U.S. Water News Online
SOUTH LAKE TAHOE, Calif. -- Experts are studying whether
air pollution from Sacramento threatens the environmental health of
the Lake Tahoe basin.
A study released recently by the Surface Transportation Policy
Project, a Sacramento-based, nonprofit organization focused on
transportation reform, ranked Sacramento fifth out of the top 10
clean-air-offending cities in the country.
While scientists agree pollutants from Sacramento are reaching the
Tahoe basin 100 miles to the east, they're not sure if it's enough to
cause lake damage or health problems.
Using data from the U.S. Environmental Protection Agency, the
study ranked metropolitan areas by how many days their air pollution
levels exceeded national health standards during a three-year period.
All of the top five cities in the nationwide survey were in
California, three in the Central Valley.
``Tahoe is definitely being impacted by pollution from Sacramento
and the Bay area,'' Jennifer Quashnick, an Air Quality Program
Manager with the Tahoe Regional Planning Agency, told the Tahoe Daily
``We've known for years that we can have transport of pollutants
in the wind.''
A study made a few years ago revealed mercury in the lake's floor.
``There were no mercury activities in the basin, so it had to come
from outside,'' said John Reuter, a professor at the University of
California, Davis who has studied Lake Tahoe since 1978.
The TRPA has also observed an increase in the ozone around Tahoe
at night, an indication that pollution is coming from outside the
basin since local ozone normally rises with the heat of the day,
Scientists say Tahoe's elevation shields it from the brunt of the
Central Valley's pollution. Ozone is carried up the western slope of
the Sierra Nevada, but by the time it reaches Tahoe, it either blows
across the lake high above ground or is diluted enough not to be a
problem at ground level.
``As far as we know, it's not polluting the lake and it's not
having a big impact on people,'' said Tom Cahill, who teaches
atmospheric science and physics at UC Davis. ``But it's a cautionary
tale because it shows how efficiently it can be transported.''
But the pollution is affecting Jeffrey pines, Cahill said.
Increased ozone levels make the trees' needles age faster, resulting
in bare branches with green tips on the end.
Not all pollution found in Tahoe comes from outside the basin.
Quashnick said that while southwest summer winds blow in
contaminants, in the winter all pollution is generated locally.
The Placer County Air Pollution Control District reported that the
majority of pollution in Tahoe comes from wood-burning stoves and
``It's both in-house and out-of-house,'' said Reuter.
Whether Sacramento's smog is having a major impact on the lake
remains to be seen.
``No doubt bad air quality is getting into the lake. The question
is -- how much and is it a big deal?'' Reuter said.
The California Air Resources Board, along with the TRPA, EPA, and
the Lahontan Regional Water Quality Control Board, is conducting a $2
million study to track how much pollution is entering the basin from
Data should be available this winter.
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