Development of a Protocol for Sampling Faecal Coliform Bacteria Originating from Manure in the Vadose zone

摘要

Contamination of water resources with components of manure is a significant concern in Ontario. One aspect is the potential for bacterial transport through the vadose zone to groundwater following field application of manure. One obstacle to characterizing the movement of faecal bacteria in the vadose zone is the sampling of soil solution for bacteria. Porous-cup suction samplers are com- monly used in estimating solute transport through this zone. However, there is little information on the calibration of such samplers for estimating numbers of bacteria in soil solution. This paper reports an attempt to make such a calibra- tion. Tests were carried out under laboratory conditions which simulated the sampling of soil solution under field situation. As the suction applied was less than the air entry value for the ceramic porous cups used, the saturation status of the medium surrounding the cups was only important in terms of the num- ber of colonies-forming units collected and not whether they were detected. The results indicated that although there were limitations in the use of the porous-cup suction samplers for bacterial sampling because of filtration effects, such samplers could be used for field collection of faecal bacteria from soil solution in situations with contrasting initial boundary conditions.