the LASAT scheme (Table 1b).The site-independent peak-to-mean ratios depending on thedistance from the source are shown in Fig. 3. These are independentof a specific site because only the fixed values of Table 3 enter thealgorithm for the peak-to-mean ratios. Peak-to-mean ratios fordistances larger than 100 m are primarily considered here. Atshorter distances the implicit assumption in Gaussian plumemodels that the longitudinal diffusion is negligible compared to thelateral and vertical diffusion is less and less valid. In Figs. 3 and 4,this distance is marked by a thin vertical line. As the stack height ofthe source is only 8 m (Table 4), separation distances down to 50 mare considered in the statistical analysis in Section 3.2.The peak-to-mean ratios depend strongly on the stability class.For unstable conditions (classes 2 and 3 as well as V and IV), thepeak-to-mean factors, starting at rather high values near thesource, rapidly approach 1 with increasing distance (Fig. 3). This isin agreement with the premise that vertical turbulent mixing canlead to short periods of local high ground-level concentrations,whereas the ambient mean concentrations are low. For neutral and slightly stable conditions (classes 4 and 5 and