Incoming: More to Trans-Boundary Ozone impacting California than ‘hot air’

There is no question pollution is adrift in the air. The past couple of days, air quality in the Fresno region of California has been good. Connected to this have been lower temperatures. Daytime temps have been in the 90s. But this is going to change. Temperatures are already starting to warm and by the weekend, they will probably be in the triple digits in most, if not all parts, of the San Joaquin Valley.

With higher temperatures what will undoubtedly come with that is worsening air quality. Specifically, the Valley’s notoriously high temps this time of the year allow ozone to form; smog that typically builds with persistent heat and lack of filtering rains or winds. It is the combination of ozone precursors such as nitrogen oxides (NOx) and Volatile Organic Compounds (VOC) like methane from dairies in the presence of heat, that help drive ozone formation.

But there remains a nagging question: How much of this ozone originates onshore and how much of it is Trans-Boundary Ozone or TBO from elsewhere, say, Asia, for example and why is learning specifically where the latter is sourced from important?

According to Bakersfield Californian newspaper staff writer Steven Mayer on Sept. 1, 2013 in “Valley air pollution: Made in China?” several studies have already been initiated in this regard. Pinpointing TBO sources is key.

A one-and-a-half-year University of California at Davis study relied on aircraft aerial surveillance “to help determine whether long-distance flows of ozone from Asia are mixing with valley air,” Mayer wrote.

California's agriculturally rich but often air-pollution shrouded San Joaquin Valley
California’s agriculturally rich but often air-pollution shrouded San Joaquin Valley

Another study, initiated by lead University of Colorado atmospheric scientist Owen Cooper utilized “a network of four balloon-launch sites along the California coast, and more sites inland, to gather ozone readings at various altitudes,” wrote Mayer, and “[p]ublished in 2011 by the Journal of Geophysical research [sic], the study used ozonesondes, balloon-borne instruments that measure concentrations of ozone at different altitudes and broadcast the data back to researchers.

“… [I]n the free troposphere above 3 kilometers, or just under 2 miles in altitude, ozone precursors, or smog-producing chemicals, were found by Cooper’s team. The main sources? China and international shipping.”

But, how can it be for certain sources are definitively identified?

Mayer cited David Lighthall, a San Joaquin Valley Air Pollution Control District (SJVAPCD) health and science advisor and TBO research coordinator, who in effect expressed that via tiny bits of soot having their own unique “elemental signatures” and when mixed in an ozone plume and carried by winds, for example, origins of such particles can then be determined, according to what I understand.

However, the Bakersfield Californian staff writer also noted that another ozone researcher, David Parrish, with the NOAA’s (National Oceanic and Atmospheric Administration) chemical sciences division located in Boulder, Colo., contends all problems related to ozone mustn’t be blamed on China further noting, absent ozone produced locally, very rarely, if at all, would the Los Angeles and San Joaquin Valley air basins record health-standard exceedances.

“And our imported ozone is certainly not all coming from China, [Parrish] said. Other Asian countries, Europe, international shipping and natural ozone sources all contribute, he said. In fact, ozone can circle the globe, so smog and its precursors created in the United States can similarly affect other nations.”

TBO’s effect becomes “diluted” in its west-to-east travels over North America, related Mayer in citing Parrish.

More related research seems warranted.

The importance, meanwhile, of learning the sources of pollution, and ozone specifically, that hitchhike around the globe via currents of air should help in establishing the “fairness” or “appropriateness” of an imposed yearly $29 million fine, split among Valley business owners and motorists alike that both must pay, all on account of a federal one-hour ozone standard of health not being met. The Valley must be in attainment of this standard for three consecutive years in order for the imposed annual fines to be erased. It is my understanding Valley motorists are responsible for around $25 million, business owners on the hook for the remainder.

Ozone levels overall in the Valley have been trending negatively.

Added Mayer: “In layman’s terms, nearly one-quarter of Kern County’s ozone problem may be attributable at times to off-shore sources, making it completely beyond local control. Add another 8 to 9 percent coming from upwind sources in California and it’s hard not to conclude that south valley residents have limited influence over the very air we breathe.”

I plan to provide more related updated information upon its availability.


Some information in this blog post was accessed via written communication with representatives of the SJVAPCD.

This post was last revised on May 8, 2020 @ 11:32 a.m. Pacific Daylight Time.

– Alan Kandel