Hydrogeochemical and Isotopic Investigations on the Origins of Groundwater Salinization in Çarşamba Coastal Aquifer (North Turkey)

The aim of this study is to determine the origins of salinization and the main hydrogeochemical process that controls the chemistry of Çarşamba coastal aquifer in Turkey. Therefore, a total of 33 groundwater samples and three seawater samples were analyzed in the coastal region of Çarşamba Plain in July 2019 and for these samples’ physical parameters, major ions and environmental isotopes (δ18O, δ2H and 3H) values were determined. Piper, Chadha, Gibbs diagrams and Stuyfzand Classification Systems were used to determine the origins of salinization and the key hydrogeochemical process controlling the groundwater chemistry. According to Stuyfzand classification system, the study showed that the freshwater and fresh-brackish water main types are the most widespread in the study area. Six water subtypes were observed in the study area that include CaHCO3, CaMix, NaMix, NaCl, NaHCO3 and MgHCO3. In addition, the subtypes CaMix indicated the locations of the transition zone, where the groundwater rich in Ca and HCO3 and gradually enriched in Na changes from CaMix with HCO3 as dominant anion to eventually CaCl and NaCl subtypes. Furthermore, the subtypes NaMix, NaHCO3 and MgHCO3 showed the locations of the transition zone where the flushing of the saline aquifer by freshwater takes place. All groundwater samples from study area had a positive cation exchange code and show that four hydrogeochemical facies composed of CaHCO3; Ca-Mg-Cl and NaCl and NaHCO3. Besides, groundwater samples have been influenced by two main mechanisms: the water-rock interaction and evaporation-crystallization. According to δ18O, δ2H and 3H analysis, the water samples have meteoric origin, shallow circulation, and a short residence time.

Structural features and formation processes of a complex hydrogeochemical section in the Baikal rift zone

The purpose of the work is to study the effect of organic matter on the formation of ion-salt and gas composition of nitrogen-methane and methane thermal water occurring in the sedimentary rocks of deep horizons of artesian basins. The object of research is the Tunka intermountain artesian basin of the Baikal rift zone and the Tungor gas and oil field of the Okhotsk-Sakhalin basin, in the deep horizons of which soda (inversion) low- and high-mineralized groundwater is common. The study combines the results of the traditional study of the composition of natural solutions and the quantitative research of physical and chemical interactions in the “water – rock” system conducted using the Selector software package according to the degree of the hydrogeochemical process, which was set by the value of the rock/water ratio. Chemically pure water and rocks of medium chemical composition were used in interaction. With the use of physicochemical modeling the formation of thermal water composition in sedimentary rocks depending on the interaction degree between water and rock and the amount of organic matter was unravelled. As a result, it was determined that the organic matter present in the rock has the dominant influence on the intensity of the hydrogeochemical process determining the amount of mineralization, the ratio of components, and the amount of methane, nitrogen, and carbon dioxide produced. The correspondent compositions of the model and natural solutions showed the possibility to form low- and high-mineralized sodium bicarbonate groundwater of different gas-saturation degree in the conditions of deep horizons of sedimentary basins due to the internal reserves of the “water – rock” system not involving any components from external sources.

IMPROVEMENT OF ENVIRONMENTALLY SAFE RINSING OF SALTED LANDS TECHNOLOGY

The theoretical justification of the environmentally friendly saline leaching technology is based on a model of the evolutionary hydrogeochemical process of the natural system, which describes mass transfer in sedimentary formations during geological time, where it occurs via the molecular diffusion mechanism through the aqueous phase, namely, a portion of the dissolved salts is removed from the soil layer proportional to the amount of their solid phase enclosed within this layer. To implement the developed flushing method, saline soil flushing technologies are proposed in practice, where the water supply to the check with a furrow is regulated by feeding it to the checks in pressure mode until it is completely moistened, and then the water supply is reduced to work in a non-pressure mode, i.e. water flow rate the check is reduced until it is equal to the filtration coefficient of the soil. Moreover, the developed technology for washing saline soils based on the «soft» control of the hydrogeochemical process, which is based on the concept of the laws of natural evolutionary soil processes in the interpretation described above: the soil as an open system has stability, self-regulation and is in translational dynamic equilibrium. To implement in practice the developed methods and technology for flushing saline lands, the proposed methodology for determining the parameters of flushing technology with irrigation technique using furrows from two opposite outlet furrows of row crops, which allow to determine the irrigation time and predict the regime of soil moisture with high reliability and reliability.

HIDROGEOKIMIA AIRTANAH TIDAK TERTEKAN DI PESISIR BARAT KABUPATEN SERANG DAN PANDEGLANG, PROVINSI BANTEN

Proses hidrogeokimia terjadi karena interaksi antara airtanah dengan air laut. Proses tersebut akan mempengaruhi komposisi kimia di lingkungan pesisir. Untuk mengetahui seberapa jauh interaksi tersebut telah terjadi, dilakukan analisis tipe air berdasarkan jumlah anion dan kation yang paling dominan, dan analisis nisbah ion-ion utama. Pengambilan conto dilakukan di 38 lokasi conto air di pesisir barat Kabupaten Serang dan Pandeglang. Hasil penelitian menunjukkan tipe air didominasi oleh Ca(HCO3)2 55,26%, NaHCO3 39,47%, Ca(SO4)2 2,63% and NaMix 2,63%. Sementara hasil analisis nisbah ion utama Na+/Cl-, Ca2+/Mg2+, dan Ca2+/SO42- mengindikasikan bahwa telah terjadi pencemaran air laut di beberapa dataran alluvial pesisir Pandeglang. Pada sebagian besar pesisir barat Serang dan Pandeglang sedang terjadi proses pencemaran atau intrusi air laut. Occurrence of hydrogeochemical process is due to the interaction between groundwater and sea water. The process will affect the chemical composition in the coastal environment. To find out how far the interaction has taken place, the water type was analysed based on the amount of most dominant anion and cation, and also the major ions ratios. The samplings were conducted in 38 locations on the west coast of Serang and Pandeglang Regencies. Results showed that the water type was dominated by Ca(HCO3)2 55,26%, NaHCO3 39,47%, Ca(SO4)2 2,63% and NaMix 2,63%. While the results of major ion analysis of Na+/Cl-, Ca2+/Mg2+, and Ca2+/SO42- indicated that there has been the sea water pollution in some coastal alluvial plains of Pandeglang. In addition, the process of pollution or sea water intrusion has been occurring on most of the west coast of Serang and Pandeglang.

UPPER CATCHMENT OF BRIBIN UNDERGROUND RIVER HYDROGEOCHEMISTRY (GUNUNG SEWU KARST, GUNUNG KIDUL, JAVA, INDONESIA)

This research was conducted within Bribin underground river, the primary river in the Gunung Sewu karst area, Gunung Kidul, Java, Indonesia. The main purpose of this study is to describe hydrogeochemical processes that occur at the upstream of Bribin River. In addition, this study also differentiates hydrogeochemical dominant processes, which come about in rainy season and dry season. Study area boundary is the upper rainfall catchment of Bribin River that is focused on three locations: Pentung River (surface), Luweng Jomblangan, and Gilap Cave. Discharge measurements for one yearperiod are conducted to define discharge hydrograph. Furthermore, baseflow separation analysis is conducted to determine the percentage of base flow (PAD) throughout the year. Water sampling for hydrogeochemical analysis is taken everymonth to represent dry season and rainy season condition. To describe the hydrogeochemical processes, scatter plot analysis with small sample size is conducted. The result shows that within dry season, dominant hydrogeochemical process is water rock interaction that indicates by: achieving maximum level of Ca2+-HCO3- ; strong relationship between discharge increment and PAD reduction; strong relationship between increasing of Ca2+-HCO3- and increasing of PAD. In addition,strong relationship between the increase in Ca2+-HCO3- and reduction of carbondioxide in water as well as minimum level of carbondioxide gas in water at the peak of dry season, is also present. In rainy season, hydrogeochemical process shifted from water-rock interaction to dilution by precipitation as a result of rain water supply through conduit system channel,which is characterized by: declining in Ca2+-HCO3- when discharge increase; increasing Ca2+-HCO3- when discharge decrease; low correlation of spesific conductivity vs Ca2+-HCO3 -; low correlation of PAD vs Ca2+-HCO3 - when discharge increase, strong correlation between declining in PAD by increasing of CO2 in the water, and rising of CO2 when discharge increase.

AGRESIVITAS AIRTANAH KARST SUNGAI BAWAH TANAH BRIBIN, GUNUNG SEWU

Karst groundwater agressivity, which is here meant as the ability of water to dissolve limestone plays asignificant role to sustain the discharge of Bribin River. This article describes the spatial karst groundwateragressivity of Bribin underground river along flowpath. The boundary of analysis used in this research isthe tentative catchment area of Bribin River starting from Pentung River (swallow hole) as an inlet andBribin Cave as the end point (outlet).39 caves within the catchment were mapped, and 8 underground river were sampled and analyzed inlaboratory to achieve the chemical composition of groundwater including cation (Ca2+, Mg2+, Na+, K+) andanion (Cl-, SO4 2-, HCO3-). Afterwards, the result of laboratory is used to identify the chemical type of karst groundwater. Groundwater agressivity is subsequently classified by using chemical agressivity diagram in the system of pH – ToC – CaCO3 in order to account the ΔpH and ΔTAC. Finally, using the value of ΔpH and ΔTAC, the rate of karst groundwater agressivity may be defined. In addition, to define the stage of dissolution process along flowpath, analysis of Saturation Indices (SI) with respect to calcite (CaCO3) is also to be applied. The result indicates that there is a tendency of the decreasing rate of groundwater agressivity along flowpath. The inlet (Pentung River) characterized by high groundwater agressivity, and then there is a moderate decreasing trend of groundwater agressivity downstream. Finally, the rate of agressivity in the end point (Bribin Cave) confirms the low agressivity stage occurs. Furthermore, the analysis of SI values shows that the dominant hydrogeochemical process is calcite dissolution, even though this values is very close to equilibrium at Bribin Cave. Meanwhile, interesting phenomena present in Sodong Cave, where the sample is classified as aggressive water with the SI value of -0.43 inevitable that leakage ofBribin River may occur in the future.