街道清掃工作藉由減少路面的街塵負荷以降低道路揚塵之排放量,減少空氣中之懸浮微粒,達到空氣污染改善的目標。但因掃街機具特性,如掃刷揚起之街塵未完全被鼓風機吸入,及經重力沉降未被去除的微粒會從出風口排出造成二次污染,使掃街作業後道路周界之懸浮微粒會有瞬間升高之現象。 改良式掃街車在掃街車有限的容許利用空間內,加裝粒狀污染物防治元件(包括局部密閉式集氣罩、高效率旋風分離器、過濾單元等三部份),為了瞭解對道路周界PM10削減成效,在車流量低之堤外道路灑下土樣模擬各級道路街塵負荷,在進行掃街測試的同時進行周界PM10監測工作。 依本研究結果顯示,改良式掃街車對於75~297μm及<75μm的路面街塵削減成效維持在70%~75%間,但對於>297μm之街塵削減成效(50.2%)較改裝前(62.1%)變的差些,顯示加裝粒狀物防治設備後,加裝防治設備及管路所產生的壓力損失,會降低掃街車的真空吸力,建議在加裝粒狀物防治設備時亦加大鼓風渦輪吸力。 另在模擬A級道路負荷的情形下,改良式掃街車ηPM10為17.0%。在模擬B級道路時,ηPM10為21.4%。在模擬C級道路時,ηPM10為27.5%。顯示改良式掃街車在增修後,在減少二次污染及改善周界空氣品質上確實有其效益。 實際在環河快速道路掃街後,其周界PM10排放量瞬間增加為掃街前水準的4~5倍,在經2小時之回復時間(Time of Response,tr)後會回復至掃街前水準。但卻需要更長的時間來使因掃街產生的二次污染排放量與因路面街塵被掃除而減少的揚塵量互相抵銷。本研究結果顯示,在洗掃作業後需要花費約9.5~12小時才能開始對整體空氣品質有正的效益。
Street sweeping can cleaning the deposited dust on the road to reduce PM emission from the road surface. It can reduce the PM10 emission and improve air quality. But it also cause the secondary pollution, like the deposited dust re-suspension by the whisk was not sucked completely, or the sucked dust not intercepted will be exhausted. The thsis investigated the removal efficiency of ambient PM10 using improved street sweeper with the particle prevention equipments( includes hood、cyclone and filter) in the limited space of sweeper. To understand the removal efficiency of ambient PM10, the study applies dust sample on the suburban road which has a low traffic density to simulate three classes of dust loading on civic road, then we monitor the ambient PM10 while sweeping. According to the result obtained from field experiments, the removal efficiency of improved street sweeper to bigger road dust(particle size>297μm)is 50.2% bader than unimproved(62.1%), means adding the particle prevention equipments will increase the pressure drop. We suggest to strengthen suction power while adding the particle prevention equipments. In a civic road simulated A class of dust loading, the ηPM10 is 17.0%. In a civic road simulated B class of dust loading, the ηPM10 is 21.4%. In a civic road simulated C class of dust loading, the ηPM10 is 27.5%. Shows the improved street sweeper did have the benefit to reduce secondary pollution and improving air quality. It was found that the ambient PM10 emission has a instant raising 4 times than that before sweeping , after 2 hours (Time od Response , tr ) , it back to the initial level. But the emission of secondary pollution needs more long time to counterbalance the decrease emission by cleaning the deposited dust on the road. The experimental result also shows it need spend 9.5~12 hours after sweeping , then starting have real benefit to the whole air quality.