Organic and inorganic aerosol compositions in Ulaanbaatar, Mongolia, during the cold winter of 2007 to 2008: Dicarboxylic acids, ketocarboxylic acids, and α‐dicarbonyls

To investigate the distributions and sources of water‐soluble organic acids in the Mongolian atmosphere, aerosol samples (PM 2.5 , n = 34) were collected at an urban site (47.92°N, 106.90°E, ∼1300 m above sea level) in Ulaanbaatar, the capital of Mongolia, during the cold winter. The samples were analyzed for water‐soluble dicarboxylic acids (C 2 –C 12 ) and related compounds (ketocarboxylic acids and α ‐dicarbonyls), as well as organic carbon (OC), elemental carbon, water‐soluble OC, and inorganic ions. Distributions of dicarboxylic acids and related compounds were characterized by a predominance of terephthalic acid (tPh; 130 ± 51 ng m −3 , 19% of total detected organic acids) followed by oxalic (107 ± 28 ng m −3 , 15%), succinic (63 ± 20 ng m −3 , 9%), glyoxylic (55 ± 18 ng m −3 , 8%), and phthalic (54 ± 27 ng m −3 , 8%) acids. Predominance of terephthalic acid, which has not been reported previously in atmospheric aerosols, was mainly due to uncontrolled burning of plastic bottles and bags in home stoves for heating and waste incineration during the cold winter. This study demonstrated that most of the air pollutants were directly emitted from local sources such as heat and power plants, home stoves, and automobiles. Development of an inversion layer (<700 m above ground level) over the basin of Ulaanbaatar accelerated the accumulation of pollutants, causing severe haze episodes during the winter season.