Distribution and sea-to-air fluxes of volatile halocarbons in the Bohai Sea and North Yellow Sea during spring.

Concentrations of volatile halocarbons (VHCs), such as CHBr2Cl, CHBr3, C2HCl3, and C2Cl4, in the Bohai Sea (BS) and North Yellow Sea (NYS) were measured during the spring of 2014. The VHC concentrations varied widely and decreased with distance from the coast in the investigated area, with low values observed in the open sea. Depth profiles of the VHCs were characterized by the highest concentration generally found in the upper water column. The distributions of the VHCs in the BS and NYS were clearly influenced by the combined effects of biological production, anthropogenic activities, and riverine input. The sea-to-air fluxes of CHBr2Cl, CHBr3, C2HCl3, and C2Cl4 in the study area were estimated to be 47.17, 56.63, 162.56, and 104.37nmolm-2d-1, respectively, indicating that the investigated area may be a source of atmospheric CHBr2Cl, CHBr3, C2HCl3, and C2Cl4 in spring.

Effect analysis of topical fluoride varnish on caries prevention of first permanent molars in school-age children / 口腔疾病防治

Objective @#To investigate the effectiveness of fluoride varnish in preventing first permanent molars caries inschool-age children and provide necessary information for oral health instruction. @*Methods@#378 children aged 6-7 years old in the first grade of primary school in dahua country, hechi city, Guangxi province (1 053 first permanent molars) were randomly recruited into 2 groups. The test group (542 first permanent molars in 191 children) was treated with fluoride varnish one time in a half year and given oral hygiene instruction 3 times; The control group (511 first permanent molars in 187 children) was only given oral hygiene instruction 3 times. All first permanent molars were checked after 18 months later for caries. @*Results@#After intervention, the caries prevalence rate in the test group raised from 21.99% to 27.75% compared with the control group from 24.60% to 37.43%. The caries incidence rate in test and control group was 5.76% and 12.83% respectively. There was a significant difference between 2 groups regardless of caries prevalence, caries incidence, the DMFT reduction, the DMFs reduction, the occlusal caries prevalence, the pit and fissure caries prevalence, the proximal caries prevalence. @*Conclusion @#Semi-annual application of fluoride varnish is effective in the prevention of dental caries in first permanent molars , which was worth of being popularized in clinic.