Correlation of black carbon aerosol and carbon monoxide in the high-altitude environment of Mt. Huang in Eastern China
Understanding the relationship between black carbon (BC) and carbon\nmonoxide (CO) will help improve BC emission inventories and the\nevaluation of global/regional climate forcing effects. In the present\nwork, the BC (PM1) mass concentration and CO mixing ratio were\ncontinuously measured at a high-altitude background station on the\nsummit of Mt. Huang (30.16 degrees N, 118.26 degrees E, 1840ma.s.l.).\nAnnual mean BC mass concentration was 1004.5 +/- 895.5 ng m(-3) with\nmaxima in spring and autumn, and annual mean CO mixing ratio was 424.1\n+/- 159.2 ppbv. A large increase of CO was observed in the cold season,\nimplying the contribution from the large-scale domestic coal/biofuel\ncombustion for heating. The BC-CO relationship was found to show\ndifferent seasonal features but strong positive correlation (R > 0.8).\nIn Mt. Huang area, the Delta BC/Delta CO ratio showed unimodal diurnal\nvariations and had a maximum during the day (09:00-17:00 LST) and\nminimum at night (21:00-04:00 LST) in all seasons, indicating the impact\nof planetary boundary layer and the intrusion of clean air masses from\nthe high troposphere. Back trajectory cluster analysis showed that the\nDelta BC/Delta CO ratio of plumes from the Eastern China (Jiangsu,\nZhejiang provinces and Shanghai) was 8.8 +/- 0.9 ng m(-3) ppbv(-1).\nTransportation and industry were deemed as controlling factors of the\nBC-CO relationship in this region. The Delta BC/Delta CO ratios for air\nmasses from Northern China (Anhui, Henan, Shanxi and Shandong provinces)\nand southern China (Jiangxi, Fujian and Hunan provinces) were quite\nsimilar with mean values of 6.5 +/- 0.4 and 6.5 +/- 0.2 ng m(-3)\nppbv(-1) respectively. The case studies combined with satellite\nobservations demonstrated that the Delta BC/Delta CO ratio for biomass\nburning (BB) plumes were 10.3 +/- 0.3 and 11.6 +/- 0.5ng m(-3) ppbv(-1),\nsignificantly higher than those during non-BB impacted periods. The loss\nof BC during transport was also investigated on the basis of the Delta\nBC/Delta 1CO-RH (relative humidity) relationship along air mass\npathways. The results showed that BC particles from Eastern China area\nwas much more easily removed from atmosphere than other inland regions\ndue to the higher RH along transport pathway, implying the importance of\nchemical compositions and mixing states on BC residence time in the\natmosphere.