摘要
黑碳(black carbon, BC)气溶胶源自化石燃料和生物质的不完全燃烧,是重要的大气和气候污染物.稳定碳同位素(13C)和放射性碳同位素(14C)是目前进行大气BC来源定量解析最为准确和客观的手段之一.本文重点概述了13C和14C溯源的基本原理和我国大气环境BC源解析的最新进展.从目前13C和14C的分析结果看,我国大气环境BC的最大排放源是化石燃料的不完全燃烧,但生物质燃烧的贡献也可以达到20%~50%,值得进一步重视.化石源对BC的贡献表现出"夏高冬低"季节特征,突显了冬季生物质燃烧对大气环境BC的重要影响.利用14C对左旋葡聚糖的源示踪能力进行了评估,发现左旋葡聚糖在夏季可以发生严重的大气降解,不宜用于定量示踪大气环境BC的排放源.最后,本文总结了目前我国BC排放清单存在的不确定性情况,指出碳同位素技术可以在BC清单准确性提高上发挥重要作用,从而进一步加深目前科学界对BC环境和气候效应的认识.
Black carbon(BC) aerosol derived from incomplete combustion of fossil fuel(e.g., coal and liquid petroleum) and biomass(e.g., agricultural residue, biofuel, and forest) is an important atmospheric pollutant globally. Besides presenting potential risks to public health, BC strongly absorbs solar radiation, decreases atmospheric visibility, heats the air, and is thought to be a key driver of climate warming. However, there is a large discrepancy between observations and models of the source apportionment and climate forcing of atmospheric BC globally, due to uncertain emission estimates.Stable carbon(13C) and radiocarbon(14C) isotope measurements are some of the most objective and accurate tools for apportioning atmospheric BC into key emission sources due to their unique fingerprint features. This review focuses on the principle of source apportionment for BC using 13C and 14C measurements, and the recent important progress in China, one of the largest emitters of BC. As expected, fossil fuel combustion is the largest contributor(70%-90%) of BC in many Chinese cities, mainly due to the huge consumption of coal and petroleum. However, the impact of biomass burning on BC can reach ~50% in some cities and even higher(~70%) in some remote sites, strongly reflecting the regional features of BC emission sources in China. Moreover, the largest and smallest contributions of fossil fuel combustion to BC are generally in summer and winter, respectively, highlighting the important influence of biomass burning on atmospheric BC during the cold season. The combined 13C and 14C measurements show that atmospheric BC in Northern China is mainly associated with coal combustion, followed by the burning of petroleum and biomass, which is very different from other regions where BC is typically dominated by petroleum burning. This implies that coal combustion is much more common and intensive in Northern China than in other regions. A strong correlation(R2= 0.81) is observed between the 14C signal and atmospheric levoglucosan concentration in winter, while the correlation is very weak(R2= 0.19) in summer. These results indicate that levoglucosan is chemically stable in the cold, but is degraded to a large extent in the atmosphere in summer. Compared with the levoglucosan concentration in winter, we roughly estimate that ~24% and ~70% of levoglucosan would be chemically degraded in spring and summer, respectively, which is consistent with chamber-based results(30%–75%). Therefore, we confirm that levoglucosan cannot quantify the impact of biomass burning on atmospheric BC in hot seasons.The source apportionment of BC based on emission-inventory technology is variable. In China, the contribution of biomass burning to BC could be as low as ~20% or as high as ~50%, depending on the emission inventory. Given the excellent ability of13C and 14C isotopes to quantify atmospheric BC, this review notes that a combined 13C and 14C measurement technique can serve as a good "referee" to guide the improvement of the BC emission inventory and deepen our understanding of the environmental and climatic effects of BC aerosols. Future research should(1) establish a 13C-BC database for different combustion-related emission sources and regions,(2) bridge the emission inventory of BC and isotope-based observations using atmospheric chemistry models,(3) comprehensively explore the atmospheric stability of levoglucosan using carbon isotopes, and(4) build an atmospheric observation network for BC carbon isotopes covering urban, rural, and remote areas in China.
作者
姜帆
刘俊文
黄志炯
郑君瑜
张干
Fan Jiang;Junwen Liu;Zhijiong Huang;Junyu Zheng;Gan Zhang(Institute of Environmental and Climate Research,Jinan University,Guangzhou 511443,China;State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Guangdong-Hongkong-Macao Joint Laboratory of Collaborative Innovation for Environmental Quality,Jinan University,Guangzhou 511443,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2020年第35期4095-4106,共12页
Chinese Science Bulletin
基金
国家自然科学基金(41877349,41603096,41430645)资助。
关键词
黑碳气溶胶
稳定碳同位素
放射性碳同位素
源解析
排放清单
black carbon aerosol
stable carbon isotope
radiocarbon isotopes
source apportionment
emission inventory
