|ALLEN, AMY - University Of Guelph|
|KIEKE, BURNEY - Marshfield Clinic Research|
|DUNFIELD, KARI - University Of Guelph|
|PARKER, BETH - University Of Guelph|
Submitted to: Hydrogeology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2017
Publication Date: 4/6/2017
Publication URL: http://handle.nal.usda.gov/10113/5753401
Citation: Allen, A., Borchardt, M.A., Kieke, B., Dunfield, K., Parker, B. 2017. Virus occurrence in private and public wells in a fractured dolostone aquifer in Canada. Hydrogeology Journal. 25:1117-1136.
Interpretive Summary: While contamination of groundwater by pathogens from human and livestock sources is now widely recognized, questions remain on the conditions that lead to contamination, particularly for fractured rock aquifers. We examined the relationship between pathogen contamination and well construction characteristics and precipitation for municipal and private wells located in southern Ontario, Canada. The wells draw water from a fractured rock aquifer. Among the 118 samples analyzed, only 8% had measurable pathogens, but nearly half of the wells (45%) were pathogen-contaminated at least once during the study period. We found deeper wells had lower pathogen concentrations as did wells that had a long open interval between the bottom of the well casing and bottom of the well. Wells with the longest open intervals were the most likely to be pathogen contaminated. We summed the precipitation amounts during three time periods before the date a well was sampled and found higher precipitation during the latter two periods resulted in higher pathogen concentrations in wells. Our findings contribute to protecting public health by identifying well construction characteristics and precipitation patterns that lead to pathogen contamination of groundwater-supplied drinking water.
Technical Abstract: Groundwater samples collected during eight months from 22 wells completed in a regional fractured dolostone aquifer in the Guelph region of southern Ontario, Canada were analyzed for viruses and Campylobacter jejuni. Only 8% of the 118 samples exhibited viruses at extremely low concentrations; but of the 22 wells sampled, 10 (45%) were positive for human enteric viruses (polyomavirus, adenovirus A, and GII norovirus), including 5 of the 8 public supply wells (62.5%) and 5 of the 11 private wells (45%). Each virus-positive well had only one virus occurrence during the 8-month sampling campaign and only one virus strain was detected in each well. The probability of virus detection was positively associated with well open interval length. Virus concentration (in the wells that were virus-positive) was negatively associated with well depth and open interval length and positively associated with overburden thickness and the amount of precipitation 8 to 14 days and 15 to 21 days prior to the sampling date. The ephemeral nature of the virus detections and the low detection rate on a per sample basis were consistent with previous studies. The percent of virus-positive wells, however, was much higher than previous studies, but this is consistent with the fact that the hydrogeologic conditions of fractured bedrock aquifers are vulnerable to contamination.