Environmental Factors Associated With Natural Methane Occurrence in the Appalachian Basin          下载免费PDF全文

Lisa J. Molofsky  John A. Connor  Thomas E. McHugh  Stephen D. Richardson  Casper Woroszylo  Pedro J. Alvarez 《Ground water》2016,54(5):656-668

The recent boom in shale gas development in the Marcellus Shale has increased interest in the methods to distinguish between naturally occurring methane in groundwater and stray methane associated with drilling and production operations. This study evaluates the relationship between natural methane occurrence and three principal environmental factors (groundwater redox state, water type, and topography) using two pre‐drill datasets of 132 samples from western Pennsylvania, Ohio, and West Virginia and 1417 samples from northeastern Pennsylvania. Higher natural methane concentrations in residential wells are strongly associated with reducing conditions characterized by low nitrate and low sulfate ([NO₃^?] < 0.5 mg/L; [SO₄^2?] < 2.5 mg/L). However, no significant relationship exists between methane and iron [Fe(II)], which is traditionally considered an indicator of conditions that have progressed through iron reduction. As shown in previous studies, water type is significantly correlated with natural methane concentrations, where sodium (Na) ‐rich waters exhibit significantly higher (p<0.001) natural methane concentrations than calcium (Ca)‐rich waters. For water wells exhibiting Na‐rich waters and/or low nitrate and low sulfate conditions, valley locations are associated with higher methane concentrations than upland topography. Consequently, we identify three factors (“Low NO₃^? & SO₄^2?” redox condition, Na‐rich water type, and valley location), which, in combination, offer strong predictive power regarding the natural occurrence of high methane concentrations. Samples exhibiting these three factors have a median methane concentration of 10,000 µg/L. These heuristic relationships may facilitate the design of pre‐drill monitoring programs and the subsequent evaluation of post‐drill monitoring results to help distinguish between naturally occurring methane and methane originating from anthropogenic sources or migration pathways.  相似文献   

Nutrient fluxes between water column and sediments: Potential influence of the pearl oyster culture   总被引：1，自引：0，他引：1  

Gaertner-Mazouni N  Lacoste E  Bodoy A  Peacock L  Rodier M  Langlade MJ  Orempuller J  Charpy L 《Marine pollution bulletin》2012,65(10-12):500-505

This study quantifies benthic nutrient fluxes and sedimentation rates in the Ahe Atoll lagoon (French Polynesia), in two stations located under pearl oyster frames, and two control stations away from the pearl culture facility. Dissolved inorganic nitrogen fluxes ranged between 2 and 35μmolNm(-2)h(-1) and Soluble Reactive Phosphorus varied between -3 and 8.2μmolPm(-2)h(-1). Particulate sedimentation rates beneath the oysters were approximately five times higher than in the control zone and the percentage of small particles (?63μm) were about the twice. In contrast, sediment composition was similar under and outside the direct influence of oyster frames. In this ecosystem, where primary production is dependent on the available nitrogen, our study revealed that, while highly variable, benthic fluxes could sometimes contribute up to 28% of the nitrogen demand for primary production.  相似文献   

The Magnuson-Stevens act (1976) and its reauthorizations: Failure or success for the implementation of fishery sustainability and management in the US?     

Andrea Dell'Apa  Lisa SchiavinatoRoger A. Rulifson 《Marine Policy》2012,36(3):673-680

The Magnuson-Stevens Fishery Conservation and Management Act (1976), opened a new era of federal fishery management in the United States. It was enacted primarily to establish a system for conserving and managing fisheries in the new 200-mile (EEZ). The US assumed exclusive authority for managing all fisheries within the EEZ, except for highly migratory species such as tunas and billfishes. Within the framework of the Act, eight Regional Fishery Management Councils (Regional Councils) were created, which are responsible for preparing Fisheries Management Plans (FMPs) in federal waters under their jurisdiction. Each FMP must meet a series of National Standards (NSs) for conservation and management. The Act was reauthorized in 1996 with the passage of the Sustainable Fisheries Act (SFA), which aimed at fine tuning the fishery regulatory apparatus that was established under the original Act. This "fine tuning" involved increased attention to biological concerns, and removal of ambiguities within it. The Act was reauthorized again in 2007, mainly to provide for more clear directives and regulations to end overfishing. After more than thirty years since the Act was passed into law, the debate among conservationists, commercial and recreational fishery representatives, and politicians on the effectiveness of the Act in achieving its purported goals it still continues. Is the Act delivering on its promises? Do NSs reflect the most important priorities for the US fishery resources, conservation and sustainable exploitation? Do the Regional Councils represent all parties that should be involved in the fisheries resources management? The aim of this paper is to provide a critical analysis to answer these questions. This paper begins with a review of the Act and its background, followed by discussion and analysis of the Act's benefits and flaws. Finally, suggestions for the implementation of its structure and future directions in fishery management strategies are made.  相似文献   

Valley confinement as a factor of braided river pattern for the Platte River   总被引：2，自引：0，他引：2  

Lisa M. Fotherby   《Geomorphology》2009,103(4):562-576

The Platte River in Nebraska has evolved in the twentieth century from a predominantly braided river pattern to a mélange of meandering, wandering, anastomosed, island braided, and fully braided reaches. Identifying the factors that determine the occurrence of a fully braided main channel was the objective of this study. Aerial photography, gage flow data, ground-surveyed cross sections, bed material samples, and the results of sediment transport modeling were used to examine factors that control spatial change in main river pattern of the central Platte River. Valley confinement is identified as the determining factor of braided river in nine of eleven divisions of the central Platte River. Flow reduction and the interruption of sediment supply are identified as determining factors preventing fully braided river in the remaining two of eleven reaches.Valley confinement, the topography which limits the width of the floodplain, was initially measured as width between historical banks (predevelopment river banks). This metric was later refined to width between confining features (historical banks, remnant bars, bridge abutments, protected banks and levees). Under existing conditions, the main channel of the central Platte River is fully braided when valley confinement (width between confining features) is 600 m or less and begins to divide into the multiple channels of an anastomosed pattern when valley confinement (width between confining features) exceeds 600 m When Platte River flow is divided between two to four major anabranches, a fully braided pattern in the main channel of the main anabranch requires a more confined valley of 400 m or less.Valley confinement is demonstrated to be the dominant factor in determining river pattern in the central Platte River, although this factor is not normally considered in the continuum of channel pattern model. Conclusions from this study can be used to increase the occurrence of fully braided main channel in the central Platte River, to aid habitat recovery for endangered or threatened bird species that favor this river pattern. Consideration of valley confinement with river continuum factors can aid river managers by improving predictions of river pattern in response to management actions.  相似文献   

Enlivening development: Water management in post‐conflict Baucau city,Timor‐Leste     

Lisa Palmer 《Singapore journal of tropical geography》2010,31(3):357-370

This paper explores how the state and others involved in the ‘development enterprise’ in Timor‐Leste are (mis)recognizing the potential of the existing environmental governance and exchange capacities of local customary institutions and practices in relation to water supply and management. Examining the problematic of water supply in a particular place‐based instance – more specifically, the intermesh of the customary, state and market sectors – it ponders how customary institutions might be better supported to extend their range of political and economic credibility and contribute to a reconfiguration of dominant community managed water supply models. Drawing out the workings of a ‘diverse economy’ where a customary economy is enmeshed with, and to some extent undermining, a weak capitalist sector, the paper argues that a failure to address issues of resource ownership and control and to engage the strengths and import of local customary institutions will have serious ramifications for the successful implementation of national development objectives in post‐conflict Baucau city and elsewhere in Timor‐Leste. Instead, it argues for an enlivened development approach wherein locally socialized landscapes are recognized as credible political sites with which ‘development’ can engage and power relations can shift.  相似文献   

A literature review of Algerian salt lakes: values,threats and implications     

Fatma Demnati  Boujéma Samraoui  Farid Allache  Alain Sandoz  Lisa Ernoul 《Environmental Earth Sciences》2017,76(3):127

Chotts are salt lakes located in the arid regions of Northern Africa. These unique wetlands are recognized for their role in the migration and breeding of waterbirds and economic values generated from mineral extraction, agriculture and tourist activities. Despite their importance for flora and fauna biodiversity, they continue to face important threats due to human activities. This article consolidates a literature review of Algerian chotts from global to local importance. An in-depth view demonstrates the changes in land use of two large chotts in the southeastern region of Algeria: Chotts Merouane and Melghir. Land use images highlight a net expansion of agricultural lands, a decrease in grazing area around the lakes and a decrease of salt lake surface area. The local focus highlights the threats and changes of Algerian and Northern African chotts and proposes some perspectives for the future.  相似文献   

Tropical Deforestation and the Kyoto Protocol   总被引：11，自引：3，他引：8  

Márcio?SantilliEmail author  Paulo?Moutinho  Stephan?Schwartzman  Daniel?Nepstad  Lisa?Curran  Carlos?Nobre 《Climatic change》2005,71(3):267-276

The current annual rates of tropical deforestation from Brazil and Indonesia alone would equal four-fifths of the emissions reductions gained by implementing the Kyoto Protocol in its first commitment period, jeopardizing the goal of Protocol to avoid “dangerous anthropogenic interference” with the climate system. We propose the novel concept of “compensated reduction”, whereby countries that elect to reduce national level deforestation to below a previously determined historical level would receive post facto compensation, and commit to stabilize or further reduce deforestation in the future. Such a program could create large-scale incentives to reduce tropical deforestation, as well as for broader developing country participation in the Kyoto Protocol, and leverage support for the continuity of the Protocol beyond the 2008–2012 first commitment period.  相似文献   

Sulfur-isotope distribution and contamination related to the Balya Pb–Zn Mine in Turkey     

Murat Budakoglu  Lisa M. Pratt 《Environmental Geology》2005,47(6):773-781

Sulfur-isotope (³⁴S) values and weight (%) of acid-volatile sulfur (AVS), chrome-reducible sulfide (CRS), elemental sulfur (ES), and acid-soluble sulfates were determined in Balya Mine ore rock, mine wastes, and Kocacay River and Lake Manyas sediments. Estimation of isotopic fractionation (³⁴S) between product sulfate and initial CRS (pyrite) was used to evaluate the progress of sulfide oxidation in the mine-waste area. Water- and acid-soluble sulfate produced from different mine-waste samples, such as metallurgical waste (MW) and waste rock (WR), in laboratory experiments also shows distinct ³⁴S values and allows identification of the acid-mine-drainage sources in the mine-waste area. Average ³⁴S_SO4values are –1.43 for MW (n=4) and +2.06 for WR (n=8). Short (24 hr) and long (60 days) term leach experiments were considered using alternating wet/dry conditions to simulate sulfate-production capacity and metal-discharge characteristics for MW and WR piles. Release of heavy metals follows the order of Pb²⁺ >Mn²⁺ >Zn²⁺ >Cu²⁺ for these pile samples. Values of ³⁴S_SO4 for river water that was collected after 3–4 h of heavy rainfall are close to values of ³⁴S_SO4 for water-soluble sulfates from mine-waste piles used in laboratory leach experiments.This revised version was published in February 2005 with corrections to the placement of the figures.  相似文献   

Pleistocene geomorphology and geochronology of eastern Grand Canyon: linkages of landscape components during climate changes     

Matt D. Anders  Joel L. Pederson  Tammy M. Rittenour  Warren D. Sharp  John C. Gosse  Karl E. Karlstrom  Laura J. Crossey  Ronald J. Goble  Lisa Stockli  Guang Yang 《Quaternary Science Reviews》2005,24(23-24):2428-2448

We report new mapping, soils, survey, and geochronologic (luminescence, U-series, and cosmogenic-nuclide) data from Pleistocene deposits in the arid setting of eastern Grand Canyon. The result is a stratigraphic framework of inset fill gravels and associated terraces that provide a record of the responses of hillslopes, tributary streams, and the Colorado River to the last 400 kyr of glacial–interglacial climate change. The best-preserved last 80 kyr of this record indicates a stratigraphic–chronologic disconnect between both deposition and incision along the Colorado River versus along the trunks of local tributaries. For example, the Colorado River finished aggrading and had already begun incising before the main pulse of aggradation in the trunks of local catchments during Marine Isotope Stage 3, and then tributary incision followed during the millennial-scale fluctuations of the last glacial epoch, potentially concurrent with mainstem aggradation. The mainstem record appears to broadly correlate with regional paleoclimate and upstream geomorphic records and thus may be responding to climatic–hydrologic changes in its mountain headwaters, with aggradation beginning during full-glacial times and continuing into subsequent interglacials. The contrasting lag time in responses of the dryland catchments within Grand Canyon may be largely a function of the weathering-limited nature of hillslope sediment supply.  相似文献   

Intradaily variability of water quality in a shallow tidal lagoon: Mechanisms and implications     

Lisa V. Lucas  Deanna M. Sereno  Jon R. Burau  Tara S. Schraga  Cary B. Lopez  Mark T. Stacey  Konstantin V. Parchevsky  Vladimir P. Parchevsky 《Estuaries and Coasts》2006,29(5):711-730

Although surface water quality and its underlying processes vary over time scales ranging from seconds to decades, they have historically been studied at the lower (weekly to interannual) frequencies. The aim of this study was to investigate intradaily variability of three water quality parameters in a small freshwater tidal lagoon (Mildred Island, California). High frequency time series of specific conductivity, water temperature, and chlorophylla at two locations within the habitat were analyzed in conjunction with supporting hydrodynamic, meteorological, biological, and spatial mapping data. All three constituents exhibited large amplitude intradaily (e.g., semidiurnal tidal and diurnal) oscillations, and periodicity varied across constituents, space, and time. Like other tidal embayments, this habitat is influenced by several processes with distinct periodicities including physical controls, such as tides, solar radiation, and wind, and biological controls, such as photosynthesis, growth, and grazing. A scaling approach was developed to estimate individual process contributions to the observed variability. Scaling results were generally consistent with observations and together with detailed examination of time series and time derivatives, revealed specific mechanisms underlying the observed periodicities, including interactions between the tidal variability, heating, wind, and biology. The implications for monitoring were illustrated through subsampling of the data set. This exercise demonstrated how quantities needed by scientists and managers (e.g., mean or extreme concentrations) may be misrepresented by low frequency data and how short-duration high frequency measurements can aid in the design and interpretation of temporally coarser sampling programs. The dispersive export of chlorophylla from the habitat exhibited a fortnightly variability corresponding to the modulation of semidiurnal tidal currents with the diurnal cycle of phytoplankton variability, demonstrating how high frequency interactions can govern long-term trends. Process identification, as through the scaling analysis here, can help us anticipate changes in system behavior and adapt our own interactions with the system.  相似文献