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.     

Coping with uncertainty: a call for a new science-policy forum

The scientific and policy worlds have different goals, which can lead to different standards for what constitutes "proof" of a change or phenomena, and different approaches for characterizing and conveying uncertainty and risk. These differences can compromise effective communication among scientists, policymakers, and the public, and constrain the types of socially compelling questions scientists are willing to address. In this paper, we review a set of approaches for dealing with uncertainty, and illustrate some of the errors that arise when science and policy fail to coordinate correctly. We offer a set of recommendations, including restructuring of science curricula and establishment of science-policy forums populated by leaders in both arenas, and specifically constituted to address problems of uncertainty.     

Concentrations of dioxin-like PCB congeners in unweathered Aroclors by HRGC/HRMS using EPA Method 1668A

We have determined the congener compositions of nine commercial Aroclor products of polychlorinated biphenyls (PCBs) to the sub-part-per-million level using high-resolution gas chromatography combined with high-resolution mass spectrometry according to US Environmental Protection Agency (EPA) Method 1668A. These Aroclor composition data should allow improved characterization and risk assessment of PCB contamination at hazardous waste sites, particularly for dioxin-like PCB congeners. By combining the data on the concentrations of each dioxin-like congener with its World Health Organization toxicity equivalency factor, we have established dioxin toxic equivalent concentrations for each pure Aroclor product.     

Monitoring trichloroethene remediation at an iron permeable reactive barrier using stable carbon isotopic analysis

Stable carbon isotopic analysis, in combination with compositional analysis, was used to evaluate the performance of an iron permeable reactive barrier (PRB) for the remediation of ground water contaminated with trichloroethene (TCE) at Spill Site 7 (SS7), F.E. Warren Air Force Base, Wyoming. Compositional data indicated that although the PRB appeared to be reducing TCE to concentrations below treatment goals within and immediately downgradient of the PRB, concentrations remained higher than expected at wells further downgradient (i.e. >9 m) of the PRB. At two wells downgradient of the PRB, TCE concentrations were comparable to upgradient values, and delta13C values of TCE at these wells were not significantly different than upgradient values. Since the process of sorption/desorption does not significantly fractionate carbon isotope values, this suggests that the TCE observed at these wells is desorbing from local aquifer materials and was present before the PRB was installed. In contrast, three other downgradient wells show significantly more enriched delta13C values compared to the upgradient mean. In addition, delta13C values for the degradation products of TCE, cis-dichloroethene and vinyl chloride, show fractionation patterns expected for the products of the reductive dechlorination of TCE. Since concentrations of both TCE and degradation products drop to below detection limit in wells within the PRB and directly below it, these downgradient chlorinated hydrocarbon concentrations are attributed to desorption from local aquifer material. The carbon isotope values indicate that this dissolved contaminant is subject to local degradation, likely due to in situ microbial activity.     

Threats to Imperiled Freshwater Fauna

Threats to imperiled freshwater fauna in the U.S. were assessed through an experts survey addressing anthropogenic stressors and their sources. Specifically, causes of historic declines and current limits to recovery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The survey was designed to identify threats with sufficient specificity to inform resource managers and regulators faced with translating information about predominant biological threats into specific, responsive actions. The findings point to altered sediment loads and nutrient inputs from agricultural nonpoint pollution; interference from exotic species; and altered hydrologic regimes associated with impoundment operations as the three leading threats nationwide, accompanied by many lesser but still significant threats. Variations in threats among regions and among taxa were also evident. Eastern species are most commonly affected by altered sediment loads from agricultural activities, whereas exotic species, habitat removal/damage, and altered hydrologic regimes predominate in the West. Altered sediment loading from agricultural activities and exotic species are dominant problems for both eastern mussels and fishes. However, eastern fishes also appear to be suffering from municipal nonpoint pollution (nutrients and sediments), whereas eastern mussels appear to be more severely affected by altered nutrient impacts from hydroelectric impoundments and agricultural runoff. Our findings suggest that control of nonpoint source pollution associated with agriculture activities should be a very high priority for agricultural producers and governmental support programs. Additonally, the large number of hydropower dams in the U.S. subject to federal re-licensing in coming years suggests a significant opportunity to restore natural hydrologic regimes in the affected rivers.     

Instructions for Authors

Instructions for Authors

Instructions for Authors