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We investigated the concentrations and seasonal variations of organophosphate esters (OPEs) in the gas phase and PM 2.5 (particulate matter with an aerodynamic diameter <2.5 μm) in an urban area of Dalian, China, as well as their gas-particle partitioning. The total concentrations of OPEs in the gas phase were in the range of 0.056–6.38 ng/m3 with the mean concentration of 0.83 ± 1.24 ng/m3, while the concentrations of OPEs in the PM 2.5 were in the range of 0.32–3.46 ng/m3 with the mean concentration of 1.21 ± 0.67 ng/m3. Tris-(1-chloro-2-propyl) phosphate (TCIPP) was the dominant congener in the gaseous phase, followed by tris-(2-chloroethyl) phosphate (TCEP) and tri- n -butylphosphate (TNBP), whereas TCEP was the dominant species in the PM 2.5 , followed by TCIPP and triphenyl phosphate (TPHP). Seasonality was discovered for OPEs in both gas phase and PM 2.5 with their concentrations higher in hot seasons, which may due to the temperature-driven emission or gas-particle partitioning. The PM 2.5 -bound fractions of OPEs varied significantly between seasons. Tricresyl phosphate (TMPP), tri(2-ethylhexyl) phosphate (TEHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and TPHP were mostly adsorbed onto fine particles, while TNBP, TCEP, TCIPP, and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) distributed in both gas and fine particle phases. The predicted PM 2.5 -bound fractions by K oa -based model were closer to the measurements for TCIPP, TDCIPP, and TPHP, whereas the predictions by Junge-Pankow model were closer to the measurements for TMPP and tris (2-butoxyethyl) phosphate (TBOEP). However, the predictions of both models cannot accurately match the measured gas-particle partitioning of TNBP and TCEP. Image 1 • Gas-PM 2.5 partitioning of organophosphate esters was investigated in an urban area. • OPEs may transfer from coarse to fine particle or gas with increasing temperature. • Tris-(1-chloro-2-propyl) phosphate distributed in both gas and particle phases. • Predicted OPE gas-PM 2.5 partitioning was significant different with that measured. TNBP, TCEP, TCIPP, and TDCIPP distributed in both gas and fine particle phases, while TPHP, TEHP, EHDPP, and TMPP were mostly in the particle phase. [ABSTRACT FROM AUTHOR]

Samples of gas and fine particulate matter (PM 2.5) were collected in Dalian, China, a typical coastal city, to determine the concentrations, seasonal variations, influential factors, sources, and gas-PM 2.5 partitioning of polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), and dechlorane plus (DPs) in the ambient air. Annual average concentrations of Σ 7 PBDEs, BDE209, Σ 6 NBFRs, and DPs were 4.40 ± 2.93, 1460 ± 2500, 7.81 ± 6.85, and 0.15 ± 0.14 pg/m3 for the gas phase, and 2.68 ± 1.64, 4291 ± 4306, 13.6 ± 23.4, and 0.31 ± 0.22 pg/m3 for the fine particle phase, respectively. BDE209 was the dominant congener, followed by HBB and BEH-TEBP, and seasonal variations in air concentrations were apparent for BFRs, especially those in the gas phase. Moreover, meteorological parameters and criteria air pollutants revealed significant positive correlations between temperature and less-brominated BFRs in the gas phase, and between PM 2.5 and highly-brominated BFRs in the particle phase. This suggests that the presence of these compounds in ambient air may largely result from combustion-related processes. Furthermore, an analysis of the gas-PM2.5 partitioning of BFRs and DPs suggested that BFRs and DPs mostly attained equilibrium, except for some NBFRs. Due to the ban of commercial penta-, octa-, and deca-BDEs by the Stockholm Convention, emissions from historical use and combustion are becoming the important sources of PBDEs in China. Image 1 • Temperature, degradation, and combustion significantly affected air levels of BFRs. • Gas-PM 2.5 partitioning of BFRs and DPs suggested most of them reached equilibrium. • PBDE emission from historical use or combustion still continues despite their ban. [ABSTRACT FROM AUTHOR]

Abstract Concentrations and temporal variations of priority polycyclic aromatic hydrocarbons (PAHs) in the air from a suburban area of Dalian, China were investigated for a 1-year period to assess their sources and potential correlations with six criteria air pollutants and meteorological parameters. The total concentrations of PAHs were in the range of 4.32–112.2 ng/m3 (Mean = 52.37 ± 23.99 ng/m3). Seasonality was discovered with the PAHs following an order of winter > spring > summer > autumn. The impacts of meteorological parameters on PAH levels were season-dependent. High temperature may increase the air concentrations of 4-ring PAHs during the non-heating period, whereas high relative humidity may raise the concentrations of 3- and 4-ring PAHs during the heating period. Correlations of PAHs with criteria air pollutants, such as SO 2 , NO 2 , and O 3 , indicated that both fossil fuel combustion and photochemical oxidation influenced the air concentrations of PAHs. According to the source apportionment by diagnostic ratios and PMF model, coal combustion and traffic emission were estimated to be the main sources of PAHs in Dalian, followed by petroleum release and biomass burning. It was worth noting that the contribution of coal combustion to the PAH burdens increased from 26% to 45% due to the emission from domestic heating in winter. This extra emission needs a continuous concern in the future. Graphical abstract Image 1 Highlights • Correlations of gaseous PAHs with six criteria air pollutants were estimated. • Coal combustion and traffic emission were the main sources of PAHs in Dalian. • Contribution of coal combustion to PAHs increased 19% in winter due to coal heating. [ABSTRACT FROM AUTHOR]

We investigated the concentrations, distributions, and sources of PAHs in the air and soils of Dalian, China, as well as their air-soil exchange trends. Total concentrations of PAHs in the air ranged from 6.37 to 124 ng/m3 with an average of 23.1 ± 26.6 ng/m3, while Σ 15 PAHs in the soils ranged from 42.8 to 28600 ng/g with an average of 2580 ± 5730 ng/g. Significant spatial distribution of PAHs was discovered in the soils with a clear urban-suburban-rural decreasing gradient, suggesting urban area is more contaminated by PAHs due to frequent and intensive human activities. However, high PAH concentrations were also discovered in the air from several rural sites, implying some PAH sources have shifted from urban to suburban or rural areas. Source apportionment indicated that major sources of PAHs in the urban and suburban soils were traffic emission/oil spill and coal combustion respectively, whereas major sources in the rural soils were diverse. Air-soil partitioning result suggested that 3-ring PAHs were mostly volatilized from soil, 6-ring PAHs were deposited into soil, while the trends of 4∼5-ring PAHs varied with sampling site. Fluoranthene, Pyrene, and Chrysene were mostly discovered to be volatilized in the urban and suburban areas, but equilibrium or deposited in the rural area, indicating a potential urban-to-rural transport of PAHs. The atmospheric transport and source shift of PAHs from urban to rural areas highlighted the importance of PAH source control on a regional scale. Image 1 • An obvious urban-to-rural decreasing gradient of PAHs was discovered in the soils. • High PAH levels in some rural air suggested an urban-to-rural shift of PAH source. • Traffic emission/oil spill is the major PAH source in the urban area of Dalian. • 4-ring PAHs were mainly volatilized in urban areas but equilibrium in rural areas. [ABSTRACT FROM AUTHOR]