Department of Chemistry and Biochemistry , University of Denver , Denver , Colorado 80208 , United States.
Environ Sci Technol. 2018 Jul 3;52(13):7587-7593. doi: 10.1021/acs.est.8b00926. Epub 2018 May 15.
The University of Denver has collected on-road fuel specific vehicle emissions measurements in the Chicago area since 1989. This nearly 30 year record illustrates the large reductions in light-duty vehicle tailpipe emissions and the remarkable improvements in emissions control durability to maintain low emissions over increasing periods of time. Since 1989 fuel specific carbon monoxide (CO) emissions have been reduced by an order of magnitude and hydrocarbon (HC) emissions by more than a factor of 20. Nitric oxide (NO) emissions have only been collected since 1997 but have seen reductions of 79%. This has increased the skewness of the emissions distribution where the 2016 fleet's 99th percentile contributes ∼3 times more of the 1990 total for CO and HC emissions. There are signs that these reductions may be leveling out as the emissions durability of Tier 2 vehicles in use today has almost eliminated the emissions reduction benefit of fleet turnover. Since 1997, the average age of the Chicago on-road fleet has increased 2 model years and the percentage of passenger vehicles has dropped from 71 to 52% of the fleet. Emissions are now so well controlled that the influence of driving mode has been completely eliminated as a factor for fuel specific CO and NO emissions.
丹佛大学自 1989 年以来一直在芝加哥地区进行道路燃料特定车辆排放测量。这近 30 年的记录说明了轻型车辆排气管排放的大幅减少，以及在越来越长的时间内保持低排放的排放控制耐久性的显著提高。自 1989 年以来，燃料特定的一氧化碳 (CO) 排放量减少了一个数量级，碳氢化合物 (HC) 排放量减少了 20 多倍。氮氧化物 (NO) 排放自 1997 年才开始收集，但已减少了 79%。这增加了排放分布的偏度，其中 2016 年车队的第 99 个百分位数贡献的 CO 和 HC 排放量约为 1990 年总量的 3 倍。有迹象表明，这些减排可能趋于平稳，因为当今使用的 Tier 2 车辆的排放耐久性几乎消除了车队更替的减排效益。自 1997 年以来，芝加哥道路车队的平均车龄增加了 2 个车型年，乘用车的比例从车队的 71%下降到 52%。排放现在得到了很好的控制，驾驶模式的影响已完全消除，不再是燃料特定 CO 和 NO 排放的一个因素。
