Improved Method for Estimating Reaction Rates During Push-Pull Tests

The breakthrough curve obtained from a single-well push-pull test can be adjusted to account for dilution of the injection fluid in the aquifer fluid. The dilution-adjusted breakthrough curve can be analyzed to estimate the reaction rate of a solute. The conventional dilution-adjusted method assumes that the ratios of the concentrations of the nonreactive and reactive solutes in the injection fluid vs. the aquifer fluid are equal. If this assumption is invalid, the conventional method will generate inaccurate breakthrough curves and may lead to erroneous conclusions regarding the reactivity of a solute. In this study, a new method that generates a dilution-adjusted breakthrough curve was theoretically developed to account for any possible combination of nonreactive and reactive solute concentrations in the injection and aquifer fluids. The newly developed method was applied to a field-based data set and was shown to generate more accurate dilution-adjusted breakthrough curves. The improved dilution-adjusted method presented here is simple, makes no assumptions regarding the concentrations of the nonreactive and reactive solutes in the injection and aquifer fluids, and easily allows for estimating reaction rates during push-pull tests.     

Land-use transition for bioenergy and climate stabilization: model comparison of drivers,impacts and interactions with other land use based mitigation options

In this article, we evaluate and compare results from three integrated assessment models (GCAM, IMAGE, and ReMIND/MAgPIE) regarding the drivers and impacts of bioenergy production on the global land system. The considered model frameworks employ linked energy, economy, climate and land use modules. By the help of these linkages the direct competition of bioenergy with other energy technology options for greenhouse gas (GHG) mitigation, based on economic costs and GHG emissions from bioenergy production, has been taken into account. Our results indicate that dedicated bioenergy crops and biomass residues form a potentially important and cost-effective input into the energy system. At the same time, however, the results differ strongly in terms of deployment rates, feedstock composition and land-use and greenhouse gas implications. The current paper adds to earlier work by specific looking into model differences with respect to the land-use component that could contribute to the noted differences in results, including land cover allocation, land use constraints, energy crop yields, and non-bioenergy land mitigation options modeled. In scenarios without climate change mitigation, bioenergy cropland represents 10–18 % of total cropland by 2100 across the different models, and boosts cropland expansion at the expense of carbon richer ecosystems. Therefore, associated emissions from land-use change and agricultural intensification as a result of bio-energy use range from 14 and 113 Gt CO2-eq cumulatively through 2100. Under climate policy, bioenergy cropland increases to 24–36 % of total cropland by 2100.     

Karst depressions in a time context

A study of karst depression enlargement through time on the Western Highland Rim (physiographic province), based on two sets of aerial photography (1937, 1972) and field work, indicates that areal growth rates (dA/dt, m²/a) depend upon the surficial geologic setting. Areal growth rates were calculated from rates of long axis (dL/dt) and mean width (dW/dt) enlargement assuming an elliptical plan shape. Areal growth rates averaged 40, 70, and 100 m²/century for loessial, clayey residual, and silty colluvial surficial material, respectively. Estimates of average apparent age of karst depressions in each of the three surficial materials, based on linear growth rates, varied from 25,000 to 65,000 years B.P. An occurrence of mastodon (Mammut americanum) and ground sloth (Megalonyx jeffersoni) from the Darks Mill depression as well as a pollen record from another depression dating from the Late Wisconsin glacial maximum in the same geomorphic setting yielded dates compatible with estimates of depression age.     

Rapid underway profiling of water quality in Queensland estuaries

We present an overview of a portable underway water quality monitoring system (RUM-Rapid Underway Monitoring), developed by integrating several off-the-shelf water quality instruments to provide rapid, comprehensive, and spatially referenced 'snapshots' of water quality conditions. We demonstrate the utility of the system from studies in the Northern Great Barrier Reef (Daintree River) and the Moreton Bay region. The Brisbane dataset highlights RUM's utility in characterising plumes as well as its ability to identify the smaller scale structure of large areas. RUM is shown to be particularly useful when measuring indicators with large small-scale variability such as turbidity and chlorophyll-a. Additionally, the Daintree dataset shows the ability to integrate other technologies, resulting in a more comprehensive analysis, whilst sampling offshore highlights some of the analytical issues required for sampling low concentration data. RUM is a low cost, highly flexible solution that can be modified for use in any water type, on most vessels and is only limited by the available monitoring technologies.     

A geoarchaeological approach to the analysis of secondary lithic deposits

The methods and techniques presented provide a means for evaluating raw material characteristics in those situations where secondary deposits of lithic materials were exploited for stone tool production. Those aspects of secondary deposits measured or estimated include size, form, roundness, crystallinity, homogeneity, and raw material frequency. A comparison and discussion of two sampled areas in eastern New Mexico demonstrate how these procedures can be used to elucidate meaningful archaeological information. © 1993 John Wiley & Sons, Inc.     

Estimating Small-Area Populations by Age and Sex Using Spatial Interpolation and Statistical Inference Methods

The objective of this research is to compute population estimates by age and sex for small areas whose boundaries are different from those for which the population counts were made. In our approach, population surfaces and age‐sex proportion surfaces are separately estimated. Age‐sex population estimates for small areas and their confidence intervals are then computed using a binomial model with the two surfaces as inputs. The approach was implemented for Iowa using a 90 m resolution population grid (LandScan USA) and U.S. Census 2000 population. Three spatial interpolation methods, the areal weighting (AW) method, the ordinary kriging (OK) method, and a modification of the pycnophylactic method, were used on Census Tract populations to estimate the age‐sex proportion surfaces. To verify the model, age‐sex population estimates were computed for paired Block Groups that straddled Census Tracts and therefore were spatially misaligned with them. The pycnophylactic method and the OK method were more accurate than the AW method. The approach is general and can be used to estimate subgroup‐count types of variables from information in existing administrative areas for custom‐defined areas used as the spatial basis of support in other applications.     

Three-dimensional carbon dioxide-induced strain distribution within a confined bituminous coal

Sequestration of carbon dioxide in unmineable coal seams is an option to reduce carbon dioxide emissions. It is well known that the interaction of carbon dioxide with unconfined coal induces swelling. This paper contributes three-dimensional strain distribution in confined coal at microstructural level using high-resolution X-ray computerized tomography data and image analysis. Swelling and compression/compaction of regions in the coal matrix occurs with CO₂ uptake. Normal strain varies between ? 1.15% and 0.93%, ? 3.11% and 0.94%, ? 0.43% and 0.30% along x, y and z axes respectively. Volumetric strain varies between ? 4.25% and 1.25%. The positive strains reported are consistent with typical range for unconstrained swelling. However, the average volumetric strains value (? 0.34%) reflect overall volume reduction. Overall swelling is apparently influenced by the confining stresses. The magnitudes of normal strains are heterogeneous and anisotropic. The swelling vs. compression/compaction observed after CO₂ uptake is localized and likely lithotype dependant.     

Mapping the Internet using GIS: The death of distance hypothesis revisited

This paper revisits the death of distance hypothesis. To explore the role of distance in the information age, three methods – web scan, hyperlink, and trace-route – are used to map the Internet for the US educational network. Statistical analysis is conducted to evaluate whether physical distance has any impact on the Internet information access. The cartographic and statistical results indicate that geography in general and distance in particular are still important factors in shaping the spatial pattern of Internet activities. For the most popular fifty-three US educational web sites, the physical distance within one thousand miles has positive effects on Internet access while access to international hosts heavily depends on the response time, link speed and other Internet infrastructures and interconnections such as the availability of domain name servers, network access points, backbones, etc. Implications of absolute, relative, and virtual distance in mapping the Internet are discussed. It is concluded that the death of distance hypothesis is premature, even misguided in most cases.