Bioaccumulation of Heavy Metals in Giant Freshwater Prawn, Macrobrachium rosenbergii from Selected Rivers in Sarawak, Malaysia

Masania, Binti Mohd Basri (2019) Bioaccumulation of Heavy Metals in Giant Freshwater Prawn, Macrobrachium rosenbergii from Selected Rivers in Sarawak, Malaysia. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

An assessment of heavy metal concentrations in wild-captured giant freshwater prawns (Macrobrachium rosenbergii) from their natural environment is important since it is susceptible to the environmental pollution due to the rapid developments and human activities along the rivers. Therefore, the objectives of this study were to (1) determine the selected metals (Cd, Co, Cu, Zn, Al and Hg) concentration in muscle tissues, exoskeleton and gills of M. rosenbergii, (2) investigate the relationship between sizes, genders and metals concentration and (3) assess sediment contamination level and food safety indices in the samples. The prawn, water and sediment samples were collected from six rivers (i.e. Sarawak River, Kayan River, Kerang River, Kuap River, Tuang River and Meranek River) during low tides. The off-line preconcentration technique coupled with the Flame Atomic Absorption Spectrometry (FAAS) was used to analyze Cd, Co, Cu, Zn and Al, while Hg was analyzed by using the Flow Injection Mercury System (FIMS) in acid digested prawn, sediment and water samples. The general trends of metals concentration for all rivers were as follow: Hg (0.001-0.530 mg/kg ) < Cd (0.0300- 1.943 mg/kg) < Co (0.020-8.824 mg/kg) < Al (0.640-9.850 mg/kg) < Zn (0.510-109.10 mg/kg) < Cu (0.850-146.480 mg/kg), with their concentrations were higher in gills > exoskeleton > muscle tissues. The correlation between metals concentration and total length of the prawn samples showed relatively positive correlation in all samples from all rivers indicated that metals concentration was higher with increasing of the prawn sizes. In general, male prawn samples contained higher concentrations of metals than female prawns (p < 0.05). The significant differences in concentrations of metals between males and females possibly contributed from their diets, metabolic rates, hormonal and reproductive status. The geo-accumulation index (Igeo) showed that all river sediments were classified as unpolluted to moderately polluted. The iv contamination factors (CF) were ranged from 0 to 3 and classified as low to moderate contaminations. The enrichment factors (EF) were categorised in depletion of minerals level and moderately contaminated level. The food safety indices showed that Cu and Zn were among the highest daily intake of metal (DIM), while Cd have the highest health risk index (HRI) to the consumer thus may impose potential health risk. The highest hazard index (HI) was observed in the sample from Sarawak River (0.69) while the lowest was in the sample from Kerang River (0.25). Thus, the samples from Sarawak River may be hazardous if consumed in an excessive amount. In conclusion, all metals concentrations in M. rosenbergii were below the permissible limits when compared to JECFA (2012) and MFA (1983) except the Cd in Sarawak River. However, regular monitoring on the metals concentration in M. rosenbergii and river sediments need to be done to control the anthropogenic sources of pollutants.

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