ABSTRACT
Arsenic-rich water found in arid and semi-arid environments is commonly attributed to evaporative concentration, and desorption of adsorbed arsenic in response to high pH and competing anions (Smedley & Kinniburgh 2002). These processes are considered at least partly responsible for high dissolved arsenic contents in portions of North America, Asia, and South America. In addition to the noted enrichment in water, evaporative environments can also precipitate arsenic-rich ephemeral salts (Reheis 1997). Such surficial salts provide a source of arsenic during runoff-events and to dust transported by wind. An incompletely investigated aspect of arsenic in these environments is the distribution of arsenic in the vadose zone where subsurface evaporation can result in accumulation of labile arsenic (Breit et al. 2010).
