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POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS IN THE REMOTE NORTH ATLANTIC MARINE ATMOSPHERE (R825377)
Citation:
Hites, R. A. AND J. I. Baker. POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS IN THE REMOTE NORTH ATLANTIC MARINE ATMOSPHERE (R825377). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33:14-20, (1999).
Description:
We have developed a sampling strategy that allows us to determine
femtogram/cubic meter concentrations of polychlorinated dibenzo-p-dioxins
and polychlorinated dibenzofurans (PCDD/F) in remote marine atmospheres. Using
this sampling strategy, a total of 37 air samples were taken during two extended
sampling periods at Bermuda between September 1993 and August 1997. During this
time, the average total PCDD/F concentrations at Bermuda decreased from 105 ? 30
to 35 ? 10 fg/m3, giving a half-life of about 2 years for these
compounds in the remote marine atmosphere. PCDD/F concentrations during both
sampling periods were somewhat higher in the winter when air parcels originated
from North America. A second air-sampling station was established at Barbados
where 22 air samples were taken between March 1996 and August 1997; an average
total PCDD/F concentration at Barbados of 15 ? 7 fg/m3 was found.
This value was not significantly different than the 27 ? 7 fg/m3
found at Bermuda during this time when air arrived from the east. This indicated
that the remote marine background concentration for these compounds is currently
on the order of 20 fg/m3. Using these background concentrations, the
dry depositional rate of PCDD/F to the world's oceans was estimated to be 200 ?
80 kg/year, and the wet depositional rate was estimated to be 900 ? 300 kg/year.
This is a total deposition rate of about 1 t/year to the oceans as compared to
our previous estimate of 12 t/year PCDD/F deposition from the atmosphere to the
land.