KARAKTERISTIK DAN DISTRIBUSI LUMPUR SIDOARJO SEPANJANG SUNGAI, ESTUARI DAN PERAIRAN PORONG

Semburan lumpur Sidoarjo (Lusi) di daerah Porong menambah fungsi Sungai Porong menjadi sarana untuk mengalirkan lumpur ke arah laut, karena kemampuan tanggul – tanggul penghalang di sekitar lokasi semburan sangat terbatas. Kondisi ini berdampak pula terhadap terbawanya lumpur lapindo ke perairan Porong. Penelitian ini bermaksud untuk mengetahui sebaran sedimen di sungai, muara dan perairan sekitar Porong terutama yang bersumber dari luapan lumpur Sidoarjo. Materi yang digunakan dalam penelitian ini adalah sebanyak 30 sampel sedimen hasil sampling yang diambil di lokasi sungai – muara sungai Porong dan 30 sampel sedimen permukaan dasar laut di perairan sekitar muara sungai Porong. Distribusi umum sebaran sedimen di perairan Porong menunjukkan sedimen lumpur ditemukan di pinggir sungai dan sedimen pasir ditemukan di bagian tengah sungai. Distribusi umum sedimen dasar perairan di sekitar muara Porong berupa pasir, lempung dan lempung lanau pasiran. Hasil analisis mikroskopik dan SEM menunjukkan bahwa sedimen yang berasal dari luapan lumpur Sidoarjo ditemukan di sepanjang aliran Sungai Porong sampai muara, namun belum ditemukan di perairan luar sekitar muara Porong. Sedimen Lusi yang sampai ke muara Porong berukuran butir sampai 2,5 mikron. Deskripsi megaskopis menunjukkan sedimen Lusi pasir - kerikil umumnya berbentuk pipih (halus– agak halus). Hasil SEM menunjukkan bahwa sedimen yang berasal dari lumpur Sidoarjo umumnya seragam dan didominasi berupa smectite. Berbeda dengan sedimen sungai, hasil SEM yang diperoleh dari sampel laut yang menunjukkan sedimennya beragam, berupa montmorilonite, kaolinite dan illite. Kata Kunci : Sedimen, Porong, lumpur Sidoarjo The Sidoarjo mudflow in the Porong area increases the functions of Porong River as media to drain the muds towards the sea, because the ability of embankments in the area as a barrier is very limited. This condition intends to determine the presence and distribution of sediment in rivers, estuaries and waters originating from the Lusi mudflow. The materials used in this study are the sediment sampling results as many as 30 samples taken from the river and off the river mouth and 30 samples of sea surface sediments in the surrounding waters. General distribution of sediments in the Porong River shows the form of mud sediments are generally found in the riverside and sandy sediment found in the middle of the river, while the distribution of sediments in waters Porong form of sand, clay and sandy silt clay. The results of microscopic and SEM analysis showed that the sediments derived from the Lusi mudflow found along Porong River till estuaries, but they have not reach surrounding water of Porong estuary. The Lusi sediment that reached the estuary Porong sized to 2.5 micron. General megascopic description show the shape of the Lusi sediment as sand-gravel is a flat-shaped (rounded - sub rounded). SEM results showed that the sediments derived from the Lusi is generally uniform and dominated by smectite. In contrast to stream sediments, the SEM results obtained from marine sediment samples show a variety of sediments, in the form of montmorillonite, caolinite and illite. Key words: Sediment, Porong, Sidoarjo, Mud Overflow (Lusi)