高流量PM10採樣過程中的異常生成物研究

Abstract

本研究使用固氣分離器與PM10高流量採樣器在大氣中進行懸浮微粒的平行 採樣，藉以了解在PM10高流量採樣器所收集的水溶性離子濃度和實際溶度 差異，並探討在採樣過程中導致這種誤差之可能反應機置。首先，先比較 使用玻璃纖維與石英的兩種不同濾紙的兩台高流量PM10的結果，發現含鹼 度較高的玻璃纖維濾紙較易吸收二氧化硫，硝酸，亞硝酸和氯化氫等酸性 氣體，造成其收集的硫酸鹽、硝酸鹽及氯鹽濃度比石英濾紙為高；而酸性 的石英濾紙則較易吸收鹼性的氨氣氣體，造成其所收集的銨鹽濃度大於玻 璃纖維濾紙。因此，濾紙的酸鹼度影響水溶性鹽粒之濃度甚鉅。其次，由 固氣分離器與PM10高流量採樣器平行採樣的結果得之，無論使用玻璃纖維 濾紙或石英濾紙，在採樣過程中所產生的硫酸鹽正異常生成物均大於 Coutant化學模式所預測的值。而在石英濾紙上產生硝酸鹽的正異常生成 物有時反較乾淨玻璃纖維濾紙因吸附硝酸氣體所產生的硝酸鹽來得多。由 上述情況得知，硫酸鹽與硝酸鹽的正異常生物不僅會在濾紙表面產生，而 且極可能在被收集微粒的堆積層中產生。但是本研究也發現，在PM10高流 量採樣器的濾紙中氯鹽濃度均嚴重低於實際濃度；且在玻璃纖維濾紙中的 銨鹽濃度均小於實際值，但是在石英濾紙的銨鹽會因採樣過程中的濕度大 小而大於或小於實際值。從固氣分離器中濾器組的實驗數據得知，在採樣 過程中造成銨鹽揮發的主要物種為氯化銨，少部分為硝酸銨，而且若干量 的非揮發性的氯鹽在採樣過程中會因與酸性微粒反應而損失。此外，根據 氣固比的觀念來預估揮發性的硝酸鹽與銨鹽有可能因微粒堆積層間的相互 作用而損失。最後，我們發現離子性的異常生成物並不一定會造成微粒總 質量濃度的改變，這可能因為在採樣過程中也同時產生有機性的異常生成 物所導致的結果。 This research used an Annular Denuder System (ADS) to sample suspended particles in the atmosphere in parallel with High Volume PM10 samplers (HVPM10). It is intended to study the sampling of soluble ionic species collected by the HVPM10 sampler, the mechanisms that may lead to this error. Firstly, results obtained by two HVPM10 samplers using different filters, namely quartz and glass fiber filters, were compared. It was found that the glass fiber filters with higher alkalinity adsorb more ambient active acidic gases such as SO2, HNO2, HNO3 and HCl during sampling resulting in the more sulfate , nitrate and chloride concentrations compared to those of quartz filters. On the other hand, acidic quartz filter was found to adsorb more basic ammonia gas thus producing ammonium concentration compared to that of glass fiber filter. Secondly, results of the ADS and HVPM10 samplers were compared. It was found that artifact sulfate concentration in both quartz and glass fiber filters of the HVPM10 sampler exceed the amount predicted by Coutant's model. In some cases, artifact nitrate concentration in quartz filters was found to exceed the amount present in blank glass fiber due to its adsorption of HNO3. Based on these results, it can be concluded that artifact sulfate and nitrate not only occurs within filters but also in particles deposits collected on filters. According to the experimental data in the filter pack of the ADS, the major species of ammonium was found to be ammonium chloride rather than ammonium nitrate, and some of nonvolatile chloride evaporated due to its reaction with acdic paticles. Based on the ratio of gas to particle distribution to predict the loss of nitrate annd ammonium species during sampling. It is found that nonvolatile nitrate and ammonia would indeed evaporate due to interaction that occurred within particle deposits.