The international journal of Aerosol and Air Quality Research (AAQR) covers all aspects of aerosol science and technology, atmospheric science and air quality related issues.

This study reported the chemical compositions of PM_2.5 for seven kinds of China IV diesel trucks and three kinds of stage II construction equipment. Filter samples were directly collected at the tailpipe with a dilution system. Twenty elements (Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sn, Sb, Ba and Pb), water-soluble ions (WSIs) including NH₄⁺, K⁺, Ca²⁺, Cl⁻, NO₃⁻ and SO₄²⁻, and carbonaceous species were analyzed and characterized. The uncertainties of these species were also estimated. Overall, the highest proportion of PM_2.5 was contributed by carbonaceous matter (OC and EC), accounting for 46.4 and 38.5% for trucks and construction equipment, respectively. The EC/OC ratios were higher than 1, with lowest in light-duty diesel trucks (LDDTs) as 1.4 ± 0.2 and highest in excavators as 5.1 ± 0.3. Similarities and differences were compared among source profiles using the residual (R)/uncertainty (U) ratios. Also Pearson’s correlation coefficients among the chemical compositions were analyzed to determine the relationships between the various chemical components. In addition, the source profiles of diesel trucks and construction equipment in our study were compared with those reported by other studies in recent years from China. Variations were observed in the results due to uncontrolled factors such as operating conditions, fuel quality and sampling measurements. To assess these uncertainties, better knowledge of local source profiles and more elaborate measurements are needed for future research.

The mechanism of the chemical reaction of H₂O with three stabilized Criegee intermediates (stabCI-OO, stabCI-CH₃-OO and stabCIx-OO) produced via the limonene ozonolysis reaction has been investigated using ab initio and DFT (Density Functional Theory) methods. It has been shown that the formation of the hydrogen-bonded complexes is followed by two different reaction pathways, leading to the formation of either OH radicals via water-catalyzed H migration or of α-hydroxy hydroperoxide. Both pathways were found to be essential sources of atmospheric OH radical and H₂O₂ making a significant contribution to the formation of secondary aerosols in the Earth’s atmosphere. The activation energies at the CCSD(T)/6-31G(d) + CF level of theory were found to be in the range of 14.70–21.98 kcal mol⁻¹. The formation of α-hydroxy hydroperoxide for the reaction of stabCIx-OO and H₂O with the activation energy of 14.70 kcal mol⁻¹ is identified as the most favorable pathway.

As a carcinogenic pollutant, hexavalent chromium (Cr(VI)) in the ambient air has serious influences on public health. Due to its instability and difficulty in chemical analysis, few studies have been conducted on the regional concentration level of environmental Cr(VI), especially in China. The pollution levels of Cr(VI) in ambient PM_2.5 were determined in two sampling sites of Beijing and Qingdao from September to December 2020. The concentrations of Cr(VI) were determined using Ion Chromatography-inductively coupled plasma mass spectrometry(IC-ICP-MS), and the Cr concentrations were simultaneously analyzed by Inductively Coupled Plasma-atomic emission spectrometry(ICP-AES). The main results are as follows: (1) Based on the analysis of samples collected at the sampling sites of Beijing and Qingdao, the concentrations of Cr(VI) in PM_2.5 were (0.140 ± 0.065) ng/m³ and (0.091 ± 0.073) ng/m³, respectively; (2) During the sampling period, the mean ratio of Cr(VI) to Cr was (0.0623 ± 0.0969). The ratio of Cr(VI)/Cr in Beijing and Qingdao were 0.076 ± 0.104 and 0.041 ± 0.039, respectively. In conclusion, compared with other countries, the concentration of Cr(VI) at the sampling sites of Beijing and Qingdao showed lower values. The average concentration of Cr(VI) estimated by the ratio of this research in China is lower than that in South Korea and similar to those in Canada and Australia.

Ninety-six particulate matter (PM₁₀) chemical source profiles for geological sources in typical cities of southwest China were acquired from Source Profile Shared Service in China. Twenty-six elements (Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Sr, Cd, Sn, Sb, Ba, Be, Tl and Pb), nine ions (F⁻, Cl⁻, SO₄²⁻, NO₃⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺), and carbon-containing species (organic carbon and elemental carbon) were determined to construct these profiles. Individual source profiles were averaged and compared to quantify similarities and differences in chemical abundances using the profile-compositing method. Overall, the major components of PM₁₀ in geological sources were crustal minerals and undefined fraction. Different chemical species could be used as tracers for various types of geological dust in the region that resulted from different anthropogenic influence. For example, elemental carbon, V and Zn could be used as tracers for urban paved road dust; Al, Si, K⁺ and NH₄⁺ for agricultural soil; Al and Si for natural soil; and SO₄²⁻ for urban resuspended dust. The enrichment factor analysis showed that Cu, Se, Sr and Ba were highly enriched by human activities in geological dust samples from south-west China. Elemental ratios were taken to highlight the features of geological dust from south-west China by comparing with northern urban fugitive dust, loess and desert samples. Low Si/Al and Fe/Al ratios can be used as markers to trace geological sources from southwestern China. High Pb/Al and Zn/Al ratios observed in urban areas demonstrated that urban geological dust was influenced seriously by non-crustal sources.