STUDI AIR TANAH PADA AREA SEMBURAN LUMPUR LAPINDO SIDOARJO MENGGUNAKAN ISOTOP ALAM

Abstract

Groundwater  age  study  has  been  carried  out  on  mud  eruption  area  in  Sidoarjo  using  natural  isotopes.  The  study  was  done  in  2007  and  2009  by  analyzing  water  samples  from  mud  eruption area.  The  aim  of  the  study  was  to  identify  water  characteristics  which  seeped  out  from  the  mud eruption  area.  Origins  of  the  water  can  be  fossil  water,  groundwater,  or  sea  water.  The ¹⁸O,  ²H,  and d²H data, which were plotted together with d¹⁸O data of the water samples of 2007 (LUSI-1 and LUSI-2), showed that water from the center of mud eruption area had interacted with magmatic materials. Whereas, the  water  from  LUSI-3  location  which  was  collected  about  300  m  distance  from  the  center  of  mud  eruption area had an age of more than 40,000 years, which contained ¹³C, ¹⁸O, and ²H of 1.58^o/_oo, 5.28^o/_oo, and -17.5^o/_oo respectively. This matter indicated that the water was sea water fossil which interacted with magmatic materials. The water in LUSI-4 location had an age of 18,408 years, which contained ¹³C, ¹⁸O, and ²H of -10.5^o/_oo, 7.68^o/_oo, and -35.3^o/_oo respectively. These data indicated that the water was fresh water, which was not mixed with water from mud. The water age from LUSI-5 location was 14,237 years, and contained ¹³C, ¹⁸O, and ²H of -3.00^o/_oo, -0.25^o/_oo, and -21.1^o/_oo respectively. These data showed that the water was partially originated from the groundwater and dominated by mud water. The water age at MVKA location was 14,355 years, and contained ¹³C, ¹⁸O, and ²H of 2^o/_oo, 2.61^o/_oo, and -6.6^o/_oo respectively. This water was estimated as a mixture of mud water and intruded sea water. Plots of ¹⁸O, ²H, d²H and d¹⁸O, ¹⁴C data of water samples of 2009 showed that the water was dominated by groundwater, but the water from LUSI-11 sample was indicated as sea water.