Ultraviolet absorbance as a proxy for total dissolved mercury in streams

Dittman, Jason A.; Shanley, James B.; Driscoll, Charles T.; Aiken, George R.; Chalmers, Ann T.; Towse, Janet E.

Ultraviolet absorbance as a proxy for total dissolved mercury in streams

2009

Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THgd), DOC concentration and DOC composition, and UV₂₅₄ absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive correlation of THgd to DOC (r² = 0.87), but progressively stronger correlations of THgd with the hydrophobic acid fraction (HPOA) of DOC (r² = 0.91) and with UV254 absorbance (r² = 0.92). The strength of the UV₂₅₄ absorbance-THgd relationship suggests that optical properties associated with dissolved organic matter may be excellent proxies for THgd concentration in these streams. Ease of sample collection and analysis, the potential application of in-situ optical sensors, and the possibility for intensive monitoring over the hydrograph make this an effective, inexpensive approach to estimate THgd flux in drainage waters. Ultraviolet absorbance measurements are a cost-effective proxy to estimate dissolved mercury concentration in stream water.

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