Low-cost UV-induced fluorescence sensor for monitoring aromatic hydrocarbons in coastal marine water

Nowadays the coastal waters of the Mediterranean Sea are increasingly affected by pollution from aromatic hydrocarbons. Therefore, in order to implement damage minimization actions, a continuous monitoring system with rapid response is needed. The most effective local method for distinguishing aromatic hydrocarbons from salt water is UV-induced fluorescence. This paper describes the design and building of a UV-induced fluorescence sensor that, mounted on board a sensor-buoy, detects the presence or absence of the pollutant in any atmospheric condition. The sensor consists of a measuring chamber, in which the water, loaded by a submersible pump, maintains a constant level thanks to a small siphon. The detection system, consisting of a UVC-LED and a phototransistor that responds in the visible light band, is located in the upper part of the chamber. In vitro tests, performed by comparing the sensor results with those obtained from a spectrofluorometer, have shown good sensitivity, repeatability, and accuracy, despite the inexpensiveness and low energy consumption of the sensor. An important goal achieved by the design and building methodology is that the sensor is able to withstand harsh weather conditions, the corrosive action of salt water and biofouling.