Determination of Heavy Metal Pollutants in Water: Standards, Methods, and Applications

Determination of heavy metal pollutants in water is essential for safeguarding drinking water safety, verifying industrial discharge compliance, and protecting aquatic ecosystems from persistent toxic contamination. This technical guide covers the key heavy metal parameters, internationally recognized analytical techniques such as ICP-MS, ICP-OES, AAS, and AFS, the applicable ISO, GB, ASTM, and EN standards, as well as sample handling, quality control, and typical application scenarios.

Technical Overview

Heavy metals are among the most closely monitored pollutants in water because of their persistence, non-biodegradability, and capacity to bioaccumulate in the food chain. Elements such as lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), hexavalent chromium (Cr(VI)), nickel (Ni), and antimony (Sb) can cause adverse health effects even at microgram-per-liter concentrations, making accurate trace-level determination critical for public health and environmental protection.

Heavy metals enter water bodies through multiple pathways, including industrial effluent from electroplating, mining, metallurgy, battery manufacturing, tanneries, and chemical plants, as well as agricultural runoff, corrosion of distribution pipes, and atmospheric deposition. Determination of heavy metal pollutants in water therefore involves a complete analytical workflow: representative sampling, proper preservation and pretreatment, instrument-based quantification, and rigorous quality control. Accredited third-party laboratories typically perform these analyses under ISO/IEC 17025 quality management systems, applying standardized methods published by ISO, GB, ASTM, EN, and JIS.

Testing Samples

Drinking Water and Tap Water

Finished drinking water, tap water at the point of use, bottled water, and source water are tested against drinking water quality standards such as GB 5749-2022, WHO guideline values, and EN drinking water directives. Particular attention is given to lead and copper leaching from plumbing systems and to arsenic in groundwater-derived supplies.

Surface Water

Rivers, lakes, reservoirs, and canals are classified according to environmental quality standards such as GB 3838-2002, which defines five functional water classes with progressively stricter limits for metals including mercury, cadmium, lead, chromium(VI), arsenic, copper, zinc, and selenium.

Groundwater

Well water, monitoring-well samples, and karst or phreatic zone water are evaluated under standards such as GB/T 14848-2017. Groundwater often accumulates geogenic arsenic, manganese, iron, and nickel, as well as anthropogenic plumes from landfills and industrial sites.

Industrial Wastewater and Effluent

Discharges from electroplating, metal finishing, mining, smelting, electronics, pigment and dye production, and chemical manufacturing are tested for compliance with discharge standards such as GB 8978 and sector-specific limits. Total and speciated metals (for example Cr(VI) versus total chromium) may both be regulated.

Seawater, Estuarine Water, and Other Matrices

Marine and brackish waters, rainwater, leachates, aquaculture water, irrigation water, cooling water, and ultrapure process water can also be characterized, with matrix-adapted methods and salinity-corrected calibration used where appropriate.

Testing Items

Commonly determined heavy metal parameters in water include the following:

• Priority toxic metals: lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), hexavalent chromium (Cr(VI)), thallium (Tl), beryllium (Be), and antimony (Sb)
• Regulated common metals: copper (Cu), zinc (Zn), nickel (Ni), total chromium (Cr), manganese (Mn), iron (Fe), and aluminum (Al)
• Additional trace elements: selenium (Se), barium (Ba), silver (Ag), molybdenum (Mo), cobalt (Co), vanadium (V), tin (Sn), titanium (Ti), and uranium (U)
• Speciation analysis: Cr(III)/Cr(VI), inorganic arsenic species (As(III)/As(V)), and methylmercury where toxicity depends on chemical form
• Fractionation: dissolved metals (0.45 µm filtered) versus total recoverable or total metals (unfiltered, digested)

For reference, GB 5749-2022 sets drinking water limits of 0.01 mg/L for lead, 0.005 mg/L for cadmium, 0.001 mg/L for mercury, 0.01 mg/L for arsenic, and 0.05 mg/L for hexavalent chromium, which places strict demands on method detection limits.

Testing Methods

Method selection depends on target elements, required detection limits, sample matrix, and throughput. The principal techniques and their typical standards are summarized below.

Sample Collection, Preservation, and Pretreatment

Samples are collected in acid-washed polyethylene or glass containers. For dissolved metals, samples are filtered in the field through a 0.45 µm membrane; for total metals, unfiltered samples are digested with nitric acid. Samples are generally acidified with ultrapure nitric acid to pH below 2 and stored at approximately 4 °C. Acidified metal samples are typically analyzed within six months, mercury within 28 days, and hexavalent chromium as soon as possible (commonly within 24 hours or preserved according to the method) to avoid redox interconversion.

Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

ICP-MS is the preferred technique for ultra-trace multi-element determination, achieving detection limits from ng/L to low µg/L levels across most of the periodic table in a single run. It is the basis of methods such as ISO 17294-2, ASTM D5673, and the ICP-MS procedures in the GB/T 5750.6 drinking water examination series. Internal standards, collision/reaction cells, and interference corrections ensure accuracy in complex matrices.

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

ICP-OES offers robust multi-element capability at trace to mg/L concentrations and is well suited to high-throughput screening and wastewater with elevated metal loads. Representative standards include ISO 11885 and ASTM D1976, along with corresponding GB/T 5750.6 procedures.

Atomic Absorption Spectrometry (AAS)

Flame AAS (FAAS) suits metals at mg/L levels such as iron, manganese, copper, and zinc, while graphite furnace AAS (GFAAS) provides single-element trace determination down to sub-µg/L levels for lead, cadmium, and others. Cold vapor AAS is the classical approach for mercury, standardized in ISO 12846. Graphite furnace procedures are covered by ISO 15586 and related GB methods.

Atomic Fluorescence Spectrometry (AFS)

Hydride generation atomic fluorescence spectrometry delivers excellent sensitivity and low background for hydride-forming elements, particularly arsenic, selenium, antimony, and mercury, and is widely adopted in the GB/T 5750.6 series and related environmental standards.

Spectrophotometry and Other Techniques

UV-visible spectrophotometry with diphenylcarbazide colorimetry remains a standard method for hexavalent chromium (for example ISO 11083 and GB 7467). Anodic stripping voltammetry (ASV) provides ultra-sensitive on-site or laboratory determination of lead, cadmium, copper, and zinc, while portable XRF and field test kits serve as rapid screening tools ahead of confirmatory laboratory analysis.

Quality Control and Data Integrity

Reliable results depend on method blanks, laboratory control samples, matrix spikes, duplicate analyses, certified reference materials, multi-point calibration with independent verification standards, and internal standards for ICP-MS. Reporting should state results together with method detection limits, measurement uncertainty, and clearly defined sample fractions.

Applications

• Drinking water safety: verification of treatment performance, distribution-system corrosion control (lead, copper), and compliance with GB 5749, WHO guidelines, and EN directives
• Discharge compliance: periodic and regulatory monitoring of industrial effluent against GB 8978 and sector-specific emission standards
• Environmental monitoring: routine surveillance of rivers, lakes, reservoirs, groundwater, and marine waters under national monitoring programs
• Site investigation and remediation: baseline surveys, risk assessment, and post-remediation verification at contaminated and former industrial sites
• Environmental impact assessment: water quality data supporting project approvals and construction-phase monitoring
• Agriculture and aquaculture: irrigation water and pond water evaluation for cadmium, arsenic, mercury, and copper risks
• Industrial process control: cooling water, boiler water, and ultrapure water verification in electronics, pharmaceutical, food, and beverage production
• Research and litigation support: trace metal datasets for scientific studies, insurance claims, and environmental disputes

FAQ

What is the difference between dissolved and total metals?

Dissolved metals are determined after field filtration through a 0.45 µm membrane and represent the bioavailable fraction, whereas total metals are measured on unfiltered, acid-digested samples and include both particulate and dissolved forms. Regulatory programs specify which fraction applies.

What detection limits can be achieved?

ICP-MS typically reaches 0.01–1 µg/L for most elements, AFS achieves 0.01–0.1 µg/L for arsenic, selenium, antimony, and mercury, GFAAS reaches roughly 0.1–5 µg/L, and ICP-OES and FAAS operate in the low µg/L to mg/L range. Detection limits must always be below the applicable regulatory limit.

How should samples be preserved?

Most metal samples are acidified with ultrapure nitric acid to pH below 2 and refrigerated. Mercury requires dedicated containers and shorter holding times, while hexavalent chromium must be analyzed quickly or preserved according to the specific method to prevent interconversion with Cr(III).

Which standard applies to my sample?

The applicable standard depends on the water type: GB 5749 for drinking water, GB 3838 for surface water, GB/T 14848 for groundwater, GB 8978 for wastewater discharge, with ISO, ASTM, EN, and JIS methods available for international projects. Accredited third-party laboratories can confirm the correct pairing of product standard and analytical method.

How long does the analysis take?

After sample receipt and pretreatment, routine multi-element determination by ICP-MS or ICP-OES is typically completed within five to ten working days; speciation analyses such as Cr(VI) or arsenic species may require additional method development time.

Can hexavalent chromium be measured separately from total chromium?

Yes. Hexavalent chromium is determined specifically by diphenylcarbazide spectrophotometry or ion chromatography with post-column derivatization, while total chromium is measured after digestion by ICP-OES, ICP-MS, or AAS. Reporting both values allows assessment of chromium speciation and toxicity.