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Because the particulate organic carbon (OC) concentrations reported in U.S. Environment Protection Agency Speciation Trends Network (STN) data were not blank corrected, the OC blank concentrations were estimated using the intercept in particulate matteror = 2.5 microm in aerodynamic diameter (PM2.5) regression against OC concentrations. The estimated OC blank concentrations ranged from 1 to 2.4 microg/m3 showing higher values in urban areas for the 13 monitoring sites in the northeastern United States. In the STN data, several different samplers and analyzers are used, and various instruments show different method detection limit (MDL) values, as well as errors. A comprehensive set of error structures that would be used for numerous source apportionment studies of STN data was estimated by comparing a limited set of measured concentrations and their associated uncertainties. To examine the estimated error structures and investigate the appropriate MDL values, PM2.5 samples collected at a STN site in Burlington, VT, were analyzed through the application of the positive matrix factorization. A total of 323 samples that were collected between December 2000 and December 2003 and 49 species based on several variable selection criteria were used, and eight sources were successfully identified in this study with the estimated error structures and min values among different MDL values from the five instruments: secondary sulfate aerosol (41%), secondary nitrate aerosol (20%), airborne soil (15%), gasoline vehicle emissions (7%), diesel emissions (7%), aged sea salt (4%), copper smelting (3%), and ferrous smelting (2%). Time series plots of contributions from airborne soil indicate that the highly elevated impacts from this source were likely caused primarily by dust storms.

Design and main principles of clean geochemical lab are reviewed with a focus on practical aspects of the clean room operations. Also discussed are techniques for reduction of air pollution by aerosols, purification of water and reagents that lead to low total procedural blank which is essential for obtaining accurate analytical data for small geochemical samples. Examples of low blank geochemical analysis and/or contamination issues include Pb analysis in zircons, Sr analysis by micromilling, meteoritic Ag, Re–Os, high-field-strength elements and W, and Li.

Systematic errors can occur when airborne dust is sampled with an impactor for subsequent element analysis. As could be shown, blank values, collection losses and memory effects are caused by the impactor and the material it is made of. Four different materials were chosen to build up a two-stage Battelle type impactor: Makrolon®, titanium, aluminium and stainless steel. The latter was applied without and with a coating of TiN. Air dust was collected on Vaseline® coated impaction plates and directly analyzed by total reflection X-ray fluorescence (TXRF). Up to 15 elements were determined simultaneously after internal standardization. Blank values arising from the impactor walls in contact with the gas flow were measured by sampling air from a clean bench. Relative collection losses were determined by sampling ambient air with two impactors in parallel and by comparing the two sets of results. Memory effects were measured by first collecting airborne particulates and then, after having replaced the impaction plates, pulling air through the impactor in a clean bench. The three effects led to relative systematic errors of a few % up to several 10% depending on element and impactor material. Stainless steel causing the largest errors has to be considered the least suitable material, even if coated with TiN. Aluminium led to moderate systematic deviations. Only titanium and Makrolon® were proven to be widely suitable impactor materials, the latter one, however, only when short sampling periods are applied.

Use of solid adsorbents for air sampling always raises questions of adequate retention, blank corrections and artifact formation. Universally valid answers to these questions are unavailable. Collection of a small set of data by sampling over a large range of air volume can provide situation-specific indications of data quality not possible with the more usual tandem bed approach. Further, it does so in a direct simple way that is especially useful in monitoring applications. The distributed air volume sampling approach is illustrated using Tenax as the adsorbent.

A method is described in which spectroscopic graphite electrodes are used as filters for atmospheric particulates and are analyzed for several elements directly by an emission spectrographic method. The sampling system and the analysis method are described and an evaluation of the approach is presented. The results indicate that several elements can be accurately determined at atmospheric concentrations ranging down to the parts pcr billion level with minimal filter blank problems. (auth)