逸散性揚塵之排放係數與控制效率量測研究

Abstract

本研究中利用暴露高度濃度剖面法，量測新竹地區三條鋪面道路、一處裸露地面和三條未鋪面道路的逸散性揚塵排放係數。並且針對灑水及控制車速二種未鋪面道路揚塵控制方法，評估其控制效率。在鋪面道路的實驗結果方面，發現揚塵的總排放係數，e (g/VKT or ton/m2-day)，會隨著風速(Vw, m/s)、坋土負荷(sL, g/m2)、每小時通過車輛數(Nv, #/hr)、平均通過車速(Vv, km/hr)增加而增加，而隨著街塵含水率(M, %)增加而減少。在博愛街、學府路和建中路所量測得的平均揚塵排放係數分別為0.22±0.13 g/VKT (ave.±std. dev.)(或 4.01±1.75 x 10-7 ton/m2.day),、0.08±0.06 g/VKT (或 1.24±0.65 x 10-7 ton/m2.day) 及 2.00±1.52 g/VKT (或 31.67±25.67 x10-7 ton/m2.day)。 現場狀況及氣象參數很明顯地對排放係數造成影響。而實驗所得的排放係數與眾多文獻中經驗式計算結果比較後發現，與Hesketh and Cross (1983)最為相近。 以多變數迴歸方法，針對所量測的排放係數及各項參數作迴歸，可得e (10-7 ton/m2-day) = K · Vw0.68 sL0.77 M -0.96 Vv0.53 Nv0.23，R2=0.90， 其中 K=2.71x10-4 or 5.21x 10-4 for e< 7x10-7 ton/m2-day or e > 7x10-7 ton/m2-day。迴歸式計算結果與實驗值比較，誤差在35％以內。 在裸露地面與未鋪面道路實驗方面，裸露地結果顯示，揚塵總排放係數會隨平均風速、坋土比率(s, %)增加而增加，但會隨地面粉塵含水率增加而減少。而在未鋪面道路方面，除了上述因素之影響外，揚塵排放係數另外會隨著每小時通行車輛數及平均車速增加而增加。利用多變數迴歸方法對裸露地實驗值迴歸結果為：e (10-7 ton/m2-day) = 5.01 x 10-2 Vw2.05 s M-0.98 (R2=0.86)；而未鋪面道路方面為：e (10-7 ton/m2-day ) = 8.72x 10-2 x Vw0.64x s0.19x M -0.05xVv1.32 x Nv1.11 (R2=0.96)。針對未鋪面道路的PM10與PM2.5佔總揚塵排放係數的比例，研究所得的結果分別為20.6±12.9 % 及 2.3±1.2 %。 逸散性揚塵控制技術方面，未鋪面道路灑水控制效率在無車輛通行的情況下效率為63.8±1.4 %，而在有車輛通行的情況下為60.1±34.9 %。另外車速控制研究方面，發現揚塵排放係數與車行速度的二次方成正比。

In this study, the exposure profile method was used to measure the emission factor of fugitive dust from three paved roads, one exposed earth surface and three unpaved roads in Hsin Chu of Taiwan. Control efficiencies of watering and vehicle speed control of the unpaved roads were also investigated. In the paved roads experiment, the measured emission factor for total suspended particulate (TSP), e (g/VKT or ton/m2-day), was found to increase with an increasing wind speed (Vw, m/s), silt loading of paved roads (sL, g/m2), number of vehicle per hour (Nv, #/hr) and average speed of vehicle (Vv, km/hr), but to decrease with an increasing moisture content of the road dust (M, %). Results show that the average emission factor of fugitive dust is 0.22±0.13 g/VKT (ave.±std. dev.)(or 4.01±1.75 x 10-7 ton/m2.day), 0.08±0.06 g/VKT (or 1.24±0.65 x 10-7 ton/m2.day) and 2.00±1.52 g/VKT (or 31.67±25.67 x10-7 ton/m2.day) for the Poai street, Shei-Fu road, and Chein-Chong road, respectively. Due to meteorological and field conditions, considerable variation of the emission factor is obverved. The present average emission factors agree best with the calculated values of the empirical equation by Hesketh and Cross (1983), among many empirical equations in the literature. By the multi-variable regression technique, the TSP emission factors measured in the three paved roads can be fitted as e (10-7 ton/m2-day) = K · (Vw)0.68 (sL)0.77 (M) -0.96 (Vv)0.53 (Nv)0.23, R2=0.90, where K=2.71x10-4 or 5.21x 10-4 for e< 7x10-7 ton/m2-day or e > 7x10-7 ton/m2-day, respectively. The predicted values are within ± 35 % of the experimental data. In the exposed earth surface and unpaved road experiment, results showed that for the exposed earth surface, the emission factors of TSP increased with an increasing average wind speed (Vw, m/s), silt content of unpaved roads (s, %), but were inversely affected by the moisture content of the road dust (M, %). For the unpaved roads, the emission factors also increased with an increasing average number (Nv, #/hr) and speed (Vv, km/hr) of vehicles. By the multi-variable regression technique, the emission factors measured at the exposed earth surface can be predicted as e (10-7 ton/m2-day) = 5.01 x 10-2 Vw2.05 s M-0.98 (R2=0.86), and those measured at the unpaved roads can be predicted as e (10-7 ton/m2-day ) = 8.72x 10-2 x Vw0.64x s0.19x M -0.05xVv1.32 x Nv1.11 (R2=0.96). In the total reentrained dust from the unpaved roads, the fractions of PM10 and PM2.5 were found to be 20.6±12.9 % and 2.3±1.2 %, respectively. In the study of control of fugitive dust by water spray, the efficiency was found to be 63.8±1.4 % for the unpaved roads without vehicle traveling, and 60.1±34.9 % for the unpaved roads with vehicle traveling. In the study of vehicle speed control, the emission factor was found to be directly proportional to the second power of the vehicle travelling speed.