Soil environmental current status assessment is a systematic, standards-based investigation process that characterizes the existing quality of soil at a defined site, identifies contaminant sources and concentration levels, and determines whether they pose unacceptable risks to human health and the environment under current or planned land use. This article provides a comprehensive technical overview of the assessment framework, sampling protocols, analytical testing items, laboratory methods, and typical industrial and regulatory applications.
Technical Overview
Soil environmental current status assessment is a structured evaluation process used to establish the baseline environmental condition of soil at a specific site, quantify the presence and distribution of potential contaminants, and support risk-based decision making for land management, redevelopment, and regulatory compliance. It serves as the technical foundation for environmental impact assessment (EIA), soil pollution investigation reports, and remediation planning.
Assessment programs are typically conducted in accordance with recognized national and international frameworks, including GB 36600-2018 (Risk Control Standard for Soil Contamination of Development Land), GB 15618-2018 (Risk Control Standard for Soil Contamination of Agricultural Land), HJ 25.1-2019 (Technical Guideline for Investigation on Soil Contamination of Development Land), HJ 25.2-2019 (Technical Guideline for Soil Environmental Monitoring of Development Land), HJ 25.3-2019 (Technical Guideline for Risk Assessment of Soil Contamination of Development Land), and HJ/T 166-2004 (Technical Specification for Soil Environmental Monitoring). International reference documents include the ISO 10381 series on soil quality sampling and ASTM E1903 on Phase II environmental site assessment.
The assessment generally proceeds through three stages: a preliminary study covering site history review, document analysis, and site reconnaissance to develop a conceptual site model; preliminary sampling and laboratory analysis compared against risk screening values; and, where screening values are exceeded, detailed investigation followed by site-specific human health and ecological risk assessment. Land use classification is central to the evaluation, as GB 36600-2018 distinguishes first-class land use (residential, schools, medical facilities, and elderly care) from second-class land use (industrial, commercial, and logistics), each with distinct screening values and control values.
Core objectives of a soil environmental current status assessment include:
- Establishing pre-construction or pre-transaction baseline contaminant concentrations
- Identifying pollution sources, impacted zones, and vertical extent of contamination
- Determining compliance with applicable risk screening and control values
- Supporting risk assessment, remediation target derivation, and land use suitability conclusions
- Providing defensible data for regulatory filing, legal due diligence, and liability allocation
Testing Samples
Surface Soil Samples
Surface soil samples are typically collected from 0 to 0.5 m below ground level, where impacts from atmospheric deposition, historical spills, and industrial handling activities are most pronounced. Sampling locations are arranged on systematic grids across the site, with grid density determined by site area, investigation phase, and the distribution of potential contamination sources identified during reconnaissance.
Subsurface and Deep Soil Samples
Subsurface samples (0.5 to 1.5 m) and deep samples (below 1.5 m) are collected using direct-push probing, hydraulic rotary drilling, or hollow-stem auger methods. Samples are targeted at stratigraphic boundaries, the base of fill layers, suspected source zones, and at least 0.5 m below the observed groundwater table to fully characterize vertical contaminant migration. Undisturbed cores are retained for lithological description and geotechnical correlation.
Soil Gas Samples
Soil gas samples are collected from temporary or permanent probes installed at approximately 1.2 to 1.5 m depth to evaluate the vapor intrusion pathway for volatile organic compounds. Active sampling into evacuated canisters or sorbent tubes, analyzed in accordance with US EPA TO-15 or TO-17 methodology, provides concentration data for indoor air risk modeling.
Background and Reference Samples
Background samples are collected from unimpacted areas with lithology similar to the site, typically located upwind and cross-gradient of suspected sources. These samples establish local geochemical baseline values, enabling statistical discrimination between anthropogenic contamination and naturally elevated element concentrations.
Associated Groundwater Samples
Although focused on soil, comprehensive status assessments typically include paired groundwater sampling from newly installed or existing monitoring wells positioned hydraulically upgradient and downgradient of the site, allowing lateral contaminant migration and leaching pathways to be evaluated within the same investigation campaign.
Testing Items
Testing parameters are selected based on site history, industrial processes previously or currently conducted, chemical storage records, and the planned future land use. Standard parameter suites include:
- Basic physicochemical indicators: pH, moisture content, organic matter, particle size distribution, cation exchange capacity, and redox potential
- Heavy metals and metalloids (eight basic items): arsenic, cadmium, total chromium, copper, mercury, nickel, lead, and zinc
- Heavy metals (eight additional items): antimony, beryllium, cobalt, manganese, selenium, silver, thallium, and vanadium, plus hexavalent chromium where relevant
- Volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, xylenes, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, vinyl chloride, and other regulated halogenated and monocyclic aromatics
- Semi-volatile organic compounds (SVOCs): polycyclic aromatic hydrocarbons including benzo[a]pyrene, phthalate esters, phenolic compounds, nitroaromatics, and chlorinated anilines
- Persistent organic pollutants: organochlorine pesticides, polychlorinated biphenyls (PCBs), and dioxins and furans at sites with combustion or specific industrial histories
- Petroleum hydrocarbons: total petroleum hydrocarbon fractions C6-C9 and C10-C40 for fuel stations, refineries, and hydrocarbon handling facilities
- Other inorganic parameters: total and easily released cyanide, fluoride, ammonia nitrogen, and water-soluble salts
Testing Methods
All sampling and analytical work should be performed by accredited third-party laboratories operating under ISO/IEC 17025 quality management systems, with chain-of-custody documentation maintained from field collection through data reporting. Principal analytical methodologies include:
- Heavy metals: acid digestion (nitric-hydrochloric-hydrofluoric mixture) with microwave assistance per HJ 803-2016, followed by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES); mercury and arsenic by atomic fluorescence spectrometry (AFS) or direct thermal decomposition; hexavalent chromium by alkaline digestion with colorimetric determination; portable X-ray fluorescence (XRF) per US EPA Method 6200 for rapid field screening
- VOCs: purge-and-trap gas chromatography-mass spectrometry (GC-MS) per HJ 605-2011 or US EPA Method 8260D, with samples collected using dedicated coring devices and preserved in methanol or sodium bisulfate at 4 degrees Celsius with strict holding times
- SVOCs: accelerated solvent extraction or ultrasonic extraction with silica gel cleanup, followed by GC-MS determination per HJ 834-2017 or US EPA Method 8270E
- Organochlorine pesticides and PCBs: gas chromatography with electron capture detection or GC-MS per HJ 835-2017 and HJ 911-2017
- Petroleum hydrocarbons: gas chromatography with flame ionization detection per HJ 1021-2019 or US EPA Method 8015C
- pH: potentiometric determination per ISO 10390 or HJ 962-2018; organic matter by potassium dichromate oxidation; moisture content by gravimetric drying
Quality assurance and quality control measures follow HJ/T 166-2004 and laboratory method requirements, including field duplicates at a frequency of at least 10 percent, trip and equipment blanks, matrix spikes, surrogate recoveries for organic analyses, continuing calibration verification, and independent data validation before results are compared against screening and control values.
Applications
Soil environmental current status assessment is applied across a wide range of regulatory, industrial, and commercial scenarios:
- Environmental impact assessment of new construction, expansion, and technical renovation projects requiring baseline soil data
- Redevelopment of former industrial land, implementing the principle of investigation before land supply where land use changes to sensitive purposes
- Periodic self-monitoring and soil pollution status reporting by enterprises designated as key soil pollution supervision units
- Site closure and decommissioning of gas stations, chemical plants, electroplating facilities, tanneries, smelters, and pesticide manufacturing sites
- Agricultural land categorization, safety utilization planning, and delineation of strictly controlled areas under GB 15618-2018
- Mining districts, oil and gas field developments, and solid waste disposal sites requiring baseline and longitudinal monitoring
- Environmental due diligence for mergers, acquisitions, financing, and brownfield transactions requiring defensible liability evaluation
FAQ
When is a soil environmental current status assessment legally required?
Assessment is required when land use changes to a sensitive purpose, such as converting industrial land to residential or educational use; when an EIA for a new project demands baseline soil data; when key regulated enterprises conduct periodic pollution status investigations; and when contamination accidents or regulatory enforcement actions necessitate a formal site investigation.
What is the difference between GB 36600-2018 and GB 15618-2018?
GB 36600-2018 applies to development land and establishes risk screening values and control values for 85 inorganic and organic parameters differentiated by first-class and second-class land use. GB 15618-2018 applies to agricultural land, setting risk screening values and risk control values focused primarily on inorganic contaminants and key pesticides relevant to crop safety and food security.
How are sampling point numbers and locations determined?
Point density is determined by site area and investigation phase according to HJ 25.1-2019 and HJ 25.2-2019, with systematic grids supplemented by judgmental points placed at former storage areas, loading zones, drain outlets, and underground tank locations identified during site reconnaissance and geophysical surveys.
What happens if analytical results exceed the screening values?
Exceedance of a screening value does not automatically mandate remediation. Instead, a detailed investigation is triggered, followed by a site-specific human health risk assessment under HJ 25.3-2019 to derive remediation target values. If concentrations exceed control values, risk control or remediation measures become obligatory before sensitive land use proceeds.
How long does a complete assessment take?
A typical program requires two to four weeks for the preliminary study and field investigation, one to two weeks for laboratory analysis, and an additional one to two weeks for data evaluation and report preparation, with detailed investigations and risk assessments extending the overall timeline depending on site complexity.