Journal de géologie et géophysique
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Redistribution of Arsenic in Soils by Natural Hydrogeologic Processes

Kevin Doherty*, Rudolph Hon

Your health depends on where you live as much as your diet and genes. All bodily processes depend on the presence of natural metals/minerals in the soil which must come from your diet. Some minor metals/minerals are iron, zinc, manganese, iodine, fluoride, chromium, cobalt, selenium, molybdenum, silicon, and vanadium. Other metals and minerals in soils are potentially toxic. Understanding the natural variations of potentially toxic elements in soils and groundwater is critical for one’s health. Arsenic is a common metal/mineral and is present in soil, water, food, and air. The top 4 common foods that contain arsenic are rice, apple and grape juice, protein shakes and powders, and chicken. Consumer Reports published the following; measurable amounts of arsenic were found in virtually every one of the 60 varieties of rice tested, roughly 10 percent of apple and grape juice samples contained arsenic levels that exceeded the federal drinking water standard of 10 ppb, three of 15 protein powders and drinks contained arsenic, exceeding the limits, and arsenic in chicken feed contained toxic levels and was banned in 2010. In 1998 the United States Environmental Protection Agency (USEPA) identified arsenic as a “known” human carcinogen based on occupational and drinking water exposure. In 2005, the EPA completed the National Human Exposure Assessment Survey and prepared a geochemical map for arsenic in soil throughout the United States that shows a number of regions contain elevated concentrations. The EPA’s soil screening level is 0.4 ppm which corresponds to a cancer risk level of 1 in 1,000,000 for ingesting arsenic. The increasing risk of cancer due to low-level arsenic exposure has prompted the author in this paper to examine the factors controlling the origin and distribution of arsenic in the environment and the ways in which arsenic may be mobilized. This paper reports on arsenic in New England, specifically a detailed study of one geographic area in central Massachusetts that has elevated arsenic levels in soils. The average results of 177 samples from 0-10' depth showed that the concentration of As was 68.72 mg kg-1. The presence of elevated levels of arsenic (As) in a zone that traverses N-S across Central Massachusetts had been periodically noted and reported. Suspected sources included the past applications of lead arsenate in orchards, industrial applications in metal and leather processing facilities, and/or from natural sources. These arsenic concentrations appear to be unrelated to commercial or industrial processes and are natural in origin. The distribution of As “hot spots” appears related to the fluvial and lacustrine depositional environment and is likely due to the bio-geoaccumulation of As throughout its depositional geologic history. Knowledge of the underlying bedrock geochemistry may aid in the prediction of elevated arsenic concentrations in overburdened soils.