USE OF AN ELECTRONIC NOSE TO MEASURE ODOR CONCENTRATION FOLLOWING APPLICATION OF CATTLE SLURRY TO GRASSLAND

Three experiments were conducted in which odour samples were taken at time intervals following application of cattle slurry to grassland. Me asurements were made of odour concentration by dynamic dilution olfact ometry and of sensor response using two electronic nose instruments wi th conducting polymer type sensor arrays (the Aromascan and the Odour- mapper). Significant linear relationships (P < 0.01) were found betwee n odour concentration and average sensor response, a single line being fitted to data from all three experiments, with % variance accounted for of 59% and 62% for the Aromascan and Odour-mapper respectively. Se nsor responses were normalized, the response of each sensor being expr essed as a percentage of the summed response across all sensors, and p rincipal components analysis (PCA) used as a means of comparing the no rmalized response patterns. Normalized response patterns from samples from the three experiments were not distinctly different and could all be classed as the same ''odour type'' by the electronic nose instrume nts. Actual response patterns (before normalisation) were also compare d using PCA and again there was no difference between experiments (aft er taking account of background samples) but a concentration effect wa s apparent, with response patterns for odour samples taken immediately following slurry application being distinctly different from patterns for subsequent samples. The experiments demonstrated the ability of e lectronic nose instruments with conducting polymer type sensors to res pond to agricultural odours at much lower concentrations than had prev iously been achieved so leading to the possibility of developing a por table instrument for odour measurement in the field. (C) 1997 Silsoe R esearch Institute.