| 摘要: | 本研究於2013年2月至4月在屏東縣車城鄉國立海洋物博館進行戶外採樣，探討恆春空曠沿海地區之春季大氣氣狀物及奈米/微米氣膠化學組成中無機鹽類、羧酸、醣醇類、脫水醣類之特性與其生成來源及粒徑分佈，進而瞭解台灣陸域最南端背景大氣之空氣品質。
大氣氣狀物平均濃度高低依序為SO2>HCl>HNO3>NH3>HNO2，其中HCl、SO2及HNO3均為日間大於夜間，而HNO2為夜間大於日間，顯示日間之HNO3為HNO2經由光化轉變而成。
PM2.5平均濃度為16.16 +/- 5.30 μg m-3，無機鹽類主要成分為SO42-、NH4+、Na+、NO3-、Cl-，五種物種的質量濃度平均佔PM2.5質量濃度48.8 +/- 27.4%，其中SO42-及NH4+的濃度粒徑分布型態相關性高達0.95且主要粒徑波峰在0.32 μm，顯示兩者來自遠處光化產物傳輸所貢獻，沿海地區的Na+、Cl-、NO3-，主要均為海洋飛沫所貢獻，三種物種粒徑主要出現在1.8 μm以上的較大粒徑。恆春大氣氣膠最大氯損失出現在droplet mode，主要乃因光化產物造成大量氯損失。
大氣PM2.5羧酸，平均濃度為0.50 +/- 0.24 μg m-3，以單元酸acetate為最大量，二元酸oxalate較少，acetate與oxalate含量比值平均為1.82，oxalate的濃度粒徑分布主要出現在0.32 μm與SO42-的粒徑分布相關性更高達0.99，顯示oxalate乃為二元羧酸的最終產物。
醣醇類及脫水醣類全天平均濃度為590 +/- 422 ng m-3，以myo-lnositol濃度333 +/- 300 ng m-3為最高，主要濃度分布出現在1.8 μm及6.2 μm，來自土壤真菌代謝產物，依次為trehalose濃度為242 +/- 213 ng m-3、glucose濃度為2.67 +/- 6.42 ng m-3，glucose濃度變異較大；最少者為Mannitol濃度為0.11 +/- 0.58 ng m-3，雖然濃度變異較大，但主要濃度分布在18 nm的初始奈米粒徑。然而arabitol呈現雙峰，主要粒徑分布為1.8 μm及6.2 μm，與Na+及Cl- 微米粒徑濃度粒徑分布型態一致，顯示arabitol來源與海洋飛沫貢獻有關。
Levoglucosan主要為生質燃燒指標污染物，本研究levoglucosan濃度為8.92 +/- 16.92 ng m-3，在恆春沿海地區僅出現微量，粒徑分布並非所有粒徑分階皆會出現，僅在粒徑為54 nm、0.32 μm及1.8 μm，與另一生質燃燒指標物種K+出現的波峰粒徑一致，兩者在粒徑 54 nm-0.32 μm相關性為0.81，顯示春季時期恆春大氣存在些許的生質燃燒的遠處傳輸。
總觀以主成分因子分析春季恆春沿海空曠大氣氣膠之貢獻來源主要為海洋飛沫、遠處光化產物及生質燃燒產物傳輸及植被與土壤之生物排放。
In this study, remote aerosols were collected from the National Museum of Marine Biology and Aquarium, Checheng Township, Pingtung County, between February 2013, and April 2013. The characteristics, origin, and size distribution of inorganic salts, carboxylic acids, sugar alcohols, and anhydrosugars in the atmospheric gases, as well as the chemical composition of the nano- and micro- aerosol of the remote coastal regions of Hengchun area during spring were investigated to analyze the atmospheric air quality at the southern tip of Taiwan. In descending order, the average concentrations of atmospheric gases were SO2 > HCl > HNO3 > NH3 > HNO2. The concentrations of HCl, SO2, and HNO3 were greater during the daytime than during the night, but that of HNO2 was greater during the night than during the daytime, indicating that the HNO3 observed during the daytime was converted from HNO2 through photochemical transformation.The average PM2.5 concentration was 16.16 +/- 5.30 μg m-3. The main components of the inorganic salts were SO42-, NH4+, Na+, NO3-, and Cl-. The mass concentration of these five substances accounted for 48.8 +/- 27.4% of the average PM2.5 mass concentration. The correlation coefficient of SO42- and NH4+ concentrations and particle-size distributions reached 0.95, and the concentration peak of the major particles was 0.32 μm, indicating that both particles were photochemical products transmitted from a long distance. Na+, Cl-, and NO3- in the coastal area originate from ocean spray, with a large diameter of over 1.8 μm. In the Hengchun area, the maximal chloride deficit of atmospheric aerosols occurs in droplet mode, mainly caused by photochemical products.The average concentration of atmospheric PM2.5 carboxylic acid was 0.50 +/- 0.24 μg m-3, consisting mainly of acetate, and oxalate. The average content ratio of acetate and oxalate was 1.82. The highest concentration particle size of oxalate existed at was 0.32 μm. The correlation coefficient between oxalate and SO42- particle-size distribution was 0.99, indicating that oxalate is the final photochemical product of dicarboxylic acids The daily average concentration of sugar alcohols and anhydrosugars was 590 +/- 422 ng m-3, with a peak myo-inositol concentration of 333 +/- 300 ng m-3, and a main concentration distributed at 1.8 μm and 6.2 μm. The trehalose concentration of soil fungus-derived metabolite products was 242 +/- 213 ng m-3, and the glucose concentration was 2.67 +/- 6.42 ng m-3, with rather substantial variances. Mannitol exhibited the lowest concentration, which was 0.11 +/- 0.58 ng m-3. Although the concentration variation of mannitol was relatively substantial, the main concentration was distributed at an initial nanoparticle size of 18 nm. Arabitol was bimodal, with main particle-size distributions of 1.8 μm and 6.2 μm, consistent with that of the Na+ concentration and Cl- micron particle size distribution, indicating that the origin of arabitol was attributed to ocean spray. Levoglucosan is an indicator for biomass combustion pollutants. In this study, the levoglucosan concentration was 8.92 +/- 16.92 ng m-3, a minor presence in the coastal area of Hengchun. The particle-size distribution was not present in all site ranges, except for the 54 nm, 0.32 μm, and 1.8 μm , which is consistent with the peak particle size of K+, another biomass combustion indicator. In the particle size range of 54 nm-0.32 μm, the correlation between the two substances was 0.81, indicating that in spring, a modest amount of biomass combustion transmitted from a long distance exists in the atmosphere in Hengchun. In summary, based on principal component analysis, the atmospheric aerosols in the remote coastal area of Hengchun during spring are contributed by ocean spray, photochemical products and biomass combustion transmitted from a long-range transport, and biogenic emissions from vegetation and soil. |
