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Antibiotic pollution of water resources is a global problem, and the development of new treatments for destroying antibiotics in water is a priority research. We successfully manufactured recyclable magnetic Fe3O4/g-C3N4 through the electrostatic self-assembly method. Selecting tetracycline (TC) as the target pollutant, using Fe3O4/g-C3N4 and H2O2 developed a heterogeneous optical Fenton system to remove TC under visible light. Fe3O4/g-C3N4 was systematically characterized by SEM, TEM, XRD, FTIR, XPS, DRS, and electrochemical methods. The removal efficiency of 7% Fe3O4/g-C3N4 at pH = 3, H2O2 = 5 mM, and catalyst dosage of 1.0 g/L can reach 99.8%. After magnetic separation, the Fe3O4/g-C3N4 photocatalyst can be recycled five times with minimal efficiency loss. The excellent degradation performance of the prepared catalyst may be attributed to the proper coupling interface between Fe3O4 and g-C3N4 which promotes the separation and transfer of photogenerated electrons. Photogenerated electrons can also accelerate the conversion of Fe3+ to Fe2+, thereby producing more ˙OH. The new Fe3O4/g-C3N4 can be used as a raw material for advanced oxidation of water contaminated by refractory antibiotics.

This study investigated the AQI (air quality index) and atmospheric pollutants including PM2.5, PM10, CO, SO2, NO2 and O3 in Chongqing, Luzhou and Chengdu from 2017 to 2019. In addition, the impacts of the COVID-19 event on the air quality in the three cities in 2020 were compared and discussed. For the combined AQIs for the three cities, in spring, the daily AQIs ranged between 25 and 182 and averaged 72.1. In summer, the daily AQIs ranged between 24 and 206 and averaged 77.5. In autumn, the daily AQIs ranged between 22 and 170 and averaged 61.1, and in winter, the daily AQIs ranged between 28 and 375 and averaged 99.6. The distributions of the six AQI classes in spring were 3%, 94%, 3%, 0%, 0%, and 0%; in summer, they were 11%, 74%, 15%, 0%, 0% and 0%; in autumn, they were 29%, 70%, 1%, 0%, 0%, and 0%, and in winter, they were 1%, 52%, 44%, 3%, 0%, and 0%, respectively. The average AQIs, in order, were Chengdu (85.4) > Chongqing (73.8) > Luzhou (73.2). Both the highest AQIs and PM2.5 (as the major indicatory air pollutant) occurred mainly in the low temperature season (January, December, and February), while O3 was the main air pollutant in June and August when the weather was hot. In February 2020, during the epidemic prevention and control actions taken in response to COVID-19 for the three cities, the combined AQIs for the top five days with the highest AQIs in February 2020 was 79.4, which was 23.6% lower than that from 2017–2019 (AQI = 100.7), and the average concentrations of PM2.5, PM10, SO2, CO, and NO2 were 89.4 µg m–3, 106 µg m–3, 2.31 ppb, 0.72 ppm, and 12.3 ppb, respectively, and were 17.9%, 30.8%, 83.8%, 19.8%, and 62.1%, lower than those in February 2017–2019. However, the average O3 concentration (31.8 ppb) in February 2020 rather than decreasing, increased by 6.2%. This is because a lower NO2 concentration hindered the NO + O3 reaction and led to increase O3 concentration in the ambient air.

Both the air quality index (AQI) and indicatory air pollutants of Anqing, Hefei, and Suzhou near central China from 2017 to 2019, and the impact of COVID-19 epidemic prevention and control actions on air quality were investigated. The combined data for the three cities from 2017 to 2019 indicated that the lowest AQI (averaged 78.1) occurred in the summer season, for which the AQI proportions for classes I, II, III, IV, V, and VI were 25.6%, 49.9%, 21.9%, 2.7%, 0%, and 0%, respectively. The highest (AQI average of 112.6) was in winter, for which the proportions were 7.4%, 39.5%, 33.3%, 12.5%, 7.2%, and 0.1%, respectively. PM2.5, PM10, and NO2 in order were the most important indicatory air pollutants for AQI classes IV, V, and VI, which all prevailed in winter and spring, while O3 was the indicatory air pollutant that occurred most in summer. The COVID-19 event, which triggered global attention, broke out at the end of 2019. This study also investigated and compared the air quality levels in the three cities from January to March 2017–2019 with those in 2020. The results showed that during February 2020, in the three cities, the average ambient air concentrations of PM2.5, PM10, SO2, CO, and NO2 were 41.9 µg m–3, 50.1 µg m–3, 2.18 ppb, 0.48 ppm, and 8.97 ppb, and were 46.5%, 48.9%, 52.5%, 36.2%, and 52.8%, respectively, lower than those in the same month in 2017–2019, respectively. However, the O3 average concentration (80.6 ppb) did not show significant fluctuations and even slightly increased by 3.6%. This is because a lower concentration of NO2 resulted in constraints on the reaction of NO + O3, so the O3 level could not be effectively further reduced. In addition, this study also analyzed and compared the five highest daily AQIs from February 2017–2019 with those of 2020 for the three cities. The mean AQI for the 5 days with the highest daily AQI (averaged 122.6) in February 2020 was 45.1% lower than that for February 2017–2019 (averaging 223.2), and the indicatory air pollutant was always PM2.5, which decreased by 46.7% (from 173.6 to 92.6 µg m–3). It is clear that during the COVID-19 epidemic prevention and control action periods, the air quality near central China improved significantly.

In early 2020, the COVID-19 epidemic spread globally. This study investigated the air quality of three cities in Hubei Province, Wuhan, Jingmen, and Enshi, central China, from January to March 2017–2020 to analyze the impact of the epidemic prevention and control actions on air quality. The results indicated that in the three cities, during February 2020, when the epidemic prevention and control actions were taken, the average concentrations of atmospheric PM2.5, PM10, SO2, CO, and NO2 in the three cities were 46.1 µg m–3, 50.8 µg m–3, 2.56 ppb, 0.60 ppm, and 6.70 ppb, and were 30.1%, 40.5%, 33.4%, 27.9%, and 61.4% lower than the levels in February 2017–2019, respectively. However, the average O3 concentration (23.1, 32.4, and 40.2 ppb) in 2020 did not show a significant decrease, and even increased by 12.7%, 14.3%, and 11.6% in January, February, and March, respectively. This is because a lower concentration of NO2 resulted in constraints on the NO + O3 reaction, and the O3 could not be effectively further depleted. In addition, the average air quality index (AQI) for the three cities in January, February, and March 2020 were 32.2%, 27.7%, and 14.9% lower than the levels in 2017–2019, respectively. Based on the AQIs for the three cities, the combined proportions of Class I and Class Ⅱ in January, February, and March 2020 increased by 27.9%, 24.8%, and 4.3%, respectively, while the combined proportion of AQI Classes III, IV, V, and VI was reduced from 34.8% to 15.8%. In addition, in the first three months of 2020, the indicatory air pollutants in the three cities for the AQIs were predominant in the following order: PM2.5 (72.0%), O3 (16.4%), PM10 (8.3%), NO2 (2.9%), and CO (0.4%). This study provides useful information for establishing a scientific air pollution control strategy and is a valuable reference for future research on improving urban air quality.

Retarding the fuel injection timing is an effective strategy for controlling NOx emissions from diesel engines. However, the influence of retarding the fuel injection timing on polycyclic aromatic hydrocarbon (PAH) and persistent organic pollutant (POP) emissions has not yet been investigated. In this study, the diesel engine was tested using four of the existing thirteen European steady state cycle (ESC) modes. The fuel injection timing was retarded from –8° to –6° and the diesel exhaust gas samples were analyzed for PAH and POP emissions. The NOx emission factor reduced by ~25% when the fuel injection timing was retarded. However, the strategy had a negative effect on combustion efficiency. The carbon monoxide (CO) and particulate matter (PM) emissions were 1.4 and 1.2 times higher for the –6° scenario, respectively. The emission factors of all the toxic organic pollutants increased drastically when the fuel injection timing was retarded. For instance, the emission factors of PAH and polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) for the –6° scenario, based on BaPeq and WHO-TEQ, were 22 and 10 times higher than for the –8° scenario. The retardation had more influence on these pollutants in the particle-phase than in gas-phase. The resultant negative impact on combustion increased the emissions of products of incomplete combustion, enhancing the potential of POP formation via de novo synthesis. The study concludes that although retarding the fuel injection timing leads to a decrease in NOx emissions from diesel engines, it also results in an increase in PAH and POP emissions.

This study investigates the emission characteristics of toxic organic pollutants (PAHs, PCDD/Fs, and PCBs) generated by a heavy-duty diesel engine operating at various exhaust gas recirculation (EGR) rates during steady-state cycles. Tests on the exhaust gas composition were conducted before and after changing the EGR ratio. The fuel used in the study (B2 diesel) was a mixture of 2% biodiesel and 98% diesel. The main focus was on the emission factors for the organic toxic pollutants in the exhaust gas after EGR ratios of 0% and 5% were applied. At an EGR ratio of 5%, the total mass emission factors for the PAHs and PCBs increased by 9.1 times and 14.4 times, respectively, while the toxicity equivalent factors increased by 4.0 times and 4.8 times, respectively. A significant increase in pollutants with a higher molecular weight, particularly for the PAHs, was observed after applying an EGR ratio of 5%, implying incomplete combustion. The emission factors of carbon dioxide (CO2) and nitric oxides (NOx) decreased by 2.5% and 54.4%, respectively, when the EGR ratio was increased from 0% to 5%, but those of PM and carbon monoxide (CO) increased by 60.5% and 66%, respectively. Therefore, a combination of control strategies is necessary in order to achieve a significant reduction in the emission of all pollutants.

Particulate matter (PM) pollution (including PM2.5 and PM10), which is reportedly caused primarily by industrial and vehicular emissions, has become a major global health concern. In this study, we aimed to reveal spatiotemporal characteristics and diurnal patterns of PM2.5 and PM10 data obtained from 50 air quality sensors situated in public bike sites in Kaohsiung City on June and November 2018 using principal component analysis (PCA). Results showed that PM concentrations in the study were above the standard World Health Organization criteria and were found to be associated, although complicated, with relative humidity. Specifically, the relationship between PM concentrations and relative humidity suggest a clear association at lower PM concentrations. Temporal analysis revealed that PM2.5 and PM10 occurred at higher concentrations in winter than in summer, which could be explained by the long-range transport of pollutants brought about by the northeast monsoon during the winter season. Both PM fractions displayed similar spatial distribution, wherein PM2.5 and PM10 were found to be concentrated in the heavily industrialized areas of the city, such as near petrochemical factories in Nanzih and Zuoying districts in north Kaohsiung and near the shipbuilding and steel manufacturing factories in Xiaogang district in south Kaohsiung. A pronounced diurnal variation was found for PM2.5, which generally displayed higher peaks during the daytime than in the nighttime. Peaks generally occurred at 7:00–9:00 a.m., noontime, and 5:00–7:00 p.m., while minima generally appeared at nighttime. The diurnal pattern of PM was greatly influenced by a greater number of industrial and human transportation activities during the day than at night. Overall, a number of factors such as relative humidity and type of season, transboundary pollution from neighboring countries, and human activities, such as industrial operations and vehicle use, affects the PM quality in Kaohsiung City, Taiwan.

Cooking oil fumes (CF) coming from night market stalls exhaust contain substantial amounts of air pollutants such as carbonyl compounds that may contribute to outdoor air pollution and may have adverse health effects on the Taiwanese population. Carbonyl emission characteristics depend on several factors, which include but are not limited to, the cooking style and food material being used. The current study evaluated carbonyl compound emissions from two scenarios: a standard kitchen cooking classroom with a stack gas tunnel and night market food stalls. The different cooking styles and food types cooked using a liquefied petroleum gas (LPG) stove, such as grilled chicken with (GCS) and without sauce (GC), mixed barbecue with sauce (MBS), grilled vegetables with sauce (GVS), stir-fried oyster omelet (OM), fried Taiwanese chicken nuggets (FN) in the kitchen cooking classroom, and grilled chicken with (GCS) and without sauce (GC), stir-fried oyster omelet (OM), grilled vegetables with sauce (GVS), and fried steak (FS) in the night market were evaluated for carbonyl carbon emissions. OM from the kitchen classroom and GCS from the night market showed the highest mean total carbonyl compound concentrations (1850 ± 682 ppb and 1840 ppb). Formaldehyde was found to be the most predominant carbonyl compound, with contribution percentages ranging from 70.9–99.58% of the total carbonyl emission factors in CFs. Grilled vegetables with sauce had the highest emission factor magnitude of 274 µg kg–1 wt. Factors such as the addition of sauce and grilling were also observed to increase carbonyl compound emissions. Corresponding health risks of carbonyl compounds in CFs for the night market vendors were also assessed. All values for cancer risk (R) were above the standard R value for workplace exposure, and HQ values were all greater than 1, suggesting a high risk for adverse health effects. Although our reported values were relatively high due to our sampling conditions, our study was first to be conducted in Taiwan and holds an important contribution to the global existing data of carbonyl compound emissions.

This study investigated the atmospheric PM2.5, PM10, SO2, NO2, CO, and O3 in Urumqi and Turfan cities from 2015 to 2017. In addition, six AQI categories and AQI values and seasonal changes in the major pollutants in Urumqi and Turpan were studied. In the three-year (2015–2017) study, in Urumqi, the average proportion of grades I, II, III, IV, V, and VI in spring were 16.3%, 59.7%, 16.0%, 5.33%, 2.67%, and 0%, respectively, were 12.0%, 82.7%, 5.33%, 0%, 0%, and 0% in summer; were 13.3%, 65.7%, 16.3%, 3.33%, 1.33%, and 0% in fall, and were 0.667%, 14.3%, 22.3%, 15.3%, 33.7%, and 13.7% in winter. In the Turpan region, the mean proportion of Grade I, II, III, IV, V, and VI pollutants were 0%, 61%, 21.3%, 8.00%, 2.33%, and 7.33% in spring, respectively; were 0.67%, 74.7%, 20.0%, 2.00%, 0.67%, and 2.00% in summer, were 1.33%, 59.7%, 42.3%, 7.67%, 0.33%, and 2.00% in fall, and were 0%, 11.0%, 35.3%, 29.3%, 20.3%, and 4.00% in winter. In the three-year (2015–2017) study, based on the results of the survey, it was determined that two cities have the best air quality in summer and the worst air quality in winter. In Urumqi, when the AQI was between 101–150, the main air pollutants in 2015 were PM2.5 and PM10. In 2016, the main air pollutant was PM2.5, and in 2017, the main air pollutants were PM2.5 and PM10. In Turpan, the main air pollutants in 2015 were PM2.5 and PM10, were PM2.5, PM10, and O3 in 2016, and was PM10 in 2017. When the AQI was between 151 and 200, in Urumqi, the main atmospheric pollutant in the three-year period was PM2.5. In Turpan, the main atmospheric pollutants in the three-year period were PM2.5 and PM10. When the AQI was between 201 and 300 in Urumqi, PM2.5 was the main atmospheric pollutant from 2015–2017. In Turpan, the main atmospheric pollutants in the three-year period were PM2.5 and PM10. To summarize, in both Urumqi and Turpan, PM2.5 and PM10 were the most predominant air pollutants causing high AQI values. More attention should thus be paid to the sources and reduction of these pollutants.

Silver nanomaterials (Ag NMs) are fabricated by many biological components in our environment. Recently, research on their biosynthesis and reactions has become a focus of attention. Due to the complexity of biological systems and samples, specific processes and mechanisms involving Ag NMs are difficult to identify and elucidate on the molecular and chemical-bond level. The microorganisms and composite components of plant extracts are of great interest in many biological syntheses. Although potential biomolecules have been shown to play essential roles in biological systems in Ag NM biosynthesis, the detailed mechanism of the electron transfer process and crucial molecules that control this reaction have only recently come into focus. The reactive behavior of the Ag NMs is of great significance for understanding their overall behavior and toxicity. Additionally, only limited knowledge is available about their kinetics. All reactions involve chemical bond formation, electron transfer, or electrostatic interactions. An overview is presented of the biosynthesis of Ag NMs based on molecular supports including a nitrate reductase/NADH oxidase-involved electron transfer reaction and their mechanisms in Ag+ reduction: quinol-mediated mechanism and superoxide-dependent mechanism, and molecular supports in plant extracts, is presented. The environmental reaction kinetics and mechanisms of the interactions of Ag NMs with substances are introduced based on the formation and classification of chemical bonds. The particle-particle reaction kinetics of Ag NMs in the environment are discussed to directly explain their stability and aggregation behavior. The toxicity of Ag NMs is also presented. In addition, future prospects are summarized. This review is the first to provide an insight into the mediating molecules and chemical bonds involved in the biosynthesis, kinetics, and mechanisms of action of Ag NMs.

During 2015–2017, the atmospheric PM2.5, PM2.5/PM10, PCDD/Fs, PCDD/F phase distribution and PM2.5-bound total PCDD/Fs-WHO2005-TEQ content in Wuhu and Bengbu were investigated in this study. In addition, the sensitivity analysis for PM2.5-bound total PCDD/Fs-WHO2005-TEQ of Wuhu was also studied. During 2015–2017, the three-year average PM2.5 concentration in Wuhu was 53.0 µg m–3, and in Bengbu was 61.4 µg m–3; the results also showed the annual average PM2.5 concentrations of these two cities had declined, but the levels were still far above the WHO annual PM2.5 standard (10 µg m–3). In addition, in Wuhu, the PM2.5-bound total PCDD/Fs-WHO2005-TEQ contents in summer (0.166 ng-WHO2005-TEQ g–1) were approximately only 68.8% in magnitude lower than the average value of other three seasons (0.532 ng-WHO2005-TEQ g–1), and that of Bengbu in summer (0.187 ng-WHO2005-TEQ g–1) was approximately 66.7% in magnitude lower than the average value of other three seasons (0.561 ng-WHO2005-TEQ g–1). Sensitivity analysis showed that the PCDD/F concentration was the most positively correlated sensitive factor for PM2.5-bound total PCDD/Fs-WHO2005-TEQ, and when ΔP/P was changed from 0% to +50%, ΔS/S responded from 0% to +106%. The second positively correlated sensitive factor was PM10 concentration, and when ΔP/P was changed from 0% to +50%, ΔS/S responded from 0% to +72%. This was followed by atmospheric temperature, and its effect was negatively correlated, when ΔP/P was changed from –50% to +50%, ΔS/S responded from +73% to –112%. The last sensitive parameter was PM2.5 concentration, with the impact divided into two stages: when ΔP/P was changed from 0% to+70%, ΔS/S responded from 0% to +33%, but when ΔP/P was changed from +70% to +100%, ΔS/S responded from +33% to +25%.The results of this study provide useful information that can be used to achieve more insights into both atmospheric PM2.5 and PCDD/Fs.

During the period 2016–2017, the atmospheric wet, dry, and total deposition fluxes and scavenging ratios of the total PCDD/Fs-WHO2005-TEQ in Handan and Kaifeng were investigated. In addition, a sensitivity analysis for the dry deposition fluxes of the total PCDD/Fs-WHO2005-TEQ was conducted. The annual wet deposition fluxes of total PCDD/Fs-WHO2005-TEQ in Handan ranged between 51.1 and 83.5 and averaged 72.3 pg WHO2005-TEQ m–2 year–1, which was approximately 1.04 times of magnitude higher than that in Kaifeng (69.3 pg WHO2005-TEQ m–2 year–1). From 2016–2017, the contribution fraction of dry deposition to the total PCDD/Fs-WHO2005-TEQ deposition flux ranged between 60.8% and 100% and averaged 80.4%. Dry deposition fluxes were more dominant than wet deposition fluxes. In terms of the seasonal variations in total PCDD/Fs-WHO2005-TEQ dry deposition fluxes (the mean values for 2016 and 2017) in Handan, those in spring, summer, fall, and winter were 1084, 563, 964, and 1325 pg WHO2005-TEQ m–2 month–1, respectively, while in Kaifeng, they were 963, 428, 715, and 1016 pg WHO2005-TEQ m–2 month–1, respectively. The total PCDD/Fs-WHO2005-TEQ deposition fluxes in winter was approximately 2.0 times of magnitude higher than that in summer. The sensitivity analysis of total PCDD/FsWHO2005-TEQ dry deposition fluxes in Handan and Kaifeng showed that the PM10 concentration was the most positively correlated sensitive factor. When ΔP/P was changed from 0% to +50%, ΔS/S responded from 0% to +46.1% and +46.3%, respectively. The second positively correlated sensitive factor was the PM2.5 concentration, where when ΔP/P was changed from 0% to +50%, ΔS/S responded from 0% to +47.8% and +40.8%, respectively. For PCDD/Fs mass concentration, when ΔP/P was changed from 0% to +50%, ΔS/S responded from 0% to +32.2% and +28.1%, respectively. This was followed by the atmospheric temperature, and its effect was negatively correlated. When ΔP/P was changed from –50% to +50%, ΔS/S responded from +46.4% to –26.9% and +57.0% to –30.5%, respectively. The results of this study provide useful information that can be used to achieve more insights into both atmospheric deposition of total PCDD/Fs-WHO2005-TEQ and the sensitive factors for dry deposition fluxes.

From 2015 to 2017, the atmospheric PM2.5, the total PCDD/Fs-WHO2005-TEQ concentrations, PM2.5-bound total PCDD/Fs-WHO2005-TEQ contents, and the gas-particle partitioning of PCDD/Fs in Handan and Kaifeng were investigated. In addition, a regression analysis of the air quality index (AQI) and total PCDD/Fs-WHO2005-TEQ concentration was also studied. From 2015-2017, in Handan, the three-year average PM2.5 concentrations in spring, summer, autumn and winter were 66.9, 61.3, 74.8, and 138 µg m–3, respectively and averaged 85.3 µg m–3, which was 1.2 orders of magnitude higher than that in Kaifeng (71.1 µg m–3). The three-year average PM2.5-bound total PCDD/Fs-WHO2005-TEQ content in spring, summer, autumn, and winter in Handan were 0.88, 0.28, 0.67, and 0.72 ng WHO2005-TEQ g–1, respectively, and averaged 0.64 ng WHO2005-TEQ g–1, which was 1.1 order of magnitude higher than that in Kaifeng (0.57 ng WHO2005-TEQ g–1). The three-year average fraction of gas phase total PCDD/Fs-WHO2005-TEQ concentrations in spring, summer, autumn, and winter in Handan were 26.4%, 62.8%, 28.9%, and 3.34%, respectively, and averaged 30.4%. The three-year average fraction of gas phase total PCDD/Fs-WHO2005-TEQ concentrations in Kaifeng (34.3%) was 1.1 order of magnitude higher than that in Handan (30.4%). Positive correlations between the AQI and the total PCDD/Fs-WHO2005-TEQ concentration were found and their R2 values in 2015, 2016, and 2017 were 0.929, 0.921, and 0.876, respectively. Therefore, the AQI can be used to roughly predict the level of total PCDD/Fs-WHO2005-TEQ in ambient air through the use of a regression equation in these two cities.

The atmospheric PM2.5, total PCDD/Fs-WHO2005-TEQ concentrations, PM2.5-bound total PCDD/Fs-WHO2005-TEQ content, gas-particle partitioning and wet deposition of PCDD/Fs in Jinan and Weihai, from 2015 to 2017, were investigated, respectively. Furthermore, a regression analysis of the air quality index (AQI) and total PCDD/Fs-WHO2005-TEQ concentrations was studied as well. From 2015–2017, the three-year average PM2.5 concentrations in Jinan and Weihai were 76.1 and 32.9 µg m–3, respectively. The three-year average total PCDD/Fs-WHO2005-TEQ concentrations in Jinan and Weihai were 0.0866 and 0.0396 pg-WHO2005-TEQ m–3, respectively, indicating that maritime climate regulation contributes to the spread of pollutants. The three-year average fraction of gas phase total PCDD/Fs-WHO2005-TEQ concentrations in spring, summer, autumn, and winter in Jinan were 26.1%, 63.8%, 30.5% and 4.62%, respectively; while, those in Weihai were 30.7%, 74.5%, 44.4%, and 8.41%, respectively. In 2016, the annual wet deposition fluxes in Jinan and Weihai were 1288 and 483 pg WHO2005-TEQ m–2 year–1, respectively. The annual scavenging ratios of total PCDD/Fs-WHO2005-TEQ were 33080 and 30870 in Jinan and Weihai, respectively. The total concentration of PCDD/Fs-WHO2005-TEQ increased with an increase of AQI and showed a positive correlation; the R2 values of three years (2015, 2016, and 2017) were 0.873, 0.847, and 0.744, respectively. Therefore, knowing the AQI value, the total concentration of PCDD/Fs-WHO2005-TEQ in the ambient air can be roughly estimated using a regression equation.

In this study, the atmospheric PM10, SO2, NO2, CO, and O3 concentration from 2015-2017, in Handan and Kaifeng were investigated. Besides, the seasonal variations of AQI values and their corresponding primary pollutants of six AQI grades were also discussed. In Handan, the daily AQI values ranged from 22 to 500 in 2015, from 19 to 500 in 2016, and from 27 to 500 in 2017, for which the corresponding average values were 143, 132 and 151, respectively. In Kaifeng, the daily AQI ranged from 25 to 496 in 2015, from 20 to 420 in 2016, and from 21 to 434 in 2017, for which the corresponding average values were 129, 124 and 131, respectively. During the three-year study, in Handan, the average proportion of grades I, II, III, IV, V and VI were 4.0%, 35.0%, 25.6%, 31.7%, 2.5% and 1.2% in spring; were 4.0%, 35.1%, 22.6%, 35.8%, 2.5% and 0% in summer; were 14.2%, 31.0%, 15.3%, 35.8%, 3.7% and 0% in fall, and were 3.3%, 26.1%, 20.0%, 37.8%, 8.1% and 4.7% in winter. In Kaifeng, the average proportion of grades I, II, III, IV, V and VI were 2.6%, 34.0%, 24.4%, 36.1%, 2.6% and 0.3% in spring; were 18.2%, 41.9%, 21.8%, 17.0%, 1.1% and and 0% in summer; were 8.6%, 34.3%, 17.4%, 34.8%, 4.9% and 0% in fall, and were 2.1%, 15.1%, 7.8%, 44.5%, 26.2% and 4.3% in winter. Overall, the air quality in the two cities were the worst in winter. The AQI values were between 101 and 150, where in Handan, PM2.5, PM10, and O3 were the primary air pollutants over the three years. In Kaifeng, the primary air pollutants were PM2.5, PM10, NO2, and O3 in 2015; were PM2.5, PM10, and O3 in 2016, and were PM2.5, PM10, and O3 in 2017. When AQIs ranged between 151 and 200, in Handan, the primary air pollutants were PM2.5, PM10, and O3 in both 2015 and 2016, and were PM2.5, PM10, NO2, and O3 in 2017. In Kaifeng, PM2.5, PM10, and O3 were the primary air pollutants from 2015-2017. When AQIs were between 201 and 300, in Handan, the primary air pollutants were PM2.5 and PM10 in 2015 and were PM2.5 and O3 in 2017. In Kaifeng, the primary air pollutants comprised PM10 in 2015, PM2.5 and PM10 in 2016, and PM2.5 and O3 at the same time. When the AQI values were between 301 and 500, which did not occur in Handan in 2015, the primary air pollutants comprised PM10 in 2016, PM2.5 and PM10 in 2017, and in Kaifeng from 2015-2017, PM2.5, and PM10 were the primary air pollutants. This study investigated the AQI values and corresponding primary pollutants in each season in more detail, the control strategies for these air pollutants will be more precisely.

From 2015–2017, the atmospheric PM10, SO2, NO2, CO, and O3 in Wuhu and Bengbu were investigated in this study. In addition, the AQI values and seasonal variations in six AQI classes and corresponding primary pollutants were also studied. In Wuhu, the daily AQI ranged from 23 to 298 in 2015, from 33 to 290 in 2016, and from 34 to 278 in 2017, and the corresponding mean values were 81, 80 and 90, respectively. In Bengbu, the daily AQI ranged from 23 to 288 in 2015, from 32 to 286 in 2016, and from 27 to 500 in 2017, and the corresponding mean values were 88, 89 and 97, respectively. During the three-year study, in Wuhu, the mean proportion of levels with Grade I, II, III, IV, V and VI were 9.33%, 69.3%, 18.3%, 3.00%, 0% and 0% in spring; were 35.0%, 55.0%, 7.00%, 3.00%, 0% and 0% in summer; were 13.6%, 65.0%, 18.0%, 3.33%, 0% and 0% in fall, and were 5.33%, 48.7%, 30.7%, 9.67%, 5.67% and 0% in winter. In Bengbu, the mean proportion of levels with Grade I, II, III, IV, V and VI were 3.00%, 64.0%, 30.3%, 2.67%, 0.333% and 0.333% in spring; were 19.3%, 68.7%, 11.3%, 0.667%, 0% and 0% in summer; were 20.7%, 56.3%, 17.3%, 4.67%, 1.00% and 0% in fall, and were 9.67%, 36.7%, 31.0%, 32.0%, 5.67% and 0% in winter. Generally, the air quality in the two cities were in the following order: summer > fall > spring > winter. AQI ranged between 101–150, where in Wuhu, the primary air pollutants were PM2.5 and NO2 in 2015; were PM2.5, NO2 and O3 in 2016, and were PM2.5, PM10, NO2 and O3 in 2017. In Bengbu, PM2.5, PM10 and O3 were the primary air pollutants during the three years. When AQIs ranged between 151 and 200, in Wuhu, the primary air pollutant was PM2.5 in 2015; were PM2.5 and PM10 in 2016, and were PM2.5, PM10, and O3 in 2017. In Bengbu, the primary air pollutant was PM2.5 in 2015 and 2016 and comprised PM2.5 and O3 in 2017. When AQIs were between 201 and 300, in Wuhu, PM2.5 was the primary air pollutant in 2015–2017. In Bengbu, the primary air pollutant was PM2.5 in 2015 and 2016 and comprised PM2.5 and PM10 in 2017. When the AQI ranged between 301–500, which did not occur in Wuhu from 2015–2017 or in Bengbu during 2015–2016, PM2.5 was as the primary air pollutant in Bengbu in 2017. When the AQI can be analyzed in more detail, the control strategies for air pollution will be more precise.

This study investigated atmospheric PM2.5 concentration, PM2.5/PM10 ratio, total PCDD/Fs concentration, PCDD/F phase distribution, PM2.5-bound total PCDD/Fs-WHO2005-TEQ content, and dry deposition of PCDD/Fs for Xiamen and Zhangzhou Cities during 2015–2017, and sensitivity analysis of both atmospheric PM2.5-bound total PCDD/Fs-WHO2005-TEQ content and dry deposition of PCDD/Fs in these two cities. During 2015–2017, the three-year average concentration of PM2.5 in Xiamen was 27.6 µg m–3, while that of Zhangzhou was 33.9 µg m–3; this level is still higher than the WHO annual PM2.5 standard (10.0 µg m–3). In addition, the summer PM2.5-bound total PCDD/Fs-WHO2005-TEQ content in Xiamen and Zhangzhou Cities was 0.131 ng-WHO2005-TEQ g–1 and 0.161 ng-WHO2005-TEQ g–1. And it is lower than the average of the other three seasons. In Xiamen, the average monthly dry deposition flux in these three years was 322 pg WHO2005-TEQ m–2 month–1, while that of Zhangzhou was 378 pg WHO2005-TEQ m–2 month–1, respectively. Sensitivity analysis of atmospheric PM2.5-bound total PCDD/Fs-WHO2005-TEQ content showed that the most sensitive parameters are total PCDD/F mass concentration and PM10 concentration, followed by atmospheric temperature and PM2.5 concentration; in addition, the sensitivity analysis of atmospheric dry deposition is similar to those of atmospheric PM2.5-bound total PCDD/Fs-WHO2005-TEQ content. The results of this study provide useful information for better understanding PM2.5, particle-bound PCDD/Fs content and PCDD/Fs dry deposition in the ambient air of urban cities.

Benzene dye intermediate (BDI) 4-methoxy-2-nitroaniline (4M2NA) wastewater has caused significant environmental concern due to its strong toxicity and potential carcinogenic effects. Reports concerning the degradation of 4M2NA by advanced oxidation process are limited. In this study, 4M2NA degradation by Fenton oxidation has been studied to obtain more insights into the reaction mechanism involved in the oxidation of 4M2NA. Results showed that when the 4M2NA (100 mg L−1) was completely decomposed, the TOC removal efficiency was only 30.70–31.54%, suggesting that some by-products highly recalcitrant to the Fenton oxidation were produced. UV-Vis spectra analysis based on Gauss peak fitting, HPLC analysis combined with two-dimensional correlation spectroscopy and GC-MS detection were carried out to clarify the degradation mechanism and pathway of 4M2NA. A total of nineteen reaction intermediates were identified and two possible degradation pathways were illustrated. Theoretical TOC calculated based on the concentration of oxalic acid, acetic acid, formic acid, and 4M2NA in the degradation process was nearly 94.41–97.11% of the measured TOC, indicating that the oxalic acid, acetic acid and formic acid were the main products. Finally, the predominant degradation pathway was proposed. These results could provide significant information to better understand the degradation mechanism of 4M2NA.

This study investigated the monthly average dry, wet and total deposition fluxes in total-PCDD/Fs-WHO2005-TEQ in Wuhu and Bengbu, respectively. In addition, sensitivity analyses for both scavenging ratio and wet deposition of total-PCDD/Fs-WHO2005-TEQ in Wuhu were also conducted. In 2015, the annual dry deposition fluxes, wet deposition fluxes, and total deposition fluxes were 6407, 1538, and 7945 pg WHO2005-TEQ m–2 year–1 in Wuhu, and were 7101, 1525, and 8626 pg WHO2005-TEQ m–2 year–1 in Bengbu. The annual scavenging ratios of total-PCDD/Fs-WHO2005-TEQ were 30144 and 31267 in Wuhu and Bengbu, respectively. As to the sensitivity analysis for the scavenging ratio of total-PCDD/Fs-WHO2005-TEQ, the most positive sensitivity parameters were PCDD/Fs concentration and PM10 concentration; the second positively correlated sensitivity parameter was PM2.5 concentration, then, followed by atmospheric temperature, which was negatively correlated; the last negative correlated sensitivity factor was the rainfall. In terms of the sensitivity analysis for wet deposition of total-PCDD/Fs-WHO2005-TEQ, the most positive sensitivity parameter was air temperature; the second positive or negative correlated sensitivity factor was atmospheric PCDD/Fs mass concentration, followed by PM2.5 and PM10 concentration, which were positively correlated; the last positive correlated sensitivity factor was the rainfall. This study led to greater insight into the parameters affecting the atmospheric wet deposition of PCDD/Fs, which will benefit development of appropriate control strategies for PCDD/Fs and provided useful information for the scientific community.

The metal-free graphitic carbon nitride is a promising photocatalyst for peroxymonosulfate (PMS) activation towards water decontamination, but bearing low efficiency due to its electronic structure and surface chemistry. Herein, the non-metallic element boron was adopted for catalyst development. The boron dopants and defects were simultaneously introduced by potassium borohydride, resulting in an excellent activity towards PMS activation. The dominant reactive oxygen species was singlet oxygen, which was determined to originate from PMS activation over photo-induced holes initiated by an electron transfer process. Calculations based on density functional theory revealed that at excited states, due to the dopants and defects, the electron-hole distribution was altered from an even population to a significant separation, which was beneficial for photocatalytic performance. Besides, the engineered electronic structure weakened the catalyst resistance to charge transfer, enabling easier electron transfer between the catalyst and the PMS. Moreover, the strengthened and enlarged positive electrostatic potential areas on heptazine rings oriented the electron transfer process from the negatively charged PMS to the catalyst, facilitating the generation of singlet oxygen. These findings provide underlying mechanism insights into the contribution of dopants and defects to catalytic performance on persulfate-based photocatalytic water treatment.

The long-term abuse of antibiotics such as norfloxacin (NOR) poses a significant threat to aquatic environments. The development of efficient and economical treatments is still a pain point in the industry. Herein, we reported a directly robust carbonization-pyrolysis method to synthesize iron and nitrogen co-doped biochar material (Fe@N co-doped biochar) that was first applied to NOR removal through persulfate (PS) activation. The catalytic performance and operating factors were systematically investigated. It was found that 10 mg/L NOR achieved 95% degradation within 20 min under optimal reaction conditions. The removal rate of NOR could still achieve 80% and almost 50% of NOR was completely mineralized after five cycles. Through combined electron-paramagnetic-resonance analysis, quenching experiments, and X-ray-photoelectron-spectroscopy tests, •OH, •SO4−, and 1O2 were confirmed as reactive oxygen species in catalytic reaction. Iron activated PS to produce •OH and •SO4− through electron transfer and nitrogen-containing functional groups (graphitic N, C-OH/C = N) accepted electrons from PS to generate 1O2. The radical pathway involving hydroxyl radicals and the nonradical pathways involving singlet oxygen together accounted for the rapid degradation of NOR. The degradation pathways were comprehensively established, including defluorination, decarboxylation, piperazine ring breakage and nalidixic ring transformation. This study shed light on a new mechanism of radical and nonradical co-dominated PS activation and proposed a simple and inexpensive antibiotic wastewater treatment system.

In this study, manganese peroxidase (MnP) was applied to induce the in vitro oxidation of sulfamethoxazole (SMX). The results indicated that 87.04% of the SMX was transformed and followed first-order kinetics (kobs = 0.438 h−1) within 6 h when 40 U L−1 of MnP was added. The reaction kinetics were investigated under different conditions, including pH, MnP activity, and H2O2 concentration. The active species Mn3+ was responsible for the oxidation of SMX, and the Mn3+ production rate was monitored to reveal the interaction among MnP, Mn3+, and SMX. By integrating the characterizations analysis of the MnP/H2O2 system with the density functional theory (DFT) calculations, the proton-coupled electron transfer (PCET) process dominated the catalytic circle of MnP and the transformation of Mn3+. Additionally, possible oxidation pathways of SMX were proposed based on single-electron transfer mechanism, which primarily included the S–N bond cleavage, the C–S bond cleavage, and one electron loss without bond breakage. It was then transformed to hydrolysis, N–H oxidation, self-coupling, and carboxylic acid coupling products. This study provides insights into the atomic-level mechanism of MnP and the transformation pathways of sulfamethoxazole, which lays a significant foundation for the potential of MnP in wastewater treatment applications.

Cu2O micro-sized crystals was synthesized through a hydrothermal reaction of CuCl2 and NaOH solution adding ascorbic acid (AH2) as reductant. The morphology changed from truncated octahedral to six-corners-{1 1 1} truncated octahedral along with the increasing molar ratio of NaOH/CuCl2. The preferential growth rates of the {1 1 1} and {1 1 0} faces affected by the concentration of [Cu(OH)4]2−, resulting in the morphological evolution. The sufficient AH2 has an etching effect to form a quasi-spherical Cu2O structure. The highly-truncated octahedral Cu2O with the dominant {1 1 0} faces has higher adsorption and also photocatalytic activity with a methyl orange (MO) degradation rate of 90.3% under visible light. It’s proposed that the {1 1 0} faces of Cu2O microcrystals possess higher photocatalytic activity than {1 1 1} faces, and are even more active than the {1 0 0} faces.

The atmospheric PM2.5, PM2.5/PM10, PCDD/Fs-WHO2005-TEQ, and PCDD/F (polychlorinated dibenzo-p-dioxins and dibenzofuran) phase distributions of 23 cities in southern China, during 2014–2016, were investigated in this study. In general, the cities with higher latitudes had higher PM2.5 concentrations than those with lower latitudes. During 2014–2016, the lowest three-year average concentrations of PM2.5 occurred at Sanya and Haikou and were 16.4 and 21.7 µg m–3, respectively; while the highest concentrations of PM2.5 was occurred at Wuhan and Luzhou and were 68.8 and 63.1 µg m–3, respectively. During 2015–2016, the PM2.5 concentrations of most of cities decreased, but those of five cities (Chengdu, Luzhou, Nanchang, Qujing and Quanzhou) increased, indicting that the air quality of these five cities was still not well controlled. The average RM values of the 23 cities were 5.20, 4.49 and 4.13 in 2014, 2015 and 2016, respectively, which revealed that the PM2.5 concentrations in the cities of southern China slowly decreased, although they were still far above the WHO air quality regulated standard (10 µg m–3). In general, a city with a higher PM2.5 concentration was also had a higher PM2.5/PM10 ratio. Among the 23 cities, the six highest three-year averages of total-PCDD/Fs-WHO2005-TEQ concentrations were 0.0665, 0.0633, 0.0625, 0.0600, 0.0528 and 0.0526 pg-WHO2005-TEQ m–3 in Chengdu, Wuhan, Nanjing, Hefei, Luzhou and Hangzhou, respectively. During 2014, the six cities (Hefei, Nanjing, Wuhan, Guiyang, Shanghai and Chengdu) with the lowest temperatures in winter (an average of 5.4°C), their average particle phase fractions of total-PCDD/Fs-WHO2005-TEQ that were approximately 76%, 53%, 71% and 93% in the spring, summer, fall and winter, respectively; while, the six cities (Haikou, Fuzhou, Guangzhou, Nanning, Nanchang and Changsha) with the highest temperatures in summer (an average of 16.5°C), had average particle phase fractions of total-PCDD/Fs-WHO2005-TEQ that were approximately 61%, 42%, 57% and 81% in the spring, summer, fall and winter, respectively. The results of this study provide information showing the trends of both atmospheric PM2.5 and PCDD/Fs in the cities of southern China. In addition, this study provided the overview relating to the PM2.5 and PCDD/Fs in ambient air of southern China, which was not reported in previous studies. The results of this study were of great importance to present the trends of air quality in China. It is also useful for the establishment of control strategies in the future.

Monitoring atmospheric deposition fluxes (dry and wet deposition) is of great importance in tracing the environmental fate and behavior of PCDD/Fs. To further understand the characteristics of both dry and wet PCDD/F deposition in Northern China, two cities, namely Harbin and Shijiazhuang were investigated. During 2014, in Harbin, the monthly dry deposition fluxes of total-PCDD/Fs-WHO2005-TEQ ranged between 308 and 1290 pg WHO2005-TEQ m–2 month–1, with an annual flux of 8240 pg WHO2005-TEQ m–2 year–1; however, in Shijiazhuang, the dry deposition fluxes ranged from 699 to 2230 pg WHO2005-TEQ m–2 month–1, with an annual 15400 pg WHO2005-TEQ m–2 year–1. Monthly dry deposition velocities of particle phase total-PCDD/Fs-WHO2005-TEQ are similar, ranging between 0.42 and 0.94 cm s–1 (average 0.59 cm s–1) and between 0.42 and 0.92 cm s–1 (average 0.6 cm s–1) in Harbin and Shijiazhuang, respectively. Due to the low level of rainfall in Northern China, the monthly wet deposition fluxes were in the range of 3–79.9 (369 pg WHO2005-TEQ m–2 year–1) and 0–140 pg WHO2005-TEQ m–2 month–1 (622 pg WHO2005-TEQ m–2 year–1) in Harbin and Shijiazhuang, respectively. In addition, the average scavenging ratios of total-PCDD/Fs-WHO2005-TEQ were 31900 and 30700 in Harbin and Shijiazhuang, respectively. Combined with dry and wet deposition, the annual total (dry + wet) deposition flux in Shijiazhuang (16100 pg WHO2005-TEQ m–2 year–1) is 1.9 times of magnitude higher than that in Harbin (8610 pg WHO2005-TEQ m–2 year–1). The results indicated that the dry deposition flux was the major mechanism for removal of PCDD/Fs from the atmosphere in Northern China. By examining both the PM2.5 level and total-PCDD/Fs-WHO2005-TEQ deposition in Northern China, and comparing the values with those found in other places, it is clear that there is an urgent need to control the particulate emissions in this area.

The characteristics of dissolved organic matter (DOM) in inflowing river, flowing into drinking water, have profound influences on the quality and safety of water. Here, ultraviolet–visible (UV–vis) spectroscopy and three-dimensional fluorescence (EEM) spectroscopy were combined to investigate the spatiotemporal variations of DOM in Nanfei River flowing into Chaohu Lake in China. 24 water samples and 24 surface sediments samples (including dry-to-wet transition season and wet season in 2018) were collected from different types of outlets. Parallel factor analysis (PARAFAC) model and correlation analysis were conducted to identify the primary sources of DOM. Two humic-like components (C1 235–250 nm/385–430 nm and C3 255–270 nm/455–510 nm) and one tryptophan-like component (C2 270–290 nm/320–350 nm) were effectively identified by PARAFAC model. The results showed DOM concentration presented significant spatiotemporal variations. The concentration was much lower in water than in surface sediments in dry-to-wet transition season, but higher in the wet season. Fluorescence index (FI), biological index (BIX) and humification index (HIX) were used to judge characteristic of DOM origination. These indexes indicated that, DOM in Nanfei River had both the characteristics of humus and autogenous, but neogene autogenic feature was stronger, which was largely due to mixture of water, resuspension and desorption of DOM in sediments and photochemical degradation. In addition, the characteristic parameter of molecular mass of DOM (the values of M) had an obvious linear relationship with the fluorescence intensity ratio of fulvic acid-like to humic acid-like (C1/C3), indicating that macromolecular substances could be removed by adding or improving membrane treatment. These provided technical support for improving quality and comprehensive treatment of drinking water sources.

With the rapid construction of dams worldwide, reservoir system has become a representation of modern aquatic environment. However, the profiles of antibiotic resistance genes (ARGs) and associated factor influencing their dynamics in modern aquatic environment (e.g., water phase, sediment phase, and soil phase) are largely unknown. Here, we comprehensively characterized the diversity, abundance, distribution of ARGs in a large drinking water reservoir using high-throughput quantitative PCR, as well as ranked the factors (e.g., mobile genetic elements (MGEs), bacteria community, bacterial biomass, antibiotics, and basic properties) influencing the profiles of ARGs on the basis of structural equation models (SEMs). Water phase was prone to harbor more diverse ARGs as compared to sediment phase and soil phase, and soil phase in drawdown area was a potential reservoir and hotspot for ARGs. Environmental media partially affected the ARG diversity in modern aquatic environment, while it observably influenced the distributions of ARGs and MGEs and their co-occurrence patterns. The pathways for the proliferation and spread of ARGs in water phase were both the horizontal gene transfer (HGT) and vertical gene transfer (VGT), while the dominant pathways in sediment phase and soil phase were the HGT and VGT, respectively. The SEMs demonstrated that MGEs contributed the most to drive the ARG dynamics in both water phase and sediment phase, while the most dominant factor for this in soil phase was bacterial community. Overall, environmental media exerted a bottleneck in driving the dynamics of ARGs in modern aquatic environment probably via diversifying the MGEs, bacterial community, bacterial biomass, antibiotics and basic properties.

Harmless treatment of antibiotics, and recovery of precious metals from the spent Li-ion battery are two typical environmental issues with rapid development of the society. Presently, we reclaimed Mn from the spent Li-ion battery cathode materials for hydrothermally synthesizing MnO2/Fe(0) composites, which were used as the efficient heterogeneous photo-Fenton catalyst. The new composite was well characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) methods before optimizing their usage for sulfadiazine destruction. The catalytic efficiency of the MnO2 substrate was enhanced by impregnating different proportions of Fe(0) into the substrate. The MnO2: Fe(0) molar ratio at 40:1 (MnO2-40Fe) shows optimal catalytic activity. Sulfadiazine degradation by 0.2 g/L MnO2-40Fe, 6 mM H2O2 in pH 3 is almost 98.6%, and it follows first-order kinetics. The MnO2 and nano zero-valent iron synthesized using spent cathode of Li-ion batteries is equally efficient in sulfadiazine even after five times repeated use. As elucidated by mass spectroscopic data, sulfadiazine degradation by MnO2-40Fe was a multi-faceted photo-Fenton process which results in CO2, H2O, NH4+ and SO42− as final products. The excellent degradation performance of the as-prepared catalyst might be attributed to the introduction of nano zero-valent iron on the nanostructured MnO2, which not only provides more active sites, but also has a synergistic effect with MnO2 and light irradiation, leading to the generation of large amounts of activated radicals for destructing sulfadiazine. This work provides a promising method for reclamation of spent Li-ion battery cathode for environmental applications.

The visible light sensitive metal-free mesoporous graphitic carbon nitride (mpg-CN) was fabricated for photodegradation of atenolol (ATN), a widely used drug for cardiovascular diseases. Peroxydisulfate (PDS) as an electron acceptor as well as a radical origin was introduced to enhance the catalytic performance, and retaining the nature of metal-free and mesoporous of mpg-CN. The photo-induced holes, SO4 − and O2 − were identified as the active species. Integrated with density functional theory (DFT) calculations and photoelectrochemical experiments, the interaction among PDS, catalyst, and ATN is unveiled. PDS can obtain an electron from the catalyst, hence to improve the separation of electron-hole pairs and activates itself. ATN has stable chemical adsorption states on catalyst surface. Then the electron-deficient catalysts can acquire electrons from ATN. In addition, primary degradation sites of ATN and following possible degradation pathways were explored with DFT calculations and mass spectrometry analysis.

The fate of antibiotics has mostly been studied in lab-scale systems. Few studies have precisely evaluated the attenuation of antibiotics in natural streams. We used Lagrangian sampling combined with a tracer test and one-dimensional transport with inflow and storage model (OTIS) to reveal the effects of dilution and self-attenuation processes, and diurnal variation of light on the degradation of 14 antibiotics in a 3.6 km low-flow stream. The results showed that the order of in-stream attenuation rates were macrolides (0.18–0.25 h−1) > tetracyclines (0.16–0.18 h−1) > fluoroquinolones (0.094–0.13 h−1) > sulfonamides (0.056–0.082 h−1); half of the mass of antibiotics were lost within 0.44–1.96 km. The dilution effect, including longitudinal dispersion and transient storage, accounted for 20.70%–91.60% of the total attenuation while self-attenuation processes accounted for 8.40%–79.30%. Over 60% of sulfonamides were dissipated by dilution, while over 68% of the removal of macrolides and tetracyclines was attributed to self-attenuation. A comparison of the attenuation rates between day and night demonstrated that photo-dependent attenuation played a dominant role, especially for sulfonamides, accounting for more than 50% of their self-attenuation. Photo-independent attenuation reduced most macrolides and tetracyclines. This in situ experiment increased our understanding of antibiotic attenuation in natural streams.

Iron Oxychloride (FeOCl) was prepared by partial thermal decomposition and was studied as a heterogeneous Fenton catalyst to degrade tetracycline (TC). SEM, XRD, XPS technology were used to characterize its performance. The influencing factors of TC degradation efficiency were studied, including pH value, H2O2 content, catalyst dosage and initial TC concentration. The results showed that under the optimal conditions, the degradation rate of 60 mg L−1 TC reached 92.9% within 60 min of reaction. The degradation process follows a second-order kinetic equation. Compared with other iron-based catalysts, FeOCl exhibited better catalytic and degradation effects. Moreover, FeOCl/H2O2 system exhibited a wide pH range (from 3.0 to 7.0) for efficient degradation of TC and showed excellent stability and reusability. Meanwhile, based on the intermediates identified by HPLC-MS, two possible pathways for the degradation of TC were proposed. Further, the results of electron spin-resonance spectroscopy and radical quenching tests suggested that the ·OH formed in the FeOCl/H2O2 system was mainly responsible for the degradation of TC.

Classical Fenton and Fenton-like processes destruct organic pollutants in water non-selectively to complete mineralization. However, the usage of classical Fenton or Fenton-like processes is often limited due to the narrow operational pH window, sludge accumulation, inefficient H2O2 and efficiency decline. To overcome these constraints, in this study, we used a homogeneous Fe3+-Ce3+-H2O2 Fenton-like process to degrade catechol at different experimental conditions. At pH 7, almost 97% of 10 mM catechol can be destructed within 60 min while the degradation by Classical Fenton or Fe3+-H2O2 Fenton-like process only 36.2% and 23.7%. The resultant solution after the degradation contains only traces of cerium ions. The sludge created by the process was extensively characterized by FTIR and XPS spectroscopy to elucidate the fate of cerium ions. Electron spin resonance (ESR) data confirmed •OH as the major free radical in Fe3+-Ce3+-H2O2 process. Our Fenton-like process widens the optimal pH values to neutral condition.

Struvite crystallization was one of the most promising techniques for nutrient recovery from nutrient-rich wastewater. However, As(V) derived from the wastewater has been proved to adversely affect struvite crystallization. Constant composition technique was employed to quantify the effect of As(V) on struvite crystallization in the presence of As(V) under various operational conditions such as supersaturation, pH and ionic strength. Subsequently, the interaction mechanisms between As(V) and struvite crystals were further elucidated by means of XPS and FTIR. Interestingly, the roles of adsorption and coprecipitation in the interaction under various operational conditions were primarily evaluated. At a supersaturation of 0.4, pH 8.5 and 0.1 mol/L NaCl, the crystal growth rate of struvite was substantially reduced from (14.2 ± 0.3) × 10−6 to (7.6 ± 0.1) × 10−6 mol/min with As(V) concentration increasing from 0 to 10 mg/L. Nevertheless, As(V) scarcely changed the surface diffusion growth mechanism of struvite. Moreover, the adsorption and coprecipitation of As(V) accounted for its interaction with struvite. Thereinto, the adsorption mechanism was triggered by the bidentate inner-sphere surface complexes and the electrostatic interaction between As(V) and struvite. Furthermore, the influence of supersaturation and ionic strength on the inhibitory effect was found to be highly dependent of the adsorption of As(V), whereas the coprecipitation of As(V) is mainly responsible for the impact of pH. The finding herein provided a novel approach to elucidate the inhibitory mechanisms of heavy metals on struvite crystallization, which facilitated to obtain pure struvite crystals from the wastewater contaminated by heavy metals.

The construction of highly efficient photo-induced degradation methods is essential for water remediation. A novel nanocomposite was firstly synthesized, which was consisted of Ag nanoparticles immobilized on black phosphorus nanosheets (AgNPs@BP). The structure, surface area and morphological properties of AgNPs@BP composite were broadly investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The factors which is crucial to the degradation efficiency of norfloxacin including light conditions, pH value, catalyst type, reaction temperature, catalyst dosage and initial norfloxacin concentration, were investigated. The photocatalytic performance of the designed samples was investigated based on the photo-induced degradation of norfloxacin under near infrared light irradiation. The results confirmed that under the optimal conditions, about 85.0% of norfloxacin was rapid degraded within 90 min. In addition, this AgNPs@BP can be easily reused for 5 cycles without significantly reducing catalytic activity. Generally, a photocatalytic mechanism is proposed based on monitoring of •O2− in the reaction. The enhanced photocatalytic activity of AgNPs@BP nanocomposite was ascribed to the sensitization of BP nanosheets by fully harvest of near infrared light and high electron-hole separation efficiency. This work broadens the applications of BP and highlights its promise in the treatment of environmental pollution.

Drinking water reservoir is threatened globally due to anthropogenic contamination and thus in need of more attention. Here, we comprehensively investigated the occurrence, distribution and risk assessment of representative antibiotics in a large drinking water reservoir (Fengshuba Reservoir, China). The total concentrations of antibiotics in the water phase, porewater phase, sediment phase and soil phase (drawdown area) were in the ranges of 195–569 ng/L, 47.1–333 ng/L, 114–272 μg/kg and 2.84–77.2 μg/kg, respectively. The dominant antibiotic was CIP in both the water and porewater phases, while it was OTC in the sediment phase. For the water phase, seasonal factor consisting hydrologic condition and pattern of antibiotic use could influence the occurrence level and environmental fate of antibiotics. In contrast, exogenous particles derived from the soils that had used manures during the spring planting season coupled with heavy rainfall was responsible for the occurrence level and composition of antibiotics in the sediment phase. Moreover, Chl-α, NO3−, TP and EC were the most dominant factor influencing the antibiotic distributions in the water phase, porewater phase, sediment phase and soil phase, respectively. Pseudo-partitioning coefficients indicated that PENV and PENG might accumulate more easily into the sediments from the aqueous phase compared with other antibiotics. Risk assessments suggested that TC might pose high risks to the aquatic ecosystem, but the antibiotics presented no risk to the health of consumers. Generally, TC could be used as a promising indicator for evaluating the occurrence and potential risk of antibiotics in Fengshuba Reservoir.

The construction of heterogeneous Fenton-like catalyst with high efficiency is crucial for wastewater treatment. In this study, magnetite nanoparticles were successfully embedded into chitosan beads to form a porous structure (Fe3O4-Cs) by in-situ or two-step method, and it was put forward as a kind of Fenton-like catalyst to degrade tetracyclines for the first time. SEM, TEM, XRD, FT-IR, XPS, TG and BET technologies were used to characterize its properties. After comparing the tetracycline hydrochloride (TC) degradation efficiencies of two prepared beads, the in-situ method was selected for subsequent studies. The influential factors of TC degradation efficiency were investigated, including iron content, pH value, the amount of H2O2, reaction temperature, catalyst dosage and initial TC concentration. The results showed that under the optimal conditions, about 96.0% of TC (48.09 mg/L) and 68.3% of total organic carbon (TOC) were degraded within 20 min and 120 min, respectively. The degradation efficiencies for the other two tetracyclines: oxytetracycline (OTC) and doxycycline hyclate (DOTC), have been explored as well. And the degradation process followed pseudo first order kinetic equation. In addition, these Fe3O4-Cs beads with saturated magnetization could be easily reused for 6 cycles without significantly reducing catalytic activity. High degradation performance of beads was attributed to the stable porous structure, abundant active sites and possible synergistic effects between two components, which promoted the formation of hydroxyl radicals (HO ) for TC degradation. The possible reaction pathways and mechanism on TC degradation were discussed technically. In short, these results indicated that macroscopic Fe3O4-Cs beads (3–4 mm) with high efficiency, excellent stability and reusability exhibited a superior Fenton-like process on the removal of tetracyclines for future application.

To understand how granular activated carbon (GAC) promotes methanogenesis, batch tests of CH4 production potential in anaerobic serum bottles with addition of GAC or not were conducted. Tests showed that GAC promoted methanogenesis remarkably, but the non-conductive zeolite did not. The qPCR demonstrated that the biomass on GAC contributed little to the promotion. High-throughput sequencing data implied that promotion was related with direct interspecies electron transfer between Geobacteraceae and Methanosaetaceae. According to the c-type cytochromes (c-Cyts) response to the supplement of GAC, it was speculated that GAC may play the role of c-Cyts' substitution. In the undefined cultures, the phenomenon that c-Cyts were repressed by GAC was first observed. This research provided new evidence to microbial mechanism of promoting methanogenesis via GAC.

Struvite crystallization has been so far proved to be a potential technology for nitrogen and phosphorus recovery from nutrient-rich wastewater. However, humic acid (HA) among organic matters in nutrient-rich wastewaters would inevitably exert an adverse impact on the crystallization. Therefore, in the present study, we innovatively propose a process monitor chart to accurately differentiate and quantify the nucleation and crystal growth of struvite crystallization by means of constant composition technique, thereby probing the effect of HA on the nucleation and growth kinetics of struvite. Moreover, the mechanism underlying the interaction between HA and struvite crystals was also explored by FTIR and XPS analysis. The results indicated that HA not only significantly prolonged the induction time, but also decreased the growth rate of struvite crystals. This can be explained by the fact that HA is prone to complex with the reactant, and its subsequent adsorption on the surface of struvite crystals performs during the crystallization process. Consequently, the crystal morphology initially varied from rod-like shape to trapezoidal prism, and ultimately to triangular prism, as HA concentration gradually increased from 0 to 100 mg/L. Interestingly, the interaction between HA and struvite crystals is likely to be triggered by the formation of amide, HA-Mg2+ complex and phosphate ester on the crystal surface. These findings herein put forward an innovate method to elucidate the inhibitory effect of organic matter on the nucleation and growth kinetics of struvite, which can provide a theoretical basis for understanding the interference of organic pollutants with struvite crystallization.