Modeling sorbent injection for mercury control in baghouse filters: II--pilot-scale studies and model evaluation

Activated carbon injection for Hg control in a 500-lb/hr pilot-scale coal-fired furnace equipped with a fabric filter for particulate control was evaluated at different operating conditions. The pilot-scale tests showed that Hg removal was improved at lower temperatures and higher C/Hg ratios. The two-stage mathematical model developed to describe Hg removal using powdered activated carbon injection upstream of a baghouse filter was used to obtain Langmuir isotherm parameters as a function of temperature by fitting the model to a subset of experimental data. The predictive capability of the model was then tested by comparing model calculations with additional experimental data from this system obtained using different operating temperatures and sorbent to Hg ratios. Model predictions were in good agreement with experimentally measured Hg removal efficiency. Based on the model predictions, Hg removal in the duct appears to be limited and higher C/Hg ratio, lower operating temperature, and longer cleaning cycle of the baghouse filter should be utilized to achieve higher Hg removal in this system.     

Development of a sampling train for the assessment of particulate fugitive emissions

A prototype portable Fugitive Assessment Sampling Train (FAST), designed to obtain large samples of particulate emissions generated by sources whose configurations preclude sample collection before the diffusion of the emissions into the ambient atmosphere, has been successfully fabricated and tested. The prototype FAST utilizes a combination of commercially available and specially designed equipment to collect a 500 milligram particulate sample in an 8-hour period at locations downwind of most industrial fugitive sources. The particulate sample is separated into inhalable and respirable fractions and provides sufficient material for a complete Level 1 assessment including bioassays. A quantity of organic species larger than C₆, sufficient for mass spectrometry analysis, is collected on a bed of adsorbent resin. The establishment of design criteria and operating parameters, selection and design of hardware components, and the fabrication and initial testing of the FAST are discussed. The results of calibration tests and an initial field trial are presented and a plan for additional development is outlined.     

Temporal - and dose-related characteristics of biochemical and morphological alterations in the hamster induced by 2,3,7,8-tetrachlorodibenzo- -dioxin

The temporal - and dose-related characteristics of hepatic enzymes induced and toxic responses elicited in the hamster by 2,3,7,8-tetrachlorodibenzo- -dioxin were examined. The results demonstrate a dissociation of the induction of these hepatic enzymes from TCDD-elicited lethality, but not necessarily hepatic damage, in this species. Furthermore, the hyperthyroidism observed is suggestive of a role of these hormones in the relatively insensitive nature of this species to TCDD treatment.     

Distribution of Diatoms in a Forested Stream Containing a Series of Interconnected Lakes

We explored the spatial variation in diatom communities withinthe Turkey Lakes Watershed (TLW). The TLW is a single watershed in an old growth sugar maple forest that contains an alternatingseries of stream and lake embayments. Near the outlet of each lake, we sampled pools and riffles to determine abundance and diversity of diatom communities along this hydrologic system. Diatom diversity, measured by Shannon-Weaver Index, richness andevenness, increased steadily downstream before eventually decreasing near the watershed outlet. Canonical CorrespondenceAnalysis indicated that diatom genera were correlated with streamchemistry. Upper reaches were the least productive, characterizedby lower pH (<7), higher N:P (113:1 to 124:1, dominated by complex forms of N), and high mean relative abundances of Eunotia spp., Tabellaria spp., and Pinnularia spp. Middle and lower reaches were more productive, characterized byhigher pH (>7), lower N:P (71:1 to 90:1, dominated by simple forms of N, e.g., nitrate-N), and high mean relative abundances of Cymbella spp. and Brachysira spp. Achnanthesminutissima (Kutz.) Hustedt, the most abundant species, and Navicula spp., Nitzschia spp., Gomphonema spp., and Frustrulia spp. were represented at all stream sites. Thisstudy revealed that within the TLW, a hydrologic system of the same stream order, the diatom community was influenced by a nutrient gradient, where the stream and its intervening lakes contributed to a shift from acidic, inorganic N-poor upper reaches to a circum-neutral, inorganic N-richer outlet. By imparting genera-specific stresses, stream flow (i.e. pools vs. riffles) further shaped the diatom community.     

Smart Growth in a Small Urban Setting: the challenges of building an acceptable solution

Smart growth policies direct development towards existing communities already served by roads, sewer systems and other infrastructure. The increased development in these communities in turn should enable them to benefit from a stronger tax-base, more efficient use of their schools and other public facilities, and the renewed economic vitality of their urban centres. These goals and objectives appear to complement and support the efforts of urban mayors to attract new property tax rateables and better-paying jobs, but they may conflict with the desires of residents to reduce densities and improve the quality of life. We use a visual GIS-based model to assist five small contiguous older suburbs individually and collectively to evaluate their current redevelopment plans and to understand the implications of their land-use decisions on the quality of life in their communities. By bringing them together as a group, and our raising broader redevelopment and impact issues, they have begun to rethink how these properties could be best used to meet the community's needs and to see them in the context of similar redevelopment plans within their mini-region. One of the changes emerging is a greater role for certain types of residential development and a concurrent reduction in the amount of commercial space being considered. The authors would like to thank the Geraldine R. Dodge Foundation for funding this project, the Somerset County Planning Board and mayors of the five towns for actively supporting and participating in the study and the Regional Planning Partnership for its co-operation and assistance in refining its GOZ model to promote regional planning from the bottom up. The authors accept full responsibility for the ideas and recommendations in this report.     

Shoot biomass of turfgrass cultivars grown on composted waste

Various cultivars of four cool-season grass types (tall fescue, fine fescue, perennial ryegrass, and Kentucky bluegrass) were seeded in 0.34-liter plastic pots containing either composted sewage sludge [Com-Til² (CT), Soil Magic² (SM)] or composted yard mulch (YM). Plants were grown in the greenhouse for four weeks prior to measuring shoot biomass. White most tall fescue cultivars showed more shoot growth on YM, perennial ryegrass cultivars generally grew better on SM. Cultivars of fine fescue and bluegrass grew about the same on YM or SM, and slightly less on CT. With very few exceptions, shoot biomass of individual cultivars was greater on either YM or SM than it was on CT. Within individual grass types, Pennlawn (fine fescue), Pennant (perennial ryegrass), and Victa (Kentucky bluegrass) averaged consistently better growth on all three composted media. For tall fescue, Aquara, Rebel II, and Monarch performed best on YM, SM, and CT, respectively. Bioaccumulation of heavy metals did not occur in selective samples of shoot tissues collected from the grass types used. This research was supported by National Science Foundation grant #8902053 to Buckeye Bluegrass Farms. The greenhouse studies described in this paper were performed in conjunction with field tests conducted at Buckeye Bluegrass Farms. Requests for information on field trials should be directed to H. F. Decker, Box 176, Ostrander, Ohio 43061, USA. Use of trade names is for the reader's information only and does not imply endorsement over similar products of like properties.     

The relationship of beer consumption and state alcohol and motor vehicle policies to fatal accidents

Fatal accident data from 50 states and the District of Columbia were examined in order to determine the relationship between alcohol availability and fatal motor vehicle accidents. This relationship was analyzed for both fatal accidents and motor vehicle fatalities (potentially more than one per accident) using multiple regression. The independent variables were: (1) driving age (percent of drivers under 21); (2) beverage purchase age; (3) average beer consumption; (4) number of outlets per million population selling alcohol for on-premise consumption; (5) percentage of metropolitan residents; (6) percentage of male drivers; and (7) mileage per driver per year. It was found that the regression analyses for fatal accidents and for fatalities were highly similar. Driving age was the strongest predictor of highway mortality. On-premise availability of alcohol was significantly and inversely associated with motor vehicle fatalities. This suggests that when on-premise outlets are fewer and more geographically spread out, the chances of drinking and driving are greater. Finally, average beer consumption was significantly and positively associated with highway fatalities perhaps because many drivers consider it a “soft” alcoholic beverage that will not impair their ability to drive.     

Assessing representativeness of places for conservation reservation and heritage listing

Problems arising from application of the representative criterion for conservation and natural heritage evaluation are discussed. An ecological basis to this criterion is suggested that focuses on those key environmental factors dominating biotic response. A methodology is proposed that utilizes computer-based methods of establishing and interrogating spatial data bases (geographic information systems), environmental modeling, and numeric analysis. An example is presented illustrating some of the advantages and limitations of classification and dimension reduction techniques in both defining bioenvironments and displaying their spatial distribution. The advantages of this method for representativeness evaluation are that it maximizes the utility of available data, is explicit and repeatable, and enables large areas to be analyzed at relatively fine scales.