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.     

Batch reactor kinetic studies on the reductive dechlorination of chlorinated ethylenes by tetrakis-(4-sulfonatophenyl)porphyrin cobalt

Tetrakis-(4-sulfonatophenyl)porphyrin cobalt was identified as a highly-active reductive dechlorination catalyst for chlorinated ethylenes. Through batch reactor kinetic studies, degradation of chlorinated ethylenes proceeded in a step-wise fashion with the sequential replacement of Cl by H. For perchloroethylene (PCE) and trichloroethylene (TCE), the dechlorination products were quantified and the C₂ mass was accounted for. Degradation of the chlorinated ethylenes was found to be first-order in substrate. Dechlorination trials with increasing catalyst concentration showed a linearly increasing pseudo first-order rate constant which yielded rate laws for PCE and TCE degradation that are first-order in catalyst. The dechlorination activity of this catalyst was compared to that of another water-soluble cobalt porphyrin under the same reaction conditions and found to be comparable for PCE and TCE.     

Characterizing the trophy hunting debate on Twitter

Social media is an arena of debate for contentious political and social topics. One conservation topic debated online is the acceptability of trophy hunting, a debate that has implications for national and international policy. We used a mixed-methods approach (grounded theory and quantitative clustering) to identify themes in the trophy hunting debate on Twitter. We examined commonly co-occurring categories that describe people's stances on trophy hunting. We identified 12 categories and 4 preliminary archetypes opposing trophy hunting—activism, scientific, condemning, and objecting—whose opposition derived from different moral reasoning. Few tweets (22) in our sample of 500 supported trophy hunting, whereas 350 opposed it. The debate was hostile; 7% of tweets in our sample were categorized as abusive. Online debates can be unproductive, and our findings may be important for stakeholders wishing to effectively engage in the trophy hunting debate on Twitter. More generally, we contend that because social media is increasingly influential, it is important to formally contextualize public responses to contentious conservation topics in order to aid communication of conservation evidence and to integrate diverse public perspectives in conservation practice.     

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.     

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....     

Importance of macroalgal fields as coral reef fish nursery habitat in north-west Australia

Macroalgal fields are a feature of the shallow tropical benthos, yet their importance for coral reef fish population dynamics remains poorly understood. The abundance of fish recruits was recorded using underwater visual census at six macroalgal and 11 coral reef sites in the Montebello and Barrow Islands. Surveys identified 6,935 individual recruit fish from 105 species, 54 genera and 20 families. Of these, 1,401 recruits from 48 species, 31 genera and 14 families were observed in macroalgal sites. Sixteen of the 105 recruit species (15.2 %) were observed exclusively at macroalgal sites. Forty-two (87.5 %) of these species have been observed as adults on adjacent coral reefs. Species composition of fish recruits differed significantly between the two habitats. Corallivore, small omnivore and zooplanktivore recruits had significantly higher numbers in the coral sites, while the results clearly demonstrate that juveniles, within the genera Lethrinus and Choerodon, as well as large algal croppers, are predominantly found at macroalgal (74–100 %) rather than coral-dominated sites. High-canopy macroalgae cover was positively correlated with abundance of these taxa, particularly Lethrinids (r ² = 0.40). This study is the first to highlight the important attributes of tropical macroalgal fields and suggests that they have a similar role to seagrass meadows as essential juvenile habitat, thus warranting greater attention in conservation planning and ecological studies.     

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.