Size-segregated sampling

Certain measurements cannot be made in the field, and for these it is necessary to collect samples for transport to the sorts of instruments that are available only in laboratories. Collection of size-segregated samples can be achieved by the use of a cascade impactor, which consists of a series of apertures of decreasing diameter, each of which is above a matched, stacked collection... 

To account for inhomogeneity in bubble sizes, d in Eq. (20-52) should be taken as / Ln,dffLn,d, and evaluated at the top of the vertical column if coalescence is significant in the rising foam. Note that this average d for overflow differs from that employed earlier for S. Also, see Bubble Sizes regarding the correction for planar statistical sampling bias and the presence of size segregation at a wall. 

Given these data, what statements can we make about the number and size of samples that would have to be taken to hold the sampling standard deviation to some prescribed level Calculation of Ingamell subsampling constant is not appropriate since segregation is present. 

Comparisons Between Size-Segregated Resuspended Soil Samples and Ambient Aerosols in the Western United States... 

Dibenzo[a,/]pyrene, a potent mutagen in the MCL-5 assay, was not detected in this analysis of SRM 1649. However, this 6-ring PAH XXIX was identified (but not quantified) by comparison to an authentic standard by Allen and co-workers (1998) in their analysis of size-segregated aerosols in urban Boston ambient air. Furthermore, in their August 1994 study of biologically active, particle-associated PAHs in ambient Riverside, California, Atkinson and Arey (1997) measured concentrations of 18, 20, and 15 pg m-3 of this compound for one daytime and two nighttime sampling events, respectively. These concentrations were 40-50% of the BaP concentrations in the same aerosol samples. 

Compositional Analysis of Size-Segregated Aerosol Samples... 

Cahill Wakabayashi Analysis of Size-Segregated. Aerosol Samples 215... 

Jalava PI, Salonen RO, Halinen AI, Penttinen P, Pennanen AS, Sillanpaa M, Sandell E, Hillamo R, Hirvonen M-R (2006) In vitro inflammatory and cytotoxic effects of size-segregated particulate samples collected during long-range transport of wildfire smoke to Helsinki. Toxicol Appl Pharmacol 215 341-353... 

Therefore, sampling procedures are of the greatest importance in order to reduce the effect of nonuniform size segregation and nonrandom homogeneity of a system to achieve statistically meaningful sampling results. Careful attention and faithful observance must be demonstrated and it is extremely important that sampling occurs when the powders are in motion [6] and samples are withdrawn from the whole stream for equal periods of time, rather than part of the stream for all of the time [3]. 

Powdered material is poured into a cone and divided into four equal parts. One quarter is recovered and the process was repeated until the required weight of sample is obtained. This method is prone to operator bias, as finer particles tend to remain in the center of the cone because of size segregation. Symmetry of the cone is also quite difficult to achieve but is necessary for accuracy, so this method is not recommended. ... 

We mounted samples of feed coal in epoxy resin under hydraulic pressure as described by Cole and Berry (2). An apparatus and procedure for vacuum-mounting the fragile chars was developed ana is described elsewhere (8). Samples of pretreated coal and hydrogasification residue were sieved, and tests were made on the sieve fractions to avoid error from size segregation. 

The mass concentrations of the size segregated gravimetric particle were measured by weighing each filter before and after sampling in two measurement periods. 

Rather unusually Adams and Baker analysed the discharge from the mixer rather than the more conventional in situ analysis. Results are thus given in sequential form and despite the scatter rtf the individual samples it is possible to identify trends of segregation. Sample size is not quoted, but as only twenty-five or so black particles were counted in each sample it is likely that the sample is coarse grained and will reflect quite wide variations due to local patchiness of the black polythene component. 

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