title: Temporal variations of disinfection byproduct precursors in wildfire detritus.
abstract: The Rim Fire ignited on August 17, 2013 and became the third largest wildfire in California history. The fire consumed 104,131 ha of forested watersheds that were the drinking water source for 2.6 million residents in the San Francisco Bay area. To understand temporal variations in dissolved organic matter (DOM) after the wildfire and its potential impacts on disinfection byproduct (DBP) formation in source water supply, we collected the 0-5 cm ash/soil layer with surface deposits of white ash (high burn severity) and black ash (moderate burn severity) within the Rim Fire perimeter in Oct 2013 (pre-rainfall) for five sequential extractions, and in Dec 2013 (∼87 mm cumulative precipitation) and Aug 2014 (∼617 mm cumulative precipitation) for a single water extraction. Water-extractable DOM was characterized by absorption and fluorescence spectroscopy and DBP formation tests. Both increasing cumulative precipitation in the field or number of extractions in the lab resulted in a significant decrease in specific conductivity, dissolved organic carbon, and DBP formation potential, but an increase in DOM aromaticity (reflected by specific UV absorbance). However, the lab sequential leaching failed to capture the increase of the NOx(-)-N/NH4(+)-N ratio and the decrease in pH and dissolved organic carbon/nitrogen ratio of ash/soil extracts from Oct 2013 to Aug 2014. Increasing cumulative precipitation, inferring an increase in leaching after fire, led to an increase in DOM reactivity to form trihalomethanes, haloacetic acids, and chloral hydrate, but not for haloketones, haloacetonitrile, or N-nitrosodimethylamine, which were more related to the original burn severity. This study highlights that fire-affected DBP precursors for different DBP species have distinct temporal variation possibly due to their various sensitivity to biogeochemical alterations.
authors.affiliation: Baruch Institute of Coastal Ecology & Forest Science, Clemson University, Georgetown, SC, 29442, USA.
authors.forename: Jun-Jian
authors.initials: JJ
authors.lastname: Wang
authors.affiliation: Department of Land, Air and Water Resources, University of California - Davis, CA, 95616, USA.
authors.forename: Randy A
authors.initials: RA
authors.lastname: Dahlgren
authors.affiliation: Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC, 29625, USA.
authors.forename: Mahmut S
authors.initials: MS
authors.lastname: Erşan
authors.affiliation: Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC, 29625, USA.
authors.forename: Tanju
authors.initials: T
authors.lastname: Karanfil
authors.affiliation: Baruch Institute of Coastal Ecology & Forest Science, Clemson University, Georgetown, SC, 29442, USA; Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC, 29625, USA. Electronic address: achow@clemson.edu.
authors.forename: Alex T
authors.initials: AT
authors.lastname: Chow
mesh_terms: D004128:Dimethylnitrosamine; D004203:Disinfection; D005390:Fires; D009584:Nitrogen; D022882:Trihalomethanes
chemical_list: D022882:Trihalomethanes; D004128:Dimethylnitrosamine; D009584:Nitrogen
keywords: Dissolved organic matter; Forest fires; Source water treatment; Trihalomethanes; Water quality