Non Destructive on Site Measurement of Algal Biofilms on Historic Surfaces

摘要

Algal biofilms on developing on surfaces are an important factor in materials deterioration. As well as bringing about aesthetic deterioration of a surface, they support the growth of other more aggressive biodeteriogens such as bacteria and fungi. Biocides are used to protect surfaces from such biofouling and there is a large requirement for cheap, sensitive, and rugged sensors for rapid determination of their effectiveness. Small ultra bright LED's are ideally suited as fluorescent excitation sources for small light, instruments ideally suited for use in daily fieldwork. To this end the authors have developed a device to detect chlorophyll in algal biofilms on solid surfaces. An important aspect of monitoring the effectiveness of biocide treatments is to obtain field data about the fluorescence of the biofilms under ambient conditions over time. Monitoring programmes have been set up at various historic sites and data collected throughout the year. Measurements have been made in summer and winter and fluorescence intensities of algae on Roman mosaic and on biocide-treated medieval plaster shown. The instrument demonstrates a linear sensitivity of less than 10 algal cells per mm This sensitivity means that biocides can be applied in minimal concentrations, and their efficiency monitored quickly on site using the LED based system.