Real-time measurements of acidic trace gases (HCl, HNO(3), HONO, and SO(2)), ammonia, and water-soluble ions in PM(2.5) were conducted at Xinken, a coastal site downwind of Guangzhou, from 4 October to 4 November 2004, as part of the Pearl River Delta (PRD) intensive field campaign. The average concentrations of HCl, HONO, HNO(3), SO(2), and NH(3) are 2.8, 2.9, 6.3, 55.4, and 7.3 mu g m(-3) respectively, and 2.4, 7.2, 24.1, and 9.2 mu g m(-3) for Cl(-), NO(3)(-), SO(4)(2-), and NH(4)(+) in PM(2.5). The diurnal variations of both HCl and HNO(3) showed higher concentrations during daytime and lower concentrations at night, and aerosol Cl(-) and NO(3)(-) showed an opposite diurnal patterns to HCl and HNO(3). The diurnal variation of NH(3) showed the similar pattern to that of aerosol NH(4)(+) with lower concentration during daytime and higher concentration at night. The average concentration of SO(2) during daytime was higher than that at night. The transportation of urban plumes to the sampling site could explain the higher concentration of SO(2) during daytime. HONO showed a clear diurnal variation with lower concentration during daytime and higher concentration at night. The HONO concentrations were positively correlated with the particle surface area concentrations, suggesting the formation of HONO through the heterogeneous conversion on particle surfaces could be significant. The ionic charge balance analysis included the cations derived from filter measurements indicates that the contribution of the cations in fine particle (PM(1.8)) to the charge balance is not pronounced. The theoretical equilibrium constant (K(e)) of NH(4)NO(3) is higher than the observed concentration product (K(m) = [NH(3)] x [HNO(3)]) during daytime, and lower than K(m) at night. This indicates that the atmospheric conditions during the sampling period did not favor the formation of NH(4)NO(3) during daytime. (c) 2008 Elsevier Ltd. All rights reserved.
Continuous measurements of aerosol number size distribution in the range of 3 nm-10 mu m were performed in Pearl River Delta (PRD), China. These measurements were made during the period of 3 October to 5 November in 2004 at rural/coastal site, Xinken (22 degrees 37'N, 113 degrees 35'E, 6m above sea level), in the south suburb of Guangzhou City (22 degrees 37'N, 113 degrees 35'E, 6m abovesea level), using a Twin Differential Mobility Particle Sizer (TDMPS) combined with an Aerodynamic Particle Sizer (APS). The aerosol particles at Xinken were divided into four groups according to the observation results: nucleation mode particles (3-30 nm), Aitken mode particles (30-130 nm), accumulation mode particles (130-1000 nm) and coarse mode particles (1-10 mu m). Concentrations of nucleation mode, Aitken mode and accumulation mode particles were observed in the same order of magnitude (about 10,000 cm(-3)), among which the concentration of Aitken mode particle was the highest. The Aitken mode particles usually had two peaks: the morning peak may be caused by the land-sea circulation, which is proven to be important for transporting aged aerosols back to the sampling site, while the noon peak was ascribed to the condensational growth of new particles. New particle formation events were found on 7 days of 27 days, the new particle growth rates ranged from 2.2 to 19.8 nm h(-1) and the formation rates ranged from 0.5 to 5.2 cm(-3) s(-1), both of them were in the range of typical observed formation rates (0.01-10 cm(-3) s(-1)) and typical particle growth rates (1-20 nm h(-1)). The sustained growth of the new particles for several hours under steady northeast wind indicated that the new particle formation events may occur in a large homogeneous air mass. (c) 2008 Elsevier Ltd. All rights reserved.
Previous research in the Taihu Lake Region (TLR) of China found high levels of atmospheric organochlorine pesticides (OCPs). To understand the sources and the environmental behaviors of these OCPs in the TLR, research on air-water gas exchange was performed in 2004. Hexachlorocyclohexanes (HCHs), DDT related compounds (DDTs), cis-chlordane (CC), trans-chlordane (TC), heptachlor (HEPT), and alpha-endosulfan in both air and water samples were analyzed, and air-water gas exchange fluxes of these compounds were calculated. The net volatilization flux of alpha-HCH was 58 ng m(-2) day(-1), suggesting that the residue of technical HCH in the lake sediment might have been an important source of alpha-HCH to the air of this region after the ban of technical HCH two decades ago. The main components of technical chlordane, TC, CC, and HEPT, each had net volatilization fluxes > 230 ng m(-2) day(-1), suggesting that waste discharge from manufacturing plants in the upper region was the main source of chlordane to the lake. Unlike alpha-HCH and chlordane, o,p'-DDT and alpha-endosulfan had net deposition fluxes, suggesting that these compounds were transported through the atmosphere from land sources and then deposited into the lake. The correlation between air concentrations and ambient air temperature indicated that the current sources of o,p'-DDT and alpha-endosulfan were from land; alpha-HCH and chlordane were mainly from the lake.