Reactivity of Litter Leachates from California Oak Woodlands in the Formation of Disinfection By-Products
- Alex T. Chowa,
- Anthony T. O'Geenb,
- Randy A. Dahlgrenb,
- Francisco J. Díazb,
- Kin-Hang Wongc and
- Po-Keung Wong *c
- a The Baruch Institute of Coastal Ecology & Forest Science, Clemson Univ., Georgetown, SC 29440
b Dep. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616
c School of Life Science, The Chinese Univ. of Hong Kong, Shatin, N.T. Hong Kong SAR, China. Assigned to Associate Editor Robert Cook
Litter materials from forested watersheds can be a significant source of dissolved organic matter (DOM) to surface waters that can contribute to the formation of carcinogenic disinfection by-products (DBPs) during drinking-water chlorination. This study characterized the reactivity of DOM from litter leachates of representative vegetation in oak woodlands, a major plant community in the Foothill Region of California. Leachates from fresh and decomposed litter (duff) from two oak species, pine, and annual grasses were collected for an entire rainy season to evaluate their reactivity to form DBPs on chlorination. Relationships among specific ultraviolet absorbance (SUVA), fluorescence index (FI), specific differential ultraviolet absorbance (SΔUVA), specific chlorine demand (SCD), and the dissolved organic carbon:dissolved organic nitrogen (DOC:DON) ratio to the specific DBP formation potential (SDBP-FP) were examined. The DOM derived from litter materials had considerable reactivity in forming trihalomethanes (THMs) (1.80–3.49 mmol mol−1), haloacetic acid (HAAs) (1.62–2.76 mmol mol−1), haloacetonitriles (HANs) (0.12–0.37 mmol mol−1), and chloral hydrate (CHD) (0.16–0.28 mmol mol−1). These values are comparable to other identified watershed sources of DBP precursors reported for the California Delta, such as wetlands and organic soils. Vegetation type and litter decomposition stage (fresh litter versus 1–5 yr-old duff) were key factors that determined characteristics of DOM and their reactivity to form DBPs. Pine litter had significantly lower specific THM formation potential compared with oak and grass, and decomposed duff had a greater DON content, which is a precursor of HANs and other nitrogenous DBPs. The SUVA and SDBP-FP were temporally variable and dependent on vegetation type, degree of decomposition, and environmental conditions. Among the optical properties of DOM, SΔUVA was the only parameter that was consistently correlated with SDBP-FP.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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