Framework for nontargeted investigation of contaminants released by wildfires into stormwater runoff: Case study in the northern San Francisco Bay area

Abstract

This article is part of the special series "Ecological consequences of wildfires." The series documents the impacts of largescale wildfires in many areas of the globe on biodiversity and ecosystem condition in both terrestrial and aquatic ecosystems, the capacity for systems to recover and management practices needed to prevent such destruction in the future.

Suspect Screening and Chemical Profile Analysis of Storm‐Water Runoff Following 2017 Wildfires in Northern California

“…The features were then annotated with sample collection sites and storm events, and numbers of features for each sampling and reference sites are summarized in Table 1. No clear relationship was observed between overall numbers of features and levels of development or burned percentage (Supporting Information, Table S1), though in the companion study using gas chromatography (GC) × GC/TOF, Chang et al (2021) observed that the number of detected analytes increased with the number of structures that were damaged or destroyed. Principal component analysis was carried out for all features in both positive and negative modes (Supporting Information, Figure S1).…”

“…The sampling sites in Sonoma were located around Sonoma Creek, with the reference site located on the nearby Graham Creek tributary to Sonoma Creek. The watersheds of reference sites do not contain significant development (<0.05%), whereas wildfire‐impacted sites contain watersheds with a wide range of development (<1% in three cases and 3%–59% in the remaining seven cases; Chang et al, 2021). The city of Santa Rosa samples were collected only during the first storm event, and no specific reference site was sampled.…”

“…Both storm events were considered suitable for sampling after passing the threshold of >2.54 cm (1 inch) of precipitation in a span of 24 h. Baseline turbidity is known to be <1.5 nephelometric turbidity units (NTU) at the reference sites and 0.5–6 NTU at the other sites (Chang et al, 2021). In contrast, turbidity during the storms was 18 and 192 NTU at the Sonoma reference site and 2 and 29 NTU at the Napa reference site during Storms 1 and 2, respectively.…”

“…It was interesting that both OPFR levels in Santa Rosa samples were much higher than the rest, possibly attributable to the combustion of more building structures and housing. As summarized by CalFire and our collaborative study, the city of Santa Rosa experienced the highest severity of fire in terms of structures destroyed or damaged (Tubbs Fire, 5953 structures; CalFire, n.d.; Chang et al, 2021).…”

“…However, because of sampling limitations, there were no samples collected before the wildfires or after Storm Event 2 in Santa Rosa, and only one reference location per region per storm event was sampled. As a collaboration study noted (Chang et al, 2021), the reference sites might not be ideal because they were less developed sites compared with sites that were impacted by fire. Thus, the differences we observed might be due to a combination of wildfire and urban development.…”