Modelling of zinc accumulation in the American oyster, Crassostrea virginica (GMELIN)

A model of zinc accumulation by the American oyster, Crassostrea virginica, is developed by relating in-situ zinc body burden to time-integration of uptake. Short-term uptake rates are estimated in laboratory by introducing &\sp{lcub}65{rcub}&Zn to oysters of various weights in aquaria with salinities of 18&\perthous& and 12&\perthous&. Uptake of &\sp{lcub}65{rcub}&Zn by an oyster: (1) varies as a power function of the body weight (soft tissue dry weight) of the oyster (&dy\over{lcub}dt{rcub}& = kW&\sp{lcub}\beta{rcub}&), (2) is inversely related to the salinity of ambient water, and (3) increases linearly with ambient concentration. Zinc body burdens of oysters of various weights from oyster beds with different salinity regimes of the James River and of the Rappahannock River are measured. When the zinc body burden of oysters is fitted to a power function of body weight (y = aW&\sp{lcub}\rm b{rcub}&), the values of power, b, are 1.33, 1.30, and 1.06 for salinities of 13, 15, and 20&\perthous&, respectively, in the James River and 1.16 for a nominal salinity of 18&\perthous& in the Rappahannock River. The values of b agree with the values of &\beta& derived from the &\sp{lcub}65{rcub}&Zn uptake experiments; b = &\beta& + 1. The model is calibrated using data for Horsehead Shoals and Nansemond Ridge, two sites in the James River having average salinities roughly the same as those used in &\sp{lcub}65{rcub}&Zn laboratory studies. The model is verified by the use of data for Wreck Shoal, a mid-salinity sampling site of the James River, and the pooled data for the Rappahannock River sampling sites. The weight-specific zinc concentration of an oyster increases continuously, but rate of the increase is reduced as the oyster grows larger. Both uptake parameters, k and &\beta& vary with salinity. It is suggested that the body weight effects, and their variation with salinity, should be incorporated in the design of monitoring programs for trace metals as well as in experimental studies

Zinc distributions in sediments, the common mussel, Mytilus edulis (L.), the American oyster, Crassostrea virginica (Gmelin), and the commensal pea crab, Pinnotheres ostreum (Say)

Oysters and mussels of varying sizes and sediment samples were collected from oyster beds with different salinity regimes of three Virginian coastal plain rivers: Rappahannock River. James River. and Piankatank River. Zinc concentrations of 1) soft tissues. gut contents. and shells of the oysters. 2) soft tissues of the mussels. 3) pea crabs. and 4) sediment samples were measured with a flame atomic absorption (Flame AA) spectrophotometer. Particulate organic carbon and nitrogen concentrations ·of the sediments were measured with a carbon-nitrogen analyzer. The contribution of extraneous materials. such as gut contents. faeces. and pea crabs. to the variability in oyster metal bioconcentration measurements is examined. The effect of salinity differences on bioconcentrations and the relationships between oyster and mussel dry meat weights and body burdens and bio-concentrations also are examined. The relationships are assumed to have the form: uptake equals the product of a constant times weight raised to the power b (e.g •• a {body size}b). Values for the constants a and bare determined for each case

Experimental studies of Zinc-65 uptake rates by the American oyster, Crassostrea virginica with regard to salinity, sediment concentration, and body size

Three sets of twelve oysters from the ,James River were placed in three recirculating aquaria dosed with the radioactive tracer zinc-65. All aquaria had the same amount of river bottom sediment which was kept in suspension by the water movement caused by aeration; one aquarium had twice as much tracer as the other two. The salinity of one of the low dose aquaria and. the high dose aquarium was maintained at 18 0/00: the other low dose aquarium was maintained at 1:2 0/00. All other factors were kept constant. Sediment-water-tracer mix was added to the aquaria every 12 hours. Water samples. taken immediately before and after the additions. were filtered with 0.45 micrometer membrane filters. The suspended sediment concentrations and the radioactivities of water and filters were measured. After 108 hours. the oysters were shucked and the dry weights and the radioactivities measured. Tracer uptak1e rates were calculated and the relationship between the uptake rate and body size was determined. That relationship was assumed to have the form: uptake equals the product of a constant times weight raised ti:\u3e the power b (e.g. a x {body size)b). Values for the constants a and b were determined for each aquarium

A comparative study of dry weight measurements of oyster soft tissue

Four alternative drying methods for oyster soft tissue were compared: oven drying at 105, 100 and 80°C and freeze drying. Weights were recorded every 12 hours for 5 days, and after sample treatments were switched, every 24 hours for another 3 days. The time required for all of the oysters in a treatment to reach constant weight were 36, 36, 60, and 120 hours for the 105, 100, 80°C ovens and freeze drier respectively. Within a treatment, the time for an individual oyster to reach constant weight was not related to that weight. For oven drying, drying was rapid and complete; there was no additional loss over the remainder of the 120- hour drying period. The average ratio of wet (0-hour) to dry (120-hour) weight were 9.17 to 9.47 for oven drying but only 7.35 for freeze drying. Mter three additional days in 105°C oven, the 105, 100; 80°C oven dried, and freeze dried groups lost an additional less-than-1, 1, 1, and 8% respectively. All oven dried groups gained 1% (over the 5 day) weight in the freeze drier, while the freeze dried group lost an additional 2% in 3 days. It was concluded that the temperature, at least from 80 to 105°C, for oven drying affects final dry weights by 1% or less, but the drying times required for constant weight are different. Freeze drying was less effective than oven drying in removal of water and required more time

Gaussian time-dependent variational principle for the finite-temperature anharmonic lattice dynamics

The anharmonic lattice is a representative example of an interacting bosonic many-body system. The self-consistent harmonic approximation has proven versatile for the study of the equilibrium properties of anharmonic lattices. However, the study of dynamical properties therewithin resorts to an ansatz, whose validity has not yet been theoretically proven. Here, we apply the time-dependent variational principle, a recently emerging useful tool for studying the dynamic properties of interacting many-body systems, to the anharmonic lattice Hamiltonian at finite temperature using the Gaussian states as the variational manifold. We derive an analytic formula for the position-position correlation function and the phonon self-energy, proving the dynamical ansatz of the self-consistent harmonic approximation. We establish a fruitful connection between time-dependent variational principle and the anharmonic lattice Hamiltonian, providing insights in both fields. Our work expands the range of applicability of time-dependent variational principle to first-principles lattice Hamiltonians and lays the groundwork for the study of dynamical properties of the anharmonic lattice using a fully variational framework.Comment: v2: Added a citation to L. Monacelli and F. Mauri, "Time-Dependent Self Consistent Harmonic Approximation: Anharmonic nuclear quantum dynamics and time correlation functions," arXiv:2011.14986 and a note on i

Dissolved oxygen measurements in the Machipongo River system near Willis Wharf, Virginia

Most aquatic organisms require· oxygen to survive and consequently, the dissolved oxygen (DO) content of the water is one of the most important measures of water quality. Sources of oxygen are the atmosphere and photosynthesis. Oxygen is consumed by plants and animals during respiration and by microorganisms that decompose organic matter. The more sources and sinks of oxygen, the more difficult it is to understand and predict the oxygen dynamics of a river system. Grossly polluted systems turn out to be quite simple, because the pollutant source dominates. Natural, unimpacted systems often show a balance between a number of sources and sinks and therefore are much more complex. The rivers of the Eastern Shore of Virginia typify this latter case. The Machipongo River, including its tributary Parting Creek, drains mostly agricultural land and forest. The river has extensive fringe marshes and tidal flats which are exposed at low water. A large mechanized clam processing facility located at Willis Wharf, Virginia also discharged wastewaters to Parting Creek. The organic loadings in these wastewaters have varied over time as processing techniques and production levels changed. Mathematical models are very useful tools that allow water quality managers to predict the environmental response to various actions, such as an increase in pollutant loads when a new facility begins discharging wastewaters or a decrease in pollutant loads when treatment levels are increased. Models can be only as good as the field data upon which they are based. When a system is complex, the data set must be comprehensive, and often extensive in time, so that there is sufficient information to allow the effects of all major factors to be determined. For the Machipongo River, such a field effort would be very expensive. Consequently, studies have been more limited in scope and designed to examine one factor only, namely the effects of the clam processing wastewaters. In the spring of 1989, a field study was undertaken to see if water quality differed between Parting Creek, which received the clam wastes, and the Machipongo River, which had no comparable wastewater loading. In the fall of 1990, another study was conducted to see whether conditions had changed in response to waste load reductions at the clam processing plant. Subsequently, the clam processing plant was closed, so the waste loading to Parting Creek was eliminated. This report describes the data collected during the spring of 1992, when there was no discharge from the plant. At a later date, these data will be compared with those from prior years to determine what, if any, change in water quality has resulted from the elimination of this point source of organic wastes

Sediment processes monitoring data report for calendar year 1989

Pairs of particle interceptor traps were deployed at three depths - 3, 6, and 9 meters with deployment intervals typically lasting about two weeks. At times of deployment and retrieval, profiles of water temperature, salinity and dissolved oxygen content were made and water samples were collected at trap depths. Bottom sediments also were collected and a sub-sample of the surficial sediments taken. Water samples, bottom sediments, and the materials collected in the traps were returned to the Virginia Institute of Marine Sciences for analysis. The data collected during both 1988 and 1989 are presented in the appendices. Both 1988 and 1989 data sets have been archived in ASCII and IBM PC spreadsheet formats. Individuals desiring the data in ASCII or spreadsheet formats (Lotus or Quattro) should contact one of the authors

Factorization of the 3d superconformal index

We prove that 3d superconformal index for general =2 U(N) gauge group with fundamentals and anti-fundmentals with/without Chern-Simons terms is factorized into vortex and anti-vortex partition function. We show that for simple cases, 3d vortex partition function coincides with a suitable topological open string partition function. We provide much more elegant derivation at the index level for =2 Seiberg-like dualities of unitary gauge groups with fundamantal matters and =4 mirror symmetry1114sciescopu

General, Strong Impurity-Strength Dependence of Quasiparticle Interference

Quasiparticle interference (QPI) patterns in momentum space are often assumed to be independent of the strength of the impurity potential when compared with other quantities, such as the joint density of states. Here, using the $T$-matrix theory, we show that this assumption breaks down completely even in the simplest case of a single-site impurity on the square lattice with an $s$ orbital per site. Then, we predict from first-principles, a very rich, impurity-strength-dependent structure in the QPI pattern of TaAs, an archetype Weyl semimetal. This study thus demonstrates that the consideration of the details of the scattering impurity including the impurity strength is essential for interpreting Fourier-transform scanning tunneling spectroscopy experiments in general.Comment: main manuscript: 8 pages, 6 figures, Supplementary Information: 3 pages, 6 figure