Key Specialized Inspection for Soil Pollution: Standards, Testing Items, and Analytical Methods

Soil pollution key specialized inspection is a systematic environmental testing program designed to identify and quantify hazardous contaminants in soil and groundwater, ensuring compliance with national risk control standards for agricultural and development land. Accredited third-party laboratories apply standardized sampling protocols and advanced instrumental methods to detect heavy metals, volatile and semi-volatile organic compounds, pesticides, and persistent organic pollutants. This article provides a comprehensive technical overview of the regulatory framework, sample types, testing items, analytical methods, and practical applications of specialized soil pollution inspection.

Technical Overview

Soil pollution key specialized inspection refers to the targeted sampling, laboratory analysis, and risk-based evaluation of soil environments for pollutants designated as priorities under national soil risk control standards. Under the Chinese regulatory framework, the two core references are GB 36600-2018, the Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land, and GB 15618-2018, the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land. Together these standards define risk screening values and intervention or control values for heavy metals, volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), organochlorine pesticides, and other persistent contaminants.

The inspection process follows a staged approach consistent with the national technical guidelines for site soil pollution investigation (HJ 25.1-2019) and site monitoring (HJ 25.2-2019): systematic sampling design, field sample collection under strict quality assurance, laboratory determination by validated instrumental methods, and data evaluation against applicable thresholds. Results determine whether a land parcel requires further detailed investigation, formal risk assessment, or risk control and remediation. All analyses should be performed by accredited third-party laboratories holding ISO/IEC 17025 accreditation and national metrology accreditation, with method detection limits set well below the applicable screening values.

Testing Samples

Agricultural Land Soil

Topsoil samples collected from farmland, vegetable bases, orchards, and tea plantations, typically from the 0-20 cm plow layer with 20-40 cm subsoil samples where vertical distribution must be characterized. Grid-based sampling designs are used to represent each evaluation unit. Results are compared against the screening and control values of GB 15618-2018 for the eight regulated heavy metals, supporting land classification into priority protection, safe utilization, and strict control categories.

Development Land Soil

Borehole and test-pit samples from industrial, commercial, residential, and public management parcels, collected at stratified depths with a surface interval of 0-0.5 m and deeper intervals guided by site history and geology. Sampling grids of approximately 40 m x 40 m are common for initial screening, with denser grids in suspected source areas. Samples are assessed against the 45 basic indicators and 40 additional indicators of GB 36600-2018, which distinguish sensitive first-class land uses such as residential and educational facilities from second-class uses such as industrial and commercial development.

Contaminated Site Soil and Groundwater

Soil from suspected contaminated sites, including former chemical plants, gasworks, pesticide manufacturing facilities, electroplating workshops, fuel stations, and mining or smelting operations, together with groundwater drawn from monitoring wells installed in targeted aquifers. Groundwater data reveal contaminant migration and leaching pathways that complement soil chemistry and are essential for complete risk characterization.

Sediments, Sludge, and Solid Waste

River and lake sediments, sewage sludge, composts, and industrial solid wastes intended for land application, disposal, or classification. Where hazardous waste determination is required, leaching toxicity testing is performed to evaluate whether the material exceeds regulatory thresholds.

Testing Items

Testing packages are configured according to land use type, site history, and the applicable risk control standard. Typical indicator groups include:

• Basic physicochemical parameters: pH, moisture content, organic matter, cation exchange capacity, particle size distribution, electrical conductivity, and total nitrogen, phosphorus, and potassium.
• Heavy metals and inorganic pollutants: the eight regulated metals (cadmium, mercury, arsenic, lead, chromium, copper, nickel, and zinc), plus hexavalent chromium, beryllium, cobalt, selenium, vanadium, antimony, thallium, molybdenum, manganese, and fluoride where site conditions indicate.
• Volatile organic compounds: benzene, toluene, ethylbenzene, and xylenes; chlorinated methanes, ethanes, and ethenes such as trichloroethylene and tetrachloroethylene; and other regulated volatiles.
• Semi-volatile organic compounds: phenols, anilines, phthalate esters, nitroaromatics, chlorinated hydrocarbons, and the sixteen priority polycyclic aromatic hydrocarbons including benzo[a]pyrene.
• Pesticides and persistent organic pollutants: organochlorine pesticides such as DDT, hexachlorocyclohexane, and chlordane; organophosphorus pesticides; and polychlorinated biphenyls.
• Petroleum hydrocarbons: total petroleum hydrocarbons determined in the C6-C9 and C10-C40 carbon fractions.
• Dioxins and furans: the seventeen 2,3,7,8-substituted PCDD/PCDF congeners reported as toxic equivalents.
• Site-specific indicators: cyanide, ammonia nitrogen, nitrate, and other parameters selected on the basis of historical land use.

Testing Methods

Field work follows the technical specifications for soil environmental monitoring (HJ/T 166-2004) and groundwater environmental monitoring (HJ 164-2020). Sample handling protocols for volatile analytes include zero-headspace containers, immediate cooling to 4 degrees Celsius, and analysis within validated holding times. Laboratory methods are summarized below:

• Heavy metals: total digestion with hydrochloric, nitric, hydrofluoric, and perchloric acids or aqua regia extraction (ISO 11466; HJ 803-2016), followed by ICP-OES or ICP-MS (ISO 17294), graphite furnace atomic absorption spectrometry (GB/T 17141-1997 for lead and cadmium), and atomic fluorescence spectrometry (GB/T 22105; HJ 680-2013) for mercury, arsenic, selenium, antimony, and bismuth.
• Hexavalent chromium: alkaline extraction in an oxygen-free environment followed by atomic absorption or spectrophotometric determination (HJ 1082-2019).
• VOCs: purge-and-trap or headspace gas chromatography-mass spectrometry (HJ 605-2011; HJ 742-2015).
• SVOCs and PAHs: ultrasonic or accelerated solvent extraction followed by GC-MS (HJ 834-2017) and high performance liquid chromatography with fluorescence detection (HJ 784-2016).
• Organochlorine pesticides and PCBs: GC-MS or gas chromatography with electron capture detection (HJ 835-2017; HJ 743-2015).
• Petroleum hydrocarbons: gas chromatography with flame ionization detection (HJ 1021-2019).
• Dioxins and furans: isotope dilution high-resolution gas chromatography-high-resolution mass spectrometry (HJ 77.4) with sub-picogram-level detection capability.
• Leaching toxicity: sulfuric acid-nitric acid extraction or horizontal oscillation leaching procedures for hazardous waste identification (GB 5085.3-2007; HJ/T 299-2007; HJ 557-2010).

Quality assurance requires field duplicates at a minimum rate of 10 percent, transport and equipment rinsate blanks for volatile analytes, certified reference materials, matrix spikes, and laboratory method blanks. Data validation and review against national reporting conventions are performed before results are issued.

Applications

Key specialized soil pollution inspection supports regulatory compliance and decision-making across a wide range of scenarios:

• National and regional soil pollution status surveys, detailed investigations, and soil environment ledger management.
• Classification and safe utilization management of agricultural land, including farmland affected by elevated cadmium and other heavy metals.
• Redevelopment of brownfield and former industrial sites prior to changes in land use or property transfer.
• Baseline investigation, risk assessment, remediation design, and post-remediation effect evaluation for contaminated sites.
• Soil environmental impact assessment and completion acceptance for construction projects.
• Compliance monitoring around mining, smelting, chemical production, and waste disposal facilities.
• Safety evaluation of sewage sludge, compost, and reclaimed materials intended for land application.

FAQ

What is the difference between risk screening values and intervention values?

Risk screening values are thresholds below which contaminant concentrations generally pose no unacceptable human health risk, while concentrations above screening values trigger the need for detailed investigation and risk assessment. Intervention values, applicable under GB 36600-2018 for development land, indicate a level of risk that requires risk control or remediation measures.

Which standard applies to my project, GB 15618-2018 or GB 36600-2018?

GB 15618-2018 applies to agricultural land including cultivated land, orchards, and pasture, whereas GB 36600-2018 applies to development land such as industrial, commercial, residential, and public management parcels. Mixed-use areas are evaluated against the standard corresponding to each land use function, applying the more sensitive threshold where uses overlap.

How many sampling points and what sampling depths are required?

Sampling density depends on the investigation stage and site area. Initial site investigations commonly use grids of approximately 40 m x 40 m, with denser spacing in suspected source zones, while agricultural surveys are designed on evaluation units with grid or diagonal layouts. Development land sampling typically includes a surface interval of 0-0.5 m plus deeper intervals at lithological boundaries and potential contamination pathways identified during borehole logging.

How long does specialized soil testing take?

Routine testing packages for heavy metals, basic parameters, and common organics are generally completed within 7 to 15 working days after sample receipt. Dioxin and furan analysis and extended organic schedules may require 15 to 25 working days due to extraction, cleanup, and high-resolution mass spectrometric confirmation requirements.

Are soil standards based on total content or leachable content?

The risk control standards for soil are based on total element concentrations determined after aqua regia or total digestion. Leaching tests, such as the sulfuric acid-nitric acid extraction method, are applied separately for hazardous waste identification and for evaluating contaminant mobility toward groundwater.

What qualifications should the testing laboratory hold?

The laboratory should hold national metrology accreditation for the specific soil and groundwater methods reported, together with ISO/IEC 17025 laboratory accreditation. Method detection limits, calibration traceability, and participation in proficiency testing programs should be verifiable for all reported parameters.