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At least 1,099 records · Page 61Linked to original sources
USGS2016

Use of structured decision-making to explicitly incorporate environmental process understanding in management of coastal restoration projects: Case study on barrier islands of the northern Gulf of Mexico

Coastal ecosystem management typically relies on subjective interpretation of scientific understanding, with limited methods for explicitly incorporating process knowledge into decisions that must meet multiple, potentially competing stakeholder objectives. Conversely, the scientific community lacks methods for identifying which advancements in system understanding would have the highest value to decision-makers. A case in point is barrier island restoration, where decision-makers lack tools to objectively use system understanding to determine how to optimally use limited contingency funds when project construction in this dynamic environment does not proceed as expected. In this study, collaborative structured decision-making (SDM) was evaluated as an approach to incorporate process understanding into mid-construction decisions and to identify priority gaps in knowledge from a management perspective. The focus was a barrier island restoration project at Ship Island, Mississippi, where sand will be used to close an extensive breach that currently divides the island. SDM was used to estimate damage that may occur during construction, and guide repair decisions within the confines of limited availability of sand and funding to minimize adverse impacts to project objectives. Sand was identified as more limiting than funds, and unrepaired major breaching would negatively impact objectives. Repairing minor damage immediately was determined to be generally more cost effective (depending on the longshore extent) than risking more damage to a weakened project. Key gaps in process-understanding relative to project management were identified as the relationship of island width to breach formation; the amounts of sand lost during breaching, lowering, or narrowing of the berm; the potential for minor breaches to self-heal versus developing into a major breach; and the relationship between upstream nourishment and resiliency of the berm to storms. This application is a prototype for using structured decision-making in support of engineering projects in dynamic environments where mid-construction decisions may arise; highlights uncertainty about barrier island physical processes that limit the ability to make robust decisions; and demonstrates the potential for direct incorporation of process-based models in a formal adaptive management decision framework.

Mississippi↗
USGS2011

Consequences of increasing bioenergy demand on wood and forests: An application of the Global Forest Products Model

The Global Forest Products Model (GFPM) was applied to project the consequences for the global forest sector of doubling the rate of growth of bioenergy demand relative to a base scenario, other drivers being maintained constant. The results showed that this would lead to the convergence of the price of fuelwood and industrial roundwood, raising the price of industrial roundwood by nearly 30% in 2030. The price of sawnwood and panels would be 15% higher. The price of paper would be 3% higher. Concurrently, the demand for all manufactured wood products would be lower in all countries, but the production would rise in countries with competitive advantage. The global value added in wood processing industries would be 1% lower in 2030. The forest stock would be 2% lower for the world and 4% lower for Asia. These effects varied substantially by country. ?? 2011 Department of Forest Economics, SLU Ume??, Sweden.

Journal of Forest Economics↗
USGS2009

Movements of brown bullheads in Presque Isle Bay, Lake Erie, Pennsylvania

Presque Isle Bay, Lake Erie, was listed as an Area of Concern (AOC) by the International Joint Commission in part because of the high incidence of external tumor in brown bullheads. Verifying the source of the possible contaminant exposure is critical to addressing the AOC designation. We used telemetry tracking (n = 49 fish) to test the hypothesis that adult bullheads captured within the bay during spawning season do not exit the bay during the post-spawning summer and fall months. We analyzed genetic variation at 15 microsatellite loci for 112 adult fish from 5 locations, 4 inside the bay and 1 outside, in order to test for possible differences. Data from fixed-station receivers suggested fish did not leave Presque Isle Bay during the study period. Predicted locations outside Presque Isle Bay were only 0.1% of all predicted locations and were below the 0.2% error rate based on known manual relocations. However, there was evidence for movement within Presque Isle Bay. Most movement was between Misery Bay or Lagoons and the open bay area. Whereas telemetry results showed tendency for adult site fidelity, genetic results showed no differences among locations, indicating that there is a single panmictic population. Our telemetry data suggest that brown bullheads are likely a useful indicator species for environmental conditions in Presque Isle Bay, since adults likely are retained in the system.

Journal of Great Lakes Research↗
USGS2020

Trends and biological effects of environmental contaminants in lamprey

Environmental contamination is of global concern. Lamprey are scientifically, ecologically, culturally, and economically important fishes. Our study represents the first synthesis ever on environmental contamination in lamprey. Objectives of this study include: (1) evaluate lethal and sublethal effects of environmental contaminants on lamprey, thereby providing insight into the potential for environmental contaminants to affect lamprey abundance, (2) highlight the unique characteristics of contaminant accumulation in lamprey, (3) determine whether spatial and temporal trends observed in contaminant concentrations of other top predators of aquatic food webs are reflected in the spatial and temporal trends of contaminant concentrations of lamprey, (4) identify key environmental contaminants affecting consumption advisories for people eating lamprey, and (5) identify important gaps in our knowledge of environmental contamination in lamprey. The geographic scope of this synthesis is worldwide. We conclude that, in general, the environmental contaminant concentrations that have been experienced by lamprey in the wild appear to be nonlethal to lamprey. However, environmental contaminants exert sublethal effects on lamprey. Sea lamprey ( Petromyzon marinus ) and Pacific lamprey ( Entosphenus tridentatus ) are relatively high in total mercury (Hg) concentration compared with other fishes. Compared with other top predators, lamprey are relatively low in polychlorinated biphenyl (PCB) concentration and concentrations of organochlorine pesticides. We also conclude that regulations on the use of PCBs, beginning in the 1970s, were effective in dramatically reducing PCB concentration in lamprey since the 1970s. Emerging contaminants, such as pharmaceuticals, microplastics, and per- and polyfluorinated alkyl substances (PFAS), have yet to be studied in lamprey.

Journal of Great Lakes Research↗
USGS2005

Temporal analysis of the frequency and duration of low and high streamflow: Years of record needed to characterize streamflow variability

A temporal analysis of the number and duration of exceedences of high- and low-flow thresholds was conducted to determine the number of years required to detect a level shift using data from Virginia, North Carolina, and South Carolina. Two methods were used - ordinary least squares assuming a known error variance and generalized least squares without a known error variance. Using ordinary least squares, the mean number of years required to detect a one standard deviation level shift in measures of low-flow variability was 57.2 (28.6 on either side of the break), compared to 40.0 years for measures of high-flow variability. These means become 57.6 and 41.6 when generalized least squares is used. No significant relations between years and elevation or drainage area were detected (P>0.05). Cluster analysis did not suggest geographic patterns in years related to physiography or major hydrologic regions. Referring to the number of observations required to detect a one standard deviation shift as 'characterizing' the variability, it appears that at least 20 years of record on either side of a shift may be necessary to adequately characterize high-flow variability. A longer streamflow record (about 30 years on either side) may be required to characterize low-flow variability. ?? 2005 Elsevier B.V. All rights reserved.

Journal of Hydrology↗
USGS2008

Assessment of crop growth and soil water modules in SWAT2000 using extensive field experiment data in an irrigation district of the Yellow River Basin

SWAT, a physically-based, hydrological model simulates crop growth, soil water and groundwater movement, and transport of sediment and nutrients at both the process and watershed scales. While the different versions of SWAT have been widely used throughout the world for agricultural and water resources applications, little has been done to test the performance, variability, and transferability of the parameters in the crop growth, soil water, and groundwater modules in an integrated way with multiple sets of field experimental data at the process scale. Using an multiple years of field experimental data of winter wheat (Triticum aestivum L.) in the irrigation district of the Yellow River Basin, this paper assesses the performance of the plant-soil-groundwater modules and the variability and transferability of SWAT2000. Comparison of the simulated results by SWAT to the observations showed that SWAT performed quite unsatisfactorily in LAI predictions during the senescence stage, in yield predictions, and in soil-water estimation under dry soil-profile conditions. The unsatisfactory performance in LAI prediction might be attributed to over-simplified senescence modeling; in yield prediction to the improper computation of the harvest index; and in soil water under dry conditions to the exclusion of groundwater evaporation from the soil water balance in SWAT. In this paper, improvements in crop growth, soil water, and groundwater modules in SWAT were implemented. The saturated soil profile was coupled to the oscillating groundwater table. A variable evaporation coefficient taking into account soil water deficit index, groundwater depth, and crop root depth was used to replace the fixed coefficient in computing groundwater evaporation. The soil water balance included the groundwater evaporation. The modifications improved simulations of crop evapotranspiration and biomass as well as soil water dynamics under dry soil-profile conditions. The evaluation shows that the crop growth and soil water components of SWAT could be further refined to better simulate the hydrology of agricultural watersheds. ?? 2008 Elsevier B.V. All rights reserved.

Journal of Hydrology↗
USGS2019

Anthropogenic and geologic causes of anomalously high uranium concentrations in groundwater used for drinking water supply in the southeastern San Joaquin Valley, CA

Concentrations of uranium (U) >30 µg/L in groundwater are relatively uncommon in drinking water in the United States but can be of concern in those areas where complex interactions of aquifer materials and anthropogenic alterations of the natural flow regime mobilize uranium. High concentrations (>30 µg/L) of U in the southeastern San Joaquin Valley, California, USA, have been detected in 24 percent of 257 domestic, irrigation, and public-supply wells sampled across an approximately 110,000 km2 area. The location of high concentrations depends on the interactions of U sources from fluvial fans that originate in the Sierra Nevada to the east and seepage of irrigation water that contains high concentrations of HCO3 that leaches U from the sediments. In addition, interactions with phosphate (PO4) from fertilized irrigated fields may sequester U in the aquifer. Principal component analysis of the data demonstrates that HCO3 and ions associated with high total dissolved solids in the aquifer and the percentage of agriculture near the well sampled are associated with high U concentrations. Nitrate concentrations do not appear to control release of U to the aquifer. Age dating of the groundwater and generally increasing U concentrations of the past 25 years in resampled wells where irrigation is prevalent suggests that high U concentrations are associated with younger water, indicating that irrigation of fields over the past 100 years has significantly contributed to increasing concentrations and mobilizing U. In some places, the groundwater is supersaturated with uranyl-containing minerals, as would be expected in roll front deposits. In general, the interaction of natural geological sources high in U, the anthropogenically driven addition of HCO3 and possibly phosphate fertilizer, control the location and concentration of U in each individual fluvial fan, but the addition of nitrate in fertilizer does not appear control the location of high U. These geochemical interactions can be used to determine controls on anomalously high U in alluvial aquifers

California↗
USGS2009

Magnetostratigraphic correlations of Permian-Triassic marine-to-terrestrial sections from China

We have studied three Permian–Triassic (PT) localities from China as part of a combined magnetostratigraphic, 40 Ar/ 39 Ar and U–Pb radioisotopic, and biostratigraphic study aimed at resolving the temporal relations between terrestrial and marine records across the Permo-Triassic boundary, as well as the rate of the biotic recovery in the Early Triassic. The studied sections from Shangsi (Sichuan Province), Langdai (Guihzou Province), and the Junggar basin (Xinjiang Province), span marine, paralic, and terrestrial PT environments, respectively. Each of these sections was logged in detail in order to place geochronologic, paleomagnetic, geochemical, conodont and palynologic samples within a common stratigraphic context. Here we present rock-magnetic, paleomagnetic and magnetostratigraphic results from the three localities. At Shangsi, northern Sichuan Province, we sampled three sections spanning Permo-Triassic marine carbonates. Magnetostratigraphic results from the three sections indicate that the composite section contains at least eight polarity chrons and that the PT boundary occurs within a normal polarity chron a short distance above the mass extinction level and a reversed-to-normal (R-N) polarity reversal. Furthermore, the onset of the Illawarra mixed interval lies below the sampled section indicating that the uppermost Permian Changhsingian and at least part of the Wuchiapingian stages postdate the end of the Kiaman Permo-Carboniferous Reversed Superchron. At Langdai, Guizhou Province, we studied magnetostratigraphy of PT paralic mudstone and carbonate sediments in two sections. The composite section spans an R-N polarity sequence. Section-mean directions pass a fold test at the 95% confidence level, and the section-mean poles are close to the mean PT pole for the South China block. Based on biostratigraphic constraints, the R-N transition recorded at Langdai is consistent with that at Shangsi and demonstrates that the PT boundary occurred within a normal polarity chron a short distance above the mass extinction level. In the southern Junggar basin, Xinjiang Province, in northwest China, we determined the magnetostratigraphy of three sections of a terrestrial sequence. Normal and reversed polarity directions are roughly antipodal, and magnetostratigraphies from the three sections are highly consistent. Combined bio- and magneto-stratigraphy used to correlate this sequence to other PT sequences suggests that the previously-proposed biostratigraphic PT boundary in the Junggar sections was most likely misplaced by earlier workers suggesting that further work is necessary to confidently place the PT boundary there.

Journal of Asian Earth Sciences↗
USGS2013

The stability of sulfate and hydrated sulfate minerals near ambient conditions and their significance in environmental and planetary sciences

Sulfate and hydrated sulfate minerals are abundant and ubiquitous on the surface of the Earth and also on other planets and their satellites. The humidity-buffer technique has been applied to study the stability of some of these minerals at 0.1 MPa in terms of temperature-relative humidity space on the basis of hydration-dehydration reversal experiments. Updated phase relations in the binary system MgSO 4 -H 2 O are presented, as an example, to show how reliable thermodynamic data for these minerals could be obtained based on these experimental results and thermodynamic principles. This approach has been applied to sulfate and hydrated sulfate minerals of other metals, including Fe (both ferrous and ferric), Zn, Ni, Co, Cd, and Cu. Metal-sulfate salts play important roles in the cycling of metals and sulfate in terrestrial systems, and the number of phases extends well beyond the simple sulfate salts that have thus far been investigated experimentally. The oxidation of sulfide minerals, particularly pyrite, is a common process that initiates the formation of efflorescent metal-sulfate minerals. Also, the overall abundance of iron-bearing sulfate salts in nature reflects the fact that the weathering of pyrite or pyrrhotite is the ultimate source for many of these phases. Many aspects of their environmental significance are reviewed, particularly in acute effects to aquatic ecosystems related to the dissolution of sulfate salts during rain storms or snow-melt events. Hydrous Mg, Ca, and Fe sulfates were identified on Mars, with wide distribution and very large quantities at many locations, on the basis of spectroscopic observations from orbital remote sensing and surface explorations by rovers. However, many of these findings do not reveal the detailed information on the degree of hydration that is essential for rigorous interpretation of the hydrologic history of Mars. Laboratory experiments on stability fields, reactions pathways, and reaction rates of hydrous sulfates likely to be found on Mars enhance our understanding of the degrees of hydration of various sulfates that should currently exist on Mars at various seasons and locations and during various atmospheric pressure and obliquity periods. Two sets of systematic experiments were described; one on hydrous Mg sulfates and the other on hydrous Fe 3+ sulfates. Also, their implications to Mars sulfates mineralogy were discussed.

Journal of Asian Earth Sciences↗
USGS2005

The 2003 phreatomagmatic eruptions of Anatahan volcano - Textural and petrologic features of deposits at an emergent island volcano

Stratigraphic and field data are used in conjunction with textural and chemical evidence (including data from scanning electron microscope, electron microprobe, X-ray fluorescence, X-ray diffraction, and instrumental neutron activation analysis) to establish that the 2003 eruption of Anatahan volcano was mainly phreatomagmatic, dominated by explosive interaction of homogeneous composition low-viscosity crystal-poor andesite magma with water. The hydromagmatic mode of eruption contributed to the significant height of initial eruptive columns and to the excavation and eruption of altered rock debris from the sub-volcanic hydrothermal system. Volatile contents of glass inclusions in equilibrium phenocrysts less abundances of these constituents in matrix glass times the estimated mass of juvenile magma indicate minimum emissions of 19 kt SO2 and 13 kt Cl. This petrologic estimate of SO2 emission is an order-of-magnitude less than an estimate from TOMS. Similarly, inferred magma volumes from the petrologic data are an order of magnitude greater than those modeled from deformation data. Both discrepancies indicate additional sources of volatiles, likely derived from a separate fluid phase in the magma. The paucity of near-source volcanic-tectonic earthquakes preceding the eruption, and the dominance of sustained long-period tremor are attributed to the ease of ascent of the hot low-viscosity andesite, followed by a shallow phreatomagmatic mode of eruption. Phreatomagmatic eruptions are probably more common at emergent tropical island volcanoes, where shallow fresh-water lenses occur at near-sea-level vents. These relations suggest that phreatomagmatic explosions contributed to the formation of many of the near-sea-level craters and possibly even to the small calderas at the other Mariana islands.

Northern Mariana Islands↗
USGS2005

The 2003 eruption of Anatahan volcano, Commonwealth of the Northern Mariana Islands: Chronology, volcanology, and deformation

The first historical eruption on Anatahan Island occurred on 10 May 2003 from the east crater of the volcano. The eruption was preceded by several hours of seismicity. Two and a half hours before the outbreak, the number of earthquakes surged to more than 100 events per hour. At 0730 UTC, the Washington Volcanic Ash Advisory Center issued an ash advisory. Although the eruption lasted for 3 months, the majority of erupted material was expelled during the first 2 weeks. The opening episode of the eruption resulted in a deposit of juvenile scoria and lithic clasts, the latter derived from geothermally altered colluvial fill from the vent area. The opening episode was followed by crater enlargement and deepening, which produced deposits of coarse, reddish-brown ash containing a mixture of juvenile and lithic clasts. The third episode of the eruption produced coarse ash and lapilli comprised of juvenile scoria and minor amounts of lithics. Plume heights were 4500 to 13,000 m for the initial three phases. The fourth episode, from about May 18 through early August, was characterized by smaller plume heights of 900 to 2400 m, and steam was the dominant component. Minor amounts of coarse ash and accretionary-lapilli ash comprise most of the deposits of the fourth episode, although ballistic blocks and bombs of andesite lava are also locally present. These andesite blocks were emplaced by an explosion on 14 June, which destroyed a small lava dome extruded during the first week of June. Activity waned as the summer progressed, and subsequent ash deposits accumulated in July and early August, by which time the eruption had effectively ended. In September and October, degassing and geothermal activity continued, characterized by small geysers, boiling water, and jetting steam. Noteworthy deviations from this activity were a surge event in late May–early June and the destruction of the lava dome on 14 June. We calculated on-land tephra-fall deposits to have a bulk volume of about 27.5 × 10 6 m 3 , covering an area of 40.6 km 2 . We determined the juvenile to lithic content of the deposits and corrected the bulk volume to a juvenile volume of 24.0 × 10 6 m 3 . We use a volume corrected density of 1.32 g/cm 3 to convert the juvenile volume of 24.0 × 10 6 m 3 to a magma volume of 13.2 × 10 6 m 3 . Using the methods of Fierstein and Nathenson (1992) [Fierstein, J., Nathenson, M., 1992. Another look at the calculation of fallout tephra volumes. Bull. Volcanology. 54, 156–167.], we computed the total eruption volume at 45.4 × 10 6 m 3 . Deformation surveys recorded large changes surrounding the east crater. The modeled volumetric change based on the surveys was 0.82 × 10 6 m 3 of magma, which we estimate corresponds to a minimum intrusion of 10 × 10 6 m 3 of magma which is in good agreement with our calculated on-land magma volume.

Anatahan volcano↗
USGS2006

Youngest volcanism about 1 million years ago at Kahoolawe Island, Hawaii

Young volcanic deposits in Kahoolawe Island, cutting up through the caldera-filling lava, colluvium and talus in the west wall of Kanapou Bay, had long been stratigraphically considered the rejuvenated-stage products. New K-Ar ages, combined with magnetic polarity data, show that young volcanism was at about 0.98-1.04 Ma and indicate no substantial quiescence between the filling of the caldera and the young volcanism. This result, and the tholeiitic characteristics of the young deposits, suggest they are a component of late shield-stage volcanism. ?? 2005 Elsevier B.V. All rights reserved.

Hawaii↗
USGS2008

Volcanic risk perception of young people in the urban areas of Vesuvius: Comparisons with other volcanic areas and implications for emergency management

More than 600 000 people are exposed to volcanic risk in the urban areas near the volcano, Vesuvius, and may need to be evacuated if there is renewed volcanic activity. The success of a future evacuation will strongly depend on the level of risk perception and preparedness of the at-risk communities during the current period of quiescence. The volcanic risk perception and preparedness of young people is of particular importance because hazard education programs in schools have been shown to increase the clarity of risk perception and students often share their knowledge with their parents. In order to evaluate young people's risk perception and preparedness for a volcanic crisis, a multiple choice questionnaire was distributed to 400 high-school students in three municipalities located close to the volcano. The overall results suggest that despite a 60-year period of quiescence at Vesuvius, the interviewed students have an accurate perception of the level of volcanic risk. On the other hand, the respondents demonstrate a clear lack of understanding of volcanic processes and their related hazards. Also, the interviewed students show high levels of fear, poor perceived ability to protect themselves from the effects of a future eruption, and insufficient knowledge of the National Emergency Plan for Vesuvian Area (NEPVA). The latter result suggests that in comparison with volcanic crises in other regions, during a future eruption of Vesuvius, there may not be enough time to educate the large number of people living near the volcano about how to appropriately respond. The inadequate risk education and preparedness of respondents implies that a strong effort is needed to improve communication strategies in order to facilitate successful evacuations. Therefore, it is important to take advantage of the present period of quiescence at Vesuvius to improve the accuracy of risk perception of youth in local communities. ?? 2008.

Journal of Volcanology and Geothermal Research↗
USGS2008

Hawaiian cultural influences on support for lava flow hazard mitigation measures during the January 1960 eruption of Kīlauea volcano, Kapoho, Hawai‘i

In 1960, Kīlauea volcano in Hawaii erupted, destroying most of the village of Kapoho and forcing evacuation of its approximately 300 residents. A large and unprecedented social science survey was undertaken during the eruption to develop an understanding of human behavior, beliefs, and coping strategies among the adult evacuees ( n = 160). Identical studies were also performed in three control towns located at varying distances from the eruption site ( n = 478). During these studies data were collected that characterized ethnic grouping and attitudes toward Hawaiian cultural issues such as belief in Pele and two lava flow mitigation measures—use of barriers and bombs to influence the flow of lava, but the data were never published. Using these forgotten data, we examined the relationship between Hawaiian cultural issues and attitudes toward the use of barriers and bombs as mitigation strategies to protect Kapoho. On average, 72% of respondents favored the construction of earthen barriers to hold back or divert lava and protect Kapoho, but far fewer agreed with the military's use of bombs (14%) to protect Kapoho. In contrast, about one-third of respondents conditionally agreed with the use of bombs. It is suggested that local participation in the bombing strategy may explain the increased conditional acceptance of bombs as a mitigation tool, although this can not be conclusively demonstrated. Belief in Pele and being of Hawaiian ethnicity did not reduce support for the use of barriers, but did reduce support for bombs in both bombing scenarios. The disparity in levels of acceptance of barriers versus bombing and of one bombing strategy versus another suggests that historically public attitudes toward lava flow hazard mitigation strategies were complex. A modern comparative study is needed before the next damaging eruption to inform debates and decisions about whether or not to interfere with the flow of lava. Recent changes in the current eruption of Kīlauea make this a timely topic.

Hawaii↗
USGS2000

Considerations involved with the use of semipermeable membrane devices for monitoring environmental contaminants

Semipermeable membrane devices (SPMDs) are used with increasing frequency, and throughout the world as samplers of organic contaminants. The devices can be used to detect a variety of lipophilic chemicals in water, sediment/soil, and air. SPMDs are designed to sample nonpolar, hydrophobic chemicals. The maximum concentration factor achievable for a particular chemical is proportional to its octanol–water partition coefficient. Techniques used for cleanup of SPMD extracts for targeted analytes and for general screening by full-scan mass spectrometry do not differ greatly from techniques used for extracts of other matrices. However, SPMD extracts contain potential interferences that are specific to the membrane–lipid matrix. Procedures have been developed or modified to alleviate these potential interferences. The SPMD approach has been demonstrated to be applicable to sequestering and analyzing a wide array of environmental contaminants including organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dioxins and dibenzofurans, selected organophosphate pesticides and pyrethroid insecticides, and other nonpolar organic chemicals. We present herein an overview of effective procedural steps for analyzing exposed SPMDs for trace to ultra-trace levels of contaminants sequestered from environmental matrices.

Journal of Chromatography A↗
USGS2001

Effect of canopy removal on snowpack quantity and quality, fraser experimental forest, Colorado

Snowpack peak water equivalent (PWE), ion concentration, content, and spatial distribution of ion load data from spring 1987-1996 in a 1 ha clearcut and adjacent forested plots vegetated by mature Picea engelmannii and Abies lasiocarpa in the Fraser experimental forest (FEF), Colorado are presented. Our objectives were: (1) to see if a forest opening might redistribute snowfall, snowpack moisture, and snowpack chemical content, and (2) to examine the importance of canopy interception on snowpack quantity and chemistry. On an average, the canopy intercepted 36% of snowfall. Interception was correlated with snowfall amount, snowpack PWE beneath the canopy, and air temperature. Canopy removal increased snowpack PWE to >90% cumulative snowfall inputs. Snowpack K-, H-, and NH4+ concentrations on the clearcut were lower and NO3- higher than in the snowpack beneath the forested plots. Cu mulative snowfall K+ input was less than in the clearcut snowpack; H+ inputs were greater in snowfall than in the snowpack of any plot; and inorganic N (NO3- and NH4+) inputs from snowfall to the clearcut were greater than to the forested plots. Processes accounting for the differences between snowfall inputs and snowpack ion content were leaching of organic debris in the snowpack, differential elution of the snowpack, and canopy retention. There were significant trends by year in snowpack ion content at PWE without similar trends in snowfall inputs. This finding coupled with snowpack ion elution bring into question the use of snowpack chemistry as an indicator of winter atmospheric inputs in short-term studies. ?? 2001 Elsevier Science B.V.

Journal of Hydrology↗
USGS2002

Groundwater hydrochemistry in the active layer of the proglacial zone, Finsterwalderbreen, Svalbard

Glacial bulk meltwaters and active-layer groundwaters were sampled from the proglacial zone of Finsterwalderbreen during a single melt season in 1999, in order to determine the geochemical processes that maintain high chemical weathering rates in the proglacial zone of this glacier. Results demonstrate that the principle means of solute acquisition is the weathering of highly reactive moraine and fluvial active-layer sediments by supra-permafrost groundwaters. Active-layer groundwater derives from the thaw of the proglacial snowpack, buried ice and glacial bulk meltwaters. Groundwater evolves by sulphide oxidation and carbonate dissolution. Evaporation- and freeze-concentration of groundwater in summer and winter, respectively produce Mg-Ca-sulphate salts on the proglacial surface. Re-dissolution of these salts in early summer produces groundwaters that are supersaturated with respect to calcite. There is a pronounced spatial pattern to the geochemical evolution of groundwater. Close to the main proglacial channel, active layer sediments are flushed diurnally by bulk meltwaters. Here, Mg-Ca-sulphate deposits become exhausted in the early season and geochemical evolution proceeds by a combination of sulphide oxidation and carbonate dissolution. At greater distances from the channel, the dissolution of Mg-Ca-sulphate salts is a major influence and dilution by the bulk meltwaters is relatively minor. The influence of sulphate salt dissolution decreases during the sampling season, as these salts are exhausted and waters become increasingly routed by subsurface flowpaths. ?? 2002 Elsevier Science B.V. All rights reserved.

Journal of Hydrology↗