제주지역의 식물기원 VOCs 배출 특성과 오존 생성에 미치는 영향 연구

Abstract

The objectives of this study are to characterize the emission of biogenic volatile organic compounds (BVOCs) emitted from forest in Jeju area and to examine the impacts of these BVOCs into ambient air on the ozone formation. For these purposes, the emission rates for monoterpene and isoprene are measured for ten dominant individuals of conifers and broad-leaved trees, and the CMAQ and MM5 models are used. The research findings from this study are summarized as follows: The emission rate of monoterpene is significantly higher in conifers (0.29～1.24 ㎍ gdw-1hr-1) than that in broad leaved trees (0.1～0.2 ㎍ gdw-1hr-1), whereas the emission rate of isoprene is higher in broad leaved trees than that in conifers. Of all species of trees, Abies koreana shows the highest value in the emission rate for monoterpene and Quercus serrata also has the highest level in the emission rate for isoprene. The emission rates of monoterpene and isoprene are the highest in summer season. The peak of emission rates are appeared at the time of 13:00～14:00 when foliage temperature is high and photosynthesis is active. Emission of isoprene is stopped at nighttime due to the absence of light. There is a great difference between major components of monoterpene according to the species of trees. In particular, α-pinene, β-pinene, and β-phellandrene are dominant components in Pinus thunbergii and Pinus densiflora which are in the same genus, d-limonene in Abies koreana, and sabinene in Crytomeria japonica. On the other hand, a similar composition of monoterpene components is shown in broad leaved trees. By the results of computing the emission amount of BVOCs for Jeju area based on the CORINAIR process, Eighty five percentages of monoterpene emission are emitted from conifers and 15% of that are from broad leaved trees. Most of monoterpene emission is attributed to Pinus thunbergii (46.7%) and Crytomeria japonica (29.6%). The broad leaved trees have greatly contributed to the emission of isoprene. Especially, it can be seen that Quercus serrata plays a dominant role in emission of isoprene. The total amount of emission of BVOCs is estimated as 3,612 ton yr-1 in Jeju area. The amount of 1,846 ton yr-1 (51.1%) is attributed to conifers, 1,620 ton yr-1 (44.9%) to broad leaved tree, and 146 ton yr-1 (4.0%) to grassland. Of total emission amount of BVOCs, monoterpene accounts for 32.3% (1,166 ton yr-1), isoprene for 28.0% (1,012 ton yr-1), and OVOCs for 39.7% (1,434 ton yr-1). The emission amount of BVOCs computed by this study is less by 1,101 ton yr-1 (31.9%) than that estimated by other previous study. This means that it is important to survey the emission rate at real environment and gather the detailed data for the distribution of local species of trees on target region. It can be shown in the distribution of BVOCs in Jeju area that BVOCs is emitted 3,000～10,000 kg yr-1 from an altitude of 500m to the top of Halla Mt. with a dense forest, and less than 1,500 kg yr-1 below an altitude of 500 m. The emission amount of monoterpene is more than 1,500 kg yr-1 due to the influence by communities of Abies koreana at an altitude of 1,500 m or above and Pinus thunbergii and Crytomeria japonica at an altitude of 500～700 m. The emission amount of isoprene is 1,500～3,000 kg yr-1 at an altitude of 700～1,500 m with dense broad leaved trees and very little at an altitude of 1,500 m or above due to the absence of broad leaved trees. To analyze the impact of emission of BVOCs on ozone formation, the simulation is performed by using CMAQ model according to four scenarios based on weather conditions available to produce higher concentration of ozone without the influence of outer air mass in Jeju area. In Case 1 considered the impact of BVOCs emitted from the forests on ozone production, the simulated ozone concentrations are 91～94% of the concentrations actually measured at monitoring sites and diurnal patterns of simulated ozone concentrations are very similar to those of actual measurements of ozone. In Case 2 without consideration of the impact of BVOCs emitted from the forest, the simulated ozone concentrations are at 71～73% of the concentrations actually measured at monitoring sites. This means that the given conditions for real circumstances is not reflected in these results. When predicting the ozone concentration by assuming that there will be an increase in the emission of BVOCs from the vegetation in the future, it is predicted that the ozone concentration in the downtown area of Jeju city exceeds the air quality standard of 1-hr average concentration due to the increase in BVOCs emission up to 25% more than the present. In addition, if the emission of BVOCs is increased up to 50% in the future, the resilts of simulation shows that the areas exceeded the air quality standard of 1-hr average ozone concentration are enlarged to the suburbs of Jeju city and the central area of Seogwipo city.