Quantifying metal emissions from vehicular traffic using real world emission factors

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Public Health

Background:

• Road traffic is a major source of urban particulate matter.
• Non-tailpipe emissions from vehicles contribute significantly to metal pollution.
• Understanding traffic-emitted metals is crucial for assessing health risks.

Purpose of the Study:

• To determine real-world emission factors for fine particulate metals from road traffic.
• To investigate spatial and temporal variations in these metal emissions.
• To identify factors influencing metal emission rates.

Main Methods:

• Hourly X-ray fluorescence measurements over three years (2015-2018).
• Data collected at an urban roadway and a busy highway.
• Analysis of inter-site differences and temporal trends.

Main Results:

• Emission factors for Ti, Fe, Cu, and Ba were 2.2-3.0 times higher at the highway site, linked to heavy-duty vehicles.
• Weekday emissions for Mn, Zn, Ca, and Fe were 2.0-3.5 times higher than Sundays.
• Metal emissions decreased with higher relative humidity and precipitation due to reduced dust resuspension.

Conclusions:

• Emission factors varied significantly based on vehicle fleet composition and traffic volume.
• Traffic-related metal emissions can be isolated and quantified.
• Human exposure to airborne metals fluctuates spatially and temporally due to traffic dynamics.