Geochemistry Commons^™

Researching Nitrite Oxidation At High Temperatures, Dolores A. Huang, Jeremy A. Dodsworth, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

15N-nitrate (NO3 -) pool dilution experiments show that ammonia (NH3) is oxidized to nitrate in geothermal springs up to at least 85C; however, nitrite (NO2 -)- oxidizing microorganisms are only known to grow up to 66°C. We hypothesize that thermophilic microorganisms oxidize nitrite to nitrate at high temperatures. Alternatively, it is possible that nitrite is oxidized abiotically. We propose to test these hypotheses by setting up microbial enrichments designed to grow thermophilic nitrite oxidizing bacteria by varying incubation temperature (50, 65, 80°C), oxygen concentration (20% and 5%), and cultivation media. A negative control consisting of filtered spring water (0.1 μm) …

Anthropogenic Osmium In Rain And Snow Reveals Global-Scale Atmospheric Contamination, Cynthia Chen, Peter N. Sedwick, Mukul Sharma

Dartmouth Scholarship

Osmium is one of the rarer elements in seawater, with typical concentration of approximately 10 x 10(-15) g g(-1) (5.3 x 10(-14) mol kg(-1)). The osmium isotope composition ((187)Os/(188)Os ratio) of deep oceans is 1.05, reflecting a balance between inputs from continental crust (approximately 1.3) and mantle/cosmic dust (approximately 0.13). Here, we show that the (187)Os/(188)Os ratios measured in rain and snow collected around the world range from 0.16 to 0.48, much lower than expected (>1), but similar to the isotope composition of ores (approximately 0.2) that are processed to extract platinum and other metals to be used primarily …

Biogenic Tracers Through The Holocene On The Alaskan Shelf, Carie A. Curry

OES Theses and Dissertations

Dramatic environmental changes in the Arctic Ocean have been observed for the last two decades including changing the amount of sea ice thickness and extent, and increased river discharge. In order to put these and other current day observations into historical context and perhaps reveal mechanisms controlling them, a suite of paleo-proxies were used to analyze two high resolution cores collected on the 2005 HOTRAX expedition. The goals of this research were: (1) develop an analytical method for determining biogenic calcite, (2) identify the major sources of biogenic matter into the system over the Holocene, and (3) assemble the history …

Export Of Terrestrial Dissolved Organic Matter Along A River To Ocean Transect Of The Lower Chesapeake Bay Investigated By Advanced Analytical Techniques, Rachel Leigh Sleighter

Chemistry & Biochemistry Theses & Dissertations

Ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) has proved essential for the complete separation of the thousands of peaks present in natural organic matter (NOM), a complex assemblage of organic molecules present in water, soils, and sediments. An improved understanding of its composition is crucial to understand how pollutants interact with NOM and how NOM cycles through global carbon cycles.

Optimizing the acquisition and handling of the FTICR mass spectra is the first step to obtaining high quality data. A simple method to internally calibrate the peaks in the complex spectra, using naturally present fatty …

Origin And Paleoclimatic Significance Of Late Quaternary Loess In Nebraska: Evidence From Stratigraphy, Chronology, Sedimentology, And Geochemistry, Daniel R. Muhs, E. Arthur Bettis Iii, John N. Aleinikoff, John P. Mcgeehin, Jossh Beann, Gary Skipp, Brian D. Marshall, Helen M. Roberts, William C. Johnson, Rachel Benton

United States Geological Survey: Staff Publications

Loess is one of the most extensive surficial geologic deposits in mid-continental North America, particularly in the central Great Plains region of Nebraska. Last-glacial-age loess (Peoria Loess) reaches its greatest known thickness in the world in this area. New stratigraphic, geochronologic, mineralogic, and geochemical data yield information about the age and provenance of Peoria Loess, as well as evaluation of recent climate models.

Comparison Of Total Mercury And Methylmercury Cycling At Five Sites Using The Small Watershed Approach, James B. Shanley, M. Alisa Mast, Donald H. Campbell, George R. Aiken, David P. Krabbenhoft, Randall J. Hunt, John F. Walker, Paul F. Schuster, Ann Chalmers, Brent T. Aulenbach, Norman E. Peters, Mark Marvin-Dipasquale, David W. Clow, Martin M. Shafer

United States Geological Survey: Staff Publications

The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1 ng L^-1 and MeHg was less than 0.2 ng L^-1. THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with …

Arctic Perennial Ice Cover Over The Last 14 Million Years, Dennis A. Darby

OES Faculty Publications

Knowledge of the long-term history of the perennial ice is an important issue that has eluded study because the Cenozoic core material needed has been unavailable until the recent Arctic Coring Expedition (ACEX). Detrital Fe oxide mineral grains analyzed by microprobe from the last 14 Ma (164 m) of the ACEX composite core on the Lomonosov Ridge were matched to circum-Arctic sources with the same mineral and 12-element composition. These precise source determinations and estimates of drift rates were used to determine that these sand grains could not be rafted to the ACEX core site in less than a year. …

Interdecadal-Decadal Climate Variability From Multi-Coral Oxygen Isotope Records In The South Pacific Convergence Zone Region Since 1650ad, Peipei Zhang

Geology Theses and Dissertations

Annual average oxygen isotope (δ18O) time series from five coral cores collected from Fiji and Tonga are used to construct a Fiji-Tonga Interdecadal-Decadal Pacific Oscillation (F-TIDPO) index of low frequency (>9yr and <55yr) climate variability in this area back to 1650 A.D. Presently, both Fiji and Tonga are located in the South Pacific Convergence Zone (SPCZ) salinity front region where the Interdecadal Pacific Oscillation (IPO) variation is most pronounced. We first demonstrate the consistency between this F-T IDPO index and a MSL pressure-based SPCZ Position Index (SPI) (1891-2000), thus verifying the ability of coral δ18O to record past interdecadal-decadal climatic variations in this region back to 1891. The F-T IDPO index is then shown to be synchronous with the IPO index (1856-2000), suggesting that this coral-based index effectively represents the interdecadal-decadal scale climate variance back to 1650. The consistently anti-phase spectrums of the F-T five-coral composite and the interdecadal-decadal components in equatorial Pacific coral δ18O series from Maiana [Urban et al., 2000] and Palmyra [Cobb et al., 2001] suggest that the simultaneous eastern expansion (western contraction) of the eastern salinity front of Western Pacific Warm Pool (WPWP) occurs at the same time as the northeast (southwest) movement of the SPCZ during a positive IPO (negative IPO) phase.

Impact Of Anthropogenic Combustion Emissions On The Fractional Solubility Of Aeroosol Iron: Evidence From The Sargasso Sea, Peter N. Sedwick, Edward R. Sholkovitz, Thomas M. Church

OES Faculty Publications

We report empirical estimates of the fractional solubility of aerosol iron over the Sargasso Sea during periods characterized by high concentrations of Saharan dust (summer 2003) and by low concentrations of aerosols in North American/maritime North Atlantic air masses (spring 2004 and early summer 2004). We observed a strong inverse relationship between the operational solubility of aerosol iron (defined using a flow-through deionized-water leaching protocol) and the total concentration of aerosol iron, whereby the operational solubility of aerosol iron was elevated when total aerosol iron loadings were low. This relationship is consistent with source-dependent differences in the solubility characteristics of …

Assessing The Paleoceanographic Potential Of The Coral Montipora Venosa At Fanning Atoll, Central Equatorial Pacific, Alexa Stolorow

Geology Theses and Dissertations

As interest in global climate change increases, so does the need for better and more extensive climate proxies. The central equatorial Pacific has been established as the region with the largest ENSO-related sea surface temperature (SST) and precipitation (PPT) anomalies, which are known to impact global interannual climate variability. To date, the coral genus Porites has been most commonly utilized for coral-based paleo-reconstructions of ENSO and lower frequency phenomena. However, due to questions of biological artifacts in coral, to more fully understand coral-based reconstruction, different coral genera need to be analyzed.
In this study, oxygen (δ18O) and carbon (δ13C) isotopic …

Western Caribbean Sea Surface Temperatures During The Late Quaternary, Matthew W. Schmidt, Maryline J. Vautravers, Howard J. Spero

OES Faculty Publications

[1] Mg/Ca ratios in the planktonic foraminifera Globigerinoides ruber from Colombian Basin core ODP 999A suggest that Caribbean sea surface temperatures ( SSTs) were from 2.1 to 2.7°C colder than the present during the last three glacial maximums. In comparison, faunal derived SSTs ( SIMMAX method) show that August SSTs in the Caribbean varied < 2° over the past 360 kyr, whereas February SSTs varied between 21.0°C and 26.5°C. Changes in the Mg/Ca-SST record contain a strong 23 kyr periodicity, suggesting the Mg/Ca-SST record reflects a warm season weighted SST average rather than an annual mean SST. Combining several dissolution indices, we identify brief periods of decreased carbonate preservation in our record and show that MIS 11 stands out as the most intensive dissolution cycle in the Caribbean over the last 460 kyr. Comparison of Caribbean SST change with a similar estimate of tropical SST variability in the western Pacific over the past 360 kyr reveals shifts in the east-west tropical SST gradient that are coeval with glacial-interglacial climate change and consistent both with a southward migration of the glacial ITCZ and with a glacial El Niño-like mode of tropical circulation.

The Composition Of Coexisting Jarosite-Group Minerals And Water From The Richmond Mine, Iron Mountain, California, Heather E. Jamieson, Clare Robinson, Charles N. Alpers, D. Kirk Nordstrom, Alexei Poustovetov, Heather A. Lowers

United States Geological Survey: Staff Publications

Jarosite-group minerals accumulate in the form of stalactites and fine-grained mud on massive pyrite in the D drift of the Richmond mine, Iron Mountain, California. Water samples were collected by placing beakers under the dripping stalactites and by extracting pore water from the mud using a centrifuge. The water is rich in Fe³⁺ and SO₄^2–, with a pH of approximately 2.1, which is significantly higher than the extremely acidic waters found elsewhere in the mine. Electron-microprobe analysis and X-ray mapping indicate that the small crystals (<10 > μm in diameter) are compositionally zoned with respect to Na …

Relating Water And Otolith Chemistry In Chesapeake Bay, And Their Potential To Identify Essential Seagrass Habitats For Juveniles Of An Estuarine-Dependent Fish, Spotted Seatrout (Cynoscion Nebulosus), Emmanis Dorval

Biological Sciences Theses & Dissertations

A quantitative understanding of habitat use of estuarine-dependent fishes is critical to the conservation of their most essential habitats. Because recruitment and fitness may be influenced by the quality of juvenile habitats, developing methods to quantify habitat-specific survivorship is pivotal to such understanding. An initial step to quantify survivorship is to validate the habitat-specific natural tags contained in otoliths. To this aim I investigated the variability in the chemistry of surface waters and otoliths of juvenile spotted seatrout, Cynoscion nebulosus, in five seagrass habitats of Chesapeake Bay, namely: Potomac, Rappahannock, York, Island, and Eastern Shore. I measured Mg, Ca, …

Methods And Models For Estimating Advective Pore Water Exchange In Tidal Flats, Timothy J. Shaw

Faculty Publications

No abstract provided.

Rare-Earth Elements And Nd And Pb Isotopes As Source Indicators For Labrador Sea Clay-Size Sediments During Heinrich Event 2, Larry V. Benson, Don Barber, John T. Andrews, Howard E. Taylor, Paul Lamothe

United States Geological Survey: Staff Publications

Elemental abundances and Nd and Pb isotope ratios were determined on samples from the carbonate-free, clay-size fractions of sediments from intervals above, within, and below Heinrich event 2 (H-2) in core HU87-9 from the Northwest Labrador Sea slope. In HU87-9, rare-earth element (REE) distributions and elemental concentrations within the H-2 event are distinct from those outside this event. ɛ_Nd(0) and ²⁰⁶Pb/²⁰⁴Pb data also indicate different values for sediments deposited within and outside the H-2 event. Comparisons of REE patterns from the H-2 interval with those from bedrock units in Baffin Island, northern Quebec, and Labrador …

Organic Geochemical Analysis Of Late-Glacial And Early-Holocene Ecosystem Changes: A Case Study From Northern New England Lakes, Michael A. Kruge, Andrea Lini

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

The lacustrine sedimentary archive of organic remains provides important evidence for the reconstruction of the environmental histories of lakes and their watersheds, recording the response of the Earth's biota to changes on scales varying from the local to the global. The last Glacial-Interglacial transition presents an opportunity to investigate how, and at what rates, watershed and lake ecosystems were established on once glaciated, carbon and nutrient-poor landscapes. The small lakes of northern Vermont (USA) provide an appropriate setting in which to investigate such changes.

As part of a multidisciplinary study of three Vermont lake sediment cores, samples ranging in age …

Nitrate Anomaly In The Upper Nutricline In The Northern South China Sea - Evidence For Nitrogen Fixation, George T. F. Wong, Shi-Wei Chung, Fuh-Kwo Shiah, Chung-Chi Chen, Liang-Saw Wen, Kon-Kee Liu

OES Faculty Publications

[1] Up to 2 μM of nitrate anomaly, N*, were found in the upper nutricline at the South East Asia Time-series Study (SEATS) site in the northern South China Sea (SCS). These concentrations were among the higher values reported in the Pacific and indicate the significant contribution of the remineralization of nitrogen-rich organic matter formed by nitrogen fixation to the nutrient dynamics of the area. The concentrations were systematically higher, by up to 2.5 μM, in the Fall through the early Spring, during the northeast monsoon, than in the Summer, suggesting that the impact of nitrogen fixation was higher during …

Strontium Isotopic Signatures Of The Streams And Lakes Of Taylor Valley, Southern Victoria Land, Antarctica: Chemical Weathering In A Polar Climate, W. B. Lyons, Carmen A. Nezat, Larry V. Benson, Thomas D. Bullen, Elizabeth Y. Graham, Jesicca Kidd, Kathleen A. Welch, James M. Thomas

United States Geological Survey: Staff Publications

We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different ⁸⁷Sr/⁸⁶Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system …

Intra-Annual Variation In The Stable Oxygen And Carbon And Trace Element Composition Of Sclerosponges, P. K. Swart, S. Thorrold, B. Rosenheim, A. Eisenhauer, C. G. A. Harriason, M. Grammer, C. Latkoczy

Biological Sciences Faculty Publications

This paper presents data to support the presence of (1) intra-annual signals in the chemical composition (δ¹⁸O and Sr/Ca) of the skeletons ofsclerosponges from the Bahamas and (2) variable rates of skeletal accretion. These conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 μm and a laser microprobe which obtained trace element data every 20 μm (Sr, Mg, and Pb). An age model was established using a combination of changes in the concentration of Pb, the …

Identification Of Past Climate Variability Of The Eastern Pacific Ocean Using Both D13c And D18o Records In Corals From Clipperton Atoll (1994-1906), Lei Ren

Geology Theses and Dissertations

The ENSO (El Nino and the Southern Oscillation) is a fundamental ocean-atmosphere phenomenon that dominates interannual global climate variability. Reconstructing past ENSO events is therefore important for documenting and understanding the past behavior of the global climate system and enabling us to predict future climate change. However, the present understanding of ENSO events has been mainly based on the instrumental record of Pacific climate which provides detailed data only for the past few decades. Recent studies have shown that the stable isotope record in coral skeletons can be used as a valuable indicator of paleoclimatic changes in tropical regions, and …

A Geochemical Study Of Marine Sediments From The Mac. Robertson Shelf, East Antarctica: Initial Results And Palaeoenvironmental Implications, Peter N. Sedwick, P. T. Harris, L. G. Robertson, G. M. Mcmurtry, M. D. Cremer, P. Robinson

OES Faculty Publications

Sediments from the Antarctic continental margin may provide detailed palaeoenvironmental records for Antarctic shelf waters during the late Quaternary. Here we present results from a palaeoenvironmental study of two sediment cores recovered from the continental shelf off Mac. Robertson Land, East Antarctica. These gravity cores were collected approximately 90 km apart from locations on the inner and outer shelf. Both cores are apparently undisturbed sequences of diatom ooze mixed with fine, quartz-rich sand. Core stratigraphies have been established from radiocarbon analyses of bulk organic carbon. Down-core geochemical determinations include the lithogenic components Al and Fe, biogenic components opal and organic …

Estimation Of Groundwater Velocities From Yucca Flat To The Amargosa Desert Using Geochemistry And Environmental Isotopes, Ronald L. Hershey, Steve Y. Acheampong

Publications (WR)

Geochemical modeling techniques were applied to groundwater flowpaths from Yucca Flat on the Nevada Test Site (NTS) to the Amargosa Desert, south of the NTS to estimate groundwater flow velocities for independent comparison to velocities calculated by other methods. The groundwater flowpaths examined considered flow in the carbonate aquifer beneath Yucca and Frenchman flats mixing with flow from carbonate aquifers east and southeast of the NTS and discharging at wells south of the NTS border. The approach used the computer codes WATEQ4F and NETPATH to calculate chemical speciation, determine the saturation state of mineral phases, and simulate mixing and the …

The Implications Of Turbidite-Driven Redox Changes In Sediments Of The Iberia Abyssal Plain, Timothy J. Shaw, P. A. Meyers

Faculty Publications

No abstract provided.

Organic Matter Accumulation, Sulfate Reduction, And Methanogenesis In Pliocene–Pleistocene Turbidites On The Iberia Abyssal Plain, P. A. Meyers, Timothy J. Shaw

Faculty Publications

No abstract provided.

Identification And Quantitation Of Volatile Amines In Chesapeake Bay Sediments, Neeraja Y. Krishna

Chemistry & Biochemistry Theses & Dissertations

Sediments from different parts of the Chesapeake Bay were analyzed to determine the presence of volatile amines. A HF-HCl extraction method was used to extract both exchangeable and fixed amines from the sediments and a purge-and-trap technique was used to concentrate the amines. Following derivatization with heptafluorobutyric anhydride (HFBA), the HFBA-amines were analyzed by gas chromatography with electron capture detection and with mass spectrometric detection. One primary amine, i-amylamine with a concentration ranging from 0. 78 nmoles/g dry weight to < 0.05 nmoles/g dry weight was found in a total of twenty seven samples collected on three different dates in 1993. Another primary amine, 2-methylbutylamine with a concentration ranging from 0.18 nmoles/g dry weight to < 0.05 nmoles/g dry weight was found in a total of twenty three samples collected on three different dates in 1993. A secondary amine, diethylamine was detected but could not be quantified in a total of seven samples collected in September 1993. The concentrations of these amines varied with location in the Bay, depth in the sediment, and time of year the sediments were collected. The origin of i-amylamine and 2-methylbutylamine might be from the biological decarboxylation of amino acids leucine and isoleucine, respectively. The origin of diethylamine is unknown.

Trace Metals And Pyrite In Sediments Of Chesapeake Bay, Robert S. Kluckhohn

OES Theses and Dissertations

The formation and cycling of iron sulfides within anoxic sediments can affect the cycling of trace metals. The sediments at station CB-27 (near Annapolis, Maryland) in Chesapeake Bay were rich in FeS (39% of TS), low in greigite (3.6% of TS), and has a relatively constant pyrite concentration (50 - 60% of TS) with depth. The percent composition of total metals in pyrite were 25.7% cu, 11.8% Zn, 15.8% Fe, and non-detectable to 2.1% Cd. At Station CB- 28 (near the Choptank River), the sediments were low in FeS (1.7% of TS), richer in greigite (up to 14% of TS), …

A Comparison Of Metals In Several Ahermatypic Corals And Surficial Sediments: Mobile Pinnacles And Hoffa Reef, Northcentral Gulf Of Mexico, Kathryn M. Conko

OES Theses and Dissertations

Metal concentrations in marine sediment and carbonate secreting invertebrates are representative of surrounding environmental chemistry. Aluminum, Ba Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr, and Zn were measured in carbonate and terrigenous phases of the $<$63 um fraction of sediment samples from two locations in the northcentral Gulf of Mexico. Enrichment factors indicate that Al, Ba, Cu, Cr, Mg, Mn, and Ni are all slightly depleted in these sediments relative to crustal abundances. Discriminant function analyses shows that the concentrations of five elements differ between locations.

Ahermatypic coral (106 specimens) from five genera collected from the study sites were analyzed for Cd, Cu, Cr, Pb, Zn, Mn, Sr, Ba, Fe, Ca and Mg. Eight elements vary between some genera, Al and Ba also vary in concentration in corals between either location. All elements except Sr are significantly depleted in the coral with respect to Ca in the …

Sulfide In Shelf/Slope Waters Of The Western Atlantic, Christian F. Krahforst

OES Theses and Dissertations

Sulfide in the surface ocean has been recently considered as a source of hydrogen sulfide gas in the marine boundary layer. This "oxic" sulfide may also be important as a ligand in trace metal complexation. In the absence of actual data, the existence of sulfide in the ocean mixed layer remains speculative. The purpose of this study was to develop a sensitive technique (having picomolar detection limits) for the determination of sulfide in seawater, and to investigate the distribution of sulfide in the surface ocean.

In order to assess the abundance and distribution of sulfide in surface waters, samples were …

Leachate Monitoring In Naturally Saline Groundwater Chesapeake Landfill Chesapeake Virginia, T. Britt Mcmillan

OES Theses and Dissertations

Groundwater chemistry around the Chesapeake municipal landfill was monitored over a one year period. Ten sample sites as well as two surface water sites were used to monitor water quality. Two wells, one at 3 m and the other at 10 m were located at each site. Surface water samples were taken from the Elizabeth River, north of the landfill, and a tidal channel, west of the landfill. Seven groundwater sites were downgradient of the landfill and three sites were upgradient (control sites).

The landfill overlies a tidal marsh, approximately 100 m south of the intracoastal waterway (Elizabeth River). Dredge …

A Method For Determining Creosote Contamination Of Sediment From The Elizabeth River, Norfolk, Va, Elizabeth G. Merrill

OES Theses and Dissertations

Hydrocarbon input sources to the Elizabeth River were investigated. Carbonized coal products (creosote, coal tar, and roof tar), petroleum products (Kuwait Crude Oil, No. 2 Fuel Oil, and a fuel oil spill sample) and soot (woodstove and diesel engine) have unique hydrocarbon distributions. Elizabeth River sediment hydrocarbon distributions indicate that they are contaminated with both carbonized coal and petroleum products. Using a simple two member mixing model, greater than 65 percent of Elizabeth River sediments' resolved aromatic compounds were determined to originate from carbonized coal products. These aromatic hydrocarbons include the EPA priority pollutant polynuclear aromatic hydrocarbons which are known …