Heavy Metal Determination in Water Under Chinese National Standards (GB): Methods, Limits, and Compl

Heavy metal contamination in water poses serious risks to human health and aquatic ecosystems, making the accurate determination of metals such as lead, cadmium, mercury, arsenic, and chromium essential for regulatory compliance. This article explains how heavy metals in water are measured under the Chinese national standards (GB) framework, covering applicable water matrices, regulated analytes and limit values, analytical techniques such as ICP-MS, ICP-OES, AAS, and AFS, and practical guidance on sampling, preservation, and quality control. It is intended for environmental engineers, water quality managers, and laboratory professionals seeking GB-compliant heavy metal testing of water.

Technical Overview

Heavy metals are metallic elements with relatively high densities that persist in the environment, bioaccumulate in the food chain, and exhibit toxicity even at trace concentrations. In aquatic systems, typical anthropogenic sources include mining and smelting operations, electroplating and metal finishing, battery manufacturing, tanneries, pesticide and fertilizer use, and municipal or industrial wastewater discharges. Because metals such as lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), and hexavalent chromium (Cr(VI)) are toxic, non-biodegradable, and cumulative in living organisms, Chinese national standards (GB) establish strict limit values and standardized analytical procedures for their determination in water.

The Chinese regulatory framework for water quality is structured around four principal product and environmental quality standards: GB 5749-2022 for drinking water quality, GB 3838-2002 for surface water environmental quality, GB/T 14848-2017 for groundwater quality, GB 3097-1997 for seawater quality, and GB 8978-1996 for the integrated discharge standard of wastewater. Supporting these limit-setting standards is a family of measurement standards that specify the instrumental and chemical procedures used for quantification, including the GB/T 5750.6-2023 standard examination methods for drinking water (metal indicators), GB/T 7475-1987 for copper, zinc, lead, and cadmium by atomic absorption spectrometry, GB 7466-87 and GB 7467-87 for total chromium and hexavalent chromium, and the environmental protection industry standards HJ 700-2014 (65 elements by ICP-MS), HJ 776-2015 (32 elements by ICP-OES), and HJ 694-2014 (mercury, arsenic, selenium, bismuth, and antimony by atomic fluorescence spectrometry).

Modern GB heavy metal determination is performed at trace and ultra-trace levels, with reporting limits typically in the range of micrograms per liter (µg/L) or lower for toxic elements. Accredited third-party laboratories and in-house environmental laboratories carrying national metrology and laboratory accreditation conduct these tests under documented quality systems, applying method validation, certified reference materials, and full procedural blanks to ensure data reliability and legal defensibility.

Testing Samples

Drinking Water and Packaged Water

Tap water, finished water from treatment plants, terminal water at the point of use, and packaged or bottled water are tested against GB 5749-2022. This standard regulates more than a dozen metallic indicators, including arsenic, cadmium, chromium (hexavalent), lead, mercury, selenium, aluminum, antimony, barium, beryllium, boron, molybdenum, nickel, silver, thallium, copper, zinc, iron, and manganese, with analytical procedures specified in the GB/T 5750.6-2023 series.

Surface Water

Rivers, lakes, reservoirs, and canals are classified into functional zones under GB 3838-2002, each with its own metal limit values for parameters such as mercury, cadmium, chromium (hexavalent), lead, arsenic, selenium, copper, zinc, fluoride-related metals, iron, and manganese. Routine surveillance of surface water bodies relies heavily on multi-element GB and HJ instrumental methods such as ICP-MS and ICP-OES.

Groundwater

Well water, monitoring-well samples, and aquifer water are evaluated under GB/T 14848-2017, which defines five quality classes. Groundwater assessments around industrial sites, landfills, mining areas, and agricultural regions commonly target lead, cadmium, arsenic, mercury, hexavalent chromium, nickel, iron, and manganese to identify contamination plumes and guide remediation.

Industrial Wastewater and Effluent

Discharges from electroplating, metal processing, mining, chemical, battery, tannery, and electronics manufacturing are regulated under GB 8978-1996 and industry-specific discharge standards. Total mercury, alkyl mercury, total cadmium, total chromium, hexavalent chromium, total lead, total nickel, and total arsenic are classic priority pollutants monitored at discharge outfalls for permit compliance.

Seawater, Estuarine, and Process Water

Marine and brackish waters are assessed under GB 3097-1997, requiring matrix-matched calibration for high-salt samples. Process water, cooling water, boiler feed water, and purified water used in food, beverage, pharmaceutical, and electronics production are also screened for metal contamination to protect product quality and equipment integrity.

Testing Items

The scope of GB heavy metal determination in water covers priority toxic metals, secondary regulated metals, and general physicochemical metal indicators. Core regulated elements and representative drinking water limit values under GB 5749-2022 include:

• Arsenic (As) — 0.01 mg/L, determined by hydride generation atomic fluorescence or ICP-MS
• Cadmium (Cd) — 0.005 mg/L, determined by graphite furnace AAS or ICP-MS
• Chromium, hexavalent (Cr(VI)) — 0.05 mg/L, determined by diphenylcarbazide spectrophotometry (GB 7467-87)
• Lead (Pb) — 0.01 mg/L, determined by graphite furnace AAS, ICP-MS, or dithizone spectrophotometry
• Mercury (Hg) — 0.001 mg/L, determined by cold vapor atomic fluorescence or ICP-MS
• Selenium (Se) — 0.01 mg/L, determined by atomic fluorescence spectrometry
• Antimony (Sb) — 0.005 mg/L; barium (Ba) — 0.7 mg/L; beryllium (Be) — 0.002 mg/L; thallium (Tl) — 0.0001 mg/L
• Nickel (Ni) — 0.02 mg/L; molybdenum (Mo) — 0.07 mg/L; silver (Ag) — 0.05 mg/L
• Copper (Cu) — 1.0 mg/L; zinc (Zn) — 1.0 mg/L; aluminum (Al) — 0.2 mg/L
• Iron (Fe) — 0.3 mg/L; manganese (Mn) — 0.1 mg/L; boron (B) — 0.5 mg/L

In addition to total element concentrations, testing may distinguish dissolved metals (filtration through a 0.45 µm membrane) from total metals (acid digestion of the unfiltered sample), and may include chemical speciation such as the separation of hexavalent chromium from trivalent chromium, since toxicity and regulatory limits differ significantly between species.

Testing Methods

Sample Collection and Pretreatment

Samples for metal analysis are collected in acid-washed polyethylene or glass bottles following HJ 493-2009 for preservation and handling. For total recoverable metals, the sample is acidified with nitric acid to pH below 2 at the time of collection and digested with nitric acid (or nitric-perchloric acid for difficult matrices) before instrumental measurement. For dissolved metals, the sample is filtered through a 0.45 µm membrane prior to acidification. Mercury samples require the addition of a stabilizing oxidant to prevent loss by volatilization or adsorption, and hexavalent chromium samples must be buffered to avoid redox interconversion before analysis.

Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

ICP-MS under HJ 700-2014 and the GB/T 5750.6-2023 series is the most powerful multi-element technique, capable of quantifying more than 60 elements in a single run with detection limits at the nanogram-per-liter level. Internal standards, collision-reaction cell technology, and interference corrections are applied to remove polyatomic interferences, making the method suitable for lead, cadmium, arsenic, mercury, thallium, beryllium, uranium, and a broad suite of trace metals in all water matrices.

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

HJ 776-2015 specifies the determination of 32 elements by ICP-AES/ICP-OES. The technique offers wide linear ranges, high throughput, and robust tolerance of total dissolved solids, which makes it well suited for copper, zinc, iron, manganese, aluminum, barium, and boron in drinking water, surface water, and wastewater at milligram-per-liter to low microgram-per-liter concentrations.

Atomic Absorption Spectrometry (AAS)

GB/T 7475-1987 covers the determination of copper, zinc, lead, and cadmium by flame atomic absorption, with chelation-extraction preconcentration (APDC-MIBK) used for lead and cadmium to reach the low microgram-per-liter range. Graphite furnace atomic absorption spectrometry (GFAAS), specified in the GB/T 5750.6 series, provides superior sensitivity for trace lead, cadmium, nickel, antimony, and thallium through electrothermal atomization of microliter sample volumes.

Atomic Fluorescence Spectrometry (AFS)

HJ 694-2014 specifies the determination of mercury, arsenic, selenium, bismuth, and antimony by atomic fluorescence spectrometry. Hydride generation and cold vapor techniques physically separate the analyte from the sample matrix, delivering excellent sensitivity and low background for the hydride-forming and volatile metals, and AFS remains a workhorse method in Chinese laboratories for arsenic, selenium, and mercury in water.

UV-Visible Spectrophotometry

Classical colorimetric GB methods remain authoritative for specific species: hexavalent chromium is determined by reaction with diphenylcarbazide under GB 7467-87, total chromium by oxidation followed by the same color reaction under GB 7466-87, and lead by the dithizone method. These methods require minimal instrumentation and serve as reliable references, particularly for hexavalent chromium speciation.

Quality Assurance and Data Reporting

Each analytical batch includes field and reagent blanks, duplicate samples, matrix spikes with recovery acceptance criteria (typically 80–120 percent), and certified reference materials. Calibration curves are verified with independent check standards, and results are reported with method detection limits, measurement uncertainty where required, and a clear statement of conformity against the applicable GB limit values.

Applications

GB-compliant heavy metal determination of water supports a wide range of regulatory, industrial, and scientific purposes:

• Drinking water safety monitoring by water utilities and health authorities against GB 5749-2022
• Wastewater discharge permit compliance and outfall supervision under GB 8978-1996 and sector-specific discharge standards
• Environmental quality assessment of rivers, lakes, reservoirs, and groundwater under GB 3838-2002 and GB/T 14848-2017
• Environmental impact assessments, construction project acceptance, and post-remediation verification for contaminated sites
• Process water, purified water, and ultrapure water verification in food, beverage, pharmaceutical, and electronics manufacturing
• Aquaculture and irrigation water safety evaluation for agricultural and food production chains
• Academic research, pollution source apportionment, geochemical surveys, and environmental forensic investigations

Test reports issued by accredited third-party laboratories on this basis are accepted by environmental regulators, customs authorities, certification bodies, and international buyers as objective evidence of water quality compliance.

FAQ

What is the difference between total metals and dissolved metals?

Total metals are measured after acid digestion of the whole, unfiltered sample and represent the sum of dissolved, colloidal, and particle-bound forms. Dissolved metals are measured in the filtrate obtained by passing the sample through a 0.45 µm membrane before acidification. Regulatory standards specify which form applies: drinking water limits generally refer to total concentrations, while some surface water and ecological criteria use the dissolved fraction.

Which GB standards specify the analytical methods?

For drinking water, the GB/T 5750.6-2023 series defines the reference methods for metal indicators. For environmental waters and wastewater, the GB 7466/7467/7475 series and the HJ instrumental standards such as HJ 700-2014 (ICP-MS), HJ 776-2015 (ICP-OES), and HJ 694-2014 (AFS) are the applicable method standards. The choice depends on the water matrix, the elements of interest, and the limit values to be verified.

How should water samples for heavy metal analysis be preserved?

Samples should be collected in pre-cleaned polyethylene containers, acidified with high-purity nitric acid to pH below 2, stored at low temperature, and analyzed within the holding time specified in HJ 493-2009 — typically 14 days for most metals, with shorter holding times for mercury and hexavalent chromium. Field blanks and preservative blanks are recommended for trace-level work.

What detection limits can be achieved?

With ICP-MS, method detection limits for most elements reach 0.01–1 µg/L or better, sufficient to verify the strictest GB 5749-2022 limits such as thallium at 0.1 µg/L and mercury at 1 µg/L. Graphite furnace AAS and atomic fluorescence achieve comparable performance for their target elements, while flame AAS and ICP-OES cover higher-concentration parameters.

How do GB methods relate to international standards?

The underlying analytical techniques are internationally harmonized: GB and HJ ICP-MS, ICP-OES, and AAS procedures are technically aligned with the corresponding ISO and ASTM water analysis methods, differing mainly in validation requirements, QC criteria, and reporting conventions. Accredited third-party laboratories can typically issue test reports referencing GB methods or, where required, equivalent ISO or ASTM methods.

What accreditation should the testing laboratory hold?

For data to be accepted by Chinese regulators, the laboratory should operate under a recognized laboratory accreditation scheme with the relevant GB/HJ metal methods within its accredited scope. Clients should verify the laboratory's method scope, current accreditation status, and reporting format before commissioning testing to ensure legal validity of the results.