Fine Particles and Oxidant Pollution: Developing an Agenda for Cooperative Research

ABSTRACT

This paper describes a background for the North American Research Strategy for Tropospheric Ozone (NARSTO) cooperative program integrating studies of O₃ and PM_{2 5}. It discusses several important aspects for rationalizing NARSTO's trinational investigative approach, including (1) an outlook on the state of knowledge about fine particles in the troposphere and their origins in Canada, Mexico, and the United States; (2) the need for enhancement and strengthening of key field measurements in relation to tropospheric chemistry and a health effects component; and (3) the use of a central theme for advancing air quality modeling using evolving techniques to integrate and guide key process-oriented field campaigns. The importance of organizing a scientific program to acquire “policy-relevant” information is stressed, noting cooperative research directions that address combined PM_2.5 and O₃ issues, illustrated through exploration of hypothetical pathways of PM_2.5 response to choices of O₃ and PM precursor emission reductions. The information needed for PM_2.5 research is noted to intersect in many cases with those of O₃, but diverge in other cases. Accounting for these distinctions is important for developing NARSTO's strategy over the next decade.     

Calibration of Sharp Cut Impactors for Indoor and Outdoor Particle Sampling

ABSTRACT

A low-flow rate, sharp cut point inertial impaction sampler was developed in 1986 that has been widely used in PM exposure studies in the United States and several other countries. Although sold commercially as the MS&T Area Sampler, this sampler is widely referred to as the Harvard Impactor, since the initial use was at the Harvard School of Public Health. Impactor nozzles for this sampler have been designed and characterized for flows of 4,10, 20, and 23 L/min and cut points of 1, 2, 5, and 10 |im. An improved method for determining the actual collecting efficiency curve was developed and used for the recent impactor calibrations reported here. It consists of placing a multiplet reduction impactor inline just downstream of the vibrating orifice aerosol generator to remove the multiplets, thus allowing only the singlet particle s to penetrate through to the impactor being calibrated.

This paper documents the techniques and results of recent nozzle calibrations for this sampler and compares it with other size-selective inertial impactors. In general, the impactors were found to have sharp cutoff characteristics. Particle interstage losses for all of the impactors were very low, with the exception of the 10-|im cut size 20 L/ min impactor, which had greater losses due to the higher flow rate. All of the cut nozzle laboratory calibrations compare favorably to the U.S. Environmental Protection Agency (EPA) WINS-96 fine particle mass (PM_{2 5}) impactor calibration data.     

Air Emission Inventories in North America: A Critical Assessment

Abstract

Although emission inventories are the foundation of air quality management and have supported substantial improvements in North American air quality, they have a number of shortcomings that can potentially lead to ineffective air quality management strategies. Major reductions in the largest emissions sources have made accurate inventories of previously minor sources much more important to the understanding and improvement of local air quality. Changes in manufacturing processes, industry types, vehicle technologies, and metropolitan infrastructure are occurring at an increasingly rapid pace, emphasizing the importance of inventories that reflect current conditions. New technologies for measuring source emissions and ambient pollutant concentrations, both at the point of emissions and from remote platforms, are providing novel approaches to collecting data for inventory developers. Advances in information technologies are allowing data to be shared more quickly, more easily, and processed and compared in novel ways that can speed the development of emission inventories. Approaches to improving quantitative measures of inventory uncertainty allow air quality management decisions to take into account the uncertainties associated with emissions estimates, providing more accurate projections of how well alternative strategies may work. This paper discusses applications of these technologies and techniques to improve the accuracy, timeliness, and completeness of emission inventories across North America and outlines a series of eight recommendations aimed at inventory developers and air quality management decision-makers to improve emission inventories and enable them to support effective air quality management decisions for the foreseeable future.     

The Southeastern Aerosol Research and Characterization Study,Part 3: Continuous Measurements of Fine Particulate Matter Mass and Composition

Abstract

Deployment of continuous analyzers in the Southeastern Aerosol Research and Characterization Study (SEARCH) network began in 1998 and continues today as new technologies are developed. Measurement of fine particulate matter (PM_2.5) mass is performed using a dried, 30 °C tapered element oscillating microbalance (TEOM). TEOM measurements are complemented by observations of light scattering by nephelometry. Measurements of major constituents include: (1) SO₄ ^2? via reduction to SO₂; (2) NH₄ ⁺ and NO₃ ^? via respective catalytic oxidation and reduction to NO, (3) black carbon (BC) by optical absorption, (4) total carbon by combustion to CO₂, and (5) organic carbon by difference between the latter two measurements. Several illustrative examples of continuous data from the SEARCH network are presented. A distinctive composite annual average diurnal pattern is observed for PM_2.5 mass, nitrate, and BC, likely indicating the influence of traffic-related emissions, growth, and break up of the boundary layer and formation of ammonium nitrate. Examination of PM_2.5 components indicates the need to better understand the continuous composition of the unmeasured “other” category, because it contributes a significant fraction to total mass during periods of high PM_2.5 loading. Selected episodes are presented to illustrate applications of SEARCH data. An SO₂ conversion rate of 0.2%/hr is derived from an observation of a plume from a coal-fired power plant during early spring, and the importance of local, rural sources of NH₃ to the formation of ammonium nitrate in particulate matter (PM) is demonstrated.     

Development of the Ammonia Injection Technology (AIT) for the Control of PCDD/PCDF and Acid Gases from Municipal Solid Waste Incinerators

This article describes the development of the Ammonia Injection Technology (AIT), a technology for the simultaneous control of the emissions of PCDD/PCDF (polychlorinated p-dibenzodioxins and polychlorinated dibenzofurans), HCI, SO₂ and NOX from municipal solid waste incinerators. It briefly reviews the theoretical basis of the technology and the bench-scale and pilot-scale experiments. It describes the results of the pilot-scale experiment in detail and reports on the finding that the formation of PCDD and PCOF takes place in different regions of the boiler system. Finally, a concept is introduced for the treatment of emission control residues which could lead to the recovery of chlorine from waste products and its “recycle” to the chlorine manufacturing process (“closed chlorine life cycle“ concept).     

The Southeastern Aerosol Research and Characterization Study: Part II. Filter-Based Measurements of Fine and Coarse Particulate Matter Mass and Composition

Abstract

The Southeastern Aerosol Research and Characterization Study (SEARCH) was implemented in 1998–1999 to provide data and analyses for the investigation of the sources, chemical speciation, and long-term trends of fine particulate matter (PM_2.5) and coarse particulate matter (PM_10–2.5) in the Southeastern United States. This work is an initial analysis of 5 years (1999–2003) of filter-based PM_2.5 and PM_10–2.5 data from SEARCH. We find that annual PM_2.5 design values were consistently above the National Ambient Air Quality Standards (NAAQS) 15 µg/m³ annual standard only at monitoring sites in the two largest urban areas (Atlanta, GA, and North Birmingham, AL). Other sites in the network had annual design values below the standard, and no site had daily design values above the NAAQS 65 µg/m³ daily standard. Using a particle composition monitor designed specifically for SEARCH, we found that volatilization losses of nitrate, ammonium, and organic carbon must be accounted for to accurately characterize atmospheric particulate matter. In particular, the federal reference method for PM_2.5 underestimates mass by 3–7% as a result of these volatilization losses. Organic matter (OM) and sulfate account for ≥60% of PM_2.5 mass at SEARCH sites, whereas major metal oxides (MMO) and unidentified components (“other”) account for ≥80% of PM_10–2.5 mass. Limited data suggest that much of the unidentified mass in PM_10–2.5 may be OM. For paired comparisons of urban-rural sites, differences in PM_2.5 mass are explained, in large part, by higher OM and black carbon at the urban site. For PM₁₀, higher urban concentrations are explained by higher MMO and “other.” Annual means for PM_2.5 and PM_10–2.5 mass and major components demonstrate substantial declines at all of the SEARCH sites over the 1999–2003 period (10–20% in the case of PM_2.5, dominated by 14–20% declines in sulfate and 11–26% declines in OM, and 14–25% in the case of PM_10–2.5, dominated by 17–30% declines in MMO and 14–31% declines in “ other”). Although declining national emissions of sulfur dioxide and anthropogenic carbon may account for a portion of the observed declines, additional investigation will be necessary to establish a quantitative assessment, especially regarding trends in local and regional emissions, primary carbon emissions, and meteorology.     

Biodegradation kinetics and toxicity of vegetable oil triacylglycerols under aerobic conditions

The aerobic biodegradation of five triacylglycerols (TAGs), three liquids [triolein (OOO), trilinolein (LLL), and trilinolenin (LnLnLn)] and two solids [tripalmitin (PPP) and tristearin (SSS)] was studied in water. Respirometry tests were designed and conducted to determine the biochemical oxygen demand (BOD) parameters of the compounds. In the case of the solid lipids, the degradation process was limited by their extremely non-polar nature. When added to water, PPP and SSS formed irregular clumps or gumballs, not a fine and uniform suspension required for the lipase activity. After 30 days, appreciable mineralization was not achieved; therefore, first-order biodegradation coefficients could not be determined. The bioavailability of the liquid TAGs was restricted due to the presence of double bonds in the fatty acids (FAs). An autoxidation process occurred in the allylic chains, resulting in the production of hydroperoxides. These compounds polymerized and became non-biodegradable. Nevertheless, the non-oxidized fractions were readily mineralized, and BOD rate constants were estimated by non-linear regression: LLL (k = 0.0061 h⁻¹) and LnLnLn (k = 0.0071 h⁻¹) were degraded more rapidly than OOO (k = 0.0025 h⁻¹). Lipids strongly partitioned to the biomass and, therefore, Microtox^® toxicity was not observed in the water column. However, EC₅₀ values (<15% sample volume) were measured in the solid phase.     

Age dependent acute oral toxicity of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and two anaerobic N-nitroso metabolites in deer mice (Peromyscus maniculatus)

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) transforms anaerobically into N-nitroso compounds: hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX). Exposure to these N-nitroso metabolites may occur in areas contaminated with explosives, as anaerobic degradation occurs via some bacteria and is one remediation strategy used for RDX. Few papers report acute oral toxicity and none have evaluated age dependent toxicity of RDX or its N-nitroso metabolites. Median lethal dose (LD₅₀) was determined in deer mice (Peromyscus maniculatus) of three age classifications 21 d, 50 d, and 200 d for RDX, MNX, and TNX using the US EPA up-and-down procedure (UDP). Hexahydro-1,3,5-trinitro-1,3,5-triazine and N-nitroso metabolites caused similar overt signs of toxicity. Median lethal dose for 21 d deer mice were 136, 181, and 338 mg/kg for RDX, MNX, and TNX, respectively. Median lethal dose for 50 d deer mice were 319, 575, and 338 mg/kg for RDX, MNX, and TNX, respectively. Median lethal dose for 200 d deer mice were 158, 542, and 999 mg/kg for RDX, MNX, and TNX, respectively. These data suggest that RDX is the most potent compound tested, and age dependent toxicity may exist for all compounds and could play a role in RDX and RDX N-nitroso metabolite ecological risk evaluation of terrestrial wildlife at RDX contaminated sites.     

Fate of sex hormones in two pilot-scale municipal wastewater treatment plants: conventional treatment

The fate of seven sex hormones (estrone (E1), estradiol (E2), estriol (E3), ethinylestradiol (EE2), testosterone, androstenedione, and progesterone) was determined in two pilot-scale wastewater treatment plants operated under conventional loading conditions. The levels of hormones in both the liquid and the solid matrixes of the plants were determined. Each of the two 20-l/h pilot-scale plants consisted of a primary clarifier followed by a three-stage aeration tank and a final clarifier. The primary sludge and the waste activated sludge (WAS) were digested anaerobically in one pilot plant and aerobically in the other. The pilot plants were fed a complex synthetic wastewater spiked with the hormones. Levels of testosterone, androstenedione and progesterone were close to method detection limit (MDL) concentrations in the final and digester effluents (both liquid and solid phases) and were considered as completely removed. Average mass flux removals from the liquid streams (plant influent minus secondary clarifier effluent) for the natural estrogens were 82% for E1, 99% for E2, and 89% for (E1+E2). An average overall removal of only 42% was achieved for EE2. These values reflect removals averaged for the two pilot plants.