|
March 7, 1997
A weekly feature provided by scientists at the Hawaiian Volcano
Observatory.
Kilauea sulfur dioxide emissions down by 90%
The smell of sulphur is strong but not
unpleasant to the sinner
--Mark Twain, 1866
Sinners or not, many of us living on the island of Hawai`i over the
past decade feel that, although we cherish the volcanoes, the smell of
sulfur gas and volcanic air pollution, or vog, from Kilauea has become
decidedly unpleasant. Currently, we are experiencing the clean air
quality that many residents and visitors remember from before 1986,
when the Kilauea east rift zone eruption became continuous, and a
daily, steady supply of gas accumulated, rather than being dispersed by
the winds.
Lately, air in leeward Hawai`i has been very clear, with little
volcanic haze to obscure the view of the mountains and coastal areas.
Interrupted trade winds usually cause east Hawai`i to be inundated with
large amounts of sulfur dioxide (SO2) gas and sulfate
particles from Kilauea. During a recent interruption in trade winds,
however, levels of ambient SO2 measured near the summit of
Kilauea were significantly lower than what has become
`normal' for the last 10 years.
This period of better air quality is a direct result of the low
level of current eruptive activity. After the collapse of Pu`u `O`o and
the start of eruptive episode 54 early in the morning on January 30,
east rift zone SO2 gas emissions were 15-30% of the 2,000
tons per day or so that we have measured during eruptively active
periods over the last several years. When the short-lived episode
ended on January 31, SO2 emissions decreased even further.
Although there is lava ponding, once again, within Pu`u `O`o, current
SO2 emissions from Kilauea appear to be less than 10% of the
daily emission rates measured since 1993.
This 90% decrease in released SO2 gas from Kilauea is
very good news for Kona residents, for it means that there is simply
much less gas to be blown by the prevailing trade winds from degassing
sources on Kilauea around South Point, and up along the Kona coast,
where it is trapped by the onshore-offshore daily wind regime. On this
journey, there is also less gas to react chemically with sunlight,
oxygen, dust and water to form the sulfuric acid and other sulfate
particles that cause the visible pollution that had become so
ubiquitous for Kona residents and visitors.
The significant decrease in SO2 gas emissions is good
news for east Hawai`i residents too. During periods of interrupted
trade winds, areas from Volcano to lower Puna to Hilo, and even
Hamakua, can be impacted by vog. Residents living close to the gas
emission sources at the summit and middle east rift zone, have
periodically experienced high levels of SO2 gas. At a site
near the park headquarters in Hawai`i Volcanoes National Park, ambient
concentrations of SO2 exceeded the EPA primary health
standard of 0.139 parts per million on nearly 70 occasions over the
past 10 years.
Residents and visitors alike should enjoy this interlude of cleaner
air, for it is presently unclear whether the current low level of
activity at Kilauea will persist. Since roughly 8 pounds of
SO2 gas bubbles out from each cubic yard of magma as it
rises toward the surface to erupt as lava, a lower eruption rate of
lava releases less gas, which, in turn, will produce less vog.
There have been periods of little (1894-1907) or no activity
(1934-1952) at Kilauea since the start of the historic period in 1790.
Since the 1950s, however, eruption rates have increased dramatically,
with rates for each ensuing decade surpassing those of the previous
decade. So, although the vog `problem' has largely
disappeared for now, it is probable that we will once again be faced
with high vog episodes on the Big Island in the future.
The health effects of vog are not well documented, although
anecdotal reports from health-care professionals and other Big Island
residents include headaches, fatigue, respiratory difficulties, and
allergy complications during extended periods of poor air quality.
Studies from urban areas with pollution of similar composition show
that acidic aerosols, such as those comprising vog, can degrade lung
function and compromise our immune systems, especially for vulnerable
individuals, such as children, the elderly, and asthmatics.
In pursuing the goal of obtaining relevant information on vog, the
Hawai`i State Department of Health has engaged scientists from the
University of Hawai`i, and University of Southern California medical
school to examine the health effects of vog on school children. At
the U.S. Geological Survey's Hawaiian Volcano Observatory, we
are continuing to improve our measurements of the source of the vog.
An extended lull in eruptive activity, like the one we are currently
experiencing, can be beneficial to health studies by providing a sharp
contrast to periods of bad air quality. We all look forward to the
fruits of this research.
The URL of this page is
http://hvo.wr.usgs.gov/
Contact:
webmaster@wwwhvo.wr.usgs.gov
Updated :
|