Cape J N, Tang Y S, van Dijk N, Love L, Sutton M A, Palmer S C F
Edinburgh Research Station, Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK.
Environ Pollut. 2004 Dec;132(3):469-78. doi: 10.1016/j.envpol.2004.05.009.
Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.
在苏格兰，采用基于道路交通密度和背景氮沉降的分层抽样方案，对距离道路边缘最远10米处进行了为期一年的二氧化氮（NO₂）和氨（NH₃）双月综合测量。远离道路边缘时，气体浓度下降迅速，NH₃在最初10米内浓度下降90%，NO₂在最初15米内浓度下降90%。NO₂传输距离更长，这反映了排放出的NO与O₃反应生成二次NO₂。在车道边缘估算的高于背景值的浓度，对于NH₃而言与交通密度呈线性比例关系（微克NH₃ 立方米⁻³ = 1×10⁻⁴×每日汽车数量），这反映了三元催化剂的排放。对于NO₂，其排放强烈依赖于车辆类型和燃料，交通密度按照“汽车当量”计算；车道边缘的NO₂浓度与汽车当量数量成正比（微克NO₂ 立方米⁻³ = 1×10⁻⁴×每日汽车当量数量）。尽管NH₃的绝对浓度（微克 立方米⁻³）比NO₂小五倍，但NH₃向植被的沉降速度更快，这意味着车辆排放到路边植被的干氮沉降中，来自NH₃和NO₂的量大致相当。根据交通密度，在车道边缘，车辆废气导致的额外氮沉降为1至15千克氮 公顷⁻¹ 年⁻¹，在距离道路边缘10米处降至0.2至10千克氮 公顷⁻¹ 年⁻¹。
