Study from Los Angeles shows huge extent of spread of particle air pollution downwind of airport

A study in California looking at air pollution from Los Angeles International Airport has shown far more widespread impacts that had previously been expected. The scientists measured the spatial pattern of particle number (PN) concentrations downwind from the airport with an instrumented vehicle that enabled a larger area to be covered than allowed by traditional stationary measurements. The study found at least a 2-fold increase in PN concentrations over un-impacted baseline PN concentrations during most hours of the day in an area of about 60 km2 that extended to 16 km (10 miles) downwind and a 4- to 5-fold increase to 8–10 km (5–6 miles) downwind. Locations of maximum PN concentrations were aligned to eastern, downwind jet trajectories during prevailing westerly winds. They found the levels of PM miles from the airport were higher than those from motorways. They say “The freeway length that would cause an impact equivalent to that measured in this study (i.e., PN concentration increases weighted by the area impacted) was estimated to be 280–790 km) “The total freeway length in Los Angeles is 1500 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.”

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Emissions from an International Airport Increase Particle Number Concentrations 4-fold at 10 km Downwind

. 2014 Jun 17; 48(12): 6628–6635.
Published online 2014 May 29. 
For a better version of this image, see here 

Abstract

We measured the spatial pattern of particle number (PN) concentrations downwind from the Los Angeles International Airport (LAX) with an instrumented vehicle that enabled us to cover larger areas than allowed by traditional stationary measurements.
LAX emissions adversely impacted air quality much farther than reported in previous airport studies.
We measured at least a 2-fold increase in PN concentrations over un-impacted baseline PN concentrations during most hours of the day in an area of about 60 km2 that extended to 16 km (10 miles) downwind and a 4- to 5-fold increase to 8–10 km (5–6 miles) downwind. Locations of maximum PN concentrations were aligned to eastern, downwind jet trajectories during prevailing westerly winds and to 8 km downwind concentrations exceeded 75 000 particles/cm3, more than the average freeway PN concentration in Los Angeles.
During infrequent northerly winds, the impact area remained large but shifted to south of the airport. The freeway length that would cause an impact equivalent to that measured in this study (i.e., PN concentration increases weighted by the area impacted) was estimated to be 280–790 km.
The total freeway length in Los Angeles is 1500 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.
…. and there is a lot more ……

Recommendations for Other Studies

LAX is in a region of Los Angeles with highly consistent wind direction. This provided the several hours necessary for a single mobile platform to monitor a sufficient number of transects to cover the large area impacted by LAX emissions. At airport locations where the prevailing wind direction frequently shifts during the day, multiple platforms would be necessary to quickly capture the full spatial extent of emissions impacts to surrounding air quality.

The emissions from LAX are likely not unique on a per-activity basis. The large area of impact from LAX suggests that air pollution studies involving PN, localized roadway impacts, or other sources whose impacts are in the influence zone of a large airport should carefully consider wind conditions and whether measurements are influenced by airport emissions.

Source apportionment of specific airport sources or activities was beyond the scope of our study but would be necessary to evaluate the effectiveness of possible mitigation options. Differing NO2 to NOx ratios at different levels of engine thrust might be used to distinguish the contributions of jet landing, idling or takeoff activities. Takeoff and idling emission also differ in surface properties (i.e., the ratio of active surface area to surface bound photoionizable species) and particle size distributions differ between aircraft and ground support equipment emissions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4215878/

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