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This study investigated PM2.5-PAHs associations collected in Beijing, Jinan, and Shanghai in Eastern China. The results indicated that PM2.5 concentrations in Beijing, Jinan, and Shanghai were 125.7 μg m−3 (18.6–355.5 μg m−3), 115.9 μg m−3 (44.2–345.4 μg m−3), and 85.1 μg m−3 (24.3–232.8 μg m−3), respectively. The PAH concentrations in terms of PM2.5 in Beijing, Jinan, and Shanghai ranged from 23.2 to 819.8 ng m−3, 25.7 to 727.1 ng m−3, and 8.5 to 133.9 ng m−3, respectively. PAH concentrations were found to be positively correlated with PM2.5 concentration in Beijing and Shanghai. The compositions of PAHs in PM2.5 in Beijing and Jinan were almost the same: 11% low ring, 80–82% middle ring, and 7–9% high ring. However, Shanghai had a different composition. Source apportionment indicated that the incomplete combustion of coal and diesel and gasoline emissions were the main sources of PAHs in PM2.5 in all three cities, whereas Shanghai had a greater contribution from liquid fossil fuels. The values for the health risk assessment estimated by the benzo[a]pyrene equivalent concentration in Beijing and Jinan were 2.39 × 10−6 and 2.57 × 10−6, respectively, thus both exceeding the 1 × 10−6 limit (USEPA) considered likely to pose an inhalation cancer risk to people. Shanghai, however, had a risk estimate of 5.05 × 10−7, which is still in a safe range. This study is the first to simultaneously monitor the PAHs in PM2.5 in three cities in Eastern China and may point to a long-range transportation of PM2.5-PAHs from Beijing to Jinan and partially to Shanghai. [ABSTRACT FROM AUTHOR]

Invasive Spartina alterniflora ( S. alterniflora ) has significant impacts on sediment biogeochemical cycling in the tidal wetlands of estuaries and coasts. However, the impact of exotic Spartina alterniflora invasion on greenhouse gases (GHGs) production dynamics in sediments remain limited. Here, we investigated the dynamics of sediment physicochemical properties, GHGs production rates, and microbial gene abundances in a native Cyperus malacensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year) in the Minjiang River Estuary, China. The methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O) production rates varied both spatially and seasonally, while microbial gene abundances (bacterial and fungal gene abundances) and organic matter (TOC and TN) only varied spatially. GHGs production rates were also characterized by higher values in surface sediment (0-10 cm) compared to subsurface sediment (10-20 cm) and by seasonal variations with higher values in summer than in winter. S. alterniflora invasion can significantly increase CH 4 and CO 2 production rates, organic matter, and microbial gene abundances ( p < 0.05). Temperature, organic matter and microbial gene abundances were the most dominating factor controlling the spatio-temporal variations of CH 4 and CO 2 production rates. Overall, our findings highlighted the significant role of S. alterniflora invasion in regulating GHGs production rates in coastal wetland sediments and provided fundamental data for estimating GHGs emissions and carbon sequestration in the complex tidal wetlands., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Jiang, Shao, Huang, Du, Wen, Tang, Xu, Gao, Lin and Sun.)

Dissolved inorganic nitrogen (DIN) is very high in the Pearl River Estuary (PRE) and nitrate (NO x - ) removal processes such as denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) are important for determining export of DIN to coastal waters. However, fluxes of NO x - removal and influencing factors in the PRE are still unclear. We conducted 4 cruises at 11 sites in the PRE to investigate potential NO x - removal rates, their contributions, and corresponding gene abundances, and controlling factors in surface sediments (0-5 cm). The results showed that the potential rates of denitrification, anammox, and DNRA as well as their contributions varied spatially and seasonally. Denitrification (1.98 ± 1.7 μg N g -1 d -1 ) was the major NO x - removal processes (68.43 ± 14.61%) while DNRA (0.45 ± 0.28 μg N g -1 d -1 ) contributed 22.61 ± 14.89% in NO x - removal. The NO x - removal processes and corresponding gene abundances were correlated with the chlorophyll concentrations in both overlying water and sediment, indicating that marine-produced organic matter was the major driver for benthic NO x - removal processes. In addition, water column turbidity had important effects on primary production, which affects benthic N processes. Our study provides evidences for that the turbidity-regulated primary production in overlying water is the primary driver for benthic NO x - removal processes. The contribution of sediment NO x - removal fluxes to water column NO x - concentration was low in the upper estuary and increased in the lower estuary where marine produced chlorophyll a was higher. However, daily fluxes of NO x - removal were estimated to account for only 0.18-7.22% (mean 1.85 ± 1.62%) of NO x - in the whole overlying water column. This suggests that most riverine NO x - was exported out into the adjacent coastal waters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)