Abstract:
The Ijen volcano has the Pleistocene age, and this stratovolcano was very acidic crater water with a pH of 0-1. The acidic
water seeps into the Banyupait River. Asembagus is a research area located on the northern slope of the Ijen volcano, and the Banyupait
River drains this. This study used several different analytic methodologies with some previous researchers, namely geological mapping,
pH measurement, spectrophotometry, IRMS (Isotope Ratio Mass Spectrometer), and the technique of Induced Coupled Mass
Spectrometry (ICP-MS). Besides, the petrographic analysis is used to determine rock minerals' composition due to rocks interacting
with acidic water. Banyupait River water in the Asembagus area has a pH of river water around 3-7.3, SO4 (220-683 ppm), and the type
of water is meteoric water. Also, Ca, K, and Mg concentrations in the west Banyupait river irrigation water flow showed higher levels
than the eastern. Likewise, REE elements from the Asembagus region showed lower concentrations compared to Ijen Crater water.
This change in the level of chemical elements is caused by the Banyupait River's acidity being diluted or mixed with water from other
water. The process of acidic water interaction with rocks can also be observed from rocks traversed by the Banyupait River flow.
Chalcedony and hematite replace the primary minerals of basaltic rocks. This research is expected to improve the quality of water
needed by the Asembagus community to live healthily.
