Intermediate volatility organic compound (IVOC) emissions from a large cargo vessel were characterized under realworld operating conditions using an on-board measurement system. Test ship fuel-based emission factors (EFs) of total IVOCs were determined for two fuel types and seven operating conditions. The average total IVOC EF was 1003 ± 581 mg•kg-fuel −1 , approximately 0.76 and 0.29 times the EFs of primary organic aerosol (POA) emissions from low-sulfur fuel (LSF, 0.38 wt % S) and high-sulfur fuel (HSF, 1.12 wt % S), respectively. The average total IVOC EF from LSF was 2.4 times that from HSF. The average IVOC EF under low engine load (15%) was 0.5−1.6 times higher than those under 36%−74% loads. An unresolved complex mixture (UCM) contributed 86.1 ± 1.9% of the total IVOC emissions. Ship secondary organic aerosol (SOA) production was estimated to be 546.5 ± 284.1 mg•kg-fuel −1 ; IVOCs contributed 98.9 ± 0.9% of the produced SOA on average. Fuel type was the dominant determinant of ship IVOC emissions, IVOC volatility distributions, and SOA production. The ship emitted more IVOC mass, produced higher proportions of volatile organic components, and produced more SOA mass when fueled with LSF than when fueled with HSF. When reducing ship POA emissions, more attention should be paid to commensurate control of ship SOA formation potential.

Nitrite (NO 2 − ) and its conjugate acid, nitrous acid (HNO 2 ), have long been recognized as a ubiquitous atmospheric pollutant as well as an important photochemical source of hydroxyl radicals (•OH) and reactive nitrogen species (•NO, • NO 2 , •N 2 O 3 , etc.) in both the gas phase and aqueous phase. Although NO 2 − /HNO 2 plays an important role in atmospheric chemistry, our understanding on its role in the chemical evolution of organic components in atmospheric waters is rather incomplete and is still in dispute. In this study, the nitrite-mediated photooxidation of vanillin (VL), a phenolic compound abundant in biomass burning emissions, was investigated under pH conditions relevant for atmospheric waters. The influence of solution pH, dissolved oxygen, and •OH scavengers on the nitrite-mediated photooxidation of VL was discussed in detail. Our study reveals that the molecular composition of the products is dependent on the molar ratio of NO 2 − /VL in the solution and that nitrophenols are the major reaction products. We also found that the light absorbance of the oxidative products increases with increasing pH in the visible region, which can be attributed to the deprotonation of the nitrophenols formed. These results contribute to a better understanding of methoxyphenol photooxidation mediated by nitrite as a source of toxic nitrophenols and climatically important brown carbon in atmospheric waters.

Accurate physical-chemical properties are of fundamental importance for interpreting and simulating the environmental fate and transport behavior of polycyclic aromatic hydrocarbons (PAHs). A complete set of thermodynamically consistent property data (vapor pressure, aqueous solubility, octanol solubility, octanol−water partition coefficient, octanol−air partition coefficient, and air−water partition coefficient) for 15 PAHs [naphthalene (Nap), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fluo), phenanthrene (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr), chrysene (Chry), benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DBA), indeno[1,2,3-c,d]pyrene (IP), and benzo[g,h,i]perylene (BghiP)] is derived from measured data reported in the literature. First, literature-derived values (LDVs) at 25 °C for each property and compound are obtained by averaging, regression, and extrapolation. Then the LDVs for each compound are adjusted to conform to the thermodynamic relationships between them using a least-squares adjustment procedure. The influence of the mutual solubility of octanol and water on phase partitioning is taken into account in the adjustment of K OW. Compared to other semivolatile organic compounds, the LDVs for the PAHs display a high degree of thermodynamic consistency and require only minor adjustments. The LDVs and the adjusted values for all properties show highly linear regressions with molar mass.

Fe(III)−oxalate complexes are likely abundant in clouds, fogs and aerosol water. They are photoreactive and can act as an important source of reactive oxygen species ( • OH, H 2 O 2 and HO 2 •) in tropospheric aqueous phases. Although the mechanisms involved in ferrioxalate photolysis have been investigated extensively, few kinetic and mechanistic information is available on the aging of dissolved organic compounds by this photochemical system. In this work, the Fe(III)−oxalate mediated photooxidation of guaiacol (GUA), a model for phenolic compounds emitted from biomass burning, was investigated under typical pH conditions of the atmospheric water. The effect of Fe(III) concentration, oxalate concentration and pH on the photooxidation of GUA was studied in detail. Our results revealed that oxalate can inhibit the oxidation of GUA by Fe(III) under the dark condition. However, the iron-catalyzed photooxidation of GUA can be strongly promoted in the presence of oxalate due to the formation of photoactive Fe(III)−oxalate complexes. GUA was rapidly oxidized to form a number of polymeric, functionalized and open-ring products with low volatility. Detailed reaction pathways for the photooxidation of GUA by Fe(III)−oxalate complexes were proposed based on the results of high-resolution mass spectrometry. This work suggests that ferrioxalate photochemistry can play an important role in the transformation of dissolved organics in atmospheric aqueous phases.