Flow-through Apparatus Research Articles

THE EFFECT OF TEMPERATURE AND INITIAL SOIL MOISTURE CONENT ON THE VOLATILIZATION OF AMMONIA FROM SURFACE-APPLIED UREA

Through both laboratory and field experiments, we studied the effects of soil moisture content on ammonia (NH3) volatilization from urea, surface-applied to bare Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf). In the laboratory trial, urea fertilizer treatments were applied to cylindrical cores of soil in a flow-through apparatus. Volatilized NH3 was measured by passing humid air through the head space and into boric acid traps for 12 d. Total loss from urea on soil with 0.15 kg kg−1 moisture content was 30.7% and on soil with 0.22 kg kg−1 moisture content, 18.3%. Nitrogen-15-enriched urea was applied to the surface of soils at 0.15 and 0.22 kg kg−1 moisture content in confined cylindrical microplots in a field site in May and July 1985. Soil in the microplots dried during the 14-d trials, because the site was covered during periods of rainfall. Samples were analyzed 0, 3, 7, and 14 d after urea after urea application. The mean air temperature was 15.0°C in May and 20.5°C in July. After 14 d, 15N recovery from 0.22 kg kg−1 moisture soil was 71.9% in May and 60.0% in July. Recovery from 0.15 kg kg−1 moisture soil was 95.5% in May and 84.9% in July. We concluded that under drying conditions greater volatilization occurs in soil with a greater initial moisture content, but when soil moisture conditions remain essentially constant, as occurred in the laboratory experiment, there is less volatilization from the soil with the greater moisture content. Also, there are greater NH3 volatilization losses at higher temperatures, given adequate moisture to ensure complete and rapid urea hydrolysis.

The Development and Use of a Flow-through Apparatus for Measuring Nitrogenase Activity and Photosynthesis in Field Crops

The Development and Use of a Flow-through Apparatus for Measuring Nitrogenase Activity and Photosynthesis in Field Crops

The complexity of mineral dissolution as viewed by high resolution scanning Auger microscopy: Labradorite under hydrothermal conditions

The dissolution of labradorite under hydrothermal conditions has been studied by exposing a packed core of fine-grained labradorite powder to deionized water at 300°C and 300 bars for 57 days using a single-pass flowthrough apparatus. The principal methods used for characterizing the labradorite dissolution were high lateral resolution scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), and measurement of the exit solution chemistry. Under these hydrothermal conditions, boehmite and halloysite precipitate throughout the core and the labradorite powder undergoes extensive dissolution. The reacted labradorite surfaces are incongruently modified to levels as deep as 20 Å (for Al and Si) to 30 Å (for Na and Ca), although the distribution of elements within this depth or deeper is not yet known. The modified surface chemistry not only changes systematically down the length of the core, but is also locally variable. Generally, and relative to the starting composition, the reacted surfaces are enriched in Al and depleted in Na, Ca, and Si, and the Ca surface concentration decreases with distance from the inlet. Locally, some portions of the reacted labradorite surfaces have had Ca (and presumably Na) almost entirely removed. The dissolution mechanism of labradorite under hydrothermal conditions as revealed by SAM is highly complex, and the variability in surface chemistry is probably controlled by the local density and distribution of microcracks and crystal defects, the starting morphology of each labradorite surface, and the local flow patterns of reacting solution over that surface. Our results are contrary to previous XPS studies of dissolving feldspars (at or near room temperature) which do not report dramatic changes in near-surface chemistries. Part of the difference between the XPS and Auger results may be due to the difference in the depth of analysis associated with the characteristic electrons utilized by the two techniques.

The dissolution kinetics of quartz as a function of pH and time at 70°C

A single-pass, flow-through apparatus was used to determine the dissolution rate of quartz at 70°C as a function of pH and time. Dissolution rate data were obtained over the pH range 1.4 to 11.8 in nine separate experiments each lasting 50 days. The quartz dissolution rates were defined by the silica release rate to solution. Speciation-solubility calculations using the geochemical modeling code EQ3/6 indicate that the fluid was maintained far from equilibrium with respect to quartz and well-undersaturated with respect to all possible secondary minerals in all runs. The dissolution rates were independent of pH at values (10 −15.3 mol/cm 2 · s) consistent with the data of Rimstidt and Barnes (1980) up to approximately pH 6, but at higher pH the rates increased with increasing pH, proportional to a H + −0.5 , being almost four orders of magnitude higher at pH 11.8. The rate constants for quartz dissolution at 70°C were 10 −15.3 mol/cm 2 · s in the pH-independent region extending from acid through neutral solutions, and 10 −17.8 mol/cm 2 · s in more alkaline solutions. Etch pits were strongly developed in the runs with the more alkaline solutions (pH > 8), in which the rates were the highest. This appears consistent with a surface reaction-controlled dissolution mechanism.

The Transport and Metabolism of Urea inChara australis

The Transport and Metabolism of Urea in<i>Chara australis</i>

Sampling of airborne polycyclic aromatic hydrocarbons

Limitations of NIOSH sampling method P and CAM 183 were defined for airborne standard mixtures of polycyclic aromatic hydrocarbons (PAH) generated as vapors in a flow-through apparatus. The PAH fell into three categories: those that were too volatile to be collected by the NIOSH filtration method at normal ambient temperatures and were best sampled with Tenax or XAD-2 sorbent (i.e., indane, naphthalene, biphenyl, acenaphthene, fluorene, 9,10-dihydrophenanthrene, phenathrene, and anthracene); those that were quantitatively collected by filters, even after a brief airborne residence time (i.e., benz(a)anthracene, chrysene, benzo(a)pyrene, dibenz(a,h)anthracene, and benzo(ghi)perylene); and those that partitioned between filter and sorbent (i.e., fluoranthene and pyrene). A combination glass fiber/silver membrane filter backed by two sorbent tubes in series gave overall mean recoveries of 94-96% for the 15 PAH studied at total concentrations of, nominally, 0.2 and 0.02 mg/m/sup 3/. Individual PAH concentrations were 0.03-0.05 and 0.003-0.005 mg/m/sup 3/, respectively.

Adsorption removal of carbon dioxide from the helium coolant of high-temperature gas-cooled reactors

This paper conducts experiments on the removal of CO/sub 2/ from helium by means of a Soviet-made adsorbent under the conditions characteristic of high-temperature gas-cooled reactor cleaning systems. The adsorption of CO/sub 2/ from helium was studied under dynamic conditions with a fixed layer of adsorbent in a flow-through apparatus with an adsorber 16 mm in diameter. The analysis of the helium was carried out by means of a TVT chromatograph. In order to compare the adsorption of CO/sub 2/ on CaA zeolite under dynamic conditions from the helium stream under pressure with the equilibrium adsorption on the basis of pure CO/sub 2/, the authors determined the adsorption isotherm at 293 K by the volumetric method over a range of CO/sub 2/ equilibrium pressures from 260 to 11,970 Pa. Reducing the adsorption temperature to 273 K leads to a considerable reduction in the energy costs for regeneration, owing to the increase in adsorption and the decrease in the number of regeneration cycles; the amount of the heating gas used is reduced to less than half.

The toxicology and metabolism of chlorothalonil in fish. I. Lethal levels for Salmo gairdneri, Galaxias maculatus, G. truttaceus and G. auratus and the fate of 14C-TCIN in S. gairdneri

LC 50 values of chlorothalonil (TCIN) to Salmo gairdneri, Galaxias maculatus, G. truttaceus and G. auratus for 24, 48 and 96 h were determined using a flow-through apparatus. All values were lower than those previously reported for various fish species. The influence of decreased oxygen concentration and co-exposure of acephate on LC 50 values of TCIN to Salmo gairdneri was also investigated. Uptake of 14C-chlorothalonil in internal organs of Salmo gairdneri was measured during a 96 h exposure to 10 μg/l in water. The primary site of accumulation was the bile. Levels in all other organs were in the mg/kg range and increased with time of exposure. Protein binding was observed in the liver. Release of polar labelled metabolites was constant with time over 96 h depuration, with 0.5% being TCIN. All organ levels dropped during this time. The possible route of TCIN metabolism is discussed.

Responses to rapid temperature change in the Pacific lamprey (Lampetra tridentata)

Some aspects of the thermal biology of the Pacific lamprey (Lampetra tridentata) were studied by making rapid changes in the ambient water temperature (Ta). Calorimetric studies were conducted to determine the rate of ensuing changes in mean body temperature [Formula: see text] and various deep body temperatures. Cardiovascular–respiratory alterations were evaluated in an experimental flow-through apparatus in which Ta could be rapidly shifted while changes in ventilation frequency (fV) and heart rate (fH) were recorded. Immediately following a step increase in Ta, the change in [Formula: see text] of a 0.21-kg lamprey was 33% complete in 33 s and 67% complete in 127 s. Deep dorsal muscle temperature changed much more slowly, being 33% complete in 87 s and 67% complete in 225 s. During rapid shifts in Ta, fV and fH changed at a significantly greater rate than would be predicted taking into account the change in [Formula: see text] and the resultant Q10 effects on metabolism. This effect persisted when the [Formula: see text] of the water was held at 600 Torr (1 Torr = 133.322 Pa). A possible interpretation of the results is that lampreys, like other water-breathing vertebrates, sense alterations in peripheral temperature and utilize this information to alter the output of the ventilatory and cardiovascular systems in a way that anticipates some of the metabolic effects of temperature.

Progress in the development of artificial diets for bivalve filter feeders

Methods are described for preparing (1) carboxymethyl cellulose microgel particles, used in the delivery of high molecular weight water-soluble nutrients to aquatic filter feeders and (2) lipid-walled microcapsules for the delivery of low molecular weight water-soluble nutrients. An artificial diet was prepared which consisted of microgel particles, microcapsules, kaolin, and a freely dissolved trace-metal mixture. When the diet was continuously fed to oysters held in beakers, growth rates as high as 73% that of algal-fed controls were obtained. Much poorer growth occurred if the oysters were fed on the same diets in a flow-through apparatus. It is postulated that the better growth of oysters continuously fed on artificial diets in beakers was due to the relatively high bacterial numbers present, compared with lower numbers present in the flow-through apparatus. Bacteria could be important in the growth of oysters fed on the artificial diets by acting as a nutrient source and/or by aiding in the breakdown and digestion of the food particles.

Elements and innovations in the cultivation of red abalone Haliotis rufescens

Seven elements are described for cultivation of the red abalone, Haliotis rufescens: broodstock management; spawning induction, fertilization, and early development; larval cultivation; forage culture; settlement and early-juvenile-stage cultivation; weaning; and grow-out: Cultivation methods and equipment are described. Spawnable abalones are maintained on a year-round basis. Larvae are cultured in a flow-through apparatus that yields over 90% to the settling stage. A diatom slurry method is used to provide forage to the early benthonic and juvenile stages. Cultivation problems are described. Included are those with bacteria, Vibrio spp., and the maintenance of suitable diatom substrates for juvenile stages.

A battery-operated, continous-flow enclosure for metabolism studies in benthic communities

Community metabolism is increasingly being used as a measure of functional activity in ecological research. In order to combine the advantages of measuring metabolism in open and closed aquatic ecosystems, a battery powered, portable, in-situ, continuous flow-through apparatus was designed. A gravity generated water flow through the enclosures ensures steady flow rates and allows continuous measurements of e.g. O2, temperature and nutrients over long time-periods. The setup is suitable for experimental purposes as it is possible to manipulate the incoming water (e.g. by increasing or decreasing temperature, food, oxygen and nutrient levels) and as several enclosures containing different ecosystem components can be serially coupled in order to evaluate aspects of their interdependence and functions in the total ecosystem. The device is also suitable in bio-assay studies for on-site effluent testing and dose-response testing of toxicants. By regulating the flow rate and size of the enclosure, the setup can be easily adapted to different sizes and activities of the components studied.

Laboratory rearing of marine calanoid copepods

Cohorts of 100 newly hatched (<48 h) Pseudocalanus sp. nauplii were reared to maturity in replicate in a flow-through apparatus at 5 ° C and four phytoplankton concentrations (200, 100, 50, and 25 μg carbon · 1−1). The life stage distribution of each cohort was measured by subsampling (nauplii) and silhouette photography (copepodids) at discrete intervals throughout the experimental period to determine the effect of food concentration on cohort development. The flow-through apparatus maintained constant paniculate carbon and nitrogen concentrations during the experiments. Silhouette photography eliminates the need to sacrifice animals so that rearing at field concentrations of copepods was possible. Phytoplankton were grown in chemostats which provided a simple means of maintaining sterile cultures for extended periods and a continual source of cells of constant chemical composition. A stock culture apparatus maintained source populations of copepods with only minimal handling.

α-Amylase Secretion by Single Barley Aleurone Layers

The secretion of alpha-amylase from single isolated (Hordeum vulgare L. cv Himalaya) aleurone layers was studied in an automated flow-through apparatus. The apparatus, consisting of a modified sample analyzer linked to a chart recorder, automatically samples the flow-through medium at 1 minute intervals and assays for the presence of alpha-amylase. The release of alpha-amylase from aleurone layers begins after 5 to 6 hours of exposure to gibberellic acid and reaches a maximum rate after 10 to 12 hours. The release of alpha-amylase shows a marked dependence on Ca(2+), and in the absence of Ca(2+) it is only 20% of that in the presence of 10 millimolar Ca(2+). Withdrawal of Ca(2+) from the flow-through medium results in the immediate cessation of enzyme release and addition of Ca(2+) causes immediate resumption of the release process. The effect of Ca(2+) is concentration-dependent, being half-maximal at 1 millimolar Ca(2+) and saturated at 10 millimolar Ca(2+). Ruthenium red, which blocks Ca(2+) but not Mg(2+) efflux from barley aleurone layers, renders alpha-amylase release insensitive to Ca(2+) withdrawal. Inhibitors of respiratory metabolism cause a burst of alpha-amylase release which lasts for 0.5 to 5 hours. Following this phase of enhanced alpha-amylase release, the rate of release declines to zero. Pretreatment of aleurone layers with HCl prior to incubation in HCN also causes a burst of alpha-amylase release, indicating that the inhibitor is affecting the secretion of alpha-amylase and not its movement through the cell wall. The rapid inhibition of alpha-amylase release upon incubation of aleurone layers at low temperature (5 degrees C) or in 0.5 molar mannitol also indicates that enzyme release is dependent on a metabolically linked process and is not diffusion-limited. This conclusion is supported by cytochemical observations which show that, although the cell wall matrix of aleurone layers undergoes extensive digestion after gibberellin treatment, the innermost part of the cell wall is not degraded and could influence enzyme release.

Acute toxicity of cadmium, zinc, and cadmium-zinc mixtures to Daphnia magna.

Experiments were performed in flow-through apparatus to determine the acute toxicity of zinc, cadmium, and their mixtures toDaphnia magna in order to compare sensitivity ofDaphnia relative to that of other organisms and to determine if the metal mixture behaves differently than expected on the basis of single metal experiments. Dosage-mortality curves are derived forDaphnia populations exposed to zinc and cadmium for 36, 48, 60, 72, and 96 hr periods. Similar curves are derived forDaphnia exposed to equally potent mixtures of zinc and cadmium as calculated from initial experiments and forDaphnia exposed to equal concentration mixtures of the metals. Cadmium is more toxic than zinc, but zinc-cadmium mixtures are less toxic than expected.Daphnia magna is considerably more sensitive to these metals than are other invertebrates and vertebrates previously studied. This study demonstrates errors which can arise in attempts to set water quality criteria based upon short term studies of organisms with long life spans.

A flow-through system for field measurements of production by marine macroalgae

A continuous flow-through chamber for the in situ measurement of primary production in macrophytic algae (as exemplified by Ulva lactuca) is described. Rapid mixing occurred within the chamber independent of flow rate or amount of algal tissue, so that the “complete-mix reactor” model of sanitary engineering was closely approximated. Field experiments with the apparatus revealed a rapid response to short-term variations in production rate as well as a close correlation between production and changing light levels. The flowthrough apparatus was compared to a closed system (the traditional bell jar approach); when the water in the latter was mixed, the two methods gave similar results for incubations not longer than several hours. However, during longer incubations, the productivity in the static system was sometimes depressed, possibly due to nutrient depletion or to abnormally high levels of oxygen. Thus, the flow-through system permits reliable measurements of macroalgal production for periods of 12 h or longer.

Long-term Effects of Hydrogen Sulfide on Hexagenia limbata (Ephemeroptera) 1

Nymphs of the mayfly Hexagenia limbata (Serville) were subjected to hydrogen sulfide in test chambers with a mud substrate into which they could burrow. Acute and chronic tests were in flow-through apparatus. At 17.8–18.3°C and O 2 of 4.5–6.6, 96-h LC 50 was 0.165 mg/liter H 2 S and LC 50 at 12 days was 0.060 mg/liter H 2 S. In chronic tests running 138 days with 0.029 mg/liter H 2 S, 37% mortality occurred, and at 0.0762 mg/liter H 2 S, none survived. No subimagos emerged at concentrations of 0.0348 mg/liter H 2 S but below this level 30–70% emerged.

Chronic Toxicity of Hydrogen Sulfide to Gammarus pseudolimnaeus

Gammarus pseudolimnaeus from two trout streams were exposed to various levels of hydrogen sulfide from 0.0007 to 0.0192 mg/liter in a flow-through apparatus for periods of 65, 95, and 105 days in four tests. Results indicate that 0.002 mg/liter of H2S is the maximum safe concentration for Gammarus, but below this level there is increased reproduction or survival. Mean 96-hr LC50 for Gammarus from the same populations was 0.022 mg/liter of H2S or approximately 10 times the safe level.

Growth of a photoautotroph, Plectonema boryanum, in the dark on glucose

A system is described for culturing an obligate photoautotroph, Plectonema boryanum, on glucose in the dark. This consisted of a continuous flow-through apparatus, by means of which fresh sterile media was continually replenished. Algal cells grown in the dark on glucose are deficient in chlorophyll, but regained their chlorophyll after exposure to light and are able to grow in their usual mineral salts medium, when transferred to the light.

Growth of obligate autotrophic bacteria on glucose in a continuous flow-through apparatus.

Nitrosomonas europaea, Nitrobacter agilis, Thiobacillus denitrificans, T. neapolitanus, and T. thioparus (all obligate autotrophic bacteria) have been grown in dialysis culture, on glucose salts media, in the absence of their specific inorganic energy source. Metabolic products for N. agilis grown on nitrite salts medium were identified as keto acids. Pyruvic acid inhibited this organism at 5 x 10(-5)m. Keto acids were not inhibitory for the thiobacilli grown on thiosulfate medium. However, when T. denitrificans was grown on glucose with dialysis, addition of 5 x 10(-4)m pyruvate inhibited growth. Thus, it appears pyruvate may be inhibitory for other autotrophs, as has been reported for T. thiooxidans.