Estimation of bioavailable heavy metals in water environments in Bangkok neighborhood

Abstract

The concentrations of dissolved metals in the Chao Phraya River in the stretch between 83 and 29 km away from the river mouth, and some water environment around an industrial estate situated in Bangkok suburb were measured and labile species, self-defined as unbalanced inorganic species were calculated using Visual MINTEQ Ver. 3. The Chao Phraya River sampling was carried out one time, and three time samplings were carried out for the industrial estate. The average inorganic species concentrations of Ni, Cu, Zn, Cd and Pb in 5 samples collected from the Chao Phraya River in the stretch between 83 and 29 km away from the river mouth were, 71.8±12.1μg/L, 3.38±7.02μg/L, 75.8±61.6μg/L, 7.18±1.86μg/L, 6.71±6.14μg/L, which constitutes 96±1.8%, 7.3±14% (when a value of a site was exclude, 1.3±0.87%), 99±0.64%,74 ± 9% and 3.8±2.5% of the dissolved metals, respectively, are found to be labile. The water environments around the industrial estate included raw water from the Chao Phraya River for uses in the estate, treated water for distribution in estate, groundwater in community outside the industrial estate, influent to WWTP (combined from industries and domestic sources within the estate), treated wastewater effluent from WWTP, polishing pond effluent of WWTP, effluent-receiving canal water at 3 points, and the lake water within the industrial estate zone. The dissolved concentrations of Ni, Cu, Cd, Zn and Pb varied from ND to a few hundreds ug/L. Remarkable findings in industrial estate samples are as follows: Treated water showed higher dissolved concentrations of some metals due to decrease in pH during treatment facilities, dissolved concentrations of metals in treated wastewater after activated sludge process and polishing pond treatment did not seem to differ much with those of influent stream which flowed into WWTP, which is in accordance with the previous studies, Groundwater near the estate normally showed low dissolved metals; high Zn and Cd were found in different sampling though,The canal water that received WWTP’s effluent showed some level of dissolved metals; the lake inside the estate compound showed a bit different metals levels, pH and % labilities in some cases, indicating that the source of metals might be different, Zinc showed highest labilities in all samples, which indicated that the environmental settings in all sites favored forming inorganic species. Lowest labilities were found in Cu and Pb, uniformed and moderately high labilities are found in Ni despite difference in sampling sites, and labilities of Cd varied to an extent. The estimated labile concentrations were compared with those measured using a speciation device called Emporeᵀᴹ. The results were found to be different for some reasons.