Compositions of ash, soil, sediment, water, and biota after the 2020 CZU Lightning Complex Wildfire, Santa Cruz Mountains, California
By Renee K. Takesue, Leticia P. Hallas, Pamela L. Campbell-Swarzenski, Nancy G Prouty, and Amy E. East
https://doi.org/10.5066/P13QWYFV
Dates
Published: Dec. 11, 2025
Summary
The CZU Lightning Complex Wildfire burned 86,500 acres of forested coastal watersheds in the Santa Cruz Mountains, CA, from August 16 to September 22, 2020. Ash, soil, and stream sediment were collected and characterized as soon as sites could be safely accessed to quantify potential environmental and public hazards from wildfire-related potentially toxic metals and polycyclic aromatic hydrocarbons (PAHs). Sites were chosen to reflect conditions with low, moderate, and severe soil burn severities. Repeated collections at regular intervals over three years showed temporal changes of in situ wildfire-related chemicals and changes related to transport of wildfire-materials in coastal watersheds. Stable isotopes, radiocarbon, and PAHs were measured in dominant plants, stream biota (steelhead and crayfish) and intertidal mussels to determine how wildfire constituents were taken up by organisms. Airborne wildfire particulates were collected and characterized downwind in Santa Cruz up to one month post-fire. Sediment provenance in Scott Creek and three of its tributaries was determined from geochemical fingerprinting of underlying parent rocks. In combination, these parameters show how the chemistry of hillslope soil and stream sediment and biota of forested coastal watersheds were affected by wildfire and how recovery progressed over three years.
Sampling Data
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Charcoal counts, stable isotopes, and elemental chemistry of particulate materials after the 2020 CZU Wildfire
After the CZU Wildfire in August 2020, stream sediment (7 burned, 1 unburned drainages), airborne ash, in situ ash, and regolith were collected from August 2020 to August 2023 to characterize wildfire effects. Solid-phase parameters include sand-sized charcoal counts, total carbon (TC), total inorganic carbon (TIC), total organic carbon (TOC), bulk stable carbon 13/12 isotope ratios (d13C), bulk stable nitrogen 15/14 isotope ratios (d15N), and concentrations of 60 elements in the less than 63 micron fine fraction.
Data Files
CZUparticulates_charcoal_isotopes_elements_data.csv - 80.7 KB - MD5:6f0f951f994255e520d25f41f0b56dfc
Metadata Files
CZUparticulates_charcoal_isotopes_elements_metadata.xml - 54.3 KB
CZUparticulates_charcoal_isotopes_elements_metadata.txt - 54.1 KB
Left bank of Little Creek five months after the 2020 CZU Wildfire -
Parent and alkylated polycyclic aromatic hydrocarbons (PAHs) in ash, stream sediment, steelhead, crayfish, and marine mussels after the 2020 CZU Wildfire
Seventy-six parent and alkylated polycyclic aromatic hydrocarbons (PAHs) were quantified in wildfire ash (airborne and in situ), stream sediment, steelhead, crayfish, and marine mussels after the August 2020 CZU Lightning Complex Wildfire and at regular intervals over three years.
Data Files
CZUallPAHs_ash_sediment_biota_data.csv - 268.8 KB - MD5:a82dc8e578f1180018cef22ef8cb9d06
Metadata Files
CZUallPAHs_ash_sediment_biota_metadata.xml - 216.3 KB
CZUallPAHs_ash_sediment_biota_metadata.txt - 232.4 KB
Black carbon on a Santa Cruz beach after the 2020 CZU Wildfire. Photo credit: Ferdinand Oberle
Related Field Activities
- 2020-638-FA - View Details
Suggested Citation
Takesue, R.K., Campbell-Swarzenski, P.L., Hallas, L.P., Prouty, N.G., and East, A.E., 2025, Compositions of ash, soil, sediment, water, and biota after the 2020 CZU Lightning Complex Wildfire, Santa Cruz Mountains, California: U.S. Geological Survey Data Release, https://doi.org/10.5066/P13QWYFV.
2020 CZU Wildfire studies
