Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 11:30:00 AM

Location: San Miguel

Koopmans, D, J, University of Georgia, Athens, USA, dirk@arches.uga.edu

Bronk, D, A, College of William and Mary/VIMS, Gloucester Pt. , USA, bronk@vims.edu

PHOTOPRODUCTION OF AMMONIUM IN AN ESTUARY AND ADJACENT SURFICIAL GROUNDWATER

We measured ammonium photoproduction in water collected from the Satilla River estuary and adjacent surficial groundwater (1.5m depth) in Georgia. Previous work has shown that ammonium photoproduction from dissolved organic nitrogen (DON) can be inconsistent. To improve detection of the photochemical signal we temporarily brought a fraction of each sample to pH 9.5, volatilizing ambient ammonium. We ultrafiltered the remaining fraction (1000 Dalton MWCO), concentrating the high molecular weight (HMW) DON one-and-a-half to two fold. Both fractions were irradiated in quartz tubes for eight hours by a xenon lamp, which mimicked the spectra and intensity of June midday sunlight (controls were wrapped in foil). Low concentrations of ammonium (0.1 to 0.2 uM) were produced photochemically in both fractions of estuarine water (four of four samples) and in ammonium-free groundwater (two of two samples), corresponding to DON losses of 0.1 to 1.0%. In contrast, photochemically mediated loss of ammonium (0.2 to 0.4 uM) was measured in the HMW groundwater treatment (two of two samples).

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Aquatic Sciences Meeting, Albuquerque 2001

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