Mechanistic insights into Fe(II)-citric acid complex catalyzed CaO2 Fenton-like process for enhanced benzo[a]pyrene removal from black-odor sediment at circumneutral pH.

Polycyclic aromatic hydrocarbons (PAHs) are found ubiquitously in contaminated aquatic sediments. They are difficult to degrade, particularly the high-molecular-weight PAHs (e.g., benzo[a]pyrene, BaP). In this study, CaO2 assisted with ferrous ion (Fe(II))-citric acid (CA) was applied for the first time in BaP degradation in aquatic sediment. Among the treatment processes we studied, CaO2/Fe(Ⅱ)/CA could effectively degrade BaP at circumneutral pH (7.0 ± 0.3), reaching a maximum of nearly 80% under optimal conditions (0.84 mM CaO2, 0.21 mM Fe(Ⅱ), and 0.35 mM CA in per gram of dry sediment). Contrary to some external environmental factors such as temperature, common metal ions, and natural organic matters, a certain amount of moisture content and inorganic anions (Cl-, SO42-) exhibited a positive effect on BaP degradation, which can probably be contributed to the improved mass transfer rate in the non-homogeneous sediment-water mixture and a higher level of free radicals. The degradation kinetic dominated by hydroxyl radicals included three main stages contribution ∼29.4%, ∼43.1%, and ∼2.4% to BaP degradation, respectively. Based on the theoretical calculations of density functional theory, a pathway for BaP degradation was proposed. For the treatment of actual contaminated sediment, the CaO2/Fe(II)/CA process could realize the elimination of black-odor and effective removal of PAHs from the sediment, as well as negligible ecotoxicity on benthic organisms. This study provides a reference and guidance for the use of CaO2 based Fenton-like systems in treating PAH-contaminated black-odor river sediments.

The Association of Morphological Differences of Middle Cerebral Artery Bifurcation and Aneurysm Formation: A Systematic Review and Meta-Analysis.

OBJECTIVE: We explored the relationships between morphological parameters of middle cerebral artery (MCA) bifurcations based on imaging and the development of middle cerebral aneurysms. Artery bifurcations can form disordered hemodynamics which can promote the development of aneurysms, whereas the hemodynamic environment at the bifurcation tip is highly reliant on the bifurcation's geometry. METHODS: We searched 3 electronic databases for all relevant, publicly available publications as of March 18, 2022. Through the screening of abstracts and full texts, a meta-analysis was performed to compare the daughter-to-daughter angle, the inclination angle (γ), and the parent vessel diameter of MCA bifurcations between patients in MCA aneurysm and non-aneurysm controls. RESULTS: Ten articles describing 1012 patients with MCA aneurysms and 1106 control individuals without aneurysms were included in the analysis. The aneurysm group showed a larger daughter-to-daughter branch angle at MCA bifurcations than the non-aneurysm group (weighted mean difference [WMD] = 42.00; 95% confidence interval [CI], 33.77 to 50.23; P < 0.00001). The daughter-to-daughter angle was also larger in the MCA aneurysm group with than without an aneurysm side branch (WMD = 37.03; 95% CI, 26.57 to 47.50; P < 0.00001), and in the MCA aneurysm group than in the non-aneurysm control group (WMD = 41.87; 95% CI, 29.19 to 54.54; P < 0.00001). The aneurysm group had a larger inclination angle than the control group (WMD = 28.73; 95% CI, 18.78 to 38.69; P < 0.00001). In patients with a MCA aneurysm, the parent vessel of the branch with the MCA aneurysm tended to be smaller in diameter than the contralateral branch without the aneurysm (WMD = -0.12; 95% CI, -0.24 to 0.00; P = 0.05). CONCLUSIONS: A larger daughter-to-daughter angle and larger inclination angle at MCA bifurcations are closely related to MCA bifurcation aneurysms. The parent vessel diameter is negatively related to MCA bifurcation aneurysms.