Hydrogeochemical analysis of groundwater in residential areas around the Terjun landfill in Medan city, Indonesia

Open dumping is the type of landfill used in Terjun landfill. This type of landfill has a high potential for pollution to the environment, especially in groundwater quality. This study aims to determine the quality of groundwater in the Terjun landfill area and its hydrogeochemistry. The methods proposed in this research are Trilinear Piper Diagram Analysis (1944), Stiff Quadrangle Diagram Analysis (1951) and Durov Diagram Analysis (1948). The elements analyzed include Calcium (Ca 2+ ), Sodium (Na + ), Magnesium (Mg 2+ ), Potassium (K + ), Chloride (Cl - ), Bicarbonate (HCO 3 - ) and Sulfate (SO 4 2- ). The results obtained on the electrical conductivity value ranged from 100-1100 micromhos/cm, indicating the classification of the water as fresh water. Analysis of the major ion test results of each sample using the three methods shows that the dominant ion content in the borehole groundwater is Cl- ions in borehole 1 and HCO3- ions in the other boreholes. On the Piper diagram, it can be determined that the facies or type of borehole groundwater that has been tested is Ca2+-HCO3-. Then the Durov diagram can be divided into 2 groups, namely the simple dissolution or mixing and reverse ion exchange groups. When looking at the results of the major ion test, sample point 1 has a high level of Cl- ions influenced by leachate water and a fairly close distance to the landfill.