Middle- and Neighborhood-Scale Variations of PM10 Source Contributions in Las Vegas, Nevada.

The Las Vegas Valley PM10 Study was conducted during 1995 to determine the contributions to PM10 aerosol from fugitive dust, motor vehicle exhaust, residential wood combustion, and secondary aerosol sources. Twenty-four-hr PM10 samples were collected at two neighborhood-scale sites every sixth day for 13 months. Five week-long intensive studies were conducted over a middle-scale sub-region at 29 locations that contained many construction projects emitting fugitive dust. The study found that the zone of influence around individual emitters was less than 1 km. Most of the sampling sites in residential and commercial areas yielded equivalent PM10 concentrations in the neighborhood region, even though they were more distant from each other than they were from the nearby construction sources. Based on chemical mass balance (CMB) receptor modeling, fugitive dust accounted for 80-90% of the PM10, and motor vehicle exhaust accounted for 3-9% of the PM10 in the Las Vegas Valley.

Combination of intermittent cyclical etidronate and hormone replacement therapy for postmenopausal non-responders to estrogen.

OBJECTIVE: To investigate whether the addition of etidronate to conventional hormone replacement therapy (HRT) is effective against bone loss in postmenopausal women whose lumbar bone mineral density (BMD) cannot be maintained by HRT. DESIGN: Single-centre, placebo-controlled randomised study. PATIENTS: Among 1138 patients on conventional HRT, 30 postmenopausal women were considered to be non-responders to estrogen, since their BMDs continued to decrease by more than 1% per year in spite of the HRT. The BMD of all the included patients was less than 70% of the young adult mean. INTERVENTIONS: PATIENTS were randomly divided into two groups: group A (n = 15) treated with conventional HRT and placebo, and group B (n = 15) treated with combined intermittent cyclical etidronate therapy (ICT-etidronate) and conventional HRT. Measurement of lumbar BMD was performed at baseline and at 6 and 12 months using dual energy x-ray absorptiometry (DEXA). Biochemical markers of bone resorption and formation were also measured during the visits. RESULTS: ICT-etidronate combined with HRT increased the lumbar BMD at 6 months (p < 0.05) and 12 months (p < 0.05) compared with baseline. Lumbar BMDs of the combined treatment group were significantly increased at 12 months (p < 0.05) compared with the HRT-only group. Bone resorption was suppressed by combined therapy at 6 months (p < 0.05). Bone formation did not change in either group. CONCLUSIONS: ICT-etidronate combined with HRT seems to be effective in preventing loss of BMD in postmenopausal women who do not respond to estrogen, and may be useful in preventing fractures in this group.

PM2.5 and PM10 concentrations from the Qalabotjha low-smoke fuels macro-scale experiment in South Africa.

This article presents results from the particulate monitoring campaign conducted at Qalabotjha in South Africa during the winter of 1997. Combustion of D-grade domestic coal and low-smoke fuels were compared in a residential neighborhood to evaluate the extent of air quality improvement by switching household cooking and heating fuels. Comparisons are drawn between the gravimetric results from the two types of filter substrates (Teflon-membrane and quartz-fiber) as well as between the integrated and continuous samplers. It is demonstrated that the quartz-fiber filters reported 5 to 10% greater particulate mass than the Teflon-membrane filters, mainly due to the adsorption of organic gases onto the quartz-fiber filters. Due to heating of sampling stream to 50 degrees C in the TEOM continuous sampler and the high volatile content of the samples, approximately 15% of the particulate mass was lost during sampling. The USEPA 24-hr PM2.5 and PM10 National Ambient Air Quality Standards (NAAQS) of 65 microg m(-3) and 150 microg m(-3), respectively, were exceeded on several occasions during the 30-day field campaign. Average PM concentrations are highest when D-grade domestic coal was used, and lowest between day 11 and day 20 of the experiment when a majority of the low-smoke fuels were phased in. Source impacts from residential coal combustion are also found to be influenced by changes in meteorology, especially wind velocity. PM2.5 and PM10 mass, elements, water-soluble cations (sodium, potassium, and ammonium), anions (chloride, nitrate, and sulfate), as well as organic and elemental carbon were measured on 15 selected days during the field campaign. PM2.5 constituted more than 85% of PM10 at three Qalabotjha residential sites, and more than 70% of PM10 at the gradient site in the adjacent community of Villiers. Carbonaceous aerosol is by far the most abundant component, accounting for more than half of PM mass at the three Qalabotjha sites, and for more than a third of PM mass at the gradient site. Secondary aerosols such as sulfate, nitrate, and ammonium are also significant, constituting 8 to 12% of PM mass at the three Qalabotjha sites and 15 to 20% at the Villiers gradient site.

Comparison of PM10 concentrations in high- and medium-volume samplers in a desert environment.

The USEPA replaced TSP with PM10 as the National Ambient Air Quality Standard for particulate matter. The commercially available PM10 sampler is a high-volume model using quartz fiber filters. In certain investigations, such as source apportionment studies, chemical analysis of the filter is necessary, however, many analyses cannot be run on quartz filters. An alternate filter such as Teflon is amenable to XRF and ion chemical analyses but is not amenable to analysis for carbon. To overcome these problems DRI constructed a medium-volume PM10 sampler that is capable of collecting particulates on both Teflon and quartz fiber filters simultaneously. This paper describes the design of the DRI medium-volume PM10 sampler, discusses a method for determining equivalence of two samplers, the results of applying the method to test the equivalence of the medium-volume sampler and a commerical high-volume sampler, and examines differences between PM10 and TSP measurements in a southwestern desert.