Fraction Of Deposition Research Articles

The influence of atmospheric transport on precipitation chemistry at two sites in the midwestern United States

Cluster analyses of two-dimensional mixed layer back trajectory data were used to determine what fraction of chemical variability in precipitation composition could be related to differences in atmospheric transport. Trajectories arriving at two different sites, Rockport, Indiana, and Gaylord, Michigan, were clustered to identify events occurring with similar transport patterns. It was found that certain transport situations resulted in significantly higher concentrations and depositions of the major ions, H +, SO 4 −, NO 3 − and NH 4 −. At Rockport, the greatest fraction of acid deposition was associated with low wind speeds. At Gaylord, transport direction played a greater role than transport speed in influencing precipitation composition. Results presented here suggest that 10%–40% of the variability in ion concentrations may be related to differences in atmospheric transport. The residual variation in concentrations was correlated with differences in the occurrence of upwind precipitation, precipitation type, and variation in precipitation amount.

Aspects of atmospheric pollutant origin and deposition revealed by multielemental observations at a rural location in eastern Canada

During autumn 1984, at a location in central Ontario, a study of the elemental composition of aerosols and precipitation was undertaken to determine the feasibility of making daily multielemental measurements on a routine basin, to probe the potential for gaining insight into pollutant origin from multielemental composition, and to estimate trace element deposition to an acid‐sensitive watershed. The concentrations of Ti, Br, Mn, In, Na, V, Al, Ca, Se, As, Sb, Pb, Fe, Mg, Cu, Zn, and Cd in aerosol and of Pb, Mg, Ca, As, Br, I, Mn, and V in precipitation were measurable routinely, using neutron activation, X ray fluorescence, and plasma emission spectroscopy. Standard high volume samplers for total aerosols below 15 μm diameter as well as dichotomous samplers and Andersen impactors for size fractionation were operated simultaneously with two wet‐only precipitation collectors. Aerosol data revealed four components: one soil (Mg‐Ti‐Al‐Ca‐Fe) and three anthropogenic (Se‐Sb‐Pb‐Cd‐Br; Mass‐Cu‐SO4=; In‐As). Ranked in order of increasing mass fraction in 2.1‐ to 10‐μm diameter particles are the elements Pb, S, Se, Br, As, Cl, Na, V, In, Cu, Mn, Al, Ba, Ti, and Ca. A comparison of air parcel origin on high‐ and low‐concentration days, using 3‐day back trajectories, revealed major source regions of SO4=, Pb, In, As, and Al. The element In is an excellent tracer of smelter emissions to the north. Although the estimated mean ratio of In/Se in smelter emissions from central Ontario is close to that used in the regional aerosol apportionment model of Rahn and Lowenthal, its variability is greater than they propose. In 21 precipitation events, strong correlations were found between H+‐SO4 =, Ca++‐Mg++, NO3−‐NH4+‐Cl−‐V, and Pb‐Br. The mass ratio of Br/Pb was higher in precipitation (0.47) than in aerosols (0.27), possibly because of precipitation scavenging of HBr gas in addition to Br in aerosols. In ascending order, the estimated dry‐deposited fraction of total deposition of Br, Pb, Mg, Mn, Ca, S, V, and As ranged from 10 to 42%.

Quantifying the relationship between atmospheric transport and the chemical composition of precipitation on Bermuda

In an effort to investigate the influence of different atmospheric flow patterns on thecomposition of precipitation on the island of Bermuda, a cluster analysis of atmospherictrajectories was performed to identify periods of similar transport. The cluster analysistechnique represents a relatively objective alternative to the more subjective method ofclassifying trajectories according to compass sector. Data were stratified into two broadseasons, defined as a warm (April-September) and a cool (October-March) season. Relative tothe cool season, significantly higher per event concentrations of non-seasalt sulfate and nitrateoccurred in the warm season on Bermuda. There was no significant difference in the per eventprecipitation amount between seasons; however, there was significantly higher per eventdeposition of warm season non-seasalt sulfate, and nitrate. Significant differences inprecipitation composition were also identified between flow patterns. It was found that thesource regions which contributed the largest fraction of hydrogen ion deposition and nonseasaltsulfate deposition on Bermuda differed by season. During the cool months, 40% of thedeposition occurred with transport from the west, off the East Coast of the US, implicatinganthropogenic sources. In the warm season, an equally large fraction of deposition wasassociated with flow from the Bahamas region, suggesting an oceanic source of biogenic sulfuras the precursor. DOI: 10.1111/j.1600-0889.1988.tb00117.x

An estimate of the importance of dry deposition as a pathway of acidic substances from the atmosphere to the biosphere in eastern Canada

The relative importance of dry and wet deposition of sulphate and nitrate over southeastern Canada is examined using daily air and precipitation chemistry observations made at 6 rural stations of the Air and Precipitation Monitoring Network (APN) during the period 1979 to 1982. Dry deposition was calculated from these air concentrations using deposition velocity information on land-use types, on atmospheric wind speed and stability and on dry deposition rates from over 80 published studies. Despite the large uncertainty in dry deposition estimates which is associated with the complexity of the process, valuable conclusions emerge. It is estimated that total annual deposition varies between 10 to 86 mmole m −2 and 13 to 62 mmole m −2 for SO = 4 and NO - 3 , respectively. To eastern Canada 22% and 30% of the total SO=4 and NO−3 deposition is dry deposited, respectively. Depending on location, the contribution of SO2 to the dry deposition of sulphur ranges from 37% to 78%. It tends to decrease with increasing distance from major sources. In eastern Canada, the best estimate of the fraction of the total dry deposition of nitrogen contributed by NO2 and HNO3 is in the range 50% to 60% and 31 % to 45%, respectively, depending on location. The uncertainty in the NO2 estimate is large, approaching a factor of 3.5. Even if PAN dry deposition velocities are equal to that of NO 2 (they are expected to be lower), the contribution of PAN to total nitrate deposition is negligibly small. Both dry and wet deposition are episodic in nature. It is estimated that the top-20% deposition events yield 47% to 70% of the total deposition. DOI: 10.1111/j.1600-0889.1988.tb00213.x

Direct measurement of dry deposition to a polyethylene bucket and various surrogate surfaces

The polyethylene bucket commonly used as a dry deposition collector was evaluated and compared to a variety of other surrogate surfaces. Since SO/sub 2/, NO/sub 2/, and HNO/sub 3/ were not collected by a dry bucket, it most likely underestimates gaseous dry deposition to many natural surfaces. Deposition was similar to buckets with high walls compared to buckets with 1-cm walls, indicating a minor influence of the walls on particle deposition. At the suburban site used for this study, dry deposition to a bucket accounted for a significant fraction of total deposition: 24% of SO/sub 4//sup 2 -/, 29% of NO/sub 3//sup -/, and over half of Ca/sup 2 +/, Mg/sup 2 +/, Na/sup +/, and K/sup +/ total deposition. The bucket was compared to seven other surrogate surfaces. It collected more dry deposited material than Teflon, foil, or coated foil surfaces. However, it generally collected less than a nylon filter, quartz-fiber filter, a glass-fiber filter, or a water surface. Deposition appeared to be strongly influenced by the affinity of the surface for gases and the retention characteristics of the surface for particles.

Atmospheric trace elements at Enewetak Atoll: 2. Transport to the ocean by wet and dry deposition

The concentrations of trace elements in precipitation and dry deposition are presented for samples collected at Enewetak Atoll (11°N, 162° E) during SEAREX experiments in 1979. The concentrations of Al, Sc, Mn, Fe, Co, and Th in rain are dominated by crustal material, and for these elements, wet deposition evidently exceeds dry deposition. For most of these elements the present rates of atmospheric deposition at Enewetak are similar to their mean rate of accumulation in sediments over the past 5–10,000 years, suggesting that the air‐to‐sea exchange of particles is closely tied to the sedimentary cycle of the mid‐Pacific. Noncrustal sources govern the concentrations of Pb, Zn, Cu, Se, and Cd in wet and dry deposition samples. Analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples, and even though these estimates do not necessarily reflect the dry deposition to the ocean surface, the results suggest that recycled sea spray often amounts to more than 50% of the total dry deposition of the enriched elements. Recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements. The net deposition rates of elements such as Cu and Zn are greater than or equal to their inputs from vertical mixing, but the net deposition of Pb clearly exceeds the input from upwelling. The current net deposition rates of the enriched elements are also similar to their rates of removal to sediments. These results indicate that air‐sea exchange processes may significantly affect the chemistry of trace metals in the open ocean.

Effect of Fractions of Fish Meal and Hepatic Lipid Deposition in Estrogenized Chicks

Three experiments were conducted for the purpose of determining the effect of feeding isoenergetic diets with and without fish meal or its fractions on hepatic lipid deposition in estrogenized chicks. The chicks were fasted for 48 hr before being fed the experimental diets and were injected with estradiol three times during the experiment. After 4 days, hepatic lipid content was determined. In the first experiment, the quantity of hepatic lipid deposited per unit of liver and per 100 g body weight was significantly less for chicks fed 10% fish meal and an ethanol extract of fish meal equivalent to 10% than for chicks fed an unsupplemented corn-soy diet. In a second experiment a significant reduction in hepatic lipids deposited per 100 g body weight was observed with 10% fish meal but only a numerical reduction with ethanol extracts of fish meal equivalent to 10 or 20% and the ash of ethanol extract equivalent to 20%. In a third experiment a highly significant reduction in hepatic lipid deposition was observed in birds refed a diet containing fish meal, alfalfa, and torula yeast but feeding this before the starvation-refeeding period did not affect liver lipids. These results show that fish meal contains hepatic lipid lowering activity in refed estrogenized chicks and suggest that the activity may be extracted with ethanol.

Inertia effect on deposition of charged particles in a parallel-plate channel

The effect of inertia forces on the deposition of highly charged fine particles of sizes less than 20 μm in a parallel-plate channel has been analyzed numerically for uniform and fully-developed flows. The deposition is primarily due to space charge alone and the image and gravity forces are not included in the analysis. A charge—inertia parameter n (ranging from 0 to 1) was defined to characterize the flow deposition phenomena. It was found that for n less than 0.1 the effect of inertia forces may be neglected and that the fraction of deposition near the entrance of the channel deviates substantially from the result neglecting the inertia effect.

Distribution of polymeric plutonium injected intravenously with different amounts in mice.

Tissue distribution of intravenously injected polymeric plutonium in mice was studied by liquid scintillation counting. The purpose of this study was to know the effect of plutonium administered at different dose levels on its distribution to the tissues. The fraction of deposition and average dose rate to the highly radiosensitive tissues such as the bone marrow and testes were also of our concern.The polymeric plutonium prepared in this institute was demonstrated to have colloidal properties by showing high deposition in the liver and spleen for a long time. Percent uptakes of plutonium in the main tissues except in the kidneys were not influenced by the three different doses from 5μCi/kg to 15μCi/kg body weight of 239Pu. At 28 days after injection, femoral bone, femoral marrow and testes contained 1.23, 0.18 and 0.063 percent of the injected doses, respectively. At 56 days, the uptakes of the plutonium in the same three tissues were 1.23, 0.17 and 0.057 percent respectively. Average dose rates to the liver, lungs, kidneys, testes and femoral bone were proportional to the amount of plutonium administered. On the other hand, average dose rates to the spleen and bone marrow were characteristic in that they were not proportional to the amount of plutonium administered. Elevated dose rates (rad/day) were obtained in the spleen and the bone marrow, where there were weight losses resulting from the internal exposure to the deposited plutonium. Therefore, radiation dose to the spleen and bone marrow can not be solely obtained in proportion to the administered dose.

Accumulation modes of alkylating agents on normal peripheral blood lymphocytes

The in vitro uptake by normal peripheral blood lymphocytes of 14C-labeled cyclophosphamide and nitrogen mustard has been measured in a manner which parallels cell exposure to drugs used in the nitrogen mustard-oncovin-procabazine-prednisone (MOPP) and cyclophosphamide-oncovin-procarbazine-prednisone (COPP) clinical protocols. Accumulation of these alkylating agents occurs in two recognizable patterns. The first exhibits a saturation phenomenon, since radioactivity can be partially blocked by an equal concentration of unlabelled drug, reflects stereospecificity, and represents a minor fraction of total deposition. The second form, proportionately larger than the first, is dependent on drug concentration in the suspending medium, with radioactivity increasing in an apparently limitless linear fashion, uninfluenced by competitive inhibition. This part also is less tenaciously held by the lymphocyte. While the mere presence of drug on the lymphocytes does not necessarily imply injury or lethality, the fact that these peripheral lymphocytes are able to accumulate cytotoxic agents and are partially interchangeable with an analogous fixed lymphoid cell mass suggests that clinical immunosuppression and lymphocytopenia may be related, in part, to cell drug deposition.

Energy Transfer in Radiolysis of Rare-Gas—C2F6 Mixtures

The gas-phase gamma radiolysis of C2F6 with He, Ne, Ar, Kr, and Xe has been examined as a function of the fraction of energy deposition in the rare gas. For 90% energy deposition in the rare-gas energy-transfer efficiencies of 5%, 47%, 92%, 78%, and 36% in the respective mixtures of He to Xe were observed. The transfer efficiency is shown to depend on the difference between the recombination energies of C2F6 and the rare gas. This dependence indicates the existence of charge-transfer processes although some excitation transfer also takes place. In Xe–C2F6 mixtures charge transfer is endothermic and the change in product distribution supports the expectation that only excitation transfer occurs.