Occurrence of Benzene Polycarboxylic Acids in Ash and Streamwater after the Cameron Peak Fire

To better understand the effects of wildfire on water quality, water and ash samples were collected at multiple stream and river locations following the Cameron Peak Fire. These sites included both burned and unburned parts of the Cache La Poudre watershed in northern Colorado. A series of benzene polycarboxylic acids (BPCAs), including benzene, naphthenic, and biphenyl polycarboxylic acids, were quantitatively measured in streamwater samples for their occurrence in the watersheds; numerous isomers were also detected. High-flow storm events, containing high concentrations of charred organic matter and ash, were sampled during storm runoff (typically high intensity rainfall >5 cm/h). Concentrations of BPCAs ranging from 1 to greater than 100 mu g/L were measured following storm events but were absent from unburned sites and occurred at lower levels (ng/L) during nonstorm conditions. The most concentrated and abundant BPCA in burned samples (1,2,4-benzene tricarboxylic acid) was absent in unburned samples and thus may potentially serve as a tracer of wildfire impacts on water quality. Ash collected immediately following the fire contained the same suite of compounds (mu g/g concentration range) as streamwater samples. These results demonstrate that these BPCAs constitute an important proportion of the organic matter exports after wildfires.