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.     

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.     

Significantly higher number of fetal cells in the maternal circulation of women with pre-eclampsia

Although the pathophysiology of pre-eclampsia is unknown, several studies have indicated that abnormal placentation early in pregnancy might play a key role. It has recently been suggested that this abnormal placentation may result in transfusion of fetal cells (feto-maternal transfusion) in women with pre-eclampsia. In the present study, fetal nucleated red blood cells were isolated from 20 women with pre-eclampsia and 20 controls using a very efficient magnetic activated cell sorting (MACS) protocol. The number of male cells was determined using two-color fluorescence in situ hybridization (FISH) for X and Y chromosomes. Significantly more XY cells could be detected in women with pre-eclampsia (0.61±1.2 XY cells/ml blood) compared to women with uncomplicated pregnancies (0.02±0.04 XY cells/ml blood) (Mann–Whitney U-test, p<0.001). These results suggest that fetal cell trafficking is enhanced in women with pre-eclampsia, and this finding may contribute to the understanding of the pathophysiology of the disease. Copyright © 2001 John Wiley & Sons, Ltd.     

DDT residues in water, sediment, domestic and indigenous biota from a currently DDT-sprayed area

DDT is used for indoor residual spraying (IRS) in Limpopo Province, northern South Africa to control malaria. Through IRS, DDT may reach the outdoor environment via dust and air and from possible spillages during application. In this area the local people consume domestic chickens, wild fish or birds. Fish from the river catchment and impoundments seem to be the major source of protein intake. Water, sediment and tissue samples from two such fish species, domestic chickens and wild birds (terrestrial and aquatic) from this DDT-sprayed area were analysed for DDT and metabolite residues. The samples contained p,p′-DDT, p,p′-DDD and p,p′-DDE residues, with the latter the most ubiquitous and in the highest concentrations. These findings raise concern that both water and food may be major routes of human exposure to DDT and metabolites, thereby posing possible adverse human health implications to the local communities.     

Ecological studies on intertidal New Zealand Sphaeromatidae (Isopoda: Flabellifera)

Ten sympatric rocky shore species and 3 brackish-water species of Sphaeromatidae were studied. Rocky shores were classified in terms of substrate and exposure to wave action. Although most of the rocky-shore species occur on all shore classes, vertical and horizontal distribution in each species, as well as densities, vary with substrate and wave action. A close relationship between distribution and breeding exists in the rocky-shore species; maximum differences in the vertical distribution of juveniles and adults occur, together with the highest reproductive capacities, in the species exposed to the greatest wave action. Tolerances to temperature, salinity and desiccation are wider in the species of brackish water and less exposed rocky shores, correlating with the greater variations in these conditions where wave action is reduced. Exoskeletons and pereopods are stouter in the species of more exposed shores, except where the microhabitat affords protection from wave action. In Isocladus armatus, geographic and seasonal variations in relative frequencies of colour forms correlate with differences in environmental temperatures. Under laboratory conditions, the colour forms show differences in tolerances to temperature and salinity.This work was carried out in the Zoology Department, University of Canterbury, New Zealand; the text was completed in Zoologisches Institut der Universität Kiel, Germany.