Project Proposal for 1999
Project title: Chronology and Isotope Geochemistry of Ground Waters in the Florida Keys and Offshore Areas
Geographic area: Florida Bay, Florida Keys, and Coral Reefs
Project start date: 1996
Project end date: 1999?
Project chief: J.K. Bohlke (co-PIís-WRD: L.N. Plummer, T.B. Coplen,
E. Busenberg; co-PI-GD: E.A. Shinn)
Mail address: 431 National Center, Reston, VA 20192
Program(s) (list all programs to which this work plan is being
Integrated Natural Resources Science Program
Program element(s)/task(s) (show percent distribution if more
than one element/task). If submitting to more than one program, include
element(s)/tasks from each program here:
Element 7: Florida Bay, Florida Keys, and the Coral Reefs
Task 7.2: Hydrogeology of Florida Bay and Florida Keys
Project summary: A brief (<100 words) summary written to
be understood by a nonspecialist. State the issues to be addressed, the
objectives of the project, significance to scientific questions and land-management
and policy issues, and benefit to the Nation, all in terms that do not
require technical translation. This paragraph will be used to describe
this project in the Program and Division science plans.
Ground waters are potential sources, sinks, and
carriers of nutrients and other contaminants beneath the Florida Keys and
offshore regions to the north and south. This project is designed to provide
new data on the sources, flow directions, exchange rates, and chemical
characteristics of ground waters underlying the region of Florida Bay,
the Keys, and offshore reefs. The results, to be derived in part from analyses
of environmental tracers and isotopes, will provide general empirical information
about subsurface transport processes and their potential impact on surface
Project objectives and strategy: More detailed/technical than
the project summary, describing BRIEFLY the technical goals and approaches
to be used over the LIFETIME of the project.
We propose to test the use of environmental isotopes
and tracers, combined with geochemical modeling, for determining the origins
and ages of the various ground waters in the region of Florida Bay and
the Keys, the extent and velocity of contaminant plumes, the fate of anthropogenic
contaminants, and water-aquifer reactions that alter the source characteristics.
The empirical approaches being tested include: (1) analyses of CFCís, carbon-14,
and tritium and helium isotopes for information about the residence times
of water and dissolved species in the subsurface; (2) analyses of stable
isotopes of carbon, sulfur, hydrogen, oxygen, and nitrogen for information
about sources of, and chemical reactions among, waters, nutrients, and
other species; and (3) modeling of chemical reactions and residence time
distributions. This work will complement other ongoing or proposed studies
in the Keys involving deliberate tracer injection, hydraulic monitoring
and modeling, and analyses of additional specific contaminants.
The major elements of the data gathering part of
the study are (1) well installation and selection, to provide regional
coverage of various ground-water environments along with depth resolution
at selected sites (many of these were done before the study, additional
ones have been installed on the basis of the earlier rounds of sampling);
(2) two intensive field sampling campaigns in which all of the constituents
of interest are collected from a subset of the sites (one of these sampling
episodes occurred in Winter 1996; the other was in Fall, 1997); (3) laboratory
analyses of sample sets (some of these are done in-house; others are contracted
out; overall time required for each set can be as much as a year). Modeling
and interpretation of results take place in preliminary fashion as data
become available, but comprehensive and reliable treatments rely upon multicomponent
evaluations involving the whole data set. In particular, the treatment
of chronological tracers will be done simultaneously in such a way that
various combinations of flow, mixing, and degradation models can be compared.
Inverse geochemical modeling will be done to determine reactions responsible
for producing observed water quality characteristics (including nutrient
concentrations) in the subsurface.
Potential impacts and major products: Describe expected outcomes,
both scientific and management/policy-related. What scientific questions
and land-management and policy issues does this project help answer? Why
is it important to Program priorities? What products will you produce to
contribute to the desired outcomes?
This project will provide quantitative information
about the origins, residence times, and nutrient chemistry of marine ground
waters beneath the Florida Keys and nearby offshore areas. Chronologic
and isotopic data for ground waters should be useful in assessing the extent
and rate of movement of potential contamination in the subsurface; nutrient
chemistry and isotopic data should be useful in distinguishing natural
and anthropogenic sources of chemical constituents in ground water. These
data and interpretations should aid decision-making about waste-water treatment
and disposal in the region. In addition, the study includes testing some
new combinations of methods and sample types that could expand the list
of approaches available to the scientific community for future investigations
of similar problems.
Collaborators, clients (Names, affiliation, and roles of internal
and external users of information generated by project):
The study is designed as a collaboration between
researchers in the Water Resources Division and the Geologic Division in
USGS. The study complements (and is coordinated with) several other studies
in the same area. Those include: INRSP Tasks 1.7, 7.2, and 7.3, which deal
with various aspects of hydrology, ground-water/surface-water interactions,
and sediment diagenesis in Florida Bay and the Keys; EPA-funded radon tracer
study; EPA-funded coral and hardbottom monitoring project; EPA-funded seagrass
monitoring project; USGS aerial magnetic ground-water salinity mapping
project; and other USGS and S. Florida Water Management projects being
conducted in Florida Bay. Information about the movement and quality of
ground water beneath Florida Bay, the Keys, and offshore reefs will be
helpful in the design of efficient regulation policies for waste-water
disposal by the Florida Dept. of Environmental Protection, the NOAA Florida
Keys National Marine Sanctuary, and Everglades National Park.
Time line (FY 1999 to project end): List MAJOR tasks and deliverables
by fiscal year and indicate key staff responsible for each.
In FY99 (end year?), analyses and data summaries
of samples collected in FY96-FY98 will be completed (all Reston PIís).
A small number of additional samples will be collected and analyzed for
a subset of chemical and isotopic constituents, to fill specific gaps in
the sets collected so far, and to provide some indication about short-term
changes at selected sites over the course of the study (collections with
aid from Shinn and Reich; analyses by the Reston PIís). Results will be
compiled and evaluated in terms of ground water sources, residence times,
and geochemical reactions (all Reston PIís). Reports will be written on
(1) origins and residence times of marine ground waters, and (2) nutrient
chemistry of marine ground waters (Reston PIís plus Shinn).
FY 1999 activities: Statement of the work to be undertaken in
FY 1999 and a description of the methods and procedures.
Analyses of samples collected in FY96-FY98 will
be compiled and evaluated. Simple mixing, dispersion, and 1-dimensional
flow models will be used to interpret the chronological data and determine
ground-water residence times; solutions will be sought that can account
simultaneously for as many tracers as possible, and discrepancies will
be evaluated with respect to possible degradation, contamination, or other
more complex behavior. Chemical data will be evaluated with geochemical
equilibrium speciation models and inverse geochemical reaction models to
investigate natural processes affecting water quality and nutrient concentrations.
A few new samples will be collected and analyzed for nutrients, chemistry,
and stable isotopes (H, 0, and N) to characterize specific endmembers identified
as minor mixing components in the marine ground water survey, including
fresh ground waters from beneath recharge areas on Key Largo, water-supply
samples, and waste-water samples from a selection of local treatment plants.
FY 1999 deliverables/products: Describe in more detail the specific
deliverables/products that will result from this work in FY 1999.
A comprehensive data report will be compiled with
all of the analytical data, methods of analysis, etc. Topical reports will
be prepared focusing on: (1) the origins and residence times of the marine
ground waters; and (2) nutrient sources and isotopic characteristics.
FY 1999 outreach: Emphasizing FY 1999, describe plans to address
client requirements, decisions, and deadlines.
New directions or major changes for FY 1999 (if applicable):
ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH
FY 1998 accomplishments and outcomes, including outreach:
The major accomplishments so far for FY98 were an
intensive sampling effort in November, 1997 and subsequent analytical work
on the samples. Approximately 1200 samples were collected from about 40
sites, mainly in Florida Bay, and including a few representatives of surface
waters, water supplies, and nested piezometers. This sample set complements
the one obtained in FY96 by extending the coverage of the project throughout
Florida Bay, by including more vertical resolution at selected sites, and
by including some shallow ground waters and seepage meters at one of the
ocean-side experimental tracer sites. Analyses and some preliminary evaluations
should be completed by about the end of FY98.
FY 1998 deliverables, products completed:
Collection and analysis of samples comprising a
comprehensive regional survey of marine ground waters beneath the Florida
Keys, in offshore transects to the reefs, and throughout the Bay, will
have been completed by the end of FY98. Data reports and interpretive reports
have been started, but will not be completed until sometime in FY99.
PROJECT SUPPORT REQUIREMENTS
Names and expertise (e.g. carbonate petrology) of key project
staff (list by fiscal year for duration of project):
J.K. Bohlke (hydrologist, geochemist) FY99 to end
L.N. Plummer (hydrologist, geochemist) FY99 to end
E. Busenberg (inorganic and trace gas chemist) FY99 to end
T.B. Coplen (isotope chemist) FY99 to end
E. Shinn (geologist) FY99 to end
J.E. Hannon (stable isotope analysis) FY99
C. Reich (geologist) FY99
Other required expertise for which no individual has been identified
(list by fiscal year for duration of project):
(Assistant for isotope analysis, data compilation and geochemical
modeling in Reston) FY99 to end
Major equipment/facility needs (list by fiscal year for duration
(Assistant for limited sampling in Florida) FY99
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