STUDY OF RADON-222 GAS, DISSOLVED RADON-222, AND DISSOLVED RARE ELEMENT IN LEMBANG AREA

• Main Author: ASHURI NIM : 22714301, WIJAYANTI
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31597
• Institution: Institut Teknologi Bandung

<p align="justify">This research was conducted in Lembang area, covering the west region of Lembang Fault and south region of Mount Tangkuban Perahu. The objectives of this study are to know the anomaly of dissolved Radon-222 and Radon-222 in soil gas, to analyze fault seal behavior of Lembang Fault based on isotope Radon-222 and hydrogeochemical data, and to investigate the groundwater origin of the study area. <br /> <br /> <br /> The data were taken from in situ measurements and laboratory analysis of hot and cold spring samples. For in situ measurements, data were collected using intelligent meter, Rad7, and Rad H2O. Meanwhile, laboratory analysis was conducted by using ion chromatography, inductively coupled plasma mass spectrometry, and gas chromatography. The research objects were two hot springs (KNCH and MBY1), 15 cold springs, and 26 point measurements of Radon-222 in soil gas. These data were then analyzed to determine water type, concentration trend of dissolved Radon-222, Radon-222 in soil gas, and dissolved rare elements, Lithium, Boron, and Fluorine. <br /> <br /> <br /> Based on the pattern of concentration distribution of dissolved Radon-222 and dissolved rare elements that can be transported by groundwater, the concentration distribution for both components in the northern and southern part of the Lembang Fault escarpment are distinctly different. This circumstance indicates that Lembang Fault acts as a barrier for groundwater flow. The concentration of Radon-222 in soil gas is increasing as it approaches the Lembang Fault. It indicates that the fractures formed along Lembang Fault act as a pathway of Radon-222 gas. <br /> <br /> <br /> Based on its water type and distance to the Mount Tangkuban Perahu, KNCH hot springs are classified as outflow zones from Mount Tangkuban Perahu. By considering the Cl/B ratio, KNCH (1069.02) and MBY1 (31.28) ratios are very different. This indicates that the CHD and MBY1 springs are not derived from the same reservoir. The water type of MBY1 hot spring is Bicarbonate that may be formed by the condensation of steam (rich in CO2) beneath the groundwater surface. In addition to the multiple reservoirs of KNCH and MBY1, it is suspected that KNCH and MBY1 hot springs derive from different heat sources. The water types of cold springs in the southern KNCH (CII, KVS, PDB, and KPG) are Chloride and Chloride-Sulphate, indicating the influence of KNCH hot springs in the four cold springs. Coupled with water type result, dissolved rare elements concentration in cold water of the southern KNCH also implies the hot springs influence in cold springs. <br /> <br /> <br /> Bicarbonate water in JYGR, GOM, BKN, GB1, GB2, GB3, GB5, MNH, DGG, MBY2, and MBY3 cold springs are possibly formed due to the reaction between meteoric water and carbon dioxide (from the atmosphere). From the 11 cold springs, there are two springs relatively in close relation to MBY1: MBY2 and MBY3. Unlike the cold spring in the south of KNCH (CII, KVS, PDB, and KPG), MBY1 hot spring does not affect the chemical content in MBY2 and MBY3 cold springs. It was likely that the aquifer that constitutes the MBY1 hot spring is not in continuity with the aquifer of MBY2 and MBY3 cold springs. <br /> <br /> <br /> The conclusion of this study is that the dissolved Radon-222 has a relatively high value (average = 32,856 Bq / m3) in the northwestern part of study area (volcanicrelated), compared with the surrounding of Lembang Fault (average = 8,044 Bq / m3). Radon-222 in soil gas has relatively high value near Lembang Fault (average = 35.840 Bq / m3) compared with the northwest part of the study area (average = 20,360 Bq / m3). The comparison of dissolved Radon-222, Radon-222 in soil gas, and dissolved rare element content shows that Lembang Fault is a boundary of groundwater flow between the south and north of this fault. The fractures around Lembang Fault act as pathways of Radon-222 gas to near surface. The appearance of Li, F, B, and Cl elements in cold springs, in the southern and western parts of the study area, is due to the influence of volcanic activity. There are two groups of cold and hot spring origin: volcano-related and non-volcano-related. The heat sources between KNCH and MBY1 hot springs are different.<p align="justify"> <br />