Determination of the Priority Pollutant Metals – Regulations and Methodology

Importance of the Topic

The release and concentration of trace metals through industrial and municipal activities pose persistent risks to ecosystems and human health. Regulatory limits and reliable analytical methods are essential to monitor, control, and mitigate the impacts of metal pollutants in drinking water, industrial effluents, and waste streams.

Objectives and Study Overview

This application note reviews the framework of U.S. regulations governing priority pollutant metals and summarizes atomic absorption (AA) approaches recommended by the EPA to comply with drinking water, effluent discharge, and hazardous waste criteria. Key goals include outlining regulatory limits, detailing sample preparation and instrumentation, and illustrating how AA methods satisfy analytical requirements.

Methodology and Instrumentation

The analytical strategy centers on atomic absorption spectroscopy with variants selected by required detection limits and sample matrix:

• Flame AA for milligram per liter levels in secondary standards and less stringent effluents.
• Graphite furnace AA for sub-milligram per liter quantitation, especially near primary drinking water limits and NPDES permit thresholds.
• Hydride generation AA for sensitive determination of arsenic and selenium.
• Cold vapor AA for mercury analysis at ultra-trace levels.
• Chelation-extraction and coprecipitation techniques for selective separations (e.g., Cr(VI) vs. Cr(III)).

Sample handling protocols address dissolved, suspended, total, and extractable metal fractions, with filtration, acidification (pH <2), and controlled microwave or hot-plate digestion steps. Strict cleaning procedures for glassware and equipment, plus reagent blanks, prevent contamination. Quality controls follow EPA guidelines with daily calibration checks and periodic performance standards.

Main Results and Discussion

The note correlates regulatory metal limits with suitable AA methods:

• Primary drinking water: As (0.05 mg/L), Ba (1.0 mg/L), Cd (0.01 mg/L), Cr (0.05 mg/L), Pb (0.05 mg/L), Hg (0.002 mg/L), Se (0.01 mg/L), Ag (0.05 mg/L).
• Secondary drinking water: Cu (1.0 mg/L), Fe (0.3 mg/L), Mn (0.05 mg/L), Zn (5.0 mg/L).
• Effluent guidelines under Clean Water Act: NPDES permits set limits based on best practicable and best available technologies for up to 35 metals, including 13 priority pollutants.
• Hazardous waste EP toxicity thresholds: As (5 mg/L), Ba (100 mg/L), Cd (1 mg/L), Cr (5 mg/L), Pb (5 mg/L), Hg (0.2 mg/L), Se (1 mg/L), Ag (5 mg/L).

Discussion highlights the evolving regulatory landscape—new source performance standards, pretreatment requirements, and proposals to amend chromium speciation criteria—and emphasizes AA’s flexibility in meeting varied detection needs across matrices.

Benefits and Practical Applications

Atomic absorption offers:

• High selectivity and sensitivity across a wide concentration range.
• Established EPA-approved methods for regulatory compliance.
• Adaptability to different sample types (drinking water, effluents, sludges).
• Relatively rapid analysis with well-defined quality control protocols.

This enables laboratories to verify compliance with Safe Drinking Water Act, Clean Water Act, and RCRA requirements and to support industry in pollution control and environmental monitoring.

Future Trends and Potential Applications

Emerging directions include:

• Integration of speciation analysis (e.g., Cr(VI)/Cr(III)) for toxicity assessment.
• Adoption of inductively coupled plasma (ICP) methods as validated alternatives to AA.
• Development of automated sample preparation and on-line separation techniques to improve throughput.
• Enhanced data management systems tailored for regulatory reporting and real-time monitoring.

These trends aim to refine detection limits, reduce analysis time, and expand capabilities for routine and research applications.

Conclusion

Atomic absorption spectroscopy remains a cornerstone for quantifying priority pollutant metals under U.S. environmental regulations. By matching appropriate AA techniques to specified concentration ranges and sample matrices, laboratories can reliably demonstrate compliance, support pollution control technologies, and contribute to protecting public health and the environment.

Reference

1. US EPA, A Handbook of Key Federal Regulations and Criteria for Multimedia Environmental Control, EPA-600/7-79-175 (1979).
2. US EPA, “Drinking Water Regulations–Amendments,” Federal Register 44(140):42250 (1979).
3. US EPA, Federal Register 44(247):75927 (1979).
4. F. Cross, “Update: Effluent Limitations Guidelines,” Pollution Engineering, p. 41 (Sept. 1980).
5. D. Hanson, “Proposed Changes to Clean Water Act Debated,” Chemical & Engineering News 60(32):14 (1982).
6. US EPA, Test Methods for Evaluation of Solid Waste, Physical/Chemical Methods, SW-846 (1980).
7. US EPA, “Hazardous Waste Management Systems,” Federal Register 45(212):72029 (1979).
8. US EPA, Methods for Chemical Analysis of Water and Wastes, EPA-600/4-79-020 (1979).
9. J. Kopp, T. Martin, “Trace Elements–Methodology, and Legislation,” ASTM Standardization News, p. 18 (Feb. 1983).