Atmospheric aerosol over Alaska: 1. Spatial and seasonal variability

Aerosol chemical composition data for seven National Park Service locations in Alaska for the period from 1986 to 1995 were analyzed. Data for elements, black carbon, and total mass were obtained for samples of atmospheric particles less than 2.5 μm in diameter. Assuming that all elemental aerosol S was from SO4=, concentrations of excess (nonmarine) sulfate (XSO4=) were calculated by subtraction of the sea salt SO4= mass fraction to Na and observed Na concentrations. Mass concentration of XSO4= ranged from 0.01 to 3.9 μg m−3, and mass concentration of black carbon (BC) ranged from 0.01 to 5 μg m−3. Seasonal variations with maxima during the winter/spring season and minima in the summer for most of the sites in Alaska were observed for the XSO4= but not for the BC and the fine mass concentration. The seasonal variations of XSO4= concentration were always higher in northwestern Alaska. BC concentration in central Alaska peaked during the summertime because of the high BC emission from forest fires. The Pb concentration in central Alaska shows a negative trend over the timescale of measurements. It is concluded that all of the sites experience aerosol pollution from long distance, regional, and local sources. Seasonal variations of the XSO4= concentration are related to the seasonal variations in long-range transport of midlatitudinal S emissions, to the varying rate of photochemical SO4= fine aerosol production and to fine aerosol removal processes in the troposphere. The spatial distribution of XSO4= shows a strong northwest to southeast negative gradient that can be associated with the long-range transport of anthropogenic aerosol from pollution sources located to the north or northwest of Alaska.

[1]  L. Barrie,et al.  The influence of mid-latitudinal pollution sources on haze in the Canadian arctic , 1981 .

[2]  John M. Miller.  A five-year climatology of five-day back trajectories from Barrow, Alaska , 1981 .

[3]  K. Rahn,et al.  Atmospheric bromine in the Arctic , 1983 .

[4]  G. Shaw,et al.  Long-range tropospheric transport of pollution aerosols into the Alaskan Arctic , 1984 .

[5]  R. Schnell,et al.  Vertical and horizontal characteristics of Arctic haze during AGASP: Alaskan Arctic , 1984 .

[6]  L. Barrie,et al.  The oxidation rate and residence time of sulphur dioxide in the arctic atmosphere , 1984 .

[7]  T. Iversen,et al.  Arctic air pollution and large scale atmospheric flows , 1985 .

[8]  G. Shaw.  Aerosol measurements in central Alaska, 1982–1984 , 1985 .

[9]  L. Barrie,et al.  Arctic air pollution: An overview of current knowledge , 1986 .

[10]  P. Crutzen,et al.  Ozone destruction and photochemical reactions at polar sunrise in the lower Arctic atmosphere , 1988, Nature.

[11]  G. Shaw.  Chemical air mass systems in Alaska , 1988 .

[12]  A. Clarke.  Aerosol light absorption by soot in remote environments , 1989 .

[13]  W. Raatz.  An anticyclonic point of view on low-level tropospheric long-range transport , 1989 .

[14]  The flux of anthropogenic sulphur into the arctic from mid-latitudes in 1979/80 , 1989 .

[15]  L. Barrie,et al.  Chemical components of lower tropospheric aerosols in the high arctic: Six years of observations , 1990 .

[16]  P. Shepson,et al.  Depletion of lower tropospheric ozone during arctic spring : the Polar Sunrise Experiment 1988 , 1990 .

[17]  Sheldon Landsberger,et al.  Distribution characteristics of trace elements and ionic species of aerosol collected at Canadian high arctic , 1991 .

[18]  G. Shaw.  Aerosol chemical components in Alaska air masses: 1. Aged pollution , 1991 .

[19]  H. Horvath.  Atmospheric light absorption : a review , 1993 .

[20]  Sheldon Landsberger,et al.  Qualitative determination of source regions of aerosol in Canadian high Arctic , 1993 .

[21]  L. Barrie,et al.  Biogenic sulfur aerosol in the arctic troposphere: 1. contributions to total sulfate , 1993 .

[22]  L. Barrie,et al.  Atmospheric observations of aerosol black carbon, carbon dioxide and methane in the high arctic , 1994 .

[23]  W. Malm,et al.  Spatial and seasonal trends in particle concentration and optical extinction in the United States , 1994 .

[24]  P. Shepson,et al.  Organic and inorganic bromine compounds and their composition in the Arctic troposphere during polar sunrise , 1994 .

[25]  Ola M. Johannessen,et al.  The Arctic's shrinking sea ice , 1995, Nature.

[26]  G. Shaw.  The Arctic Haze Phenomenon , 1995 .

[27]  T. Cahill,et al.  Measurement of Aerosol Absorption Coefficient from Teflon Filters Using Integrating Plate and Integrating Sphere Techniques , 1995 .

[28]  P. Hopke,et al.  The ratio of aerosol optical absorption coefficients to sulfur concentrations, as an indicator of smoke from forest fires when sampling in polar regions , 1996 .

[29]  P. Paatero,et al.  Atmospheric aerosol over Alaska: 2. Elemental composition and sources , 1998 .

[30]  Philip K. Hopke,et al.  Identification of Source Nature and Seasonal Variations of Arctic Aerosol byPositive Matrix Factorization , 1999 .