Spatio-temporal prediction of atmospheric benzene (Part I)

Benzene is a carcinogenic and genotoxic pollutant which mainly affects the people health through the inhalation. Nevertheless, this pollutant is not frequently measured by air-quality networks. To solve this problem, some models have been published to estimate benzene concentrations in the atmosphere. However, the lack of measures makes difficult the application of complex models in order to get a detailed spatio-temporal analysis, namely in urban areas. In this work was developed a simple semi-empirical model to predict benzene concentrations based on the ratio of benzene and carbon monoxide concentrations in order to predict the concentrations of this pollutant in large areas and periods with lack of benzene measurements but with higher impact in the human health. The model was applied to an urban area, the Metropolitan Area of Oporto, for a period of 12 years (1995–2006). Monthly correlations between benzene and carbon monoxide concentrations at Custóias air-quality station are significant (p = 0.01) and higher in winter (r _s > 0.7) than in summer (0.3 > r _s > 0.7). Estimate of the monthly ratio of the concentration of these two pollutants range between 199 and 305. The methodology validation shows good results (r _s = 0.81) which allow, assuming the availability of carbon monoxide data, the use of this tool for areas with low benzene recorded data. The application of this methodology in the study area shows an annual average trend decrease of benzene concentrations during the study period, which may be linked to a general trend decrease of benzene emissions in European urban areas, including the study domain.     

Twenty-year inter-annual trends and seasonal variations in precipitation and stream water chemistry at the Bear Brook Watershed in Maine, USA

Mean annual concentration of ${\textrm{SO}}_{4}^{2-}$ in wet-only deposition has decreased between 1988 and 2006 at the paired watershed study at Bear Brook Watershed in Maine, USA (BBWM) due to substantially decreased emissions of SO₂. Emissions of NO_x have not changed substantially, but deposition has declined slightly at BBWM. Base cations, ${\textrm{NH}}_{4}^{+}$ , and Cl^??? concentrations were largely unchanged, with small irregular changes of <1 μeq L^???1 per year from 1988 to 2006. Precipitation chemistry, hydrology, vegetation, and temperature drive seasonal stream chemistry. Low flow periods were typical in June–October, with relatively greater contributions of deeper flow solutions with higher pH; higher concentrations of acid-neutralizing capacity, Si, and non-marine Na; and low concentrations of inorganic Al. High flow periods during November–May were typically dominated by solutions following shallow flow paths, which were characterized by lower pH and higher Al and DOC concentrations. Biological activity strongly controlled ${\textrm{NO}}_{3}^{-}$ and K^?+?. They were depressed during the growing season and elevated in the fall. Since 1987, East Bear Brook (EB), the reference stream, has been slowly responding to reduced but still elevated acid deposition. Calcium and Mg have declined fairly steadily and faster than ${\textrm{SO}}_{4}^{2-}$ , with consequent acidification (lower pH and higher inorganic Al). Eighteen years of experimental treatment with (NH₄)₂SO₄ enhanced acidification of West Bear Brook’s (WB) watershed. Despite the manipulation, ${\textrm{NH}}_{4}^{+}$ concentration remained below detection limits at WB, while leaching of ${\textrm{NO}}_{3}^{-}$ increased. The seasonal pattern for ${\textrm{NO}}_{3}^{-}$ concentrations in WB, however, remained similar to EB. Mean monthly concentrations of ${\textrm{SO}}_{4}^{2-}$ have increased in WB since 1989, initially only during periods of high flow, but gradually also during base flow. Increases in mean monthly concentrations of Ca^2?+?, Mg^2?+?, and K^?+? due to the manipulation occurred from 1989 until about 1995, during the depletion of base cations in shallow flow paths in WB. Progressive depletion of Ca and Mg at greater soil depth occurred, causing stream concentrations to decline to pre-manipulation values. Mean monthly Si concentrations did not change in EB or WB, suggesting that the manipulation had no effect on mineral weathering rates. DOC concentrations in both streams did not exhibit inter- or intra-annual trends.     

Radioactive fallout in the United States due to the Fukushima nuclear plant accident

The release of radioactivity into the atmosphere from the damaged Fukushima Daiichi nuclear power plant started on March 12th, 2011. Among the various radionuclides released, iodine -131 ((131)I) and cesium isotopes ((137)Cs and (134)Cs) were transported across the Pacific Ocean and reached the United States on 17-18 March 2011. Consequently, an elevated level of fission products (131)I, (132)I, (132)Te, (134)Cs and (137)Cs were detected in air, water, and milk samples collected across the United States between March 17 and April 4, 2011. The continuous monitoring of activities over a period of 25 days and spatial variations across more than 100 sampling locations in the United States made it possible to characterize the contaminated air masses. For the entire period, the highest detected activity values ranged from less than 1 m Bq m(-3) to 31 m Bq m(-3) for the particulate (131)I, and up to 96 m Bq m(-3) for the gaseous (131)I fraction.     

Method of median semi-variance for the analysis of left-censored data: Comparison with other techniques using environmental data

In environmental monitoring, variables with analytically non-detected values are commonly encountered. For the statistical evaluation of these data, most of the methods that produce a less biased performance require specific computer programs. In this paper, a statistical method based on the median semi-variance (SemiV) is proposed to estimate the position and spread statistics in a dataset with single left-censoring. The performances of the SemiV method and 12 other statistical methods are evaluated using real and complete datasets. The performances of all the methods are influenced by the percentage of censored data. In general, the simple substitution and deletion methods showed biased performance, with exceptions for L/2, Inter and L/√2 methods that can be used with caution under specific conditions. In general, the SemiV method and other parametric methods showed similar performances and were less biased than other methods. The SemiV method is a simple and accurate procedure that can be used in the analysis of datasets with less than 50% of left-censored data.     

Protecting Sensitive Coastal Areas with Exclusion Booms during Oil Spill Events

Oil spills at sea remain a serious threat to coastal settlements and sensitive ecosystems. Although the impacts of spills are contingent upon a variety of environmental factors and the chemical composition of the oil itself, spill effects can be long lasting in the pelagic zone with broad impacts on sensitive bacterial, microbial, plant, and animal communities. Efforts to contain, deflect, protect, and mitigate the effects of oil are increasingly important, given the massive social, economic, and environmental fallout connected to large spills. The purpose of this paper is to provide geographic perspective for protecting coastal areas with exclusion booms during oil spill events. Specifically, we introduce a generalized, extendable, spatial optimization model that simultaneously minimizes spill effects on vulnerable shorelines and the total costs associated with dispatching booms. The multiobjective model is solved with a weighting method to produce a Pareto optimal curve that reveals how the costs and protection operations change under different priorities. A simulated tanker spill near Mobile Bay, AL, USA, is used as an illustrative example.

     

The Great Recession or progressive energy policies? Explaining the decline in US greenhouse gas emissions forecasts

This paper evaluates the causes of the 23% decline in 2030 US greenhouse gas emissions forecasts between 2007 and 2011. Dynamic regression modeling predicts that the Great Recession contributed to about 67% of the 2008–2009 emissions decline, but then fell to about an 18% share for the 2030 emissions forecast. An analysis of electricity generation forecasts show that switching from coal to gas contributed only 6% to the total 2030 decline. In contrast, regulatory impact assessments and policy analysis showed that state and federal policies were responsible for 46% of the 2030 decline in emissions.     

The Chemical and Meteorological Conditions Associated with High and Low Ozone Concentrations in Southeastern Michigan and Nearby Areas of Ontario

This analysis represents the first characterization of the photochemistry and transport of ozone in the Detroit metropolitan area and provides a basis for comparing data for Detroit to that for other cities. The characterization is based on a comprehensive set of meteorological and chemical measurements obtained at a site in the urban core of Detroit during the summer of 1981, together with measurements of O₃, nitrogen oxides (NO _X ), and nonmethane organic compounds (NMOC) from rural, suburban, and urban areas in southeastern Michigan and adjacent areas of Ontario.

For the quartile (23 days) with highest ozone maxima (97-180 ppb), the maxima occurred 10-70 km north-northeast of the city on days that were warm and hazy with light southsouthwest winds. On such days there was a marked accumulation of ozone precursors (NMOC and NO_X) in the early morning, as well as a rapid chemical removal of NO _X (NO _X half-life of ～5 h) from morning to midday. The timing of the daily ozone increase across the study region suggests that local photochemical generation in a moving plume was responsible for more than half of the ozone measured downwind. However, there was also evidence that ozone transported into Detroit as part of the regional background was a significant part of the O₃ maxima on high ozone days. The average contributions of photochemistry and transport for the 23 days with the highest ozone maxima were estimated to be 57 ppb and 47 ppb, respectively.     

Measurements of Sulfur Oxides,Nitrogen Oxides,Haze and Fine Particles at a Rural Site on the Atlantic Coast

During August, 1982 and January and February, 1983, General Motors Research Laboratories operated air monitoring sites on the Atlantic Coast near Lewes, Delaware and 1250 km to the east on the southwest coast of Bermuda. The overall purpose of this project was to study the transformations of the principal acid precipitation precursors, NO _x and SO _x species, as they transport under conditions not complicated by emissions from local sources. In this paper, the measurements of gas and particulate species from Lewes are described and the composition and sources of sulfate aerosol, which is the most important haze-producing species, are investigated.

On the average, the total suspended particulate (TSP) concentration was 27.9 μg/m³ while the PM₁₀ (mass of particles with a diameter less than or equal to 10 μm) concentration was 22.0 μg/m³ or 79 percent of the TSP. The PM₁₀ consisted of 6.1 μg/m³ of coarse particles (CPM, diameter = 2.5 ? 10μm) and 15.9 μg/m³ of fine particles (FPM, diameter < 2.5 μm).

On a mass basis the most important constituents of the fine particulate fraction were sulfate compounds, 50 percent, and organic compounds, 30 percent. The mean light extinction coefficient corresponds to a visual range of 18-20 km. Most of the extinction can be attributed to the sulfate (60 percent) and organic carbon (13 percent). Particle size measurements show that the mass median aerodynamic diameter for both species is 0.43 μm. This is a typical size for a hydrated sulfate aerosol. For carbon, however, this is a larger size than previously reported and results in a more efficient light scattering aerosol. Principal component analyses indicate that coal combustion emissions from the midwestern U.S. are the most significant source of sulfate in Lewes during the summer and winter.     

Expanding the range of halogenated 1'-methyl-1,2'-bipyrroles (MBPs) using GC/ECNI-MS and GCxGC/TOF-MS

Halogenated 1'methyl-1,2'-bipyrroles (MBPs) have been identified worldwide in marine mammals. Here we present the tentative identification of previously undetected MBP congeners in Delpinus delphis blubber using gas chromatography/electron capture negative ion mass spectrometry (GC/ECNI-MS) and comprehensive two-dimensional gas chromatography/time of flight mass spectrometry (GCxGC/TOF-MS). This is the first report of 26 congeners. The presence of numerous partially halogenated congeners suggests that they are either biosynthesized concomitantly with their perhalogenated counterparts or that their dehalogenation products can also bioaccumulate. The newly found compounds fit the geographic trend that has been previously noted. That is, samples from the Atlantic Ocean are dominated by the more brominated congeners while those from the Pacific are dominated by the more chlorinated congeners.     

Effects of decadal exposure to interacting elevated CO2 and/or O3 on paper birch (Betula papyrifera) reproduction

We studied the effects of long-term exposure (nine years) of birch (Betula papyrifera) trees to elevated CO(2) and/or O(3) on reproduction and seedling development at the Aspen FACE (Free-Air Carbon Dioxide Enrichment) site in Rhinelander, WI. We found that elevated CO(2) increased both the number of trees that flowered and the quantity of flowers (260% increase in male flower production), increased seed weight, germination rate, and seedling vigor. Elevated O(3) also increased flowering but decreased seed weight and germination rate. In the combination treatment (elevated CO(2)+O(3)) seed weight is decreased (20% reduction) while germination rate was unaffected. The evidence from this study indicates that elevated CO(2) may have a largely positive impact on forest tree reproduction and regeneration while elevated O(3) will likely have a negative impact.