Geographic distribution of selected elements in the livers of polar bears from Greenland, Canada and the United States

To assess geographic distributions of elements in the Arctic we compared essential and non-essential elements in the livers of polar bears (Ursus maritimus) collected from five regions within Canada in 2002, in Alaska between 1994 and 1999 and from the northwest and east coasts of Greenland between 1988 and 2000. As, Hg, Pb and Se varied with age, and Co and Zn with gender, which limited spatial comparisons across all populations to Cd, which was highest in Greenland bears. Collectively, geographic relationships appeared similar to past studies with little change in concentration over time in Canada and Greenland for most elements; Hg and Se were higher in some Canadian populations in 2002 as compared to 1982 and 1984. Concentrations of most elements in the polar bears did not exceed toxicity thresholds, although Cd and Hg exceeded levels correlated with the formation of hepatic lesions in laboratory animals.     

Roles of SO2 oxidation in new particle formation events

The oxidation of SO₂ is commonly regarded as a major driver for new particle formation (NPF) in the atmosphere. In this study, we explored the connection between measured mixing ratio of SO₂ and observed long-term (duration > 3 hr) and short-term (duration < 1.5 hr) NPF events at a semi-urban site in Toronto. Apparent NPF rates (J₃₀) showed a moderate correlation with the concentration of sulfuric acid ([H₂SO₄]) calculated from the measured mixing ratio of SO₂ in long-term NPF events and some short-term NPF events (Category I) (R² = 0.66). The exponent in the fitting line of J₃₀ ~ [H₂SO₄]ⁿ in these events was 1.6. It was also found that SO₂ mixing ratios varied a lot during long-term NPF events, leading to a significant variation of new particle counts. In the SO₂-unexplained short-term NPF events (Category II), analysis showed that new particles were formed aloft and then mixed down to the ground level. Further calculation results showed that sulfuric acid oxidized from SO₂ probably made a negligible contribution to the growth of > 10 nm new particles.     

The Contributions of Open Sources to Ambient TSP Levels

A companion paper showed that the annual (1976) emissions of particles from open sources, those sources too great in extent to control through enclosure or ducting, in the U.S. were over 500 × 10⁶ tons. Here it is demonstrated that on the average, a single open source class (unpaved roads) contributes 1.2 times as much to the variability of statewide-averaged measured annual mean TSP levels as all conventional sources. The nine other major open source classes do not appear to contribute significantly to measured TSP levels, due to patterns of source and monitor location. Although, on the average, the total contributions of unpaved roads to TSP are larger than conventional source contributions, the per ton contributions are only approximately one-ninth as great. Both precipitation frequency and adjacent states’ TSP levels are found to be stronger determinants of the between-state variability in TSP levels than conventional open source emissions. Several states, including NM, IL, AL, NJ, PA, CA, ID, ND, Rl, DE, CT, and WV (depending upon criterion of importance) are identified for further research on the feasibility, practicality, importance, and cost-effectiveness of control of emissions of dust from unpaved roads.     

Trace Element Inputs from a Coal Burning Power Plant to Adjacent Terrestrial and Aquatic Environments

Inputs of trace elements derived from coal ash to terrestrial and aquatic environments were investigated near an 83 MW coal-burning power plant. Comparisons were made between terrestrial inputs of trace elements through aerial deposition during 23 years before installation of electrostatic precipitators and aquatic inputs from ash disposal basins after installation. A gaussian plume model was used to predict deposition patterns of 29 trace elements in coal ash about the power plant. Detectable increases of only Sr, As, Sb, and Be in surface soils within 3 km of the power plant were predicted. Concentrations measured in surface soils were largely consistent with these predictions. Measurements of aerial deposition of Cd, Pb, Cu, and Mn at a site 5.5 km distant were similar to those in other rural areas and indicated that little of the measured Cd, Cu, Mn, or Pb was derived from fly ash. Concentrations of 12 heavy metals in effluents from the basin receiving ash were comparable to those predicted in rainfall deposited nearest the plant. It is concluded that at other coal combustion facilities, basin disposal could be a more serious contamination threat to aquatic environments than aerial dispersal of ash.     

The Value of Monitoring for Radon in the Home: A Decision Analysis

In light of the recent publicity about the adverse health effects of radon gas, many citizens and government officials are considering whether or not to monitor for radon in homes. This paper presents a formal decision analysis of the monitoring dilemma from the perspective of hypothesized homeowners. The analysis considers the costs of radon monitoring and control, the carcinogenic risks of radon exposure, the demographics of household size, and a hypothetical homeowner's knowledge of radon exposure levels—with and without the benefit of specific monitoring data. Since monitoring every home in the United States would be quite expensive, the analysis reveals some more efficient monitoring strategies that might be employed by citizens and government officials. While the paper presents a new analytic perspective in the monitoring problem, the results should not be considered definitive. Further study is necessary to clarify precisely what is known about radon exposure, health effects, and control strategies.     

Canister-Based Method for Monitoring Toxic VOCs in Ambient Air

The availability of reliable, accurate and precise monitoring methods for toxic volatile organic compounds (VOCs) is a primary need for state and local agencies addressing daily monitoring requirements related to odor complaints, fugitive emissions, and trend monitoring. The canister-based monitoring method for VOCs is a viable and widely used approach that is based on research and evaluation performed over the past several years. This activity has involved the testing of sample stability of VOCs in canisters and the design of time-integrative samplers. The development of procedures for analysis of samples in canisters, including the procedure for VOC preconcentration from whole air, the treatment of water vapor in the sample, and the selection of an appropriate analytical finish has been accomplished. The canister-based method was initially summarized in the EPA Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air as Method TO-14. Modifications and refinements are being added to Method TO-14 in order to obtain a Statement of Work for the Superfund Contract Laboratory Program for Air. This paper discusses the developments leading to the current status of the canisterbased method and provides a critique of the method using results obtained in EPA monitoring networks.     

Jointly estimating survival and mortality: integrating recapture and recovery data from complex multiple predator systems

Environmental and Ecological Statistics - Identifying where, when, and how many animals live and die over time is principal to understanding factors that influence population dynamics....     

Habitat patch shape, not corridors, determines herbivory and fruit production of an annual plant

Habitat corridors confer many conservation benefits by increasing movement of organisms between habitat patches, but the benefits for some species may exact costs for others. For example, corridors may increase the abundance of consumers in a habitat to the detriment of the species they consume. In this study we assessed the impact of corridors on insect herbivory of a native plant, Solanum americanum, in large-scale, experimentally fragmented landscapes. We quantified leaf herbivory and assessed fruit production as a proxy for plant fitness. We also conducted field surveys of grasshoppers (Orthoptera), a group of abundant, generalist herbivores that feed on S. americanum, and we used exclosure cages to explicitly link grasshopper herbivory to fruit production of individual S. americanum. The presence of corridors did not increase herbivory or decrease plant fruit production. Likewise, corridors did not increase grasshopper abundance. Instead, patches in our landscapes with the least amount of edge habitat and the greatest amount of warmer "core" area had the highest levels of herbivory, the largest cost to plant fruit production as a result of herbivory, and the most grasshoppers. Thus habitat quality, governed by patch shape, can be more important than connectivity for determining levels of herbivory and the impact of herbivory on plant fitness in fragmented landscapes.     

A simplified computational analysis of turbulent plumes and jets

The application of computational fluid dynamics (CFD), particularly Large Eddy Simulation, for the modelling of buoyant turbulent plumes, has been demonstrated to be very accurate, but computationally expensive. Here a more basic, and therefore more generally practicable, approach is presented. Commercial CFD software is used to model such plumes using Reynolds-Averaged Navier-Stokes (RANS) turbulence models. A careful comparison is made between the numerical predictions and well-established results regarding the bulk properties of plumes. During this process, we are able to observe the well-known approximate Gaussian nature of the plume and achieve quantitative agreement with empirical plume spread coefficients. The use of numerical modelling allows for the investigation of the flow field and turbulence in those regions of the plume of most interest—the plume edge and near source regions. A comprehensive sensitivity study is conducted to identify the limits of applicability of this modelling approach. It is shown that the standard modelling approach of Morton, Taylor and Turner, which introduced the well-known entrainment assumption, pertains in a region well above the source region. At the plume edge, the levels of turbulence are contrasted with the value of the entrainment parameter. Finally, the effects of forcing the plumes with additional momentum at the source are considered, including the case of a pure jet. We show how these forced plumes eventually lose their momentum excess and tend to the behaviour of a pure, buoyant plume.