北京森林BVOCs排放特征及对区域空气质量的影响

利用林业二类调查蓄积资料，广泛调研植物源挥发性有机物（BVOCs）排放因子的最新研究成果，运用光温影响模型对北京森林BVOCs排放特征进行研究，并分析其对区域空气质量的影响.结果显示，2015年北京森林BVOCs排放量平均值为27.97×10⁹g C/a，变化域值范围为（9.46~76.45）×10⁹g C/a，其中异戊二烯、单萜烯和其他VOCs贡献率分别为75.09%、15.62%和9.29%.不同树种间BVOCs排放量差异较大，杨树和栎树是主要的异戊二烯排放源，贡献率分别为63.16%和25.92%；油松是主要的单萜烯排放源，贡献率为40.90%.不同龄级林对BVOCs排放的贡献不同，中龄林贡献率最大，占总量的39.14%.BVOCs排放呈夏季高、冬季低的特征，春、夏、秋、冬排放量分别占全年的12.55%、77.48%、9.76%和0.21%.BVOCs对O₃生成潜势的贡献量为240.51×10⁹g，其中异戊二烯占92.66%，是主要的贡献者；对二次有机气溶胶（SOA）生成潜势的贡献量为1.73×10⁹g，异戊二烯和单萜烯分别占24.26%和75.73%.研究表明，北京森林BVOCs排放会导致大气年均SOA浓度增加0.94μg/m³，O₃浓度上升9.01μg/m³，特别是对夏季O₃污染具有较大贡献.建议城市绿化时应从有助于空气质量改善的角度考虑树种的VOCs排放能力.

Emission characteristics of VOCs from forests and its impact on regional air quality in Beijing

Emission characteristics of BVOCs from forests and its impact on regional air quality in Beijing were studied by analyzing the volume data of second-class forest resources survey in Beijing and investigating the BVOCs emission factors from relevant literatures. The results showed that the average BVOCs emissions from forest in Beijing were 27.97×10⁹g C/a, with a range of 9.46~76.45×10⁹g C/a. The contribution of isoprene, monoterpene and other VOCs (OVOCs) to total BVOCs emissions were 75.09%, 15.62% and 9.29%, respectively. The BVOCs emissions had significant species variation:poplar and quercus were the main species responsible for isoprene emission, contributing 63.16% and 25.92% to the total, respectively; Pinus tabulaeformis was the main species responsible for monoterpene emission, contributing 40.90% to the total. Forests of different age-class had different contributions to BVOCs emissions. Half-mature forest was the main emission source and contributed 39.14% to the total BVOCs emission from forests. The seasonal variations of BVOCs emissions were significant, and the emissions in spring, summer, autumn and winter accounted for 12.55%, 77.48%, 9.76% and 0.21% of the annual emissions, respectively. The ozone formation potential of BVOCs was 240.51×10⁹g, of which isoprene was the main contributor accounting for 92.66%. The secondary organic aerosol formation potential of BVOCs was 1.73×10⁹g, and the contributions of isoprene and monoterpene were 24.26% and 75.73%, respectively. This study indicated that BVOCs emissions form forest caused the annual atmospheric ozone concentrations to rise by 9.01μg/m³ and an increase of the annual atmospheric SOA concentrations by 0.94μg/m³. Especially, BVOCs emissions had relatively high contribution to ozone formation in summer. Therefore, the VOCs emissions capacity of species should be fully considered in urban greening, which would be conductive to improve air quality.