Soil pollutant analysis is the systematic sampling and laboratory testing of soil to identify and quantify heavy metals, petroleum hydrocarbons, pesticides, volatile organic compounds, and other hazardous substances that threaten human health, groundwater, and ecosystems. This technical guide explains typical sample types, testing items, internationally recognized standards such as ISO, ASTM, EN, and GB, and the analytical methods—including ICP-MS and GC-MS—commonly used by accredited third-party laboratories.
Technical Overview
Soil pollutant analysis is a core component of environmental site investigation, land redevelopment, and agricultural quality management. Soil becomes contaminated through industrial discharges, fuel and chemical spills, improper waste disposal, atmospheric deposition, and excessive application of fertilizers and pesticides. Because pollutants persist in soil for decades and can migrate into groundwater and the food chain, quantitative chemical analysis is essential for assessing exposure risks and determining whether remediation is required.
Soil contaminants are generally divided into three categories: inorganic pollutants such as heavy metals and metalloids (arsenic, cadmium, chromium, lead, mercury, nickel, copper, zinc), organic pollutants such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), volatile and semi-volatile organic compounds (VOCs and SVOCs), and dioxins, and emerging contaminants such as per- and polyfluoroalkyl substances (PFAS), pharmaceutical residues, and microplastics.
The evaluation framework is risk-based. GB 36600-2018 establishes risk screening values and intervention values for 85 indicators applicable to development land, while GB 15618-2018 sets risk screening and control values for agricultural land. International method standards published by ISO, ASTM, EN, and JIS govern sampling, pretreatment, and instrumental analysis. All analytical work should be performed by accredited third-party laboratories operating under an ISO/IEC 17025 quality management system to ensure data defensibility for regulatory submission and litigation support.
Testing Samples
Surface Soil Samples
Surface soil, typically collected from 0 to 0.5 m, is the most commonly analyzed matrix because it directly contacts site users, children, construction workers, and crops. Samples are collected using stainless steel or non-contaminating tools at grid-based or judgmental locations, transferred to glass or polyethylene containers, and composited only when the data quality objectives permit. For farmland, samples are usually taken from the plow layer at 0 to 20 cm, with deeper 20 to 40 cm profile samples added when vertical migration is suspected.
Subsurface Soil and Borehole Core Samples
Subsurface investigation uses hand augers, direct-push rigs, or drill rigs to recover continuous or interval cores from 0.5 m down to 6 m or deeper. Cores are logged by lithology, photographed, and subsampled at standard depth intervals, with elevated readings from field screening instruments (photoionization detectors or portable XRF) used to select intervals for laboratory analysis. Subsurface data define the vertical extent of contamination and inform soil volume estimates for remediation design.
Farmland and Greenhouse Soil
Agricultural soil samples are collected for food safety verification, soil fertility assessment, and origin environment certification. Testing typically focuses on heavy metals regulated by GB 15618-2018, pesticide residues such as DDT and hexachlorocyclohexane, and nutrient parameters including nitrogen, phosphorus, potassium, organic matter, and pH. Composite sampling across a field is standard, typically one composite per 20 to 100 mu depending on the investigation objective.
Industrial and Contaminated Site Soil
Soil from former chemical plants, electroplating facilities, refineries, gas stations, landfills, and mining areas carries the widest range of potential contaminants. Sample collection follows grid-based designs, commonly 40 m by 40 m for initial screening and refined to 20 m by 20 m for detailed characterization, with additional judgmental samples at storage tanks, pipelines, drain outlets, and spill areas.
Sediment and Soil-Like Matrices
River and lake sediments, dredged material, sludge, compost, and construction fill can be analyzed using the same analytical platforms. These matrices often require modified pretreatment, such as freeze-drying and higher dilution factors, and results may be compared against sediment quality guidelines or disposal acceptance criteria.
Testing Items
A testing program is designed according to land use, site history, and regulatory triggers. The principal parameter groups are listed below.
- Heavy metals and inorganic pollutants: arsenic, cadmium, chromium, hexavalent chromium, copper, lead, mercury, nickel, zinc, beryllium, vanadium, antimony, selenium, thallium, cobalt, molybdenum, barium, manganese, total fluoride, and cyanide.
- Volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, xylenes (BTEX), chlorinated solvents such as trichloroethylene, tetrachloroethylene, and dichloromethane, vinyl chloride, and petroleum ether fractions.
- Semi-volatile organic compounds (SVOCs): the 16 priority PAHs including benzo[a]pyrene, phthalate esters, phenols and chlorophenols, nitrobenzenes, anilines, and organotin compounds.
- Persistent organic pollutants: organochlorine pesticides (DDT, hexachlorocyclohexane, aldrin, dieldrin), polychlorinated biphenyls, and the 17 toxic dioxin and furan congeners plus 12 dioxin-like PCBs expressed as toxicity equivalents (TEQ).
- Petroleum hydrocarbons: total petroleum hydrocarbons (TPH) with carbon fractionation, typically C6 to C10 and C10 to C40, plus fuel oxygenates and additives such as MTBE.
- Emerging contaminants: PFAS compounds, pharmaceutical and personal care product residues, antibiotics, antibiotic resistance genes, and microplastics.
- Physicochemical and nutritional properties: pH, electrical conductivity, organic matter and total organic carbon, cation exchange capacity, particle size distribution, moisture content, oxidation-reduction potential, and total or available nitrogen, phosphorus, and potassium.
Testing Methods
Sampling and Sample Preparation
Sampling is performed in accordance with the ISO 10381 series, EN 16179, and relevant national technical specifications. Samples for VOC analysis are collected first, without homogenization, into sealed containers with minimal headspace, preserved at 4 °C, and analyzed within the standard holding period. Samples for metals and SVOCs are air-dried or freeze-dried, gently disaggregated, sieved through a 2 mm nylon or stainless steel mesh, and reduced by quartering or riffle splitting, following ISO 11464. Moisture content is determined gravimetrically according to ISO 11465 so that results can be reported on a dry-weight basis.
Heavy Metal and Inorganic Analysis
Metals are brought into solution by aqua regia digestion following ISO 11466, microwave-assisted digestion following ISO 12914, or total digestion with hydrofluoric acid following ISO 14869-1 for comparison with total-content criteria. Quantification is performed by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES) following ISO 17294-2 and ISO 22036, by flame or electrothermal atomic absorption spectrometry following ISO 11047, by hydride generation or electrothermal AAS for arsenic and selenium following ISO 20280, and by cold vapor AAS or atomic fluorescence spectrometry for mercury following ISO 16772. Hexavalent chromium is determined separately after alkaline digestion using diphenylcarbohydrazide spectrophotometry. Field screening with portable energy-dispersive XRF instruments, following ISO 13196, is widely used to delineate hotspots in real time.
Organic Contaminant Analysis
VOCs are extracted by static headspace or purge-and-trap techniques and quantified by gas chromatography-mass spectrometry (GC-MS) following ISO 22155. PAHs and other SVOCs are extracted by pressurized fluid extraction, ultrasonic extraction, or Soxhlet extraction, cleaned up by silica gel or gel permeation chromatography, and quantified by GC-MS following ISO 18287 for PAHs and ISO 14154 for chlorophenols. Organochlorine pesticides and PCBs are analyzed by GC with electron capture detection or GC-MS following ISO 10382. Total petroleum hydrocarbons are quantified by GC-FID following ISO 16703 or the risk-based fractionation approach of ISO 16558. Dioxins, furans, and dioxin-like PCBs require high-resolution GC-MS at sub-nanogram-per-kilogram detection limits following EN 16190. PFAS compounds are analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) under strict PFAS-free sampling and laboratory protocols.
Quality Assurance and Data Validation
Accredited third-party laboratories operating under ISO/IEC 17025 support every batch with method blanks, laboratory duplicates, matrix spikes, surrogate standards, and certified reference materials to verify accuracy, precision, and recovery. Method detection limits and limits of quantification must be below the applicable regulatory screening values. Deliverables typically include a chain-of-custody record, a QC summary, and, where required, a measurement uncertainty statement so that results can withstand regulatory review and legal challenge.
Applications
Soil pollutant analysis supports decision-making across the entire land management lifecycle, from initial investigation through remediation closeout. Typical applications include:
- Phase I and Phase II environmental site assessments conducted under ASTM E1527 and ASTM E1903 for property transactions, financing, and mergers.
- Brownfield redevelopment and change-of-land-use approval, demonstrating compliance with GB 36600-2018 screening and intervention values.
- Agricultural soil quality surveys and safe-production-base verification for farmland, orchards, and greenhouse operations.
- Remediation design, progress monitoring, and post-remediation acceptance testing for excavation, soil washing, thermal desorption, and bioremediation projects.
- Construction surplus soil characterization and disposal or reuse classification for infrastructure and urban development projects.
- Environmental emergency response after chemical spills, pipeline leaks, or flooding events, where rapid on-site screening is combined with confirmatory laboratory analysis.
- Compliance monitoring for mining, oil and gas, landfill, and industrial operations, including groundwater protection programs.
- Expert evidence and technical support for environmental litigation, insurance claims, and pollution liability disputes.
FAQ
What is the difference between GB 36600 and GB 15618?
GB 36600-2018 applies to development land such as residential, commercial, and industrial parcels and defines risk screening values and intervention values for 85 indicators, including heavy metals, VOCs, and SVOCs. GB 15618-2018 applies to agricultural land and defines risk screening values and control values oriented toward protecting crop safety and production. The applicable standard depends on the current or planned land use, and both are commonly applied when land is being converted between uses.
How deep should soil samples be collected?
For development land investigation, samples are typically collected from surface soil at 0 to 0.5 m, shallow subsurface at 0.5 to 1.5 m, and deeper intervals at 1.5 to 3 m and 3 to 6 m, with deeper sampling where contamination or underground structures are suspected. For agricultural surveys, the plow layer at 0 to 20 cm is standard, supplemented by deeper profile samples where vertical migration is a concern.
How should samples be preserved for VOC analysis?
VOC samples must be collected directly from freshly exposed soil without mixing or homogenization, placed in sealed jars or vials with minimal headspace or preserved in methanol, kept at 4 °C in the dark, and delivered to the laboratory under full chain of custody. Analysis is normally required within 7 to 14 days of collection to minimize volatilization losses.
Can on-site XRF screening replace laboratory testing?
No. Portable XRF following ISO 13196 is an excellent delineation and decision support tool that provides results within minutes, but its detection limits, spectral interferences, and moisture sensitivity mean it cannot fully replace confirmatory analysis. Regulatory submissions and remediation acceptance are based on accredited laboratory results, with XRF data used to guide sample placement and reduce costs.
What detection limits can be achieved?
ICP-MS routinely achieves detection limits in the microgram-per-kilogram to low milligram-per-kilogram range for most metals, with mercury and arsenic methods reaching sub-microgram-per-kilogram levels by cold vapor and hydride generation techniques. GC-MS methods for PAHs, VOCs, and pesticides typically reach microgram-per-kilogram levels, while dioxin analysis by high-resolution GC-MS achieves picogram-per-kilogram detection with TEQ reporting.
How long does soil pollutant analysis take?
Standard heavy metal panels are typically completed within 5 to 7 working days, organic compound suites within 7 to 12 working days, and specialist analyses such as dioxins or PFAS within 10 to 20 working days after laboratory receipt. Expedited turnaround can often be arranged for urgent project schedules, and Rush priority should be specified at the time of quotation and sample submission.