BACKGROUND FLUORESCENCE ANALYSIS AS A TOOL TO CHARACTERIZE AND CORRELATE WATERS DRAINING THE ALAKAI SWAMP, KAUAI

The Alaka’i Swamp lies on the high western-side of the shield volcano that created Kauai some 5 million years ago. The climatic setting is northeast trade wind dominated with annual rainfall at topographically high Mt. Waialeale in excess of 1000 cm/yr tapering to 250 cm/yr in the lower northwestern part of the swamp. Much of that water, plus additional high-altitude bog cloud/fog moisture, drains northwestward across and through the region of the swamp. Surface water, tapped by three main tributaries, drains southward through the Waimea Canyon. A significant portion is thought to drain as groundwater to the northern segment of the Na Pali coast.

In order to better characterize the Alaka’i and its drainage system, 19 water samples were collected from bogs, springs, wells, and stream waters within the swamp and at major tributaries draining the Alaka’i and the Waimea Canyon. In addition to field parameters, major and minor elements and stable isotopes, samples were analyzed for DOC and background fluorescence analysis on both filtered and acidified samples.

In the filtered samples, synchroscans of most of the waters collected had a major peak at an emission wavelength of about 480 nm and the RFI had a strong linear correlation with DOC (R² = 0.94). In the acidified samples (representing the fulvic acid characteristic) there were 3 major patterns representing different organic signatures: One set with peaks at about 300 nm and 360 nm, one with a major peak at only 300 nm and all others with peaks at 360 nm and 480 nm with fluctuating relative intensity. Analysis indicates that these 3 fingerprints may be used to correlate the sites from which each of these waters were derived and has the potential as a tool to characterize the Alaka’i swamp and its surface and subsurface drainage system.