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Clay Mineralogical Composition of Some Acid Sulphate Soils from Cox's Bazar District in Bangladesh

S. Rahman
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

A. Islam
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

M. S. Hussain
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

Five pedons of acid sulphate soils from Cox's Bazar coastal belt were investigated to identify clay minerals and nature of weathering in these pedons. The soils have pH values below 4.0, high amounts of kaolinite, illite and also trace amounts of smectite, chlorite, vermiculite, mica, feldspar and interstratified 7Å + 10Å and 10Å + 14Å clay minerals. X-ray diffractograms of Mg-saturated glycolated clay samples of A and C horizons of the pedons showed that in Chakaria-a and -b there were no differences in the distribution of 7.0, 10.0 and 14.0 Å minerals. The 7.0 Å mineral has increased and 10.0 Å mineral decreased at the surface of Badarkhali and Cheringa-a soils. The concentration of 7.0. 10.0 and 14.0 Å minerals were increased at the surface soils of Cheringa-b. These differences were related to changes caused by pedogenic weathering.

Keywords: Acid sulphate soils, Dominant minerals, Clay mineral, Mangrove tidal floodplain

Location: Cox's Bazar district, Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land management

Objectives:

Objective of the study was to determined the clay mineralogical composition of some acid sulphate soils from cox's Bazar district in Bangladesh.

Methodology:

In the present study, mangrove tidal floodplain of Cox's Bazar district was selected as a representative area of acid sulphate soils in Bangladesh. This area comprised south eastern and north western parts of Cox's Bazar district which lies between approximately 20°45 and 21°45 north latitudes and 91^o45 to 92°45 east longitudes. During the field study, twenty one soils sample on horizon basis from five pedons of various stages of development were collected for laboratory analyses. Of these pedons, two belonged to Chakaria (potential), two to Cheringa (actual) and one to Badarkhali (actual) series, treated to be K-saturated and Mg-saturated, The minerals were determined from the X-ray diffraction patterns of these specimens, After running X-ray, the Mg-saturated slide was treated with glycol and the K- saturated slide heated at 550^oC. Again, the materials on slides were run by X-ray diffraction technique and the clay minerals were identified from the diffractograms. Identification and estimation of mineral contents were then made from relative peak height and peak area by comparing with X-ray patterns of standard minerals.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 15, No. 2, 115-122, 1991

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The high content of mica in the acid sulphate soils of Cox's Bazar in Bangladesh was due to the nature of their parent materials. In some nonacid alluvial soils of the coastal belt of Bangladesh, Hassan and Razzaq and Hussain et. al. separated high contents of mica, Kaolinite and smectites. The soil studied by the above authors were formed on the Gangetic alluvium and as a result considerable quantities of smectites were found in them. The acid sulphate soils from Cox's Bazar area were on recent alluvium. As a result, the amount of smectite in them is quite small. From the above X-ray diffractograms results it appears that there is increase of 7.1 Å minerals and a decrease of 10.0 Å minerals in the surface horizon of the actual acid sulphate soils. Lepidocrocite was found in trace amount in Chakaria profiles. The X-ray diffraction patterns show that Badarkhali and Cheringa profiles have low content of jarosite minerals in their clay fractions.

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