J Air Waste Manag Assoc. 2014 Sep;64(9):1003-12. doi: 10.1080/10962247.2014.907217.
Near-roadway ambient black carbon (BC) and carbon monoxide (CO) concentrations were measured at two schools adjacent to a freeway and at an urban background school 2 km from the freeway to determine the change in concentrations attributable to vehicle emissions after the three-lane expansion of U.S. Highway 95 (US 95) in Las Vegas, Nevada. Between summer 2007 and summer 2008, average weekday small-vehicle volume increased by 40% +/- 2% (standard error). Average weekday large-vehicle volume decreased by 17% +/- 5%, due to a downturn in the economy and an associated decline in goods movement. Average vehicle speed increased from 58 to 69 mph, a 16% +/- 1% increase. The authors compared BC and CO concentrations in summer 2007 with those in summer 2008 to understand what effect the expansion of the freeway may have had on ambient concentrations: BC and CO were measured 17 m north of the freeway sound wall, CO was measured 20 m south of the sound wall, and BC was measured at an urban background site 2 km south of the freeway. Between summer 2007 and summer 2008, median BC decreased at the near-road site by 40% +/- 2% and also decreased at the urban background site by 24% +/- 4%, suggesting that much of the change was due to decreases in emissions throughout Las Vegas, rather than only on US 95. CO concentrations decreased by 14% +/- 2% and 10% +/- 3% at the two near-road sites. The decrease in BC concentrations after the expansion is likely due to the decrease in medium- and heavy-duty-vehicle traffic resulting from the economic recession. The decrease in CO concentrations may be a result of improved traffic flow, despite the increase in light-duty-vehicle traffic. Implications: Monitoring of BC and CO at near-road locations in Las Vegas demonstrated the impacts of changes in traffic volume and vehicle speed on near-road concentrations. However, urban-scale declines in concentrations were larger than near-road changes due to the impacts of the economic recession that occurred contemporaneously with the freeway expansion.
毗邻高速公路的两所学校和距离高速公路 2 公里的市区背景学校测量了道路附近环境黑碳 (BC) 和一氧化碳 (CO) 浓度，以确定美国内华达州拉斯维加斯 95 号州际公路 (US 95) 扩建成三车道后，归因于车辆排放的浓度变化。2007 年夏至 2008 年夏，工作日小型车平均交通量增加了 40% +/- 2%（标准误差）。由于经济下滑和商品运输量下降，工作日大型车平均交通量减少了 17% +/- 5%。平均车速从 58 英里/小时增加到 69 英里/小时，增加了 16% +/- 1%。作者比较了 2007 年夏和 2008 年夏的 BC 和 CO 浓度，以了解高速公路扩建可能对环境浓度产生的影响：BC 和 CO 在高速公路隔音墙以北 17 米处测量，CO 在隔音墙以南 20 米处测量，BC 在距高速公路以南 2 公里的市区背景处测量。2007 年夏至 2008 年夏，近路点 BC 的中位数下降了 40% +/- 2%，市区背景点 BC 也下降了 24% +/- 4%，表明大部分变化是由于拉斯维加斯整个地区的排放量减少，而不仅仅是在 US 95 上。近路点 CO 浓度分别下降了 14% +/- 2%和 10% +/- 3%。高速公路扩建后 BC 浓度的下降可能是由于经济衰退导致中重型车辆交通量减少。CO 浓度的下降可能是由于交通流量改善，尽管轻型车辆交通量增加。影响：在拉斯维加斯近路地点监测 BC 和 CO，证明了交通量和车速变化对近路浓度的影响。然而，由于与高速公路扩建同时发生的经济衰退的影响，市区浓度的下降幅度大于近路变化。
