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As a set of persistent organic pollutants (POPs) that cause serious harm to human and animal health, polycyclic aromatic hydrocarbons (PAHs) degradation has attracted attentions of many scholars. Ozonation is one of the promising techniques for removing PAHs from various aqueous solutions because of its molecular structures, rapid reaction with ozone (O3), and oxidation by-products of PAHs produced during ozonation are more biodegradable than initial PAHs. However, its application is constrained by the high cost of ozone production, and organic matter in water is only partially oxidized. In recent years, to improve the efficiency of the ozonation process and optimize economic efficiency, several methods of O3-based advanced oxidation processes (AOPs) (i.e. O3/UV, O3/H2O2, O3/H2O2/UV, O3/Fenton, O3/Catalyst) have been studied. These AOPs generate more HO• than molecular ozone. This review summarized recent developments relating to the degradation of PAHs via O3-based AOPs and their exciting mechanisms. Compared different processes characteristics in terms, such as radical species, operational conditions, by-products and their toxicity, and cost. We considered that O3/photocatalyst seems to be a better choice for PAHs degradation. Finally, the challenges and future trends of PAH degradation have prospected. [ABSTRACT FROM AUTHOR]

To meet the strict requirements of reducing sulfur emissions, an increasing number of commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during the cleaning process is discharged back to the marine environment. We investigated the effects of closed-loop scrubber (natrium-alkali method) wash water on three trophic species. Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae were exposed to 0.63–6.25, 0.63–10, and 1.25–20% concentrations of wash water, respectively. The 50% effective concentration in 96 h (EC50-96 h) for D. salina was 2.48%, and the corresponding total polycyclic aromatic hydrocarbons (PAHs) and heavy metals were 22.81 and 23.67 μg L−1. The 50% lethal concentration in 7 d (LC50-7 d) values for M. bahia and M. chulae were 3.57% and 20.50%, respectively. The lowest observed effect concentration (LOEC) values for M. bahia and M. chulae were 1.25% and 2.5%, respectively, and the corresponding total PAHs and heavy metals were 11.50 and 11.93 and 22.99 and 23.86 μg L−1. M. bahia 's body weight was negatively correlated with the amount of wash water. Low concentrations of wash water (0–5%) had no significant effect on the reproduction of M. bahia. Although concentrations of 16 PAHs and 8 heavy metals are known, different compounds might react with each other and form more unknown toxic substances, and the measured toxicity comes from synergistic effects between various pollutants. Therefore, future work is needed to clarify other more toxic contaminants in wash water. We highly recommend that wash water be treated before being discharged to the marine environment. [ABSTRACT FROM AUTHOR]

Ship's Ballast Water Convention has officially entered into force in China. Assessing the potential risk of chemical by-products produced from treated ballast water is a new concern of marine environment safety. In this study, calculation methods for safety concentrations of 41 chemical by-products in treated ballast water was investigated based on risk assessment of ballast water proposed by International Marine Organization. The results indicated that the lowest safety concentrations were respectively dibromoacetonitrile (0.227 µg/L), monochloroacetic acid (2.166 µg/L), sodium hypochlorite (3.09 µg/L), bromochloroacetonitrile (3.58 µg/L), and monochloroacetonitrile (3.64 µg/L), whereas the highest value was dibromo-methane (114 000 µg/L). Deviation of safety concentrations might be due to lack of ecotoxicity data and different input values used in harbor model. The research results can not only provide basic data for the implementation of Ship' S Ballast Water Convention and the establishment of standards for chemical by-products in ballast water, but also provide methods for environmental assessment in related fields. [ABSTRACT FROM AUTHOR]

To solve the heteroscedastic problem in linear regression, many different heteroskedasticity-consistent covariance matrix estimators have been proposed, including HC0 estimator and its variants, such as HC1, HC2, HC3, HC4, HC5 and HC4m. Each variant of the HC0 estimator aims at correcting the tendency of underestimating the true variances. In this paper, a new variant of HC0 estimator, HC5m, which is a combination of HC5 and HC4m, is proposed. Both the numerical analysis and the empirical analysis show that the quasi-tinference based on HC5m is typically more reliable than inferences based on other covariance matrix estimators, regardless of the existence of high leverage points. [ABSTRACT FROM PUBLISHER]

Highlights: [•] We investigated the UV/TiO2 process for ballast water treatment. [•] UV/TiO2 treatment had the potential to inhibit plankton regrowth. [•] The advantages of UV/TiO2 at low UV dose (i.e., 75%) were much greater. [•] The concentrations of disinfection by-products formed during UV/TiO2 treatment were very low. [Copyright &y& Elsevier]

So far there is not an effective method to prevent the rapid spread of harmful microorganisms in air space or on the surface of objects. In this paper, a physical method based on strong electric-field discharge was used to produce hydroxyl radicals (\cdot\OH) for biological decontamination and sterilization in air space. Results show that cells of Staphylococcus aureus, Escherichia coli, and Yeast were rapidly killed by the \cdot\OH fogdrops with a concentration of 0.6 mg/L and spray density of 22 \mu\L/m^2 within 4 s. Cell morphological changes were also observed through the microscope. Most of the cells were disrupted and lysed into small debris when being exposed to a killing dosage of \cdot\OH radicals. [ABSTRACT FROM AUTHOR]

Background: Phenol and its derivatives are important intermediates in the chemical industry, especially the pharmaceutical and electronic industries. The synthesis of phenols has attracted the attention of scientists due to their importance. Dehydrogenation of cyclohexanones is one of the promising aromatization strategies for phenols manufacture because the raw materials are low cost and stable. In recent years, some efficient and green methods with the use of H 2 , O 2 and air, alkene, H 2 and O 2 -free are described., Objective: This mini-review will summarize some recent developments relating to the dehydrogenation of cyclohexanones to phenols, along with their interesting mechanism aspects. The challenges and future trends of the transformation will be prospected., Conclusion: The synthesis of phenols from the dehydrogenation of cyclohexanones has recently attracted much attention. Some synthetic methods have been established, and interesting mechanisms have been proposed in some cases. Lots of catalysts were developed for the transformation to afford the corresponding product. Although the present methods still have drawbacks and limitations, it is supposed that many novel methods would probably be developed in the near future., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)