Satellite-derived vegetation index and cover type maps for estimating carbon dioxide flux for arctic tundra regions

The spatial variability and co-variability of two different types of remote sensing derivatives that portray vegetation and geomorphic patterns are analyzed in the context of estimating regional-scale CO₂ flux from land surfaces in the arctic tundra. For a study area encompassing the Kuparuk River watershed of the North Slope of Alaska, we compare satellite-derived maps of the normalized difference vegetation index (NDVI) generated at two different spatial resolutions to a map of vegetation types derived by image classification of data from the Landsat multispectral scanner (MSS). Mean values of NDVI for each cover type stratum are unique (with the exception of moist acidic tundra and shrubland types). Based on analysis of semi-variograms generated for SPOT-NDVI data, most of the vegetation cover and landform features of this arctic tundra landscape have spatial dimensions of less than 1 km. Thaw lakes on the coastal plain and glacial depositional landforms, such as moraines in the foothills, seem to be the largest features, with vegetation units having dimensions no larger than 700 m. Frequency distributions of NDVI and vegetation types extracted for sampling transects flown by an aircraft sensing CO₂ flux, relative to distributions for the entire Kuparuk River watershed, suggest a slight sampling bias towards greater cover of mesic wet sedge tundra and thaw lakes and associated lower NDVI values. The regional pattern of NDVI for the North Slope of Alaska corresponds primarily to differences between the two major physiographic provinces of this region.     

Applied focused ion beam techniques for sample preparation of astromaterials for integrated nanoanalysis

Abstract— Sample preparation is always a critical step in the study of micrometer‐sized astromaterials available for study in the laboratory, whether their subsequent analysis is by electron microscopy or secondary ion mass spectrometry. A focused beam of gallium ions has been used to prepare electron transparent sections from an interplanetary dust particle (IDP), as part of an integrated analysis protocol to maximize the mineralogical, elemental, isotopic, and spectroscopic information extracted from one individual particle. In addition, focused ion beam (FIB) techniques have been employed to extract cometary residue preserved on the rims and walls of microcraters in 1100 series aluminum foils that were wrapped around the sample tray assembly on the Stardust cometary sample collector. Non‐ideal surface geometries and inconveniently located regions of interest required creative solutions. These include support pillar construction and relocation of a significant portion of sample to access a region of interest. Serial sectioning, in a manner similar to ultramicrotomy, is a significant development and further demonstrates the unique capabilities of focused ion beam microscopy for sample preparation of astromaterials.     

Performance Assessment of Pump‐and‐Treat Systems

Pump‐and‐treat (P&T) is a widely applied remedy for groundwater remediation at many types of sites for multiple types of contaminants. Decisions regarding major changes in the remediation approach are an important element of environmental remediation management for a site using P&T. While existing guidance documents provide information on design, operation, and optimization for P&T systems, these documents do not provide specific technical guidance to support remedy decisions regarding when to transition to a new remedy or to initiate closure of the P&T remedy. A structured approach for P&T performance assessment was developed and is described herein, using analysis of three example P&T systems. These examples highlight key aspects of the performance assessment decision logic and represent assessment outcomes associated with optimizing the P&T system, transitioning from P&T to natural attenuation, and supplementing P&T with another technology to hasten transition to natural attenuation.     

Forecasting of Horizontal Gas Well Production Decline in Unconventional Reservoirs using Productivity,Soft Computing and Swarm Intelligence Models

Natural Resources Research - The most widely used production decline forecasting tools are numerical reservoir simulation, material balance estimates and advanced methods of production decline...     

Preparation of large Stardust aluminum foil craters for analysis

Over the last decade, silica aerogel tracks and aluminum foil craters on the Stardust collector have been studied extensively to determine the nature of captured cometary dust grains. Analysis of particles captured in aerogel has been developed to a fine art, aided by sophisticated preparation techniques, and yielding revolutionary knowledge of comet dust mineralogy. The Stardust foil craters can be interpreted in terms of impacting particle size and structure, but almost all studies of composition for their contents have relied on in situ analysis techniques or relatively destructive extraction of materials. This has limited their examination and interpretation. However, numerous experimental hypervelocity impact studies under Stardust-Wild 2 encounter conditions have shown that abundant dust components are preserved in foil craters of all sizes. Using some of these analogue materials, we have previously shown that modern, nondestructive scanning electron microscope imaging and X-ray microanalysis techniques can document distribution of dust remnants both quickly and thoroughly within foil craters prior to any preparation. Here we present findings from our efforts to quantify the amount of residue and demonstrate a simple method of crater shape modification which can bring material into positions where it is much more accessible for in situ analysis, or safe removal of small subsamples. We report that approximately 50% of silicate-dominated impactors were retained as impact crater residue; however, <3% of organic impactors remained in the craters after impact.