Grain‐size variability within a mega‐scale point‐bar system,False River,Louisiana

Point bars formed by meandering river systems are an important class of sedimentary deposit and are of significant economic interest as hydrocarbon reservoirs. Standard point‐bar models of how the internal sedimentology varies are based on the structure of small‐scale systems with little information about the largest complexes and how these might differ. Here a very large point bar (>25·0 m thick and 7·5 × 13·0 km across) on the Mississippi River (USA) was examined. The lithology and grain‐size characteristics at different parts of the point bar were determined by using a combination of coring and electrical conductivity logging. The data confirm that there is a general fining up‐section along most parts of the point bar, with a well‐defined transition from massive medium‐grained sands below about 9 to 11 m depth up into interbedded silts and fine–medium sand sediment (inclined heterolithic strata). There is also a poorly defined increase in sorting quality at the transition level. Massive medium sands are especially common in the region of the channel bend apex and regions upstream of that point. Downstream of the meander apex, there is much less evidence for fining up‐section. Finer sediment accumulated more readily after the establishment of a compound bar in the later stages of construction, at the terminal apex and in the bar tail. This work implies that the best reservoir sands are likely to be located in the centre of the point bar, deposited in a simple bar system. Reservoir quality decreases towards the bar edge. The early‐stage channel plug is largely composed of coarsening‐upward cycles of silt to clay and is dominated by clay and clayey silt material with poor reservoir characteristics.     

Measurement of persistent organic pollutants (POPs) in plastic resin pellets from remote islands: toward establishment of background concentrations for International Pellet Watch

Plastic resin pellets collected from remote islands in the Pacific, Atlantic, and Indian Oceans and the Caribbean Sea were analyzed for polychlorinated biphenyls (PCBs), dichloro-diphenyltrichloroethane and its degradation products (DDTs), and hexachlorocyclohexanes (HCHs). Concentrations of PCBs (sum of 13 congeners) in the pellets were 0.1-9.9 ng/g-pellet. These were 1-3 orders of magnitude smaller than those observed in pellets from industrialized coastal shores. Concentrations of DDTs in the pellets were 0.8-4.1 ng/g-pellet. HCH concentrations were 0.6-1.7 ng/g-pellet, except for 19.3 ng/g-pellet on St. Helena, where current use of lindane is likely influence. This study provides background levels of POPs (PCBs<10 ng/g-pellet, DDTs <4 ng/g-pellet, HCHs <2 ng/g-pellet) for International Pellet Watch. Sporadic large concentrations of POPs were found in some pellet samples from remote islands and should be considered in future assessments of pollutants on plastic debris.     

First health and pollution study on harbor seals (Phoca vitulina) living in the German Elbe estuary

The Elbe is one of the major rivers releasing pollutants into the coastal areas of the German North Sea. Its estuary represents the habitat of a small population of harbor seals (Phoca vitulina). Only little is known about the health status and contamination levels of these seals. Therefore, a first-ever seal catch was organized next to the islands of Neuwerk and Scharhörn in the region of the Hamburg Wadden Sea National Park. The investigations included a broad set of health parameters and the analysis of metals and organic pollutants in blood samples. Compared to animals of other Wadden Sea areas, the seals showed higher γ-globulin levels, suggesting higher concentrations of pathogens in this near-urban area, elevated concentrations for several metals in particular for V, Sn, Pb, and Sr, and comparable ranges for chlorinated organic contaminants, except for elevated levels of hexachlorobenzene, which indicates characteristic inputs from the Elbe.     

Space–time forecasting using soft geostatistics: a case study in forecasting municipal water demand for Phoenix, Arizona

Managing environmental and social systems in the face of uncertainty requires the best possible forecasts of future conditions. We use space–time variability in historical data and projections of future population density to improve forecasting of residential water demand in the City of Phoenix, Arizona. Our future water estimates are derived using the first and second order statistical moments between a dependent variable, water use, and an independent variable, population density. The independent variable is projected at future points, and remains uncertain. We use adjusted statistical moments that cover projection errors in the independent variable, and propose a methodology to generate information-rich future estimates. These updated estimates are processed in Bayesian Maximum Entropy (BME), which produces maps of estimated water use to the year 2030. Integrating the uncertain estimates into the space–time forecasting process improves forecasting accuracy up to 43.9% over other space–time mapping methods that do not assimilate the uncertain estimates. Further validation studies reveal that BME is more accurate than co-kriging that integrates the error-free independent variable, but shows similar accuracy to kriging with measurement error that processes the uncertain estimates. Our proposed forecasting method benefits from the uncertain estimates of the future, provides up-to-date forecasts of water use, and can be adapted to other socio-economic and environmental applications.     

Seismic behaviour of timber-laced stone masonry buildings before and after interventions: shaking table tests on a two-storey masonry model

The present work focuses on the seismic behaviour of timber-laced masonry buildings with timber floors, before and after the application of intervention techniques. A two-storey building with timber ties (scale 1:2) was subjected to biaxial seismic actions. Prior to the execution of shaking table tests, the dynamic characteristics of the model were identified. The base acceleration was increased step-wise until the occurrence of significant but repairable damages. Afterwards, the masonry was strengthened by means of grouting, whereas the diaphragm action of the top floor of the building was enhanced and the model was re-tested. The tests on the timber reinforced model before strengthening show that the presence of timber ties within the masonry elements contributes to improved seismic behaviour. The performance of the model after strengthening shows that the selected intervention techniques led to a significant improvement of the seismic behaviour of the building model.     

All jobs are not created equal: Divergent indicators in the knowledge economy

Univariate indicators such as employment are often used to benchmark economic growth at the local and regional levels. However, the tremendous technological and industrial changes in the U.S. economy in the second half of the twentieth century suggest this practice may be outdated. In fact, the singular use of univariate indicators to benchmark regional development may obscure a much richer and more complex web of economic processes. Given the potential complexities associated with regional benchmarking in the current global economy, this paper will explore the numerical differences in economic performance presented by popular univariate indicators of regional growth. Results demonstrate a univariate approach to benchmarking presents an incomplete snapshot of regional performance that is incapable of capturing the multifaceted nature of economic growth in today’s global knowledge economy. Although job creation remains an important component to development efforts, many other factors should be considered in evaluations of regional performance, including the industries in which jobs are created and their associated wages.     

Retention of biosignatures and mass-independent fractionations in pyrite: Self-diffusion of sulfur

Self-diffusion of sulfur in pyrite (FeS₂) was characterized over the temperature range ∼500-725 °C (∼1 bar pressure) by immersing natural specimens in a bath of molten elemental ³⁴S and characterizing the resulting diffusive-exchange profiles by Rutherford backscattering spectroscopy (RBS). The temperature dependence of the sulfur diffusivity (D_S) conforms to D_S = D_o exp(−E_a/RT), where the pre-exponential constant (D_o) and the activation energy (E_a) are constrained as follows:

     

Comparison of Nutrient and Microbial Dynamics over a Seasonal Cycle in a Mid-Atlantic Coastal Lagoon Prone to <Emphasis Type="Italic">Aureococcus anophagefferens</Emphasis> (Brown Tide) Blooms

To determine the roles of dissolved organic matter in the onset, duration, and decline of blooms of the “brown tide” pelagophyte, Aureococcus anophagefferens, nutrient and microbial dynamics, heterotrophic and autotrophic carbon (C) and nitrogen (N) uptake, and peptide hydrolysis were compared in natural populations: (1) seasonally, among physically similar sites in a mid-Atlantic coastal lagoon, Chincoteague Bay, (2) at an individual site as a bloom initiated, developed, and declined, and (3) in whole versus size-fractionated water. Throughout the year, urea was the dominant form of N taken up at both bloom and nonbloom sites. C acquisition in the A. anophagefferens (1.2–5.0 μm) size fraction was dominated by bicarbonate uptake during bloom initiation but organic C compounds were taken up later during and after the bloom. Bacterial productivity was enhanced during and just after the bloom and bacterial abundance was four times higher at the bloom versus nonbloom site.     

Evaluation of amendments used to prevent sodification of irrigated fields

Gypsum and S are applied to soils being irrigated with Na–HCO₃ dominated coalbed natural gas (CBNG) produced water to protect soil structure and fertility. Wyoming law requires beneficial use of produced water and irrigation with CBNG produced water in the semi-arid Powder River Basin is becoming more common. Strontium isotopes were used to evaluate the effectiveness of the gypsum and S applications in preventing sodification of these irrigated soils. The isotope ratio of Sr on the cation exchange complex of irrigated soil falls between that of the gypsum amendment (0.7074) and that of local soil (0.712–0.713). Strontium isotopes indicate that, to a depth of 30 cm, as much as 50% of the Sr on the irrigated soil cation exchange sites originated from the applied gypsum amendment on a field irrigated for 3 a. This was also true to a depth of 5 cm on a field irrigated less than 1 a. Strontium isotope ratio measurements of vegetation illustrate plant utilization of Sr from gypsum amendments, thereby reinforcing the conclusions about the presence of Sr from gypsum on the soil’s exchange sites. This Sr tracing technique may be useful in a wide variety of settings where monitoring soil health is necessary, especially in settings where poor quality water is used for irrigation: a more common occurrence as demand for fresh water increases.