Characterization of Forty Seven Years of Particulate Chemical Composition in the Finnish Arctic.

摘要

Forty seven years of weekly total suspended particle filters collected at Kevo, Finland from October 1964 through 2010 by the Finnish Meteorological Institute were analyzed for near-total trace elements, soluble trace elements, black carbon (BC), and major ions and methane sulfonic acid (MSA). Kevo is located in Northern Finland, 350 km north of the Arctic Circle. The samples from 1964-1978 were collected with Whatman 42 cellulous filters and the samples from 1979-2010 collected on Whatman GF/A glass-fiber filters. A portion of the filters was microwave acid-digested (ad) and analyzed for near-total trace elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Another portion was water extracted (we) and analyzed for soluble trace elements by ICP-MS and ionic species by ion chromatography (IC). Black carbon (BC) was determined using optical and thermal optical techniques at SUNY Albany. A clear seasonal trend with winter/spring maxima and summer minima is observed for most species attributed to enhanced transport of pollutants from anthropogenic mid-latitude sources to the Arctic in the winter and early spring. Compared to more remote Arctic sampling sites, species of anthropogenic origin (V, Co, Cu, Ni, As, Cd, Pb, SO4) have significantly higher concentrations and a less pronounced seasonality. High concentrations of Cu (14.1 ng/m3), Ni (0.97 ng/m3), and Co (0.04 ng/m3) indicate the influence of non-ferrous metal smelters on the Kola Peninsula, although Cu unexpectedly did not correlate with Ni or Co. Ni and Co were highly correlated. Significant long-term decreasing trends were detected for most species. All constituents except Sn-ad, Re-ad, Sn-we, Mo-we, V-we, have significant (p < 0.001) decreasing trends from 1964-2010. The largest decreases were Sb (-3.90 %/yr), Pb (-3.87 %/yr), Mn (-3.45 %/yr), Cd (-3.42 %/yr), and Ca (-3.13 %/yr ). As, Pb, and Cd concentrations at Kevo were consistent with the reported time-trends of European emissions inventories. Pb concentrations at Kevo have dramatically decreased (92%) in the past 47 years due to the reduced use of leaded gasoline in automobiles. Non sea salt SO4 concentrations were found to have a very similar trend to European and Former Soviet Union SO2 emissions. SO4 concentrations declined dramatically in the early 1990s a result of the collapse of the Soviet Union. Potential source contribution function (PSCF) analysis was used to estimate source locations of the species. PSCF plots for anthropogenic species (V, Cd, Mn, Mo, Sb, Tl, W, and SO4) suggest source areas predominantly in Eastern Europe, European Russia, and the Baltics. Markers of stationary fuel combustion (V, Mn, Mo, Sb, Se, Tl, and SO4) also pointed towards possible source regions in the Pechora Basin and Ural industrial areas in Russia, and near gas and oil fields in western Kazakhstan. Methane sulfonic acid (MSA) is marker of marine planktonic algae. MSA concentrations at Kevo peak from May to July and have estimated source locations in the Barents, Norwegian, and Greenland Seas, coinciding with warmer waters and increased biogenic activity. Using monthly averages from June and Jul, MSA concentrations were found to be positively correlated (r2 = 0.200; p < 0.001) with sea surface temperature anomalies in the surrounding seas and negatively (r2 = 0.280; p = 0.0018) with sea ice extent. The chemical composition dataset was analyzed by Positive Matrix Factorization (PMF5). The entire dataset (1964-2010) was modeled as well as three separate time periods, 1964-1978, 1979-1990, and 1991-2010. The dataset was split in 1979 due to a change from Whatman 42 cellulose filters to a glass fiber filters, and in 1990 due to drops in concentrations related to the economic collapse of the Soviet Union. Two factors representing non-ferrous metal smelters were found for all time periods. One factor was dominated by Cu and the other by Ni and Co. Each of the time periods contained a factor describing stationary fuel combustion with high percentages of V, BC, and nss-SO4; a ferrous metal factor dominated by Fe and some Mn; a biogenic sulfate factor; a factor containing the majority of Mo and W; and a factor dominated by Sn. The 1979-1990, 1991-2010, and 1964-2010 results contained a factor for As and Re, and a factor with the majority of Mn and Cd, which were not observed in 1964-1978. The 1964-1978 time period results contains three unique factors, a factor dominated by Ag, a factor dominated by Au, and a sea salt factor characterized by a high percentage of Na and Mg. The 1964-2010 contains an Ag and Au factor as well. Ag and Au both have high concentrations in the late 1960s that decrease dramatically starting in the early 1970s. The increased uncertainty due to the high blanks in the glass fiber filters may account for the inability to determine a sea salt factor in the later time periods.