KAJIAN HIDROGEOKIMIA BERDASARKAN ANION DAN KATION UTAMA PADA AIRTANAH DANGKAL DI KABUPATEN TANGERANG

• Main Author: Indriyani, Neni
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70593
• Institution: Institut Teknologi Bandung

The research area covers the whole area of Tangerang Regency, which is about 111 km2. The objective of this research is to know the distribution of shallow groundwater facies and its relation with geological setting and source of anion-cation in groundwater. Based on log bor analysis in the research area, the aquifer is formed by sandstones and volcanic rocks (tuff), whereas aquitard is by sandy clay. Dug well and graphic cross sections show that the concentrations of the main anions and cations in the central part are lower than in the west-northeast and south-north, because local groundwater flow does not allow replacement and ion enrichment in the areas. Meanwhile, the result of Piper diagram analysis shows that the groundwater hydrogeochemistry consists of HCO3, HCO3-Cl-SO4, Cl-SO4-HCO3, Ca-Na, Na-Ca and Na-K facies. The HCO3, HCO3-Cl-SO4, Cl-SO4-HCO3 facies are the results of direct contact of groundwater with CO2 in soil zone, reaction of water with sedimentary rocks, pollution by human activity, yielding SO4, and reaction of water with clay in reducing condition, causing Cl replacement and ion exchange. Meanwhile, Ca-Na, Na-Ca and Na-K facies are the results of reaction of water with clay, yielding Ca and Na, reaction of water with sandstone containing plagioclase, yielding Ca and Na, and reaction of water with sandstone containing K-Felspar, yielding K. There are Na+K, Cl and TDS anomalies at point SG-25, which indicate that the groundwater is on sea water - fresh water interface, may cause mixing. It may also be caused by regional groundwater flow from the southern part, where the elevation is higher.