Geological mapping in Gua Musang and evaluation of seawater intrusion in shallow aquifer of Kemumin, Kota Bharu using integrated geophysical & geochemical methods

This study focus on geological mapping of Lojing, Gua Musang and evaluation of seawater intrusion in shallow aquifer of Kemumin, Kota Bharu that is located near the shoreline using integrated geophysical and geochemical methods. Geological map was produced on 1 : 25,000 scale by conducting traversing, field observation and petrographic study. Lithology mainly composed of mudstone, quartzite and alluvium unit in the study area. Meanwhile, seawater intrusion in shallow aquifers can pose serious issue as it can be considered as contamination of groundwater. Therefore, integrated approach is applied using Electrical Resistivity Imaging (ERI) method was used by using ABEM Terrameter LS of 200 meter line with 41 electrodes and 5 meter spacing to produce a 2D imaging of the subsurface using RES2DINV software. The aforementioned method than was integrated with in situ geochemical analysis to gather data with the parameters such as pH, temperature, salinity, turbidity, Total Dissolved Solids (TDS), Total Suspended Solids (TSS) and Electrical Conductivity (EC) and laboratory analysis such as Atomic Absorption Spectroscopy (AAS) and titration analysis in five well locations. A total of three survey line were conducted by applying Wenner, Schlumberger and Pole-dipole array. Based on resistivity profile, only two locations of survey line showing seawater intrusion at approximately 5 to 20 meter depth. Meanwhile, all the groundwater samples are safe to use as the graphical data was compared with the National Guideline of Raw Water Quality Standards by Ministry of Health Malaysia. From the chemical result, samples collected near the shoreline (AT1, AT3, AT7 and AT8) show high salinity value.