This paper provides a detailed account of the development of a fluorescence based measurement technique for measuring the mass of contaminant on solid surfaces in the presence of water flow. A test apparatus was design and developed for the purpose of studying adsorption and desorption of diesel to and from a copper test surface in the presence of contaminated and fresh water flow, respectively. A calibration technique was developed to correlate the measured fluorescence intensity to the mass of diesel adsorbed per unit surface area (the excess surface density) and the bulk concentration of the diesel in the flow. Both bulk composition and the excess surface density measurements were achieved via a traverse of the fluorescent measurement probe perpendicular to the test surface. Two nominal bulk mass fractions (0.2 % and 0.3 %) were tested each for five different Reynolds numbers between zero and 7000. Measurements for a given condition were made over a period of approximately 200 hours. The measured diesel excess surface density varied between zero and 0.02 kg/m2 for the variation in the bulk mass fraction and Reynolds number of the flow. Freundlich constants were calculated for the various bulk mass fractions and Reynolds numbers.