HYDROGEOLOGIC ASSESSMENT OF GROUNDWATER UNDER DIRECT INFLUENCE OF SURFACE WATER

摘要

Cryptosporidium parvum is a waterborne pathogen known to reside in surface waters throughout the U.S. Recent Cryptosporidiosis outbreaks from drinking water wells are the result of this contaminant transporting between surface and ground water systems. With a high resistance to typical groundwater treatment procedures, aquifer infiltration by Cryptosporidium poses a serious threat. Since groundwater wells are the main source of drinking water supply in the State of Florida, understanding certain factors that affect the passage of C. parvum into the subsurface would prevent future outbreaks. This study examines Florida's surficial geology, recharge capacity, and possible sinkhole development as they influence the risk of groundwater contamination. Microscopic Particulate Analysis (MPA) sampling was performed on 719 public water systems distributed throughout Florida. Sampling results defined the wells as having high, moderate, or low risk to surface water influence. The results of this study indicated that the hydrogeology of an area tends to influence the MPA Risk Index (Rl) of a well. Areas of higher aquifer recharge generally contained the majority of the moderate and high-risk wells. Surficial geologic regions of shelly sand and clay, limestone, and clayey sand contained over 80% of the high-risk wells. The results also suggested that areas prone to sinkhole development are likely to contain wells with positive Rl.