Black carbon in a continental semi-arid area of Northeast China and its possible sources of fire emission

Surface continuous measurements on black carbon (BC) were performed at Tongyu (44.42 degrees N, 122.87 degrees E) from March to December 2008. Tongyu is an international reference site of semi-arid climate and environment researches, located in a continental semi-arid area of northeastern China. Mass concentrations and potential contributing sources of BC are discussed for the sampling site. Hourly BC concentrations ranged from 77.61 ng m(-3) to 59.55 mg m(-3) with an average of 2.52 mg m(-3), showing a clear seasonal pattern with high values in spring, fall, and winter and low values in summer. Events of high BC concentrations occurred frequently in spring as a result of long-range transport of polluted air masses from the north, northwest, and south in the atmosphere over the Asian continent. The Yangtse River Delta (YRD) and China Anhui Province, the North China Plain (NCP), Northeast China, the Mongolian boundary near China and Russia, Middle Asia, and some areas of Russian Far East were major potential contribution sources for the observed pollutants. The region between Jiangsu Province and Anhui Province of China and the boundary regions between China and Russian Primorskiy and Khabarovskiy were possible source areas of fire emissions having great contributions to high BC levels at Tongyu. The region between Jiangsu Province and Anhui Province of China was the most important anthropogenic fire source of agricultural residue burning outflows.