Estimation of incremental reactivities for multiple day scenarios: an application to ethane and dimethyoxymethane

Single-day scenarios are used to calculate incremental reactivities by defi nition (Carter, J. Air Waste Management Assoc. 44 (1994) 881-899.) but even unreactive organic compounds may have a non-negligible effect on ozone con centrations if multiple-day scenarios are considered. The concentration of unreactive compounds and their products may build up over a multiple-day pe riod and the oxidation products may be highly reactive or highly unreactive affecting the overall incremental reactivity of the organic compound. We h ave developed a method for calculating incremental reactivities for multipl e days based on a standard scenario for polluted European conditions. This method was used to estimate maximum incremental reactivities (MIR) and maxi mum ozone incremental reactivities (MOIR) for ethane and dimethyoxymethane for scenarios ranging from 1 to 6 days. It was found that the incremental r eactivities increased as the length of the simulation period increased. The MIR of ethane increased faster than the value for dimethyoxymethane as the scenarios became longer. The MOIRs of ethane and dimethyoxymethane increas ed but the change was more modest for scenarios longer than 3 days. MOIRs o f both volatile organic compounds were equal within the uncertainties of th eir chemical mechanisms by the 5 day scenario. These results show that dime thyoxymethane has an ozone forming potential on a per mass basis that is on ly somewhat greater than ethane if multiple-day scenarios are considered. ( C) 2001 Elsevier Science Ltd. All rights reserved.