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Peter W. Swarzenski

Publications and source records attributed to Peter W. Swarzenski.

69 records · Page 4Linked to original sources
USGS2005

Gulf of Mexico integrated science - Tampa Bay study, the impact of groundwater and contaminants on Tampa Bay

Despite the recreational and economic value of coastal bays and estuaries, these ecosystems are often among our most 'troubled' natural environments. Urbanization, agriculture, mining, and shipping are just a few activities that can have a profound and lasting impact on the coastal zone. In order to maintain a healthy coastal ecosystem, it is crucial to develop reasonable management practices around expert scientific information. We still have much to learn about the quantity and quality of groundwater being discharged into Tampa Bay, Florida. We also need to improve our knowledge of a wide range of contaminants entering the bay and must be able to determine where they accumulate in seafloor sediments. Such buried contaminants can potentially be harmful to biota if they are released to the water column. U.S. Geological Survey (USGS) scientists and research partners from the University of South Florida (USF), the University of Florida (UF), and the Florida Marine Research Institute (FMRI) are mapping sources of groundwater, measuring groundwater flow into Tampa Bay, and assessing the impact of contaminants and sediments on bay water quality and ecosystem health.

Open-File Report↗
USGS2004

An autonomous, electromagnetic seepage meter to study coastal groundwater/surface-water exchange

The bi-directional exchange of groundwater with coastal surface waters may influence not only coastal-water and geochemical budgets, but may also impact and direct coastal ecosystem change. For example, the widespread discharge of nutrient-enriched submarine groundwater into an estuary or lagoon may contribute directly to the onset and duration of eutrophication, as well as the development of harmful algal/bacterial blooms. Most often, this submarine groundwater discharge (SGD) (defined here as a composite of meteoric, connate and sea water) occurs as hard-to-constrain diffuse seepage, rather than as focused discharge either through vent or collapse features. As a result, quantifying SGD rates has remained difficult for both oceanographers and hydrologists alike. This report describes an adaptation of an old tool, the Lee-type manual seepage meter, with a state-of-the-art electromagnetic flow meter that enables rapid, autonomous, bi-directional measurements of fluid exchange rates across the sediment/water interface. When such measurements are coupled and interpreted with surface and groundwater pressure, salinity and temperature data, as well as other complementary measurements such as excess watercolumn 222 Rn activities, then realistic groundwater/surface-water exchange rates can be obtained in dynamic coastal environments.

Open-File Report↗
USGS2004

Submarine ground-water discharge and its role in coastal processes and ecosystems

Submarine ground-water discharge (SGD) has recently been recognized as a phenomenon that can strongly influence coastal water and geochemical budgets and drive ecosystem change. For example, the discharge of nutrient-enriched ground water into coastal waters may contribute significantly to eutrophication and blooms of harmful algae. Similarly, the quantity of SGD can also directly affect the availability of fresh water to coastal communities, impact fragile coastal ecosystems such as estuaries and coral reefs, and influence geomorphology of shoreline features. Moore raised awareness of the global importance of SGD and much effort has been devoted to developing new tracer techniques and methods for the identification and quantification of SGD. Because the discharge of coastal ground water commonly occurs as diffuse seepage rather than focused discharge through identifiable springs, assessing SGD has remained difficult for both oceanographers and hydrologists. Through national and international research programs, Burnett, Moore, Charette, and others have developed a rigorous, systematic approach for quantifying SGD using a wide assortment of tracers and methods. Intercalibration experiments, such as those conducted in coastal waters off Australia, Brazil, and Long Island, NY, demonstrate that careful measurements can accurately quantify SGD, confirm some of the driving mechanisms (e.g. climatic and tidal forcing), and constrain the spatial and temporal scales at which these mechanisms operate. Now that approaches for rigorously quantifying SGD are becoming better established, scientists can now begin to investigate the wide variety of coastal processes affected by SGD.

Open-File Report↗
USGS2004

Assessment of estuarine water-quality indicators using MODIS medium-resolution bands: initial results from Tampa Bay, FL

Using Tampa Bay, FL as an example, we explored the potential for using MODIS medium-resolution bands (250- and 500-m data at 469-, 555-, and 645-nm) for estuarine monitoring. Field surveys during 21–22 October 2003 showed that Tampa Bay has Case-II waters, in that for the salinity range of 24–32 psu, (a) chlorophyll concentration (11 to 23 mg m −3 ), (b) colored dissolved organic matter (CDOM) absorption coefficient at 400 nm (0.9 to 2.5 m −1 ), and (c) total suspended sediment concentration (TSS: 2 to 11 mg L −1 ) often do not co-vary. CDOM is the only constituent that showed a linear, inverse relationship with surface salinity, although the slope of the relationship changed with location within the bay. The MODIS medium-resolution bands, although designed for land use, are 4–5 times more sensitive than Landsat-7/ETM+ data and are comparable to or higher than those of CZCS. Several approaches were used to derive synoptic maps of water constituents from concurrent MODIS medium-resolution data. We found that application of various atmospheric-correction algorithms yielded no significant differences, due primarily to uncertainties in the sensor radiometric calibration and other sensor artifacts. However, where each scene could be groundtruthed, simple regressions between in situ observations of constituents and at-sensor radiances provided reasonable synoptic maps. We address the need for improvements of sensor calibration/characterization, atmospheric correction, and bio-optical algorithms to make operational and quantitative use of these medium-resolution bands.

Florida↗
USGS2004

Novel geophysical and geochemical techniques used to study submarine groundwater discharge in Biscayne Bay, Florida

Introduction Submarine groundwater discharge (SGD) is a problem of major proportions on a world-wide scale. The ubiquitous nature of SGD along varied coastlines and its importance to coastal water and geochemical budgets have recently been thrust into the global spotlight . For example, the discharge of nutrient-enriched groundwater into coastal waters may cause nutrient imbalances that can lead to eutrophication or near-shore micro-organism blooms . Similarly, SGD can also directly affect threatened coastal freshwater resources and impact fragile coastal ecosystems, such as coral reefs. Recently, much effort has been devoted to developing and adapting new tracer techniques and methods for the identification and quantification of SGD. As the discharge of coastal groundwater most often occurs as diffuse seepage rather than through a single vent feature, assessing SGD has remained difficult for both oceanographers and hydrologists alike. Burnett and colleagues have developed a systematic approach to investigate SGD by using a combination of both physical seepage measurements and a suite of naturally occurring isotopic tracers in the U/Th decay chain – 222 Rn and 223,224,226,228 Ra. Manheim et al. further extended SGD investigations by adapting geophysical resistivity techniques to examine fine-scale change in conductivity fields within coastal sediments. Such streaming resistivity profiling has been successfully applied to identify sites of SGD, as well as the dynamic position of the fresh water/saltwater interface.

Florida↗
USGS2004

Is the extraction of thorium onto MnO 2 -coated filter cartridges uniform?

Large-volume (i.e., 10 2 - 10 3 L) seawater samples are traditionally required to study the partitioning of particle-reactive radionuclides between solution and size-fractionated particulate matter. One of the most frequently used methods to preconcentrate the short-lived isotopes of Th ( 234 Th and 228 Th) from such large volumes of water involves the effective extraction of Th onto two MnO 2 -coated polypropylene cartridges. Determination of dissolved Th activities assumes that the two MnO 2 -coated filter cartridges extract Th uniformly (same extraction efficiency), but this assumption has not been rigorously validated. Any variability in the extraction efficiency of the two cartridges connected in series will directly introduce an error in the determination of final dissolved Th activity. In this article, we evaluated the variability in the extraction efficiency of MnO 2 -coated filter cartridges that were prepared under varying conditions. Thorium-234-spiked seawater was filtered in series through a manifold consisting of six MnO 2 -coated cartridges. From the activities of 234 Th retained in each cartridge, the relative (calculated from the activities in two successive cartridges) and absolute (ratio of 234 Th activity retained to the activity entered) extraction efficiency for each of the cartridges was calculated. At a constant flow rate and constant KMnO 4 saturation, the absolute extraction efficiency varied by -40% (from 54.1 to 93.8%) within the first two filter cartridges, and over 50% (from 32.3 to 89.3%) on all six MnO 2 cartridges. Our results confirm that a uniform extraction efficiency using two filters connected in series is rarely achieved. Using the average extraction efficiency of all cartridges, we propose a new approach that assumes a constant extraction efficiency. This method will reduce the error introduced by the assumption of uniform extraction efficiency in the determination of dissolved Th activities.

Open-File Report↗
USGS1999

210Pb and 210Po, manganese and iron cycling across the O2/H2S interface of a permanently anoxic fjord: Framvaren, Norway

Vertical profiles of dissolved and particulate 201 Po and 210 Pb were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O 2 /H 2 S interface facilitates the aerobic dissolution of MnO 2 . In contrast, Fe(II) concentrations begin to increase only at the O 2 /H 2 S interface depth. Activity profiles reveal that dissolved 210 Po and 210 Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210 Po and 210 Pb are highly enriched at the O 2 /H 2 S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210 Po and 210 Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated.

Framveran Fjord↗