科研成果 by Year: 2004

In order to characterize sources of fine carbonaceous aerosols, PM2.5 aerosols were sampled at 5 sites in forest, tunnel, urban, rural., and forest/urban areas in the Lower Fraser Valley (LFV) during the Pacific 2001 Air Quality Study. All sample filters were analyzed for cis-pinonic acid and n-fatty acids. cis-Pinonic acid varied from 0.6-46.5 ng m(-3) at the sites in the forest, rural and forest/urban mixing area, and was low, from < detection limit to 6.5 ng m(-3) at the tunnel and 0.3 to 20.4 ng m(-3) at the urban site. It showed consistent day-night differences at all locations, and was linearly correlated with alpha-pinene in forest areas. At the elevated mixing forest/urban site, the day-night pattern showed evidence of nighttime source of the acid. Straight-chain n-fatty acids on the aerosols showed evidence of the light-duty automobile source at the tunnel, with the highest concentration of all sites and a carbon number distribution with low CPI values. In the forest, the acids were the second highest of all sites, and the CPI value for the acids was the highest of all sites, indicating direct forest emissions. At other locations the n-fatty acids showed impacts from these sources, judging from the carbon number distributions. At the urban sites, there was evidence of meat cooking emissions contribution to the n-fatty acids. It was found that unsaturated n-fatty acids may be used as an indicator of the apparent ``age'' of the acids in aerosols, and that a photochemical half-life of 5 h was derived based on the comparison of the day and nighttime C-18:1/C-18:0 ratios at the sites. (C) 2004 Elsevier Ltd. All rights reserved.

Measurements of a number of aerosol properties and trace gases were conducted at Golden Ears Provincial Park (GE park), near the town of Maple Ridge, B.C., Canada from 6th to 11th of August 2001, just prior to the beginning of the main Pacific 2001 study. The measurements were intended to help with the characterization of the particulate matter (PM) in the forest that borders the northern side of the Lower Fraser Valley (LFV). The concentrations of inorganic ions in the particles decreased after 8th August, while the organic mass concentrations in the particles increased after 8th August. Throughout the study, organic carbon (OC) was the single highest component of the aerosol, and after 8th August, OC comprised about 90% of the particle composition. During the daytime, there was a clear anthropogenic influence from upslope flow driven by the sea breeze. The mixing ratio of monoterpenes increased overnight, when the winds were from the forests to the north but the cis-pinonic acid increased during the day, along with the anthropogenic tracers, suggesting that the oxidation of monoterpenes occurred with the help of anthropogenic oxidants. The particle volume data showed increases often corresponding with decreases in monoterpenes. A steady increase in particle volumes resulted from condensation of OC on the particles, and despite an increase in water soluble organic carbon (WSOC) the effectiveness of the OC at absorbing water for relative humidity (RH) values less than or equal to90% was low relative to sulphate. (C) 2004 Elsevier Ltd. All rights reserved.

High-resolution size-resolved mass concentration of organic and inorganic species present in/on sub-micron particles measured during the PACIFIC 2001 field study in the Lower Fraser Valley (LFV) are presented. The measurements of major particulate species (organics, sulfate, nitrate and ammonium) were made in situ and in real time at three different sites representing urban (Slocan Park), semi-rural (Sumas) and rural (Langley) areas, using two Aerodyne aerosol mass spectrometers (AMSs). The total non-refractory PM1.0 mass concentrations at the three sites were found to range from 0.12 to 24.50 mug m(-3), with an average concentration of 4.76 mug m(-3.) A large variability in aerosol composition was observed in the LFV, depending on meteorological conditions. Generally, during southwesterly wind conditions, inorganic species accounted for 50% of total mass loadings in the LFV, while during stagnant conditions organic species made up the majority of the particle mass. The organic aerosol species exhibit a bimodal size distribution, while the inorganic species are in most cases confined to the accumulation mode centered around 400 nm. Background sulfate levels of similar to 1 mug m(-3) were observed in the LFV during the entire campaign. Transport is found to be an important factor controlling the composition of sulfate in the LFV. Several photochemical events leading to the observation of substantial increases of sulfate in the LFV were also identified. Many of these events involve sulfate-dominated growth of small particles and appear to occur on a regional scale within the LFV. (C) 2004 Elsevier Ltd. All rights reserved.

The Pacific 2001 Air Quality Study was a major program on ambient particulate matter carried out in the Lower Fraser Valley. This paper provides an overview of the study and gives accounts of the measurements in each major components of the field measurement program, including ground sites specifically targeted on traffic emissions, urban mixing, urban to rural transition, biogenic emissions from forest, and a mixture of urban and forest, and an airborne measurement program to link the ground based components. A summary of major findings is given in the paper, along with a general background for the papers in this issue. (C) 2004 Elsevier Ltd. All rights reserved.