제주지역 강수성분 장기 모니터링 및 오염특성 연구

Abstract

The collection of the total 724 precipitation samples in Jeju area was made during 1997-2011, and their major ionic components were analyzed by ion chromatography. The concentrations of major inorganic ions (Na+, NH4 +, K+, Ca2+, Mg2+, Cl-, NO2-, NO3-, PO43-, SO42-) and organic acid species (HCOO-,CH3COO-) were determined. From the comparison in terms of ion balance, electric conductivity, and acid fraction of precipitation, it was found their correlation coefficients were in the range of 0.933∼0.987, indicating a good quality of the collected data. During the study period, the volume-weighted mean pH and electric conductivity at Jeju area were 4.79 and 21.9 μS/cm, respectively. The precipitation was a weak acidic, showing 94% frequency below pH 5.6. The ionic strength of precipitation was 0.24 ± 0.27 mM, indicating 30.8% of total precipitation within a pure rainwater criteria. The volume-weighted mean concentrations (ueq/L) of the ionic species in precipitation were in the order of Cl- > Na+ > nss-SO4 2- > NH4+ > NO3- >H+ > Mg2+ > nss-Ca2+ > K+ > PO43- > NO2- >HCOO- > CH3COO- > F- >HCO3- > CH3SO3-. The marine (Na+, Mg2+, Cl-), anthropogenic (NH4+,nss-SO42-, NO3-) and soil (nss-Ca2+) species have contributed to the total ionic components of precipitation samples by 43∼74%, 16∼40% and 0.7∼5.3%, respectively. The correlation coefficients between NO3-, nss-SO42-, and NH4+ showed high values, indicating the formation of ammonium sulfate and ammonium nitrate due to the neutralization of acidic precipitation substances. The correlation coefficient between Na+ and Cl- was 0.99, which indicated an introduction of sea salts to the precipitation in Jeju area. The variation of NO3- and nss-SO4 2-concentrations showed a distinct seasonality with higher concentration in winter compared to summer, indicating an increase of fossil fuel consumption and a possibility of long-range transport of air pollutants from continental area by the westerly wind in winter season. The nss-Ca2+ concentration was also shown the highest in winter. Furthermore, it has increased comparatively in spring season, possibly due to a soil influence including the Asian Dust. The acidity contributions by sulfuric and nitric acids were 58.1 and 35.7%, respectively. Meanwhile the acidity contributions by formic and acetic acids were 3.7 and 2.5%, respectively. The free acidity was 33.0%, showing high in summer and low in spring. On the other hand, the neutralization factors by ammonia and calcium carbonate were 0.52 and 0.22, respectively, especially showing high neutralization contribution by calcium carbonate in spring season. Based on the factor analysis, the precipitation components were influenced by the order of marine > anthropogenic > soil and biogenic sources at Jeju area. Furthermore, the back trajectory analysis explained that the concentrations of nss-SO42-, NO3-, NH4+ and nss-Ca2 were higher when the air masses came from China continent to Jeju area, on the other hand, their concentrations were lower when from the North Pacific Ocean.