The selenium content of Welsh soils with special reference to bedrock and contamination from sulphide ores

This paper describes a survey of total selenium contents of surface soil samples in Wales. Samples were collected from three areas: over Silurian shales where deficiences in sheep have been reported, in an area severely affected by pollution from lead mining and in an area where black, marine shales outcrop. Selenium levels were low over the Silurian shales but high in the other two areas. Statistical analysis of the data permitted the separating out of a basal range of selenium values low enough to account for the reports of deficiences in sheep. Some selenium values were high enough to suggest the possibility of selenosis in sheep.     

Experimental prey species preferences of Hexaplex trunculus (Gastropoda: Muricidae) and predator–prey interactions with the Black mussel Mytilus galloprovincialis (Bivalvia: Mytilidae)

Hexaplex trunculus is one of the most widespread Mediterranean species of muricid gastropod and lives on rocky, sandy-mud and mud substrata. Although common in the Adriatic Sea, relatively little is known about its ecology especially feeding behaviour. The aim of this study was to explore the aspects of the feeding behaviour of H. trunculus using Arca noae, Modiolus barbatus and Mytilus galloprovincialis as experimental prey. Prey species preference, predator size, prey size choice, feeding rates, handling times and mode and place of attack were analysed. Typically, only M. galloprovincialis was attacked: A. noae rarely at the byssal gape and M. barbatus never. Small (40 mm) H. trunculus could not easily attack large M. galloprovincialis (65 mm) and preferred small (20 mm) and medium (35 mm) sized prey. Conversely, medium (55 mm) and large (70 mm) H. trunculus fed randomly on M. galloprovincialis of all three sizes. The feeding strategy adopted by H. trunculus individuals varied with respect to size. A tendency to drill the prey shell was recorded for small predators, whereas marginal chipping was adopted more frequently by large individuals. On average small, medium and large H. trunculus consumed 2.4±1.6 (range 0–4), 1.2±1.6 (range 0–4) and 2.0±2.1 (range 0–6) M. galloprovincialis, respectively. There was a statistically significant difference in prey-handling time with respect to the method of access adopted, predator and prey sizes. The time required to access a M. galloprovincialis individual by marginal chipping was considerably less than that required for drilling. H. trunculus consumed an average of 0.60±0.80 g M. galloprovincialis tissue dry weight over a 5-week period, that is, ~40% of its own tissue body weight. This translates to an average-sized (55 mm shell height) H. trunculus consuming ~18 M. galloprovincialis of 50 mm shell length (minimum marketable size) per year. H. trunculus showed no preference to drill either the left or right valves of M. galloprovincialis but generally attacked the posterior shell margin.     

Nitrate uptake by the reef coral Diploria strigosa: effects of concentration, water flow, and irradiance

The effects of several environmental variables on net nitrate uptake by the scleractinian coral Diploria strigosa were investigated under controlled flow conditions. D. strigosa exhibited nitrate uptake rates ranging from 1 to 5 nmol cm⁻² h⁻¹ at ambient concentrations of 0.1–0.3 μM that are typical of oligotrophic reefs such as Bermuda. Net uptake ceased at approximately 0.045 μM. The uptake was positively correlated with concentration up to a saturation concentration of approximately 3 μM. The uptake was also positively correlated with water velocity at 1 μM, but not at 6 μM, suggesting diffusional limitation at low concentrations and kinetic limitation at higher concentrations. Nitrate uptake by D. strigosa was not affected by light intensity or time of day, but was almost completely inhibited by 48 h exposure to ammonium levels found on many reefs.     

Field test of volatilization models

Four volatilization models were tested against field data from the Manchester Ship Canal and the River Main. The equations byMacKay andYeun, using Schmidt number and wind speed for the calculation of volatilization rate, were found to give the best results for the slowly flowing Ship Canal. Models using flow velocity grossly underestimated the real values for this waterway but were found to be superior for the faster flowing River Main. The results of this work indicate that volatilization models should be carefully chosen for a particular environmental situation. Additionally, the importance of the validation of such models against field data is emphasised.     

Species- and stage-specific differences in trace element tissue concentrations in amphibians: implications for the disposal of coal-combustion wastes

Information on species- and stage-specific patterns of contaminant accumulation is generally lacking for amphibians, yet such information could provide valuable knowledge on how amphibians interact with contaminants. We assessed concentrations of As, Cd, Cu, Ni, Pb, Se, Sr, and Zn in whole bodies of larval, recently metamorphosed, and adult life stages in Bufo terrestris and Rana sphenocephala from a site that currently receives coal combustion waste (CCW) discharge, a site where CCW was formerly discharged that has undergone natural attenuation for 30 years, and a nearby reference site. For the majority of elements (As, Cd, Cu, Ni, Pb, Zn), concentrations were highest in larvae, but Se and Sr concentrations remained elevated in later life stages, likely because these elements are S and Ca analogs, respectively, and are thus retained throughout structural changes during metamorphosis. Element concentrations were generally higher in B. terrestris than in R. sphenocephala. Concentrations of As, Se, and Sr were up to 11-35 times higher in metamorphs emigrating from CCW-polluted wetlands compared to unpolluted wetlands, suggesting metamorphosed amphibians can transport trace elements from aquatic disposal basins to nearby uncontaminated terrestrial habitats. In addition, anurans utilizing naturally revegetated sites up to 30 years after CCW disposal ceases are exposed to trace elements, although to a lesser degree than sites where CCW is currently discharged.     

Transfer of selenium from prey to predators in a simulated terrestrial food chain

Little is known about the accumulation and effects of selenium in reptiles. We developed a simplified laboratory food chain where we fed commercial feed laden with seleno-D,L-methionine (30 microg/g dry mass) to crickets (Acheta domestica) for 5-7 d. Se-enriched crickets (approximately 15 microg/g Se [dry mass]) were fed to juvenile male and female lizards (Sceloporus occidentalis) for 98 d while conspecifics were fed uncontaminated crickets. Lizards fed contaminated prey accumulated Se concentrations ranging from 9.3 (in female carcass) to 14.1 (in female gonad) microg/g compared to <1.5 microg/g in tissues of controls. Female gonad concentrations approached the highest of thresholds for reproductive toxicity in oviparous vertebrates. However, we observed no consistent effect of dietary treatment on sublethal parameters or survival. Our simplified food chain proved to be an ecologically relevant method of exposing lizards to Se, and forms the foundation for future studies on maternal transfer and teratogenicity of Se.     

Air quality and health benefits from potential coal power plant closures in Texas

As power production from renewable energy and natural gas grows, closures of some coal-fired power plants in Texas become increasingly likely. In this study, the potential effects of such closures on air quality and human health were analyzed by linking a regional photochemical model with a health impacts assessment tool. The impacts varied significantly across 13 of the state’s largest coal-fired power plants, sometimes by more than an order of magnitude, even after normalizing by generation. While some power plants had negligible impacts on concentrations at important monitors, average impacts up to 0.5 parts per billion (ppb) and 0.2 µg/m³ and maximum impacts up to 3.3 ppb and 0.9 µg/m³ were seen for ozone and fine particulate matter (PM_2.5), respectively. Individual power plants impacted average visibility by up to 0.25 deciviews in Class I Areas. Health impacts arose mostly from PM_2.5 and were an order of magnitude higher for plants that lack scrubbers for SO₂. Rankings of health impacts were largely consistent across the base model results and two reduced form models. Carbon dioxide emissions were relatively uniform, ranging from 1.00 to 1.26 short tons/MWh, and can be monetized based on a social cost of carbon. Despite all of these unpaid externalities, estimated direct costs of each power plant exceeded wholesale power prices in 2016.

Implications: While their CO₂ emission rates are fairly similar, sharply different NO_x and SO₂ emission rates and spatial factors cause coal-fired power plants to vary by an order of magnitude in their impacts on ozone, particulate matter, and associated health and visibility outcomes. On a monetized basis, the air pollution health impacts often exceed the value of the electricity generated and are of similar magnitude to climate impacts. This suggests that both air pollution and climate should be considered if externalities are used to inform decision making about power-plant dispatch and retirement.     

Comparisons of the dust/smoke particulate that settled inside the surrounding buildings and outside on the streets of southern New York City after the collapse of the World Trade Center, September 11, 2001

The collapse of the World Trade Center (WTC) on September 11, 2001, generated large amounts of dust and smoke that settled in the surrounding indoor and outdoor environments in southern Manhattan. Sixteen dust samples were collected from undisturbed locations inside two uncleaned buildings that were adjacent to Ground Zero. These samples were analyzed for morphology, metals, and organic compounds, and the results were compared with the previously reported outdoor WTC dust/smoke results. We also analyzed seven additional dust samples provided by residents in the local neighborhoods. The morphologic analyses showed that the indoor WTC dust/smoke samples were similar to the outdoor WTC dust/smoke samples in composition and characteristics but with more than 50% mass in the <53-microm size fraction. This was in contrast to the outdoor samples that contained >50% of mass above >53 microm. Elemental analyses also showed the similarities, but at lower concentrations. Organic compounds present in the outdoor samples were also detected in the indoor samples. Conversely, the resident-provided convenience dust samples were different from either the WTC indoor or outdoor samples in composition and pH, indicating that they were not WTC-affected locations. In summary, the indoor dust/smoke was similar in concentration to the outdoor dust/smoke but had a greater percentage of mass <53 microm in diameter.     

Effects on the function of Arctic ecosystems in the short- and long-term perspectives

Historically, the function of Arctic ecosystems in terms of cycles of nutrients and carbon has led to low levels of primary production and exchanges of energy, water and greenhouse gases have led to low local and regional cooling. Sequestration of carbon from atmospheric CO2, in extensive, cold organic soils and the high albedo from low, snow-covered vegetation have had impacts on regional climate. However, many aspects of the functioning of Arctic ecosystems are sensitive to changes in climate and its impacts on biodiversity. The current Arctic climate results in slow rates of organic matter decomposition. Arctic ecosystems therefore tend to accumulate organic matter and elements despite low inputs. As a result, soil-available elements like nitrogen and phosphorus are key limitations to increases in carbon fixation and further biomass and organic matter accumulation. Climate warming is expected to increase carbon and element turnover, particularly in soils, which may lead to initial losses of elements but eventual, slow recovery. Individual species and species diversity have clear impacts on element inputs and retention in Arctic ecosystems. Effects of increased CO2 and UV-B on whole ecosystems, on the other hand, are likely to be small although effects on plant tissue chemisty, decomposition and nitrogen fixation may become important in the long-term. Cycling of carbon in trace gas form is mainly as CO2 and CH4. Most carbon loss is in the form of CO2, produced by both plants and soil biota. Carbon emissions as methane from wet and moist tundra ecosystems are about 5% of emissions as CO2 and are responsive to warming in the absence of any other changes. Winter processes and vegetation type also affect CH4 emissions as well as exchanges of energy between biosphere and atmosphere. Arctic ecosystems exhibit the largest seasonal changes in energy exchange of any terrestrial ecosystem because of the large changes in albedo from late winter, when snow reflects most incoming radiation, to summer when the ecosystem absorbs most incoming radiation. Vegetation profoundly influences the water and energy exchange of Arctic ecosystems. Albedo during the period of snow cover declines from tundra to forest tundra to deciduous forest to evergreen forest. Shrubs and trees increase snow depth which in turn increases winter soil temperatures. Future changes in vegetation driven by climate change are therefore, very likely to profoundly alter regional climate.     

Bioleaching of zinc and copper from anaerobically digested swine manure: effect of sulfur levels and solids contents.

Anaerobically digested swine manure (ADSM) generally contains high concentrations of zinc (Zn) and copper (Cu). These metals levels exceed the land application regulations of municipal biosolids of many European countries and are on the borderline of exceptional quality in the U.S. Environmental Protection Agency (U.S. EPA) 40 CFR part 503 standards. From this perspective, a series of batch tests were conducted to evaluate the feasibility of bioleaching of Zn and Cu from ADSM so that the produced biosolids could safely be applied to land. The effect of different substrate levels (sulfur) and total solids content (as high as 9%) on metal solubilization was investigated. The results showed that metal solubilization efficiency for both Zn and Cu declined significantly with an increase in total solids from 3 to 6% and then to 9% at the same substrate level. Metal solubilization increased proportionately with increases in substrate concentration up to 6% of total solids content. However, at 9% total solids content, metal solubilization was insignificant at all substrate levels tested. At a 6% total solids level and 10 000 mg/L of substrate, 94% of Zn and 72% of Cu were solubilized. Bioleaching was also found to be effective in destruction of pathogens with approximately 2.5 log-scale reduction. The residual biosolid was found to meet the Class A biosolids standands of U.S. EPA 40 CFR part 503.