Search USGS⌕ Search

Geology topics

Brian Katz

Publications and source records attributed to Brian Katz.

6 recordsLinked to original sources
USGS2011

Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2 cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 13 C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that δD values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that δD values in ethane might be more suitable for modeling than comparable values in methane and propane.

Geochimica et Cosmochimica Acta↗
USGS2011

Constraints on Lake Agassiz discharge through the late-glacial Champlain Sea (St. Lawrence Lowlands, Canada) using salinity proxies and an estuarine circulation model

During the last deglaciation, abrupt freshwater discharge events from proglacial lakes in North America, such as glacial Lake Agassiz, are believed to have drained into the North Atlantic Ocean, causing large shifts in climate by weakening the formation of North Atlantic Deep Water and decreasing ocean heat transport to high northern latitudes. These discharges were caused by changes in lake drainage outlets, but the duration, magnitude and routing of discharge events, factors which govern the climatic response to freshwater forcing, are poorly known. Abrupt discharges, called floods, are typically assumed to last months to a year, whereas more gradual discharges, called routing events, occur over centuries. Here we use estuarine modeling to evaluate freshwater discharge from Lake Agassiz and other North American proglacial lakes into the North Atlantic Ocean through the St. Lawrence estuary around 11.5 ka BP, the onset of the Preboreal oscillation (PBO). Faunal and isotopic proxy data from the Champlain Sea, a semi-isolated, marine-brackish water body that occupied the St. Lawrence and Champlain Valleys from 13 to 9 ka, indicate salinity fell about 7-8 (range of 4-11) around 11.5 ka. Model results suggest that minimum (1600 km3) and maximum (9500 km3) estimates of plausible flood volumes determined from Lake Agassiz paleoshorelines would produce the proxy-reconstructed salinity decrease if the floods lasted <1 day to 5 months and 1 month to 2 years, respectively. In addition, Champlain Sea salinity responds very quickly to the initiation (within days) and cessation (within weeks) of flooding events. These results support the hypothesis that a glacial lake flood, rather than a sustained routing event, discharged through the St. Lawrence Estuary during the PBO. ?? 2011 Elsevier Ltd.

Quaternary Science Reviews↗
USGS2009

Characterization and disinfection by-product formation potential of natural organic matter in surface and ground waters from Northern Florida

Streamwaters in northern Florida have large concentrations of natural organic matter (NOM), and commonly flow directly into the ground water system through karst features, such as sinkholes. In this study NOM from northern Florida stream and ground waters was fractionated, the fractions characterized by infrared (IR) and nuclear magnetic resonance (NMR), and then chlorinated to investigate their disinfection by-product (DBP) formation potential (FP). As the NOM character changed (as quantified by changes in NOM distribution in various fractions, such as hydrophilic acids or hydrophobic neutrals) due to migration through the aquifer, the total organic halide (TOX)-FP and trihalomethane (THM)-FP yield of each of these fractions varied also. In surface waters, the greatest DBP yields were produced by the colloid fraction. In ground waters, DBP yield of the hydrophobic acid fraction (the greatest in terms of mass) decreased during infiltration.

Florida↗
USGS2005

Using multiple chemical indicators to assess sources of nitrate and age of groundwater in a karstic spring basin

Human health and ecological concerns have arisen due to a steady increase in nitrate-N concentrations during the past 40 years in Fannin Springs (0.3-4.7 mg/L), a regional discharge point with an average flow of >2.8 m3/second (>100 ft3/second) for water from the karstic Upper Floridan aquifer (UFA). Multiple chemical indicators (major dissolved species, 15N and 18O of nitrate, dissolved gases, 78 pesticides and degradates, and 67 organic compounds typically found in domestic and industrial wastewater) and transient tracers (3H/3He, chlorofluorocarbons [CFCs], sulfur hexafluoride [SF6]) were analyzed in water samples from nine wells along three transects and in spring water to assess groundwater age and potential contaminant sources. Land use is predominantly agricultural (52 percent) and forest (31 percent) in the 320 km2 (124 mi2) spring basin, which was delineated from a potentiometric-surface map of the UFA using high-resolution water-level data. Nitrate-N concentrations were highly variable in the oxic UFA and ranged from <0.02 to 4.7 mg/L. ?? 15N-NO3 values (3.4-9.9 per mil) indicated that nitrate contamination originated from inorganic sources (synthetic fertilizer) and organic sources (manure spreading or waste disposal). Higher nitrate concentrations and the younger age of spring water relative to water from upgradient wells indicate better communication with N sources at the surface. Apparent ages of groundwater correlated positively with well depth (P < 0.05) and were younger in water from wells nearer to the spring (<8 years) compared with other wells (10-50 years). Most transient tracer concentrations were consistent with binary mixing curves representing mixtures of water recharged during the past 10 years and older water (recharged before 1940). Young water mixing fractions ranged from 0.07 to 0.90. Trace levels of herbicides found in groundwater and spring water were indicative of applications for vegetative control in agricultural and other land-use types.

Environmental & Engineering Geoscience↗
USGS2004

Suwannee river basin and estuary integrated science workshop: September 22-24, 2004 Cedar Key, Florida

In response to the growing number of environmental concerns in the mostly pristine Suwannee River Basin and the Suwannee River Estuary system, the States of Florida and Georgia, the Federal government, and other local organizations have identified the Suwannee River as an ecosystem in need of protection because of its unique biota and important water resources. Organizations with vested interests in the region formed a coalition, the Suwannee Basin Interagency Alliance (SBIA), whose goals are to promote coordination in the identification, management, and scientific knowledge of the natural resources in the basin and estuary. To date, an integrated assessment of the physical, biological, and water resources has not been completed. A holistic, multi-disciplinary approach is being pursued to address the research needs in the basin and estuary and to provide supportive data for meeting management objectives of the entire ecosystem. The USGS is well situated to focus on the larger concerns of the basin and estuary by addressing specific research questions linking water supply and quality to ecosystem function and health across county and state boundaries. A strategic plan is being prepared in cooperation with Federal, State, and local agencies to identify and implement studies to address the most compelling research issues and management questions, and to conduct fundamental environmental monitoring studies. The USGS, Suwannee River Water Management District and the Florida Marine Research Institute are co-sponsoring this scientific workshop on the Suwannee River Basin and Estuary to: Discuss current and past research findings, Identify information gaps and research priorities, and Develop an action plan for coordinated and relevant research activities in the future. This workshop builds on the highly successful basin-wide conference sponsored by the Suwannee Basin Interagency Alliance that was held three years ago in Live Oak, Florida. This years workshop will focus on identifying information needs and priorities and developing partnerships. The USGS is seeking to define the role of the USGS Florida Integrated Science Center (FISC) in conducting integrated research in the Suwannee River Basin, and to establish a cooperative program with other agencies. Participants interested in river, floodplain, springs, estuary, or basin-wide issues are encouraged to attend. Topics for this years workshop include: Water quality and geochemistry: nutrient enrichment, reduction of nutrient loading to ground water, contaminants, and land use, Hydrogeology: interactions among ground water, surface water and ecosystem, modeling, and baseline mapping, Ecosystem dynamics: structure, process, species, and habitats (estuarine, riverine, floodplain, and wetland), and Information management: data sharing, database development, geographic information system (GIS), and basin-wide models.

Open-File Report↗