Assessment of shallow groundwater contamination on Pari Island, Indonesia

Freshwater on small islands is generally limited and relies on rainwater and groundwater. This study aimed to assess changes in shallow groundwa ter quality on Pari Island, Indonesia. Pari Island is a small island with an area of 41.32 ha and belongs to a monsoon climate. Also, being a residential island, it attracts many tourists. The approach was to assess the shallow groundwater quality of ten wells during the dry and wet seasons. Changes in water quality were evaluated using traditional hydrochemical analysis methods (Schoeller, Piper, and Gibbs diagrams) and ion ratios. Shallow groundwater quality in the study area showed different responses depending on the season. Therefore, each well responded differently to changes represented by changes in water quality. The change is controlled by various factors: evaporation (or water balance), geology, aquifer characteristics, tides, wind direction, and wave height. These factors trigger the fluctuation of groundwater and seawater interface, affecting the amount of rainwater and sea water transported to the freshwater aquifer layer. This water volume transported affects the process of rock weathering, dissolution, and dilution of contaminants in shallow groundwater.