Redox Potential and Seasonal Porewater Biogeochemistry of Three Mountain Wetlands in Southeastern Kentucky, USA

Redox potentials (Eh) were monitored bimonthly and porewater chemistry was analyzed seasonally at three slightly-acidic, high-elevation Kentucky wetlands that differed in hydrology, parent materials, and vegetation. At all sites, Eh values were below 300 mV, which indicated that reducing conditions persisted within the upper 90 cm and fluctuated mainly within the range of iron and sulfate reduction. Significant relationships of Eh values with depth were observed only at the Martins Fork wetland, where precipitation was the primary water source. The strongest and most stable reducing conditions, observed at the Kentenia site, reflected consistently high water levels, which were sustained by ground water. The third wetland (Four Level) was distinguished by irregular Eh fluctuations coinciding with strong seasonal ground-water upwelling. Although Fe³⁺ and SO₄ ²⁻ were the primary terminal electron acceptors in all wetlands, porewater chemistry also varied significantly by season and soil depth in response to piezometric water level fluctuations. Additional factors that influenced porewater chemistry included: (1) the presence of limestone parent materials that affected porewater pH, Ca²⁺, and Mg²⁺; and (2) the prevalence of sphagnum moss or graminoid species that influenced dissolved organic carbon, CO₂, and CH₄. Results from this study indicated the diverse range and importance of multiple factors in controlling biogeochemical processes and properties in small, high-elevation Appalachian wetlands.     

Geochemical processes in the Onyx River, Wright Valley, Antarctica: Major ions, nutrients, trace metals

We present data on major ions, nutrients and trace metals in an Antarctic stream. The Onyx River is located in Wright Valley (77-32 S; 161-34 E), one of a group of ancient river and glacier-carved landforms that comprise the McMurdo Dry Valleys of Antarctica. The river is more than 30 km long and is the largest of the glacial meltwater streams that characterize this relatively ice-free region near the Ross Sea. The complete absence of rainfall in the region and the usually small contributions of glacially derived tributaries to the main channel make this a comparatively simple system for geochemical investigation. Moreover, the lack of human impacts, past or present, provides an increasingly rare window onto a pristine aquatic system.For all major ions and silica, we observe increasing concentrations with distance from Lake Brownworth down to the recording weir near Lake Vanda. Chemical weathering rates are unexpectedly high and may be related to the rapid dissolution of ancient carbonate deposits and to the severe physical weathering associated with the harsh Antarctic winter. Of the nutrients, nitrate and dissolved reactive phosphate appear to have quite different sources. Nitrate is enriched in waters near the Lower Wright Glacier and may ultimately be derived from stratospheric sources; while phosphate is likely to be the product of chemical weathering of valley rocks and soils. We confirm the work of earlier investigations regarding the importance of the Boulder Pavement as a nutrient sink.Dissolved Mn, Fe, Ni, Cu, and Cd are present at nanomolar levels and, in all cases, the concentrations of these metals are lower than in average world river water. We hypothesize that metal uptake and exchange with particulate phases along the course of the river may serve as a buffer for the dissolved load. Concurrent study of these three solute classes points out significant differences in the mechanisms and sites of their removal from the Onyx River.     

Relict rock glaciers and protalus lobes in the British Isles: implications for Late Pleistocene mountain geomorphology and palaeoclimate

Many relict rock glaciers and protalus lobes have been described in mountainous areas of the British Isles. This paper reviews their distribution, chronology, supposed origin and development, and places the research within current investigations and knowledge. Rock glaciers and protalus lobes are located in a number of different topographic locations and settings. They developed at the base of steep cliffs following the catastrophic failure of rock faces, at the base of scree slopes following the gradual accumulation of rock debris and in association with glaciers. Protalus lobes probably developed in response to the permafrost creep of talus material while rock glaciers formed through the deformation and sliding of large bodies of buried ice. Rock glaciers probably developed, or were last active, during the Younger Dryas, although the possibility exists that some of these landforms are Dimlington Stadial in age. The development of protalus lobes during the Younger Dryas suggests that precipitation levels were low and permafrost was widespread during this time. The lack of rock glaciers (sensu stricto) in the British Isles compared with other mountain areas is believed to be a consequence of the rock type and relative scarcity of weathered debris for their formation rather than a lack of suitable sites or appropriate environmental conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Racetrack and Bonnie Claire: southwestern US playa lakes as analogs for Ontario Lacus, Titan

We note the geomorphological and meteorological processes at Racetrack Playa, Death Valley National Park, as analogs for those at Ontario Lacus on Titan. Although Ontario is ∼50× larger, the planforms of the two features are nearly identical, both are extremely flat, and are in environments where infrequent rainfall occurs against a climate, where evaporation exceeds precipitation. While the famous moving rocks on the Racetrack Playa may be exceptional on the Earth, the lower gravity and thicker atmosphere may render wind-induced rock transport comparatively common on Titan. Nearby Bonnie Claire Playa also provides field insights into the interpretation of remote sensing data from Titan.     

Combined microthermometric and Raman spectroscopic technique to determine the salinity of H2O-CO2-NaCl fluid inclusions based on clathrate melting

Fluid inclusions approximated by the system H₂O-CO₂-NaCl are common in many geologic environments. In order to apply microthermometric data from these inclusions to infer P-T (pressure-temperature) trapping conditions, the composition of the inclusions, including the salinity, must be known. Normally, salinities of aqueous inclusions are determined from ice-melting temperatures obtained during microthermometry. However, when CO₂-bearing aqueous fluid inclusions are cooled they often form a hydrate that incorporates H₂O into the structure, and salinities estimated from ice-melting temperatures are therefore higher than the actual salinity. A technique that combines data from Raman spectroscopic and microthermometric analyses of individual inclusions was developed to determine the salinity of CO₂-bearing aqueous inclusions based on measured clathrate melting temperatures and CO₂ pressures obtained from Raman analyses. In this study, the pressure within inclusions was determined using Raman spectroscopy based on the splitting of the Fermi diad of CO₂, measured at the clathrate melting temperature. The CO₂ densities (and pressures) predicted by the equation developed in this study are in relatively good agreement with previously published equations, except for very low densities and correspondingly low pressures. The combined Raman spectroscopy - microthermometry technique thus provides both the temperature and the pressure in the inclusion at clathrate melting. For inclusions in which the clathrate melts in the presence of CO₂ liquid, the salinity can be determined with a precision of a few tenths of a wt% NaCl, whereas for inclusions in which clathrate melts in the presence of CO₂ vapor the salinity error may be a few wt% NaCl. Applying the method to synthetic fluid inclusions with known salinity suggests that the technique is valid for determining salinity of H₂O-CO₂-NaCl fluid inclusions in which clathrate melts in the presence of liquid CO₂ only or vapor CO₂ only.     

Investigating the Spatiotemporal Links Between Disorder,Crime, and the Fear of Crime

While links between social and physical disorder, crime, and the fear of crime have long been areas of research interest, few studies have looked at these links from a spatiotemporal viewpoint. This is somewhat surprising, as many of the factors associated with disorder, crime, and fear are known to vary over time and space. This paper uses GISystems to investigate potential spatiotemporal links between these areas in Wollongong, New South Wales, with specific focus on links between graffiti and the fear of crime. The results reveal that the distribution of fear of crime varies considerably over time and is often spatially coincident with concentrations of disorder. Graffiti was found to be one of the most prevalent types of physical disorder. The results are discussed in the context of the “broken windows” thesis and strategic intervention at the community level.     

The distribution and stable carbon isotopic composition of dissolved organic carbon in estuaries

The distributions of dissolved organic carbon (DOC) and the natural carbon isotope ratio of DOC (DO¹³C) in estuaries reflect the predominant sources and sinks of organic matter from both allochthonous and autochthonous origins. The traditional view is that DOC in land-margin ecosystems reflects mainly the mixing of land-derived and oceanic DOC. However, this view is not consistent with the bulk of our data from a survey of DOC and DO¹³C distributions in estuaries on the East and Gulf coasts of the USA. While it is accurate that the DOC in estuaries includes material derived from land and from the ocean, the distributions of DOC and DO¹³C in several estuaries reflect additional DOC inputs from estuarine phytoplankton and tidal marshes. Even when DOC concentrations were distributed conservatively, the isotopic composition of the DOC revealed the existence of a dynamic cycle of DOC input and removal in some systems.     

Advances in Holocene mountain geomorphology inspired by sediment budget methodology

The sediment budget, which links sediment sources to sediment sinks with hydroclimatic and weathering processes mediating the response, is applied to the analysis of sediments in three alpine lakes in British Columbia. We provide two ways of using the sediment budget as an integrating device in the interpretation of mountain geomorphology. These approaches differ in their resolution and ability to budget the major components of the fine-sediment cascade in glaciated environments. Taken together, they provide an integrated index of landscape change over the Holocene. The first example compares the hydroclimatic controls of lake sedimentation for the last 600 years (A.D. 1370–1998) preserved in varved sediments from two of the lake basins. This hydroclimatological approach incorporates contemporary monitoring, air photo analysis, and detailed stratigraphy of sedimentation events within a single varve to infer the timing, sources, and preferred pathways of fine-grained sediments reaching the lake basins. The results indicate that glaciers, hillslope, and channel instability within the major subbasins are the principal sediment sources to the lake basins. Transitory sediment storage of glacially derived sediments within the channels is believed to modulate the episodic and more frequent delivery of sediments from adjacent hillslope and fluvial storage sites and direct routing of glacial rock flour during years of prolonged glacial melt. The second example, relying on the phosphorus geochemistry of sediments in an alpine lake basin, considers the evolution of phosphorus forms (from mineral to occluded and organic fractions) as a function of the soil development, inherent slope instability, and repeated cycles of glaciation and neoglaciation over the Holocene. This geochemical approach demonstrates that both neoglaciation and full glaciation have essentially zeroed the system in such a way that a high proportion of mineral phosphorus remains in the present lake sediments and the bioavailability of phosphorus (a key to ecosystem development) is low. Both examples illustrate the importance of variable sediment sources; the seasonality, frequency, and magnitude of sediment transfers; and the profound influence of ice cover over contemporary, neoglacial and Pleistocene time scales. They also signal the value of including both clastic and dissolved components in the sediment budget.