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The results are presented of a study conducted to examine the reactivity of NaHCO 3 and its thermally decomposed product, Na 2 CO 3 , with SO 2 as a function of temperature and particle size in a simulated flue gas. The NaHCO 3 reaction was found to be significantly more efficient than the Na 2 CO 3 reaction for temperatures less than 450°F (230°C) with a maximum efficiency of conversion occurring between 250 and 350°F. In the temperature range of 450-650°F, both compounds were observed to behave similarly. The Na 2 CO 3 reaction with SO 2 was found to be dependent on particle size in the range of 20-200 /tm for temperatures less than 450°F. The focus on sodium bicarbonate (NaHCOs) as a dry additive injection material for flue gas desulfurization (FGD) systems has come about mainly from the abundance and proximity of nahcolite to oil shale reserves, and the desire to identify an all dry FGD system. Nahcolite is a naturally occurring form of sodium bicarbonate (70% NaHC0 3 , remainder inerts), found in large underground deposits in northwestern Colorado, northeast Utah and southeast Wyoming which places it within a reasonable transportation range for coalfired steam plants located in the western part of the U.S. In addition, trona (Na 2 CO 3 NaHCOg • 2H 2 O) is also a candidate for FGD and is located in large deposits in the.U.S. Data have been collected on a variety of pilot and full scale fabric filter collectors to demonstrate the ability of the above compounds to remove SO2. 1 "" 3 These reports have concluded that the temperature, size of additive and type of injection technique (continuous versus batch) have been observed to affect the performance. Also it has been shown that sodium carbonate (N&2CO3), the product of decomposition of NaHC(>3, does not react as readily with SO2 as the parent NaHCO3. A possible explanation for this behavior may stem from the effect of the heated flue gas on thermally decomposing the NaHCOg into the product Na2COs while undergoing simultaneous reaction with SO2. The decomposition reaction for NaHC03 is given by: 2NaHCO 3 (s) Na 2 CO 3 (s) CO 2 (g) + H 2 O(g) (1)
To address the lack of research on the pulmonary health effects of ozone and fine particulate matter (≤ 2.5 μm in aerodynamic diameter; PM2.5) on individuals who recreate in the Great Smoky Mountains National Park (USA) and to replicate a study performed at Mt. Washington, New Hampshire (USA), we conducted an observational study of adult (18–82 years of age) day hikers of the Charlies Bunion trail during 71 days of fall 2002 and summer 2003. Volunteer hikers performed pre- and posthike pulmonary function tests (spirometry), and we continuously monitored ambient O3, PM2.5, temperature, and relative humidity at the trailhead. Of the 817 hikers who participated, 354 (43%) met inclusion criteria (nonsmokers and no use of bronchodilators within 48 hr) and gave acceptable and reproducible spirometry. For these 354 hikers, we calculated the posthike percentage change in forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FVC/FEV1, peak expiratory flow, and mean flow rate between 25 and 75% of the FVC and regressed each separately against pollutant (O3 or PM2.5) concentration, adjusting for age, sex, hours hiked, smoking status (former vs. never), history of asthma or wheeze symptoms, hike load, reaching the summit, and mean daily temperature. O3 and PM2.5 concentrations measured during the study were below the current federal standards, and we found no significant associations of acute changes in pulmonary function with either pollutant. These findings are contrasted with those in the Mt. Washington study to examine the hypothesis that pulmonary health effects are associated with exposure to O3 and PM2.5 in healthy adults engaged in moderate exercise.
The thermal decomposition of sodium bicarbonate, a candidate material for Ilue gas desulfunzation. has been investigated over the temperature range of 225-350°F (.380-450K) and over the particle size range of 51-140 ,urn. The shrinking core model, with chemical reaction as the rate controlling step, provides a good fit to the data in the temperature range investigated. However, caution should be exercised in extrapolating these results into the range of about 600"F (about 590K) where sintering of this material is reported to occur. The activation energy of the decomposition reaction is 20.5 kcal/mol (85.7 k.l/rnol).
A computer model called the Ozone Risk Assessment Model (ORAM) was developed to evaluate the health effects caused by ground-level ozone (O 3 ) exposure. ORAM was coupled with the U.S. Environmental Protection Agency's (EPA) Third-Generation Community Multiscale Air Quality model (Models-3/CMAQ), the state-of-the-art air quality model that predicts O 3 concentration and allows the examination of various scenarios in which emission rates of O 3 precursors (basically, oxides of nitrogen [NO x ] and volatile organic compounds) are varied. The principal analyses in ORAM are exposure model performance evaluation, health-effects calculations (expected number of respiratory hospital admissions), economic valuation, and sensitivity and uncertainty analysis through a Monte Carlo simulation. As a demonstration of the system, ORAM was applied to the eastern Tennessee region, and the entire O 3 season was simulated for a base case (typical emissions) and three different emission scenarios. The results indicated that a synergism occurs when reductions in NO x emissions from mobile and point sources were applied simultaneously. A 12.9% reduction in asthma hospital admissions is expected when both mobile and point source NO x emissions are reduced (50 and 70%, respectively) versus a 5.8% reduction caused by mobile source and a 3.5% reduction caused by point sources when these emission sources are reduced individually.
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