Air revitalization compounds: A literature survey

Chemical processes for air revitalization are attractive alternatives for some closed life support systems in the applications of space and marine explorations. A review of the literature is given for the purpose of evaluating potential candidates as air revitalizing chemicals based upon a set of criteria including toxicity in use, removal of airborne contaminants and bacteria, theoretical oxygen yields, chemical reactivity to breathing atmospheres, and commercial availability. The preliminary evaluation shows potassium and sodium Superoxides as prime candidates for further evaluation against the practical considerations of actual use. Upon closer scrutiny, potassium Superoxide is the desired chemical for air revitalization in closed life support systems according to the present technology. Kinetic reaction rates for the simple hydration of KO₂ were reported to increase for increasing pressures to 12 atm making it a promising air revitalization chemical at the hyperbaric conditions encountered in deep diving.     

Precipitator Equipment

The purpose of this section is to set forth the main elements and features of the equipment used for the collection of fly ash. Hardware and structural details of a routine nature having little or no bearing on basic performance are outside the scope of the paper.     

The relationship between blend miscibility and biodegradation of cellulose acetate and poly(ethylene Succmate) blends

The miscibility of cellulose acetate (CA; degree of substitution = 2.5) and poly(ethylene succinate) (PES) has been investigated using a variety of thermal techniques and by solid-state carbon13 NMR spectroscopy. The blends containing greater than ca. 70% CA were found to be miscible. In the case of blends containing less than ca. 70% CA, a combination of thermal and NMR analyses suggests that these blends are not fully miscible on a 2.5- to 5-nm scale. On the scale which can be probed by dynamic mechanical thermal analysis (15 nm), the low-percentage CA blends exhibit “significant local concentration fluctuations≓. Investigation of the biodegradation of the blend components and of the blends revealed that PES degraded relatively rapidly and that CA degraded slowly. The blends degraded at a rate essentially identical to that of CA. Miscibility (75% CA blend) or crystallization of PES (30% CA blend) had no significant effect. These data suggest that a significant mode of degradation ófPES during composting involves chemical hydrolysis of the polymer followed by biological assimilation of monomers. Degradation of the blends is initiated in the amorphous phase. Because CA is a significant component of the amorphous phase, a small amount of CA significantly impacts the biodegradation rates of the blends.     

WATERSHED RESPONSES TO CLIMATE CHANGE AT GLACIER NATIONAL PARK1

ABSTRACT: We have developed an approach which examines ecosystem function and the potential effects of climatic shifts. The Lake McDonald watershed of Glacier National Park was the focus for two linked research activities: acquisition of baseline data on hydrologic, chemical and aquatic organism attributes that characterize this pristine northern rocky mountain watershed, and further developing the Regional Hydro-Ecosystem Simulation System (RHESSys), a collection of integrated models which collectively provide spatially explicit, mechanistically-derived outputs of ecosystem processes, including hydrologic outflow, soil moisture, and snow-pack water equivalence. In this unique setting field validation of RHESSys, outputs demonstrated that reasonable estimates of SWE and streamflow are being produced. RHESSys was used to predict annual stream discharge and temperature. The predictions, in conjunction with the field data, indicated that aquatic resources of the park may be significantly affected. Utilizing RHESSys to predict potential climate scenarios and response of other key ecosystem components can provide scientific insights as well as proactive guidelines for national park management.     

Day-of-Week behavior of atmospheric ozone in three U.S. cities

The weekly cycles of atmospheric ozone (O3) are of interest because they provide information about the response of O3 to changes in anthropogenic emissions from weekdays to weekends. The weekly behavior of O3 in Chicago, IL; Philadelphia, PA; and Atlanta, GA, is contrasted. In Chicago and Philadelphia, maximum 1-hr average O3 increases on weekends. In Atlanta, O3 builds up from Mondays to Fridays and declines during weekends. In all three areas, volatile organic compound (VOC)/nitrogen oxides (NOx) ratios are higher during weekends, resulting from greater than proportionate decreases in NOx relative to VOC emissions. The VOC/NOx ratios correlate with maximum 1-hr O3 concentrations in Chicago, a response consistent with a VOC-sensitive airshed. A weak correlation between O3 concentrations and VOC/NOx ratios in Philadelphia suggests the impact of transported O3, which is formed in upwind VOC-sensitive locations that may be hundreds of kilometers away. Ozone concentrations in Atlanta do not correlate with VOC/NOx ratios but with concentrations of NOx and total reactive nitrogen (NOy) carried over from the previous day. When data from 1986-1990 and 1995-1999 are compared, only small differences in the weekly behavior of O3 are observed in Chicago and Philadelphia. The day-of-week differences in O3 are amplified in the more recent period in Atlanta, a possible result of urban growth.     

Effective parameters for two-phase flow in a porous medium with periodic heterogeneities

Computational simulations of two-phase flow in porous media are used to investigate the feasibility of replacing a porous medium containing heterogeneities with an equivalent homogeneous medium. Simulations are performed for the case of infiltration of a dense nonaqueous phase liquid (DNAPL) in a water-saturated, heterogeneous porous medium. For two specific porous media, with periodic and rather simple heterogeneity patterns, the existence of a representative elementary volume (REV) is studied. Upscaled intrinsic permeabilities and upscaled nonlinear constitutive relationships for two-phase flow systems are numerically calculated and the effects of heterogeneities are evaluated. Upscaled capillary pressure-saturation curves for drainage are found to be distinctly different from the lower-scale curves for individual regions of heterogeneity. Irreducible water saturation for the homogenized medium is found to be much larger than the corresponding lower-scale values. Numerical simulations for both heterogeneous and homogeneous representations of the considered porous media are carried out. Although the homogenized model simulates the spreading behavior of DNAPL reasonably well, it still fails to match completely the results form the heterogeneous simulations. This seems to be due, in part, to the nonlinearities inherent to multiphase flow systems. Although we have focussed on a periodic heterogeneous medium in this study, our methodology is applicable to other forms of heterogeneous media. In particular, the procedure for identification of a REV, and associated upscaled constitutive relations, can be used for randomly heterogeneous or layered media as well.     

Concentration and composition of atmospheric aerosols from the 1995 SEAVS experiment and a review of the closure between chemical and gravimetric measurements

We summarize the results from the various measurements and the inter-sampler comparisons from Southeastern Aerosol and Visibility Study (SEAVS), a study with one of its objectives to test for closure among chemical, gravimetric and optical measurements of atmospheric aerosol particles. Sulfate and organics are the dominant components of the SEAVS fine particles (nominally, particles with aerodynamic diameter < or = 2.5 microns) but between 28 and 42% (range over various samplers) of the gravimetrically measured total fine particle concentration is unidentified by the chemical measurements. Estimates of water associated with inorganic components and measurement imprecision do not totally explain the observed difference between gravimetric and chemical measurements. We examine the theoretical and empirical basis for assumptions commonly made in the published literature to extrapolate total fine particle concentration on the basis of chemical measurements of ions, carbon and elements. We then explore the more general question of closure using the SEAVS data as well as data from other, similar studies reported in the literature. In so combining the SEAVS measurements with other similar studies, we find a strong association between organic carbon and the unidentified component, that is, the fraction of the total fine particle concentration not identified by chemical measurements. We offer several tenable hypotheses for the relationship between the organic and unidentified components that deserve to be tested in future work. Specifically, we hypothesize that (1) errors in the sampling and analysis of organic carbon; (2) estimates of organic mass from measurements of organic carbon; and/or (3) water absorption by organics may all contribute to the observed relationship.     

Comparison of three extraction methods for 17beta-estradiol in sand, bentonite, and organic-rich silt loam

Extraction is an important procedure for samples that contain soil because other compounds in soil may affect analysis of estrogens. This study was conducted to evaluate three different extraction methods for 17beta-estradiol in soil. Sand, bentonite, and organic-rich silt loam were spiked with 1 mg kg(-1) of 17beta-estradiol as a model compound of estrogens. 17beta-estradiol and its metabolites, estrone and estriol, were extracted using (i) a modified Bligh and Dyer extraction, (ii) a pressurized fluid extraction, and (iii) a diethyl ether extraction, and measured by liquid chromatography tandem mass spectrometry. There were significant differences in the extraction efficiency for 17beta-estradiol among the extraction methods and the soils: the efficiencies ranged from 10% to 97%. Overall, the diethyl ether extraction method had the largest efficiency of 17beta-estradiol with 45% and 57% for bentonite and silt loam, respectively. Transformation of 17beta-estradiol to estrone and estriol in the different extraction methods was less than 3.6% during the extraction procedures. This study underlined the importance of sample preparation for estrogen analysis in soil samples.     

Mapping sediment contamination and toxicity in Winter Quarters Bay,McMurdo Station,Antarctica

Winter Quarters Bay (WQB) is a small embayment located adjacent to McMurdo Station, the largest researchbase in Antarctica. The bay is approximately 250 m wide andlong, with a maximum depth of 33 m. Historically, trashfrom the McMurdo Station was piled on the steep shoreline ofWQB, doused with fuel and ignited. That practice hasceased, and the adjacent land area has been regraded tocover the residual waste. The bottom of WQB remainslittered with drums, equipment, tanks, tires, cables, andother objects, especially the southeastern side of the baywhere dumping took place. Sediments are contaminated withPCBs, metals, and hydrocarbon fuels. The objectives of this study were to map the distributionof organic contaminants in WQB, assess the toxicity of WQB sediments using a simple microbial test, anddetermine correlations between toxicity and contaminantlevels. The study suggests that adverse ecological effectshave occurred from one or more of the contaminants found inWQB but the source of the toxic impacts to bay sedimentsremains unknown. Whole sediment toxicity was onlycorrelated with oil-equivalent while solvent extracts ofsediments were correlated with PAHs and oil-equivalent. Theauthors recommend that an integrated research plan bedeveloped that focuses on determining what additionalinformation is needed to make informed decisions on possibleremediation of WQB.