Biogenic volatile organic compounds (VOCs) are a significant source of global secondary organic aerosol (SOA); however, quantifying their aerosol forming potential remains a challenge. This study ...presents smog chamber laboratory work, focusing on SOA formation via oxidation of the emissions of two dominant tree species from boreal forest area, Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies), by hydroxyl radical (OH) and ozone (O3 ). Oxidation of α-pinene was also studied as a reference system. Tetramethylethylene (TME) and 2-butanol were added to control OH and O3 levels, thereby allowing SOA formation events to be categorized as resulting from either OH-dominated or O3 -initiated chemistry. SOA mass yields from α-pinene are consistent with previous studies while the yields from the real plant emissions are generally lower than that from α-pinene, varying from 1.9% at an aerosol mass loading of 0.69 μg m-3 to 17.7% at 26.0 μg m-3 . Mass yields from oxidation of real plant emissions are subject to the interactive effects of the molecular structures of plant emissions and their reaction chemistry with OH and O3 , which lead to variations in condensable product volatility. SOA formation can be reproduced with a two-product gas-phase partitioning absorption model in spite of differences in the source of oxidant species and product volatility in the real plant emission experiments. Condensable products from OH-dominated chemistry showed a higher volatility than those from O3 -initiated systems during aerosol growth stage. Particulate phase products became less volatile via aging process which continued after input gas-phase oxidants had been completely consumed.
We measured the number concentrations and size distributions of aerosol particles and air ions with a differential mobility particle sizer and air ion spectrometer, respectively, during a roadside ...campaign conducted in Kuopio (Savilahti), Finland, between 16 June and 2 July 2004. The average cluster ion (0.3–1.8 nm) concentrations were quite low (around 320 cm–3 and 280 cm–3 for negative and positive ions) during the whole period. For comparison, cluster ion concentrations in a rural SMEAR II station in Hyytiälä, southern Finland, were at the same time almost three times higher. Negative intermediate ions (1.8–7.5 nm) reached maximum concentrations of 620 cm–3 in Kuopio, while the average concentrations were in the range 60–80 cm–3 depending slightly on the wind direction. Positive intermediate ion concentrations were lower. We observed higher amounts of the intermediate ions usually during rain but also during non-rain periods indicative of short-term secondary particle formation. Large ion (7.5–40 nm) concentrations (average values of 500–800 cm–3) were 2–3 times higher in Kuopio than at the SMEAR II station. Straightforward impact of traffic was observed when the wind blew from the road: an increase in the traffic density increased concentrations of large ions.
Peat dust emissions and particle concentrations at different distances from a milled peat production field were studied for two different harvesting methods. The dust emissions were found to be ...sporadic. The momentary PM2.5 concentrations, which varied up to 5 mg m–3 near the operation area, depended on the operation and weather conditions as well as peat composition. By using the Fugitive Dust Model, PM2.5 emission rates were estimated to range from 0.3 to 43 g s–1. Wind erosion increased the PM2.5 concentrations remarkably at wind speeds over 4 m s–1. Using time activity data of the different operational phases the lowest fine particle emissions were observed from the milling phase and the highest in the harvesting phases, respectively. As compared with the present EU daily limit value, the concentrations further from the peat production field were estimated to be low. However, short term negative influences on living conditions in the neighbourhood of peat production areas may be possible under certain environmental conditions.
In Kuopio, Finland, PM sub(2.5) concentrations were measured in the vicinity of a major road, and the data were used to test roadside emission and dispersion models. The samplers were placed at a ...height of 1.8 m on a line perpendicular to the road at distances of 12, 25, 52, and 87 m from the center line of the road. The traffic density on the road and on two minor roads was measured electronically continuously, and meteorological data from two local weather stations were obtained continuously. The regionally and long-range transported contribution to PM sub(2.5) concentrations, as well as the contributions of primary and non-exhaust vehicular emissions, and other sources were estimated at 41, 33, and 26%, respectively.
The performances of eight sampling devices were tested with mineral dusts in the laboratory and in a talc production plant. The IOM sampler was chosen as the reference method for inhalable dust, and ...the IOM samplers provided with the porous plastic foam media were used as the reference methods for both the thoracic and respirable aerosols. The other size-selective instruments tested included the Respicon virtual impactor, the optical GRIMM aerosol monitor, and a two-stage cascade impactor with cut points of 10 and 4 mum. The 37-mm cassettes were also included both as open- and closed-face versions. The study confirmed the usability of the IOM samplers for mineral dust, not only in its original version for the inhalable fraction but also its modified versions for the thoracic and respirable fractions. A high correlation with the two-stage impactor results is an indication of good reproducibility. The results increased the evidence that the 37-mm cassette is a poor indicator of inhalable aerosol. The concentrations obtained with both cassette methods were not only systematically too low but also showed large collection efficiency variability. Therefore, the results cannot be corrected by using correction factors. The concentrations of inhalable aerosol measured with the Respicon were generally low, but its performances for the thoracic and respirable fractions were closer to those for the reference samplers. The results also indicate that the GRIMM monitor is well-suited for such mineral dust determinations when very good accuracy is not required, but the immediate availability of the result is more important. PUBLICATION ABSTRACT
