Potential Overwater Transport of Near Surface Ozone from Proposed Offshore Oil and Gas Development in the Caspian Sea Region

Potential changes to near surface ozone concentration resulting from proposed onshore and offshore oil exploration facilities in the Caspian Sea Region were examined. CMAQ version 4.7 was applied in a nested 36km, 12km and 4km configuration with the 36km nest covering much of central Asia and the 4km nest centered on the area of the development in the northern Caspian Sea. The WRF model version 3.1 was used to develop meteorological fields. The model was run for a three month summer period from June through August of 2007, when highest ozone concentrations are expected. Oil exploration emissions scenarios were based on: 1) peak emissions during standard operation expected to occur in the year 2030; and, 2) maximum short term emissions that might occur during emergency flaring.

Resulting ozone concentrations were examined in terms of one-hour and eight-hour maximum onshore and offshore concentrations. In addition, the AOT40 metric for cumulative exposure of vegetation to daytime ozone over 40ppb was calculated for both the maximum five-day exposure and over the full three month period. Model results show order of magnitude differences in horizontal transport of ozone plumes between over land and over water regimes, reflecting the respective difference in surface deposition between land and water. Results have important implication for offshore exposure of workers in settings such as oil platforms or fishing fleets and for exposure of population and vegetation in coastal regions at distances in excess of 100 km from emissions sources.