Distribution of Acidic Condition of River Water from The Ijen Active Volcano Crater in Banyupait River Asembagus Situbondo, East Java']Java, Indonesia

The Ijen volcano was a Pleistocene volcano and is one of the stratovolcanoes which was active in East Java Province. This volcano erupts by magmatic and phreatic eruptions. This volcano has the largest natural lake in the world, measuring around 960 x 600 m. Embankments limited the morphology of the crater with heights between 2.145-2386 m. The lowest height of the western embankment was upstream from Banyupait River. The water volume of the crater lake of Ijen volcano is quite large and very acidic. The acidic water from the crater lake flows from upstream Banyupait River to the north to the lower direction of the Asembagus Situbondo area. The purpose of this research was to study the pH distribution of the Banyupait river flow from upstream to the coast. It was because that Banyupait river acid water was used by residents for daily life and agriculture. The methodology used in this research was conducting field survey and measurements. Field survey was carried out along the flow Asembagus river in Banyupait, which started from the village of Bantal to the river mouth in the Java Sea. In conducting a field survey pH measurements were also carried out from the river water of the Kali Banyupait. The observations showed that the river water upstream of Banyupait River had a pH of around 2-3, while the more towards the downstream the pH of the river water changed to an increase of around 34. The acidic water of this river experienced dilution from several rivers in its area. Whereas in river estuaries, the river water mixes with the sea, so water has a pH of 4.2. Because river water is acidic (low pH), no biota along the Banyupait river was found. Besides that, the other characteristics of river water are brown. Rocks exposed to the river flow will be reddis, experiencing iron oxide. It was due to the interaction process of acid river water with rocks. However, the river water was used by residents around the river for agriculture and daily necessities. Consequently, the health of the population around Bantal village was low.