Environmental Engineering and Management, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani 12120, Thailand.
Environmental Engineering and Management, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani 12120, Thailand.
Sci Total Environ. 2018 Jun 15;627:290-303. doi: 10.1016/j.scitotenv.2018.01.216. Epub 2018 Feb 3.
The levels of BTEX (benzene, toluene, ethylbenzene and xylenes) in a congested urban area of Hanoi were characterized in a winter and a transitional period in 2015. Monitoring was conducted at two roads simultaneously with traffic flows and one ambient site together with meteorology. Hourly and bi-hourly BTEX samples collected using charcoal tubes were analyzed by GC-FID. BTEX levels in winter, 131 ± 71 μg/m in heavy traffic Truong Chinh (TC) road, 101 ± 29 μg/m in small residential Nguyen Ngoc Nai (NN) road, and 30 ± 15 μg/m in the ambient air site (AA, about 150 m from each road) were 1.3-2.1 times higher than the respective levels in the transitional period. Hourly benzene levels exceeded the Vietnam national standard more frequently at TC (45%) than at NN (32%) and least at AA (5%) out of 120-180 measurements, respectively. Roadside hourly levels well reflected the diurnal traffic flow pattern and higher BTEX levels were measured at TC than NN. The ambient site exhibited lower BTEX levels and different diurnal patterns, with more pronounced evening peaks than morning rush hour peaks. BTEX pollution rose showed a strong influence of wind to levels measured at AA. Species ratios (T/B and X/E) showed typical ranges for traffic emissions at roadsides. Ratios for AA and NN after midnight with no vehicles operating showed the aging effects with typical low X/E ratios. Multivariate analysis results suggested association of gasoline vehicles with BTEX at roadsides. Backward trajectory analysis indicated potential regional transport of long-lived benzene associated with continental airmass categories. BTEX at TC our study were 2-3 times lower for every species compared to those previously reported, showing results of fuel quality and vehicle technologies improvement. Health risks of people working at the roadside also reduced by about 3 times during the 10 years.
2015 年冬季和过渡时期，对河内一个交通拥堵地区的 BTEX（苯、甲苯、乙苯和二甲苯）水平进行了研究。在两条道路上同时进行监测，一条是交通流量大的 Trường Chinh（TC）路，另一条是交通流量小的 Nguyễn Ngọc Nại（NN）路，还有一个环境监测点。使用活性炭管采集的每两小时和每小时 BTEX 样本，通过 GC-FID 进行分析。冬季，TC 路上交通繁忙时 BTEX 浓度为 131±71μg/m3，NN 路上交通流量较小时 BTEX 浓度为 101±29μg/m3，环境监测点（AA，距离每条道路约 150m）BTEX 浓度为 30±15μg/m3，这些浓度均比过渡时期分别高出 1.3-2.1 倍。120-180 次测量中，TC 路的苯浓度超标（45%）比 NN 路（32%）更频繁，而 AA 路（5%）则最少。每小时路边浓度很好地反映了交通流量的日变化模式，TC 路的 BTEX 浓度高于 NN 路。环境监测点的 BTEX 浓度较低，日变化模式不同，傍晚峰值比早高峰更明显。BTEX 污染升高显示出风向对 AA 点测量值的强烈影响。物种比（T/B 和 X/E）显示了路边交通排放的典型范围。午夜后没有车辆运行时，AA 和 NN 的比值显示出老化效应，典型的低 X/E 比值。多元分析结果表明，汽油车与路边的 BTEX 有关。后向轨迹分析表明，长寿命苯与大陆气团类别有关的区域传输。与之前的报道相比，我们研究中 TC 路上的每种 BTEX 浓度都降低了 2-3 倍，这表明燃料质量和车辆技术的改进取得了成果。10 年来，在路边工作的人的健康风险也降低了约 3 倍。
