On the nature and health impacts of BTEX in a populated middle eastern city: Tehran, Iran

This study describes a spatio-temporal characterization of concentrations of BTEX in ambient air of four hot spots (bus terminals) in the megacity of Tehran. Monte Carlo simulations were performed to evaluate cancer risk and non-cancer risk owing to BTEX exposure in three age groups (<6, 6 to <21 and 21 to <81 years). The average toluene to benzene ratios for the four intercity bus terminals were 2.63 (summer) and 2.88 (winter). Furthermore, the mean xylenes to benzene and ethylbenzene to benzene ratios in the two seasons for all stations ranged from 3.33 to 4.40 (summer) and 2.13�2.80 (winter), respectively. There was insignificant difference in BTEX levels between working and non-working days owing to the lack of change in vehicular traffic during the full week. Factors promoting BTEX formation in the study region were fuel evaporation, gas stations, diesel bus emissions, and a lack of hydroxyl radicals (radOH) for reacting with the target compounds. Calculations suggested that cancer risk for benzene and ethylbenzene in three age groups at the four bus terminals exceeded values recommended by U. S. EPA. In addition, the hazard quotient for BTEX in both seasons for different age groups ranged between 1.23 � 10 �5 and 3.58 � 10 �1 , values of which were lower than reference levels. Carcinogenic emissions such as with benzene and ethylbenzene discharged by bus terminals impact the growing population in the study region, which requires additional action to reduce health effects. © 2019 Turkish National Committee for Air Pollution Research and Contro

Priorities and interactions of Sustainable Development Goals (SDGs) with focus on wetlands

Wetlands are often vital physical and social components of a country's natural capital, as well as providers of ecosystem services to local and national communities. We performed a network analysis to prioritize Sustainable Development Goal (SDG) targets for sustainable development in iconic wetlands and wetlandscapes around the world. The analysis was based on the information and perceptions on 45 wetlandscapes worldwide by 49 wetland researchers of the GlobalWetland Ecohydrological Network (GWEN). We identified three 2030 Agenda targets of high priority across the wetlandscapes needed to achieve sustainable development: Target 6.3-'Improve water quality'; 2.4-'Sustainable food production'; and 12.2-'Sustainable management of resources'. Moreover, we found specific feedback mechanisms and synergies between SDG targets in the context of wetlands. The most consistent reinforcing interactions were the influence of Target 12.2 on 8.4-'Efficient resource consumption'; and that of Target 6.3 on 12.2. The wetlandscapes could be differentiated in four bundles of distinctive priority SDG-targets: 'Basic human needs', 'Sustainable tourism', 'Environmental impact in urban wetlands', and 'Improving and conserving environment'. In general, we find that the SDG groups, targets, and interactions stress that maintaining good water quality and a 'wise use' of wetlandscapes are vital to attaining sustainable development within these sensitive ecosystems. © 2019 by the authors

Optimization of Influencing Parameters on Phenanthrene Removal Efficiency in Soil Washing Process by Using Response Surface Methodology

Response surface methodology (RSM) under Box�Behnken design (BBD) was applied to evaluate the effect of the influencing parameters including surfactant concentration, liquid/soil ratio, Humic Acid concentration, and washing time on phenanthrene removal efficiency in soil washing process by using the nonionic surfactant Tween 80 and find an optimal operational conditions to achieve the highest removal efficiency. A polynomial quadratic model was used to correlate phenanthrene removal efficiency and four independent variables (R2 = 0.9719). Based on the obtained results the most influential parameter on phenanthrene removal efficiency was surfactant concentration with an impact value of 69.519. Liquid/soil ratio was also another factor that significantly influenced on removal efficiency with an impact value of 25.014. The interaction between surfactant concentration and liquid/soil ratio was also shown to have a positive significant effect on removal efficiency (pvalue = 0.0027). However, the other independent variables Humic Acid concentration and time were not significant in the ranges selected in this study. Based on the optimization results maximum removal efficiency of 70.692 ± 3.647 was achieved under the conditions of surfactant concentration 5000 mg L�1, liquid/soil ratio 30 v/w, HA concentration 9.88 mg L�1, and washing time 2 h, which was in good agreement with predicted value (66.643). © 2018 Taylor & Francis Group, LLC

Enhanced photocatalytic degradation of metronidazole by TiO2 decorated on magnetic reduced graphene oxide: Characterization, optimization and reaction mechanism studies

In this work, the TiO2 decorated magnetic reduced graphene oxide was fabricated by the hydrothermal method. The characterization of prepared composite was studied by XRD, FT-IR, SEM, EDX, BET, and TGA techniques. Both the magnetization of TiO2 by Fe3O4 nanoparticles and then its decorating on rGO surface were confirmed using characterization tests. The photocatalytic efficacy of the provided samples was defined via the degradation of metronidazole (MNZ) under visible light irradiation. The operational parameters' effect, including pH, catalyst dosage, initial MNZ concentration, rGO, and TiO2, was evaluated. The results indicated that the maximum degradation rate of MNZ (0.0092 min�1) was obtained for 0.75 g composite containing 4 rGO and 5 TiO2 at pH = 5 and MNZ concentration of 20 mg/L. MNZ and TOC were eliminated completely at optimum operational conditions within 120 and 250 min reaction times, respectively. The quenching test revealed that O2�- acted as dominant radical in the degradation process. © 2020 Elsevier B.V

Desorption kinetics and isotherms of phenanthrene from contaminated soil

Background: Prediction of polycyclic aromatic hydrocarbons (PAHs) desorption from soil to estimate available fraction regarding to initial concentration of the contaminant is of great important in soil pollution management, which has poorly been understood until now. In the present study estimation of fast desorption fraction which is considered as available fraction was conducted by evaluating desorption kinetics of phenanthrene (a three ring PAH) from artificially contaminated soils through the mathematical models. Methods: Desorption rate of phenanthrene (PHE) was investigated by using the nonionic surfactant Tween80 in a series of batch experiments. The effects of reaction time from 5 to 1440 min and initial PHE concentration in the range of 100-1600 mg/kg were studied. Results: Available fractions of the contaminant were achieved within the first hour of desorption process as the system reached to equilibrium conditions. Experimental data were examined by using kinetic models including pseudo-first-order, pseudo-second-order in four linearized forms, and fractional power. Among the models tested, experimental data were well described by pseudo-second-order model type (III) and (IV) and fractional power equation. Fast desorption rates, as Available fractions were determined 79%, 46%, 40%, 39%, and 35% for initial PHE concentrations of 100, 400, 800, 1200, and 1600 mg/kg respectively. Among the evaluated isotherm models, including Freundlich, Langmuir in four linearized forms, and Temkin, the equilibrium data were well fitted by the first one. Conclusion: Applying the nonionic surfactant Tween80 is a useful method to determine available fraction of the contaminant. This method will provide the management of contaminated sites by choosing a proper technique for remediation and predicting achievable treatment efficiency

Co-implanting of TiO2 and liquid-phase-delaminated g-C3N4 on multi-functional graphene nanobridges for enhancing photocatalytic degradation of acetaminophen

Herein, an efficient all-solid-state Z-type photocatalyst, TiO2/graphene/g-C3N4 (TGCN), was fabricated, characterized and utilized toward acetaminophen (ACM) degradation under a simulated solar light (SSL). The acid-treatment-assisted exfoliation process was used to break Van-der-Waals bonds between the bulk g-C3N4 layers and yield of ultrathin g-C3N4 nanosheets was fully explained. Also, the importance of using HCl and water in the process was examined. Structural, morphological and surface features of samples were thoroughly determined using XRD, Raman, TGA, FTIR, EDX, DRS, TEM, HRTEM, FESEM, BET, PL, EIS and photocurrent analyses. By considering different locations of graphene nanosheets in the TGCN, different charge transfer mechanisms were purposed and investigated employing Coulomb's law and trapping experiments. Constructing the efficient Z-type photocatalyst by introduction of graphene as shuttle electron mediator to TiO2 and g-C3N4 nanocomposite significantly enhanced the degradation performance and photo-activity. The adsorption edge of the TGCN nanocomposite was extended to the visible·light region by g-C3N4 nanosheets benefiting a more favorable band gap position. The characterization results clarified that graphene facilitates photo-induced electron transportation and separation as well as improving the specific surface area and promoting the ACM adsorption capacity. Then, the most possible indirect Z-type charge separation mechanism for TGCN/SSL system was successfully confirmed by findings. Benefiting from the excellent synergetic effect of the catalyst individual systems, the ACM (50 mg/L) could reach up to complete degradation under SSL irradiation with the 0.6 g/L of TGCN (60:10:30) at pH = 9.0 within 120 min reaction. In the end, a tentative pathway for ACM decomposition was suggested. © 2021 Elsevier B.V

Reuse of polycyclic aromatic hydrocarbons (PAHs) contaminated soil washing effluent by bioaugmentation/biostimulation process

The reuse feasibility of the bioremediated effluent of the combination of sequential soil washing followed by biological treatment for removal of phenanthrene (PHE) from contaminated soils was investigated for several soil washing. In the first stage a removal efficiency of 74.4 ± 3.5 was obtained under the optimum conditions of: surfactant (Tween 80) concentration of 5000 mg/L, liquid/soil ratio of 30 v/w, humic acid concentration of 2.31 mg/L (6.93), and washing time of 2 h. In the second stage complete biodegradation of PHE from soil washing effluent was achieved by inoculating enriched bacterial consortium (OD600nm = 1) within 7 days. Reuse possibility of biologically treated solution for the next cycles of soil washing process was conducted by adjusting the surfactant concentration. The findings displayed that reusability of the biologically recycled solution was maintained up to 7th cycle, reaching a removal efficiency of >99 and >97 in artificial and real contaminated soils respectively, indicating the effectiveness of reused surfactant solution. © 2016 Elsevier B.V

Sono-photocatalytic degradation of tetracycline and pharmaceutical wastewater using WO3/CNT heterojunction nanocomposite under US and visible light irradiations: A novel hybrid system

In this paper, in-situ fabrication of tungsten oxide (WO3) on carbon nano-tube (CNT) was performed via sol-gel/hydrothermal method to prepare WO3/CNT nanocomposites and then coupled with visible light and ultrasound (US) irradiations for sono-photocatalytic removal of tetracycline (TTC) and pharmaceutical wastewater treatment. The as-prepared catalysts were characterized by FT-IR, XRD, TEM, UV-VIS DRS, FESEM, EDS, TGA, BET, BJH, EIS, and EDX techniques. The characterization tests, indicated successful incorporation of CTNs into the WO3 framework and efficient reduction of charge carries recombination rate after modifying with CNT. The investigation of experimental parameters verified that 60 mg/L TTC could be perfectly degraded at optimum operational parameters (WO3/CNT: 0.7 g/L, pH: 9.0, US power: 250 W/m2, and light intensity: 120 W/m2 over 60 min treatment. Trapping experiments results verified that HOrad radicals and h+ were the main oxidative species in degradation of TTC. The as-prepared photocatalysts could be reused after six successive cycles with an approximately 8.8 % reduction in removal efficiency. Investigation of the effect of real pharmaceutical wastewater revealed that this system is able to eliminate 83.7 and 90.6 % of TOC and COD, respectively after 220 min of reaction time. Some compounds with lower toxic impact and molecular weight, compared to raw pharmaceutical wastewater, were detected after treatment by sono-photocatalysis process. The biodegradability of real pharmaceutical wastewater was improved significantly after treatment by WO3/CNT sono-photocatalysis. © 2020 Elsevier B.V