Growing Algae Alter Spectroscopic Characteristics and Chlorine Reactivity of Dissolved Organic Matter from Thermally-Altered Forest Litters

Previous studies demonstrated that wildfires alter spectroscopic characteristics of terrestrial dissolved organic matter (DOM) and increase specific disinfection byproduct formation potential (SDBP-FP). However, it is unclear whether characteristicg.of thermally altered DOM (TA-DOM) are altered by biogeochemical processes (e.g., transformed by growing algae) before entering water treatment facilities. The freshwater green algae Pseudokirchneriella subcapitata and blue-green algae Microcystis aeruginosa were separately incubated in the.mixture of cultural medium and pine (Pinus palustris) litter-derived TA-DOMs (50 degrees C, 250 degrees C, and 400 degrees C) over 7 days to demonstrate the effects of algal growth on alterations in SDBP-FP. TA-DOM optical characteristics and SDBP-FP were quantified by absorption and fluorescence spectroscopy and chlorination-based DBP-FP experiments. After the inoculation with P. subcapitata, TA-DOM aromaticity (indicated by SUVA(254)) increased from 1.19 to 1.90 L/mg/m for 50 degrees C-extract but decreased from 4.95 to 3.75 L/mg/m for 400 degrees C-extract. The fraction of tyrosine-like components decreased from 25.9 to 9.3% for 50 degrees C-extract but increased from 0.9 to 1.3% for 400 degrees C-extract. Same patterns were also observed for M aeruginosa. Growing algae generally increased chlorine reactivities and formations of trihalornethanes, haloacetonitriles, chloral hydrate, and haloketones. Our data suggest that the biodegradable dissolved organic carbon in TA-DOM decreases as fire intensity (i.e., temperature) increases. Postfire algal blooms can increase chlorine reactivity of fire-affected terrestrial DOM for DBP formation.