ANALYSIS OF ORGANIC CARBON FLUX IN THE GILAP CAVE, PONJONG SUB-DISTRICT, GUNUNG KIDUL DISTRICT, YOGYAKARTA, INDONESIA

Sutanto Trijuni Putro, Dr. Eko Haryono, M.Si,

2013 | Tesis | S2 Geografi

Penelitian ini dilaksanakan di Kecamatan Ponjong, Kabupaten Gunungkidul, yang merupakan bagian dari kawasan Karst Gunungsewu. Tujuan dari penelitian ini adalah: 1) mengetahui kandungan organic karbon di airtetesan, aliran sungai bawah tanah, dan sungai permukaan; 2) menganalisa persentase organic karbon di tetesan, sungai bawah tanah dan sungai permukaan; 3) menganalisa variasi musiman aliran organic karbon di daerah penelitian Serangkaian kerja dilakukan, mulai dari observasi, instalasi alat dan sampling, serta pemrosesan data dan analisa. Observasi permukaan dilakukan untuk memahami kondisi permukaan area penelitian. Sampel organic karbon dan air dari sinking stream, tetesan, sungai bawah tanah dan air hujan dilakukan setiap dua hari sekali selama satu bulan, mencakup akhir musim hujan dan awal musim kemarau. Ion utama, organic karbon, debit, pH, DHL, dan suhu sampel dikumpulkan selama pekerjaan lapangan. Hasil lapangan dianalisa menggunakan trend dan korelasi antar parameter. Hasil mengindikasikan bahwahasil rata-rata organic karbon di Jomblangan yang mewakili kondisi permukaan adalah 2266 mg/L (0,227 %), Sungai Bawah Tanah Gilap 3130 mg/L (0,314 %) dan air tetesan 2690 mg/L (0,27 %). Kesemuanya melebihi standar 5 mg/L sebagai batas untuk air minum. Sungai bawah tanah GIlap memiliki konsentrasi organic karbon tertinggi. Tingginya nilai tersebut dikarenakan oleh aktivitas fauna dan percampuran dengan organic karbon dari perkolasi melalui epikarst. Organic karbon memiliki korelasi positif dengan debit dan korelasi negative dengan SI dan pH. Saat musim hujan, debit meningkat, diikuti dengan organic karbon, kecuali untuk tetesan. Tetesan dipengaruhi oleh selang waktu perjalanan air dari permukaan menuju system bawah permukaan melalui epikarst.

This research was conducted in Ponjong Sub-District, Gunungkidul, which is the part of Gunungsewu Karst area. The objectives of this research are: 1) Assessing the organic carbon contained in the dripwater, underground river flow and the surface river; 2) Analyzed the percentage between organic carbon in Gilap Cave from the dripwater, underground river flow and the surface river (sinking stream); and 3) Analyzed the seasonal variety of organic carbon flux in research area. To achieve the objective, a series of works was conducted and prepare. From observation, equipment installation and sampling, and data processing and analysis. Surface observation was conducted to understand the surface condition of research area. Sample of organic carbon, water from sinking stream, dripwater in speleothem and rainwater pH was collected with 2 days interval for a month. The sampling schedule covered the end of rainy season and the beginning of dry season. Major ion concentration, organic carbon concentration, discharge, pH, EC, and temperature of sample were collected during the fieldwork. The result was analyzed using trend and correlation among each parameter. The result indicate that the average organic carbon concentration found in Jomblangan which represent the condition of the sinking stream was 2266 mg/L (0,227 %), Gilap River was 3130 mg/L (0,314 %) and dripwater 2690 mg/L (0,27 %). They was far exeed the standard of 5 mg/L of organic carbon for drinking water. The Gilap River has the highest organic carbon than dripwater and Jomblangan which represent the sinking stream condition. Based on previous study, surface river in north west direction from research area has 0,99% organic carbon. The high concentration in Gilap River because of the effect of fauna activity and the mixture/accumulation of organic carbon coming from percolation through the epikarst. Organic carbon had positive correlation with discharge and negative correlation with SI and pH. In rainy season where the discharge was higher, the organic carbon content was also high except for dripwater. Dripwater was influenced by the timelag of water travel from surface to subsurface through epikarst.

Kata Kunci : organic karbon, indeks kejenuhan (SI), conduit, rekahan, hidrogeokimia