Abstract
In recent years, California has experienced decreasing water supplies and increasing frequency of wildfires due to drought and climate change. Despite the importance of groundwater quality to California’s water supplies, there have been few studies which examine the effects of wildfires on groundwater quality in California. State and federal agencies have recognized PFAS such as PFOA and PFOS as emerging constituents of concern due to its historical prevalence in many common household products and documented adverse health effects. Due to the prevalence of PFOA, PFOS, and precursor chemicals to PFOA and PFOS in common materials, this study hypothesizes that the runoff of ashes from wildfire burn areas could be a potential pathway of PFOA or PFOS into the groundwater. This project analyzes the effect of eight California wildfires in 2019 and 2020 on PFOA and PFOS concentrations in downstream groundwater wells. Publicly available sampling data was analyzed in R to determine if there was a statistically significant change in the PFOA and PFOS concentrations in the groundwater following these wildfires. Additionally, the individual wells were also analyzed for trends that may have been indicative of PFOA and PFOS contamination from the burn sites.
Ultimately, this project did not find a conclusive relationship linking wildfires to changes in PFOA and PFOS concentrations in the groundwater. Out of the eight study areas that were analyzed, there was a statistically significant increase in concentration at two study areas, a statistically significant decrease in concentration at one study area, and neither a statistically significant increase nor decrease in concentration at five areas. Additionally, a relationship between the area of a fire and the magnitude of the change in concentrations was unable to be established. The lack of conclusive trends were attributed to the lack of historical sampling data, the small number of study areas, and the short time period that was studied. However, while the results were inconclusive, the results did not rule out fire burn areas from being a source of PFOA and PFOS. Factors such as California’s lack of precipitation may be causing a delay in the contaminants from wildfire ash reaching the groundwater. While this study did not yield conclusive results about the relationship of wildfires to PFOA and PFOS concentrations in the groundwater, it highlights the need for future studies so that the effect of wildfires on groundwater quality is better understood.