Impact of Photoactive Roads on Urban Air Quality

汽车尾气是世界各地城市空气污染的主要来源，也是造成地面臭氧污染的主要因素。改善城市空气质量的一项努力是将二氧化钛应用于建筑物和道路表面，使这些表面具有光催化作用。在阳光照射下，这些表面有效地破坏氮氧化物（NOx）和挥发性有机化合物（VOCs），臭氧的前体。虽然这些表面已被证明能有效去除氮氧化物，但还没有系统的研究来量化它们在减少人类接触臭氧和汽车尾气中排放的有毒化合物方面的潜力。事实上，这些表面可能会产生空气有毒物质，如氮氧化物产生的亚硝酸，挥发性有机化合物产生的甲醛和乙醛。我们小组的初步研究表明，当汽油蒸气混合物暴露在照明的二氧化钛处理的混凝土中时，甲醛和乙醛会迅速产生。光活性道路实际上可能通过降低氮氧化物/挥发性有机化合物的浓度比和通过产生亚硝酸和甲醛增加自由基的产生率来增加城市地区的臭氧。了解汽车尾气转化对这些表面的净影响，对于确定光活性城市材料是否真的会改善城市空气质量至关重要。在这个项目中，室内研究将用于量化氮氧化物和挥发性有机化合物在光活性道路材料（沥青和混凝土）中的损失，作为光照水平、温度、湿度和商用二氧化钛表面处理产品的函数。亚硝酸和醛的产率也将被测量。室内试验将在模拟汽车尾气（包括汽油蒸气）的配制试验混合物上进行，并在环境污染条件下进行室外试验。氮氧化物和挥发性有机化合物的表面破坏效率以及亚硝酸和醛的产量将被参数化，并用于空气质量模型，以测试对主要污染物浓度和臭氧形成光化学的影响。该项目将首次对光活性道路对城市空气化学的影响进行系统调查和综合空气质量数值模拟研究。这项研究将为公众和城市规划者提供急需的定量信息，以了解光活性道路作为减少城市空气污染的解决方案的有效性。暴露在汽车尾气中已被证明对心血管健康有重大影响。利用光活性道路从源头上清除车辆污染物，有可能改善居住在主要道路附近的数百万人的健康。研究结果将用于本科课程作业，并在会议和同行评议的出版物中传播。这项研究将帮助支持一名研究生，并为西北印第安学院的一名美国印第安学生提供暑期研究实习的支持。

1232994JobsonVehicle emissions are a major source of urban air pollution in cities worldwide and major contributors to ground level ozone pollution. One effort taking hold to improve air quality in cities is the application of titanium dioxide to building and roadway surfaces to make these surfaces photocatalytic. Upon irradiation with sunlight, these surfaces efficiently destroy nitrogen oxides (NOx) and volatile organic compounds (VOCs), the precursors to ozone. While such surfaces have been shown to be effective at removing NOx, there has been no systematic study to quantify their potential to reduce human exposure to ozone and to the toxic compounds emitted in vehicle exhaust. These surfaces may in fact generate air toxics such as nitrous acid from NOx, and formaldehyde and acetaldehyde from VOCs. Preliminary studies by our group have shown that formaldehyde and acetaldehyde are rapidly generated when gasoline vapor mixtures are exposed to illuminated titanium dioxide treated concrete. Photoactive roads may in fact increase ozone in urban areas by decreasing the NOx / VOC concentration ratio and increasing radical production rates via production of nitrous acid and formaldehyde.Understanding the net effect of vehicle exhaust transformation on these surfaces is essential for determining if photoactive urban materials will in fact improve urban air quality. In this project chamber studies will be used to quantify NOx and VOCs loss to photoactive roadway materials (asphalt and concrete) as a function of light levels, temperature, humidity, and commercial titanium dioxide surface treatment products. The yields of nitrous acid and aldehydes will also be measured. Chamber tests will be conducted on prepared test mixtures that mimic vehicle exhaust including gasoline vapor and in outdoor experiments under ambient pollution conditions. The surface destruction efficiencies of NOx and VOCs and yields of nitrous acid and aldehydes will be parameterized and used in an air quality model to test the resulting impact on primary pollutant concentrations and ozone formation photochemistry. This project would provide the first systematic investigation and integrated air quality numerical modeling study of the impact of photoactive roads on urban air chemistry.This study will provide much needed quantitative information of interest to the public and urban planners on the efficacy of photoactive roads as a solution to reduce urban air pollution. Exposure to vehicle exhaust has been shown to have a significant impact on cardiovascular health. Removing vehicle pollutants at the source with photoactive roads has the potential to improve health for millions of people living near major roadways. The results of the research will be used in undergraduate course work and disseminated in conferences and peer reviewed publications. The research will help support one graduate student and provide support for a summer research internship for an American Indian student from the Northwest Indian College.