Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX7. CHAPTER 7 ANNEX - ENVIRONMENTAL
EFFECTS OF LEAD
AX7.1 TERRESTRIAL ECOSYSTEMS
AX7.1.1 Methodologies Used in Terrestrial Ecosystems Research
The distribution of Pb throughout the terrestrial ecosystem, via aerial deposition, has been
discussed throughout this document. Its further impacts on soil, sediment, and water provide
numerous pathways that may promote unacceptable risk to all levels of biota. Stable isotopes of
Pb have been found useful in identifying sources and apportionment to various sources. One of
the key factors affecting assessment of risk is an understanding, and perhaps quantification, of
bioavailability. Therefore, the bioavailability of Pb is a key issue to the development of
NAAQS. However, the discussion of all methods used in characterizing bioavailability is
beyond the scope of this chapter. The following topics are discussed in this chapter.
• Lead Isotopes and Apportionment
• Methodologies to determine Pb speciation
• Lead and the Biotic Ligand Model (BLM)
• In situ methods to reduce Pb bioavailability
AX7.1.1.1 Lead Isotopes and Apportionment
Determination of the extent of Pb contamination from an individual source(s) and its
impact are of primary importance in risk assessment. The identification of exposure pathway(s)
is fundamental to the risk analysis and critical in the planning of remediation scenarios.
Although societies have been consuming Pb for nearly 9,000 years, production of Pb in
the United States peaked in 1910 and 1972, at approximately 750 and 620 kt/year, respectively
(Rabinowitz, 2005). The diversity of potential Pb sources (fossil fuel burning, paint pigments,
gasoline additives, solders, ceramics, batteries) and associated production facilities (mining,
milling, smelting-refining) make fingerprinting of sources difficult. (See Chapter 2 and its
Annex for additional information on sources.) Therefore, dealing with multiple sources (point
and nonpoint), a reliable and specific fingerprinting technique is required. It has been well
established (Sturges and Barrie, 1987; Rabinowitz, 1995) that the stable isotope composition of
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