Airport Particle Emissions More Widespread Than Previously Believed
Emissions from turbine aircraft are one of the main objections held by those who want southern California’s busy Santa Monica Airport closed, yet in a recently released study, emissions from nearly Los Angeles International Airport (LAX) suggest an unexpectedly severe impact on residents downwind of major airports.
The Santa Monica city council is considering a graduated hydrocarbon emissions limit scheme that could eventually disallow many jets from using the airport, but the legality of that move remains questionable. However, local politicians whose constituents live near Santa Monica Airport and/or LAX do not seem concerned about the likelihood that turbine-engine emissions at LAX are significantly higher than those at Santa Monica. None of the politicians or their staffers had responded to AIN’s questions about the emissions study as of June 20.
The study, published in Environmental Science & Technology on May 29, found that “LAX emissions adversely impacted air quality much farther than reported in previous airport studies.” Using an instrumented vehicle, the scientists measured “the spatial pattern of particle number (PN) concentrations downwind of LAX…” Unlike earlier studies that measure emissions close to the airport or at fixed locations, this one sought to find out how far downwind and away from the runway centerline the emissions remained at high levels.
The measurements showed that baseline PN concentrations 10 km downwind were four times higher compared to nearby unimpacted baseline concentrations. A two-fold increase was found 16 km downwind, and five-fold at 8 km from the airport. “Within 3 km of the airport boundary, concentrations were elevated nearly ten-fold, exceeding 100,000 particles/cm3, with concentrations of 150,000 particles/cm3 occurring over an area of several square kilometers.”
These levels are higher than would be expected from local freeway traffic, according to the study: “The freeway length that would cause an impact equivalent to that measured in this study (that is, PN concentration increases weighted by the area impacted) was estimated to be 280-790 km. The total freeway length in Los Angeles is 1,500 km. These results suggest that airport emissions are a major source of PN in Los Angeles that are of the same general magnitude as the entire urban freeway network. They also indicate that the air quality impact areas of major airports may have been seriously underestimated.”
Unlike LAX, Santa Monica Airport is surrounded by homes and offices adjacent to the airport property. A study of ultrafine particle emissions at Santa Monica Airport in 2009 found, “Aircraft operations led to an increase of 10 and 2.5 times the concentration of [ultrafine particles] over background levels at 100 and 600 meters downwind, respectively.” The LAX study did not break the particles into specific particle sizes, so it does not show a number for ultrafine particles.