Nitrogen oxides emission control options for coal-fired electric utility boilers

Recent regulations have required reductions in emissions of nitrogen oxides (NOx) from electric utility boilers. To comply with these regulatory requirements, it is increasingly important to implement state-of-the-art NOx control technologies on coal-fired utility boilers. This paper reviews NOx control options for these boilers. It discusses the established commercial primary and secondary control technologies and examines what is being done to use them more effectively. Furthermore, the paper discusses recent developments in NOx controls. The popular primary control technologies in use in the United States are low-NOx burners and overfire air. Data reflect that average NOx reductions for specific primary controls have ranged from 35% to 63% from 1995 emissions levels. The secondary NOx control technologies applied on U.S. coal-fired utility boilers include reburning, selective noncatalytic reduction (SNCR), and selective catalytic reduction (SCR). Thirty-six U.S. coal-fired utility boilers have installed SNCR, and reported NOx reductions achieved at these applications ranged from 15% to 66%. Recently, SCR has been installed at >150 U.S. coal-fired utility boilers. Data on the performance of 20 SCR systems operating in the United States with low-NOx emissions reflect that in 2003, these units achieved NOx emission rates between 0.04 and 0.07 lb/10(6) Btu.     

Vascular plant extinction in the continental United States and Canada

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.     

A method for the isolation of microorganisms producing extracellular long-side-chain poly (β-hydroxyalkanoate) depolymerase

A simple method was developed for the preparation of an autoclavable, long-side-chain poly (-hydroxyalkanoate) (LSC-PHA) colloidal suspension, which was used as a substrate for enzymatic degradation and to prepare agar overlay plates for the isolation of microorganisms producing extracellular LSC-PHA depolymerase. Six cultures producing extracellular LSC-PHA depolymerase were isolated from a composted hydrocarbon-contaminated soil. All were pseudomonads or related bacteria. All (with the possible exception ofXanthomonas maltophilia) could produce LSC PHA. Except forX. maltophilia none could hydrolyze poly (-hydroxybutyrate). Screening of sevenPseudomonas strains known to accumulate LSC PHA showed that all were negative for extracellular LSC-PHA depolymerase production. It was concluded that extracellular LSC-PHA depolymerase producers are found mostly in the genusPseudomonas but that they are relatively uncommon.     

Migration of aluminum from food contact materials to food—a health risk for consumers? Part I of III: exposure to aluminum,release of aluminum,tolerable weekly intake (TWI), toxicological effects of aluminum,study design,and methods

Background

In spite of the prevalence of aluminum in nature, no organism has been found to date which requires this element for its biological functions. The possible health risks to human beings resulting from uptake of aluminum include detrimental effects to the hemopoietic system, the nervous system and bones. Aluminum is used in many fields and occurs in numerous foodstuffs. Food contact materials containing aluminum represent an anthropogenic source of dietary aluminum.

Results

As a result of their frequent use in private households a study was undertaken to detect migration of this metal to foodstuffs from drink containers, coffee pots, grill pans, and camping cookware made of aluminum.

Conclusions

An estimate of the health risk to consumers is calculated, based on the tolerable weekly intake (TWI) specified by the European Food Safety Authority of 1 mg/kg body weight for all groups of people. In some instances the TWI is significantly exceeded, dependent upon the food contact material and the food itself.

     

Hierarchical regulation of nitrogen export from urban catchments: interactions of storms and landscapes.

In urban catchments of arid central Arizona, we investigate how the export of mineral and organic nitrogen (N) in storm runoff is regulated by interactions between local landscape characteristics and broader scale storm features. First, we test whether N export is more a function of (1) processes that affect N concentration in runoff or (2) the propensity of the catchment to convey rainfall as runoff. With data pooled across catchments, the mass of N in export (load) is determined by processes regulating runoff N concentration. There are exceptions when catchments are examined individually, where N load from some catchments is determined by the hydrologic responsiveness of the catchment. Second, we investigate the relationship between N export and catchment features. Loads per catchment area were greater from more impervious catchments, probably because impervious catchments held more N in a mobilizable phase and conveyed more rainfall as overland flow. Loads per area were lower from larger catchments, possibly owing to more N-retention hot spots in larger catchments. Catchments with the greatest N exports were those with commercial land use, and loads decreased as development became less prevalent or as residential replaced industrial land use. Third, we investigated how catchment features moderated direct responses of N export to storms. Export was less correlated with storm features in catchments that were larger, more pervious, and less industrial. Results support an "N build and flush" hypothesis, which purports that there is little biotic processing of N deposited to arid, urban surfaces with little organic matter. The rate and duration of deposition determine the size of the mobile N pool. Any amount of rainfall capable of generating overland flow would entrain nearly all mobilizable N and export it from the catchment. Nonetheless, these results suggest that, even with daunting seasonal and interannual variability in storm conditions, material export can be reduced by managing intrinsic catchment features.     

Population Declines and Priorities for Amphibian Conservation in Latin America

Abstract: Although dramatic amphibian population declines have been reported worldwide, our understanding of the extent of the declines in Latin America, where amphibian diversity is high, is limited to a few well-documented studies. To better understand the geographic extent of declines, their possible causes, and the measures needed to improve Latin American scientists' ability to research the phenomenon and make effective management recommendations, we convened three regional workshops with 88 Latin American herpetologists and conservationists. Population declines are widespread in Latin America. At least 13 countries have experienced declines, and in 40 cases species are now thought to be extinct or extirpated in a country where they once occurred. Declines or extinctions have affected 30 genera and nine families of amphibians. Most declines have occurred in remote highlands, above 500 m in elevation in Central America and above 1000 m in the Andes. Most documented declines occurred in the 1980s. Of the possible causes studied to date, climate change appears to be important at one site and chytrid fungal disease has been identified at sites in three countries. Although many monitoring studies are currently underway in a variety of habitats, most studies are recent and of short duration. In a signed resolution, workshop participants called for greater collaboration and communication among scientists working in Latin America to understand the geographic extent of population declines and the distribution of possible causal factors. In situ conservation is important to protect habitats, but captive-rearing programs for species subject to imminent extinction are also needed. Better understanding of the taxonomy and natural history of amphibians and more funding for research and monitoring are critical to developing a scientific basis for management action to arrest and reverse population declines.     

Measures of energy cost and value in ecosystems

The physical output of ecological processes have different values even though they may be measured in the same physical units. Using linear input-output theory, we derive a set of weights based on direct and indirect energy requirements for ecosystem commodities which uniquely converts them into commensurable unit costs. Under certain conditions, these costs are equal to values or prices. Using this system, behavioral theories can be better posed for experimental verification.     

Ecological investigations with the undulating oceanographic recorder: The hydrography and plankton of the waters adjacent to the Orkney and Shetland Islands

This paper describes the results of a survey of the North Sea and north Atlantic waters adjacent to the Orkney and Shetland Islands, from 23 May to 9 June, 1973, using simultaneous tows of the prototype Undulating Oceanographic Recorder (UOR) and the Continuous Plankton Recorder (CPR). The UOR sampled plankton and measured salinity and temperature over its undulation profile from 5 to 65 m in depth. The CPR sampled plankton at a fixed depth of 10 m. Three principal water masses were identified, each with a characteristic plankton community.     

A framework of connections between soil and people can help improve sustainability of the food system and soil functions

Globally soil quality and food security continue to decrease indicating that agriculture and the food system need to adapt. Improving connection to the soil by knowledge exchange can help achieve this. We propose a framework of three types of connections that allow the targeting of appropriate messages to different groups of people. Direct connection by, for example, handling soil develops soil awareness for management that can be fostered by farmers joining groups on soil-focused farming such as organic farming or no-till. Indirect connections between soil, food and ecosystem services can inform food choices and environmental awareness in the public and can be promoted by, for example, gardening, education and art. Temporal connection revealed from past usage of soil helps to bring awareness to policy workers of the need for the long-term preservation of soil quality for environmental conservation. The understanding of indirect and temporal connections can be helped by comparing them with the operations of the networks of soil organisms and porosity that sustain soil fertility and soil functions.     

Woodlot management and livelihoods in a tropical conservation landscape

In biodiversity hotspots, there is often tension between human needs and conservation, exacerbated when protected areas prevent access to natural resources. Forest-dependent people may compensate for exclusion by managing unprotected forests or cultivating planted woodlots. Outside Bwindi Impenetrable National Park in Uganda, household wood product needs are high and population growth puts pressure on the environment. We investigated the role of privately and collectively managed woodlots in provisioning wood products and supporting local livelihoods. We found that households relied heavily on woodlots for daily needs and as resources during time of need. We also found that locally relevant social institutions, called stretcher groups, played a role in the management of woodlots, providing shared community resources. Privately and collectively owned woodlots support local livelihoods and wood product needs in the region. Long-term management of forests in Uganda should consider the value of woodlots and the mechanisms required to support them.