Spatiotemporal variation of atmospheric nitrated polycyclic aromatic hydrocarbons in semi-arid and petrochemical industrialized Lanzhou City, Northwest China

Profiles, exposure assessment and expanded screening of PAHs and their derivatives in one petroleum refinery facility of China

This study investigated environmental distribution and human exposure of polycyclic aromatic hydrocarbons (PAHs) and their derivatives in one Chinese petroleum refinery facility. It was found that, following with high concentrations of 16 EPA PAHs (∑Parent-PAHs) in smelting subarea of studied petroleum refinery facility, total derivatives of PAHs [named as XPAHs, including nitro PAHs (NPAHs), chlorinated PAHs (Cl-PAHs), and brominated PAHs (Br-PAHs)] in gas (mean= 1.57 × 104 ng/m3), total suspended particulate (TSP) (mean= 4.33 × 103 ng/m3) and soil (mean= 4.37 × 103 ng/g) in this subarea had 1.76-6.19 times higher levels than those from other subareas of this facility, surrounding residential areas and reference areas, indicating that petroleum refining processes would lead apparent derivation of PAHs. Especially, compared with those in residential and reference areas, gas samples in the petrochemical areas had higher ∑NPAH/∑PAHs (mean=2.18), but lower ∑Cl-PAH/∑PAHs (mean=1.43 × 10-1) and ∑Br-PAH/∑PAHs ratios (mean=7.49 × 10-2), indicating the richer nitrification of PAHs than chlorination during petrochemical process. The occupational exposure to PAHs and XPAHs in this petroleum refinery facility were 24-343 times higher than non-occupational exposure, and the ILCR (1.04 × 10-4) for petrochemical workers was considered to be potential high risk. Furthermore, one expanded high-resolution screening through GC Orbitrap/MS was performed for soils from petrochemical area, and another 35 PAHs were found, including alkyl-PAHs, phenyl-PAHs and other species, indicating that profiles and risks of PAHs analogs in petrochemical areas deserve further expanded investigation.

Response of trace elements in urban deposition to emissions in a northwestern river valley type city: 2010-2021

Anthropogenic activities release significant quantities of trace elements into the atmosphere, which can infiltrate ecosystems through both wet and dry deposition, resulting in ecological harm. Although the current study focuses on the emission inventory and deposition of trace elements, their complex interactions remain insufficiently explored. In this study, we employ emission inventories and deposition data for eight TEs (Cr, Mn, Ni, Cu, Zn, As, Cd, Pb) in Lanzhou City to unveil the relationship between these two aspects. Emissions in Lanzhou can be roughly divided into two periods centered around 2017. Preceding 2017, industrial production constituted the primary source of TEs emissions except for As; coal combustion was the primary contributor to Cr, Mn, and As emissions; waste incineration played a significant role in As, Zn, and Cd emissions; biomass combustion influenced Cr and Cd emissions; and transportation sources were the predominant contributors to Pb and Cu emissions. With the establishment of waste-to-energy plants and the implementation of ultra-low emission retrofits, emissions from these sources decreased substantially after 2017. Consequently, emissions from industrial production emerged as the main source of TEs. The deposition concentrations of Cr, Mn, Ni, Cu, and Pb followed a similar trend to the emissions. However, Cd and As exhibited lower emissions and a less pronounced response relationship. Moreover, Zn concentrations fluctuated within a narrow range and showed a weaker response to emissions. The consistent changes in emissions and TEs deposition concentrations signify a shift in deposition pollution in Lanzhou city from Coal-fired pollution to that driven by transportation and industrial activities. Within this transition, the industrial production process offers significant potential for emission reduction. This insight provides a crucial foundation for managing TEs pollution and implementing strategies to prevent ecological risks.

PM-bound polycyclic aromatic compounds (PACs) in two large-scale petrochemical bases in South China: Spatial variations, sources, and risk assessment

Polycyclic aromatic compounds (PACs) are potential pollutants emitted from the petrochemical industry, whereas their occurrence and sources in petrochemical regions are still poorly known. The present study revealed the spatial variations, compositional profiles, sources and contributions, and health risks of PM-bound PACs in two large-scale petrochemical bases (GDPB and HNPB) in South China. The concentrations of parent polycyclic aromatic hydrocarbons (PAHs) were 7.14 ± 3.16 ng/m³ for ∑₁₈PAHs and 0.608 ± 0.294 ng/m³ for the PAHs with molecular weight of 302 amu (MW302 PAHs) in the GDPB base and 2.55 ± 1.26 ng/m³ and 0.189 ± 0.088 ng/m³ in the HNPB base. Oxygenated PAHs (OPAHs) showed comparable concentrations to the parent PAHs in both the bases and nitrated PAHs (NPAHs) had the lowest mean levels (260 pg/m³ and 59.4 pg/m³ in the two regions). Coronene, 2,8-dinitrodibenzothiophene, and dibenzo[a,e]fluoranthene showed remarkably higher contributions to the PAC and can be PAC markers of the petrochemical industry source. Five sources of PACs were identified respectively in both petrochemical bases by the positive matrix factorization (PMF) model. The vehicle (and ship) traffic exhaust was the primary source of PACs (contributed 33% to the ∑PACs), and the sources related to the coking of coal and heavy petroleum and refinery exhaust were identified in both bases, with contributions of 10-20%. PACs in GDPB also contributed from secondary atmospheric reactions (17.3%) and the usage of sulfur-containing fuels (20.9%), while the aromatics industry made a significant contribution (20.1%) to the PACs in the HNPB region. The cumulative incremental lifetime cancer risks (ILCRs) induced by inhalation of PM-bound PACs in both petrochemical bases were low (10^-8-10^-6). For the sources related to the petrochemical industry, coking activities and the aromatic industry were the significant contributors to the ∑ILCRs in GDPB and HNPB, respectively. This research has implications for further source-targeted control and health risk reduction of PACs in petrochemical regions.

Spatial and seasonal variation and sources of deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) in Shanghai

Spatial and temporal variations of polycyclic aromatic hydrocarbons (PAHs) deposition fluxes and sources may significantly facilitate risk evaluation and pollution control of super megacity in China. A study on PAHs of wet and dry deposition in Shanghai was conducted from January to December of 2019. Seventeen sampling sites located in four functional areas were set, including the Baoshan iron and steel industry area (BS), Jinshan petrochemical industry area (JS), city center (CC), and Chongming agricultural area (CM). A total of 15 PAHs were determined by gas chromatography-mass spectrometry (GC-MS, Agilent 7890A/5975C). PAHs atmospheric deposition flux in winter was highest (3.12 ± 1.98 μg/(m²·day), mostly attributed to local emissions accumulation under adverse meteorological diffusion conditions, as well as pollutants transport from northern China during heating season. PAHs deposition fluxes in industrial area (BS and JS) were 3.75 ± 4.08 μg/(m²·day) and 3.18 ± 3.62 μg/(m²·day) respectively, which were greater than those in CC and CM, accounting for 1.91 ± 1.06 μg/(m²·day) and 1.41 ± 0.61 μg/(m²·day) respectively. Proportional composition and isomer ratios of PAHs indicated that the PAHs deposition in winter and spring samples were more homogeneous, whereas those of summer and autumn seemed to be more variable and dispersed. Positive matrix factorization model were employed to identify the potential sources of PAHs in specific functional areas. A dominance of contribution was attributed to coal combustion (46%) at BS, petroleum volatilization (48%) at JS, biomass burning (55%) at CM, and vehicle emission (49%) at CC. This study highlighted that local urbanization and industrialization have a significant contribution to PAHs deposition to specific functional regions in Shanghai.

Spatial and temporal variation, source identification, and toxicity evaluation of brominated/chlorinated/nitrated/oxygenated-PAHs at a heavily industrialized area in eastern China

Some derivatives of polycyclic aromatic hydrocarbons (PAHs) such as chlorinated and brominated PAHs (Cl/BrPAHs), nitrated and oxygenated PAHs (N/OPAHs) have attracted significant concern due to their high toxicity. Knowledge of the profiles, formation mechanisms, and potential sources of these toxic chemicals near the industrial complexes is essential for their pollution control and management. In this study, we monitored Cl/BrPAHs, N/OPAHs, and PAHs at 24 sampling sites near a heavily industrialized area (steel, chemical, and rubber plants) using passive air samplers during the heating period (7 December 2019 to 15 April 2020) and the non-heating period (2 June 2020 to 4 October 2020). The total average concentrations of 16 BrPAHs, 8 ClPAHs, 17 NPAHs, 6 OPAHs, and 18 PAHs during both sampling periods were 471 pg/m³, 229 pg/m³, 312 pg/m³, 2120 pg/m³, and 63.1 ng/m³, respectively. Except for NPAHs, BrPAHs, ClPAHs, OPAHs, and PAHs all showed higher levels during the heating period. The spatial distributions of Cl/BrPAHs, N/OPAHs, and PAHs exhibited a similar pattern, with the highest concentrations detected in the vicinity of the steel industry. Congener profiles of PAH derivatives indicated that mono-substituted low molecular weight compounds (2-3 rings) were dominant. The major formation mechanisms of halogenated PAHs were discussed by correlation analysis and relative Gibbs free energies, and direct bromination of parent PAHs could be the major formation mechanism of BrPAHs in this study. Diagnostic ratios showed that NPAHs were mainly derived from primary emissions, but the contribution of secondary formation was increased at heavily contaminated sites. The positive matrix factorization model extracted four Cl/BrPAHs, three N/OPAHs, and four PAHs factors, and the result showed that PAHs and their derivatives mainly derived from industrial and combustion sources, photochemical reactions, vehicle emissions, and crude oil volatilization, etc.

Passive air sampling for semi-volatile organic chemicals

During passive air sampling, the amount of a chemical taken up in a sorbent from the air without the help of a pump is quantified and converted into an air concentration. In an equilibrium sampler, this conversion requires a thermodynamic parameter, the equilibrium sorption coefficient between gas-phase and sorbent. In a kinetic sampler, a time-averaged air concentration is obtained using a sampling rate, which is a kinetic parameter. Design requirements for kinetic and equilibrium sampling conflict with each other. The volatility of semi-volatile organic compounds (SVOCs) varies over five orders of magnitude, which implies that passive air samplers are inevitably kinetic samplers for less volatile SVOCs and equilibrium samplers for more volatile SVOCs. Therefore, most currently used passive sampler designs for SVOCs are a compromise that requires the consideration of both a thermodynamic and a kinetic parameter. Their quantitative interpretation depends on assumptions that are rarely fulfilled, and on input parameters, that are often only known with high uncertainty. Kinetic passive air sampling for SVOCs is also challenging because their typically very low atmospheric concentrations necessitate relatively high sampling rates that can only be achieved without the use of diffusive barriers. This in turn renders sampling rates dependent on wind conditions and therefore highly variable. Despite the overall high uncertainty arising from these challenges, passive air samplers for SVOCs have valuable roles to play in recording (i) spatial concentration variability at scales ranging from a few centimeters to tens of thousands of kilometers, (ii) long-term trends, (iii) air contamination in remote and inaccessible locations and (iv) indoor inhalation exposure. Going forward, thermal desorption of sorbents may lower the detection limits for some SVOCs to an extent that the use of diffusive barriers in the kinetic sampling of SVOCs becomes feasible, which is a prerequisite to decreasing the uncertainty of sampling rates. If the thermally stable sorbent additionally has a high sorptive capacity, it may be possible to design true kinetic samplers for most SVOCs. In the meantime, the passive air sampling community would benefit from being more transparent by rigorously quantifying and explicitly reporting uncertainty.