Timescales Of Storage Research Articles

Retention and remobilization dynamics of fine particles and microorganisms in pastoral streams

Both microbial metabolism and pathogen retention and remobilization are dependent on downstream transport of fine particles, which migrate in a series of deposition and resuspension events. All fine particles, including clay minerals, particulate organic carbon, nutrients and microbes, are often considered to be transported similarly in the environment because of a lack of specific observations comparing their relative transport. We conducted a tracer injection study to compare the transport and retention of the fecal indicator bacterium Escherichia coli, synthetic inert fluorescent fine particles, and a dissolved conservative tracer. We found that the fluorescent fine particles and bacteria were transported similarly, with both having greater retention than the solute tracer. We used a stochastic model to evaluate in-stream retention and migration of the solute, fluorescent particles, and E. coli. The best-fit model parameters indicate that different stream reaches had varied retention characteristics, but always showed greater retention of fluorescent particles and E. coli compared to the solute tracer. Direct measurements within known retention areas after the injection showed that the majority of the fluorescent particles and E. coli were retained near the sediment–water interface in macrophyte stands or filtered within the top 3 cm of the streambed sediment. Both the tracer particles and E. coli were retained within these regions for multiple months following the injection experiment. The stochastic model properly captured the wide range of storage timescales and processes we observed in the stream. Our results demonstrate the importance of the streambed sediment and in-stream macrophytes as short- and long-term reservoirs for fine organic particles and microbes in streams.

Temporal scaling of groundwater discharge in dual and multicontinuum catchment models

This paper presents a multicontinuum approach to model fractal temporal scaling of catchment response in hydrological systems. The temporal scaling of discharge is quantified in frequency domain by the transfer function HðxÞ, which is defined as the ratio between the spectra of catchment response and recharge time series. The transfer function may scale with frequency x as HðxÞ x2b. While the classical linear and Dupuit models predict exponents of b52 and b51, observations indicate scalings with noninteger exponents b. Such behaviors have been described by multifractal models, which, however, often lack a relation to the medium characteristics. We revisit and extend the classical linear Dupuit aquifer models and discuss their physical meanings in the light of the resulting aquifer dynamics. On the basis of these classical models, we derive a multicontinuum approach that provides physical recharge models which are able to explain fractal behaviors with exponents 1=2 < b < 2. Furthermore, this approach allows to link the fractal dynamics of the discharge process to the physical aquifer characteristics as reflected in the distribution of storage time scales. We systematically analyze the catchment responses in the proposed multicontinuum models, and identify and quantify the time scales which characterize the dynamics of the catchment response to recharge.

Buoyancy Driven Mass Transfer in a Liquid Desiccant Storage Tank

A new concept for long-term solar thermal storage is based on the absorption properties of aqueous calcium chloride. Water, diluted and concentrated calcium chloride solutions are stored in a single tank. An immersed heat exchanger and stratification manifold are used to preserve long-term sorption storage, and to achieve thermal stratification. The feasibility of sensible heating the tank via large-scale natural convection without mixing salt solutions is demonstrated via measurements of velocity, CaCl2 mass fraction, and temperature in a 1500 l prototype tank. Experiments are conducted over a practical range of the relevant dimensionless parameters. For Rayleigh numbers from 3.4 × 108 to 5.6 × 1010 and buoyancy ratios from 0.8 to 46.2, measured Sherwood numbers are 11 ± 2 to 62 ± 9, and the tank is thermally stratified. Convective mixing between salt layers is inhibited by the presence of a steep density gradient at the interface between regions of differing mass fraction. The predicted storage time scales based on mixing via natural convection for the reported Sherwood numbers are 160–902 days.

Constraints on crystal storage timescales in mixed magmas: Uranium-series disequilibria in plagioclase from Holocene magmas at Mount Hood, Oregon

Uranium-series crystal ages, interpreted within a textural and geochemical framework, can provide insight into crystal storage timescales, especially in cases where crystals may derive from multiple sources. We report here 230Th–226Ra model ages of two distinct populations of plagioclase from low silica dacites from Mount Hood, Oregon, a volcano where previous studies show that the compositions of erupted magmas are controlled by magma recharge, mixing, and incorporation of plagioclase derived from mafic and silicic end-member magmas. We have measured trace element concentrations and 238U–230Th–226Ra disequilibria in four plagioclase size fractions from the Timberline (1500a) and Old Maid (215a) eruptive sequences. After correction for groundmass and apatite contamination, average 230Th–226Ra model ages of large (>500μm) plagioclase are >4.5ka (Timberline) and >5.5ka (Old Maid), with ages of cores that are >10ka in each case, indicating that plagioclase derived from silicic magmas crystallized thousands of years before eruptions. These model ages are longer than timescales of repose between eruptions, indicating that these crystals resided in the sub-surface over multiple eruptions, likely stored in a silicic crystal mush zone that periodically interacts with mafic recharge magmas, remobilizing a fraction of the large plagioclase crystals during each eruptive event. After correction for large plagioclase contamination, small (<500μm) plagioclase, derived from mafic magmas, have high (226Ra)/Ba relative to equilibrium with liquid proxies (groundmass and mafic inclusion), leading to 230Th–226Ra model ages that are <~3ka for Old Maid and undefined for Timberline separates. However, the preservation of significant 230Th–226Ra disequilibria require that the majority of crystals in the separate are young (<<10ka). The high (226Ra)/[Ba] could potentially be explained by rapid crystallization immediately prior to and/or during mixing events, consistent with evidence of rapid crystallization of rims. Rapid crystallization of mafic intrusions may trigger eruption at Mount Hood by producing a partially-crystalline mafic magma capable of mixing with a reheated silicic crystal mush.

Uranium-series comminution ages of continental sediments: Case study of a Pleistocene alluvial fan

Obtaining quantitative information about the timescales associated with sediment transport, storage, and deposition in continental settings is important but challenging. The uranium-series comminution age method potentially provides a universal approach for direct dating of Quaternary detrital sediments, and can also provide estimates of the sediment transport and storage timescales. (The word “comminution” means “to reduce to powder,” reflecting the start of the comminution age clock as reduction of lithic parent material below a critical grain size threshold of ∼ 50 μm.) To test the comminution age method as a means to date continental sediments, we applied the method to drill-core samples of the glacially-derived Kings River Fan alluvial deposits in central California. Sediments from the 45 m core have independently-estimated depositional ages of up to ∼ 800 ka, based on paleomagnetism and correlations to nearby dated sediments. We characterized sequentially-leached core samples (both bulk sediment and grain size separates) for U, Nd, and Sr isotopes, grain size, surface texture, and mineralogy. In accordance with the comminution age model, where 234U is partially lost from small sediment grains due to alpha recoil, we found that ( 234U/ 238U) activity ratios generally decrease with age, depth, and specific surface area, with depletions of up to 9% relative to radioactive equilibrium. The resulting calculated comminution ages are reasonable, although they do not exactly match age estimates from previous studies and also depend on assumptions about 234U loss rates. The results indicate that the method may be a significant addition to the sparse set of available tools for dating detrital continental sediments, following further refinement. Improving the accuracy of the method requires more advanced models or measurements for both the recoil loss factor f α and weathering effects. We discuss several independent methods for obtaining f α on individual samples that may be useful for future studies.

226Ra/230Th excess generated in the lower crust: Implications for magma transport and storage time scales: Comment and Reply: COMMENT

[Dufek and Cooper (2005][1]; hereafter DC) present an interesting and provocative paper on the origins of 226Ra excess in arc lavas. They develop an incongruent continuous melting model to argue that 226Ra excess can be created by partial melting in the lower crust. However, despite the novelty of

226Ra/230Th excess generated in the lower crust: Implications for magma transport and storage time scales: Comment and Reply: REPLY

We welcome the comments by Berlo et al. (hereafter BTBH) and thank them for the opportunity to further discuss lower crustal melting processes in arc settings. Our intention in [Dufek and Cooper (2005)][1] was not to explain the U-series disequilibria in all arc magmas through a single model.

226Ra/230Th excess generated in the lower crust: Implications for magma transport and storage time scales

Excesses of 226 Ra in arc magmas have been interpreted as resulting from flux melting of the mantle above subducting slabs, followed by fast ascent rates of magma from slab to surface (up to 1000 m/yr). However, we demonstrate that incongruent melting of the lower crust could either maintain or augment mantle-derived 226 Ra excesses, and so reduce inferred vertical transport rates. We developed an incongruent, continuous melting model, and both the incongruent melting reaction and ingrowth effects contribute to the 226 Ra excess. In particular, we found that dehydration melting of amphibolite can produce modeled 226 Ra excesses greater than 300%. Mixtures of such amphibolite dehydration melts with mantle melts will likely retain a 238 U excess (subducted slab) signature. This amphibolite dehydration melting process will also produce elevated ratios of light rare earth elements to heavy rare earth elements, similar to those observed in several arc settings, which may distinguish these magmas from those with 226 Ra excesses produced by slab dewatering alone.

Coarse sediment connectivity in river channel systems: a conceptual framework and methodology

Identification of coarse sediment connectivity down river-channel systems is important for understanding the linkages between river reaches, the influence of sediment sources on channel morphology and the mechanisms and liability to propagation of morphological change. A conceptual framework is developed in which several types and degrees of connectivity are proposed. It is hypothesised that sediment connectivity varies with sediment sources and with stream competence to transport the coarse fractions. A method of identifying the status of reaches is developed, based on field mapping of morphology and sedimentology. The analysis is exemplified by two channels: one an ephemeral channel in SE Spain; the other a perennial channel in NW England. Questions arise over whether reaches that lack channel stores transfer coarse sediment. Three scenarios are suggested: (1) lack of flux due to lack of competence of the reach; (2) flushing through of sediment due to high competence; and (3) potential transport of coarse sediment but exhaustion or lack of availability. Changes in connectivity will take place over different time scales depending on the nature of exchange and time scales of storage. Short-term variations in connectivity can be identified by repeated mapping.

Rational design of stable lyophilized protein formulations: theory and practice.

For ease of preparation and cost containment by the manufacturer, and ease of handling by the end user, an aqueous therapeutic protein formulation usually is preferred. However, with many proteins it is not possible—especially considering the time constraints for product development—to develop sufficiently stable aqueous formulations. Unacceptable denaturation and aggregation can be induced readily by the numerous stresses to which a protein in aqueous solution is sensitive; e.g., heating, agitation, freezing, pH changes, and exposure to interfaces or denaturants (Arakawa et al., 1993; Cleland et al., 1993; Brange, 2000; Bummer and Koppenol, 2000). Furthermore, even under conditions that thermodynamically greatly favor the native state of proteins, aggregation can arise during months of storage in aqueous solution (e.g., Gu et al., 1991; Arakawa et al., 1993; Chen et al., 1994; Chen et al., 1994; Chang et al., 1996a). In addition, several chemical degradation pathways (e.g., hydrolysis and deamidation) are mediated by water. In aqueous formulations, the rates of these and other (e.g., oxidation) chemical degradation reactions can be unacceptably rapid on the time scale of storage (e.g., 18–24 months) for pharmaceutical products (Manning et al., 1989; Cleland et al., 1993; Goolcharran et al., 2000; Bummer and Koppenol, 2000).

Source-to-sink sediment transfers, environmental engineering and hazard mitigation in the steep Var River catchment, French Riviera, southeastern France

Steep coastal margins are potentially subject to mass wasting processes involving notable landslide activity and sediment evacuation downstream by steep-gradient streams. Sediment transfer from short source-to-sink segments, coupled with mountain hydrological regimes, regulate patterns of river channel aggradation and coastal sediment supply in such geomorphic settings. On the steep French Riviera margin, sediment transfers from existing landslides or from various minor mass wasting processes to stream channels may result following bursts of heavy, concentrated rainfall. High-magnitude flooding and massive sediment transport downstream are generally related to unpredictable extreme rainfalls. Both mass movements and channel sediment storage pose serious hazards to downvalley settlements and infrastructure. A consideration of channel sediment storage patterns in the Var River catchment, the most important catchment in this area, highlights two important shortcomings relative to environmental engineering and hazard mitigation practices. In the first place, the appreciation of geomorphic processes is rather poor. This is illustrated by the undersized nature of engineering works constructed to mitigate hazards in the upstream bedload-dominated channels, and by the unforeseen effects that ten rock dams, constructed in the early 1970s, have had on downstream and coastal sediment storage and on sediment dispersal patterns and, consequently, valley flooding. Secondly, planners and environmental engineers have lacked foresight in valley and coastal management issues on this steep setting, notably as regards the reclaimed areas of the lower Var channel and delta liable to flooding. Urbanization and transport and environmental engineering works have progressively affected patterns of storage and transport of fine-grained sediments in the lower Var channel and delta. Meanwhile the problems raised by these changes have not been adequately addressed in terms of scientific research. A necessary future step in bettering the engineering solutions implemented to contain natural hazards or to harness water and sediment resources is that of fine-scale analysis of source-to-sink sediment transfer processes, of sediment budgets, of time-scales of storage in stream channels, and, finally, of high-magnitude hydrometeorological forcing events in this area. The way all these aspects have been modulated by engineering practices and socioeconomic development should also be an important part of such an analysis.

The role and economics of different types of energy storage

Abstract The value of heat storage for space heating systems ranging in size from individual multi-residential buildings to large district heating systems is examined for various time scales of storage—daily, intermediate and seasonal—and for various types of base-load plants for charging the stores. The cost of different types of storage—steel vessels, earth pits, rock caverns, clay stores, drilled rock stores and aquifers—are examined for built, tendered and designed projects, and are expressed as simplified cost equations. A comparison between the value and cost storage is used to discuss which types of stores are best suited for different tasks. Payback time and net savings achievable for various applications are derived. Payback times between less than two years and seven years are often attainable where conditions are suitable. While the numerical results are evaluated for Swedish conditions, comments on applicability elsewhere are included.