Predicting changes to disinfectant by-products in treated water impacted by wildfires in California

Current MSc Environmental Science graduate student Bryson Patterson is using machine learning to build a model that predicts variables that influence water quality after wildfires. Read his project summary:

Wildfires are known to increase the transportation of sediment, metals, nutrients, and other contaminants downstream into receiving waters. Many studies have focused on local responses to wildfires through rigorous sampling programs, providing insight into the stream and river water quality impacts over time. This study takes a human-centered approach by investigating the impact of wildfires on treated drinking water. Studies have shown that wildfires increase the concentration of some regulated contaminants, like disinfection byproducts, nitrate, and metals in drinking water. The goal of this study is to better understand the complex relationships between catchment characteristics, wildfires, and precipitation, on changes to regulated contaminants. A random forest modeling approach, using more than 100 catchment-level variables derived from national datasets (StreamCat, Measuring Trends in Burn Severity, National Hydrography Dataset, and PRISM Climate Project), was trained to predict concentrations of disinfection by-products from more than 10 years of water quality tests from water treatment plants in California. Initial results from the model indicate that it is capable of explaining a high level of variability in the disinfection byproduct concentration data, particularly in catchments impacted by wildfires. Although this study focuses on disinfection byproducts in California specifically, it was constructed in a way that readily allows water managers across the United States to utilize it in post-wildfire contaminant prediction, and, more broadly, in the prediction of any regulated contaminant (e.g. exceedances of nitrate in groundwater used as drinking water). The model suggests that burn severity and precipitation are two of the most important variables for predicting disinfection byproduct concentrations, which is a useful tool to help inform post-fire water quality management.

Changes in the bioaccessibility of metals in soils at a recovering wildfire site

Current double major (Behavioral Neuroscience & Environmental Science) student Rubye Strickland is combining her interdisciplinary skills to examine manganese impacts from burned soils as they recover over time.

Wildfires are increasing with climate change, making the human health implications of exposure to burned soils an essential area of research. Metals associated with fire-impacted soils can be inhaled or accidentally ingested by surrounding communities, causing health risks that may complement risks from particles that cause physical respiratory irritation. This study explores metal changes in burned soils over time as a site naturally recovers from wildfire. The Border 32 fire burned 4,456 acres near the US-Mexico border in Aug-Sept, 2022. Soil samples were collected from the burned area at 0, 3, 6, 9, and 12 months after the fire. Grain size, total metals, soil color, and bioaccessibility experiments characterized the physical and geochemical nature of the site. Over the course of 12 months as the site naturally recovered and revegetated, soil Cr exhibited a weak increase (29 +/- 9 mg kg-1 at 12 months post-fire compared with 18 +/- 5 mg kg-1 in unburned soil controls) and Zn concentrations appeared enriched immediately after the fire (207 +/- 131 mg kg-1 at 0 months post-fire) but steadily declined (89 +/- 23 mg kg-1 at 12 months). Trends in lung fluid bioaccessibility were different. No Zn or Cr were detected in lung fluid though Mn was found to steadily increase from 2-35 mg kg-1 bioaccessibility as the site recovered, approaching the background average bioaccessibility of 44 mg kg-1 Mn. These results suggest that metal biogeochemistry is complex as soils recover from wildfire and though some metals were not detected in lung fluid for these soils at this site, they were detected in more acidic gastric fluid. These results highlight the importance of assessing burned soils chemically at specific sites, particularly where trace elements of health concern like Cr and Mn may be naturally elevated. This project adds to the growing literature that focuses on inhalation risk from particulate matter exposure after fires.