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Background and Aims: With an increasing understanding of hepatitis B, the antiviral indications have been broadening gradually. To evaluate the effectiveness of tenofovir alafenamide (TAF) in chronic hepatitis B (CHB) patients with normal alanine aminotransferase (ALT) and detectable hepatitis B virus (HBV) DNA, those who are ineligible for broader antiviral criteria from the Chinese CHB prevention guide (2019)., Methods: A total of 117 patients were recruited and their data were collected from paper or electronic medical records. HBV DNA and liver function were measured at baseline and throughout the 24-week follow-up. The effectiveness endpoint was complete virological response. The safety endpoint was the first occurrence of any clinical adverse event during the treatment., Results: Among the 117 patients, 45 had normal ALT as well as detectable HBV DNA and they were not recommended for antiviral therapy according to Chinese Guidelines (2019). After TAF antiviral therapy, the rates of patients who achieved HBV DNA <20 IU/mL at 4, 12 and 24 weeks were 77.1%, 96.7% and 96.8% respectively. Among them, the undetectable rates of HBV DNA in patients with low baseline viral load at 4, 12 and 24 weeks were 92.3%, 100% and 100%, while the rates of those with high baseline viral load were 68.2%, 94.1% and 94.4%. Compared with 71.4%, 94.4% and 94.7% in the high baseline group, the undetectable rates of HBV DNA at 4, 12 and 24 weeks in the low baseline liver stiffness group were 85.7%, 100% and 100%. There was no statistical significance among the above groups., Conclusions: CHB patients who had normal ALT and detectable HBV DNA and did not meet "CHB prevention guide (2019)", could achieve complete virological response in 24 weeks after antiviral treatment by TAF., Competing Interests: The authors have no conflict of interest related to this publication., (© 2022 Authors.)

To explore the characteristics of water-soluble inorganic ions (WSIIs) in PM 2.5 during the process of continuous improvement of air quality in Beijing in recent years, a continuous collection of PM 2.5 sample campaign was conducted in Beijing from 2017 to 2018. The PM 2.5 mass concentration and WSIIs were then determined. The results showed that the average concentration of PM 2.5 in Beijing was (77.1±52.1) μg ·m -3 , with the highest and lowest values during spring [(102.9±69.1) μg ·m -3 ]and summer [(54.7±19.9) μg ·m -3 ], respectively. The average concentration of WSIIs was (31.7±30.1) μg ·m -3 , accounting for 41.1% of the PM 2.5 mass, and the seasonal contributions were: autumn (45.9%) > summer (41.9%) > spring (39.9%) ≥ winter (39.2%). SNA was an important component of the WSIIs that accounted for 86.0%, 89.5%, 74.6%, and 73.0% of the total WSIIs during spring, summer, autumn, and winter, respectively. With an increase in temperature, the concentration of NO 3 - increased initially and then decreased, while the concentration of SO 4 2- increased. When the relative humidity was less than 90%, the concentrations of both NO 3 - and SO 4 2- increased with an increase in relative humidity. With the aggravation of pollution, the overall contribution of WSIIs in PM 2.5 increased significantly, and the evolution characteristics of different ions were different. Among them, the concentration and contribution of NO 3 - continued to increase, while the contributions of SO 4 2- and the ions from dust (Mg 2+ , Ca 2+ , and Na + ) decreased. During the observation period, the primary sources of WSIIs were secondary conversion, combustion source, and dust. The control of coal combustion and motor vehicles is critical to reduce the emission of WSIIs. The backward trajectory analysis showed that the air masses from the south and west of Beijing corresponded to the high PM 2.5 concentration and proportion of WSIIs, and the contribution of secondary ions was significant. However, the concentrations and proportions of the air masses from the northwest and north were relatively low, but the contribution of Ca 2+ was high.

To investigate the characteristics of carbonaceous species in PM 2.5 in Beijing after the implementation of the Action Plan for the Prevention and Control of Air Pollution, PM 2.5 was continuously sampled in the heavily polluted southern urban area of Beijing from December 2017 to December 2018. The characteristics of organic carbon (OC) and element carbon (EC) were then determined. The results showed that the annual concentrations of PM 2.5 , OC, and EC in Beijing varied in wide ranges of 4.2-366.3, 0.9-74.5, and 0.0-5.5 μg ·m -3 , respectively, and the average mass concentration were (77.1±52.1), (11.2±7.8), and (1.2±0.8) μg ·m -3 . Overall, the carbonaceous species (OC and EC) accounted for 16.1% of the PM 2.5 mass. The seasonal characteristics of the OC mass concentrations were: winter [(13.8±8.7) μg ·m -3 ] > spring [(12.7±9.6) μg ·m -3 ] > autumn [(11.8±6.2) μg ·m -3 ] > summer [(6.5±2.1) μg ·m -3 ]. The concentration of the EC during the four seasons was low, ranging from 0.8 to 1.5 μg ·m -3 . The annual average mass concentration and contribution of secondary organic carbon (SOC) were (5.4±5.8) μg ·m -3 and 48.2%, respectively, highlighting the significant contribution of the secondary process. With the aggravation of pollution, although the contribution proportion of OC and EC decreased, their mass concentrations during "heavily polluted" days were 6.3 and 3.2 times that of "excellent" days, respectively. Compare to non-heating period, the mass concentrations of PM 2.5 , OC, and SOC increased by 14.4%, 47.9%, and 72.1% in heating period, respectively, which emphasized the importance of carbonaceous species during heating periods. Potential source contribution function (PSCF) analysis showed that the southwest areas of Beijing (such as Shanxi and Henan province) were the main potential source areas of PM 2.5 and OC. The high value area of the PSCF of EC was less and the main potential source area was in the south of Beijing (such as Shandong and Henan province).

Size-resolved filter samples were collected in Taiyuan every other week from June 2012 to May 2014. The mass concentrations of water-soluble ions (Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , F - , Cl - , NO 3 - and SO 4 2- ) were measured by ion chromatography. The results showed that the total concentrations of measured water-soluble ions were (15.39±9.91), (21.10±15.49) and (36.34±18.51) μg·m -3 in PM 1.1 , PM 2.1 and PM 9 , respectively. In PM 1.1 and PM 2.1 , secondary water-soluble ions (SO 4 2- , NO 3 - and NH 4 + ) comprised 87.59% and 86.30% of all water-soluble ions, respectively, while in PM 9 , SO 4 2- and Ca 2+ comprised 32.78% and 28.54% of all water-soluble ions, respectively. SO 4 2- and NH 4 + had higher concentrations in winter and summer, and lower in spring and autumn. NO 3 - , K + and Cl - presented similar seasonal variation with a descending order of winter >autumn >spring >summer, and Ca 2+ and Mg 2+ followed the sequence of spring >winter >autumn >summer. SO 4 2- and NH 4 + showed a unimodal size distribution and the peak in the fine mode shifted from 0.43-0.65 μm in spring and autumn to 0.65-1.1 μm in summer. NO 3 - showed a bimodal size distribution. NO 3 - and NH 4 + were dominated by the fine mode peaking at 0.43-2.1 μm in winter, and NO 3 - was dominated by the coarse mode peaking at 4.7-5.8 μm in summer. K + , Na + and Cl - also showed a bimodal size distribution with the fine mode at 0.43-1.1 μm and the coarse mode at 4.7-5.8 μm. Ca 2+ , Mg 2+ and F - were unimodal with the peak in the coarse mode of 4.7-5.8 μm. On heavily polluted days, the mass concentrations of secondary water-soluble ions and Cl - accumulated, and secondary water-soluble ions were unimodal with the peak in the fine mode of 1.1-2.1 μm. However, on clear days, secondary water-soluble ions showed a bimodal size distribution with the fine mode at 0.43-0.65 μm and the coarse mode at 4.7-5.8 μm. The peak of secondary water-soluble ions in the fine mode shifted. PCA analysis showed that the sources of water-soluble ions were dominated by the secondary formation, coal combustion, industrial emission, biomass burning, and soil particles or falling dust.

In order to evaluate the effects of the implementation of emission reduction measures and the revolution of air quality of Beijing during APEC, the evolution characteristics of air quality was analyzed based on the hourly monitored readings of Olympic Sports Center from 1 to 15 November 2014 released by Environmental Monitoring Station of China, and compared with that in 2013. The results showed that: (1) PM₂.₅ was the main pollutant in Beijing. The air quality was good during the period of APEC with three obvious pollution events, and it was better than that in the same period in 2013, indicating that the implementation of emission reduction measures had made significant contribution to the improvement of air quality. (2) During the period of APEC, the concentrations of PM₂.₅ of 5 days were below the World Health Organization (WHO) standard (25 µg · m⁻³), and the concentration of SO₂ met the WHO standard during this time. (3) During the period of APEC, the ratio of PM₂.₅, and PM₁₀ was less than 0.5 when the air quality was good, and gradually increased with the increasing pollution level. The ratio reached 0.9 when the air was seriously polluted. (4) Compared with the same time in 2013, although the implementation of emission reduction measures made contribution to the reduction of the concentration of PM₂.₅, its contributions to the reduction of SO₂ and CO concentration were much more obvious than that of PM₂.₅, and it had little impact on the reduction of NO₂ concentration, and the reduction order of pollutants emission was SO₂ > CO > PM > NO₂, indicating that the sources, effects and emission reduction of PM₂.₅ were complex, and further studies are required.

Analysis on the revolution and regional characteristics of air quality by hourly monitored readings from 1 to 15 November 2014 released by Environmental Monitoring Station of China and research of the impacts of weather situation and meteorological elements released by China Meteorological Administration towards air quality of Beijing and its surrounding cities during the Asia-Pacific Economic Cooperation (APEC) indicated that: (1) The air quality was good because of the implementation of mitigation measures, while the Air Quality Index (AQI) increased along with the termination of mitigation measures. Thus it can be seen that mitigation measures made a great contribution to the improvement of air quality of Beijing and its surrounding cities. (2) Affected by thermal inversion layer, AQI of Beijing and its surrounding cities increased quickly during the initial of the implemental of reducing measures which proved that pollutants would accumulate in the context of unfavourable weather, hence the influence of weather situation towards air quality could not be ignored. (3) Although affected by thermal inversion layer, the concentration of pollutants of Beijing was not accumulated to a high degree at the end period of reducing measures, while Tianjin, Tangshan, Baoding and Xingtai suffered from moderate and severe pollution at the same time which further illustrated that the implementation of mitigation measures have made a great contribution to the improvement of air quality in Beijing during APEC.

Research on the differences of air quality index (AQI) especially AQI of particulate matters between China and America and analysis of hourly monitored readings from April to December in 2013 released by Environmental Monitoring Station of China indicated that: (1) Although China lagged behind America in formulating and publishing of AQI standards, the AQI standards published in 2012 in China covered more pollutant indexes than before and could objectively reflect the characteristics of air pollution in China, and were more close to the residens's feeling about air quality. (2) The methods adopted for calculation of particulate matter hourly AQI were different in China and America, and the comparison revealed that the calculation method adopted by China using the 24 h average concentration breakpoint of particulate matters to replace the 1 h average concentration breakpoint would enhance the severity of the pollution level. (3) The breakpoint of PM2.5 -24 h in China was less rigorous than that in America when AQI < 200, which led to the inconsistence between the ratio of PM2.5/PM10 and the real situation in China. (4) Analysis on the monitoring readings from station of Beijing Olympic Sports Center showed that when AQI < 50, the ratio of PM2.5/PM10 was less than 0.5 and increased with.the increasing of AQI. Correction and adjustment of particulate matter real-time calculation method and breakpoints of PM2.5 and PM10 were suggested in China.