Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

• Published in: Water, air, and soil pollution Vol. 204; no. 1-4; pp. 103 - 115
• Main Authors: Clark, David B., Feddersen, Falk, Omand, Melissa M., Guza, R. T.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-11-2009; Springer; Springer Nature B.V
• Subjects: Applied sciences; Atmospheric Protection/Air Quality Control/Air Pollution; Biological oceanography; Bubble barriers; Bubbles; Climate Change/Climate Change Impacts; Contaminants; Dye concentrations; Dyes; Earth and Environmental Science; Environment; Environmental monitoring; Estimates; Exact sciences and technology; Fluorescence; Hydrogeology; Light; Measurement techniques; Pollution; Sand; Sediments; Sensors; Soil Science & Conservation; Streams; Studies; Turbidity; Water pollution; Water Quality/Water Pollution; Fluorometer; Fluorescent dye measurement; Mixing; Surfzone; Dispersion; Turbidity; Dyes; Sediments
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-009-0030-z

Decisions about recreational beach closures would be enhanced if better estimates of surfzone contaminant transport and dilution were available. In situ methods for measuring fluorescent Rhodamine WT dye tracer in the surfzone are presented, increasing the temporal and spatial resolution over previous surfzone techniques. Bubbles and sand suspended by breaking waves in the surfzone interfere with in situ optical fluorometer dye measurements, increasing the lower bound for dye detection (≈ 1 ppb) and reducing (quenching) measured dye concentrations. Simultaneous turbidity measurements are used to estimate the level of bubble and sand interference and correct dye estimates. After correction, root-mean-square dye concentration errors are estimated to be < 5% of dye concentration magnitude, thus demonstrating the viability of in situ surfzone fluorescent dye measurements. The surfzone techniques developed here may be applicable to other environments with high bubble and sand concentrations (e.g., cascading rivers and streams).