IAPCS: A Computer Model that Evaluates Pollution Control Systems for Utility Boilers

The IAPCS model, developed by U.S. EPA’s Air and Energy Engineering Research Laboratory and made available to the public through the National Technical Information Service, can be used by utility companies, architectural and engineering companies, and regulatory agencies at all levels of government to evaluate commercially available technologies for control of SO₂, NO_x, and particulate matter emissions from coal-fired utility boilers with respect to performance and cost. The model is considered to be a useful tool to compare alternative control strategies to be used by utilities to comply with the requirements of the CAA, and to evaluate the sensitivity of control costs with respect to many of the significant variables affecting costs.

To illustrate the use of the model for site-specific studies, the authors used the model to estimate control costs for SO₂ and NO_x control at Detroit Edison’s Monroe plant and two hypothetical plants under consideration and at three plants operated by New York State Electric and Gas Corporation. The economic and technical assumptions used to drive the model were those proposed by the utilities if cited, and if not cited, the model default values were used. The economic format and methodologies for costs cited in the Electric Power Research Institute’s Technical Assessment Guide are used in the IAPCS model. Depending on the specific conditions and assumptions for the cases evaluated, SO₂ control costs ranged from $417 to $3,159 per ton of SO₂ removed, and NO_x control costs ranged from $461 to $3,537 per ton of NO_x removed or reduced.     

Radionuclide content of Las Vegas Wash sediments

The Las Vegas Wash is an excavated waterway channel which drains all surface water and effluent discharge from sewage-treatment facilitates from the greater Las Vegas Metropolitan Area to Lake Mead. Fine and course sediment samples were collected at 100-m intervals and analyzed to determine the distribution of gamma-emitting radionuclides in the lower 5,500 m of the Las Vegas Wash. Results indicate depletion of long-lived fission products in upstream Wash sediments. However, trace levels of ¹³⁷Cs measured in downstream sediments suggest the resuspension and transport of radioactive fallout within the Wash. Levels of ⁴⁰K, ²³²Th, ²³⁵U, and ²³⁸U found in Wash sediments were consistent with levels typically found in southeast Nevada soils.     

Trace Metal Uptake By Pichia Spartinae, an Endosymbiotic Yeast in the Salt Marsh Cord Grass Spartina Alterniflora

The ascosporogenous marine yeast Pichia spartinae is a dominant endosymbiont of the marsh grass Spartina alterniflora. Results of previous studies suggested that P. spartinae is involved in iron transport processes in the grass. of particular interest has been the mechanisms of metal uptake and metabolism by the yeast, and the ecological and plant biochemical significance of these processes. This investigation examined the uptake of iron and other metals (Zn, Cu, Cd, Ni, Pb, Cr) by P. spartinae, and provides data on possible mechanisms of this activity. the results suggest a) the yeast can assimilate divalent and trivalent forms of inorganic iron, as well as large organic-Fe(III) complexes, b) the uptake of inorganic trivalent iron under soluble iron-deficient conditions proceeded by a different mechanism than that of soluble Fe(II), with intracellular loadings of iron much increased under the former conditions; c) trivalent iron uptake is not mediated by hydroxamate siderophores at levels detectable by sensitive screening assays; d) the assimilation of some trace metals (Cu, Zn, Cd, Ni) is likely to be mediated by low molecular weight cysteine rich proteins, possibly metallothionein, and; e) siderophores from other fungi can provide iron for P. spartinae. the iron assimilation data suggested that multiple mechanisms are involved, and are influenced by the concentration and speciation of iron in the system. in general, iron assimilation mechanisms are comparable to those described for closely related yeasts, such as Saccharomyces cerevisiae. Among other things, these results indicated that future studies of trace metal mobilization and plant assimilation in salt marsh ecosystems must account for the activities of microbial symbionts associated with the plants.     

Movement of oxybiotic and thiobiotic meiofauna in response to changes in pore-water oxygen and sulfide gradients around macro-infaunal tubes

The effects of changes in vertical and horizontal microscale gradients of oxygen and sulfide on meiofaunal distributions were examined in laboratory microcosms. Specifically, the effect of tube abandonment and reestablishment by macro-infauna on the distribution of subsurface turbellarians, gnathostomulids and gastrotrichs was studied. Meiofauna responded rapidly (within 6 h) to changing sediment chemistry, consistently trying to reoccupy optimal habitat. Every subsurface taxon had a preferred suboptimal habitat which it occupied primarily during transit from deteriorating to newly established optimal habitat. Only during this time did the distribution of ecologically similar taxa overlap substantially. Changes in oxygen and sulfide gradients could explain most but not all of the response; food availability might also be important. Oxybios consistently chose oxic suboptimal microhabitat. Thus behaviorally, as well as biochemically and ecologically, thiobios represent a distinct group among the meiofauna.     

Investigation of contact vacuuming for remediation of fungally contaminated duct materials

Environmental fungi become a potential Indoor Air Quality (IAQ) problem when adequate moisture and nutrients are present in building materials. Because of their potential to rapidly spread contamination throughout a building, ventilation system materials are of particular significance as potential microbial contamination sources. Current recommendations are to discard fibrous glass insulation that appears to be wet or moldy. Unfortunately, this advice is not always followed. Instead, cleaning is sometimes being used in buildings to remediate fibrous glass duct liner that is already contaminated with microbial growth. The objectives of this research program were to: 1) determine, under dynamic test conditions, whether fungal spore levels on heating, ventilating, and air-conditioning (HVAC) duct material surfaces could be substantially reduced by thorough vacuum cleaning, 2) evaluate whether subsequent fungal growth could be limited or contained by mechanical cleaning, and 3) provide data concerning the advisability of cleaning duct materials. The constant high relative humidity (RH) environment to which the test materials were exposed during this study was selected as a favorable growth environment that is frequently found in Southeastern United States HVAC systems. The results showed that, following cleaning, the levels of the two test fungi, A. versicolor and P. chrysogenum, recovered to preclean levels within 6 weeks. Therefore, mechanical cleaning by contact vacuuming alone was able to only temporarily reduce the surface fungal load. The current guidelines to discard contaminated materials should be followed.     

Sub-canopy deposition of ozone in a stand of cutleaf coneflower

Although there has been a great deal of research on ozone, interest in exposure of native, herbaceous species is relatively recent and it is still not clear what role the pollutant has in their ecological fitness. The ozone exposure of a plant is usually expressed in terms of the concentration above the canopy or as a time-weighted index. However, to understand the physiological effects of ozone it is necessary to quantify the ozone flux to individual leaves as they develop, which requires knowing the deposition velocity and concentration of the pollutant as a function of height throughout the plant canopy. We used a high-order closure model of sub-canopy turbulence to estimate ozone profiles in stands of cutleaf coneflower (Rudbeckia laciniata L.) located in the Great Smoky Mountains National Park, USA. The model was run for periods coinciding with a short field study, during which we measured vertical concentration profiles of ozone along with measurements of atmospheric turbulence and other meteorological and plant variables. Predictions of ozone profiles by the model are compared with observations throughout the canopy.     

Disaster study of war

In the first part of this article I argue that war should be considered as a disaster. A brief historical review of the relationship of the field of disaster studies to military concerns is presented in an effort to demonstrate that, in fact, war has been a familiar subject in the field. I then consider definitions of disaster and conclude that war is easily accommodated by them. In the main section of the article I attempt to uncover distinctive characteristics of war by submitting war to analysis within well known sociological frameworks for disasters. Finally, some methodological considerations for the study of war disasters are presented.     

How many samples are required? Evaluating a model for verification of carbon sequestration in a hybrid poplar buffer strip

A model is developed to predict annual and total above-ground carbon storage within a hybrid poplar stream buffer. The regression model predicts tree wet weight based upon circumference at breast-height (137 cm) with an r-square value of 0.9922. Carbon storage in above-ground biomass is estimated to be 3.57 to 3.71 metric tons per hectare, with a measured annual increment of 0.92 to 1.37 metric ton per hectare per year. The variability of carbon storage within this biological system, including soil organic matter, is explored, and the number of samples required to achieve a desired level of statistical certainty are predicted. As has been investigated previously for other biological systems (Garten and Wullschleger, 1999), the study shows that a prohibitively large number of samples must be taken in order to achieve high degrees of certainty about mean carbon storage values. The study also shows, however, that mean values with somewhat greater uncertainties can easily be achieved with much smaller sample sizes. Thus carbon sequestration verification might be accomplished cost-effectively if the degree of certainty required is not unrealistically high for highly variable natural systems.     

An Overview of Sediment Organic Matter Records of Human Eutrophication in the Laurentian Great Lakes Region

The isotopic and molecular compositions of organic matter buried in lake sediments provide information that helps to reconstruct past environmental conditions and to assess impacts of humans on local ecosystems. This overview of sedimentary records from the North American Great Lakes region describes examples of applications of organic geochemistry to paleolimnological reconstructions. These lakes experienced a succession of human-induced environmental changes that started after completion of the Erie Canal in 1825. Agricultural deforestation in the mid-nineteenth century released soil nutrients that increased algal productivity and caused an associated increase in algal biomarkers in sediment records. Eutrophication that accompanied magnified delivery of municipal nutrients to the lakes in the 1960s and 1970s created excursions to less negative δ¹³C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror the isotopic evidence of eutrophication in the Great Lakes.     

Cellulose degradation by Lulworthia floridana and other lignicolous marine fungi

Gravimetric analyses of cellulose (Solka Floc) utilization by representative marine Ascomycetes, including Lulworthia floridana, Lindra sp., Torpedospora sp. and Halosphaeria mediosetigera, have shown noteworthy activity based on loss of weight of cellulose by the various fungi. Particularly striking activity is evidenced by L. floridana and Torpedospora sp., with >50% cellulose degradation after 3 weeks of fungal growth. Comparable studies with the deuteromycete, Dendryphiella salina, showed >50% loss within 6 days. Dissimilar responses by various L. floridana isolates are noted. Intensive degradative activity at pH's of 6 to 8 is common along with negligible amounts of cellulase (Cx units). Adsorption of the enzyme to the mycelia or to the cellulose particles in the medium is suggested. Earlier laboratory analyses of fungal degradation of Manila cordage compare favorably with present gravimetric studies and support field observations on the significance of fungal infestation of wood, particularly that incited by the Lulworthia floridana group.This work was supported by Grant GM 12482 from the National Institute of Health and Office of Naval Research Contract No. 137-792 to the Institute of Marine Sciences, University of Miami. Contribution No. 950 from the Institute of Marine Sciences, University of Miami.