3506B24 Final Report
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with cn,sv denoting the semi-volatile fraction of species n, estimated under the assumption that individual denuder break-throughs of corresponding gas-phase species (for Φn,tot <1) adsorb exclusively on the front filter, thus being calculated as follows: 
for tandem backup glass fiber filters as used here in PCM channel 2 of the ambient samples; and 
for single backup glass fiber or paper filter, which was the setup of PCM channels 1 at the source and ambient site, respectively. The cn,ion(G1/G2/GB/P/PB) denote the concentration of species n from glass fiber filter1/filter2/blank, or from single glass/paper/blank filters, respectively. Since no phosphorous acid coated backup adsorber is available in the ambient PCM’s channel 2, the PPA filter in channel 1 substitutes for the GSC filter used for the anions. Again, Φn,tot is assumed to be 1 with the exception of acetate, formate, and oxalate. Also, the semi-volatile fraction of nitrate is determined from the difference between the first and second GSC backup filter in channel 2, because of the potential artifact induced by the heterogeneous O3 reaction with adsorbed NO2. Organic and elemental carbon (OC/EC) are determined from the quartz filters in channel 3 and 2 of the ambient and source PCM, respectively, as follows 
where cOC/EC(Q/QB) is the concentration of OC/EC from the quartz filter/blank, respectively. Under the similar assumption from above, where semi-volatile OC that break-through the C-monolith denuder (CM’s Φtot <1) adsorb or condense exclusively onto the front Q filter, “semi-volatile” OC (svOC) is derived from the XAD coated quartz backup filter (XQ) considering OC levels found on a field blank (XQB): 
5.3.2 High-Volume Samples for POC Speciation The HVS were collected on pre-baked 8″x10″ quartz filters using two high volume samplers with a flow rate of 1130 lpm each. The filter samples were covered with aluminum foil and stored in the freezer before organic speciation analysis. Between 87 and 108 organic species including n-alkanes, n-alkanoic acids, polycyclic aromatic hydrocarbons (PAH), steranes, hopanes, resin acids, aromatic diacids, and some key tracer compounds serving as specific markers for biomass burning, e.g. levoglucosan, certain resin acids (pimaric acid, sandaraco-pimaric acid, abietic acid), and the PAH retene were identified and quantified in the samples. The list of the organic compounds quantified is summarized in Table 14. The following describes the processes involved for the chemical analysis and the procedures followed to achieve highest data quality. - Chemical analysis As part of the routine extraction procedure, the samples were spiked with a mix of deuterated Internal Standards (IS) containing 16 isotopically labeled compounds: benzaldehyde-d6, dodecane-d26, decanoic acid-d19, phthalic acid-3,4,5,6-d4, acenaphthene-d10, levoglucosan-13C6 (carbon-13 uniform-labeled compound), hexadecane-d34, eicosane-d42, heptadecanoic acid-d33, 4,4’-dimethoxy-benzophenone-d8, chrysene-d12, octacosane-d58, ααα-20R-cholestane-d4, cholesterol-2,2,3,4,4,6-d6, dibenz-[ah]anthracene-d14, and hexatriacontane-d74. The volume of the IS mix spiked was determined by the Organic Carbon (OC) content in each sample, with 250 l per one mg of OC. The samples were extracted successively with hexane twice, then with a 2:1 mixture of benzene and 2-propanol three times by mild sonication for 15 min at room temperature. The extracts were filtered, combined, and concentrated to 5-10 ml by rotary evaporation. The extracts were then further blown down to roughly 250 l by gentle nitrogen gas flow (<2 psi). The final extract was then equally split into two halves: one was for archive and the other was derivatized with diazomethane to convert organic acids to their methyl esters. The derivatized extracts were then subject to gas chromatography/mass spectrometry (GC/MS) analysis. Download 11.49 Mb. Share with your friends:
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