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Low-cost, practicable techniques are required to limit the release of volatile organic compound-containing fumigants such as 1,3-D to the atmosphere. In this study, we aimed to quantify 1,3-D diffusion and emission from laboratory soil columns maintained under realistic conditions and thereby assess the efficacy of soil irrigation as a technique for reducing emissions. In two soils (one relatively high, and one relatively low, in organic matter), irrigation led to a limiting of upward diffusion of the fumigant and to the maintenance of higher soil gas concentrations. Therefore, rather than being emitted from the column, the 1,3-D was maintained in the soil where it was ultimately degraded. As a consequence, emission of 1,3-D from the irrigated columns was around half of that from the nonirrigated columns. It is concluded that surface irrigation represents an effective, low-cost, and readily practicable approach to lessening the environmental impact of 1,3-D fumigant use. In addition, the higher organic matter soil exhibited emissions of around one-fifth of the lower organic matter soil in both irrigated and nonirrigated treatments, due to markedly enhanced degradation of the fumigant. Organic matter amendment of soils may, therefore, also represent an extremely effective, relatively low-cost approach to reducing 1,3-D emissions. [ABSTRACT FROM AUTHOR]

Passive air samplers (polyurethane foam disks) were deployed at 23 background locations along a broadly west-east transect in 8 northern European countries and analyzed for PCBs, PBDEs, PAHs, and a range of organochlorine pesticides (HCB, DDTs, and DDEs). PCBs and PAHs were highest at the center of the transect (Denmark) and lowest in northern Norway. HCB was relatively uniformly distributed, reflecting its persistence and high degree of mixing in air. Higher DDE and DDT levels occurred in Eastern Europe and at several sites in Central Europe. PBDE levels were generally similar at all sites, but lower for some locations in Eastern Europe and Ireland. Emissions information for PCBs, HCB, and PBDEs was used as input for a multi-media chemical fate model, to generate predicted air concentrations and compare with these measured values. Different scenarios were highlighted by this exercise: (i) country and compound combinations where the national inventory gave predicted air concentrations in close agreement with those measured (e.g., PCBs in the UK); (E) country and compound combinations where predicted concentrations were well below those measured, but where advection of emissions from elsewhere is likely to be important (e.g., PCBs in Norway); (iii) consistent underestimation of compound concentrations by the emissions modeling (i.e., HCB); and (iv) general overestimation of ambient concentrations (i.e., PBDEs). Air mass trajectory analysis showed the likely role of long-range atmospheric transport (LRAT) on national levels. In general, advection from the south and west of Europe appeared to contribute to ambient POPs levels for countries in the center and northeast of the transect. Guidelines are presented as to how countries that want to assess their POPs source inventories can do so with this relatively cheap initial screening approach. [ABSTRACT FROM AUTHOR]

Worldwide people are exposed to toxic ultrafine particles (UFP, with diameters (dp) less than 100 nm) and nanoparticles (NP, dp < 50 nm) under a variety of circumstances. To date, very limited information is available on human exposure to freshly emitted UFP and NP while traveling on major roads and freeways. We report in-cabin and outdoor measurements of particle number concentration and size distributions while driving three vehicles on Los Angeles freeways. Particle number concentrations and size distributions were measured under different vehicle ventilation settings. When the circulation fan was set to on, with substantial external air intake, outside changes in particle counts caused corresponding in-cabin changes approximately 30–60 s later, indicating an maximal air exchange rate of about 120–60 h-1. Maximum in-cabin protection (∼85%) was obtained when both fan and recirculation were on. In-cabin and outdoor particle size distributions in the 7.9–217 nm range were observed to be mostly bimodal, with the primary peak occurring at 10–30 nm and the secondary at 50–70 nm. The vehicle's manufacture-installed particle filter offered an in-cabin protection of about 50% for particles in the 7–40 nm size range and 20–30% for particles in the 40 to ∼200 nm size range. For an hour daily commute exposure, the in-vehicle microenvironment contributes approximately 10–50% of people's daily exposure to UFP from traffic. [ABSTRACT FROM AUTHOR]

For more than 20 years the global emissions and the lifetime of methane have probably been constant, so the buildup of methane in the atmosphere has been slowing down for as long. During this time, there have been periodic events occurring every seven to eight years, when global methane concentrations increased by some 10 ppb and later fell back, in some cases due to temporary increases of emissions from the northern tropics that spread to the global scale. These conclusions are derived from the accumulated global observations that now span 23 years and define the role of human activities in the recent cycle of atmospheric methane. [ABSTRACT FROM AUTHOR]

Factors associated with sources, transport, and fate of volatile organic compounds (VOCs) in groundwater from aquifers throughout the United States were evaluated using statistical methods. Samples were collected from 1631 wells throughout the conterminous United States between 1996 and 2002 as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey. Water samples from wells completed in aquifers used to supply drinking water were analyzed for more than 50 VOCs. Wells were primarily rural domestic water supplies (1184), followed by public water supplies (216); the remaining wells (231) supplied a variety of uses. The median well depth was 50 meters. Age-date information shows that about 60% of the samples had a fraction of water recharged after 1953. Chloroform, toluene, 1,2,4-trimethylbenzene, and perchloroethene were some of the frequently detected VOCs. Concentrations generally were less than 1 μg/L. Source factors include, in order of importance, general land-use activity, septic/sewer density, and sites where large concentrations of VOCs are potentially released, such as leaking underground storage tanks. About 10% of all samples had V0C mixtures that were associated with concentrated sources; 20% were associated with dispersed sources. Important transport factors included well/screen depth, precipitation/groundwater recharge, air temperature, and various soil characteristics. Dissolved oxygen was strongly associated with VOCs and represents the fate of many VOCs in groundwater. Well type (domestic or public water supply) was also an important explanatory factor. Results of multiple analyses show the importance of (1) accounting for both dispersed and concentrated sources of VOCs, (2) measuring dissolved oxygen when sampling wells to help explain the fate of VOCs, and (3) limiting the type of wells sampled in monitoring networks to avoid unnecessary variance in the data, or controlling for this variance during data analysis. [ABSTRACT FROM AUTHOR]

Biomass combustion emissions make a significant contribution to the overall particulate pollution in the troposphere. Wildland or prescribed burns and residential wood combustion emissions can vary due to differences in fuel, season, time of day, and the nature of the combustion. Inadequate understanding of the relevance of these biomass combustion emissions is due to the lack of characterization of open combustion emissions and the limited understanding of the differences between these and residential wood combustion. To provide new insight to biomass combustion emissions, sampling was conducted in several types of conditions. Semi-volatile organic compounds (SVOC) were collected during four separate prescribed burns in three different ecosystems, Mariposa Sequoia Grove within Yosemite National Park, CA, desert brushes of central rural Nevada, and Toiyabye National Forest near Lake Tahoe, NV. SVOC samples were also collected under controlled conditions for several wildland fuels, including conifer needles, wildland grasses, and sagebrush. Fireplace emissions from simulated residential wood combustion were also collected and are included here for comparison. A high degree of variability was found in the emissions of organic carbon, elemental carbon, levoglucosan, methoxy phenols, and organic acids. The variability in the emissions of levoglucosan does not correlate with the PM2.5 gravimetric mass and thus may affect source apportionment estimates. [ABSTRACT FROM AUTHOR]

As part of the State Implementation Plan for attaining the National Ambient Air Quality Standard for ozone, the Texas Commission of Environmental Quality has created a Highly Reactive Volatile Organic Compounds (HRVOC) Emissions Cap and Trade Program for industrial point sources in the Houston/Galveston/Brazoria area. This series of papers examines the potential air quality impacts of this new emission trading program through photochemical modeling of potential trading scenarios; this paper examines the air quality impact of allowing facilities to trade chlorine emission reductions for HRVOC allocations on a reactivity weighted basis. The simulations indicate that trading of anthropogenic chlorine emission reductions for HRVOC allowances at a single facility or between facilities, in general, resulted in improvements in air quality. Decreases in peak 1-h averaged and 8-h averaged ozone concentrations associated with trading chlorine emissions for HRVOC allocations on a Maximum Incremental Reactivity (MIR) basis were up to 0.74 ppb (0.63%) and 0.56 ppb (0.61%), respectively. Air quality metrics based on population exposure decreased by up to 3.3% and 4.1% for 1-h and 8-h averaged concentrations. These changes are small compared to the maximum changes in ozone concentrations due to the VOC emissions from these sources (5–10 ppb for 8-h averages; up to 30 ppb for 1-h averages) and the chlorine emissions from the sources (5–10 ppb for maximum concentrations over wide areas and up to 70 ppb in localized areas). The simulations indicate that the inclusion of chlorine emissions in the trading program is likely to be beneficial to air quality and is unlikely to cause localized increases in ozone concentrations (‘hot spots’). [ABSTRACT FROM AUTHOR]

The article provides an overview of the mercury control technologies aimed at lessening the mercury emissions from coal-fired electric utility boilers in the U.S. The author stressed that mercury emissions from anthropogenic emission sources posed a global threat that needs to be subsided. In response, the U.S. Environmental Protection Agency proclaimed the Clean Air Mercury Rule to permanently cap and abridge emissions of mercury from coal-fired power plants. Another regulation promulgated is the Clean Air Interstate Rule, which compels further reduction of sulphur dioxide and nitrogen oxides from these power plants. Among the control technologies stressed include flue-gas desulfurization and limestone forced- oxidation.