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Sixty-four bottom ash (BA) samples from indoor burning of eight bio-fuels (BFs) including cotton (COT), corn (COR), millet (MIL), soybean (SOY), sorghum (SOR) and sesame (SES), firewood walnut (WAL), and corn cob (COC) were collected across the Beijing-Tianjin-Hebei (BTH) region. Each BA was divided into five differently sized parts for the analysis of eighteen PAHs using the GC/MS system. The Σ18PAHs values for all the BAs varied from 65.0 ± 10.6 to 1310 ± 129 ng g–1. SOR had the highest PAH level, and COC produced the lowest level. The Σ18PAHs for SOY, WAL, COT, COR, COC, and SES were negatively correlated with the BA sizes. The NA, PHE, ACL, AN, FA, PY, FL, and AC dominated in all the BAs except for SES. All the BAs were dominated by 2, 3-ring PAHs. The PAH profiles for differently sized BAs within MIL, SOR, COC, COR, and SES were similar based on lower coefficient of divergence values, while the other three BFs did not exhibit this trend. All the BF pairs except for SOR vs. SES and COC vs. COR had the different PAH profiles. No series of coincident diagnostic ratios (DRs) could represent all BFs based on their significantly varied DRs. AN/(AN + PHE) and BA/BgP might be used in identification of combustion sources of different types of BFs. SOR and SES had higher potential toxicity risk based on higher TEQ, BaPE, and CPAHs values. BgF and BgP were the indicatory PAHs for SOY, MIL, COR, SOR, and COC, while they were AC and FL for the remaining three BFs.

The chemical profiles of emission sources are indispensable for source apportionment using receptor models. To develop current knowledge of PM10 profiles, the chemical composition of major emission sources were analyzed in Xining. Samples of geological sources (soil dust, road dust and construction derived dust) and industrial fly ash were collected from representative portions using a plastic dustpan and brush and sampled on filters through a re-suspension chamber. Samples of coal combustion source and vehicle exhaust were collected directly on the filters using a dilution stack sampler. Chemical analysis included inductively coupled plasma mass spectrometry for 19 elements (Na, P, K, As, Rb, Mo, Cd, Sn, Sb, La, V, Cr, Mn, Co, Ni, Cu, Zn, T1, and Pb), inductively coupled plasma optical emission spectrometry for 7 elements (Al, Sr, Mg, Ti, Ca, Fe, and Si), ion chromatography for water-soluble ions (Na + , K + , Mg 2+ , Ca 2+ , F – , Cl – , NO3 – and SO4 2– ) and thermal/optical reflectance analysis for carbonaceous species. Crustal elements (Si, Al, Ca, Fe) predominated in geological sources, whereas trace elements (Pb, Cd, Cr, Zn and Ni) were predominant in industrial fly ash. An abundance of carbon and SO4 2– was present in coal-combustion source and vehicle exhaust. The coal-combustion boilers were a source of trace elements (Ti, Co, Sr, Sb, Tl). High concentrations of Pb and OC in soil indicated the strong influence of agriculture activities in Xining. Comparison of vehicle exhaust profiles indicated that natural gas was high environmental friendliness in comparison with petroleum products used as motor vehicles fuel. Differences in EC, Cd and NO3 – between natural gas-powered and gasoline- or diesel-powered vehicle exhaust can be used to differentiate the two types of vehicle emission sources. Differences in source profiles and indicator species between Xining and other cities suggest that source profiles should be developed locally and updated frequently.