Ozone Monitoring and Canopy Effect in the Great Smoky Mountains National Park

Vegetative uptake of ozone, or canopy effect can cause considerable differences in ozone concentration. The ability to quantify and determine the presence of canopy effect is of importance when relating ozone exposure to a health effects study being conducted in Great Smoky Mountains National Park. The concentrations seen inside and outside of the canopy differed by as much as 13 ppb and 16%. The canopy effect was quantified and evaluated to determine if the ozone concentrations measured at the trailhead at New Found Gap warranted an adjustment to accommodate for the different ozone concentrations the participants of the hiker-health study were exposed to while hiking. The ozone monitor at the New Found Gap trailhead was also investigated for the presence of a canopy effect. The monitor showed no significant effect from the bordering trees. However, the hikers, when on the trail, were within the canopy where lower than ambient ozone concentrations were present. The final recommendation was to lower ambient ozone concentrations measured at New Found Gap by 13% for the time spent on the trail by one of the three approaches presented.