By Chris Bowman
Bee Staff Writer
(Published Oct. 3, 2000, Sacramento Bee; Links added by FRAQMD)

Doubling the number of mature trees and resurfacing dark-colored roads and roofs with brighter, heat-reflecting material throughout Sacramento County would nearly halve the amount of smog exceeding national air quality standards in the region, soon-to-be-published scientific research shows.

The unusual remedy wouldn't cut much smog in the little more than four years the county has left to meet its federally mandated clean-air deadline.

But the pair of studies by the University of California's Lawrence Berkeley National Laboratory for the first time quantifies the air quality benefits accrued over time from relatively inexpensive, energy-saving changes to the urban landscape.

"This is the first study that is a comprehensive analysis of the fabric of a city, the energy savings and the air quality benefits," said Hashem Akbari, a Lawrence Berkeley scientist with the lab's "heat island" research group (Heat Island Group home page).

The $1 million in research funded by the U.S. Environmental Protection Agency makes a case study of the Sacramento area. The Lawrence Berkeley researchers assembled aerial photographs of the county detailed enough to see major streets and individual rooftops. Instruments aboard the jet also took infrared readings that measure the heat reflected from surfaces.

In the past four years, technicians from the NASA Marshall Space Flight Center in Huntsville, Ala., have flown jets equipped with infrared cameras over Salt Lake City; Baton Rouge, La.; Atlanta; Houston and Sacramento, producing block-by-block temperature maps -- mosaics of primary colors keyed to temperature ranges. The hottest spots in each city were found to be rooftops, which can reach peak temperatures of 160 degrees, followed by parking lots paved with dark materials. The urban parks and forests are coolest.

Sacramento County, like most population centers in the country, is what scientists call a "heat island" or "reverse oasis," meaning the urban area is hotter than the surrounding countryside because of the prevalence of black pavement and dark roofs and lack of trees.

On hot summer afternoons, the county is 1 to 2 degrees hotter than the air in lesser-developed areas, according to a copy of the Sacramento study obtained by The Bee.

Increases in temperature speed the formation of smog -- mainly ozone gas -- which is produced when sunlight reacts with automobile pollutants. And when it's hotter, trees emit more smog-forming volatile organic compounds into the air.

Thus, anything that takes the sizzling edge off a hot day cuts smog.

So, when the temperature is lowered by having more shade and heat reflecting surfaces less ozone or smog is produced.

"It is one of the nicest environmental science tricks you can use to clean up the air," said Arthur H. Rosenfeld, a member of the California Energy Commission, one of 14 agencies and businesses backing the Sacramento Tree Foundation's promotion of "cool" pavement and roofing.

Next year, the energy commission plans to amend the state building code to provide energy conservation credits all builders need to those that incorporate "cool" designs in their projects, Rosenfeld said.

"It's a market incentive we can offer until it catches on or becomes mandatory," he said.

Trees also cut smog by absorbing air pollutants, according to scientists with the U.S. Forest Service Western Center for Urban Research and Education at UC Davis.

In a 1998 study, scientists at the center found that Sacramento County's 6 million trees annually take up 1,606 tons of smog-forming pollutants and harmful particles, using other ways to cut those tons would cost $28.7 million a year, the study said.

Doubling the number of trees and cooling roof and pavement surfaces throughout Sacramento County would lower peak air temperature 2 to 3 degrees, more than reversing the elevated temperatures generated by the urban area, according to the Lawrence Berkeley study by Akbari and fellow researchers Haider Taha and Sheng-chieh Chang.

When afternoon temperatures are lowered 2 to 3 degrees, ozone levels fall by 7 to 10 parts-per-billion, a 6 to 8 percent drop that is about half the reduction the region needs to meet national air quality standards, the scientists calculate.

A study published last year by the same research group provided the first detailed look at the mix of land coverage in the Sacramento metropolitan area. Among its findings:

- Nearly two-thirds of the metropolitan area is paved or covered by buildings, the rest is made up mainly of grass, trees and water.

- The vegetated surfaces range from 2 percent along Florin Road to a 40 percent in residential Carmichael.

- Tree shades 13 percent of the metropolitan area. Midtown has the most extensive canopy in the county, with 27 percent tree cover.

One hot afternoon last July, the Sacramento Municipal Utility District demonstrated the effect of planting shade trees by measuring the temperature in the air and on the asphalt in two neighborhoods (visit SMUD's web site).

The asphalt street cooked at 135 degrees while the ambient air measured 95 in a shadeless, newly built housing track at West Stockton Boulevard and Wooded Brook Drive in Elk Grove.

In east Sacramento, which has a lot of trees, the asphalt near 37th and P streets registered 95 degrees on SMUD's laser heat gun and 84 degrees in the air.

Starting next year, SMUD plans to offer rebates to contractors of commercial and office buildings that use white roof coatings bearing the Energy Star seal of approval, said Misha Sarkovich, the utility's manager of the program (visit EPA's Energy Star web site).

"It's like putting sunblock on your skin," Sarkovich said. "Certain chemicals in roof coatings reflect ultraviolet rays. Not all white paint has them."

Sarkovich, who also serves on the Fair Oaks Parks and Recreation District board, said he is helping design what will be the first "cool community" project in the county at Bannister Park. Among other heat-reducing designs, the district plans to use cooler concrete instead of asphalt for the parking lot.    -End of Article -