[Nonlinear Response Relationship Between Ozone and Precursor Emissions in the Pearl River Delta Region Under Different Transmission Channels].

With the rapid development of urbanization, ozone (O3) pollution is an ongoing occurrence in the Pearl River Delta (PRD) region in China. The effective control of O3 pollution is a great challenge owing to the nonlinear relationship between O3 and precursor emissions and the effect of meteorological conditions. Based on the regional air quality model CAMx-OSAT (ozone source apportionment technology), O3 formation regimes were determined, and inter-city transportation across PRD was quantified under different transmission channels. The results showed that spatial differences were observed for the O3 formation regimes under different transmission channels. The VOCs-sensitive regime was mainly located in the central areas of the PRD region, and the NOx-sensitive regime was distributed in the suburban areas of the PRD regions under calm wind conditions. When the northeast wind was prevailing, the polluted air mass of the urban agglomeration was transmitted southwesterly downward, resulting in the downwind areas being transformed to VOCs-sensitive; the upwind areas were still NOx-sensitive. Under the southeast wind, the VOCs-sensitive regime had a banding distribution along the southeast-northwest direction, and the remaining areas were NOx-sensitive. With the influence of transmission channels, downwind cities were significantly affected by the transmission of upwind urban agglomerations (41%-87%), whereas the local formation was the main contributor under the calm wind conditions (60%-87%). To explore the relationship between O3 and precursor emissions, a series of sensitivity tests were designed. The results showed that maximized areas (20%-36%) with reductions in O3 can be achieved by reducing VOCs and NOx in the corresponding sensitive regimes, and the maximized level with the reduction in O3 can be fulfilled by reducing VOCs in the VOCs-sensitive regime. For the typical city Jiangmen, the area that met the standard increased the most under the calm wind (11%) and southeast wind (8%) conditions when VOCs and NOx were reduced in the corresponding sensitive regimes. Additionally, under northeast wind conditions, reducing VOCs in the VOCs-sensitive regime can more effectively control O3, as the area up to the standard increased by 140%.

[Characteristics and Meteorological Factors of Complex Nonattainment Pollution of Atmospheric Photochemical Oxidant (Ox) and PM2.5 in the Pearl River Delta Region, China].

Based on the atmospheric pollutant data from twelve monitoring sites in the Guangdong-Hong Kong-Macao Pearl River Delta Regional Air Quality Monitoring Network, the mass concentration trends of atmospheric photochemical oxidants (Ox, NO2+O3) and PM2.5 during 2013-2017 were studied. The complex nonattainment pollution of Ox and PM2.5 is defined as the daily average mass concentration of NO2 and PM2.5 and daily maximum 8 h average (O3 MDA8) mass concentration of O3 simultaneously that exceeds the Chinese grade Ⅱ national air quality standard. The characteristics and meteorological factors that influence the complex nonattainment pollution of Ox and PM2.5 at different types of areas were analyzed. The results indicate that from 2013 to 2017, the annual average mass concentration of PM2.5 in the Pearl River Delta (PRD) region decreased from (44±7) µg·m-3 to (32±4) µg·m-3, which met the annual standard for three consecutive years. The annual average mass concentration of Ox decreased from (127±14) µg·m-3 in 2013 to (114±12) µg·m-3 in 2016 and then showed a general rebound trend to (129±13) µg·m-3 in 2017 when O3 concentrations increased significantly (10 µg·m-3). The proportion of pollution processes with O3 as the primary pollutant increased from 33% in 2013 to 78% in 2017, and the regional characteristics of simultaneous pollution in multiple cities have been highlighted. The complex nonattainment pollution of Ox and PM2.5 occurred 60 times during the study period, primarily in urban sites (78%) and suburban sites (22%). The largest number of days of complex nonattainment pollution occurred in autumn (52%) because of strong solar radiation that was conducive to ozone formation, and consequently, the high oxidization of the atmosphere promoted the secondary generation of PM2.5. The weather conditions that caused the complex nonattainment pollution in the PRD mainly include outflow-high-pressures (43%), subtropical-high-pressures(30%), and tropical-depressions (27%). In terms of specific meteorological conditions, when the temperature was in the range of 20-25℃ and relative humidity was in the range of 60%-75%, the proportion of complex nonattainment pollution was the highest (22%). When O3 pollution was substantial, the high relative humidity and low wind speed during the nighttime caused the concentration of NO2 and PM2.5 to rise significantly, and then the high temperatures during the day aggravated the complex nonattainment pollution.

[Effect of oral rinse with Turkish gall on the clinical periodontal parameters and halitosis].

OBJECTIVE: To assess the effect of traditional Chinese medicine, oral rinse of Turkish gall (extracts from Turkish gall) on periodontal and halitosis parameters. METHODS: This single-blinded randomized controlled trial recruited 70 patients with gingivitis or mild to moderate chronic periodontitis. All the patients received the same professional oral hygiene instruction and using toothbrush and fluoride-only paste with same brand and size dispatched by the investigator from baseline to the end. The tested group by oral rinse of Turkish gall on the base of conventional oral hygiene, and control group with conventional oral hygiene only, were assigned randomly at baseline. Then periodontal parameters including Plaque index (PlI), Bleeding index (BI), Probing depth (PD) and Staining index (SI), halitosis index including volatile sulphur compounds (VSCs) by Halimeter, organoleptic score (OS), area of tongue coating (Ta), thickness of tongue coating (Tt), were measured at baseline and two-weeks after. RESULTS: After two weeks, all the periodontal parameters except for SI were significantly improved within each group (P<0.001). As compared to those in control group, the patients in tested group only exhibited significant improvement of PlI after two-week-use of oral rinse of Turkish gall (P<0.05). Though values of OS and Tt in tested group, OS only in control group, decreased significantly (P<0.05) respectively after two weeks, there were no statistical difference on the improvement of halitosis parameters. CONCLUSION: For untreated patients with gingivitis and periodontitis, oral rinse of Turkish gall displayed significant inhibition of dental plaque, while no predominated effect on halitosis when compared to correct conventional plaque control methods.