10.1021/es0206893.s001
Holly A. Bamford
Holly A.
Bamford
Fung Chi Ko
Fung Chi
Ko
Joel E. Baker
Joel E.
Baker
Seasonal and Annual Air−Water
Exchange of Polychlorinated
Biphenyls across Baltimore Harbor
and the Northern Chesapeake Bay
American Chemical Society
2002
PCB inventory
Northern Chesapeake Bay
sampling
residence time
Baltimore Harbor
MD
PCBs
AEOLOS
Chesapeake Bay site
PCB volatilization fluxes
O ceans S tudy
tmospheric E xchange O ver L akes
Baltimore Harbor exchanges
2002-09-19 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Seasonal_and_Annual_Air_Water_Exchange_of_Polychlorinated_Biphenyls_across_Baltimore_Harbor_and_the_Northern_Chesapeake_Bay/3597174
As part of the <i>A</i>tmospheric <i>E</i>xchange <i>O</i>ver <i>L</i>akes and
<i>O</i>ceans <i>S</i>tudy (AEOLOS), air−water exchange fluxes of
polychlorinated biphenyls (PCBs) were determined along
a transect in the Baltimore Harbor from the Inner Harbor of
Baltimore, MD, to the mainstem of the northern Chesapeake
Bay to assess the overall contributions of urban source
PCBs through air−water exchange and their impacts on
coastal waters. Six sites were sampled during three intensive
sampling periods in June 1996, February 1997, and July
1997 and at two sites (urban and rural) every ninth day
between March 1997 and March 1998 to measure spatial
and temporal variability in the PCB air−water exchange fluxes.
During the intensive sampling campaigns, net total PCB (<i>t</i>-PCBs) volatilization fluxes ranged between 5 and 2120
ng m<sup>-2</sup> day<sup>-1</sup>, varying on both temporal and spatial scales.
Volatilization fluxes were highest in February, driven by
high winds and elevated dissolved PCB concentrations.
Throughout the annual sampling period, <i>t-</i>PCB volatilization
fluxes were similar between urban (130 μg m<sup>-2</sup> yr<sup>-1</sup>)
and rural (120 μg m<sup>-2</sup> yr<sup>-1</sup>) sites. Approximately 10% of
the dissolved <i>t</i>-PCB inventory in the water column in Baltimore
Harbor exchanges with the atmosphere each day. From air−water exchange alone, the estimated residence time of
dissolved <i>t-</i>PCBs in the harbor is approximately 10 days
(estimated hydraulic residence time of water in the harbor
is between 7 and 14 days), indicating that air−water
exchange is an efficient removal mechanism of <i>t</i>-PCBs
from urban coastal waters. Furthermore, the annual flux of
<i>t-</i>PCBs volatilizing from Baltimore Harbor is approximately
12% of the gas-phase <i>t-</i>PCB inventory over the water,
and at the northern Chesapeake Bay site, the <i>t-</i>PCB flux
is approximately 40% of the gas-phase <i>t-</i>PCB inventory. This
suggests that air−water exchange of <i>t-</i>PCBs has the
potential to be a significant source of PCBs to the rural
atmosphere.