Designing a Filter System to Meet Specified Efficiency and Emissions Levels

Fabric filter technology in conjunction with existing system designs holds promise for submicron pariiculate capture. Field data to support this position are only now becoming available with improved tools for submicron particulate testing.     

Sulfur Gas Emissions From Stored Flue Gas Desulfurization Sludges

The emissions of volatile sulfur-containing compounds from 13 flue gas desulfurization (FGD) sludge field storage sites have been characterized. Sulfur gas emissions from the sludge surfaces were determined by measuring the sulfur gas enhancement of sulfur-free sweep air passing through a dynamic emission flux chamber placed over selected sampling sites. Samples of the enclosure sweep air were cryogenically concentrated in surface-deactivated Pyrex “U” traps. Analyses were conducted by wall-coated, open-tubular, capillary column, cyrogenic gas chromatography using a sulfur-selective, flame photometric detector. Several major variables associated with FGD sludge production processes were examined in relation to the measured range and variations in sulfur fluxes including: (a) the sulfur dioxide scrubbing reagent used, (b) sludge sulfite oxidation, (c) “unfixed” or “fixed” FGD sludge, and (d) ponding or landfill storage. The composition and concentration of the measured sulfur gas emissions were found to vary with the type of sludge, the effectiveness of rainwater drainage from the landfill surface, the method of impoundment, and the sulfate/sulfite ratio of the sludge. Hydrogen sulfide, carbonyl sulfide, dimethyl sulfide, carbon disulfide, and dimethyl disulfide were identified in varying concentrations and ratios in the FGD sludge emissions. In addition, up to four unidentified organo- sulfur compounds were found in the emissions from four FGD sludges. The sulfur flux from one FGD storage pond was analyzed by gas chromatography-single ion monitoring mass spectrometry. In addition to the four identified sulfur compounds, this flux contained large concentrations of benzene, toluene, and α-pinene. The measured, total sulfur emissions ranged from less than 0.01 to nearly 0.3 kg of sulfur per day for an equivalent 100 acre (40.5 hectare) sludge impoundment surface.     

A Reassessment of the Economic Effects of Ozone on U.S. Agriculture

The potential adverse effects of environmental change on agriculture have motivated considerable public research on this topic. Acid deposition, gaseous air pollutants, stratosphere ozone depletion and "green house" phenomena, individually and in combination, have been or are being evaluated in terms of effects on agricultural productivity. Assessments of the economic consequences of such effects have also been performed as input into the regulatory process. As with any applied bioeconomic analysis, the credibility of these economic assessments is dependent on the quality of the natural science and other data on the pollutant In question.

The ability of economists to assess the agricultural effects of one important pollutant, tropospheric ozone, has been Improved by the recently completed National Crop Loss Assessment Network (NCLAN). The structure, protocols and initial plant science findings of this U.S. Environmental Protection Agency program have been presented in this journal (see, for example, Heck et al).^1-2 In a related article,³ we reported the economic consequences of those preliminary ozone crop yield effects. Summary plant science findings have now been published.⁴

We provide here a more complete analysis of estimated benefits from reductions in troposphere ozone based on the final results of the NCLAN plant science research. In doing so, we concentrate on improvements in the modeling and underlying data which are reflected In this current assessment. While uncertainties still remain, these improvements should result in more defensible estimates of the magnitude of ozone’s effects on U.S. agriculture.     

An updated assessment of the acute impacts of ocean carbon sequestration by direct injection

This paper evaluates the expected environmental impact of several promising schemes for ocean carbon sequestration by direct injection of CO₂, and serves as a major update to the assessment by Auerbach et al. (1997) and Caulfield et al. (1997) of water quality impacts and the induced mortality to zooplankton. Three discharge approaches are considered, each designed to maximize dilution over the water column: a point release of negatively buoyant CO₂ hydrate particles from a moving ship; a stationary point release of CO₂ hydrate particles forming a sinking plume; and a long, bottom-mounted diffuser discharging buoyant liquid CO₂ droplets. Two of these scenarios take advantage of the enhanced dilution offered by CO₂ hydrate particles, and are based on recent laboratory and field studies on the formation and behavior of such particles. Overall, results suggest that it is possible with present or near present technology to engineer discharge configurations that achieve sufficient dilution to largely avoid acute impacts. In particular, the moving ship hydrate discharge is identified as the most promising due to its operational flexibility. In addition to lethal effects, sub-lethal and ecosystem effects are discussed qualitatively, though not analyzed quantitatively. Our main conclusion is that ocean carbon sequestration by direct injection should not be dismissed as a climate change mitigation strategy on the basis of environmental impact alone. Rather, it can be considered as a viable option for further study, especially in regions where geologic sequestration proves impractical.     

Relative Importance of Intrinsic,Extrinsic, and Anthropic Factors in the Geomorphic Zonation of the Trinity River,Texas1

Phillips, Jonathan D., 2010. Relative Importance of Intrinsic, Extrinsic, and Anthropic Factors in the Geomorphic Zonation of the Trinity River, Texas. Journal of the American Water Resources Association (JAWRA) 46(4): 807-823. DOI: 10.1111/j.1752-1688.2010.00457.x Abstract: The Trinity River, Texas, was characterized according to its geologic framework, valley width and confinement, slope, sinuosity, channel-floodplain connectivity, and flow regime, leading to the identification of 18 hinge points along the 638 km study area where major transitions in two or more criteria occur. These, and effects of human agency, avulsions, and sea level rise, delineate 21 river styles or zones. Each zone was evaluated with respect to dominant factors determining its geomorphological characteristics: geology/lithology, tectonics, Holocene sea level rise, meandering, cutoffs and other lateral channel changes, avulsions, valley constrictions by alluvial terraces, and paleomeander depressions. Direct human influences (a large impoundment and water withdrawals) are also evident. Entropy of the relationships between these controls and the geomorphological zones shows that all the controls are significant, and each accounts for 4-15% of the total entropy. Geologic controls, lateral channel changes, and constriction by terraces are the three most influential controls, illustrating that controls on river morphology include extrinsic boundary conditions, active process-form interrelationships, and inherited features. Extrinsic and intrinsic controls each account for about a third of the entropy, but the latter includes antecedent features as well as active channel dynamics, underscoring the importance of historical contingency even in alluvial rivers.     

Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment1

Crockett, Kris, Jonathan B. Martin, Henri D. Grissino-Mayer, Evan R. Larson, and Thomas Mirti, 2010. Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment. Journal of the American Water Resources Association (JAWRA) 1-13. DOI: 10.1111/j.1752-1688.2010.00464.x Abstract: Information about long-term variability of streamflow is important to allocate water resources, but few historical records extend more than 75 years into the past, requiring proxy records to evaluate flow prior to that time. Flow proxies have been found in tree-ring widths in temperate regions, but have rarely been used in humid subtropical environments because the relationship between tree growth and climate was believed to be weakened by limited seasonality and stress on tree growth from drought conditions. Tree-ring residual chronologies from two forests sampled from northern Florida correlate well with historical annual discharge (r² values as high as 0.47) from 3 of 15 river-gauging stations that were used to compare with the tree-ring chronologies. The best correlations occur where streamflow has little contribution from spring discharge or continuous flow from lakes and wetlands. Streams lack correlations with the tree-ring residual chronologies (r² values as low as 0.0002) where springs and continuous discharge from lakes mute variations in their flow. Tree-ring chronologies appear to be useful for reconstruction of prehistorical variations of some streamflow in humid subtropical regions, but interpretations of the reconstructions must consider the local hydrologic conditions.     

An assessment of the impact of climate change on air quality at two UK sites

Possible effects of climate change on air quality are studied for two urban sites in the UK, London and Glasgow. Hourly meteorological data were obtained from climate simulations for two periods representing the current climate and a plausible late 21st century climate. Of the meteorological quantities relevant to air quality, significant changes were found in temperature, specific humidity, wind speed, wind direction, cloud cover, solar radiation, surface sensible heat flux and precipitation. Using these data, dispersion estimates were made for a variety of single sources and some significant changes in environmental impact were found in the future climate. In addition, estimates for future background concentrations of NO_x, NO₂, ozone and PM₁₀ upwind of London and Glasgow were made using the meteorological data in a statistical model. These showed falls in NO_x and increases in ozone for London, while a fall in NO₂ was the largest percentage change for Glasgow. Other changes were small. With these background estimates, annual-average concentrations of NO_x, NO₂, ozone and PM₁₀ were estimated within the two urban areas. For London, results averaged over a number of sites showed a fall in NO_x and a rise in ozone, but only small changes in NO₂ and PM₁₀. For Glasgow, the changes in all four chemical species were small. Large-scale background ozone values from a global chemical transport model are also presented. These show a decrease in background ozone due to climate change. To assess the net impact of both large scale and local processes will require models which treat all relevant scales.     

Spatial and temporal variability in urban fine particulate matter concentrations

Identification of hot spots for urban fine particulate matter (PM(2.5)) concentrations is complicated by the significant contributions from regional atmospheric transport and the dependence of spatial and temporal variability on averaging time. We focus on PM(2.5) patterns in New York City, which includes significant local sources, street canyons, and upwind contributions to concentrations. A literature synthesis demonstrates that long-term (e.g., one-year) average PM(2.5) concentrations at a small number of widely-distributed monitoring sites would not show substantial variability, whereas short-term (e.g., 1-h) average measurements with high spatial density would show significant variability. Statistical analyses of ambient monitoring data as a function of wind speed and direction reinforce the significance of regional transport but show evidence of local contributions. We conclude that current monitor siting may not adequately capture PM(2.5) variability in an urban area, especially in a mega-city, reinforcing the necessity of dispersion modeling and methods for analyzing high-resolution monitoring observations.     

Halogenated organic contaminants and mercury in northern fulmars (Fulmarus glacialis): levels, relationships to dietary descriptors and blood to liver comparison

The northern fulmar (Fulmarus glacialis) is an interesting candidate for the study of patterns and levels of halogenated organic contaminants (HOCs) since they accumulate high levels of certain HOCs. In the present study we characterized a suite of established and novel HOCs in northern fulmars breeding on Bj?rn?ya in the Norwegian Arctic. A comparison between blood and liver HOC levels was made, and the levels were related to the ratios of heavier to lighter stable isotopes of nitrogen (15)N/(14)N (delta(15)N) and carbon (13)C/(12)C (delta(13)C) in muscle. A significant difference in congener patterns between blood and liver was found. The delta(13)C was not related to HOCs, neither in liver nor in blood. Weak correlations were found between delta(15)N and liver HOC levels. The 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQs) in northern fulmars were well above thresholds for reproductive effects in seabirds.