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The adsorption of several different organic polyelectrolytes from aqueous solution by activated carbon was characterized. Polyelectrolytes included humic acids extracted from peat and soil, polymaleic acid, a synthetic polymer identified as a fulvic acid surrogate, and natural organic matter in Huron River (Ann Arbor, MI) water. Isotherms of individual ultrafiltration size fractions confirmed that smaller molecular size components adsorb to a greater extent on an adsorbent mass basis. The molecular weight distributions of organic polyelectrolytes remaining in solution after equilibration with various amounts of activated carbon were measured with high-performance size-exclusion chromatography (HPSEC). A comparison of molecular weight distributions demonstrated conclusively that small molecular size components are adsorbed preferentially; i.e., adsorptive fractionation on the basis of molecular size occurs. This behavior was observed for each of the wide variety of samples studied, suggesting that it may be a rather general feature of the adsorption of polyelectrolyte mixtures from solution by activated carbon.

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Wildfire occurrence and intensity are increasing worldwide causing severe disturbances to forest watersheds used for potable water supply. The effects of wildfire on drinking water quality are not well understood, especially in terms of terrestrial dissolved organic matter (DOM) and DOM-associated formation of disinfection byproducts (DBP). As the forest floor layer is a major source of terrestrial DOM, we investigated characteristics and DBP formation of water extractable organic matter (WEOM) from the 0−5 cm depth of nonburned detritus (control) and burned detritus with black ash (moderate severity) and white ash (high severity) associated with the 2013 Rim Fire in California. Spectroscopic results suggested that the aromaticity of WEOM followed white ash > control > black ash and fluorescence region II (excitation 220−250 nm; emission 330−380 nm) of the emission-excitation-matrix was identified as a potential burn severity indicator. Compared to the control, WEOM from white and black ashes had lower reactivity in forming trihalomethanes (55%-of-control) and haloacetic acids (67%-of-control), but higher reactivity in forming the more carcinogenic haloacetonitrile after chlorination (244%-of-control) and N-nitrosodimethylamine after chloramination (229%-of-control). There was no change in reactivity for chloral hydrate formation, while WEOM from black ash showed a higher reactivity for haloketone formation (150%-of-control). Because wildfire consumed a large portion of organic matter from the detritus layer, there was lower water extractable organic carbon (27%-of-control) and organic nitrogen (19%-of-control) yields in ashes. Consequently, the wildfire caused an overall reduction in water extractable terrestrial DBP precursor yield from detritus materials.

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