As mentioned in previous posts, tropospheric ozone (O3) is a secondary pollutant formed by photochemical reactions. Though some are from natural sources, as an anthropogenic air pollutant is sourced from the emissions from fossil fuel combustion.

In the Northeastern United States, ozone is of regional scale importance due to long-range transport within slow moving and often stagnant high pressure systems (Skelly, 2000). The injection of this primary pollutant from a plethora of industrial, transport, and urban sources results in the significant exposure of ozone to forests and natural plant communities in the downward region. Rural sites are also found to have higher long term ozone exposures, where polluted air masses are transported downwind from urban or industrial centres (Comrie, 1994). As mentioned before, this is an example of how pollutants can be transported through space.

Ozone exposure symptoms are recognized into acute or chronic responses (Skelly, 2000). Acute injuries involve the death of cells are seen within a few hours or days after exposure. These often materialise in the form of bifacial flecking with tan to dark brown spots. Chronic types of injuries develop often on a more routine basis for sensitive plant species. These subtle symptoms develop more slowly (days to weeks).

Ozone is perhaps the most concerning pollutant as it has tremendous effects on the long-term productivity and health of trees along with other native plants that are located in the natural forested areas of the Northeastern United States.

References:

Comrie, A. C. (1994). A synoptic climatology of rural ozone pollution at three forest sites in pennsylvania. Atmospheric Environment (1994), 28(9), 1601-1614. doi:10.1016/1352-2310(94)90306-9

Skelly, J. M. (2000). Tropospheric ozone and its importance to forests and natural plant communities of the northeastern United States. Northeastern Naturalist, 7(3), 221-236.