Kajian penspesiesan dan ketoksikan logam dalam sistem akuatik tasik bekas lombong bijih timah menggunakan model unjuran

Abstract

In aquatic environment, metals can exist in many physicochemical forms or species that can be classified based on their particle size and toxicity. The toxicity of the metals species can be explained by the development of toxicity model which are made in two steps in this research. The first step was to determine the toxic value of metal using bioassay method and speciation calculated by MINTEQA2 software, and second step was done by the linearity relationship that exists between toxic value and species concentrations that were analysed by ridge regression method. The evaluation of toxicity model for several metals species Al(III), As(III), Fe(III), Mn(II) and Zn(II) for sets of water quality data from previous studies was carried out to measure whether the metal species are toxic (negative value of the coefficient regression) or non-toxic (positive value of the coefficient regression), and the analytical results revealed that the model being developed showed the toxic properties of metal species accurately. However, to use this toxicity model a complete water quality data of pools must be obtained. In this study, the physicochemical parameters was monitored for tin mining pools around the districts of Selangor at monthly intervals from July 1999 until April 2000, the analytical water quality results show that almost all of the parameters studied are within acceptable limits as stipulated, except for COD and Al, As, Fe and Mn. Meanwhile the type of metal species present are found to be dependent on pH. In the determination of the toxicity of metals species Al(III), As(III), Fe(III), Mn(II) and Zn(II) in each set of water quality data, a toxicity study for each individual metals, metals mixture and pools metals-mixture were carried out using juvenile tilapia merah (Oreochromis sp.). Results show that increasing hardness and pH can decrease the individual toxicity of metals (96h-LC50 M mg/L), and decreasing the toxic property of metals mixtures (96h-LC50 M, STU are TR = 1:1:1:1:1), meanwhile the order of toxical pollution pools can be based on toxical lifetime median (LT50) were L4, L1, L5, L3 and L2. Nevertheless, toxical result of metal species exist in setting water quality from toxical studies and water pools metal pollution was indicated by the amount of toxic metals species and nontoxic metals species for tilapia merah juvenile.