Environmental Engineering Reference
In-Depth Information
table 6.1
Proposed Indicators for Both the Intensive and the Cluster Sites within the Monitoring Program
Indicator
Location
Frequency
Indicator of
Atmospheric Hg speciation and fl ux
I
Continuous
Causality
Wet deposition Hg and Flux
C & I
Weekly & event
Causality
Throughfall and litterfall Hg speciation/fl ux
I
Weekly
Causality
Hg in snowpack
C & I
Annual
Both
Soil/sediment speciation (i.e., Hg, MeHg and %MeHg)
C & I
Annual & quarterly
Both
Soil solution speciation
I
Quarterly
Both
Forest fl oor survey
I
Every 10 yrs
Causality
Methylation/demethylation rates
I
Biannual
Both
Sediment Hg accumulation rate
C & I
Every 5-10 yrs
Both
Surface water Hg speciation/Hg
0
fl ux
C & I
Annual & quarterly
Both
Stream water and groundwater Hg speciation and fl ux
I
Weekly & quarterly
Causality
Algae/phytoplankton and zooplankton Hg speciation
I
Quarterly
Causality
Hg speciation in prey fi sh or estuarine invertebrates
C & I
Annual
Both
Total Hg in piscivorous fi sh
C & I
Annual
Trend
Total Hg in mammal/bird blood and fur/feather/egg
C & I
Annual
Both
SOURCE
: Information summarized from Harris et al. (2007) and Mason et al. (2005).
C
cluster sites; I
intensive sites.
humid temperate, and humid tropical) and 14 divisions
(Bailey, 2004), and in terms of Hg monitoring it appears that
the terrestrial regions could be subdivided into 10 “ecore-
gions.” In addition, estuarine and coastal sites should be
included in the network (Evers et al., 2008a) because these are
impacted by local and regional inputs from the atmosphere
and the watershed. The number of estuarine and marine
sites is dependent on the total number of intensive sites,
but there should be at least 2-3 to cover spatial and regional
differences and to account for sites directly impacted versus
remote locations. On the east coast of North America, for
example, it could be possible to choose an intensive site near
the coast so that the cluster sites incorporate different water
types, such as lakes, tidal river reaches, and the estuarine
and coastal environment.
It is scientifi cally reasonable to have 10-20 cluster sites
corralled around each intensive site, and these sites would be
chosen based on their similar atmospheric loading within
each ecoregion. At these sites, the primary indicators would
be measured over a prolonged period of time (Table 6.1). It
is envisioned that a set of cluster sites would have ecologic
characteristics that are as similar as possible but would have
differing site characteristics (Schmeltz et al., 2011) (e.g., pH,
dissolved organic carbon (DOC), acid neutralizing capacity
(ANC), and watershed:water body ratio). Cluster site selec-
tion criteria would be based on multiple factors, such as
water-body type (lake, reservoir, river, or estuary/coastal)
and would represent remote and impacted sites, dry regions
and saline waters, as well as a wide range of ecosystem
types, and include exposure “hotspots” (Evers et al., 2007).
Intensive sites would be locations where intensive, mul-
timedia, more continuous monitoring is conducted, and
where the specifi c objective is both the careful monitor-
ing of anticipated changes to Hg loading (trend analy-
sis) and detailed documentation of the environmental
response in terms of MeHg accumulation in biota (causal
response). Emphasis would be placed on choosing sites
where change is expected. To maximize existing moni-
toring, information, and resources, these sites should
be established in conjunction with current deposition
monitoring stations and/or ecosystem study sites. Clearly,
sites from the National Atmospheric Deposition Program
(NADP) Mercury Deposition Network (MDN), which cur-
rently measures only wet deposition, but which is being
expanded to include atmospheric Hg speciation measure-
ments (MDN, 2008), would be desirable as would be sites
from other regional monitoring programs, which include
Hg and related ancillary measurements, because of the lon-
ger-term records at these locations. Measurements would
include detailed atmospheric, watershed, aquatic, and biota
sampling. Priority should be also given to sites with other
intensive ongoing monitoring programs (including sites,
such as the Long Term Ecological Research [LTER] Network,
which may not have existing Hg data) and would seek to
