Characteristics of spatial distribution of water fluoride in Heze City, Shandong Province based on inverse distance weighted

Abstract

Objective To evaluate the inverse distance weighted(IDW) in revealing the characteristics of spatial distribution of water fluoride in Heze City,Shandong Province.Methods A geographic information system (GIS) database of water fluoride was established in Heze City of Shandong Province using the data of endemic fluorosis surveys collected by Endemic Disease Prevention Institute in Shandong Province during 2005-2007.IDW spatial interpolation was applied to predict the distribution of fluoride in drinking water in 139 towns of Heze City.Sensitivity and specificity were calculated.Results Mean water fluoride levels in 10 counties of Heze City were all higher than 1.0 mg,/L,and the water fluoride in Cao County,Juye,Mudan District and Juancheng were higher than 2.0 mg/L.Of all 139 townships of Heze City,129 were higher fluoride townships where fluoride was ＞ 1.0 mg/L,10 were lower fluoride townships(≤ 1.0 mg/L).IDW spatial interpolation showed that the water fluoride of most areas in Heze City were ＞ 1.0-2.0 mg/L.The areas with water fluoride of ＞ 2.0-3.0 mg/L were mainly located in eastern Juancheng,northern Mudan District,north-central Chengwu,central and southern Juye,southeastern part of Caoxian and eastern part of Shan Town.Regions of water fluoride ＞ 3.0 mg/L were mainly distributed in Xieji and Wanfeng towns of Juye County,Jishan town of Juancheng County,Sunlaojia town of Caoxian and Dusi town of Mudan County.The internal verification results showed that the sensitivity,specificity and overall accuracy rate of IDW used for predicting water fluoride content was 100.00％ (129/129),10.00％ (1/10) and 93.53％ (130/139),respectively.While the external verification results showed that the sensitivity,specificity and overall accuracy rate of IDW for predicting water fluoride content was 100.00％(31/31),11.11％(1/9) and 80.00％(32/40),respectively.Conclusion With the application of IDW interpolation,it is feasible to infer the overall spatial distribution based on the monitoring data,and to reveal the spatial characteristics of water fluoride in Heze City,Shandong Province. Key words: Fluoride;  Geographic information systems;  Spatial interpolation;  Endemic disease