HEALTH, TRACE ELEMENTS, AND HYDROGEOLOGY: WHAT ARE THE RESEARCH TOPICS?

Groundwater has historically been considered preferable to surface water as an untreated source for drinking water due to its natural filtration by the aquifer media. Even early humans appear to have been aware of the quality differences between springs and surface water. However, as our ability to analyze and understand water quality increased, we discovered that well water and even clear spring water may contain trace elements of concern. The natural solvent properties of water result in dissolution of a portion of the aquifer media by groundwater. Sometimes the trace elements found dissolved in groundwater are healthy and sometimes they present a risk to human health. Selecting quality water sources and managing water quality with regard to trace elements present future educational and research challenges. The trend toward exploring for brackish groundwater supplies highlights one of these future challenges. This presentation looks at two trace elements of concern: naturally occurring arsenic (As) in deep aquifers, and naturally occurring radon (Rn) with regard to media contact and residence times.

Decreasing the EPA drinking water standard for As from 50 µg/l to 10 µg/l affected the water supply from deep Trinity aquifer wells in central Texas. Initial studies indicate possible sources, solutions, and research needs; but data are scarce, public education is in its infancy, and opinions are highly variable. Similarly, although Rn in homes is a known air quality concern, much less work has been conducted on Rn in groundwater. Research using a Rad7 detector is rapidly uncovering how little we know about the occurrence and behavior of Rn in major aquifers. Examples from the northern segment of the Edwards Balcones Fault Zone aquifer indicate variable concentrations among wells and springs that are difficult to explain. Present knowledge and research strategies will be presented.