| Light alkane hydrocarbons are present in major quantities in the near-surface atmosphere of Texas, Oklahoma and Kansas. Elevated levels of the (C1 –C6) light alkanes were first observed in Oklahoma City. A regional study conducted in September 2001 centered around Oklahoma City showed the light alkanes to be enhanced regionally. A second more extensive regional study was conducted in spring 2002 using a grid sampling configuration. The grid sampling configuration provided very effective in identifying areas of enhancement for the light alkanes. The elevated alkane mixing ratios are attributed to emissions from the oil and natural gas industries within the area. In addition, measured alkyl nitrated mixing ratios were comparable to urban smog values, indicating active photochemistry in the presence of nitrogen oxides, and therefore with abundant formation of tropospheric ozone. We estimate 4–6 Tg of methane, a significant fraction of total U.S. emissions, are released annually within the region. Annual ethane emissions from the study region are estimated to be 0.3–0.5 Tg yr−1. |
