WINTERTIME MEASUREMENTS OF AEROSOL ACIDITY AND TRACE-ELEMENTS IN WUHAN, A CITY IN CENTRAL CHINA

A 2-week intensive ambient aerosol study was conducted in December 1988 in Wuhan (Hubei Province), a city of nearly 2 million located on the Yangtze River in central China (P.R.C.). This is an industrial region where soft coal burning is widespread, and emission controls for vehicles and industrial facilities are minimal. The sampling site was located in one of the civic centers where residential and commercial density is highest. An Andersen dichotomous sampler was operated with Teflon membrane filters to collect fine (d(p) < 2.5-mu-mad) and coarse (2.5 less-than-or-equal-to d(p) < 10-mu-mad) particles for total mass and element determinations. An annular denuder system (ADS) was used to collect fine fraction aerosols for analyses of ionic species including strong acidity (H+). The study was conducted between 18 and 30 December, which was rainless, consistently cool (3-10-degrees-C) and overcast, but without fog or acute stagnation. Fine particulate mass (PM, as mu-g m-3) averaged 139 (range 54-207); coarse PM averaged 86 (range 29-179). Trace element concentrations were also high. Crustal elements (Si, Al, Ca and Fe) were found primarily in the coarse fraction, while elements associated with combustion (S, K, Cl, Zn and Se) were enriched in the fine fraction. The concentrations of arsenic and selenium were evidence of a large source of coal burning, while vanadium levels (associated with fuel oil use) were not especially enriched. Despite the seemingly high PM loadings, ionic concentrations were not especially high. The average composition of soluble fine aerosol species (in neq m-3) were SO42-: 520 (range 180-980), NO3-: 225 (range 50-470), Cl-: 215 (range 20-640), and NH4+: 760 (range 280-1660). A deficit in accountable FP components (total mass compared to the total of ionic plus element masses) as well as the black appearance of collected materials indicate an abundance of carbonaceous aerosol, as high as 100-mu-g m-3. Aerosol acidity was negligible during most monitoring periods, H+: 14 (range 0-50 neq m-3, equivalent to 0-2.5-mu-g m-3 as H2SO4). Sulfur dioxide, measured by the West-Gaeke method for part of the study, concentrations were low. Although not directly measured, the aerosol measurements suggested that gaseous HCl (from refuse incineration) and NH3 (animal wastes) concentrations might have been high. Higher aerosol acidity might be expected if HCl sources were more prominent and not neutralized by local ammonia or other base components.