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Arsenic Speciation and its Effect on Soil Cleanup Standards

INTRODUCTION Arsenic is an element that is widely distributed in the Earth’s crust and has been used for centuries both to kill and to cure. It has been found in at least 1014 of 1598 current or former sites on the U.S. Environmental Protection Agency’s (EPA’s) National Priorities List (NPL), and, as illustrated by Figure 1, arsenic has been detected at NPL sites in almost every state (ATSDR, 2000). Despite its frequent appearance, arsenic is not universally present in environmental media in the same form (i.e., chemical species), and the effects of arsenic exposure are directly related to its chemical form at the point of exposure. Inorganic arsenic is both odorless and tasteless, which has made it a poison of choice in both fact as well as fiction. It has been used for the treatment of leukemia, psoriasis, and chronic bronchial asthma and limited research suggests that arsenic also may be an essential nutrient in the human diet (ATSDR, 2000). Arsenic has been used in a variety of commercial products including pesticides and insecticides, feed additives and livestock dips, and in the manufacture of glass, electronics, metal alloys, dyes and soaps, and ceramics (Azcue and Nriagu, 1994). Arsenic also is used in the wood preservative known as CCA (chromated copper arsenate) for pressure treated lumber; this use accounts for approximately 90% of the arsenic currently produced (ATSDR, 2000). The potential toxicity resulting from the extensive use of pressure treated lumber in residential decks and play sets throughout the United States is undergoing intensive investigation.