Psycho-Chemical Characteristic of Groundwater Quality in Hard Rock and Alluvium Aquifers in Pangkalpinang City, Bangka Belitung Islands Province

Abstract The people of Pangkalpinang City generally use water sourced from groundwater and from the reservoirs of former tin mining excavations commonly called “Kolong.” However, the quality of the Kolong water used has a pH that tends to be acidic, while the groundwater quality has yet to be detected. In line with these problems, this study aims to analyze groundwater quality based on groundwater’s Psycho-Chemical properties associated with the lithology distribution in the study location. There are 3 rock units in the research location: the phyllite rock unit, classified as hard rock, sandstone unit, and alluvium unit. The results obtained in the comparison of Psycho-Chemical parameters of groundwater based on lithology spread over 98 observation wells are in the phyllite rock unit; there are 9 observation wells with pH 4.67-6.26; EC 72-291 μS/cm; and TDS 38-142 mg/L. The sandstone rock unit has 57 observation wells with pH 4.36-8.41, EC 36-5394 μS/cm, and TDS 17-2732 mg/L. The alluvium unit has 32 observation wells with pH 4.68-8.54, EC 32-12333 μS/cm, and TDS 16-6167 mg/L. A comparison of groundwater quality characteristics based on the physico-chemical properties of water with the distribution of lithology illustrates that the quality of groundwater in the phyllite rock unit has a low pH (acidic), so it must get treatment first to be suitable for use by the community as clean water. At the same time, the results of the analysis of groundwater Psycho-Chemical parameters for EC and TDS values in sandstone and alluvium units are in the Slightly Brackish and Brackish categories, where this can be caused by several factors, such as the possibility of contamination by salt water (geogenic) or contamination by human activities (anthropogenic) so that further research needs to be done to find out the source of groundwater pollution at the research site.