8342937125

Pcrtanika 14(1). 83-86 (1991)

COMMUNICATION III

Effect of Organie Matter on the Immobilization of Cadmiiun in Four Malaysian Cocoa Growing Soils

ABSTRAK

Kęsa n ba han organik a las penjerapan kadmium dałam empat jtnis lanah koko Malaysia telah dikaji. Isoterma Langm a i r menu njukkan bahawa unłuk siri Rengam, Bernam dan Selangor muatan penjerapan kadmium meningkat denganpemusnahan kandungan organik. Sebaliknya kesan terbalik didapati pada siri lanah Malaka. Perbezaan mungkindisebabkan oleh kesanpenkelatanyangberlainan antara lanah dengan kadmium.

ABSTRACT

The effect of soil organie maller on cadmium adsorplion in four Malaysian cocoa soils was inuestigated. Langmuir isothenns for the metal show that for Rengom, Bernam and Selangor seńes soils, sorption capacities inereasewith the destruction of organie matter. The reyerse is obtained for Malacca seńes soil. The difference could be due to the different chelatingeffectiyeness of soil organie matter to cadmium.

MATERIALS AND METHODS

Four different soils from cocoa estatesin Peninsula Malavsia were collected from a surface horizon of 0-15 cm and some of their characteristics were deter-mined by standard procedures. The soils investigated were Rengatn (Merlimau), Bernam (Sungei Buluh), Selangor (Flemington) and Malacca (Selbourne).

Co n t a et 7 7meExperi men Is

In all thecontact timeexperiments,0.5gofsoil was shaken in 40 ml of 50/ig mP¹ Cd solution at room temperaturę. Alicjuots of 2 ml were withdrawn at various intervals for analysis of cadmium using a Labtest (710-2000) inductively coupled plasma-atomicemission spectrometer (1CP-AES).

A dsorpl i o n Isot h erm s

Adsorption isotherms were obtained by shaking 0.25 g of soil with 20 ml of Cd solution for 24 h at room temperaturę. In order to prevent precipitation

of ('.d (OH) ₂, a eoncen tration range of 0-150 /ug mg

ml"¹ for Cd was used. The suspension was centri-fuged at 4500 rpm for 10 min and the supernatant wasanalysed for Cd using the method asdescribed. Ihe amount of Cd adsorped was calculated as the difference between the initial concentration and that remainingafterecjuilibration. Data reported are the meansof three replicates. Controls without soils were similarly carried out to ascertain

INTRODUCTION

Cadmium isanon-essential tracę element in plants and animals. Its hazardous effects on human be-ingsarewell documented. It isemitted to theenvi-ronment from industrial activitiesand produets. Its presence in Malaysian cocoaestatesisprobablydue to itsgeochemical origin and/or asacontaminant from application of phosphate fertilizer. Depending on itssource of origin, a rangę of less than 1 to 75

^ig g“¹ cadmium in phosphate fertilizers hasbeen reported (Sauerbeck 1984).

Variousstudieshaveshown that cadmium from the soil can be taken up by the plants, through which itentersthe foodchain. (kadmium availabi-lity to plants depends on many factors. They in-dudesoil pH.clay mineralogy.competinganions, abundance, typeofsorption sitesand complexing agents (organie and inorganic). Ram and Verloo (1985) found that high sorption capacity and the lormation ofstableorgano-metallic complexesled to a relatively lower mobil i ty of cadmium, amongst other heavy metals, in soil. However, Petruzzelli etal (1978) reported that organie matter reduction produced a smali decrease or even aslight inerease in cadmium sorption in four Italian soils.

The purpose of this study is to investigate the effect of organie matter on the immobilization of cadmium in four Malaysian cocoa growing soils.

I his was accomplished by studying the Langmuir isotherms for cadmium with and without the presence of organie matter in the soils.