RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 10, ES2002, doi:10.2205/2007ES000260, 2008
Variations of trace gases, meteorological parameters, and their connection with aerosol formation in boreal forestsYu. S. Lyubovtseva Geophysical Center, Russian Academy of Sciences, Moscow, Russia L. Sogacheva, and M. Kulmala Department of Physical Sciences, University of Helsinki, Helsinki, FinlandContentsAbstract[1] The data of observations at Hyytiälä background station in 1997 - 2003 are analyzed for investigating the possible links between physical, chemical, and meteorological parameters for event and nonevent days for different seasons. The seasonal patterns of average trace gases concentrations (O3, H2O, NOx = NO + NO2, SO2 ), UV-A irradiation, temperature, relative humidity, condensational sinks are established and used for evaluating their influence on the seasonal dependence of formation and growth rates of particles in the nucleation mode. The condensational sinks are shown to play a crucial role in the chemical dynamics of the gaseous precursors and the aerosol particles. The variations of the sinks are mainly attributed to the humidification of the preexisting aerosol and thus strongly depend on the relative humidity. Introduction[2] Recent observations have provided impressive evidences that the particle formation processes and their further growth can be detected in different geographic locations and in absolutely diverse conditions. Long term data set on particle formation at a continental forest site (Hyytiälä, Southern Finland) display a strong seasonal variation on the number of occurrences of these events with a maximum during spring time and a minimum in midsummer. Annual variations of the particle growth rate during nucleation events in forest and rural locations also show a strong seasonal trend [Kulmala et al., 2004] with maximal and minimal particle growth rate 4 -17 nm/h (summer time) and 0.5 - 2 nm/h (winter time) respectively. [3] The particle formation in the atmosphere is a dynamic process. The combination of chemical, physical, and meteorological processes define the production rate of non-volatile substances that can then either nucleate or condense onto the surfaces of foreign particles. Because the chemical composition of newly born particles with the sizes 3 - 10 nm is still unknown, an information on the mechanisms, the sources, and the actual conditions of the particle formation can be only derived from the studies on correlations of various factors and the attempts of their subsequent classification. [4] The major goal of this presentation is to analyze the diurnal variations in different seasons and the long-term behavior of the trace gases concentrations (SO2, NO, NOx ), ozone level, relative and absolute humidity, and the meteorological parameters for examining the influence of these seasonal dependence on the aerosol concentration, the formation and growth rates of the particles in the nucleation mode. [5] Our analysis uses the data set on the parameters obtained during the period 1996 - 2003 at the Hyytiälä station. The station is located in the extended area of Scots pines dominant forests with the conditions typical for a background location. The hour average values of the studied concentrations were calculated for different seasons of each year and for the whole period of measurements. The average concentrations of trace gases, SO2, NOx, water vapor, ozone, and short wavelength irradiance UV-A (320-400 nm) as well as all necessary meteorological parameters were determined as averages over different periods for all days of observations and separately, for event and nonevent days. Results and Discussion
Winter
Spring
Summer
Conclusion[24] Practically all sources and sinks have a seasonal pattern. Seasonal variations of VOC connected with the biological activity of trees and VOC reach a maximum in summer time. Opposite seasonal variation are observed for SO 2. Maximal level of SO 2 is observed in winter and is stipulated by seasonal differences in the wind direction. Sinks of trace gases depend on the meteorological conditions: height of mixing layer (which is maximal in summer), losses on the surfaces (minimal in winter for snow cover), losses in the canopies (maximal in summer time), the influence of RH on the condensation sink. The seasonal variations formation particles is result from a balance of sources and sinks and demand a thorough analysis in future. ReferencesBonn, B., G Schuster, and G. K. Moortgat (2002), Influence of water vapor on the process of new particle formation during monoterpene ozonolysis, J. Phys. Chem. A, 106, 2869, doi:10.1021/jp012713p. [CrossRef] Buzorius, G., Ü. Rannik, P. Aalto, M. Dal Maso, E. D. Nilsson, K. E. J. Lehtinen, and M. Kulmala (2003), On particle formation prediction in continental boreal forest using micrometeorological parameters, J. Geophys. Res., 108, (D13), 4377, doi:10.1029/2002JD002850. [CrossRef] Kulmala, M., H. Vehkmäki, T. Petäjä, M. Dal Maso, A. Lauri, V. M. Kerminen, W. Birmili, and P. H. McMurry (2004), Formation and growth rates of ultrafine atmospheric particles: a review of observations, J. Aeosol Sci., 35, 143, doi:10.1016/j.jaerosci.2003.10.003. [CrossRef] Mäkela, J. M., M. Dal Maso, L. Pirjola, P. Keronen, L. Laakso, M. Kulmala, and A. Laaksonen (2000), Characteristics of the atmospheric particle formation events observed at a boreal forest site in Southern Finland, Boreal Env. Res., 5, 299. Pirjola, L. (1999), Effect of the increased UV radiation and biogenic VOC emissions on ultrafine sulphate aerosol formation, J. Aerosol Sci., 30, 355, doi:10.1016/S0021-8502(98)00065-2. [CrossRef] Suni, T., and M. Dal Maso, et al. (2003), Air temperature triggers of the recovery of evergreen boreal forest photosynthesis in spring, Global Change Biology, 9, 1410, doi:10.1046/j.1365-2486.2003.00597.x. [CrossRef] Received 18 January 2008; accepted 1 February 2008; published 22 February 2008. Keywords: trace gases, nucleation, seasonal variation, atmospheric nanoaerosols. Index Terms: 0300 Atmospheric Composition and Structure; 0305 Atmospheric Composition and Structure: Aerosols and particles; 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties. ![]() Citation: 2008), Variations of trace gases, meteorological parameters, and their connection with aerosol formation in boreal forests, Russ. J. Earth Sci., 10, ES2002, doi:10.2205/2007ES000260. (Copyright 2008 by the Russian Journal of Earth SciencesPowered by TeXWeb (Win32, v.2.0). |