Correlation of black carbon aerosol and carbon monoxide concentrations measured in the high-altitude environment of Mt. Huangshan, Eastern China
1Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Japan
2State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
3Institutes of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Abstract. Understanding the relationship between black carbon (BC) and carbon monoxide (CO) will help improve BC emission inventories and the evaluation of global/regional climate forcing effects. In the present work, the BC (PM1) and CO mixing ratio was continuously measured at a~high-altitude background station on the summit of Mt Huangshan between 2006 and 2009. Annual mean BC concentration was 654.6 ± 633.4 ng m−3 with maxima in spring and autumn, when biomass was burned over a large area in Eastern China. The yearly averaged CO concentration was 446.4 ± 167.6 ppbv, and the increase in the CO concentration was greatest in the cold season, implying that the large-scale domestic coal/biofuel combustion for heating has an effect. The BC–CO relationship was found to have different seasonal features but strong positive correlation (R > 0.8). Back trajectory cluster analysis showed that the ΔBC/ΔCO ratio of plumes from the Yangtze River Delta region was 6.58 ± 0.96 ng m−3 ppbv−1, which is consistent with result from INTEX-B emission inventory. The ΔBC/ΔCO ratios for air masses from Northern, Central Eastern and Southern China were 5.2 ± 0.63, 5.65 ± 0.58 and 5.21 ± 0.93 ng m−3 ppbv−1, respectively. Over the whole observation period, the ΔBC/ΔCO ratio had unimodal diurnal variations and had a maximum during the day (09:00–17:00 LST) and minimum at night (21:00–04:00 LST) in spring, summer, autumn and winter, indicating the effects of the intrusion of clean air mass from the high troposphere. The case study combined with measurements of urban PM10 concentrations and satellite observations demonstrated that the ΔBC/ΔCO ratio for a plume of burning biomass was 12.4 ng m−3 ppbv−1 and that for urban plumes in Eastern China was 5.3 ± 0.53 ng m−3 ppbv−1. Transportation and industry were deemed as controlling factors of the BC–CO relationship and major contributions to atmospheric BC and CO loadings in urban areas. The loss of BC during transportation was also investigated on the basis of the ΔBC/ΔCO–RH relationship along air mass pathways, and the results showed that 30–50% BC was lost when air mass traveled under higher RH conditions (>60%) for 2 days.