A Stream‐Based Methane Monitoring Approach for Evaluating Groundwater Impacts Associated with Unconventional Gas Development     

Victor M. Heilweil  Bert J. Stolp  Briant A. Kimball  David D. Susong  Thomas M. Marston  Philip M. Gardner 《Ground water》2013,51(4):511-524

Gaining streams can provide an integrated signal of relatively large groundwater capture areas. In contrast to the point‐specific nature of monitoring wells, gaining streams coalesce multiple flow paths. Impacts on groundwater quality from unconventional gas development may be evaluated at the watershed scale by the sampling of dissolved methane (CH₄) along such streams. This paper describes a method for using stream CH₄ concentrations, along with measurements of groundwater inflow and gas transfer velocity interpreted by 1‐D stream transport modeling, to determine groundwater methane fluxes. While dissolved ionic tracers remain in the stream for long distances, the persistence of methane is not well documented. To test this method and evaluate CH₄ persistence in a stream, a combined bromide (Br) and CH₄ tracer injection was conducted on Nine‐Mile Creek, a gaining stream in a gas development area in central Utah. A 35% gain in streamflow was determined from dilution of the Br tracer. The injected CH₄ resulted in a fivefold increase in stream CH₄ immediately below the injection site. CH₄ and δ¹³C_CH4 sampling showed it was not immediately lost to the atmosphere, but remained in the stream for more than 2000 m. A 1‐D stream transport model simulating the decline in CH₄ yielded an apparent gas transfer velocity of 4.5 m/d, describing the rate of loss to the atmosphere (possibly including some microbial consumption). The transport model was then calibrated to background stream CH₄ in Nine‐Mile Creek (prior to CH₄ injection) in order to evaluate groundwater CH₄ contributions. The total estimated CH₄ load discharging to the stream along the study reach was 190 g/d, although using geochemical fingerprinting to determine its source was beyond the scope of the current study. This demonstrates the utility of stream‐gas sampling as a reconnaissance tool for evaluating both natural and anthropogenic CH₄ leakage from gas reservoirs into groundwater and surface water.  相似文献   

Robust Regulation of Alkalinity in Highly Uncertain Continuous Anaerobic Digestion Processes     

Víctor Alcaraz‐González  Fabián Azael Fregoso‐Sanchez  Hugo Oscar Mendez‐Acosta  Victor Gonzalez‐Alvarez 《洁净——土壤、空气、水》2013,41(12):1157-1164

In this paper, a multiple‐input multiple‐output (MIMO) model‐based robust control scheme is proposed for the indirect control of both total alkalinity and the ratio (intermediate alkalinity)/(total alkalinity) by regulating volatile fatty acid concentrations and strong ions concentration, while guaranteeing the so‐called operational stability in anaerobic digestion (AD) processes. The proposed MIMO regulator is an adaptive controller derived from an AD model which incorporates the physicochemical equilibrium of the system as well as the use of a robust interval observer to estimate key process bounds that are used in the computation of the control efforts. Numerical simulations were carried out for a number of operating conditions under the most uncertain scenarios. Results showed that the proposed multivariable control law is able to recover the system stability around a pre‐determined set point in the face of parameter uncertainty and load disturbances.  相似文献   

Earth observations during space shuttle flight STS‐41: Discovery's mission to planet earth     

Kamlesh P. Lulla  Michael R. Helfert  David L. Amsbury  Victor S. Whitehead  Cynthia A. Evans  M. Justin Wilkinson 《国际地球制图》2013,28(1):69-80

Abstract

Multi‐temporal ERS‐1 SAR data acquired over a large agricultural region in West Bengal was used to classify kharif crops like rice, jute and sugarcane. Rice crop grown under lowland management practice showed a temporal characteristic. The dynamic range of backscatter was highest for this crop in temporal SAR data. This was used to classify rice using temporal SAR data. Such temporal character was not observed for the other study crops, which may be due to the difference in cultivation practice and crop calendar. Significant increase in backscatter from the ploughed fields was used to derive information on onset and duration of land preparations. Synergistic use of optical remote sensing data and SAR data increased the separability of rice crop from homesteads and permanent vegetation classes.  相似文献   

A late Pleistocene human presence at Huaca Prieta,Peru, and early Pacific Coastal adaptations     

Tom D. Dillehay  Duccio Bonavia  Steve L. Goodbred  Mario Pino  Victor Vásquez  Teresa Rosales Tham 《Quaternary Research》2012,77(3):418-423

Archaeological excavations in deep pre-mound levels at Huaca Prieta in northern Peru have yielded new evidence of late Pleistocene cultural deposits that shed insights into the early human occupation of the Pacific coast of South America. Radiocarbon dates place this occupation between ~ 14,200 and 13,300 cal yr BP. The cultural evidence shares certain basic technological and subsistence traits, including maritime resources and simple flake tools, with previously discovered late Pleistocene sites along the Pacific coast of Peru and Chile. The results help to expand our knowledge of early maritime societies and human adaption to changing coastal environments.  相似文献   

Integrated provenance analysis of a convergent retroarc foreland system: U–Pb ages,heavy minerals,Nd isotopes,and sandstone compositions of the Middle Magdalena Valley basin,northern Andes,Colombia     

Junsheng Nie  Brian K. Horton  Joel E. Saylor  Andrés Mora  Maria Mange  Carmala N. Garzione  Asish Basu  Christopher J. Moreno  Victor Caballero  Mauricio Parra 《Earth》2012,110(1-4):111-126

Sediment provenance analysis remains a powerful method for testing hypotheses on the temporal and spatial evolution of uplifted source regions, but issues such as recycling, nonunique sources, and pre- and post-depositional modifications may complicate interpretation of results from individual provenance techniques. Convergent retroarc systems commonly contain sediment sources that are sufficiently diverse (continental magmatic arc, fold–thrust belt, and stable craton) to enable explicit provenance assessments. In this paper, we combine detrital zircon U–Pb geochronology, heavy mineral identification, Nd isotopic analyses, conventional sandstone petrography, and paleocurrent measurements to reconstruct the clastic provenance history of a long-lived sedimentary basin now exposed in an intermontane zone of the northern Andean hinterland of Colombia. The Middle Magdalena Valley basin, situated between the Central Cordillera and Eastern Cordillera, contains a 5–10 km-thick succession of Upper Cretaceous to Quaternary fill. The integrated techniques show a pronounced change in provenance during the Paleocene transition from the lower to upper Lisama Formation. We interpret this as a shift from an eastern cratonic source to a western Andean source composed of magmatic-arc rocks uplifted during initial shortening of the Central Cordillera. The appearance of detrital chloritoid and a shift to more negative ε_Nd(t=0) values in middle Eocene strata of the middle La Paz Formation are attributed to shortening-related exhumation of a continental basement block (La Cira–Infantas paleohigh), now buried, along the axis of the Magdalena Valley. The diverse provenance proxies also show distinct changes during middle to late Eocene deposition of the Esmeraldas Formation that likely reflect initial rock uplift and exhumation of the fold–thrust belt defining the Eastern Cordillera. Upsection, detrital zircon U–Pb ages and heavy mineral assemblages for Oligocene and younger clastic deposits indicate that the Mesozoic sedimentary cover of the Eastern Cordillera was recycled during continued Cenozoic shortening. Our multidisciplinary provenance study refines the tectonic history of the Colombian Andes and demonstrates that uncertainties related to sediment recycling, nonunique sources, source heterogeneity, and climate in interpreting provenance data can be minimized via an integrated approach.  相似文献   

Tectono-sequence stratigraphy and U–Pb zircon ages of the Rincón Blanco Depocenter,northern Cuyo Rift,Argentina     

Silvia Barredo  Farid Chemale  Claudia Marsicano  Janaína N. Ávila  Eduardo G. Ottone  Victor A. Ramos 《Gondwana Research》2012,21(2-3):624-636

Extensional processes that followed the Gondwanan Orogeny rise to the development of a series of rift basins along the continental margin over older accreted Eopaleozoic terranes. Stratigraphic, structural, paleontological, and isotopic studies are presented in this work in order to constrain the ages of the sedimentary infilling and to analyze the tectosedimentary evolution of one of the Cuyo basin depocenters, known as Rincón Blanco. This asymmetrical half-graben was filled by continental sediments under a strong tectonic control. The infilling was strongly controlled by tectonics which in term produced distinctive features along the whole sedimentary sequence. Using a combination of lithological and structural data the infilling was subdivided into packages of genetically linked units bounded by regional extended surfaces. Several tuffs and acid volcanic rocks have been collected across the whole section of the Rincon Blanco sub-basin for SHRIMP and LA-MC-ICPMS U–Pb zircon dating. The ages obtained range from 246.4 ± 1.1 Ma to 230.3 ± 1.5 Ma which is the time elapsed for the deposition of three tectono-sequence units separated by regional unconformities and mainly constrained to the Middle Triassic. They are interpreted as a result of a reactivation of the extensional system that has evolved along strike as segments of faults that linked together and/or as laterally propagating faults. Regional correlation with coeval rift basins permits to establish north-south propagation in the extensional regime along the western margin of SW Gondwana. This trending started in the lowermost Triassic and extended until the latest Triassic. Two of them were precisely correlated with Cerro Puntudo and Cacheuta half-graben systems. The new data indicate that the three sequences were mostly deposited during the Middle Triassic (246 to 230 Ma), with no evidence of sedimentation during Norian and Rhaetian, which is in conflict with some previous biostratigraphic studies.  相似文献   

Laboratory Validation of Ultra-Soft Soil Deformation Model     

Myint Win Bo  Victor Choa  Kai Sin Wong  Arul Arulrajah 《Geotechnical and Geological Engineering》2011,29(1):65-74

Ultra-soft soil with high moisture content will experience large strain deformation under one-dimensional compression with little or no gain in effective stress. Such deformation behaviour does not comply with Terzaghi’s effective stress gain theory. The e-log s_v^￠ \sigma_{v}^{\prime } relationship of ultra-soft soil is non-linear with large compression index in the first order of log cycle. This paper proposes three compression indices (C_c1^* C_{c1}^{*} , C_c2^* C_{c2}^{*} and C_c3^* C_{c3}^{*} ) for stresses covering three log cycles. Good prediction of settlement magnitude is possible with these newly proposed compression parameters for ultra-soft soil. In addition, implicit finite difference model applying the large strain theory is also proposed and validated with results from laboratory measurements. The time factor curves for ultra-soft soil with large strain compression are also proposed and validated.  相似文献   

Landslide susceptibility mapping of Tevankarai Ar sub-watershed,Kodaikkanal taluk,India, using weighted similar choice fuzzy model     

Sujatha  E. Ramani  Rajamanickam  Victor 《Natural Hazards》2011,59(1):401-425

This paper deals with the landslide susceptibility zonation of Tevankarai Ar sub-watershed using weighted similar choice fuzzy method in a GIS environment. There has been a rapid increase in landslide occurrences in the Kodaikkanal town and area surrounding the town specially in the settlements around the town and road links leading to and from the town. This necessitates a detailed study of slope instability problems in this area. It is observed that these incidences occur frequently during the monsoon and summer showers. Rainfall is identified as the prime triggering factor. Eleven physical factors that cause instability are identified as causative factors from the field investigations and landslide occurrences. Land use pattern, slope gradient, curvature and aspect, weathering index which are evaluated from the weathering ratios of different chemical constituents of the three major lithological variations, soil type, hydraulic conductivity of soil and soil thickness, geomorphology, drainage, and lineament have been utilized to prepare the spatial variation. A weighted similar choice fuzzy model which ranks a set of alternatives by identifying the similarity between the outcome of alternatives and outcome of ideal alternatives is used to rank the causative factors. Each causative factor is classified into sub-categories and rated based on their effect on stimulating the landslide event using qualitative judgment derived from field studies and landslide history. The prepared thematic maps of causative factors are integrated, utilizing the GIS software Arcmap. The outcome has projected the low, moderate, high, and very high landslide susceptibility zones. The high-hazard and very high-hazard areas fall in the northwestern part characterized by croplands and agricultural plantations, while the moderate hazard zones are seen in prominent settlements and low-hazard zones are observed in the sparse settlements and zones of less agricultural activity. The model is verified using the relative landslide density (R) index, and the susceptibility map is found to be consistent with the mapped landslide incidences. The results from this study illustrate that the use of weighted similar choice fuzzy method is suitable for landslide susceptibility mapping on regional scale in growing hill towns as Kodaikkanal town.  相似文献   

GIS based landslide susceptibility mapping of Tevankarai Ar sub-watershed, Kodaikkanal, India using binary logistic regression analysis   总被引：5，自引：0，他引：5  

Sujatha E RAMANI  Kumarvel PITCHAIMANI  Victor Rajamanickam GNANAMANICKAM 《山地科学学报》2011,8(4):505-517

Landslide susceptibility mapping is the first step in regional hazard management as it helps to understand the spatial distribution of the probability of slope failure in an area.An attempt is made to map the landslide susceptibility in Tevankarai Ar subwatershed,Kodaikkanal,India using binary logistic regression analysis.Geographic Information System is used to prepare the database of the predictor variables and landslide inventory map,which is used to build the spatial model of landslide susceptibility.The model describes the relationship between the dependent variable(presence and absence of landslide) and the independent variables selected for study(predictor variables) by the best fitting function.A forward stepwise logistic regression model using maximum likelihood estimation is used in the regression analysis.An inventory of 84 landslides and cells within a buffer distance of 10m around the landslide is used as the dependent variable.Relief,slope,aspect,plan curvature,profile curvature,land use,soil,topographic wetness index,proximity to roads and proximity to lineaments are taken as independent variables.The constant and the coefficient of the predictor variable retained by the regression model are used to calculate the probability of slope failure and analyze the effect of each predictor variable on landslide occurrence in thestudy area.The model shows that the most significant parameter contributing to landslides is slope.The other significant parameters are profile curvature,soil,road,wetness index and relief.The predictive logistic regression model is validated using temporal validation data-set of known landslide locations and shows an accuracy of 85.29 %.  相似文献   

Quantitative assessment of landslide hazard along transportation lines using historical records   总被引：2，自引：1，他引：1  

Pankaj Jaiswal  Cees J. van Westen  Victor Jetten 《Landslides》2011,8(3):279-291

In this paper, a quantitative landslide hazard model is presented for transportation lines, with an example for a road and railroad alignment, in parts of Nilgiri hills in southern India. The data required for the hazard assessment were obtained from historical records available for a 21-year period from 1987 to 2007. A total of 901 landslides from cut slopes along the railroad and road alignment were included in the inventory. The landslides were grouped into three magnitude classes based on the landslide type, volume, scar depth, and run-out distance. To calculate landslide hazard, we estimated the total number of individual landslides per kilometer of the (rail) road for different return periods, based on the relationship between past landslides (recorded in our database) and triggering events. These were multiplied by the probability that the landslides belong to a given magnitude class. This gives the hazard for a given return period expressed as the number of landslides of a given magnitude class per kilometer of (rail) road. The relationship between the total number of landslides and the return period was established using a Gumbel distribution model, and the probability of landslide magnitude was obtained from frequency–volume statistics. The results of the analysis indicate that the total number of landslides, from 1- to 50-year return period, varies from 56 to 197 along the railroad and from 14 to 82 along the road. In total, 18 hazard scenarios were generated using the three magnitude classes and six return periods (1, 3, 5, 15, 25, and 50 years). The hazard scenarios derived from the model form the basis for future direct and indirect landslide risk analysis along the transportation lines. The model was validated with landslides that occurred in the year 2009.  相似文献