Ozone concentrations of three different vertical gradients for a Cunninghamia lanceolata forest in spring and summer at Yandang Mountain National Forest Park, Wenzhou

Abstract

Research on ozone concentration in forests has become a hot area of forest recreation because of its influence on forest growth and environmental quality. The variation of ozone mass concentration at different vertical heights in forest environment has a guiding role in forest recreation activities. Ozone concentration and meteorological factors in three different vertical gradients(The following are expressed by H1, H2 and H3 respectively. H1 stands for 1.5 m from ground, H2 indicates the central part of canopy, H3 means the boundary between canopy and atmosphere.) in Yandang Mountain were monitored for 24 h in the spring and summer of 2017. Their changing features and influencing factors were also observed at the same time. In this experiment, ozone sampler was used to sample three kinds of ozone mass concentration, and the data were processed by variance analysis and multiple comparison analysis. Results indicated that the mean value of 8 h maximum ozone concentration in three different vertical gradients all achieved the primary standard for ambient air quality standards(100 μg·m-3) except for the top of H3 (103.03 μg·m-3) during the spring. Ozone concentration changes for the different vertical gradients was H1 < H2 < H3 in both spring and summer with differences in the daily mean ozone concentration between H1 and H2 and H3 being higher in spring than in summer, there was a significant difference between H2 and H3 (P < 0.05). During the observation period for the two seasons, the daily ozone concentration in the different vertical gradients (H1, H2, and H3) all exhibited a single peak curve, with the highest concentration occurring in 11:00-15:00, whereas the lowest occurring in 5:00. The mean value of the hourly ozone concentration for H1, H2, and H3 during the two seasons was positively related with temperature and wind speed and negatively with humidity as well as pressure. In conclusion, Taking ozone concentration as recreation standard, summer nights was more suitable for people to travel. It was advisable to choose the understory and the middle of the canopy to arrange recreation facilities, such as a plank road in the understory or overhead and a wooden house in a C. lanceolata forest.