제주도 산림 대기 내 monoterpene의 분포특성

Abstract

Biogenic emissions from forest, crops and grasslands are now considered major compounds in photochemical processes, affecting the production of chemical oxidants, and possibly the formation of organic aerosols. In Jeju Island, a forest is well preserved and trees and plant cover about half of the whole island. Population density and industrial activity in this area are very low. Therefore, the emissions of anthropogenic pollutants may be ignored. In this situations, the emissions of BVOCs may play a significant role in the atmospheric chemistry in this region. Nevertheless, no studies have been conducted to determine the characteristics of BVOCs emissions in this island. The investigations presented in this study focus on how the concentrations of monoterpenes are distributed in the atmosphere of forest. For this purpose, field experiments are performed mainly at two different sites, one is coniferous forest and the other in broad leaved forest. Concentrations of BVOCs are measured in the forest atmosphere. Measurements of monoterpene concentration are taken at 1.5m, 9m and 15m(or 12m) above ground level. The forest canopy is situated between 11m and 14m above ground level in these sampling sites. BVOCs are sampled on the absorption tubes, filled with 300㎎ Tenax TA. 24L air samples are taken at a rate of approximately 100㎖/min with aid of a battery powered sampling pump. At the end of the sampling works the tubes are transported back to the laboratory for analysis with GC/MS. A number of BVOCs are identified in the atmosphere of the broad leaved forest. This shows that plant leaves emit a broad spectrum of organic compounds that typically play multiple roles in plant protection. For the monoterpene identified in this study, a very distinct diurnal variation is observed. It can be clearly seen that there is an increase in the concentration of monoterpene species at night, regardless of the species of trees. The monoterpene concentration of ambient air in the coniferous forest is about 2 times higher than that in the broad leaved forest. On the other hand, the concentration at Cheju National University located at rural area is very low and, at a city hall located at the downtown of Jeju city, not detected. Measurements with height above ground level shows that the concentration in the ambient air at outside of forest canopy is lower than those below the canopy. The seasonal variations of monoterpene concentrations are also distinct.