大氣PM2.5水溶性無機鹽微粒與前驅氣體之半連續監測系統

Abstract

本研究開發一部可同時量測酸鹼氣體與PM2.5無機鹽濃度的線上即時監測系統(Parallel Plate Wet Denuder-Wet Electrical Precipitator, PPWD-WEP)，以手動多孔金屬片固氣分離採樣器(porous metal denuder sampler, PDS)為基礎，進行平行採樣比對，評估即時監測系統的準確性。PPWD-WEP由平行平板濕式固氣分離器(Parallel Plate Wet Denuder, PPWD)、高效率電極線-平板型濕式靜電集塵器(Wet Electrical Precipitator, WEP)、注射泵及離子層析儀(Ion Chromatography, IC)所組成。WEP內含一組可收集氣體的平行玻璃板及一組可同時收集氣體與微粒平行銅板。玻璃板表面擁有水膜，可以吸附氣流中的酸鹼氣體；銅板之間設有三條通高壓電的黃金電極線，能在金線與銅板之間產生電場，並利用電暈放電使通過極線附近的微粒帶電，而帶電的微粒會受靜電力的吸引收集在銅板表面。PPWD的構造與WEP相似，但內部僅有一組用來收集氣體的平行玻璃板。兩種收集板表面皆經噴砂處理，並塗敷TiO2奈米微粒以提高表面的親水性、加強收集板表面的水膜均勻度、增加氣體及微粒的收集效率。 本研究開發的線上即時監測系統能同時監測環境中無機酸鹼氣體及水溶性無機性微粒狀污染物，研究實驗比對結果顯示，線上監測系統具有一定的準確度，手動採樣與線上監測系統兩者所測得之酸鹼氣體SO2及NH3的相對誤差分別為-5.44 ± 10.32及-3.96 ± 10 %；PM2.5水溶性無機鹽成分Cl-、SO42-及NH4+的相對誤差分別為-4.51 ± 26.37、2.75 ± 20及-0.86 ± 20.88 %，因此線上監測系統可取代傳統手動採樣方法，方便操作並能提供即時環境汙染現況。

A real-time semi-continuous monitoring system (PPWD-WEP) which consists of PM2.5 cyclone, parallel plate wet denuder (PPWD), wet electrostatic precipitator (WEP) and ion chromatography (IC) had been developed to measure atmospheric pollutant near real time. The PPWD-WEP consists of two plexiglass plates with a copper plate that was attached to the inner surface. Both plexiglass plates and copper plates were sand-blasted and coated with the thin layers of nano-TiO2. Three gold wires were put between the copper plate to be used as discharge electrodes. PPWD-WEP was coupled with ion chromatography (IC) to analyze liquid sample from PPWD-WEP after sampling. The accuracy of PPWD-WEP was validated by comparing the PPWD-WEP result with collocated PDS as a reference at ambient environment. Results showed that for gaseous species, the relative difference in SO2 and NH3 concentration between the PPWD-WEP and PDS are -5.44 ± 10.32 and -3.96 ± 10 % respectively. For particulate species, the relative difference of Cl-, SO42- and NH4+ are -4.51 ± 26.37, 2.75 ± 20 and -0.86 ± 20.88 % respectively.