Soil volatile halogenated hydrocarbons (VHHs) testing is a critical environmental analysis used to identify and quantify chlorinated and brominated solvents—such as trichloroethylene, tetrachloroethylene, and carbon tetrachloride—in soil at contaminated sites. This technical guide explains the target analytes, internationally recognized sampling and analytical methods, applicable standards, and how accredited third-party laboratories support site investigation, risk assessment, and remediation projects.
Technical Overview
Volatile halogenated hydrocarbons (VHHs) are a family of low-molecular-weight chlorinated and brominated organic compounds characterized by high vapor pressure and boiling points generally below 200°C. Common members include chlorinated methanes (chloroform, carbon tetrachloride, dichloromethane), chlorinated ethanes (1,2-dichloroethane, 1,1,1-trichloroethane), and chlorinated ethenes (vinyl chloride, trichloroethylene, tetrachloroethylene). These compounds entered the environment through decades of use as industrial solvents, metal degreasers, dry-cleaning agents, chemical intermediates, and agricultural fumigants, as well as through landfill leachate, leaking underground storage tanks, and accidental spills.
In soil, VHHs exhibit distinctive environmental behavior that makes them particularly challenging contaminants. Many chlorinated ethenes and ethanes act as dense non-aqueous phase liquids (DNAPLs) that migrate downward through the vadose zone under gravity, while their high volatility drives rapid partitioning into soil gas, creating pathways for vapor intrusion into buildings and groundwater contamination. Several of these compounds, including vinyl chloride and trichloroethylene, are classified as known or probable human carcinogens, which has driven strict regulatory limits such as the risk screening values established in GB 36600-2018 for development land. Accurate, defensible analytical data is therefore essential for site investigation, human health risk assessment, and remediation decision-making.
Testing Samples
Surface and Shallow Soil
Surface soil samples, typically collected from depths of 0 to 1.5 meters, are analyzed to evaluate contamination from spillage, historical solvent handling, and atmospheric deposition. These samples are commonly taken during preliminary site investigations and screening campaigns using stainless-steel trowels or hand augers, with portable photoionization detectors (PIDs) used for field screening to guide sample selection.
Subsurface and Deep Soil
Subsurface samples recovered from boreholes drilled with direct-push rigs, hollow-stem augers, or sonic drilling methods are used to delineate vertical contaminant plumes and identify DNAPL source zones. Because volatile losses increase with sample handling, subsurface VHH samples must be transferred rapidly from split spoons or core liners into sealed sample containers with minimal disturbance and exposure to air.
Industrial, Brownfield, and Construction Land Soils
Soils from former industrial facilities, gasworks, chemical plants, dry-cleaning sites, and brownfield parcels undergoing redevelopment are routinely tested for VHHs to determine whether contaminant concentrations exceed risk screening values and whether remediation is required before land reuse or disposal.
Sediment and Stockpiled Material
Riverbed and lacustrine sediments impacted by industrial discharges, as well as excavated soil stockpiles pending disposal or reuse, are analyzed to classify waste streams, verify treatment performance, and support compliance with disposal facility acceptance criteria.
Testing Items
Typical analytical scopes cover 20 to 40 individual halogenated compounds, depending on the applicable regulatory framework. The most frequently requested target analytes include:
- Halogenated methanes: chloromethane, bromomethane, dichloromethane (methylene chloride), chloroform, carbon tetrachloride
- Halogenated ethanes: 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2-dibromoethane
- Halogenated ethenes: vinyl chloride, 1,1-dichloroethene, cis-1,2-dichloroethene, trans-1,2-dichloroethene, trichloroethylene (TCE), tetrachloroethylene (PCE)
- Brominated trihalomethanes: bromodichloromethane, dibromochloromethane, bromoform
- Halogenated aromatics and related compounds: chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, where included in the site-specific compound list
Testing Methods
Sample Collection and Preservation
Because VHHs are readily lost through volatilization and biodegradation, sampling protocols follow strict practices such as those in ASTM D4547, US EPA Method 5035A, and HJ/T 166-2004. Soils are collected using zero-headspace vials or coring devices, preserved with sodium bisulfate or methanol at low contaminant levels, transported at 4±2°C in the dark, and analyzed within the standard 14-day holding time. Field duplicates and trip blanks accompany each sampling event to monitor precision and cross-contamination.
Purge-and-Trap GC-MS
Purge-and-trap extraction coupled with gas chromatography-mass spectrometry (GC-MS) is the most sensitive and widely used technique, as specified in HJ 605-2011, HJ 735-2015, and US EPA Method 8260D. An aliquot of soil is dispersed in water or methanol extract, purged with inert gas at elevated temperature, and volatile analytes are trapped on an adsorbent cartridge before thermal desorption into the GC column. Mass spectral detection in full-scan or selected-ion monitoring (SIM) mode achieves method detection limits as low as 0.1 µg/kg and provides definitive compound identification.
Static Headspace GC-MS
Static headspace GC-MS, described in HJ 741-2015, US EPA Method 5021A, and ISO 22155, equilibrates the soil-water mixture in a sealed vial at a controlled temperature (typically 60–85°C) and injects an aliquot of the equilibrated headspace gas into the GC-MS. The technique is robust, cost-effective, and well suited to high-throughput screening and soils with high moisture or organic content, with detection limits generally in the range of 1 to 10 µg/kg.
Quality Assurance and Quality Control
Defensible data packages from accredited third-party laboratories include multi-point initial calibrations with continuing calibration verification, instrument tuning checks (such as BFB), method blanks, laboratory control samples, matrix spikes and duplicates, and surrogate standard recoveries for every sample. These controls quantify bias, precision, and completeness, and the results are reported with full data qualification according to the relevant data validation guidelines.
Applications
Soil VHH testing data underpin a wide range of environmental management activities, including:
- Phase II environmental site assessments and detailed contamination delineation at industrial and commercial parcels
- Risk screening against regulatory criteria such as GB 36600-2018 and comparable international soil quality guidelines
- Design and verification of remediation technologies, including soil vapor extraction, thermal desorption, and excavation disposal
- Vapor intrusion assessments for buildings constructed above or near chlorinated solvent plumes
- Environmental due diligence for property transactions, financing, and brownfield redevelopment
- Regulatory compliance reporting, pollution incident investigations, and litigation support requiring chain-of-custody documentation
FAQ
What detection limits can be achieved for VHHs in soil?
With purge-and-trap GC-MS, method detection limits typically range from 0.1 to 1 µg/kg for individual compounds. Static headspace GC-MS usually delivers detection limits of approximately 1 to 10 µg/kg, which remains well below most regulatory screening values for development land.
Why is sample handling so critical for this analysis?
Volatile halogenated hydrocarbons can be lost by volatilization, biodegradation, or cross-contamination within minutes of soil disturbance. Sealed, preserved, and refrigerated containers with minimal headspace, combined with strict holding times, are essential to ensure the analytical results represent true field concentrations.
Which standard should my project follow?
The choice depends on the jurisdiction and project objective. In China, HJ 605-2011, HJ 735-2015, and HJ 741-2015 define the reference methods, with GB 36600-2018 supplying risk screening values. In North America, US EPA Methods 5035A and 8260D are standard practice, while ISO 22155 applies to many international projects. Accredited third-party laboratories can advise on the most appropriate method combination.
How long does the analysis take?
Standard turnaround is typically 5 to 10 working days from laboratory receipt, with expedited 48-to-72-hour services available for urgent site investigation or remediation verification programs.
Can soil gas and groundwater be tested alongside soil?
Yes. Comprehensive vapor intrusion and plume delineation studies combine soil VHH analysis with soil gas sampling (passive or active) and groundwater testing using equivalent purge-and-trap or headspace GC-MS methods, providing a complete picture of contaminant distribution across all environmental media.
