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PM2.5 aerosol sampling for collection of 24 h samples was carried out every day from Qinghai Lake (3200m a.s.l.),a remote continental site in the northeastern part of Tibetan Plateau from July to August 2010.To better understand the production of water-soluble organic aerosols,the samples were analyzed for water-soluble dicarboxylic acids (C2-C11) and related compounds (ketocarboxylic acids and α-dicarbonyals),as well as organic carbon (OC),elemental carbon (EC),water-soluble organic carbon (WSOC),and water-soluble inorganic ions.Distributions of dicarboxylic acids and related compounds were characterized by a predominance of oxalic acid (29.3 – 347.6 ng m-3,148.2 ± 83.9 ng m-3) followed by malonic (9.3 – 77.6 ng m-3,27.2 ± 15.5 ng m-3) and succinic (3.6 – 29.3 ng m-3,14.5 ± 8.0 ng m-3) acids.The average contributions of diacids,ketoacids and dicarbonyls to WSOC were 44.1%,1.3%,and 0.4 %,respectively.They were several times higher than those reported in north-western cities from which air masses were transported to the Qinghai Lake,indicating an importance of photochemical processing of aerosols during a long-range transport.The diacids/WSOC and C9/diacids ratios were higher than those reported previously in different atmosphere aerosols,which may indicate that the local aerosols were chiefly influenced by the biomass burning (herbages and dung) and photochemical oxidations were enhanced because of the stronger solar radiation.This study demonstrated that diacids were primarily produced by the secondary photochemical oxidation of organic pollutants and ω-oxoacids were likely intermediates to the production of dicarboxylic acids.