Transport of microbiological contaminants in the unsaturated zone of the Chalk aquifer: investigation by tracer test

摘要

Understanding the fate and transport of microbiological contaminants in the subsurface is becoming increasingly important as man-made pressures on groundwater increase. The presence of the unsaturated zone contributes to groundwater protection by reducing vulnerability; the thicker this zone, the greater the residence time of pollutants and potential for attenuation. In order to investigate the role of the unsaturated zone, and in particular that of the Chalk aquifer, a tracer test has been carried out. This tracer test used a range of particles of different sizes to simulate pathogenic microbiological agents ranging from viruses to protozoa, The Chalk is particularly sensitive because it contributes up to 75% of drinking water in some areas of England and is one of the most areally extensive outcropping aquifers. The testing showed that although there is potential for transmission of pathogens to the water table, there is also considerable attenuation.