Geochemical Factors Controlling the Mobilization of Arsenic at an Artificial Recharge Site, Clearwater, Florida

Aquifer storage and recovery and artificial recharge projects are common methods of developing and managing groundwater resources for future use by cities that face pressure to maintain sustainable supplies of water for growing populations. Such projects, however, are often accompanied by water‐quality problems that can be mitigated by careful attention to geological and geochemical factors that account for the occurrence and mobilization of contaminants such as arsenic in storage zones. Investigations of artificial recharge systems in Florida, for example, have identified oxidative dissolution of pyrites by treated injectate waters as the principal factor causing the mobilization of arsenic from the matrix of an aquifer. This paper describes major‐ion chemistry and associated reduction‐oxidation factors that account for the occurrence of arsenic in groundwater at an artificial recharge site under development by the City of Clearwater, Florida. The results of this investigation are fully consistent with those of previous studies. Of particular significance is the apparent sensitivity of arsenical sulfides to slight changes in the redox conditions under which those minerals are otherwise stable.