Aerosol measurements, enrichment factors

Iron was chosen as the reference element because its major source is likely to be soil and it is measured with good accuracy and precision by FIXE. Crustal abundances were taken from Mason (21). Enrichment factors greater than 1 indicate an enrichment of that element relative to crustal abundances values less than 1 indicate a depletion. The results of this calculation are shown in Table 4. For this calculation it was assumed that ammonium and nitrate accounted for all aerosol nitrogen. It is seen that Si and Ca are near their crustal abundance, indicating a probable soil dust source. The low EF for Al is probably due to a systematic error in the Al measurement rather than a true depletion. Potassium, although present in small concentrations, is slightly enriched relative to crust. The other fine aerosol species, C, N, S, and Pb are enriched by factors of thousands over their natural crustal abundance, indicating that they are not due to wind-blown dust. 

Measurement of Cd in the atmosphere and in rain and snow at various locations on the globe indicate that the primary source of Cd to the atmosphere is anthropogenic and show a pronounced latitudinal gradient in deposition [27,28,33-35]. The deposition of Cd in precipitation and bulk aerosol samples is observed to occur at significant crustal enrichment factors (EFc) where... 

Sea salt contains (by weight) 55.7% Cl, 0.19% Br, and 0.00002% I. Depletion of the Cl and Br content of marine aerosol relative to bulk seawater, as measured by Cl/Na and Br/Na ratios, indicates that there is some net flux of these two halogens to the gas phase. Interestingly, the ratio I/Na in marine aerosol is typically much greater than that in seawater, often by a factor of 1000. The large enrichment for iodine in seasalt aerosols relative to seawater has been attributed, in part, to the enhanced level of organic I compounds in the surface organic layer on the ocean that become incorporated in the aerosol formation mechanism. 

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