Dynamics of Arsenic Concentration and Speciation in Wisconsin Private Drinking Water Wells

As a naturally occurring element, Arsenic (As) in drinking water can cause skin, bladder, lung, liver, colon, and kidney cancer as well as various other health issues such as blood vessel damage, high blood pressure, nerve damage, anemia, stomach upsets, diabetes, and skin changes (Wisconsin Department of Natural Resources, 2017).

Arsenic is commonly detected in Wisconsin’s private wells. In the Fox River Valley region, >18% of private water-supply wells exceed the 10 ug L-1 (ppb) drinking water standard (Thornburg and Sahai, 2004). Extensive water sampling studies carried out in Outagamie and Winnebago Counties showed that 3% of drinking water wells had As concentrations higher than 50 ppb and 20% of well had As concentrations higher than 10 ppb (Riewe, 2015).

Recent well water testing results showed that As contamination is also prevalent in private wells located in Southeastern Wisconsin and many other parts of the state (Gotkowitz, 2000; Gotkowitz et al., 2008; Gotkowitz et al., 2004; Ozaukee County Public Health Department, 2011). According to the Ozaukee County Public Health Department, 24 out of 167 wells tested between 4/2/2009 and 6/2/2009 had As concentrations higher than 10 ppb (Benson, 2009). In the township of Cedarburg, where 70 wells were tested, 20 wells (28.6%) exceeded the EPA standard (Benson, 2009). As a result, As testing is now included in well water testing contingency for real estate transfer.

Recent survey performed by the PIs indicate that the reported well water As levels could significantly underestimate the actual As level that the well users may be exposed to because it is common practice to flush the well for more than 1 hour before the water sample is collected. In addition, our preliminary results suggested that along with well pumping/flushing, as the total As concentration usually drops, As speciation (e.g., percentage of As(III) and As(V)) will also change significantly. It is well known that the uncharged nature of As(III) under ambient pH conditions makes it extremely difficult to remove As(III) from drinking water even using reverse osmosis (RO) systems (Akin et al., 2011; George et al., 2006; Jiang et al., 2013; Walker et al., 2008). For instance, Walker et al. (2008) reported that while >95% of As(V) can be removed through RO, the removal efficiency was generally <45% when more than 50% of the As exists as As(III).
A better understanding of As concentration and speciation dynamics in Wisconsin’s private drinking water wells is critical for the better assessment of long term exposure health risks and the improved selection, design and implementation of different water treatment techniques (Wisconsin Department of Natural Resources, 2017). The primary goal of this research is to fill this knowledge gap through quantifying the dynamics of total As, As(III) and As(V) under normal pumping/usage conditions.