Distribusi Fe, Al, Dan Si Oksida Pada Beberapa

RATNA KNAUSYARI HARWANTI. Distribution of Fe, Al, and Si Oxide in
Several Soils &om Different Parent Rocks in Karangsambung, Kebumen, Central
Java. Supervised by WIDIATMAKA and ISKANDAR.
Karangsambung is a nature geological laboratory where there were found
several rocks in a different surface environment. This place is a location where
slab ocean Indies-Australia and Eurasia continental plates met. Various rocks are
possible to form various type of soil.
This research was aimed to study about Fe, A1 and Si oxide in several soils
which develop from different parent rock materials and to study soil weathering
rate. Soil samples were collected in 6 locations from 3 rock materials that were :
igneous, sediment, and metamorphic rocks. Six soil profiles (PI to P6) was
established &om the parent material of diabase, phillyte, chert, marble, basalt and
shale. The contain of Fe, Al, and Si oxide in soil were extracted with dithionite
citrate bicarbonate, ammonium oxalate, and pyrophosphate methods.
The rate of Fed were 3.73-1.38%, &om the highest to lowest were P6 > P4
> P2 > P5 > PI > P3, Feo (0.5-0.15%) P1 > P6 > P2 > P4 > P3 z P5. All the
profiles have incline Sip> Alp > Fe,. Ratio Fe, Al, and Si oxide were different in
every soil. It is showing differentiation of oxide form. Profile which was
dominated by crystalline oxide were P2, P4, P5 dan P6, and profile which was
dominated by oxide arnorf were P 1 and P3.
There were not similar pattern in Fe, Al, or Si distribution between soil
profile in similar rocks (igneous, sediment, or metamorph). Based on the ratio
FedFed analysis, intensive weathering was occurred in profile P2, P4, P5 and P6.
According to the ratio of SiOz/FezO3 a analysis, intensive weathering was
occurred in profile P3, PI and P5, while according to the ratio of Si02/AI2O3,
intensive weathering was occurred in profile PI, P3, P4, dan P5. In profile PI, P2,
P4 and P5 the maximum value were attained in B horizon and its derivative ( B2,
BC), whereas for profile P3 and P6, the maximum value were attained in in
succesion A2 and C horizon.
RATNA KHAUSYARI RARWANTI. Distribusi Fe, Al, dan Si Oksida pada
Beberapa Tanah yang Memiliki Batuan Induk Berbeda di Karangsambung,
dan
Kebumen, Jawa Tengah. Di bawah bimbingan VVIDIATMISKANDAR.
Karangsambung merupakan laboratorium alam geologi dimana berbagai
jenis batuan dengan lingkungan permukaan yang berbeda-beda bisa dijumpai.
Lokasi ini merupakan tempat pertemuan antara lempeng samudra Hindia Australia
dengan lempeng benua Eurasia. Adanya berbagai macam batuan, tanah yang
terbentuk kemungkinan akan berbeda-beda pula.
Penelitian ini bertujuan untuk mengetahui distribusi Fe, Al, dan Si oksida
pada berbagai tanah dari bahan induk yang berbeda-beda dan mengetahui tingkat
pelapukan tanah. Pengambilan contoh tanah dilakukan di 6 lokasi yang mewakili
3 batuan induk : batuan beku, sedimen dan metamorf. Profil pertama sampai
keenam (Pl, P2, P3, P4, P5, dan P6) merupakan profil tanah yang terbentuk dari
batuan induk berturut-turut yaitu diabas, filit, rijang, manner, basalt, dan lempung.
Kandungan Fe, Al, dan Si oksida di dalam tanah diekstraks dengan metode
ditionit sitrat bikarbonat, ammonium oksalat dan pirofosfat.
Nilai Fed berkisar 3.73-1.38 % dari terbesar ke terendah adalah P6 > P4 >
P2 > P5 > P1 > P3, sedangkan nilai Fe, (0.50-0.15%) dengan uutan adalah P1 >
P6 > P2 > P4 > P3 > P5. Semua profil memiliki kecenderungan Sip > Alp > Fe,.
Nilai rasio Fe, Al, dan Si oksida berbeda-beda setiap tanah, menunjukkan
dominansi bentuk oksida yang berbeda-beda pula. Profil yang didominansi bentuk
oksida kristalin adalah P2, P4, P5 dan P6, sedangkan profil yang didominansi
bentuk oksida amorf adalah P 1 clan P3.
Tidak ada kemiripan pola dalam distribusi Fe, A1 maupun Si diantara
profil diatas batuan yang sama (batuan beku, sedimen atau metamob).
Berdasarkan hasil FeoiFed tingkat pelapukan yang intensif tejadi pada profil P2,
P4, P5 dan P6. Berdasarkan rasio Si02iFe203, pelapukan intensif tejadi di profil
P3, P1 dan P5, sedang berdasarkan rasio Si021A1203 tingkat pelapukan yang
intensifpada profil PI, P3, P4, dan P5. Bentukan kristalin besi yang diindikasikan
dari nilai (Fed-Fe,) pada PI, P2, P4, dan P5 mencapai maksimum pada horison B
dan turunannya (B2, BC), sedangkan profil P3 dan P6 secara bermrut-turut
mencapai maksimum pada horison A2 dan C.