Performance of methods for measurement of exposure to inorganic acids in workplace air

BGIA has organised round robins for the analysis of samples of inorganic acids in workplace air for a number of years. Test samples of the volatile acids HCl and HNO(3) are collected from a standard atmosphere and samples of the non-volatile acids H(3)PO(4) and H(2)SO(4) are prepared by spiking filters with acid solution. The last two round robins have also covered the sampling of volatile acids, with up to 15 "active" participants able to visit the test facility in Dresden and take samples themselves. For other "passive" participants, BGIA takes samples from the same atmosphere. The acid concentrations generated lie between 0,1 and 1 times the German limit values for HCl and HNO(3). The results for the last round robin showed no significant difference between the performance of the "active" and "passive" participants. The participant means were in good agreement with the theoretical concentrations and the quality control measurements. For "active" participants RSDs were between 7% and 14% and for all participants between 8% and 16%. The round robin for the non-volatile acids showed similar results. The participant means were again in excellent agreement with the quality control measurements and RSDs were between 12% and 15%. The BGIA round robins have demonstrated the proficiency of laboratories measuring exposure to inorganic acids in air. However, concerns remain about the performance of published methods. It has shown that the sampling efficiency of sorbent tubes falls off with increasing particle size and hence silica gel tube methods may give low results for acid mists. Another issue with silica gel tubes is that a substantial proportion of the sample can be collected on the glass wool plugs that retain the sorbent. This can be up to 50% for HCl and 100% for HNO(3). Hence, low results may be obtained if the glass wool plugs are discarded. Similarly, methods for volatile inorganic acids that use a pre-filter to remove particulates usually overlook the fact that the acids can react with co-particulate matter on the pre-filter. Low recoveries in the range 30%-50% have been found when sampling HCl through filters loaded with potential interferents. Finally, particulate salts interfere with filter sampling methods for non-volatile inorganic acids. A two-part International Standard is in preparation for inorganic acids by ion chromatography and the issues discussed above are being taken into consideration during its development.     

Using Ion-Exchange Resins to Study Soil Response to Experimental Watershed Acidification

Ion-exchange resins (IER) offer alternative approaches to measuring ionic movement in soils that may have advantages over traditional approaches in some settings, but more information is needed to understand how IER compare with traditional methods of measurement in forested ecosystems. At the Bear Brook Watershed in Maine (BBWM), one of two paired, forested watersheds is treated bi-monthly with S and N (28.8 and 25.2kgha⁻¹yr⁻¹ of S and N, respectively). Both IER and ceramic cup tension lysimeters were used to study soil solution responses after ∼11 years of treatment. Results from both methods showed treatments resulted in the mobilization of base cations and Al, and higher SO₄—S and inorganic N in the treated watershed. Both methods indicated similar differences in results associated with forest type (hardwoods versus softwoods), a result of differences in litter quality and atmospheric aerosol interception capacity. The correlation between lysimeter and IER data for individual analytes varied greatly. Significant correlations were evident for Na (r=0.75), Al (r=0.65), Mn (r=0.61), Fe (r=0.57), Ca (r=0.49), K (r=0.41) and NO₃—N (r=0.59). No correlation was evident between IER and soil solution data for NH₄—N and Pb. Both IER and soil solution techniques suggested similar interpretations of biogeochemical behavior in the watershed.     

WATER PROBLEMS IN THE INDUS FOOD MACHINE1

ABSTRACT: Examples are drawn from the Indus Basin to explain why on-farm water management problems restrict the output of agricultural products in many LDC's. Data is presented to illustrate the low level of water management knowledge of both the farmers and the current extension agents. Examples of the level of corruption and its effect on the operating system are illustrated. Several requirements that must be met before a large-scale irrigation scheme will actually increase the welfare of LDC's farmers are presented.     

The Southeastern Aerosol Research and Characterization Study: Part II. Filter-based measurements of fine and coarse particulate matter mass and composition

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 (PM2.5) and coarse particulate matter (PM10-2.5) in the Southeastern United States. This work is an initial analysis of 5 years (1999-2003) of filter-based PM2.5 and PM10-2.5 data from SEARCH. We find that annual PM2.5 design values were consistently above the National Ambient Air Quality Standards (NAAQS) 15 microg/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 microg/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 PM2.5 underestimates mass by 3-7% as a result of these volatilization losses. Organic matter (OM) and sulfate account for approximately 60% of PM2.5 mass at SEARCH sites, whereas major metal oxides (MMO) and unidentified components ("other") account for > or = 80% of PM10-2.5 mass. Limited data suggest that much of the unidentified mass in PM10-2.5 may be OM. For paired comparisons of urban-rural sites, differences in PM2.5 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 PM2.5 and PM10-2.5 mass and major components demonstrate substantial declines at all of the SEARCH sites over the 1999-2003 period (10-20% in the case of PM2.5, dominated by 14-20% declines in sulfate and 11-26% declines in OM, and 14-25% in the case of PM10-2.5, 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.