Title| Summary|Strategy|Impacts/Products|Collaborators/Clients|Task 1|Task 2 |Task 3|Task 4|Task 5|Task 6|Task 7

GEOLOGIC DIVISION CONTINUING PROJECT WORK PLAN - FL 2001

Task: 3
Task Leader: Swarzenski, Peter W.
600 4th Street South
St. Petersburg, FL 33701
Phone: (727)803-8747
Fax: (727)803-2030

Task Leader: Horowitz, Arthur R.
3039 Amwiler Road
Atlanta, GA 30360-2824
Phone: (770)903-9100
Fax: (770)903-9199

Title: Sampling procedures/approach - Integrating our work with existing programs

Coastal and Marine Geology Programs

Trace constituents are useful to assess the degree of contamination, even in a river as large as the Mississippi River. Bob Meade's Mississippi River project and other studies have shown that almost all (>92%) of the trace element load in the Mississippi River is transported downstream in particulate form, either as suspended sediment or bed-load as a carrier of contaminants. Consequently, a successful sampling program must adequately address the role of particles. This approach necessitates some unusual techniques, in that suspended sediments must be isolated or de-watered and then entirely leached. Art Horowitz (USGS-WRD) has perfected this procedure, and the same methods will be utilized for this phase of the project. In addition to these sediment samples, dissolved samples will also be analyzed for the suite of NASQAN constituents.

Work to be undertaken during the proposal year and a description of the methods and procedures:

Standard NASQAN protocol is designed to determine total as opposed to total-recoverable suspended sediment-associated trace element concentrations by the direct analyses of aliquots of material dewatered from large-volume depth- and width-integrated isokinetically collected whole-water samples. Estimates of site-specific suspended sediment fluxes are determined by summing daily instantaneous fluxes that were calculated based on log-log regression (rating curve) predictions of concentration developed by using a combination of historical and current discharge and suspended sediment concentration data. The errors associated with this approach were determined by comparing the sum of instantaneous daily fluxes calculated from actual sample-derived suspended sediment concentrations with those calculated from model-derived suspended sediment concentrations. Typically, the errors using this approach are much less than ±10% for the 3-year reporting period; however, for shorter periods of temporal resolution, the errors can increase substantially.

Site-specific intra- and interannual variations in suspended sediment associated-trace element concentrations tended to be much smaller (usually less than a factor of two) than those for discharge or suspended sediment concentrations (typically more than an order of magnitude). As there were no strong interrelations between discharge or suspended sediment concentrations, and suspended sediment-associated trace element chemistry, the use of NASQAN*-derived mean/median concentrations provided one of the only means of calculating annual sediment-associated trace element fluxes. As with the suspended sediment fluxes, the errors associated with this approach were determined by comparing the sum of site-specific instantaneous daily fluxes calculated from actual sample suspended sediment-associated trace element concentrations with those calculated using site-specific mean/median suspended sediment-associated concentrations.

The concentrations, and hence the annual fluxes, for suspended sediment-associated P and organic carbon, determined from the direct analyses of dewatered suspended sediment samples were markedly higher (fluxes were larger by factors ranging from 1.5- to 10-fold) than those determined using the more traditional/regulatory paired whole-water/filtered-water approach; this could be important for such issues as eutrophication, algal blooms, coastal productivity and incidents of Gulf Hypoxia. The majority of Cu, Zn, Cr, Ni, Ba, P, As, Fe, Mn, and Al are transported in association with suspended sediment; in contrast, Sr fluxes seem to be dominated by the dissolved fraction, whereas the transport of Li and TOC appear to be divided about equally between both phases. Annual suspended sediment fluxes in the Mississippi River Basin seem somewhat low relative to previously published averages, but are well within the range of natural variability. Downstream sediment-associated trace element, P, and TOC fluxes increase in the Mississippi River; the increases are markedly greater in the upper part of the basin (20-fold) than in the middle and lower parts of the basin (1.5-fold).

Planned Outreach:

The inorganic component of this project links directly to existing an NASQAN program on the Mississippi River. Such collaboration will consequently maximize the effectiveness of both projects. Methods developed here will also tie directly into other USGS CMPG projects that collectively address estuaries.

Publications delivered/completed for this Task:

Publications planned for this task, to be submitted for publication in current or future fiscal years.

• Swarzenski et al., 2002, A historical reconstruction of down-core metal distributions in the deltaic sediments of the Mississippi and Atchafalaya Rivers
• Swarzenski et al., 2002, Conservative/non-conservative behavior of metals in large river plumes.

Geographic area of task:

United States, Gulf Coastal States, LA

Accomplishments

Current year nonpublication accomplishments and outcomes:
Swarzenski was a co-organizer of a recent USGS Coastal Contaminants Workshop, and standard methods for inorganic geochemistry are being identified and adhered to.

Highlights - summary of the most significant outcome:
We are currently in the process of running metals/radionuclide analyses. A low-discharge cruise has been scheduled for the Sept. 4-10, 2001.

New Directions or Major Changes for Proposal Year:
A new partnership with USF Analytical Services may become a reliable and cost-effective additional source for inorganic analyses. The addition of John Bratton will provide expertise in paleo-redox reconstructions.

Title|Summary|Strategy|Impacts/Products|Collaborators/Clients|Task 1|Task 2 |Task 3|Task 4|Task 5|Task 6|Task 7