Denuder sampling

Perrino, C., F. De Santis, and A. Febo, Criteria for the Choice of a Denuder Sampling Technique Devoted to the Measurement of Atmospheric Nitrous and Nitric Acids, Atmos. Environ., 24A, 617-626 (1990). 

Because of the labor-intensive nature of annular denuder sampling, alternative techniques deserve further scrutiny. The DDM, relying on Teflon-nylon filter packs (or nylon filters alone) and an anodized aluminum annular denuder ahead of one of a pair of modified dichotomous samplers (46), merits evaluation for the influence of potential interferents (e.g., HONO). The DDM with NaCl-coated denuders would probably be nearly free of interference from HONO, but this conclusion requires evaluation. Because coarse particulate N03 must be excluded to achieve improved accuracy for HN03 and fine particulate N03, supplementary samplers are needed to obtain improved estimates of total as well as coarse particulate... 

Tang, H., E.A. Lewis, D.J. Eatough, R.M. Burton, and R.J. Farber. 1994. Determination of the particle size distribution and chemical composition of semi-volatile organic compounds in atmospheric fine particles with a diffusion denuder sampling system. Atmos. Environ. 28 939-947. 

Nordqvist, Y., Nilsson, U., and Colmsjo, A., Evaluation of denuder sampling for a mixture of three common gaseous diisocyanates, Ana/. Bioanal. Chem., 375, 786-791, 2003. 

Perrino C, Catrambone M, Esposito G et al (2009) Characterisation of gaseous and particulate atmospheric pollutants in the East Mediterranean by diffusion denuder sampling lines. Environ Monit Assess 152 231-244... 

Perrino C, Catrambone M, Esposito G, Lahav D, Mamane Y (2009) Characterisation of gaseous and particulate atmospheric pollutants in the East Mediterranean by diffusion denuder sampling lines. Environ Monit Assess 152(l )/may 2009 Viswanadham DV, Santosh KR (1990) On the application of the Gaussian model for multiple industrial sources for selected centres in South India. Bound-Layer Meteorol 53(1-2) 173-184... 

In annular denuder sampling, potassium iodide (20 g KI in 10 ml of deionized water + 10 ml of 10% glycerol in methanol), phenoxazine (0.4 g in 20 ml of acetone), and 4-allyl-2-methoxyphenol (eugenol, 10% in methanol) are used as absorbents. The third absorbent releases formaldehyde by ozonolysis, which is collected with another downstream denuder coated with 2,4-dinitrophenylhydrazine (0.5% in acetonitrile containing 1% phosphoric acid). 

Couphng of the annular denuder sampling techniques with ion chromatography provides a valuable solution to the problem of precise and accurate measurement of atmospheric inorganic pollutants, with discrimination of the gaseous and the particulate phase. 

Kito, A-JVUM. and Colbeck, I. (1999) Filtration and denuder sampling techniques, in Analytical Chemistry of Aerosols (ed. K.R. Spumy), CRC Press, Chapter 4, pp. 103-132. 

Paolini, 1986 Stallard, 1980). Comparison with Fig. 9-7 shows a reasonable match between denudation rates and uplift rates for a particular type of terrain. The most concentrated water samples and highest denudation rates are observed in river basins in tectonically active areas. 

Fig. 9-8 Histogram of dissolved solids of samples from the Orinoco and Amazon River basins and corresponding denudation rates for morpho-tectonic regions in the humid tropics of South America (Stal-lard, 1985). The approximate denudation scale is calculated as the product of dissolved solids concentrations, mean armual runoff (1 m/yr), and a correction factor to account for large ratios of suspended load in rivers that drain mountain belts and for the greater than average annual precipitation in the lowlands close to the equator. The correction factor was treated as a linear function of dissolved solids and ranged from 2 for the most dilute rivers (dissolved solids less than lOmg/L) to 4 for the most concentrated rivers (dissolved solids more than 1000 mg/L). Bedrock density is assumed to be 2.65 g/cm. (Reproduced with permission from R. F. Stallard (1988). Weathering and erosion in the humid tropics. In A. Lerman and M. Meybeck, Physical and Chemical Weathering in Geochemical Cycles," pp. 225-246, Kluwer Academic Publishers, Dordrecht, The Netherlands.)...

Possanzini M, Febo A, Liberti A. 1983. New design of a high-performance denuder for the sampling of atmospheric pollutants. Atmos Environ 17 2605-2610. 

As is the case for other types of sampling systems, artifacts can occur, e.g., evaporation of semivolatile PAHs from the particles as the gas phase is removed by the denuder surface (e.g., see Kamens and Coe, 1997 and Feilberg et al., 1999a). For information on the design, operation, and accuracy and precision of various types of denuder systems, see Chapter ll.A.3b and, for example, Coutant et al. (1988, 1989, 1992), Eatough... 

A variety of methods have been used to collect gases for subsequent quantification by techniques such as ion chromatography or colorimetric or other (e.g., electrochemical) analyses. These include filter methods, denuders, transition flow reactors, and scrubbers. Sampling must be carried out for sufficient periods of time to collect measurable amounts of the species of interest. From the total volume of air sampled and the amount of the analyte measured, the average concentration of the species in air over the collection period can be calculated. These techniques do not provide real-time analyses, although collection periods as short as 0.5 h provide sufficient sample for analysis in some cases. 

Denuders have been used in several different ways. One is to extract the walls of the denuder and measure the adsorbed gas directly by ion chromatography. Denuders have also been used as difference denuders. For example, in nitric acid measurements, the combination of gas-phase HNO-, and particle nitrate has been measured using a nylon filter or Teflon-nylon filter combination in one sampling train. In a parallel sampling train, particulate nitrate alone is measured by first passing the airstream through a denuder to re-... 

The use of tandem denuders, each with the same coating, permits at least partial correction for these sources of error in HN03 measurement. Species retained with low efficiency on carbonate coatings (e.g., NO and PAN) are collected in about equal amounts by successive denuders. If it is assumed that oxidation during and subsequent to sampling occurs equally on successive denuders as well as in their corresponding extracts, the N03 from the second denuder extract can be subtracted from that in the front denuder extract to obtain a measure of atmospheric HN03. However, this technique does not correct for the efficient retention (and subsequent oxidation) of atmospheric or artifact HONO. 

Uncertainty in Correcting Atmospheric Data. The level of uncertainty with this method can be illustrated with results from atmospheric trials (57). After 4- to 6-h samples were collected in Southern California with CO -glycerol coated annular denuders during a late fall period, the N03" recovered... 

In addition to greatly increasing the sampling and analytical requirements, if other acidic gases are to be measured the NaCl-coated denuder may show decreased efficiency at low RH. Forrest et al. (13) observed a sharp decrease in HN03 collection efficiency with NaCl-coated filters at 25% RH. Similar studies with denuders have not been reported, however. A comparison of atmospheric HN03 results with the ADM using NaX-coated denuders with those by reference procedures has not been reported, so the accuracy of the method remains to be confirmed. 

Diffusion Denuders for Specific Organic Compounds. Diffusion de-nuder techniques have been applied successfully to sampling individual organic materials, including pesticides (82), nicotine (83, 84), and PAH compounds (63). The methodology and results relating to PAH compounds are detailed here. 

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