Design and construction of cage environments for air ion and electric field research

This report describes the design and construction of cage environments suitable for chronic exposures of large groups of mice to air ions and electric fields. These environments provide defined and reproducible ion densities, ion flux, DC electric fields, sound levels, air temperature and air quality. When used during a 2 year study, these cage environments served as a durable and reliable continuous exposure system. Three environmental chambers (cubicles) housed a total of 12 cages and provided control of air temperature, air purity and lighting. Exposure cages had grounded metal exterior walls, a plexiglass door and interior walls lined with formica. An internal isolated field plate supplemented with guard wires, energized with ca 1000 VDC, created about a 2 kV/m electric field at the grounded cage floor. Air ions resulted from the beta emission of sealed tritium foils mounted on the field plate. Cages provided high ion (1.3×10⁵ ions/cc), low ion (1.6×10³ ions/cc) and field only (ion depleted < 50 ions/cc) conditions for both polarities with similar electric fields in ionized and field only cages. Detailed mapping of the floor level ion flux using 100 cm² flat probes gave average fluxes of 880 fA cm^–2 in high ion cages and 10 fA cm^–2 in low ion cages. Whole body currents measured using live anesthethized mice in high ion cages averaged 104±63 pA. Both ion flux and whole body currents remained constant over time, indicating no charge accumulation on body fur or cage wall surfaces in this exposure system.     

Long-term biological effects of air ions and D.C. electric fields on Namru mice: First year report

This report describes for the first time the effects of long-term continuous exposures of animals to small air ions and D.C. electric fields. In this study we exposed 200 female NAMRU mice (25/cage) to the following conditions: ± high ions (2×10⁵/cm³), ± low ions (2×10³/cm³), ± field only and ground (ion depleted, no field). Specially designed cages provided a defined D.C. field of about 2 kV/meter in ionized environments, with somewhat lower values in the field only cages. Detailed mapping of ion flux originating from a tritium foil generating system (multiple sources in an overhead plate) indicated a well defined, but heterogenous pattern with eight peak areas. Using a 100 cm² probe, ion flux values ranged from 10^–12–10^–14 A/cm², with an average flux of 8.7±6.8×10^–13 A/cm² in high negative ion cages, with good reproducibility between cages.Measurements of serum glucose, cholesterol, and urea nitrogen (samples taken every three months) showed a number of small but consistent and statistically significant differences between animals maintained in different environments during the first year of exposure. Serum globulin and whole blood serotonin, however, did not show any significant environmental effects. Interestingly, pairwise comparisons between high negative and low negative ion conditions, or between high positive and low positive ion conditions, or between the two ground conditions, revealed no significant differences between cages. This argues for a similarity of environmental responses for the mice maintained in each of the compared conditions.The results of a multiple classification analysis for the entire first year showed a preponderence of effects for the ionized cages, although other conditions also had highly significant differences as compared to the grand mean value. While this study has shown effects of only small magnitude (compared to normal physiological variations) in the female NAMRU mice studied here, the significance of these results strongly validates the precept of long-term air ion effects in animals. Given the known variability of different species and strains, future studies will have to determine the actual range of responsiveness of animals exposed on a long-term basis to defined air ion and electromagnetic environments.Deceased December 8, 1982.     

Effects of pulsed electric fields on mouse spleen lymphocytes in vitro

The effects of pulsed electric fields on cell membranes were investigated. In vitro exposure of mouse splenocytes to a single high-voltage pulse resulted in an increase in membrane permeability that was dependent on both the electric field strength and the pulse duration. Exposure to a 2 μs, 3.0 kV/cm pulse resulted in the induction of a 1.26 V transmembrane potential, and elicited a 50% loss of intracellular K⁺. These results are in agreement with previous studies of the effects of pulsed electric fields on erythrocytes and microorganisms. The effect of pulsed electric fields on the functional integrity of lymphocytes was i vestigated by measuring [³H]thymidine incorporation by cells cultured in the presence and absence of various mitogens following exposure to an electrical pulse. No statistically significant effects on the response of mouse spleen lymphocytes to concanavalin A, phytohemagglutinin or lipopolysaccharide were observed following exposure to 2 μs electric pulses at amplitudes of up to 3.5 kV/cm. Exposure to a single 10 μs pulse of 2.4–3.5 kV/cm produced a statistically significant reduction in the response of lymphocytes to lipopolysaccharide stimulation that was attributed to cell death.     

Enhancement of evaporation rates from thin layers of liquids exposed to air ions

A beta-ray gauge system was used to study evaporation rates and drying times of liquids exposed to relatively high fluxes of air ions of either polarity produced by a corona discharge. Evaporation rates from thin layers of water, ethyl alcohol, and carbon tetrachloride increased considerably when exposed to air ions, compared to untreated liquids under constant environmental conditions. Drying times of liquid layers exposed to air ions were shortened by a factor of at least two over liquids that had not been exposed to ions. The drying time of a liquid layer was found to increase with the decrease of ion fluxes at the liquid surface. Threshold values of 1.9×10¹¹ positive ions and 2.7×10¹¹ negative ions cm^–2 s^–1 were established below which no increase in the evaporation rates were observed for ethyl alcohol and carbon tetrachloride. The evaporation rate of water at these same ion fluxes was significantly higher than that of the control. The present experiments indicate that a stream of air ions could play a major role in the observed enhancement of evaporation rates.     

The effect of air ions on bacterial and viral pneumonia in mice

Ambient air untreated for removal of ordinary pollutants and ionized with tritium powered generators to contain 1–2 × 10⁵ small positive ions/cm³ accelerated the rate of death of mice challenged intranasally with measured doses of KLEBSIELLA PNEUMONIAE or of the PR8 strain of influenza virus. The differences between the cumulative mortality rates of controls and ion-treated animals were significant (p < 0.05 to p < 0.001) for several days of the period of observation. Exposure of infected mice to an electrical field of the same strength as that used for ion-treated mice showed no statistically significant field effect. Repetition of the influenza virus experiments using pollutant-free air and ion densities averaging 4.1 × 10⁵ small positive ions/cm³ produced essentially the same results. The observation that high concentrations of positive ions accelerate the rate of death in pulmonary infections with KLEBSIELLA PNEUMONIAE and with influenza virus conforms to the pattern of earlier work with COCCIDIOIDES IMMITIS.

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Zusammenfassung Ungereinigte Umgebungsluft mit 1–2 × 10⁵ kleinen positiven Ionen/cm³ nach Ionisation mit Tritiumbetriebenen Generatoren beschleunigte die Todesrate von Mäusen, die intranasal mit bekannten Mengen KLEBSIELLA PNEUMONIAE und PR8 Influenza Virus okuliert worden waren. Die Unterschiede zwischen den Kontrolltieren und den ionenbehandelten Tieren waren an mehreren Beobachtungstagen signifikant (p < 0,05 bis p < 0,001). Die Exponierung der infizierten Tiere in einem elektrischen Feld der gleichen Stärke, wie für die ionenbehandelten Tiere verwendet wurde, ergab keine statistischen Unterschiede. Die Wiederholung der Versuche mit Influenza Virus in reiner Luft mit 4,1 × 10⁵ kleinen positiven Ionen/cm³ ergab die gleichen Ergebnisse.

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Resume De l'air non purifié additionné de 1–2 × 10⁵ petits ions positifs/cm³ — ions provenant de générateurs au Trititium — a augmenté le taux de décès de souris qu'on avait au préalable infectées par le nez de quantités déterminées de KLEBSIELLA PNEUMONIAE et de virus d'influenza PR8. La différence du taux cumulatif de mortalité entre des animaux traités avec cet air ionisé et des témoins a été significative pour chacun des jours de la période d'essais (p < 0,05 à p < 0,001). L'exposition de souris infectées à un champ électrique de même intensité que celui utilisé pour les animaux traités n'a pas présenté d'effets significatifs. La répétition de l'essai avec le virus de l'influenza, mais en utilisant de l'air libre de tout polluant et une densité d'ions moyenne de 4,1 × 10⁵ petits ions positifs/cm³ a conduit à des résultats similaires. La constatation que de hautes concentrations en ions positifs augmente le taux de décès dûs à des infections pulmonaires avec KLEBSIELLA PNEUMONIAE et avec le virus de l'influenza vient confirmer le résultat d'un essai antérieur pratiqué avec COCCIDIOIDES IMMITIS.

     

Effects of atmospheric small negative ions on the oxygen consumption of mouse liver cells

The effects of small negative air ions on the oxygen uptake of isolated mouse liver cells were studied by exposing the liver cells to varying ion concentrations. For concentrations of the order of 1–2 × 10⁵ ions/cm³, the oxygen uptake was always higher than in the normal atmospheric conditions of 3–8 × 10²/ions/cm³. For intermediate concentrations varying effects of activation and inhibition were observed. A statistical analysis showed that the oxygen uptake increased by approximately 14% when liver cells were exposed to ion concentrations of values 1–9 times the normal, by approximately 9% when exposed to 10–99 times the normal, and by approximately 38% when exposed to 100–999 times the normal. The significance and possible implications of the results are discussed.     

Long-term biological effects of air ions and D.C. electric fields on Namru mice: Second year report

This report describes the second year of long-term continuous exposures of female NAMRU mice to small air ions and D.C. electric fields in the following conditions: ± high ions ((2×10⁵/cm³), ± low ions (2×10³/cm³), ± field (2 kV/m) only and ground (ion depleted, no field). Using an isolated anesthesized mouse, whole body ion flux values averaged 1.04±0.63×10^–10 A in high ion cages for different positions on the cage floor, with about a hundred-fold reduction for low ion cages.During the second year (sample periods 5–8) of exposure serum chemistry variability increased, due to increased pathology and decreased numbers of animals as our experimental population died off. The fifth sample period yielded results consistent with those seen earlier, but later sample periods had many fewer significant differences between cages than did those of the first year. Nevertheless, MCA statistics for serum glucose for the second year found a pattern remarkably similar to the first, with the low ion cages (LN and LP) having the lowest levels. MCA statistics for both years emphasized this possible window effect of low level ionized conditions. Also, a comparison between the combined values for ionized (HN, LN, HP and LP) and ion depleted cages (NF, PF, G₁ and G₂) showed a highly significant difference (p<10^–6) for serum glucose for both years of exposure, with lower glucose values seen for animals in the ionized cages overall. Animals of all conditions also showed a highly significant decrease in serum glucose with age.Comparison of mice in ionized cages vs. the non-ionized cages also resulted in a significant difference (p<.013) for survival characteristics between groups, with ion exposed animals having a shorter lifespan. These statistics argue strongly for significant effects of long-term exposure of NAMRU mice to the ionized environment.     

Natural Electrotransformation of Lightning-Competent Pseudomonas sp. Strain N3 in Artificial Soil Microcosms

The lightning-competent Pseudomonas sp. strain N3, recently isolated from soil, has been used to study the extent of natural electrotransformation (NET) or lightning transformation as a horizontal gene transfer mechanism in soil. The variation of electrical fields applied to the soil with a laboratory-scale lightning system provides an estimate of the volume of soil affected by NET. Based on the range of the electric field that induces NET of Pseudomonas strain N3, the volume of soil, where NET could occur, ranges from 2 to 950 m³ per lightning strike. The influence of DNA parameters (amount, size, and purity) and DNA soil residence time were also investigated. NET frequencies (electrotransformants/recipient cells) ranged from 10⁻⁸ for cell lysate after 1 day of residence in soil to 4 × 10⁻⁷ with a purified plasmid added immediately before the lightning. The electrical field gradient (in kilovolts per cm) also played a role as NET frequencies ranging from 1 × 10⁻⁵ at 2.3 kV/cm to 1.7 × 10⁻⁴ at 6.5 kV/cm.     

The influence of flow rate and the composition of supplied CO2/air mixtures on discontinuous growth of Tetraselmis sp.

Summary This paper studies the influence of the flow rate of gaseous mixtures on the kinetics of growth and the fatty acid composition of Tetraselmis sp. at CO₂/air ratios of 3 × 10^–4 and 2 × 10^–5. The specific growth rate rises with increased flow rate up to values of approximately 0.086 h^–1 and 0.063 h^–1 at CO₂/air ratios of 3 × 10^–4 and 2 × 10^–5 respectively, when the flow rate is approximately 3 v/v per minute. At higher flow rates, the specific growth rate decreases. The polyunsaturated fatty acid content decreases slightly as the gaseous mixture flow rate increases, whereby the ratio 3/6 remains between 2 and 3, indicating good nutritional values. Offprint requests to: E. Molina     

Electrotaxis of zoospores of Phytophthora palmivora at physiologically relevant field strengths

Plant roots generate electrical fields in the rhizosphere as a consequence of their ion transport activities. We show here that zoospores of the plant pathogen Phytophthora palmivora exhibit anodal electrotaxis in electrical fields ≥0.5 V m⁻¹ comparable in size to the physiological fields around roots. An experimental protocol for applying weak electrical fields and quantifying electrotaxis is described. In this system, zoospore suspensions are isolated from the electrodes and their products using agarose bridges. Therefore, electrotaxis was not due to movement or trapping of zoospores in chemical, oxygen, pH or inhibitor gradients established by electrolysis. The electrophoretic and electroosmotic mobilities of encysted zoospores were measured. These forces did not influence the distribution of zoospores in electrotactic experiments at physiological field strengths. The electrotactic response saturated at fields above 10 V m⁻¹ was inhibited in media of osmotic strength below 400 Osmol m⁻³, was maximal at pH 7.5 and increased at high zoospore densities. These data suggest that electrotaxis may be a useful adjunct to chemotaxis in root targeting by zoospores.     

The effect of externally applied electrostatic fields,microwave radiation and electric currents on plants and other organisms,with special reference to weed control

A wide-ranging review is presented of the effects of various forms of externally applied electrical energy upon plants and other organisms. Although investigations involving both small and large amounts of energy directed at the targets are considered, a particular emphasis of this review is the feasibility of each type of electrical stimulation for weed control. Electrostatic fields ranging from 100 V m^?1 to 800 kV m^?1 have been applied to plants under laboratory conditions and in field trials since the 1880’s. Some beneficial effects have been reported (e.g. increase in yield from both cereal and vegetable crops), but the results have been erratic and the electrical conditions leading to definite benefits on a large scale could not be confidently predicted from early studies. High electric fields are reported to damage plants if currents greater than 10^?6 A are induced to flow through leaves causing corona discharges from the tips. The nature of the damage and the effects on metabolic processes are discussed. The results from experiments on the growth of plants in which the density and charge of air ions have been varied are also reviewed. The effects of microwave radiation (mostly 2450 MHz) upon seeds, plants and other organisms in soil are discussed. These effects depend upon the power density of the radiation and the electrical properties of the targets. Factors such as size of seeds and plants, shape and moisture content are important, as are the properties of the soil irradiated (notably water content). Although microwaves can be effective in killing plants and also seeds that are buried several centimeters deep in soil, high power equipment is required and treatment times are long e.g. a 60 kW machine could take up to 92.6 hours per hectare. Other experiments reported show that microwave radiation can kill nematodes in the soil and that it is also very effective in killing fungi and bacteria. The potential of the various possible uses of microwave radiation in agriculture is also described. Electric currents have been caused to flow through plants by the application of electrodes to the leaves. The effects range from nil, when 50–100 V and 1 or 2 μA are used, to very striking when voltages from 5 to 15 kV are applied causing currents of several amperes to flow and resulting in the rapid destruction of the target. Small electric currents passed through soil containing plants are reported to increase their growth. The effects of small current on the growth of individual leaves are reviewed. The use of high voltage tractor-borne equipment for weed control is also considered.     

Impact of air ions of both polarity on evaporation of certain organic and inorganic liquids

Air ions of both polarity, produced by corona electrodes, were used to evaporate to dryness liquid samples of ethyl alcohol (EA), water (W), and carbon tetrachloride (CTC). Drying times were determined with a beta-ray gauge. Ion exposed samples of EA, W, and CTC dried, respectively, 2.3, 3.2, and 5.4 times faster than the corresponding control samples when exposed simultaneously to 0.94×10¹² positive and 1.83×10¹² negative air ions cm^–2s^–1 under the same laboratory conditions. Drying by corona discharge could be explained by three different mechanisms. Electric wind caused by the ionic drag is proposed as the principal driving force for the observed enhancement of evaporation. The decrease in free energy of a dielectric in the presence of an electric field compared to its absence may have increased the escaping tendency of the molecules of the treated liquids. The turbulence in the liquids created by the rotational effect on the dielectric molecules by the electric field may also be a factor in further enhancing the mass transfer rates from the samples.     

Analysis of medullated axon exposed to radio-frequency electromagnetic radiation

A theoretical model is formulated to determine the electric field and thermal heating produced in a single neuron (medullated axon) by an incident radio-frequency electromagnetic field. The axon is assumed to be embedded in bulk nervous tissue below a planar interface between the tissue and air, with the irradiating field a plane wave normally incident from the air. Heat is removed by blood flow in the tissue. Numerical calculations for incident fields of power density 10mW?cm² and frequencies in the range 10⁸–10¹⁰ Hz show that the oscillating potential difference produced across the cellular membrane (single bilayer) of an unmyelinated axon is less than 5 μV, while that produced across the nodal membrane of a medullated axon may be 2–6 times greater, and that produced across the myelin of a medullated axon about 100 times greater. In the steady state, the temperature differences within the components of the medullated axon are found to be less than 10^-6°C and the temperature gradients less than 0.1°C?cm; these are shown to be negligible.     

60 Hz electric field parameters associated with the perturbation of a eukaryotic cell system

Summary Roots ofPisum sativum were exposed for seven days to 60 Hz electric fields ranging from 70–430 V/m in an aqueous medium whose conductivity was approximately 0.07 mho/m. (Corresponding current densities in the exposure medium associated with these field strengths ranged from 0.5–3.0 mA/cm²). Control and exposed roots were grown concomitantly in the same tank whose growth medium was continuously circulated. Temperature in the exposure medium was held at a constant 19° C. All experiments were conducted double blind. Root growth rates were determined daily. No perturbations in root growth were observed with electric fields of 150 V/m; there was a slight effect at 360 V/m, and a pronounced decrease in growth rate occurred at 430 V/m. Root conductivities are comparable to that of the growth medium. Under conditions in which growth inhibition occurs, it is estimated that induced 60 Hz cell membrane potentials would be of the order of 3–8 mV.     

Influence of temperature rise on kinetic parameters during batch propagation of Kluyveromyces fragilis in cheese whey under ambient conditions

Three 5 l working volume fermenters were used to investigate the growth of the yeast Kluyveromyces fragilis in acid cheese whey under ambient temperature in order to assess the specific growth rate and yield, the lactose and oxygen uptake rates during the various phases of batch culture, the effect of increasing temperature on the various kinetic parameters, and the need for a cooling unit for single cell production batch systems. The initial dissolved oxygen in the medium was 5.5 mg l^–1 and the pH was maintained at 4.5. The observed lag phase, specific growth rate and maximum cell number were 4 h, 0.2 h^–1 and 8.4 × 10⁸ cells ml^–1, respectively. About 99% of the lactose in cheese whey was utilized within 20 h, 85% during the exponential growth phase. The specific lactose utilization rates by K. fragilis were 0.20 × 10^–12, 1.457 × 10^–12, 0.286 × 10^–12 and 0.00 g lactose cell^–1 h^–1, for the lag, exponential, stationary and death phases, respectively. The dissolved oxygen concentration in the medium decreased as the cell number increased. The lowest oxygen concentration of 1.2 mg l^–1 was observed during the stationary phase. The volumetric oxygen transfer coefficient was 0.41 h^–1 and the specific oxygen uptake rates were 0.32 × 10^–12, 2.14 × 10^–12, 0.51 × 10^–12 and 0.003 × 10^–12 mg O₂ cell^–1 h^–1, for the lag, exponential, stationary and death phases, respectively. The maximum temperature recorded for the medium was 33 °C, indicating that a cooling unit for batch production of single cell protein at ambient temperature is not needed for this type of bioreactor. The increase in medium temperature affected the cell growth and the lactose and oxygen uptake rates.     

Pharmacological study of inhibited frog olfactory bulb glomerular input produced by a puff of air on the olfactory mucosa

The effects of applying 4-aminopyridine (10^–2 M), aminooxyacetic acid (AOAA — 10^–4–10^–3 M), -alanine (10^–3–10^–2 M), and bicuculline (10^–5, 10^–4 M) to the intact frog olfactory bulb were investigated. Having measured inhibition of orthodromic potential postsynaptic components produced either by a puff of air on the olfactory mucosa (OB input inhibition) or by single electrical stimulation of the olfactory nerve (postsynaptic inhibition) or by single electrical stimulation of the olfactory nerve (postsynaptic inhibition), it was found that 4-aminopyridine greatly intensified postsynaptic inhibition but strongly reduced that of OB input; inhibition of the latter was raised by AOAA or bicuculline and decreased by -alanine. These substances failed to exert any consistent, clear-cut effects on postsynaptic inhibition. Findings would support the hypothesis that OB input inhibition produced by a puff of air on the olfactory mucosa could occur as a result of GABA release from glial cells and subsequent binding of GABA to presynaptic GABA_B-receptors in glomeruli.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 12–20, January–February, 1987.     

Mechanism for electric breakdown in a chemically nonequilibrium system and the influence of the chain oxidation reaction in an H2-air mixture on the breakdown threshold

A mathematical model is developed and a numerical analysis is performed for an electric breakdown in a hydrogen-air mixture with a low concentration of H₂. It is shown that, at sufficiently low pressures p<10^?2 atm, a small molecular-hydrogen additive (η=5×10^?5–5×10^?3) decreases the reduced field of an electric breakdown in air by a factor of more than 2 because of the appearance of an additional detachment process associated with the chain hydrogen-oxidation reaction. Detailed calculations are performed for the mean number density of negative oxygen ions [O ₂ ^? ]=10³ cm^?3 and the hydrogen concentration in air [H₂]=0.5, 0.05, and 0.005%. It is found that, for [H₂]=0.005%, the breakdown can develop under the action of a geoelectric field of 1.3 V/cm at p?10^?4 atm.     

The basal permeability to water of human red blood cells evaluated by a nuclear magnetic resonance technique

The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes by a doping nuclear magnetic resonance technique. In order to estimate the basal permeability the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzene sulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 0.7×10^–3 cm s^–1 at 10°C, 1.2×10^–3 cm s^–1 at 15°C, 1.4×10^–3 cm s^–1 at 20°C, 1.8×10^–3 cm s^–1 at 25°C, 2.1×10^–3 cm s^–1 at 30°C and 3.5×10^–3 cm s^–1 at 37°C. The mean value of the activation energy of water diffusion (E_a,d) was 25 kJ/mol for control and 43.7 kJ/mol for PCMBS-inhibited erythrocytes. The values of P and E_a,d obtained after induction of maximal inhibition of water diffusion by PCMBS can be taken as references for the basal permeability to water of the human red blood cell membrane.     

Intracellular magnetophoresis of amyloplasts and induction of root curvature

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, (H²/2), was about 10⁹ Oe² · cm^–1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.Abbreviations HGMF high-gradient magnetic field - emu electromagnetic units - Oe Oersted We thank Dr. John Kiss, Miami University, Ohio for providing the Arabidopsis seeds. This work was supported by NASA grant NAGW-3656     

Deposition of ammonia to the forest floor under spruce and beech at the Höglwald site

Laboratory and field measurements of the flux of ammonia to forest floor canopies of spruce and beech stands at the Höglwald site in southern Bavaria are reported. Measurements were performed with an open chamber method. A linearity between ammonia concentration and ammonia flux from the atmosphere to the ground floor canopy was detected. Deposition of ammonia showed no saturation even at air concentrations up to 50 g NH₃ m^–3 air. Temperature, water content and the moss layer of the ground floor canopy had a minor influence on the deposition velocity in laboratory experiments. Deposition velocity of ammonia was higher to the spruce (1.3 cm s^–1), and limed spruce ground floor canopy (1.17 cm s^–1) compared to the beech stand (0.79 cm s^–1). In field studies, a diurnal course of the deposition velocity was detected with highest velocities in midday and minor during night times, but not in the climatic chamber. The flux of ammonia to the ground floor canopy was estimated of app. 10 kg N ha^–1 yr^–1 for the soil under spruce, 9 kg N ha^–1 yr^–1 for the limed spruce and 6 kg N ha^–1yr^–1 for the soil under beech. The fluxes are interpreted as fluxes from the atmosphere to the ground canopies of the stands.