The levels of fluorine in sediment cores obtained from Changyi County (PZ core) and Laizhou County (TS core) are used to discuss the fluorine sources in groundwater and its enrichment dynamics. The sediments in the aquifer are mainly constituted of granite gravels. The levels of fluorine in the PZ and TS cores range from 130 to 468 mg/kg, 139–528 mg/kg, with average values of 324, 348 mg/kg, respectively, which show relatively lower levels than the national average of fluorine in the soil or sediment. Thus, the fluorosis in this area should not be attributed to the levels of fluorine in sediments. The average fluorine concentrations in the aquifer from top to bottom are 154, 139, 200, 222 mg/kg for the TS core, and 154, 130, 266, 272 mg/kg for the PZ core, respectively, which are the lowest of the cores and extremely lower levels than the fresh granites. Such a fact indicates that a vast amount of fluorine has been leached into the groundwater. Moreover, the fluorine leachability is estimated to be approximately 70 %, although the previous documents showed fluorine contents of the granite surrounding Laizhou Bay were almost equal to or even lower than the average levels of fluorine in fresh granites. Meanwhile, a simulation experiment also reveals that fluorine release from rocks increases with the addition of seawater and brine water. Therefore, the seawater intrusion may potentially enhance the fluorine leachability, and should be an important dynamic of fluorine enrichment.

The Three Rivers Source Region of the Qinghai-Tibet Plateau is a key area that has extensive impacts on much of the population and economy of China as well as several Southeast Asian countries. The rangeland in this area has undergone degradation, the driving factors of which have been extensively investigated in previous studies. However, the effect of policy on rangeland was not analyzed by subdividing the study period according to the timing of the rangeland policies. The role of dry conditions during the process of degradation has not been studied. Therefore, the period from 1984 to 2009 was subdivided into five periods according to the timing of the relevant government policies based on long-term field investigation. The mean annual normalized difference vegetation index (NDVI) and its relationship to dry conditions, policy, temperature, precipitation, and moisture index were analyzed for the five periods. According to our analysis, dry conditions mainly occurred in non-vegetation-growing months, and they did not affect the status of the rangeland. The privatization of rangeland and livestock caused the number of livestock to increase, resulting in a decrease in the mean annual NDVI from 1984 to 1993. The policies of “Green-to-Grain” and eco-migration caused livestock numbers to decrease and the NDVI to increase after 1994. Physical factors such as temperature, precipitation, and moisture also affected the status of the rangeland. Increased temperature had positive effects on rangeland in most areas, but its effect was offset by increased numbers of livestock from 1984 to 1993. Precipitation had positive effects only in drier areas in which the precipitation in the vegetation-growing months was less than 400 mm. In general, the policies of “Green-to-Grain” and eco-migration improved the status of rangeland, and helped improve sustainable use of the rangeland. The methods used in this study could be applied to other case studies of rangeland. Governments should continue to implement compensation policies to maintain the improved condition of rangeland in the area and expand those policies to other rangeland areas.