Temporal patterns of atmospheric mercury species in northern Mississippi during 2011–2012: Influence of sudden population swings

Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) were measured on the University of Mississippi campus from July 2011 to June 2012. It is believed to be the first time that concentrations of atmospheric mercury species have been documented in northern Mississippi, and at a location with relatively large and sudden swings in population. The mean concentration (±1SD) of GEM was 1.54 ± 0.32 ng m⁻³; levels were lower and generally more stable during the winter (1.48 ± 0.22) and spring (1.46 ± 0.27) compared with the summer (1.56 ± 0.32) and fall (1.63 ± 0.42). Mean concentrations for GOM and PBM were 3.87 pg m⁻³ and 4.58 pg m⁻³, respectively; levels tended to be highest in the afternoon and lowest in the early morning hours. During the fall and spring academic semesters concentrations and variability of GOM and PBM both increased, possibly from vehicle exhaust. There were moderate negative correlations with wind speed (all species) and humidity (GOM and PBM). Backward air mass trajectory modeling for the ten highest peaks for each mercury species revealed that the majority of these events occurred from air masses that passed through the northern continental US region. Overall, this study illustrates the complexity of temporal fluctuations of airborne mercury species, even in a small town environment.     

Sexual difference in PCB congener distributions of burbot (Lota lota) from Lake Erie

Concentrations of 86 congeners of polychlorinated biphenyls (PCBs) were determined for 25 adult female and 25 adult male burbot (Lota lota) from Lake Erie. Significant differences in mean proportions of total PCB concentration between males and females ages 14–17 were found for 26 congeners. Males generally had higher mean proportions of hexachloro congeners, whereas females had higher mean proportions of more highly chlorinated congeners. In contrast, only four congeners exhibited differences between males and females ages 6–13 in mean proportions of total PCB. Therefore, the sexual difference in PCB congener distribution widened for older burbot. Males ages 14–17 also had higher proportions of certain hexachloro congeners than the other three demographic groups (males ages 6–13, females ages 6–13, and females ages 14–17) we examined. The reverse was true for more highly chlorinated congeners. The results supported a previous hypothesis that older male burbot spent a substantial amount of time feeding in the vicinity of mouths of rivers with sediment contaminated with PCBs. However, additional studies are needed to clarify and corroborate this apparent “hot spot” effect, such as seasonal movements, spatial distributions, and diet of burbot; and PCB congener distributions of various species of prey fishes captured at various locations throughout the eastern basin of Lake Erie and at different locations in the contaminated rivers.     

Development and field validation of an indicator to assess the relative mobility and risk of pesticides in the Lourens River catchment,South Africa

A GIS based pesticide risk indicator that integrates exposure variables (i.e. pesticide application, geographic, physicochemical and crop data) and toxicity endpoints (using species sensitivity distributions) was developed to estimate the Predicted Relative Exposure (PREX) and Predicted Relative Risk (PRRI) of applied pesticides to aquatic ecosystem health in the Lourens River catchment, Western Cape, South Africa. Samples were collected weekly at five sites from the beginning of the spraying season (October) till the beginning of the rainy season (April) and were semi quantitatively analysed for relevant pesticides applied according to the local farmers spraying programme. Monitoring data indicate that physicochemical data obtained from international databases are reliable indicators of pesticide behaviour in the Western Cape of South Africa. Sensitivity analysis identified K_OC as the most important parameter influencing predictions of pesticide loading derived from runoff. A comparison to monitoring data showed that the PREX successfully identified hotspot sites, gave a reasonable estimation of the relative contamination potential of different pesticides at a site and identified important routes of exposure (i.e. runoff or spray drift) of different pesticides at different sites. All pesticides detected during a monitored runoff event, were indicated as being more associated with runoff than spray drift by the PREX. The PRRI identified azinphos-methyl and chlorpyrifos as high risk pesticides towards the aquatic ecosystem. These results contribute to providing increased confidence in the use of risk indicator applications and, in particular, could lead to improved utilisation of limited resources for monitoring and management in resource constrained countries.     

A Call for Urgent Monitoring of Food and Water Security Based on Relevant Indicators for the Arctic

This perspective paper argues for an urgent need to monitor a set of 12 concrete, measurable indicators of food and water security in the Arctic over time. Such a quantitative indicator approach may be viewed as representing a reductionist rather than a holistic perspective, but is nevertheless necessary for actually knowing what reality aspects to monitor in order to accurately understand, quantify, and be able to project critical changes to food and water security of both indigenous and non-indigenous people in the Arctic. More relevant indicators may be developed in the future, taking us further toward reconciliation between reductionist and holistic approaches to change assessment and understanding. However, the potential of such further development to improved holistic change assessment is not an argument not to urgently start to monitor and quantify the changes in food and water security indicators that are immediately available and adequate for the Arctic context.     

Exclusion of chromosomal mosaicism in amniotic fluid cultures: Efficacy of in situ versus flask techniques

Accurate diagnosis of mosaicism in amniotic fluid cell cultures represents a major problem. If insufficient cells are analysed, true fetal mosaicism may go undetected. False-positive diagnosis is also possible since a second cell line may arise in vitro and not reflect the true fetal genetic constitution. These difficulties apply to both flask and in situ culture techniques, to varying degrees. The relative accuracy of flask versus in situ culture techniques in excluding mosaicism was determined by statistical analysis of experimental data from ten pairs of mixed male-female amniotic fluid specimens. The data support the idea that the majority of in situ colonies are independent of one another. The following conclusions are drawn: (1) analysis of a single metaphase from a number of different colonies enhances the confidence for excluding mosaicism; (2) analysis of more than one cell per colony offers little advantage; (3) exclusion of a given level of mosaicism requires analysis of fewer metaphases using the in situ method; (4) the confidence for excluding mosaicism is high with both in situ and flask techniques, using the provided guidelines; and (5) it is shown that the two-stage approach used by many laboratories is currently the most efficient way to exclude mosaicism.     

Guidance for the Field Demonstration of Remediation Technologies

This paper will focus on the demonstration of hazardous waste cleanup technologies in the field. The technologies will be at the pilot- or full-scale, and further referred to as field-scale. The main objectives of demonstration at the field-scale are development of reliable performance and cost data. Technology demonstrations provide performance, cost effectiveness, and reliability data so that potential technology users have sufficient information to make effective decisions as to the applicability of the technology to a specific situation. The demonstration and evaluation of a technology should be conducted with the purpose of characterizing performance, need for pre- and post-processing of the waste feed, identification of waste type and constituents applicable to the technology, system throughput, problems and limitations of the technology, and operating and maintenance costs. Table I provides a summary of remediation activities for demonstration projects.     

NOx Removal with Combined Selective Catalytic Reduction and Selective Noncatalytic Reduction: Pilot-Scale Test Results

Pilot-scale tests were conducted to develop a combined nitrogen oxide (NO_x) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium- and titanium-based composite honeycomb catalyst and enhanced urea (NH₂CONH₂) were used with a natural-gas-fired furnace at a NO_x concentration of 110 ppm. Changes in SNCR chemical injection temperature and stoichiometry led to varying levels of post-furnace ammonia (NH₃), which acts as the reductant feed to the downstream SCR catalyst. The urea-based chemical could routinely achieve SNCR plus SCR total NO_x reductions of 85 percent with less than 3 ppm NH₃ slip at reductant/NO_x stoichiometries ranging from about 1.5 to 2.5 and SCR space velocities of 18,000 to 32,000 h^?1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NO_x removal. SNCR provides high temperature reduction of NO_x followed by further removal of NO_x and minimization of NH₃ slip by a significantly downsized (high-space velocity) SCR.     

Hydrocarbon Measurements During the 1992 Southern Oxidants Study Atlanta Intensive: Protocol and Quality Assurance

Abstract

A major component of the Southern Oxidants Study (SOS) 1992 Atlanta Intensive was the measurement of atmospheric nonmethane hydrocarbons. Ambient air samples were collected and analyzed by a network of strategically located automated gas chromatography (GC) systems (field systems). In addition, an extensive canister sampling network was deployed. Combined, more than 3000 chromatograms were recorded. The SOS science team targeted for quantitative analysis 56 compounds which may be substantial contributors to ozone formation or used as air mass tracers. A quality assurance program was instituted to ensure that good measurements were being made throughout the network for each target compound. Common, high-quality standards were used throughout the network. The performance of individual field systems was evaluated during the intensive through the analysis of challenge mixtures. This methodology helped to identify and correct analytical problems as they arose.     

A Comparative Analysis of Emissions Deterioration for In-Use Alternative Fuel Vehicles

Abstract

Although there have been several studies examining emissions from in–use alternative fuel vehicles (AFVs), little is known about the deterioration of these emissions over vehicle lifetimes and how this deterioration compares with deterioration from conventional vehicles (CVs). This paper analyzes emissions data from 70 AFVs and 70 CVs operating in the federal government fleet to determine whether AFV emissions deterioration differs significantly from CV emissions deterioration. An analysis is conducted on three alternative fuel types (natural gas, methanol, and ethanol) and on four pollutants (carbon monoxide, total hydrocarbons, non-methane hydrocarbons, and nitrogen oxides). The results indicate that for most cases studied, deterioration differences are not statistically significant; however, several exceptions (most notably with natural gas vehicles) suggest that air quality planners and regulators must further analyze AFV emissions deterioration to properly include these technologies in broader air quality management schemes.     

Particulate,Carbon Monoxide,and Acid Emission Factors for Residential Wood Burning Stoves

Emissions from residential wood burning stoves are of Increasing concern in many areas. This concern is due to the magnitude of the emissions and the toxic and chemical characteristics of the pollutants. Recent testing of standard and new technology woodstoves has provided data for developing a family of particulate and carbon monoxide emission factor curves. This testing has also provided data illustrating the acidity of woodstove emissions. The particulate and carbon monoxide curves relate the actual stove emissions to the stove size and operating parameters of burn rate, fuel loading, and fuel moisture. Curves relating stove types to the acidity of emissions have also been constructed.

Test data show actual emissions vary from 3 to 50 grams per kilogram for particles and from 50 to 300 grams per kilogram for carbon monoxide. Since woodstove emissions are the largest single category of particulate emissions in many areas, it Is essential that these emissions be quantified specifically for geographic regions, allowing meaningful impact analysis modeling to be accomplished. Emission factors for particles and carbon monoxide are presented from several stove sizes and burn rates.

The acidic nature of woodstove emissions has been clearly demonstrated. Tests indicate woodstove flue gas condensate solutions to be predominantly in the 2.8 to 4.2 pH range. Condensate solutions from conventional woodstoves exhibited the characteristic buffering capacity of carboxylic acids when titrations were performed with a strong base. The environmental impact of buffered acidic woodstove emissions is not currently well understood; however, it is possible with the data presented here to make semi-quantitative estimates of acid emissions from particulate and carbon monoxide emission factors and wood use inventories.