大氣氣膠碳成分量測方法比較及干擾因子的探討; On the study of measuring methods and interfering factors in the determination of atmospheric aerosol carbons

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题名:	大氣氣膠碳成分量測方法比較及干擾因子的探討;On the study of measuring methods and interfering factors in the determination of atmospheric aerosol carbons
作者:	陳永盛;Yung-sheng Chen
贡献者:	環境工程研究所
关键词:	氣膠碳成分;碳成分量測方法比較;NaCl干擾;黑碳吸光截面積σ;VOCs;Aerosol carbon fractions;comparison of aerosol carbon measurements;NaCl interference;absorption cross section of black carbon (σ);Volatile organic carbons (VOCs)
日期:	2008-07-07
上传时间:	2009-09-21 12:19:06 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	以熱-光學法分析大氣氣膠碳成分，是廣泛被使用的量測方法，這種方法對於分析過程產生裂解碳的矯正程序，可分成熱-光學反射(TOR)和熱-光學透射(TOT)兩種。本文比較不同溫度協定與裂解碳校正方法的差異，並探討濾紙採樣受到揮發性有機化合物(VOCs, Volatile Organic Compounds)干擾的影響。此外，本文也在海岸地區採樣，進行NaCl對於EC成分解析干擾的評估。最後再以北部新莊微粒超級測站的BC (black carbon)與EC (elemental carbon)監測數據進行線性迴歸分析，以斜率得到BC吸光截面積(σ)的修正數值，訂定大台北都會區合適的σ數值，以及探討σ的影響因子。研究結果顯示，當大氣氣膠碳成分濃度增加，微粒在濾紙沉積厚度變大，TOR比TOT方式所估算的裂解碳濃度將較低。都市地區由於受到車輛排放與溫度的影響，當進行碳成分採樣時，石英濾紙吸附VOCs的濃度將會提升，且微粒有機碳揮發情形較為顯著。經由北縣石門海岸測站觀測結果顯示，當Na+濃度達3 ~ 6 μg m-3之間時，Na+對於EC成分解析的干擾情形顯著。本文以2006 ~ 2007兩年環保署北部微粒超級測站逐時數據共約17,000筆，得到σ的修正數值，在這段期間σ數值變動範圍約在20 ~ 40 m2 g-1，當硝酸鹽濃度增加、臭氧發生高濃度、大氣相對濕度達90%以上、以及降雨事件時段，都將造成σ數值上升。本文在評估σ數值日變化時，發現上下班尖峰時段σ數值跟著增加。σ的日變化也與PM2.5、PAH(總多環芳香烴)、OC(有機碳)日變化三者具有良好的相關，顯示當大氣氣膠濃度與有機成分增多將對σ數值造成影響。對於大台北都會區合適的σ數值，本文建議應該從製造商提供的16.6 m2 g-1改為24.5 m2 g-1，此數值適用於AE 31吸光儀量測BC的880 nm波段。 The thermal-optical method is widely used for measuring atmospheric aerosol carbons. In this method, pyrolyzed carbon correction can be split into thermal optical reflectance (TOR) and thermal optical transmittance (TOT). This study compares the differences due to different temperature protocols and pyrolyzed carbon corrections. Meanwhile, the interferences of volatile organic carbons (VOCs) on aerosol carbon analysis for filter samples are also studied. Moreover, the effects of NaCl on EC fractionization in the coastal area are evaluated. Finally, the monitoring data of aerosol black carbon (BC) and elemental carbon (EC) from North aerosol supersite are adopted to conduct a linear regression analysis. The slope resulted from this analysis is considered to be the best BC absorption cross section (σ) and the influencing factors of σ values are also disussed. The results show that TOR tends to underestimate pyrolyzed carbon correction when atmospheric carbon concentration is increased and thus the depth of particle deposition on a filter. Under the influence of vehicle exhausts and ambient temperature, VOCs adsorption by quartz fiber filter will be increased when using the filter in aerosol collection. Meanwhile, organic carbon evaporation from deposited particles is severer. The interference of Na+ on EC fractionization is significant when Na+ concentration reaches 3 - 6 μg m-3 based on the observation at the Shimen site on the coastline of Taipei County. In this study, 17,000 hourly data from North aerosol supersite were used to obtain the correction value of σ. The variation of σ is within the range of 20 - 40 m2 g-1 during this time period. Meanwhile, the value of σ is found to increase with higher aerosol nitrate, higher ozone concentration, higher atmospheric relative humidity above 90%, and the duration of raining event. In the diurnal variation of σ, σ value is found to enhance in the traffic peak hours. The diurnal variations of σ value are also agreed well with that of PM2.5, PAH, and OC. It indicates that the increase of atmospheric aerosols and aerosol organic fractions will affect σ values. The best σ value in the greater Taipei metropolis is recommended to change from the manufacturer’s 16.6 to 24.5 m2 g-1 for AE31 Aethalometer in measuring BC at 880 nm wavelength.
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