Casco Bay Air Deposition Monitoring ProjectEntry ID: gomc_97
Abstract: The Casco Bay Estuary Partnership is devoted to protecting and
restoring the water quality, and fish and wildlife habitat of the Casco Bay
ecosystem, while ensuring compatible human uses. Atmospheric deposition is a
natural process by which pollutants are transferred from air to soil, surface
water, sediment, and groundwater and potentially to living organisms. Wet and
... dry deposition processes (e.g., rain out, wash out, impaction, adsorption, and
absorption) remove particulate and gaseous pollutants from the atmosphere and
deposit them on the surface of water bodies, vegetation, buildings and
structures, and soil. Transfer of these pollutants from water bodies to
sediment occurs through adsorption and sedimentation. Polluted water and
sediment lead to undesirable health and environmental impacts, such as
mercurycontaminated fish, harmful algal blooms, beach closures, etc. The
current role of atmospheric deposition, as it relates to nitrogen, mercury, and
fine particulate matter (PM2.5) pollution in Casco Bay, needed to be better
understood and quantified.
Atmospheric deposition (estimated dry and wet deposition) of inorganic nitrogen
is a significant source of pollution to Casco Bay.
Atmospheric deposition of mercury is the dominant source of mercury to the
From 1998 to 2001, there was a trend of declining annual wet deposition of
mercury, ammonia, and nitrate totals at Casco Bay.
Other Instruments: MDN,NADP, IMPROVE samplers
Waterbody or Watershed Names: Casco Bay
Purpose: Develop atmospheric deposition loading estimates to guide water
quality and air quality management decisions.
Sponsor: U.S. Environmental Protection Agency
Materials and Methods: NADP, MDN and IMPROVE national protocols followed.
QAPP for the trace metals sampling available.
Sample Site Locations: The Study's long-term monitoring station has been
... located on Wolfe's Neck Farm, an organic beef farm in Freeport, ME. The site is
located in a hay field, on a peninsula 1/4 mile from Casco Bay.19. and 20.
Sample Numbers and Frequency - NADP collector - weekly wet deposition samples
collected every Tuesday, total of 52 samples/year. MDN Collector - weekly wet
deposition samples collected every Tuesday, total of 52 samples/year. PAH
Collector (March 1998 - March 2001 only) - twelve weekly samples each of wet
and dry deposition collected monthly, total of 24 samples/year. In 2000,
seasonal samples of wet and dry deposition were collected weekly during one
month per season (January, April, July, October). IMPROVE sampler - one sample
(three filters, one each from Module A, B, and C) collected every six days,
total of 156 samples/year.
(Click for Interactive Map)
This data set description is a member of a collection. The collection is described in
Start Date: 1990-01-01Stop Date: 2003-01-01
Temporal Resolution Range: Daily - < Weekly
Quality NADP, MDN and IMPROVE national protocols followed. QAPP for the trace metals
We focused validation efforts on the Casco Bay data and performed only a
cursory review of the data from other sites. Time series plots are provided in
Appendix B. 2-10 No Casco Bay IMPROVE data were flagged. A few samples appeared
... odd compared to others (i.e., stood out on scatter plots as outliers)8;
however, three of these samples appeared to be from dust events identified by
high concentrations of calcium (March 1, 2000), silicon (January 29, 1998),
aluminum and iron (May 24, 2000) and one from increased marine (sodium and
chloride) influence (March 1, 1999). We noted two troubling items: Comparison
of the XRF sulfur and sulfate ion concentrations at Acadia shows excellent
agreement while the same comparison at Casco Bay shows much more scatter
(Figure 2-3). In addition, the relationship between the two measurements
appears to change from year to year at Casco Bay. Researchers at the University
of California, Davis, recommend using the Teflon PIXE-derived sulfur values as
the measure of sulfate because of possible adsorption of sulfur dioxide (SO2)
on the nylon filter (from which sulfate values are derived). This possible SO2
adsorption would be indicated by sulfate values from the nylon filters being
greater than sulfate values from the Teflon filters. A large number of the data
values show the opposite of this trend in Figure 2-3 (especially all of 2000).
We are not sure of the cause of this difference.
The reconstructed fine mass and measured PM2.5 correlate reasonably well at
both Acadia and Casco Bay (Figure 2-4). However, the Casco Bay data show more
scatter than Acadia, and the 1998 Casco Bay data have the most outliers. We
used RCFM+marine to compute fractions of key PM2.5 components. Since we are not
using these data to estimate deposition, but rather to investigate potential
pollutant source types and regional transport, these validation items are not
critical to the conclusions of this report.
For the NTN data, we flagged the potassium concentration as suspect in the
weekly sample collected ending on June 14, 1999, at Casco Bay. The potassium
concentration was nearly an order of magnitude higher than in any other sample
(Figure 2-5). This sample was not used in subsequent analyses. The sample
collected ending on March 30, 1999, exhibited high concentrations of several
species, but the relationships were similar to other samples; therefore, the
sample was not flagged. Field and lab pH values matched reasonably well (Figure
We did not apply any additional flags to the MDN data. For the CASTNet data, we
used annual average data only and did not perform a quality assurance/quality
control (QA/QC) review of the individual data. We recommend that a QA/QC review
of this data be made in the future.
Very few problems were noted in the Casco Bay data, indicating that sampling
and analysis protocols were being followed properly.
Access Constraints Public
Use Constraints Very few problems were noted in the Casco Bay data, indicating that sampling
and analysis protocols were being followed properly.
Data Set Progress
Distribution Media: Online Internet (HTTP)
Distribution Format: PDF
Role: DIF AUTHOR
Phone: (207) 780-4820
Fax: (207) 780-4317
Email: gould.diane at epa.gov
USM Muskie School P.O. Box 9300
Province or State: ME
Postal Code: 04104
Ryan, Patrick A., Hilary Hafner, Steven G. Brown. Deposition of Air Pollutants
to Casco Bay, Casco Bay Estuary Project, 2003
Golomb, Dan. Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons near
New England Coastal Waters, Atmospheric Environment, (35) 6245 - 6258.
Deposition of Air Pollutants to Casco Bay Sonoma Technology, Inc. Report, 6/03
Estimating Estuarine Pollutant Loading From Atmospheric Deposition Using Casco
Bay, 5/03 (PDF)
Creation and Review Dates
DIF Creation Date: 2006-08-28
Last DIF Revision Date: 2009-04-28