Geokimia Air Danau Gunung Kelimutu Flores, Nusa Tenggara Timur - Prettiina Sitinjak (Jurnal Lingkungan dan Bencana Geologi, 2012)
SARIGunung Kelimutu yang terletak di Pulau Flores, Nusa Tenggara Timur memiliki tiga buah danau kawah, yaitu danau Tiwu Nua Muri Kooh Fai, danau Tiwu Ata Polo dan danau Tiwu Ata Mbupu. Danau kawah tersebut sering berubah warna karena kandungan unsur kimia yang berbeda yang dapat juga dipengaruhi oleh aktivitas gunung api. Segitiga Cl-SO4-HCO3 menunjukkan air di lereng Gunung Kelimutu seperti air sungai Muru Keba, air panas Kolorongo, air panas Liasembe, air sungai Mboeli bertipe bikarbonat, sementara air panas Toba, air panas Jopu, air dingin Toba, air panas Mutu Loo, air panas Watugana, air panas Ae Lawa, dan air sungai Ae Mutu bertipe sulfat. Berdasarkan hasil analisis kimia diketahui bahwa komposisi kimia air dingin Toba yang mengalir di desa Roga lereng Gunung Kelimutu, memiliki pH: 3,21, suhu air: 26,20 C, dengan konsentrasi Fe: 0,51 ppm, air panas Toba memiliki pH: 2,30, suhu air 48,7°C, dengan konsentrasi Fe: 10,43 ppm, Cl: 311,61 ppm, SO4: 1.046,26 ppm, dan Fluorida: 12,89 ppm. Air sungai Ae Mutu di dusun Waturaka memiliki pH: 2,33, suhu air 19,2°C, konsentrasi Fe: 76,26 ppm, Cl: 1848,97 ppm, SO4: 3765,18 ppm, Fluorida: 15,43 ppm, dan Boron: 3,94 ppm. pH yang asam dengan tingginya konsentrasi Cl, SO4, Fe, Fluorida, Boron, dan gas CO2 berkisar 80.907,02 ppm menunjukkan kemungkinan aliran air sungai tersebut berasal dari celah-celah batuan dinding danau kawah atau kebocoran danau. Di lereng Barat Gunung Kelimutu di desa Waturaka muncul aktivitas vulkanik yang baru berupa pemunculan titik solfatara dan air panas. Suhu solfatara 96,4o C, suhu air panas 87,1o C, pH 6,80. Bila dibandingkan pengukuran suhu air tahun 2007 sebesar 90,4 o C dengan tahun 2011 sebesar 87,1o C menunjukkan adanya penurunan suhu air.Kata kunci: Kelimutu, danau kawah, mata air panas, solfatara, kebocoran, air sungai, mata air dinginABSTRACTMt. Kelimutu is located on Flores Island, East Nusa Tenggara has three crater lakes, namely Lake Tiwu Nua Muri Kooh Fai, Lake Tiwu Ata Polo, and Lake Tiwu Ata Mbupu. The colors of these crater lakes are changed oftenly because they have different chemical composition, moreover, it is also influenced by volcanic activity. The Cl-SO4-HCO3 triangle shows that the water found at Mount Kelimutu slope such as the Keba Muru river water, Kolorongo spring, Liasembe hotspring, Mboeli river water are of bicarbonate types, whereas Toba hotspring, Jopu hotspring, Toba spring, Loo hotspring, Watugana hotspring, Ae Lawa hotspring, and Ae Mutu river water are of sulfate types. Based on chemical analysis results it is known that the composition of Toba spring found at Roga village-Kelimutu flank has a pH of 3.21, the temperature is 26.2° C, with Fe concentration of 0.51 ppm, the Toba hotspring has a pH of 2.30, water temperature is Ae Mutu river water at Waturaka village has a pH of: 2.33, temperature of 19.20 C, concentration of Fe: 76.26 ppm, Cl: 1848.97 ppm, SO4: 3765.18 ppm, Fluoride: 15.43 ppm , and Boron: 3.94 ppm. The acid pH with its high concentrations of Cl, SO4, Fe, Fluoride, Boron, and CO2 gas which is about 80907.02 ppm, indicates that possibly the river water is originating from the cracks of the crater wall rock or leakage of the crater lake. At Waturaka village, in the west slope of Mt. Kelimutu there was a new volcanic activity appeared, in the form of solfatar and hot springs. The temperature of the solfatar is 96.4 ° C, the hot spring temperature is 87.10 C, and the pH is 6.80. When it is compared, the water temperature measurement in 2007 which was 90.40 C with the year 2011 which was 87.10 C showed that there was a decrease in water temperature.Keywords: Kelimutu, crater lake, hot springs, solfatar, leakage, river water, spring water