GROUNDWATER FLUORIDE HAZARD ZONATION IN THE VOLCANOGENIC POLLUTED AREA, EAST JAVA, INDONESIA

Volcanic activity can release numerous hazardous pollutants, including toxic elements such as fluoride. Despite the relevance of fluorine to human nutrition, the ingestion of excessive doses can have adverse health effects such as fluorosis disease. Asembagus, Banyuputih, and Jangkar (ABJ) subdistricts in East Java, Indonesia, have been polluted by fluoride from the effluent of Kawah Ijen volcano crater-lake water. To prevent and mitigate the severe chronic effects of prolonged exposure to fluoride, a hazard zonation of the polluted area was developed. A spatial multi-criteria evaluation (SMCE) approach was applied to visualize the fluoride hazard zones based on the intrinsic properties of acid-neutral drainage distance factors. The spatial hazard model with 5x5 m(2) grid resolution showed that 15% of the area was in the very low zone, 22% in the low zone, 49% in the moderate zone, 7% in the high zone, and 7% in the very high zone, respectively. The moderate zone was associated with acid irrigation networks that watered paddy fields only during the dry season, and its contribution and mechanism of transport to groundwater fluoride pollution were still unclear. The cross-operation technique also revealed that six villages were in the high hazard zone with potential for dental fluorosis, and five villages were in the very high hazard zone with the potential for skeletal fluorosis chronic effect. Based on the condition of the drinking water source, the optimization of clean water networks and groundwater quality improvement following drinking water standards is needed. Risk communication about fluoride hazard zones should also be addressed in Asembagus, Banyuputih, and Jangkar subdistricts to reduce and mitigate long-term health effects.