在臺灣地區高度都市化過程中,空氣污染物可能會對導致大氣環境產生各種物理性及化學性的變化。由於地球的自旋運動而造成氣候的季節性變化,因此,空氣污染不僅發生在地區範圍內,也會擴散及蔓延到周遭的環境;與空氣污染物相關之一,便是環境中的街塵數量增加。本研究採集臺灣地區臺中市及嘉義市之街塵樣品,並進行粒徑分析和重金屬含量測定。研究結果顯示,粒徑較小的街塵由於比表面積較大,故可吸附較多重金屬;重金屬鉛和鋅,通常在工業製程中排放此類汙染物質,因此,其粒徑分佈和吸附粉塵之粒徑為>2.00 mm及2.00 mm~0.841 mm。相較之下,嘉義市之街塵中重金屬砷、鎳及鉛濃度高於臺中市,可能受氣候影響和當地土壤母質特徵所造成。街塵負荷的粒徑大小,亦影響重金屬濃度及其形態。由街道清掃前、後街塵比較發現,掃街後能有效減少交通排放及懸浮微粒之街塵含量,並改善空氣品質。此外,削減街塵微粒之含量,將有助於降低人體呼吸和皮膚接觸的風險性危害。 關鍵詞:街塵負荷,重金屬,粒徑分析,總懸浮微粒,空氣品質
Air polluted by pollutants may cause various physical and chemical changes of atmospheric environment in the process of highly urbanization in Taiwan area. Air pollution not only occurs in regional range but also spreads to vicinal environment due to the spin motion of earth and seasonal changes of climate. One of the related air pollutions is the increased amount of dust in the environment. The street dust samples were collected from Chiayi City and Taichung city in Taiwan and then the samples were subjected to the particle size analysis and the determination of heavy metals concentrations. The research results showed that street dust with smaller particle sizes can adsorb much more heavy metals due to higher specific surface area. Heavy metals of Pb and Zn-containing particulates are usually emitted from industrial process. Accordingly, they were distributed and adsorbed in the dust with particle sizes > 2.00 and 2.00-0.841 mm. In comparison, the concentrations of heavy metals of As, Ni, and Pb in the dust were higher from Chiayi City than from Taichung City. This may be mainly attributed to climate and characteristics of local soil parent materials. The loading degree of street dust affected the concentrations of heavy metals while particle sizes of street dust governed the speciation of heavy metals. The comparison of the amounts of street dusts before and after street sweeping and washing revealed the advantages of reduction of floating dust caused by moving vehicles and of concentrations of total suspended particulate, and improvement of air quality. Further, the reduction of the fine particle of street dust may subsequently decrease hazardous risks of human breath system and skin contact. Keywords: Street dust loading, heavy metals, particle size analysis, total suspended particulate, air quality
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