AIRMoN Deposition Program
Background.
The Atmospheric Integrated Research Monitoring Network
is an array of stations designed to provide a research-based
foundation for the routine operations of the nation's deposition
monitoring networks -- the
National Atmospheric Deposition Program (NADP) for wet deposition,
and the Clean Air Status and Tends Network (CASTNet) for
dry. A subprogram is specifically designed to detect the
benefits of emissions controls mandated by the Clean Air
Act Amendments of 1990, and to quantify these benefits
in terms of deposition to sensitive areas.
AIRMoN combines two previously-existing deposition research
networks that have appropriate characteristics (previously
known as the MAP3S precipitation chemistry network and
the CORE/satellite Dry Deposition Inferential Method network)
under a single operational umbrella, so as to generate
a new monitoring activity to which on-line modeling and
analysis can be easily applied. An air-sampling component
of AIRMoN provides some unique information on changes in
air quality.
 The techniques of AIRMoN are designed to quantify the
extent to which changes in emissions affect air quality
and deposition at selected locations. A small array (about
20 to 30) such locations are presently intended for eventual
attention of this kind. AIRMoN sites chosen to optimize
the probability for detecting the change that is sought,
and to serve related needs of effects researchers. Specific
sites are (and will be) emphasized, where operations of
different observing arrays can be collocated. Such Collocated
Operational Research Establishments ("CORE sites") will
serve two additional distinct purposes: (a) to provide
linkages among network programs operating to address different
needs with different protocols and (b) to provide the detailed
measurements necessary to understand important processes.
A strong linkage with the emerging National Environmental
Monitoring Framework has been forged.
The specific goals of the AIRMoN rapid detection monitoring
program are
- to provide regular, timely reports on the atmospheric
environment consequences of emission reductions, as imposed
under the Clean Air Act Amendments,
- to extend these observations to wet and dry deposition
rates that affect sensitive ecosystems, and
- to provide a direct linkage between the monitoring
and modeling communities that are involved.
The overall design target for AIRMoN is to detect, with
95% confidence, the atmospheric concentration and deposition
consequences of a 5% reduction in emissions, over a two-year
period. To meet this goal, AIRMoN would need to grow to
an array with 20 to 30 measurement sites in total, in three
subnetworks. The wet deposition component
(AIRMoN-wet) already exists
in preliminary form, with an existing 7 sites; eventually,
it is planned to contain about 20 sites. The dry deposition
component
(AIRMoN-dry) is planned
to be of similar size, although with as many as possible
of its sites collocated with
AIRMoN-wet. There are presently
13 such sites. A third sub-network would contribute, focusing
on air concentrations alone.
AIRMoN is intended to provide data needed by several alternative
methodologies for providing the rapid detection characteristics
that are sought. These techniques are described in detail
in the following summary; a combination of cluster analysis
and prediction differencing methods will probably be used.
AIRMoN has been endorsed, in principle, by both the
National Acid
Precipitation Assessment Program and NOAA.
To get started on the endeavor, the daily-sampling precipitation
chemistry research program, previously operated under
the auspices of the Department of
Energy was transferred to NOAA (the MAP3S program). Plans for
AIRMoN were endorsed during 1992 by NOAA and by the
Department of Commerce, and
were accepted by OMB as
an important contribution to NAPAP and to the debate
about the consequences of the Clean Air Act Amendments
controls. The activity was subsumed into a funding package
now well recognized NOAA's "Health of the Atmosphere" initiative,
and is widely viewed as a central piece in NOAA's "environmental
stewardship" portfolio.
Field sampling has continued without interruption since
the adoption of the program by NOAA, at each of the
AIRMoN-wet daily sampling sites. AIRMoN-wet is now recognized as a formal
subset of NADP.
AIRMoN-wet operates with a daily sample collection protocol, thus differentiating
itself from the weekly operations of the mainstream NADP
stations. In practice, daily sampling provides a greatly
improved quantification of ammonium deposition; this is
becoming an important consideration as the role of atmospheric
nitrogen in coastal eutrophication grows in importance.
The daily sampling protocol also permits a direct coupling
with meteorological factors, such as is necessary in the
early
detection part of this program.
At the
National Atmospheric
Deposition Program Technical Committee Meeting in
1994 (October 24-27) final decisions were made regarding
the AIRMoN-wet quality assurance plan; a system of flags
will be used to alert data users to specific problems. The
basic philosophy remained unaffected
by these negotiations with other networks: report all
of the data as fast as possible, give them to anyone
who wants them in an electronic format, and attach a
simple screening code to allow the user to avoid relevant
contamination problems.
Interest, both national and international, continues in
the NOAA Inferential Method, initially developed
under NAPAP
auspices for estimating dry deposition fluxes from simple field
measurements. Several foreign networks are contemplating
adopting the AIRMoN approach, specifically South Africa,
Spain, and a number of central and eastern European countries.
Improved estimates of dry deposition rates for AIRMON-dry sites are generated
regularly, and are applied to upgrade all previous estimates
derived for every location. In this regard, AIRMoN-dry
differs greatly from conventional monitoring activities.
Its results are not presented as "best estimates" that
remain in place. Rather, the results are given as best
estimates using available information, to be updated when
understanding improves.
Dry deposition algorithms for gaseous pollutants are explored
in intensive field programs, conducted regularly by teams
at Oak Ridge and
at Research Triangle
Park. Prime attention is given to O3, SO2,
and HNO3.
The National Monitoring Framework
ARL has been a partner in the process
by which the nation's environmental monitoring programs
are currently being reviewed and restructured. The intent
is to structure a multi-disciplinary "core" array of coupled
air, water, and terrestrial biospheric monitoring activities
at shared measurement locations ("Index sites") where trans-media
studies can be conducted and where research-grade methodologies
can be brought to bear on new issues. A pilot program in
the mid-Atlantic region is now about to commence.
A North American Agreement
on Environmental Cooperation (NAAEC) has been set up under
the auspices of the North American Free Trade Agreement (NAFTA).
The Commission on Environmental Cooperation (CEC) is the
organization that is negotiating multi-national programs
for consideration by the NAAEC. ARL is a leading player in
the CEC process, serving as US lead in discussions of continental-scale
integration of monitoring and modeling activities and of
the pathways by which pollutants are transported from source
regions across the entire continent. An early success of
this activity has been the acceptance by each country involved
(Mexico, Canada, and the United States) of an agreement calling
for collocation of sampling systems used in surface-level
monitoring networks in all countries. The routine intercomparison
program that is envisioned is designed to permit integration
of data sets derived using the individual national arrays,
to generate a coherent picture of the continental atmospheric
environment.
ARL has served as a participant in the International
Air Quality Advisory Board of the US-Canada International
Joint Commission for many years. The IAQAB is a part of
the IJC structure that concentrates on air quality issues
in (or affecting) the transboundary region, stretching
some several hundreds of kilometers on both sides of the
boundary.
ARL also takes part in the activities of the US-Canada
Air Quality Accords, led by the Department of State and
initially focused on questions related to acid deposition.
In recent times, the Accord process has been used to start
addressing a number of additional issues, such as toxic
chemical transport and regional ozone.
Through its role in these international processes, ARL
serves as one of very few US organizations in a position
to coordinate among them. This role has proved an important
contributor to moving the processes ahead, towards a future
in which continental scale problems are addressed with
attention that focuses on the most relevant causative factors,
which may differ from region to region.
The Council for the Environment
and Natural Resources has directed a new wave of attention
at the problem of integrated monitoring. The essence of integrated
monitoring is to conduct multi-disciplinary monitoring in
all of the relevant environmental media, at locations ("Index
Sites") where coupled research can help explain what causes
any changes that are observed. The ARL AIRMoN and ISIS programs
are examples of atmospheric integrated monitoring programs
AIRMoN addresses atmospheric deposition and ISIS concentrates
on the surface radiation and heat budget.
ARL participated in the intensive CENR process that generated
a "Framework" document describing a vision of the next
generation of environmental monitoring in the United States.
Building on the concepts of this report, the agencies involved
have decided to conduct a pilot program, in the mid-Atlantic
region. ARL is taking part in the deliberations that are
now designing the mid-Atlantic pilot study. It is intended
to ensure that both AIRMoN and ISIS are intimately coupled
with the pilot program, once it gets going.
GASIE was a blind comparison
of seven analytical techniques, at SO2 concentrations ranging
from 0-500 pptv, and was conducted at the University of Delaware,
Lewes, in September-October, 1994. Briefly, test mixtures
were delivered to the seven GASIE investigators through a
common Teflon manifold for fixed, 90-minute sampling intervals,
during which time [SO2] remained constant. Almost half of
the controlled were characterized by [SO2] less than 50 pptv.
GASIE consisted of a total of 115 ninety-minute measurement
periods, divided into four phases.
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