Field measurements of the near-ground odorant concentrations were made in surrounding of the mechanical sewage treatment plant with separated digestive chamber. The concentrations downwind the pollutants plume in several different meteorological situations were the basis for the estimations by a process of trial and error. The estimations encompassed the total emission of odorants and emission rates related to the volume of the purified sewage, to the amount of the removed pollutants and to the area of the unorganized emission sources during the autumn. Parallel research concerning other seasons and different surface sources of odorants are planned.

Assessments of odour nuisance are made using one of the psychophysical laws: logarithmic Weber- Fechner law or power law by Stevens. The object of the work was to determine whether one of the laws exhibits advantage over the other. To evaluate the two laws series of odorimetric measurements of aqueous solutions of acetic acid were made. Values of Pearson' correlation coefficient were calculated for relationship of the odour intensity (I) versus logarithm of the acetic acid concentration in air (Iog., C [mg/rrr'I) as well as for the relationship of logarithm of the odour intensity (log,0/) versus logarithm of the acetic acid concentration in air (log., C [rng/nr'[). Both laws are fulfilled equally well in a range of investigated concentrations of acetic acid.

Evaluations of odour intensity of the air polluted with cyclohexane (A), cyclohexanone (B) and cyclohexane with admixtures of cyclohexanone (mixtures MI, M2 and M3; x8 = 0.14; 0.05 and 0.02 respectively) were made. Empirical parameters of psychophysical equations (Weber-Fechner' and Stevens') were determined. Total concentrations of the mixtures were within the range C = 1500-3500 ppm. The interaction constant av= 115-132° was estimated for the mixtures. Verification of known models of odour interaction led to the conclusion that possible application of the models for prediction of odour intensity of the air polluted with mixtures of cyclohexane and hexane is limited.