Link for citation: Ilham Putra Adiyaksa, Savichev  O.G., Khvashchevskaya  A.A. Ecological and geochemical condition of groundwater in the region of the mud volcano in Sidoarjo (East Java province, Indonesia). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 3, рр. 51-60. In Rus.

Relevance. Since 2006, the world's largest mud volcano has been happening in the eastern part of the island of Java (Indonesia), the province of East Java, the district of Sidoarjo. The surrounding areas are densely populated, which determines the constant need for high-quality drinking water. The lack of quality water is exacerbated by the influence of a mud volcano. The aim of the research is to assess the ecological and geochemical condition of groundwater in the area adjacent to the world's largest mud volcano in Sidoarjo (Indonesia, East Java province). Methods: methods for determining the chemical composition of groundwater, statistical methods, as well as mathematical modeling. Results and conclusions. The authors have obtained the preliminary assessment of the ecological and geochemical state of groundwater in the area of the mud volcano in Sidoarjo based on the results of a survey in January, February and October 2022. The result shows that groundwater in this area is assessed as: 1) freshwater with increased mineralization, bicarbonate calcium in areas outside the main direction of the slope of the earth's surface and the movement of water masses from the west-southwest to the east-northeast, limitedly suitable for domestic and drinking use (water treatment is needed for water use); 2) brackish, sodium chloride, with high contents of Hg, I, Br, B, not suitable for household and drinking use. Elevated concentrations of Na⁺, Cl^–, I, Br, B presumably testify to the participation of marine waters in the formation of the fluid composition of the mud volcano. The genesis of Hg requires more detailed study, and, possibly, is associated with local features. In general, the most objective indicator of the impact on the state of a mud volcano is Cl^– content. Recommendations are given for further hydrogeochemical studies in Sidoarjo.