Environmental controls on long-term growth of freshwater mussels in an oligotrophic lake

2021 ◽  
Author(s):  
Vince L. Butitta ◽  
Emily H. Stanley ◽  
Andrew L. Rypel
Keyword(s):  
Freshwater Mussels ◽  
Oligotrophic Lake ◽  
Environmental Controls

Pearl Thieves and Perfect Order

2017 ◽  
Author(s):  
Jonathan Schlesinger
Keyword(s):  
Freshwater Mussels ◽  
Ecological Crisis ◽  
Local Administration ◽  
Qing Empire ◽  
Administrative Structure ◽  
Perfect Order ◽  
Tribute System

Something strange happened in Manchuria under Qing rule: its freshwater mussels disappeared. Stranger still, the Qing empire did everything in its power to preserve them: draft soldiers; fortify passes; patrol rivers; send boats and horses and silver and men. It streamlined the bureaucracy and revamped the local administration. “Nurture the mussels and let them grow,” the emperor ordered; let Manchuria have mussels. Chapter explores what happened: the collapse of the pearl fishery the attempts, in the language of the Qing court, to “nurture the mussels.” The court put its full weight behind efforts to create a long-term sustainability: it reorganized the administrative structure, empowered territorial governors, and created militarized off-limits areas. Poachers were arrested; the mussels allowed to rest. Through a detailed description of the tribute system, the ecological crisis, and the court’s response, the chapter documents how a reinvented Manchuria came to be.

Seasonal and spatial distributions of euphotic zone and long-term variations in water transparency in a clear oligotrophic Lake Fuxian, China

2018 ◽  
Vol 72 ◽  
pp. 185-197 ◽  
Author(s):  
Qichao Zhou ◽  
Yunlin Zhang ◽  
Kaidi Li ◽  
Licheng Huang ◽  
Fengle Yang ◽  
...  
Keyword(s):  
Euphotic Zone ◽  
Oligotrophic Lake ◽  
Water Transparency ◽  
Spatial Distributions ◽  
Lake Fuxian ◽  
Long Term Variations

scholarly journals Atmospheric stilling and warming air temperatures drive long‐term changes in lake stratification in a large oligotrophic lake

2020 ◽  
Author(s):  
Jonathan T. Stetler ◽  
Scott Girdner ◽  
Jeremy Mack ◽  
Luke A. Winslow ◽  
Taylor H. Leach ◽  
...  
Keyword(s):  
Oligotrophic Lake ◽  
Air Temperatures ◽  
Long Term Changes ◽  
Lake Stratification

scholarly journals Long-Term Decline in Freshwater Mussels (Bivalvia: Unionidae) of the Western Basin of Lake Erie

1991 ◽  
Vol 17 (2) ◽  
pp. 214-219 ◽  
Author(s):  
Thomas F. Nalepa ◽  
Bruce A. Manny ◽  
James C. Roth ◽  
Samuel C. Mozley ◽  
Donald W. Schloesser
Keyword(s):  
Lake Erie ◽  
Freshwater Mussels ◽  
Western Basin

scholarly journals How relevant is the deposition of mercury onto snowpacks? – Part 1: A statistical study on the impact of environmental factors

2012 ◽  
Vol 12 (19) ◽  
pp. 9221-9249 ◽  
Author(s):  
D. A. Durnford ◽  
A. P. Dastoor ◽  
A. O. Steen ◽  
T. Berg ◽  
A. Ryzhkov ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Atmospheric Stability ◽  
Atmospheric Mercury ◽  
Aquatic Life ◽  
Confidence Levels ◽  
Environmental Controls ◽  
Surface Snow ◽  
Ionic Pulse ◽  
The Impact

Abstract. A portion of the highly toxic methylmercury that bioaccumulates in aquatic life is created from mercury entering bodies of water with snowpack meltwater. To determine the importance of meltwater as a source of aquatic mercury, it is necessary to understand the environmental processes that govern the behavior of snowpack-related mercury. In this study we investigate relationships among 5 types of snowpack-related mercury observations and 20 model environmental variables. The observation types are the 24-h fractional loss of mercury from surface snow, and the concentrations of mercury in surface snow, seasonal snowpacks, the snowpack meltwater's ionic pulse, and long-term snowpack-related records. The model environmental variables include those related to atmospheric mercury, insolation, wind, atmospheric stability, snowpack physical characteristics, atmospheric pressure, and solid precipitation. Bivariate and multiple linear regressions were performed twice for each mercury observation type: once with all observations, and once excluding observations from locations where the snowpack's burden of oxidizing and stabilizing halogens is known or presumed to affect snowpack mercury. Since no observations from long-term snowpack-related records were considered affected by halogens, this group of observations was included with the sets of uninfluenced observations and was not discussed with the complete, original sets of observations. When all observations are included, only 37% of their variability can be explained, on average, with significance confidence levels averaging 81%; a separate regression model predicts each mercury observation type. Without the influence of halogens, the regression models are able to explain an average of 79% of the observations' variability with significance confidence levels averaging 97%. The snowpack-related mercury observations are most strongly controlled by the dry and wet depositions of oxidized mercury, and by precipitation. Mercury deposited through wet processes is more strongly retained by snowpacks than mercury deposited through dry processes. Revolatilization of mercury deposited through wet processes may be inhibited through burial by fresh snowfalls and/or by its more central location, compared to that of mercury deposited through dry deposition, within snowpack snow grains. The two depositions of oxidized mercury together explain 84% of the variability in observed concentrations of mercury in surface snow, 52% of the variability of observed concentrations of mercury in seasonal snowpacks and their meltwater's ionic pulse, and only 20% of the variability of observed concentrations of mercury in long-term snowpack-related records; other environmental controls seemingly gain in relevance as time passes. The concentration of mercury in long-term records is apparently primarily affected by latitude; both the primary sources of anthropogenic mercury and the strong upper-level zonal winds are located in the midlatitudes.

scholarly journals Deformation mechanisms and their microstructural indicators in the compaction of crushed salt as a geotechnical barrier

2021 ◽  
Vol 1 ◽  
pp. 131-132
Author(s):  
Kristoff Svensson ◽  
Kornelia Zemke ◽  
Ben Laurich
Keyword(s):  
Deformation Mechanisms ◽  
Dislocation Creep ◽  
Physical Processes ◽  
Environmental Controls ◽  
Porosity And Permeability ◽  
Subgrain Formation ◽  
Joint Interpretation ◽  
Early Compaction

Abstract. Following 30 years of research, it is common sense that crushed salt is the most suitable geotechnical material for encapsulating radioactive waste in a rock salt repository (e.g., Chaikowski et al., 2020). After emplacement, it provides sufficient permeability to allow outflow of unwanted canister-corrosion gases. In the long term, however, when it becomes compacted by converging cavity walls, it safely hinders any fluid flow from and to the waste. Hence, it is essential to know the evolution of (1) the material's key parameters during compaction, such as porosity and permeability, backfill resistance and viscosity; (2) the material's response to environmental controls, such as temperature, humidity, and stress; and (3) the material's long-term rheology. Here we align microstructural deformation indicators with physical processes that underlie compaction (Mills et al., 2018a). We strive to identify and – where feasible – to quantify the dominant deformation mechanisms (Blenkinsop, 2002; Jackson and Hudec, 2017). As a preliminary result, we show that the abundancy of deformation indicators increases with increasing compaction state. In early compaction, we observe more brittle mechanisms, such as grain fracturing (Fig. 1a) and cataclastic flow. At later stages, especially in the presence of moisture, plastic deformation overtakes. Therein, we observe an increased presence of indicators for pressure solution precipitation (grain boundary seams) and dislocation creep (subgrain formation, Fig. 1b), with progressing deformation. In our upcoming work, we aim at linking the observed indicators to environmental controls, such as moisture content, temperature, and strain rate by applying our approach to larger suits of samples compacted under best-known controlled conditions. Final goal is the joint interpretation with findings from in situ-compacted material (Mills et al., 2018b). Do lab tests mimic in situ processes of crushed salt compaction adequately? Can we learn how to do better by means of microstructural investigations?

scholarly journals Over 30 years of research on crushed salt as a barrier material: fundamental findings and open questions

2021 ◽  
Vol 1 ◽  
pp. 137-139
Author(s):  
Kornelia Zemke ◽  
Kristoff Svensson ◽  
Ben Laurich ◽  
Johanna Lippmann-Pipke
Keyword(s):  
Radioactive Waste ◽  
Rock Salt ◽  
Radioactive Waste Disposal ◽  
Test Series ◽  
Triaxial Tests ◽  
Barrier Material ◽  
Environmental Controls ◽  
History Of

Abstract. Repositories for high-level radioactive waste in geological formations require knowledge on thermal, mechanical and fluid transport properties of the whole repository system, including the engineered barriers and backfill materials. For about 30 years, crushed salt has been considered the most suitable geotechnical barrier material to backfill cavities and encapsulate radioactive waste in rock salt repository sites (e.g., Czaikowski et al., 2020). Over time, when the surrounding cavity walls converge by the creep of salt, it can become strongly compacted and safely encapsulates radioactive waste from any fluid flow. Hence, crushed salt has been characterized in detail for its physical material properties and its response to environmental controls (stress, temperature and moisture). This characterisation provides a basis for long-term numerical simulations (e.g., Liu et al., 2018), which verify so-called safety cases in radioactive waste disposal. Displacement-controlled oedometric compaction tests mimic the long-term in situ behaviour of crushed salt. The tests show that it can be compacted to a state comprising physical rock properties similar to natural rock salt. In general, compaction is easier with an increase in humidity and temperature (e.g., Stührenberg, 2007; Kröhn, et al., 2017). Triaxial test series address the compactions' response to differing confining pressures and help to identify generalized constitutive equations for crushed salt. Both BGR procedures, the oedometric and the triaxial compaction, are verified by the German accreditation body (DAkkS). Figure 1 illustrates the history of oedometric tests at the BGR laboratory since 1993, which examined crushed salt from various origins and differing temperature conditions. Most tests focused on material from the Asse mine, revealing the compactions' response to the materials' humidity and to brine flow. Moreover, systematic test series with synthetic grain size distributions and bentonite additives provided a basis for barrier material design. More recent tests on bedded salt formations (e.g., Teutschenthal and Sondershausen mines) allow the differentiation from characteristics from domal salt deposits (e.g. Gorleben). The current research continues the history of oedometric and triaxial tests, but has a new focus on late compaction stages with marginal remaining porosities (<5 %). The approach of systematic material characterization under best-controlled conditions essentially benefits from the international research collaboration in the KOMPASS project (Czaikowski et al., 2020). The aim of its current phase two is to synthetically generate, identify and quantify dominant grain-scale deformation processes in response to changes in environmental controls. Subsequently, these laboratory results will be embedded in numerical models on the long-term in situ rheology of crushed salt.

scholarly journals The challenge in measuring low-permeability materials: a comparison of different approaches

2021 ◽  
Vol 1 ◽  
pp. 295-297
Author(s):  
Ben Laurich
Keyword(s):  
Fluid Pressure ◽  
Low Permeability ◽  
Test Duration ◽  
Pore Waters ◽  
Advective Flow ◽  
Saturation State ◽  
Barrier Materials ◽  
Pressure Decay ◽  
Environmental Controls

Abstract. The German repository site selection procedure calls for a radioactive waste containment zone with a low-permeability host rock (kf<10-10 m s−1, StandAG §23, 5) and long-term sealing by barrier materials (EndlSiAnfV, 2020; ESK, 2019). The potential host rocks, clay and rock salt, as well as the considered barrier materials, bentonite and compacted crushed salt, show permeability in the range of kf∼10-16 m s−1 (K∼10-21 m2). These low values suggest that advective flow is as slow as diffusive mass flux. Measuring such low permeability with adequate accuracy challenges measurement setups and respective error evaluation. Methodologies. Several low-permeability measurements are carried out by transient tests, e.g. by monitoring controlled fluid pressure changes in: (1) pressure decay and (2) oscillating pulse tests. The first method (1) deviates permeability from the time needed to compensate pressure differences through the sample. The latter (2) monitors phase shift and amplitude attenuation of controlled pressure pulses passing through the sample. Any permeability measurement needs to be post-processed, e.g. for: (1) material-intrinsic controls (saturation state, storativity, the fluids' compressibility, etc.), (2) environmental controls (temperature, confining pressures, etc.) and (3) theoretical considerations (Klinkenberg correction, multi-phase wetting angles, etc.). Salts. A porosity-permeability relation was found down to K=10-19 m2 (e.g., Popp et al., 2007). Testing fluids were NaCl brine, oils, He and N2 as a fluid. As a matter of current research, a critical, low-permeability value might be associated with the so-called “percolation threshold” that defines the minimal requirements for an interconnected pore system (e.g., DAEF, 2016). Clays. A major challenge is the long duration of sample saturation (up to several months) and pressure equilibration (often days), as well as precise, temperature-compensated measuring and the determination of the samples' storativity (e.g., Winhausen et al., 2021). Testing fluids are commonly designed mixtures mimicking the rocks' pore waters. Geotechnical barrier materials. The permeability testing performed is similar to that of salt and clays mentioned above. However, both barrier materials, crushed salt and bentonite, have significant permeability early after emplacement. This is beneficial, as it allows the outflow of unwanted canister corrosion gases. Eventually, the permeability drops by orders of magnitude and the barriers become tight seals in the long-term. Here, identifying the gas entry/breakthrough pressure has been valuable (e.g., Rothfuchs et al., 2007). Figure 1 shows a preliminary sensitivity analysis as an example of pressure decay measurements. It suggests that the pressure equilibration term (c), and hence the test duration, is most sensitive to the calculation of low permeability. However, the large variation of (representative) material and environmental controls make permeability measurements complex. This workshop aims to encourage discussions on uncertainty and sensitivity of the influencing controls, such that it may lead to a “best-practice” guide for permeability measurements.

Environmental controls and long-term changes on carbon stocks under agricultural lands

2019 ◽  
Vol 186 ◽  
pp. 310-321 ◽  
Author(s):  
Paulina B. Ramírez ◽  
Francisco J. Calderón ◽  
Steven J. Fonte ◽  
Carlos A. Bonilla
Keyword(s):  
Carbon Stocks ◽  
Agricultural Lands ◽  
Environmental Controls ◽  
Long Term Changes

Long-Term Changes in Gelatinous Zooplankton in Chesapeake Bay, USA: Environmental Controls and Interspecific Interactions

2018 ◽  
Vol 42 (2) ◽  
pp. 513-527 ◽  
Author(s):  
Joshua P. Stone ◽  
Deborah K. Steinberg ◽  
Mary C. Fabrizio
Keyword(s):  
Chesapeake Bay ◽  
Interspecific Interactions ◽  
Gelatinous Zooplankton ◽  
Environmental Controls ◽  
Long Term Changes
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