Environmental Engineering Reference
In-Depth Information
reliably predicted from either prey Hg levels or abiotic
measurements. Although efforts are underway to bet-
ter model these relationships through wildlife criterion
values based on water Hg concentrations (Nichols et al.,
1999) and other means, direct fi eld measurements are still
required to confi dently track changes in environmen-
tal Hg loads. The challenge to choose the best indicator
organism is even greater because more recent evidence
indicates substantial differences in species' sensitivities to
MeHg toxicity (Heinz et al., 2009) and uptake (Evers et al.,
2005); however, the ability to interpret short- and long-
term Hg body burdens with nonlethal sampling and to
relate those concentrations to adverse effects at taxonomi-
cally relevant levels is promising. Therefore, the value of
measuring spatiotemporal trends in Hg in wildlife is par-
ticularly strong for tracking changes as well as for species
conservation purposes and determining the health of the
overall ecosystem.
trial, and coastal ecosystems. The indicators identifi ed are
wide-ranging and involve measurements made at several
different scales of time and space but are judged to be those
that will provide the best information to policymakers and
other stakeholders on the degree to which environmen-
tal concentrations are changing with identifi cation of the
reasons for the changes occurring. The need for baseline
data is crucial for the success of the program, as changes
are already occurring in a number of sectors, and further
emission reductions are expected from power plants and
other sources. It is therefore critical that an assessment pro-
gram be implemented soon, and there is urgency for the
responsible federal and state agencies, and other interested
partners, to continue to promote the process of designing
and implementing an ecologic Hg monitoring program
through legislative action.
To adequately assess ecologic changes in Hg concentra-
tions, it will be necessary to make a long-term commit-
ment to ecologic monitoring and modeling. It could take
up to 20 years before the full scope of the impacts of
the emission reductions are determined, depending on
the types of systems being monitored, and especially for
large water bodies, for those with relatively large water-
sheds, and for the coastal environment. For this reason, it
is critical for federal agencies and others in cooperation to
make a fi rm commitment to support the monitoring effort
for many years into the future at both the regional and the
global scale. Even given the fi scal realities of government
that limit long-term planning, it is still possible for federal
agencies, states, private-sector organizations, and others
to provide long-term support for the proposed monitoring
program. A monitoring program is a substantial undertak-
ing that will require a sustained commitment and sub-
stantial resources and is likely too large and complex to be
housed in any particular federal agency or academic insti-
tution. Indeed, for the United States, as outlined in the
bills submitted to U.S. Congress, participation for a North
American network would involve many organizations
(USEPA, USGS, NOAA, US Fish and Wildlife Service, and
US Park Service) with each agency being responsible for
the monitoring that falls under their charge, and for these
agencies to coordinate and involve academic and other
institutions in the various activities. Such an approach for
the United States is based on the model used in current
monitoring programs such as the NADP, a consortium
of more than 250 sponsors that depends on substantial
funding support from at least a half-dozen different
federal agencies and departments. Similarly, the bills pro-
pose the formation of a nonfederal oversight management
committee that will provide guidance and which would be
composed of scientists from a wide range of backgrounds
and organizations. Currently, such a structure is the basic
structure being considered, with federal agencies working
with each other and with other interested organizations to
develop a broad consortium to support and guide a moni-
toring and assessment program.
Concluding Remarks
The proposed monitoring strategy embraces the need
for detailed sample collection and analysis at a rela-
tively small number of locations to document the extent
of change resulting from future proposed Hg emission
reductions. In addition, it is necessary to collect samples
on a subset of indicators (Tables 6.1 and 6.2) at a large
number of sites that are widely distributed on a conti-
nental scale and that cover a wide variety of ecosystems.
This monitoring framework will be integrated with the
application of atmospheric and watershed Hg models.
Monitoring sites should be clustered together within
ecoregions to allow for the assessment of the importance
of local environmental effects not directly related to Hg
deposition changes. At the intensive sites a broad array of
atmospheric, water, sediment, terrestrial, and biotic sam-
pling would be done, while at the cluster sites, wet Hg
deposition would be measured only in conjunction with
seasonal sediment collections for total Hg and MeHg.
Aquatic biota sampling would consist of yearling fi sh
and, on a 3- to 5-year timescale, the sampling of piscivo-
rous fi sh. Wildlife sampling would be conducted under a
similar framework with yearly nondestructive sample col-
lection combined with the 3- to 5-year sampling of larger
predators. Overall, such a framework would answer the
questions of both whether change is occurring in atmo-
spheric Hg input and how this change is refl ected in biota
MeHg concentrations across a variety of aquatic ecosys-
tems. In addition, this program would provide the infor-
mation necessary to demonstrate the impact of reductions
in Hg emissions from anthropogenic sources on fi sh and
wildlife MeHg concentration.
This chapter has identifi ed the most useful indicators for
the examination of environmental changes in Hg contami-
nation in different compartments of the environment, for
the atmosphere to wildlife that live in freshwater, terres-
