ARB Research Seminar

This page updated May 23, 2017

Effectiveness of Sound Wall-Vegetation Combination Barriers as Near-Roadway Pollutant Mitigation Strategies

Photo of Suzanne Paulson

Suzanne Paulson

Photo of Yifang Zhu

Yifang Zhu

Photo of Akula Venkatram

Akula Venkatram

Suzanne Paulson, Ph.D., Professor, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles; Yifang Zhu, Ph.D., Associate Professor, Environmental Health Sciences Department, Fielding School of Public Health, University of California, Los Angeles; Akula Venkatram, Ph.D. Professor, Department of Mechanical Engineering, University of California, Riverside.

June 06, 2017
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA


Presentation
Video
Research Project

Overview

Traffic-related air pollutants are a significant public health concern near freeways. Previous studies have suggested that soundwall and/or vegetation barriers (defined here as any substantial installation of vegetation on either side of the sound barrier, trees or tall bushes etc.) may reduce near-freeway air pollution, but the literature is inconsistent, and data for vegetation and other conditions common in California are very limited. This research project combined mobile and stationary measurement and modeling approaches to evaluate the impact of various barrier configurations at four sites in California, and made pair-wise comparisons of the following configurations: no wall, sound wall only, vegetation only, and combined soundwall-vegetation combinations (eight study locations in total, each with a perpendicular transect). Chosen study sites were located along major highways in Santa Monica, Encino, Sacramento and Riverside, and if present, trees were substantially taller than the solid barriers. Three of these sites were chosen as test sites for daytime conditions (Sacramento, Encino and Riverside) and one was chosen for nighttime and early morning conditions (Santa Monica).

Mobile and stationary measurements were conducted on transects perpendicular to the main roadway. Stationary measurements for wind, ultrafine particles (UFP) and oxides of nitrogen were made on both sides of the soundwall. Mobile measurements were made using an electric vehicle for several hours each day during one to three week field campaigns, and included high time-resolution measurements of UFP, oxides of nitrogen, carbon dioxide, and PM₂.₅ (particulate matter with diameter ≤ 2.5 Ám). A dispersion model was developed and applied to analyze data from two of the field studies at Riverside and Sacramento, and provides technical and planning guidance on the effectiveness of soundwall-vegetation combinations for mitigating near-roadway air pollution.

The study concluded that dense vegetation that is taller than the barrier appears to be a clear benefit during daytime as well as early morning. The benefit is significant especially very close to the barriers, but it decays quickly, such that other mitigations might also be worth considering, especially for sensitive receptors.

Speaker Biography

Suzanne Paulson, Ph.D., is a Professor in the Department of Atmospheric and Oceanic Sciences and a Professor in the Institute of the Environment at UCLA, where she serves as the director of the Center for Clean Air. Dr. Paulson's current research studies the impact of naturally occurring and human-made particles on public health and the Earth's climate. Her research also focuses on the influences of the built-environment on air pollution levels in complex urban areas. Professor Paulson teaches climate change and air pollution to undergraduate and graduate students and has given numerous invited public lectures on related topics. She was featured in numerous radio, print, and video interviews for her work in air quality in the Los Angeles area. Currently, Professor Paulson serves on the Research Screening Committee for the California Air Resources Board and serves as an Airport Commissioner for the City of Santa Monica. She has received a National Science Foundation CAREER award for her research. Professor Paulson earned a B.A. in Chemistry from the University of Colorado and a Ph.D. in Environmental Engineering Science from the California Institute of Technology.

Yifang Zhu, Ph.D., is an Associate Professor of the Environmental Health Sciences Department in UCLA Fielding school of Public Health, University of California, Los Angeles (UCLA). Dr. Zhu's research interest is primarily in the field of air pollution, exposure assessment, and aerosol research. Specifically, she is interested in quantitative exposure/risk assessments on ultrafine particles that have shown higher toxicity than larger particles on a unit mass basis. Dr. Zhu has published more than 70 peer-reviewed journal articles and book chapters, and received several national and international awards including UCLA Chancellor Scholarship, the National Science Foundation (NSF)'s Faculty Early Career Development (CAREER) Award, the Walter Rosenblith New Investigator Award from the Health Effects Institute, and the 2011 Haagen-Smit Prize from Atmosphere Environment in recognition of her outstanding publication on ultrafine particles near major freeways. Dr. Zhu was appointed to California Air Resource Board's (CARB) Research Screening Committee in 2014. She received her B.Eng. in Environmental Engineering from Tsinghua University in 1997 and her Ph.D. in Environmental Health Sciences from UCLA in 2003.

Akula Venkatram, Ph.D., is a Professor at the Department of Mechanical Engineering at University of California, Riverside. Dr. Venkatram is an expert in micro-meteorology and air pollution dispersion modeling. Dr. Venkatram has over a decade of experience at ENSR Consulting and Engineering and served as the Head of Department at Ontario Ministry of the Environment in Toronto, Canada, before accepting his current position at UCR. Professor Venkatram pursues research in comprehensive modeling of systems governing air quality, theoretical aspects of small-scale dispersion, application of micro-meteorology to dispersion problems, and development of simplified models for complex urban systems. Professor Venkatram's current research focuses on air quality impacts of various anthropogenic sources in urban environments. Professor Venkatram has received Scientific and Technological Achievement Award from the U.S. Environmental Protection Agency for his contribution in air pollution research. Dr. Venkatram earned his B.S. in Mechanical Engineering from the Indian Institute of Technology at Madras, India, and his Ph.D. in Mechanical Engineering from Purdue University at West Lafeyette, Indiana.


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for the seminars please view the Main Seminars web page

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