Dissolved black carbon as a potential driver of surface water heating dynamics in wildfire-impacted regions: A case study from Pyramid Lake, NV, USA

Brittany R Kruger; Mark B Hausner; Nathan Chellman; Morgan Weaver; Vera Samburova; Andrey Khlystov

doi:10.1016/j.scitotenv.2023.164141

Dissolved black carbon as a potential driver of surface water heating dynamics in wildfire-impacted regions: A case study from Pyramid Lake, NV, USA

Sci Total Environ. 2023 Aug 25:888:164141. doi: 10.1016/j.scitotenv.2023.164141. Epub 2023 May 11.

Authors

Brittany R Kruger¹, Mark B Hausner², Nathan Chellman², Morgan Weaver³, Vera Samburova⁴, Andrey Khlystov⁴

Affiliations

¹ Desert Research Institute, Division of Hydrologic Sciences, 755 E Flamingo Rd, Las Vegas, NV 89119, USA. Electronic address: brittany.kruger@dri.edu.
² Desert Research Institute, Division of Hydrologic Sciences, 2215 Raggio Pkwy, Reno, NV 89512, USA.
³ Desert Research Institute, Division of Hydrologic Sciences, 755 E Flamingo Rd, Las Vegas, NV 89119, USA.
⁴ Desert Research Institute, Division of Atmospheric Sciences, 2215 Raggio Pkwy, Reno, NV 89512, USA.

PMID: 37172843
DOI: 10.1016/j.scitotenv.2023.164141

Abstract

Black carbon (BC), pyrogenic residues resulting from the incomplete combustion of organics, are liberated from wildfires at high rates. Subsequent introduction to aqueous environments via atmospheric deposition or overland flow results in the formation of a dissolved fraction, called dissolved black carbon (DBC). As wildfire frequency and intensity increases along with a changing climate, it becomes imperative to understand the impact a concurrent increase in DBC load might have to aquatic ecosystems. In the atmosphere BC stimulates warming by absorbing solar radiation, and similar processes may occur with surface waters that contain DBC. In this work we investigated whether the addition of environmentally relevant levels of DBC could impact surface water heating dynamics in experimental settings. DBC was quantified at multiple locations and depths in Pyramid Lake (NV, USA) during peak fire season while two large, proximal wildfires burned. DBC was detected in Pyramid Lake water at all sampled locations at concentrations (3.6-18 ppb) significantly higher than those reported for other large inland lakes. DBC was positively correlated (R² = 0.84) with chromophoric dissolved organic matter (CDOM) but not bulk dissolved or total organic carbon (DOC, TOC), suggesting that DBC is a significant component of the optically active organics in the lake. Subsequent lab-based experiments were conducted by adding environmentally relevant levels of DBC standards to pure water, exposing the system to solar spectrum radiation, and creating a numerical model of heat transfer based on observed temperatures. The addition of DBC at environmentally relevant orders of magnitude caused reductions to shortwave albedo when exposed to the solar spectrum, which resulted in 5-8 % more incident radiation being absorbed by water and changes to water heating dynamics. In environmental settings, this increase in energy absorption could translate to increased heating of the epilimnion in Pyramid Lake and other wildfire-impacted surface waters.

Keywords: Black carbon; Dissolved black carbon; Water heating dynamics; Wildfire impacts.