Are VOCs likely to co-occur in samples from domestic wells or public wells?
Volatile organic compounds (VOCs) co-occurred in some samples; however, mixtures occurred less frequently in domestic well samples (3.9 percent) than in public well samples (13.4 percent) at concentrations equal to or greater than 0.2 microgram per liter (μg/L). Furthermore, a single VOC occurred more frequently than multiple VOCs in domestic well samples, whereas detections of single VOCs and multiple VOCs were about equal in public well samples. Solvents, trihalomethanes (THMs), and the gasoline oxygenate methyl tert-butyl ether (MTBE) comprised the 10 most frequently detected VOCs co-occurring in domestic well samples. In contrast, all but 1 of the 10 most frequently occurring VOC mixtures in public well samples were THMs; the exception was the solvent mixture of perchloroethene (PCE) and trichloroethene (TCE). More information on this topic is included in USGS Circular 1292, Sidebar 24.
