ISSN 2303-4521 Periodicals of Engineering and Natural Sciences Original Research Vol. 9, No. 3, September 2021, pp.768-780 © The Author 2021. This work is licensed under a Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) that allows others to share and adapt the material for any purpose (even commercially), in any medium with an acknowledgement of the work's authorship and initial publication in this journal. 768 Green wall design to mitigate highway pollution Mohammed Zuhair Mohamedmeki 1 , Maha Almumaiz 2 1 Highway and Transportation Department, College of Engineering, Mustansiriyah University, Baghdad, Iraq 2 Civil Engineering Department, College of Engineering, Mustansiriyah University, Baghdad, Iraq ABSTRACT Recent studies showed that Baghdad City suffers from highly polluted environment. The enormous traffic congestion and highly number of vehicles, especially during peak hours, is the main source of this pollution. This study is focused on stopping this deterioration by suggesting a green infrastructure to the one of main arterial road of the city (Mohamed Al-Qasim Expressway). The amount of pollutants resulted from traffic fleet have been estimated. It was found that the level of pollution is exceeded the acceptable levels. A combination of vegetation (trees) and green wall (shrubs) has been proposed for designing the green infrastructure for a selected section. Three types of trees namely: Neem tree, Ficus benjamina and Conocarpus have been selected after review many types that can be used for this purpose and resist the extreme hot weather. Two types of shrubs: Myrtus communis and Dodonaea viscosa were proposed due to their suitability for this function of filtering the particulate matters. The maximum ideal annual amount of CO 2 sequestration for 1km of trees planted on road sides and median was about 43.2, 10.5, and 9.25 Tonne for the Neem tree, Ficus benjamina, and Conocarpus, respectively. Keywords: Highway, CO 2 emission, Environmental pollutants, Green infrastructure, particulate matter Corresponding Author: Mohammed Zuhair Mohamedmeki Department, Highway and Transportation University, Mustansiriyah University Baghdad, Iraq E-mail: dr.mohamedmeki@uomustansiriyah.edu.iq 1. Introduction Urban growth became a common problem throughout the world [1] as people left their rural areas and accumulated in major cities [2]. This growth has good economic benefits but at the same time has many environmental consequences [3]; which affect climate change and increase global warming [4]. Numerous studies have revealed the existence of highly percentage of air pollutants to levels above the standard values [5]. Chen et al. (2007) reported that the main air contaminants found in our environment are particulate matter (PM), ozone (O 3 ), CO in addition to NO 2 , SO 2 and CO 2 . In Iraq, especially in capital Baghdad, vast masses of pollutants are emitted in the environment because of many reasons: the trucks run by diesel, buses, heavy-duty building equipment, big number of shared electricity generators of about 15,000 [6] in addition to the highly number of vehicles run by gasoline; which increased after 2003 with a yearly percentage of about 17.5% [7]. Nearly 38% of these vehicles concentrate in Baghdad with about 1.75 million vehicles[5]. Many studies reported that traffic pollutants are the major cause of environmental pollutions all- over the world[6]. These include PM, nitrogen oxides (NOx), CO and volatile organic compounds (VOCS). Traffic pollutants increase the environmental pollution and expose people scattered on, and near roads to the risk of lung diseases, cardiovascular morbidity, asthma [7], mortality , cognitive declines (Health Effects Institute [7]. Environmental Protection Agency (EPA) website (EPA, 2020a) reported that about 50 million people in the United States live close to road environment, within less than 100 m from major roads. Similarly, nearly 40% of people in Toronto live up to 500 m from principal arterial (expressway) or up to 100 m from major roads [8].