Water quality heavy metal testing to Chinese national standards (GB) is the laboratory-based determination of regulated metallic contaminants—such as lead, cadmium, mercury, arsenic, and chromium—in drinking water, surface water, groundwater, and wastewater using methods specified under GB standards including GB 5749-2022, GB 3838-2002, and GB/T 5750.6-2023. Accurate, standards-compliant heavy metal analysis is essential for regulatory compliance, public health protection, and environmental risk management. This article explains the applicable GB framework, sample types, target analytes, detection techniques, quality control requirements, and typical applications of heavy metal testing in water.
Technical Overview
Heavy metals in water refer to metallic elements—and the metalloid arsenic—that persist in the environment, bioaccumulate in the food chain, and exert toxicity even at trace concentrations. In the Chinese regulatory system, the control of heavy metals in water is governed by a hierarchy of mandatory quality standards and supporting method standards. Compliance testing must be performed by accredited third-party laboratories or qualified monitoring institutions using nationally validated analytical methods.
- GB 5749-2022 – Hygienic standard for drinking water quality, defining limit values for arsenic, cadmium, chromium(VI), lead, mercury, selenium, aluminum, iron, manganese, copper, zinc, antimony, barium, beryllium, boron, molybdenum, nickel, silver, and thallium.
- GB 3838-2002 – Environmental quality standard for surface water, classifying rivers, lakes, and reservoirs into five functional classes with graded limits for copper, zinc, selenium, arsenic, mercury, cadmium, chromium(VI), and lead.
- GB/T 14848-2017 – Standard for groundwater quality, with Class III limits generally aligned to drinking water criteria.
- GB 8978-1996 – Integrated wastewater discharge standard, setting maximum allowable discharge concentrations for total mercury, total cadmium, total chromium, chromium(VI), total arsenic, total lead, total nickel, copper, zinc, and manganese.
- GB/T 5750.6-2023 – Standard examination methods for drinking water, Part 6: metal parameters, specifying ICP-MS, ICP-OES, atomic absorption, and atomic fluorescence procedures.
- Complementary industry standards such as HJ 700-2014 (65 elements by ICP-MS) and HJ 766-2015 (32 elements by ICP-OES) extend the scope to environmental water matrices.
A key technical distinction in all GB-based reporting is between total metals (measured after acid digestion of the unfiltered sample) and dissolved metals (measured after filtration through a 0.45 µm membrane). Regulatory limits and acceptance criteria must always be matched to the correct fraction. In addition, the method detection limit of the selected procedure is generally required to reach at least one quarter—and preferably one tenth—of the applicable regulatory limit.
Testing Samples
Drinking Water and Packaged Water
Tap water at treatment plant outlets and distribution network points of compliance, as well as bottled, barrelled, and purified water products, are tested against GB 5749-2022. Sampling follows the hygienic procedures of GB/T 5750.2, including flushing of taps, sterile or acid-washed containers depending on the analyte, and same-day transport to the laboratory.
Surface Water
Rivers, lakes, reservoirs, and estuarine waters are classified under GB 3838-2002. Sampling points and frequencies follow national environmental monitoring technical specifications, with particular attention to reaches downstream of mining, smelting, electroplating, and chemical industry zones where heavy metal loads are elevated.
Groundwater
Water from drinking water wells, agricultural wells, and monitoring wells is assessed under GB/T 14848-2017. Groundwater impacted by landfill leachate, mine drainage, or industrial seepage is a priority matrix for arsenic, lead, cadmium, chromium, and nickel screening.
Industrial and Municipal Wastewater
Effluent from electroplating, metal finishing, battery manufacturing, leather tanning, mining and ore processing, non-ferrous smelting, printed circuit board production, and municipal treatment plants is tested against GB 8978-1996 and applicable sector-specific discharge standards before release to receiving waters or municipal networks.
Seawater and Brackish Water
Marine and near-shore waters are evaluated under GB 3097-1997. High dissolved salt content demands matrix-matched calibration, dilution control, or collision/reaction cell techniques to suppress spectral and matrix interferences.
Special-Purpose Water
Aquaculture water (GB 11607), farmland irrigation water, reclaimed water, cooling and boiler feed water, and ultrapure process water for electronics and pharmaceutical manufacturing each carry dedicated heavy metal requirements that accredited third-party laboratories can address with tailored GB or ISO method packages.
Testing Items
The core regulated heavy metals and representative limit values for drinking water under GB 5749-2022 include:
- Arsenic (As): 0.01 mg/L
- Cadmium (Cd): 0.005 mg/L
- Chromium, hexavalent (Cr(VI)): 0.05 mg/L
- Lead (Pb): 0.01 mg/L
- Mercury (Hg): 0.001 mg/L
- Selenium (Se): 0.01 mg/L
- Aluminum (Al): 0.2 mg/L
- Iron (Fe): 0.3 mg/L
- Manganese (Mn): 0.1 mg/L
- Copper (Cu): 1.0 mg/L
- Zinc (Zn): 1.0 mg/L
Extended trace metals frequently included in monitoring programs comprise antimony, barium, beryllium, boron, molybdenum, nickel, silver, thallium, tin, cobalt, vanadium, titanium, and lithium. For wastewater compliance, total mercury, alkyl mercury, total cadmium, total chromium, chromium(VI), total arsenic, total lead, and total nickel are designated priority pollutants with strict maximum discharge concentrations.
Testing Methods
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
ICP-MS is the premier technique for multi-element trace analysis, offering detection limits at the ng/L level, wide linear range, and simultaneous quantification of more than 60 elements. It is specified in GB/T 5750.6-2023 and HJ 700-2014, and is technically equivalent to the principles of ISO 17294-2. Internal standards, collision/reaction cell gases, and interference correction equations are applied to control polyatomic interferences in chloride- and carbon-rich matrices.
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)
ICP-OES provides robust multi-element determination at µg/L to mg/L levels with high salt tolerance, making it suitable for industrial wastewater, seawater dilutions, and process water. It is covered by HJ 766-2015 and aligns with ISO 11885. Spectral overlap is managed through alternative analytical lines and background correction.
Atomic Absorption Spectrometry (AAS)
Flame AAS (GB 7475-87 for copper, zinc, lead, and cadmium; GB 11911-89 for iron and manganese; GB 11912-89 for nickel) addresses mg/L-level analytes in relatively clean matrices. Graphite furnace AAS extends sensitivity to sub-µg/L levels for lead, cadmium, and other trace metals, while hydride generation AAS and cold vapor AAS (GB 7468-87) are classical approaches for arsenic, selenium, antimony, and mercury. The technique corresponds to ISO 15586 principles.
Atomic Fluorescence Spectrometry (AFS)
Hydride generation atomic fluorescence spectrometry is a distinctly mature and widely deployed Chinese national method for ultratrace mercury, arsenic, selenium, antimony, and bismuth, delivering sub-ng/L capability with simple operation and low operating cost. It is a core method family in GB/T 5750.6 and the HJ 694 procedure.
Ultraviolet-Visible Spectrophotometry
Colorimetric methods remain valid national standards for confirmatory and resource-limited testing: diphenylcarbazide spectrophotometry for chromium(VI) (GB 7467-87) and total chromium (GB 7466-87), silver diethyldithiocarbamate for arsenic (GB 7485-87), dithizone procedures for lead (GB 7470-87), cadmium (GB 7471-87), zinc (GB 7472-87), and mercury (GB 7469-87), and periodate oxidation for manganese (GB 11906-89).
Electrochemical and Rapid Screening Methods
Anodic stripping voltammetry achieves very low detection limits for lead, cadmium, copper, and zinc and is suited to field deployment, while portable X-ray fluorescence and colorimetric test kits serve as rapid on-site screening tools whose positive results must be confirmed by laboratory GB methods.
Sample Preparation and Quality Control
Samples for total metals are collected in acid-washed polyethylene or glass containers and acidified with high-purity nitric acid to pH below 2, with holding times typically up to 14 days; mercury samples require additional oxidant stabilization. Dissolved metals are filtered through 0.45 µm membranes, ideally on site, before acidification. Digestion by hot plate or microwave heating (following ISO 15587-type procedures) precedes total metal measurement. Quality control requirements include method blanks, laboratory control samples, certified reference materials, matrix spikes with 75–125% recovery targets, duplicate precision of relative deviation within 20%, calibration verification, and participation in interlaboratory proficiency schemes.
Applications
GB-based heavy metal testing in water supports a broad range of regulatory, industrial, and scientific objectives:
- Drinking water plant compliance, hygiene permit renewal, and network water quality verification under GB 5749-2022.
- National and local surface water and groundwater environmental monitoring, pollution census, and watershed risk assessment under GB 3838-2002 and GB/T 14848-2017.
- Industrial discharge supervision and environmental protection acceptance for electroplating, mining, smelting, battery, and chemical enterprises under GB 8978-1996 and sector-specific standards.
- Contaminated site investigation, remediation performance verification, and environmental liability assessment.
- Food processing, beverage production, aquaculture, and agricultural irrigation water safety evaluation.
- Supporting documentation for export products, environmental information disclosure, and ESG or sustainability reporting.
- Academic research, standard development, and method validation studies.
FAQ
What is the difference between total metals and dissolved metals?
Total metals are measured after acid digestion of the whole, unfiltered sample and include both dissolved species and metals bound to suspended particles; dissolved metals are measured in the filtrate passing a 0.45 µm membrane. Regulatory standards specify which fraction applies, so the sampling protocol must match the reporting requirement.
How should water samples be collected and preserved for heavy metal testing?
Use acid-walled containers, rinse them with sample where appropriate, acidify with high-purity nitric acid to pH below 2, and transport promptly to the laboratory. Mercury requires specialized stabilization, and hexavalent chromium must be preserved under alkaline conditions and analyzed quickly to prevent redox conversion.
Which analytical method is most suitable for trace-level heavy metals?
ICP-MS offers the lowest detection limits and the widest multi-element coverage, making it the preferred choice for drinking water compliance and ultratrace metals such as thallium and mercury. AFS is highly cost-effective for mercury, arsenic, selenium, and antimony, while ICP-OES and flame AAS are well suited to higher-concentration industrial matrices.
How do GB limits compare with international guidelines?
GB 5749-2022 limits for arsenic (0.01 mg/L), lead (0.01 mg/L), cadmium (0.005 mg/L), and chromium(VI) (0.05 mg/L) are broadly consistent with WHO drinking water guidelines and ISO-based national regulations, and GB analytical methods are technically harmonized with international reference procedures, supporting mutual recognition of data by accredited third-party laboratories.
What is the typical turnaround time for heavy metal testing?
Standard reporting is typically completed within five to ten working days after sample receipt, depending on the number of elements, the digestion scheme required, and whether urgent services are requested. Projects involving complex matrices or full GB/T 5750.6 method suites may require additional time for quality control validation.
How is data quality assured?
Accredited laboratories operate under ISO/IEC 17025 management systems, apply the full suite of blanks, spikes, duplicates, certified reference materials, and internal standards described above, and report results with stated measurement uncertainty, ensuring that reported concentrations are legally defensible against the applicable GB limit values.