Ambient Aerosol and its Carbon Content in Gainesville, a Mid-Scale City in Florida Paradee Chuaybamroong & Kimberleigh Cayse & Chang-Yu Wu & Dale A. Lundgren Received: 1 December 2005 / Accepted: 7 June 2006 # Springer Science + Business Media B.V. 2006 Abstract Ambient aerosols were collected during 2000–2001 in Gainesville, Florida, using a micro- orifice uniform deposit impactor (MOUDI) to study mass size distribution and carbon composition. A bimodal mass distribution was found in every sample with major peaks for aerosols ranging from 0.32 to 0.56 μm, and 3.2 to 5.6 μm in diameter. The two distributions represent the fine mode (<2.5 μm) and the coarse mode (>2.5 μm) of particle size. Averaged over all sites and seasons, coarse particles consisted of 15% carbon while fine particles consisted of 22% carbon. Considerable variation was noted between winter and summer seasons. Smoke from fireplaces in winter appeared to be an important factor for the carbon, especially the elemental carbon contribution. In summer, organic carbon was more abundant. The maximum secondary organic carbon was also found in this season (7.0 μgm −3 ), and the concentration is between those observed in urban areas (15–20 μgm −3 ) and in rural areas (4 –5 μgm −3 ). However, unlike in large cities where photochemical activity of anthro- pogenic emissions are determinants of carbon com- position, biogenic sources were likely the key factor in Gainesville. Other critical factors that affect the distribution, shape and concentration were precipita- tion, brushfire and wind. Keywords mass size distribution . elemental carbon . organic carbon . total carbon . MOUDI 1 Introduction Elevated levels of ambient particulate matters have been found to correlate with a variety of environmen- tal and health effects. Examples include increased hospital admissions due to cardiopulmonary illness (Linn, Szlachcic, Gong, Kinney, & Berhane, 2000) and degradation in visibility (EPA, 1996), among others. Among various aerosol properties that deter- mine their effects, particle size and composition are the two major ones (Dodd, Ondov, Tuncel, Dzubay, & Stevens, 1991). Particulate matter with an aerody- namic diameter less than 10 μm (PM 10 ) can pass beyond the larynx and reach the thorax or chest, while ultrafine particles (<0.1 μm) are deposited in the alveolar region by Brownian motion or diffusion (Hinds, 1999). If the deposited particles are soluble, Environ Monit Assess DOI 10.1007/s10661-006-9336-0 P. Chuaybamroong (*) Department of Environmental Science, Faculty of Science and Technology, Thammasat University, Pathumthani, 12121, Thailand e-mail: cparad@kku.ac.th K. Cayse Department of Soil and Water Science, University of Florida, Gainesville, FL 32611, USA C.-Y. Wu : D. A. Lundgren Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611, USA