76 dokomite samples, the water sample from 17 wells. and the sample of water sealing from the No.436 well were tested for trace elements Sr and Ba in Wumishan formation of Renqiu oil field. The dissolution and precipitation of minerals composed of these trace elements at different temperatures and under different pressures of CO2 were simulated using the PHREEQM, software. The distribution and migration of the trace elements were discussed. The result shows that the distribution of trace elements was controlled by the sedimentation environment and the post stage water-roek interaction. Minerals formed in a high energy envi ronment of subtidol zoDe have a high content of trace elements. The Sr, for examplel, may reach as high a 0.03%; While those formed in a low energy environment of suprallitoral zone have a low content of Sr, only 0.0028%. For the scaling, the content of Sr may be as high as 0.69% and that of Ba is 0.09%, much higher than that in rocks and in water of the oil field, indicating that there exists a strong condensation action in the scaling process.

Tongshan area, a part of the floodplain of the abandoned Huanghe River, is one of the popular ndemic fluorosis areas in East China. One of the reasons is high concentration of fluorine in shallow groundwater. Test results of 36 groundwater samples show that fluorine concentration in shallow groundwater is 0.18-6.7mg/L and 50% of the samples exceed the Chinese drinking water quality standard. There exists a significant negative correlation in content between Ca2+ and F-. The correlations between fluorine concentration and other cations (for example Na+, K+, Mg2+) are not significant. The content of dissolved fluorine from the flooding sediments of the Huanghe River that varying from 5.6mg/kg to 15.2mg/kg plays an important role in forming the high fluorine groundwater. Usually, the dissolved fluorine content in silt is much higher than that in silty clay and clay. According to the geological investigation fluorine content in deep groundwater (over 60m) is less than 1.0mg/L and suitable for drinking, so it is an effective measure to prevent endemic fluorosis by extracting deep groundwater in disease areas.