Section of weathering crust developed on the biotite granite (ankroet complex), distributed on high leveling surfaces 1400–1700 m of Miocene age (N1) at Trai Mat area and around Da Lat city. In terms of petrographic characteristics, this weathered shell section is full of zones: laterite, litoma, saprolite, and the original stone. On chemical-mineral characteristics: The results of synchronous processing of the results of chemical, thermal and jealous analysis ... on vertical sections shows, they belong to the form of fealsit formation (FeAlSi) with 4 types of shells: Fealsit / goethite-kaolinite-gibsit (FeAlSi / gt-kl-gb / N1), AlSiferit / (kaolinite-hydromica) -gibsit-goethit (AlSiFe / (kl-hmi) -gb-gt / N1), Sialit (actually receptors) / kaolinite-hydromica (SiAl / kl-hmi / N1) and Sialit (alkaline) / kaolinite rock-forming minerals (SiAl / kvtđ-kl / N1-Q). About microelements: concentrate in VPH compared to original stone: Cu: 1.8 – 3.3 times, Pb: 1 – 2 times, Mo: 0 – 2.83 times, most other elements were removed from the shell. Related minerals: Camp Mat, Da Lat Kaolin can be used as raw material for producing white bone tiles and birth materials. In this weathered shell section, there is a weathered shell of AlSiferite / (kaolinite-hydromica) -gibsit-goethite (AlSiFe / (kl-hmi) -gb-gt) which is a weathered clay-rich weathering product (gibsit up to 30 - 40%), developing on biotite granite at Mat camp - Da Lat area is often seen only in basalt weathering crust which is very rare in granite.
Dental fluorosis-a major, but preventable, oral diseases and public oral health problems-related with exceeded the fluoride level in natural groundwater sources. Dental fluorosis remains as a major public health problem worldwide, including Vietnam. Previous studies carried out since the 2000s demonstrated a link between dental fluorosis and increased fluoride levels in drinking water of Ninh Hoa town, Khanh Hoa province. The aim of this study was to determine the temporal variation of district's population, who at risk for dental caries or dental fluorosis, with questionair survey in Ninh Hoa town. The results indicated that the rate of population at risk for dental fluorosis, has been decreased in comparision with previous studies. In especially, in the vulnerable area with high fluorid zones like Ninh Xuan, Ninh Phung wards (> 6mg/L), the number of population at risk decreases to only 18 and 12%, respectively. Overall, only 25% district's population were risk of potential dental fluorosis. It is the results from implementation of drinking water supply projects from government. However, the long-term operation of the replacement of groundwater project need to be further strengthened. In addition, a further study on dental fluorosis and sources of F should be carried out.
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