion, phorate, malathion, dimethoate, dichlorvos, and related compounds
• Triazine herbicides: atrazine, simazine, cyanazine, propazine, ametryn, and prometryn
• Pyrethroid insecticides: bifenthrin, permethrin, cypermethrin, fenvalerate, deltamethrin, and lambda-cyhalothrin
• Amide herbicides and other current-use pesticides: acetochlor, butachlor, metolachlor, phenylurea herbicides, and carbamates
• Multi-residue screening packages covering 100 or more pesticides by GC-MS/MS and LC-MS/MS for comprehensive site investigations

For agricultural land assessment against GB 15618-2018, the key indicators are typically total HCH and total DDT; for development land assessment against GB 36600-2018, the full list of organochlorine pesticide screening and intervention parameters is evaluated. Custom target lists can also be established based on historical pesticide production or application records.

Testing Methods

GB-based soil pesticide residue analysis follows a validated workflow of sample preparation, extraction, cleanup, instrumental determination, and quality control, in accordance with the relevant GB, GB/T, and HJ method standards.

Sample Preparation

Received samples are freeze-dried or air-dried at low temperature, ground, homogenized, and sieved (commonly through 2 mm and then 0.25 mm mesh). Moisture content is determined in parallel so that results can be reported on a dry-weight basis, which is required for comparison with GB screening and intervention values.

Extraction and Cleanup

Extraction is performed by pressurized fluid extraction (accelerated solvent extraction) per HJ 783-2016, Soxhlet extraction per HJ 784-2016, or ultrasonic extraction using solvent systems such as acetone–n-hexane or acetone–dichloromethane. QuEChERS-based extraction is widely used for LC-amenable current-use pesticides. Cleanup employs gel permeation chromatography (GPC) to remove humic substances and lipids, followed by solid-phase extraction on Florisil, silica, or alumina, or dispersive SPE with PSA and graphitized carbon black, to reduce matrix interference before instrumental analysis.

Instrumental Determination

Organochlorine pesticides are determined by GC-ECD according to GB/T 14550-2003, by gas chromatography according to HJ 921-2017, or by GC-MS in selected ion monitoring mode according to HJ 835-2017. Organophosphorus pesticides in soil are determined by gas chromatography according to GB/T 14552-2003. Triazine herbicides are determined by HPLC with UV or diode-array detection according to HJ 1023-2019. For multi-residue analysis and trace-level confirmation, GC-MS/MS and LC-MS/MS provide enhanced selectivity and sensitivity, with typical method detection limits in the range of 0.1 to 5 micrograms per kilogram of dry soil for most compounds. Positive findings are confirmed by retention time, qualifier ion ratios, and, where required, duplicate analysis.

Quality Assurance and Quality Control

Each analytical batch includes a method blank, laboratory duplicates with relative percent deviation control limits, matrix spike recoveries typically within 70–130 percent, surrogate standards to monitor extraction efficiency, and isotopically labeled internal standards for quantitation. Calibration uses at least five levels with correlation coefficients of 0.995 or better, and method detection limits are established and verified following HJ 168-2020. Full chain-of-custody documentation is maintained from field sampling through to the final report.

Applications

GB standard soil pesticide residue testing supports a wide range of regulatory, commercial, and scientific purposes:

• Classification of agricultural land into priority protection, safe utilization, and strict control categories under GB 15618-2018, informing planting adjustments and soil remediation priorities
• Detailed site investigation and risk assessment for land redevelopment, change of land use, and transfer transactions under GB 36600-2018
• Verification of remediation effectiveness and acceptance testing after soil treatment, replacement, or in-situ stabilization projects
• Source tracing of legacy contamination around former pesticide plants, chemical industrial parks, and waste storage areas
• Support for green-food bases, organic certification, tea and produce export bases, and geographical-indication production areas requiring verified soil quality
• Environmental impact assessment, construction project completion acceptance, and routine soil environmental monitoring networks
• Academic research, regional pollution surveys, and human health risk assessment studies

FAQ

What is the difference between GB 15618-2018 and GB 36600-2018?

GB 15618-2018 applies to agricultural land and defines risk screening values and risk control values oriented toward crop safety and food production, with key pesticide indicators including total HCH and total DDT. GB 36600-2018 applies to development land such as residential, commercial, and industrial sites and defines risk screening values and intervention values based on human health exposure across 85 parameters, including numerous organochlorine pesticides.

What do risk screening values and intervention values mean?

Risk screening values are concentration thresholds used to judge whether soil contamination risk is acceptable; results below these values generally require no further action. Exceedance of a screening value triggers detailed investigation and risk assessment. For development land, intervention values represent concentration levels above which risk management or remediation is generally required.

How low are the detection limits for pesticide residues in soil?

With GC-MS, GC-MS/MS, and LC-MS/MS methods, most organochlorine, organophosphorus, triazine, and pyrethroid pesticides can be detected at levels of 0.1 to 5 micrograms per kilogram of dry soil, which is far below typical GB screening values and sufficient for regulatory judgment.

How much soil sample is required and how should it be preserved?

Generally 500 g to 1 kg of soil is collected per sample in solvent-rinsed amber glass jars with PTFE-lined caps. Samples should be kept cold, dark, and upright at approximately 4 °C during transport and extracted as soon as possible, ideally within seven days, to minimize analyte loss and degradation.

How is the analytical method selected?

Method selection depends on the target pesticide class, the governing risk control standard, and the required sensitivity. Legacy organochlorine pesticides are usually analyzed by GC-MS or GC-ECD per HJ 835-2017, HJ 921-2017, or GB/T 14550-2003; organophosphorus pesticides by GC per GB/T 14552-2003; triazines by HPLC per HJ 1023-2019; and broad multi-residue scans by combined GC-MS/MS and LC-MS/MS. Accredited third-party laboratories can recommend an optimal method suite based on the project scenario.

How long does GB standard soil pesticide residue testing take?

For routine target lists, the typical turnaround time is 7 to 15 working days after laboratory receipt of samples, depending on the number of parameters, the complexity of the matrix, and whether confirmatory reanalysis is required.