River Range Research Articles

The Effects of Regional Hydrologic Alteration on Fish Community Structure in Regulated Rivers

AbstractAlterations to temporal patterns of river flow regimes resulting from damming and flow regulation practices may have negative consequences for freshwater communities. However, little has been performed to develop a holistic approach to assess the effects of hydrologic alterations on fish communities across a wide range of rivers and between different regulation strategies. To address this, we used daily and hourly hydrologic data from gauges in 10 regulated and 14 unregulated Canadian rivers. Building on the Ecological Limits of Hydrologic Alteration concept, hydrologic alterations for many ecologically relevant flow indices were combined to obtain river‐specific hydrologic alteration scores. Extensive community surveys to estimate fish abundance, biomass, diversity indices and habitat guild representation provided data for the derivation of similar river‐specific biotic alteration scores relative to unregulated river conditions. Our results indicate that biological impairment consisting of significant biotic alteration relative to the means from unregulated rivers was directly related to increasing flow alteration scores, with the smallest fish and flow alteration scores observed in run‐of‐river systems and the greatest alteration scores under hydro‐peaking regimes. Our approach not only examined the relationship between river‐specific hydrologic alteration scores and the associated biotic responses, but also provided a more comprehensive assessment of the flow‐response alteration relationship between regulation practices, which may better inform future environmental flow management guidelines. Copyright © 2015 John Wiley & Sons, Ltd.

Complementary seasonal bias in records of Holocene paleoclimate, Bear River Range, Southeast Idaho

Complementary seasonal bias in records of Holocene paleoclimate, Bear River Range, Southeast Idaho

How seed traits predict floating times: a biophysical process model for hydrochorous seed transport behaviour in fluvial systems

SummaryMany plants disperse their seeds in waterbodies via hydrochoric transport. Despite a growing body of research into hydrochory, little is known about the fundamental seed traits that determine floatation ability or hydrochoric transport behaviour more generally. Seeds are transported in fluvial systems in one of three phases: surface transport, within the flow or incorporated in bedload. Seeds are often categorised as buoyant or non‐buoyant based on density, with little consideration of the morphological traits that determine how long seeds spend in each transport phase.We investigated the seed traits that best predict time spent floating under laboratory conditions, using sixty species of riparian plants from south‐eastern Australia. We measured and calculated key physical attributes (length, width, volume, surface area, mass, density, sphericity, roundness and shape category) and categorised seeds according to their primary dispersal modes (water/wind, vertebrate, adhesion, ants and unassisted).We used Cox's proportional hazards modelling to reveal that seed density and volume : surface area ratio were the physical traits that best predicted time spent floating. Volume : surface area ratio represents both seed size and shape, as it increases with size and sphericity. Our results showed that denser, larger and/or more spherical seeds (i.e. higher volume : surface area ratio) were poor floaters. They are therefore more likely to be transported in subsurface flow or as bedload.We combined our data with geomorphic models of sediment transport in flow to develop a biophysical process model of how hydrological forces and seed physical traits determine hydrochorous seed transport behaviour in rivers. The model describes how surface tension, buoyancy and flow velocity act on seed density and volume : surface area ratio to characterise time spent floating. We extrapolate from our data to conceptualise how these traits predict transitions between surface, subsurface and bedload transport. Hydrochoric seed transport behaviour and deposition are both threshold‐driven and multidirectional.Our process model is likely to be applicable across a range of different seed types in a range of rivers. It substantially increases our understanding of hydrochoric processes in rivers, lakes and lotic wetlands and will help illuminate the links between seed traits, hydrochoric transport and patterns of riparian vegetation and species composition.

An enigmatic earthquake in the continental mantle lithosphere of stable North America

The existence of earthquakes within continental lithospheric mantle remains a highly controversial topic. Here, we present a detailed set of seismological analyses confirming the occurrence of a mantle earthquake beneath the Wind River Range of central Wyoming. Combining regional waveform inversion with the analysis of the delay and relative amplitudes of teleseismically-observed depth phases, we demonstrate that the 2013 Wind River earthquake – a MW 4.7 highly-oblique thrust-faulting event – occurred at 75±8 km, well beneath the base of the crust. The magnitude, mechanism, and location of this earthquake suggest that it represents simple brittle failure at relatively high temperatures within the mantle lithosphere, as a result of tectonic, rather than magmatic, processes.

Calculation of the environmental dredging depth for removal of river sediments contaminated by heavy metals

Sediment contamination by heavy metals can result in significant damage to the ecological water environment. Sediment dredging is a useful way to reduce the adverse effects of heavy metal pollution in freshwater. The dredging depth is a key parameter in environmental dredging engineering. In this paper, we propose an innovative method called the critical-risk-depth method for calculating the environmental dredging depth that has been specifically designed for removal of river sediments contaminated by heavy metals. To determine the critical risk depth for dredging, the heavy metal concentrations at different sediment depths and their potential ecological risks must be tested and evaluated. The first step of the method involves analyzing sediments to determine the lateral and vertical distribution of heavy metals. In the next step, Hakanson’s potential ecological risk index is used to assess the ecological risk of heavy metals at different sediment depths. Finally, the recommended environmental dredging depths are calculated based on the potential risk for change in the vertical distribution and the given threshold level for the potential critical risk from heavy metals. We carried out a case study to determine the dredging depth for river sediment in Pinghu. The sediment analysis results show that the contents of Cd, Zn, and Pb are excessive when compared with the local soil background levels. Because of the accumulation effect of heavy metals in sediments, the heavy metal contents tend to decrease with sediment depth, but this trend may change as a result of human activities and other river dredging events. There is a high potential ecological risk level from heavy metal pollution in sediments in the study area, and the recommended environmental dredging depths of the ten rivers range from 35 to 100 cm.

Boat technology and culture in Chittagong

This ethnographic account of Chittagong’s maritime practices highlights the Bengal delta’s exceptional range of river and sea-going vessels. A multidisciplinary approach-based survey to patterns of shipbuilding and trade at Chittagong is lacking, remaining ignored outside the confines of folk specialists and local historians. Situated between South and Southeast Asia and traversing two regions—Bengal and Arakan—a study of Chittagong, one of the main Bay of Bengal ports from medieval times, requires crossing not only political borders but academic barriers as well. Ongoing practices are fundamental to highlighting traditions largely based on unrecorded transmissions.

Decoding potential effects of climate and vegetation change on mineral weathering in alpine soils: An experimental study in the Wind River Range (Wyoming, USA)

Climate change and a related increase in temperature, particularly in alpine areas, force both flora and fauna to adapt to the new conditions. These changes should in turn affect soil formation processes. The aim of this study was to identify possible consequences for soils in a dry-alpine region with respect to weathering of primary minerals and leaching of elements under expected vegetation and climate changes. To achieve this, a field empirical approach investigating an altitudinal sequence was used in combination with laboratory weathering experiments simulating several scenarios. The study sites are located in Sinks Canyon and Stough Basin of the Wind River Range, Wyoming, USA. The following sites (from moist to dry with increasing temperature along the sequence) were investigated: 10 soil profiles (Typic Haplocryoll) in a tundra ecotone, 10 soil profiles (Ustic Haplocryoll) in a pine-fir forest and 20 soil profiles (Ustic Argicryoll) in sagebrush. All soils developed on granitoid moraines. Soil mineralogy was analysed using cathodoluminescence and X-ray diffraction. This revealed that biotite and plagioclase were both weathered to smectite while plagioclase also weathered to kaolinite. Cooler, wetter, altitude-dependent conditions promoted weathering of primary minerals. Furthermore, the soils of the tundra and forest zone exhibited a higher acidity and more organic carbon.In a series of wet laboratory batch experiments, materials from topsoils (A horizons) and subsoils (B horizons) in each ecotone were examined alone or in combination with other samples. In a first step, aqueous extracts of the topsoil samples were generated in batch reactors and analysed for the main ions. In a second and a third step the topsoil extracts were reacted with the subsoil samples of the same ecotone, and with the subsoil samples of the ecotones at higher altitude. The total duration of these batch experiments was 1800h, and the solutes were measured using ICP-OES and ion chromatography. Dissolved Ca, Mg and K were mainly controlled by the chemical weathering of oligoclase, K-feldspar and biotite. With increasing altitude the total concentrations of Ca, Mg and K in the aqueous extracts decreased, the relative ionic contribution from K decreased, while the ionic contribution from Ca increased.Climate change (warming, changed precipitation) potentially will reduce weathering intensity, soil acidity and the content of organic carbon. An altitudinal shift in vegetation due to climate change seems to affect the ionic composition of the soil solution. In the case of a shift from forest to sagebrush and tundra to forest or sagebrush, the relative contribution from K would increase at the expense of Ca. We hypothesise that K will play an important role in future biogeochemical cycles under the assumptions of climate warming and subsequent vegetation shifts to higher altitudes.

INHERITED FLOODPLAINS AND REGIME OF SEDIMENTATION IN RIVERBED – FLOODPLAIN COMPLEXES

During circumpolar distribution of the large rivers with large streamflow the wide floodplains with high amplitude relief were formed in their valleys. While the discharge of the river diminished this relief was partly reformed in the course of the lateral reformations of the river channel and ancient floodplains on the large areas took on inherited character. Due to their wideness inherited floodplains serve as a effective barriers between the erosion part of the river system (erosion furrows on the slopes and gullies) and balka-river part where transit and accumulation of the sediments by the most part take place. The most part of the sediments from gullies and slopes accumulates on the inherited floodplain. In the result there is very low correlation of sediment transport regimes even between close ranges of the river. Dating of the sediments proves that as largest basins on the floodplain are being infilled and the level of the floodplain rises, the rate of accumulation and barrier effect diminish. At last the inherited floodplain relief changes totally due to lateral and vertical river bed deformations and sediment transport in this river range is being retrieved.

Detection of earlier snowmelt in the Wind River Range, Wyoming, using Landsat imagery, 1972–2013

In the western United States snow has been melting earlier in recent decades due to warmer winter and spring weather. This is particularly noticeable in the Pacific Northwest and coastal areas, yet has been less obvious in locations farther inland. Using the historical Landsat image archive, snow cover was mapped in the Wind River Range (WRR) in northwestern Wyoming, from 1972–2013. The objective of this work was to estimate the temporal change in the rate of snowmelt in the Fremont Lake basin of the WRR for the 42-year study period. Much of the streamflow in Wyoming originates from melting snow in the WRR. Streamflow is a significant contributor to the water resources for the north-central part of the state and has tremendous societal and economic impacts especially during the prolonged drought that is affecting the western U.S. Consistent with the ongoing and severe drought, data from the Pine Creek Above Fremont Lake gauge show a striking reduction in cumulative stream discharge in the 2000s vs. the decades of the 1970s, 1980s and 1990s. Snow-cover depletion curves derived from snow maps created from Landsat imagery were generated for the period 1972–2013. MODerate-Resolution Imaging Spectroradiometer (MODIS)-derived standard snow-cover maps were also used to generate snow-cover depletion curves, from 2000–2013, to provide an accuracy assessment of the Landsat technique. Landsat-derived mean snow-cover depletion curves from 2000–2013 and from the three previous decades, show that snow cover in the Fremont Lake basin is melting 16±10days earlier, on average, in the 2000s compared to the period from 1972–1999. Increasing spring and summer nighttime air temperature is the likely driver of the earlier snowmelt documented in the Landsat record.

Ecological changes in two contrasting lakes associated with human activity and dust transport in western Wyoming

The atmospheric transport and deposition of aerosols has the potential to influence the chemistry and biology of oligotrophic alpine lakes. In recent decades, dust and nitrogen emissions to alpine ecosystems have increased across large areas of the western U.S., including Wyoming. Here, we use sediment geochemistry and 87Sr/86Sr and 143Nd/144Nd isotopes to examine historical dust deposition rates to alpine lakes in the southwestern region of the Wind River Range, Wyoming. We evaluate the biological response using diatom fossil assemblages and sediment pigment concentrations. Sediment core analyses indicated that prior to a recent rise in dust flux, phosphorus concentrations and species composition were similar to those found in other alpine lakes in the region. Concomitant with a ∼50 fold increase in dust flux to the sediments circa 1940, sediment proxies revealed a two- to threefold increase in normalized sediment phosphorus content, an increase in the diatom-inferred total dissolved phosphorus concentration from ∼ 4 to 9-12 μg L−1, a tenfold increase in diatom production, and a relative increase in cyanobacteria abundance. The increase in dust influx during the 20th century appears to be due in part to human factors and demonstrates the potential for dust and other atmospheric pollutants to significantly alter remote aquatic ecosystems.

Spatial/temporal Variability of the Chegem Glacial River Hydro/chemical Characteristics

Analysis of the river water macro- and micro-component composition spatial/temporal dynamics in the mountain/glacial basin of the Chegem River (Kabardino-Balkaria State High-mountain Natural Reserve) has been carried out according the outcomes of 2014 field exploration. Background excess of Mn compounds has been found at the river range under study in respect of heavy metals.

Modeling habitat potential for elk expansion in Michigan, USA

ABSTRACT Elk (Cervus elaphus) range expansion and reintroduction is a topic of national interest in wildlife management. Eastern states are facilitating the recolonization of elk to historic ranges. Success of these herds depends on habitat evaluations, site-specific considerations of human tolerance to elk and interactions between elk and existing wildlife. Interest in elk restoration has increased for multiple stakeholders in Michigan (USA), where prospering elk suggest there is potential for range expansion. Habitat quality at the landscape scale for elk in Michigan depends primarily on available forage, suitable cover, habitat diversity, and road densities so we quantified these factors in the Upper Peninsula and northern Lower Peninsula of Michigan using a habitat suitability index model framework. We focused our analysis on target areas of interest and compared habitat suitability values occurring at those locations to values occurring within the current elk range (Pigeon River County State Forest area, or Pigeon River). We used elk habitat utilization information associated with the Pigeon River to validate and adjust our habitat suitability model. We also included a model that assigned less weight to the road density parameter, to account for uncertainty regarding the influence of roads on elk. Results from our habitat models suggested that patches of moderately suitable habitat exist outside the Pigeon River range in Michigan. Target areas differed in quality and quantity of habitat when compared to existing elk range, but habitat suitability values overlapped considerably among locations. Large patches of moderately suitable habitat also occurred outside of target areas. Results suggest that Michigan has potential to support an expanded elk range; however, additional site-specific considerations (land ownership, winter snowpack, deer-elk interaction, wolf density) likely need to be accounted for at potential restoration and expansion sites.

A century of glacier change in the Wind River Range, WY

The Wind River Range spans roughly 200km along the continental divide in western Wyoming and encompasses at least 269 glaciers and perennial snowfields totaling 34.34±0.13km2 (2006), including Gannett Glacier, the largest glacier (2.81km2) in the continental U.S. outside of Washington State. To track changing glacier and perennial snow surface area over the past century we used historic maps, aerial photography, and geologic evidence evident in said imagery. Since the end of the Little Ice Age (~1900), when the glaciers retreated from their moraines, to 2006 the ice-covered area shrank by ~47%. The main driver of surface area change was air temperature, with glaciers at lower elevations shrinking faster than those at higher elevations. The total contribution of ice wastage to late summer stream flow ranged from 0.4 to 1.5%, 0.9 to 2.8%, 1.7 to 5.4%, and 3.4 to 10.9% in four different watersheds, none of which exceeded 7% glacier cover. Results from previous studies were difficult to include because of differences in interpretation of glacier boundaries, because of poor imagery, or to extensive seasonal snow. These difficulties highlight potential problems in combining data sets from different studies and underscores the importance of reexamining past observations to ensure consistent interpretation.

Microwave Radiation Heating in Pressurized Vessels for the Rapid Extraction of Coal Samples for Broad Spectrum GC–MS Analysis

Soxhlet extraction has been successful at processing difficult to extract compounds from a variety of solid samples; however, the extraction is often time-consuming, uses large volumes of solvent, and can only process one sample at a time. This has been more evident in the sample preparation of coal and other complex geochemical samples for analysis by gas chromatography–mass spectrometry (GC–MS), where 72-h Soxhlet extractions are the norm. This study presents the development of a fast approach using a pressurized vessel system with either a hot air oven or microwave radiation heating. The techniques were tested with sub-bituminous (Powder River Range, Wyoming, U.S.A.) and bituminous (Fruitland Formation, Colorado, U.S.A.) coal samples. Performance of the pressure-vessel techniques in terms of extraction efficiency and extracted compound profiles (via GC–MS) were compared to that of a Soxhlet extraction. Overall 30–40% higher extraction efficiencies (by weight) were obtained with a 4 h hot air oven and a...

Estimates of Glacier Mass Loss and Contribution to Streamflow in the Wind River Range in Wyoming: Case Study

The Wind River Range is a continuous mountain range, approximately 160 km in length, in west-central Wyoming. The presence of glaciers results in meltwater contributions to streamflow during the late summer (July, August, and September: JAS) when snowmelt is decreasing; temperatures are high; precipitation is low; evaporation rates are high; and municipal, industrial, and irrigation water are at peak demands. Thus, the quantification of glacier meltwater (e.g., volume and mass) contributions to late summer/early fall streamflow is important, given that this resource is dwindling owing to glacier recession. The current research expands upon previous research efforts and identifies two glaciated watersheds, one on the east slope (Bull Lake Creek) and one on the west slope (Green River) of the Wind River Range, in which unimpaired streamflow is available from 1966 to 2006. Glaciers were delineated within each watershed and area estimates (with error) were obtained for the years 1966, 1989, and 2006. Glacier volume (mass) loss (with error) was estimated by using empirically based volume–area scaling relationships. For 1966 to 2006, glacier mass contributions to JAS streamflow on the east slope were approximately 8%, whereas those on the west slope were approximately 2%. The volume–area scaling glacier mass estimates compared favorably with measured (stereo pair remote sensed data) estimates of glacier mass change for three glaciers (Teton, Middle Teton, and Teepe) in the nearby Teton Range and one glacier (Dinwoody) in the Wind River Range.

Recent Alpine Glacier Variability: Wind River Range, Wyoming, USA

Glacier area and volume changes were quantified through the use of historical aerial photographs in the Wind River Range, Wyoming. Forty-four glaciers in the Wind River Range were analyzed using orthorectified aerial photography from 2012. This is an update to the work of Thompson et al. [1] in which the surface area changes of the 44 glaciers were estimated from 1966 to 2006. The total surface area of the glaciers was estimated to be 27.8 ± 0.8 km2, a decrease of 39% from 1966 and a decrease of 2% from 2006. The 2012 volume changes for the 44 glaciers were estimated using the Bahr et al. [2] volume-area scaling technique. The total glacier volume in 2012 was calculated to be 1.01 ± 0.21 km3, a decrease of 63% from 1966. These results, once compared to temperature and snowpack trends, suggest that the downward trend in snowpack as well as increasing temperatures seem to be the most likely driver of the glacier recessions. With Global Circulation Models (GCMs) forecasting higher temperatures and lower precipitation in the western U.S., it is likely that glaciers will continue to recede.Glacier area and volume changes were quantified through the use of historical aerial photographs in the Wind River Range, Wyoming. Forty-four glaciers in the Wind River Range were analyzed using orthorectified aerial photography from 2012. This is an update to the work of Thompson et al. [1] in which the surface area changes of the 44 glaciers were estimated from 1966 to 2006. The total surface area of the glaciers was estimated to be 27.8 ± 0.8 km2, a decrease of 39% from 1966 and a decrease of 2% from 2006. The 2012 volume changes for the 44 glaciers were estimated using the Bahr et al. [2] volume-area scaling technique. The total glacier volume in 2012 was calculated to be 1.01 ± 0.21 km3, a decrease of 63% from 1966. These results, once compared to temperature and snowpack trends, suggest that the downward trend in snowpack as well as increasing temperatures seem to be the most likely driver of the glacier recessions. With Global Circulation Models (GCMs) forecasting higher temperatures and lower precipitation in the western U.S., it is likely that glaciers will continue to recede.

Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams

Summary Elevated levels of fine sediment (suspended and deposited) are a common cause of ecological degradation in freshwater ecosystems. However, it is time‐consuming and expensive to monitor these parameters to support national and international water resource legislation. The Proportion of Sediment‐sensitive Invertebrates (PSI) index is a biomonitoring tool that is designed to identify the degree of sedimentation in rivers and streams. Despite having a sound biological basis, until now, the PSI index has only been tested against observed fine sediment data in two catchments; other published applications of the PSI index have relied on inferred fine sediment values. In this study, we report the results of a comprehensive analysis of the performance of the PSI index across a wide range of reference condition temperate stream and river ecosystems, including 835 sites with data on deposited sediment and 451 sites with data on suspended solids (>12 500 data points measured between 1978 and 2002). The effect of taxonomic level and taxonomic resolution on the performance of the PSI index was also examined, as was the performance of the PSI index against other non‐sediment‐specific indices, including Average Score Per Taxon (ASPT), Lotic‐invertebrate Index for Flow Evaluation (LIFE), Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance, % EPT abundance, EPT richness and % EPT richness. The results of this study show that the PSI index was more correlated with fine sediment metrics than the other biological indices tested: rs = −0.64, (P < 0.01, n = 2502) for deposited sediment and rs = −0.50 (P < 0.01, n = 1353) for suspended solids. We highlight the optimal conditions for applying the PSI index, in its current form. Given the variability in the relationship between PSI and fine sediment metrics, we propose that the use of data from more objective, quantitative methods of measuring deposited fine sediment may help to enhance the performance of the model for future applications and advance understanding of fine sediment dynamics and the pressure–response relationship.

Evaluating the quality of riparian forest vegetation: the Riparian Forest Evaluation (RFV) index

Aim of study: This paper presents a novel index, the Riparian Forest Evaluation (RFV) index, for assessing the ecological condition of riparian forests. The status of riparian ecosystems has global importance due to the ecological and social benefits and services they provide. The initiation of the European Water Framework Directive (2000/60/CE) requires the assessment of the hydromorphological quality of natural channels. The Directive describes riparian forests as one of the fundamental components that determine the structure of riverine areas. The RFV index was developed to meet the aim of the Directive and to complement the existing methodologies for the evaluation of riparian forests.Area of study: The RFV index was applied to a wide range of streams and rivers (170 water bodies) inSpain.Materials and methods: The calculation of the RFV index is based on the assessment of both the spatial continuity of the forest (in its three core dimensions: longitudinal, transversal and vertical) and the regeneration capacity of the forest, in a sampling area related to the river hydromorphological pattern. This index enables an evaluation of the quality and degree of alteration of riparian forests. In addition, it helps to determine the scenarios that are necessary to improve the status of riparian forests and to develop processes for restoring their structure and composition.Main results: The results were compared with some previous tools for the assessment of riparian vegetation. The RFV index got the highest average scores in the basins of northernSpain, which suffer lower human influence. The forests in central and southern rivers got worse scores. The bigger differences with other tools were found in complex and partially altered streams and rivers.Research highlights: The study showed the index’s applicability under diverse hydromorphological and ecological conditions and the main advantages of its application. The utilization of the index allows a better understanding of the status of riparian forests, and enhances improvements in the conservation and management of riparian areas.Keywords: riparian quality; Water Framework Directive; connectivity; indicator; hydromorphology.

Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion

The erosion of major mountain ranges is thought to be largely cannibalistic, recycling sediments that were deposited in the ocean or on the continents prior to mountain uplift. Despite this recognition, it has not yet been possible to quantify the amount of recycled material that is presently transported by rivers to the ocean. Here, we have analyzed the Li content and isotope composition (δLi7) of suspended sediments sampled along river depth profiles and bed sands in three of the largest Earth's river systems (Amazon, Mackenzie and Ganga–Brahmaputra rivers). The δLi7 values of river-sediments transported by these rivers range from +5.3 to −3.6‰ and decrease with sediment grain size. We interpret these variations as reflecting a mixture of unweathered rock fragments (preferentially transported at depth in the coarse fraction) and present-day weathering products (preferentially transported at the surface in the finest fraction). Only the finest surface sediments contain the complementary reservoir of Li solubilized by water–rock interactions within the watersheds. Li isotopes also show that river bed sands can be interpreted as a mixture between unweathered fragments of igneous and sedimentary rocks. A mass budget approach, based on Li isotopes, Li/Al and Na/Al ratios, solved by an inverse method allows us to estimate that, for the large rivers analyzed here, the part of solid weathering products formed by present-day weathering reactions and transported to the ocean do not exceed 35%. Li isotopes also show that the sediments transported by the Amazon, Mackenzie and Ganga–Brahmaputra river systems are mostly sourced from sedimentary rocks (>60%) rather than igneous rocks. This study shows that Li isotopes in the river particulate load are a good proxy for quantifying both the erosional rock sources and the fingerprint of present-day weathering processes. Overall, Li isotopes in river sediments confirm the cannibalistic nature of erosion and weathering.

Properties of modern dust accumulating in the Uinta Mountains, Utah, USA, and implications for the regional dust system of the Rocky Mountains

ABSTRACTA growing body of work is illuminating the importance of dust as a component of soil development and biogeochemical cycling in alpine environments of the Rocky Mountains. Nonetheless, important questions remain about the dust system in this region due to a paucity of focused studies and direct measurements. This project involved deployment of modified marble dust traps in the alpine zone of the Uinta Mountains of Utah to trap modern atmospheric dust over a two year period. Results indicate that dust accumulation rates are similar to values previously reported for the Wind River Range of Wyoming, but less than values for south‐western Colorado, suggesting a south‐to‐north decrease in regional dust flux. The overall mean grain size of Uinta dust is similar to values reported by prior studies in Colorado, indicating a general uniformity in grain size distribution. Uinta dust is dominated by quartz, plagioclase, K‐feldspar, and illite with trace amounts of kaolinite, chlorite, and amphibole. In contrast, only quartz and K‐feldspar are present in the Uinta bedrock, confirming an exotic origin for the dust arriving in the alpine zone. Exotic mineralogies have also been reported in dust from other mountain ranges in the western United States, indicating that eolian delivery of allochthonous minerals is a widespread process. Geochemical analysis reveals that Bi, Na, P, Zn, Sn, Cu, Cd, Ba, Ni, W, Sb, Pb, and Tl in Uinta dust are elevated 10 to > 80‐times above their abundances in local bedrock. These results support reports of anthropogenic elemental enrichment in lake sediments from Colorado and Utah. Patterns of elemental loading suggest that certain elements are delivered by winds arriving from different directions, raising the possibility that some elements could be associated with unique source areas. Copyright © 2014 John Wiley & Sons, Ltd.