Results

ROEs for atmospheric plume-centerline, ground-level concentrations of hydrogen sulfide resulting from instanta­neous and continuous hydrogen sulfide releases were pre­dicted and are presented in Figures C-l through C-4. Figures C-l and C-2 present the predicted ROEs for continuous hy­drogen sulfide releases during worst case daytime and night­time meteorological conditions, respectively. Figures C-3 and C-4 present the predicted ROEs for instantaneous hydro­gen sulfide releases during worst case daytime and nighttime meteorological conditions, respectively. The ROEs for con­centrations of 10, 30, 100, 300 and 500 ppm were modeled for both release types. The 10 ppm concentration ROEs rep­resent an 8-hour averaging time for the continuous hydrogen sulfide release and a 10-minute averaging time for the instan­taneous release. The 30, 100, 300, and 500 ppm concentra­tion ROEs represent a 10-minute averaging time for the continuous hydrogen sulfide release and a 1-minute averag-

ing time for the instantaneous release. A hydrogen sulfide re­lease rate range of 10 to 10,000 lb/hr (111.8 to 111,765 SCFH) was modeled for the continuous type release. For the puff (instantaneous) type hydrogen sulfide release, a release quantity range of 0.1 to 1000 lbs (1.1 to 11,177 SCF) was modeled. If the hydrogen sulfide release is based on pounds, standard cubic feet (SCF) can be obtained by multiplying pounds by a factor of 11.2.

Note: The ROEs presented in Figures C-l through C-4 are plotted against the amount of hydrogen sulfide released. For the release of a multi-compo­nent gas stream, the actual amount of hydrogen sulfide released should be used to determine the ROE.

Equation coefficients based on linear regression for pre­dicting the ROE as a function of the release type (continu­ous/puff) and quantity/rate of hydrogen sulfide released for both daytime and nighttime meteorological conditions are presented in Table C-l. The equation is given in Par. C.8. The coefficients are applicable only over the ranges pre­sented in Figures C-l through C-4, and extrapolation could result in overly conservative estimates of the ROEs. Any re­lease lasting significantly longer than 15 minutes should be interpreted as a continuous release. The modeling work pre­sented in Appendix С assumes steady-state meteorological conditions. ROEs predicted for a long averaging time (8-hour) and long downwind distances are conservative because it is unlikely that the same meteorological conditions will persist during that time period.