| Abstract | Problems of heavy metal pollution in marine environment are caused mainly by the discharges of treated water from land-based industries and agriculture. A number of common heavy metals causing marine pollution include lead (Pb), cadmium (Cd), copper (Cu) and zinc (Zn). Most heavy metals can be accumulated through the food chain making seafood hazardous to human consumers. This study was conducted with the general objective to determine the accumulation of heavy metals in green mussels (Perna viridis). It comprises two major parts; field survey and experiment. The field survey was conducted monthly during February-September 1994 with the objectives to determine the seasonal and areal variation of heavy metals (Cd, Pb, Zn and Cu0 in green mussels at the Upper Gulf of Thailand; the Ang Sila Bay, the Bang Pakong Estuary, the Chao Phraya Estuary and the Mae Klong Estuary. The relationship of heavy metals in soft tissue of green mussels, suspended solids and seawater was also studied The experimental part comprises two experiments with the aim to obtain the knowledge of heavy metal kinetics in green mussels (Perna viridis). The first experiment lasted for 20 days with heavy metals analysis every 5 day and the second experiment lasted only 6 days with daily heavy metals analysis. Heavy metals were analyzed by flame atomic absorption spectrophotometer extraction process. Green mussels were exposed to seawater media in 10 tons cement tanks which were added 15 ug/L of Cu and non Cu-added (control). Cu concentration in green mussel, faecal materials and Chaetoceros sp. were analyzed to compare for the difference between control tank and contaminated tank. The study found that green mussels have significant higher concentrations of Cd, Pb and Zn in wet season than in dry season. The significant annual different of Cd was found at the Ang Sila Bay and the Chao Phraya Estuary, Pb was found at the Mae Klong Estuary, and Zn was found at the Ang Sila Bay and the Mae Kkong Estuary. Significantly higher concentration of Cd in suspended solids was found at the Ang Sila Bay, Zn was also found in wet season at Bang Pakong and Mae Klong Estuaries. However, there was no seasonal difference of heavy metals concentration in seawater. The average results show that there was significant difference of heavy metals concentration in green mussels collected from 4 different sites. The average minimum concentrations of Cd, Zn, and Cu found at Bang Pakong Estuary was 1.55+_1.06, 33.97+_8.59 and 7.56+_1.06ug. g1 dry.wt, respectively, The average maximum concentrations of Cd, Zn and Cu found at Chao Phraya Estuary was 6.87+_3.14, 45.32+_12.14 and 9.96-_1.60 ug. g1 dry.wt, respectively. The minimum and maximum mean Pb concentration was 3.86+_2.06 and 5.98+_6.24 ug. g1 dry.wt at Chao Phraya Estuary and Bang Pakong Estuary, respectively. The average maximum concentration of Cd, Pb and Cu in suspended solids was 17.88+_23.9, 35.81+_23.7 and 46.43+_13.9 ug. g1 dry.wt, respectively at Ang Sila Bay. The average minimum of Zn was 147.20+_146.02 ug. g1 dry.wt and average minimum of Pb and Cu was 15.03+_ 7.60 and 21.06+_8.70 ug. g1 dry.wt at Bang Pakong Estuary. The average minimum of Cd and Zn was 1.15+_1.09 and 87.7+_77.71 ug. g1 dry.wt at Chao Phraya Estuary and Mae Klong Estuary , respectively. The Chao Phraya Estuary had higher accumulation of Cd, Zn and Cu in green mussels than the other 3 sites, but Pb was the lowest. Contrasting to the Chao Phraya Estuary, the Bang Pakong Estuary has highest accumulation of Pb but lowest Cd, Zn and Cu in green mussels. However, the average value of Cd (0.56 mg kg wet wt), Pb (0.76 mg kg wet wt) and Cu (1.14 mg kg wet wt) in green mussels revealed that the accumulation of htese heavy metals did not exceed the maximum allowable level of 2.0 mg Cd kg wet wt (UNEP/FAO/WHO,1988), 2.0mg Pb and 5.0 mg Cu kg wet wt (FAO/WHO Food Standard Programe, 1990), respectively, However, it was found that the average maximum concentration of Zn (5.23 mg. kg wet wt) in green mussels at the Chao Phraya Estuary slightly exceeded the maximum allowable level of 5.0 mg Zn kg wet wt (FAO/WHO Food Standard Programe, 1990). Cd is the only heavy metal in green mussels that varied and has positive correlation with the variation in suspended solids and seawater. The results of the first experiment show that the average concentration of cu in Chaetoceros sp., green mussels and faecal materials in Cu contaminated tanks was 56.50+- 7.76 ug. g dry wt, 13.25+_3.12 ug. g dry wt and 117.59+_49.71 ug. g dry wt compared to non-contaminated tanks at 16.78+-4.09 ug. g dry wt, 8.80+_0.56 ug. g dry wt and 37.12+-3.40 ug. g dry wt, respectively, Rapidly increase of cu in green mussels and fiscal materials was observed in the first two days in Cu contaminated tank in experiment two. Some of green mussels in contaminated tanks were transferred to control tanks on day sixth and green mussels were sampling to analyze every 6 hours for 48 hours to determine the depuration. The Experiment show that average concentration of Cu in green mussels continuously decreased from 16.92 ug.g dry wt to 8.56 ug. g gry wt within 48 hours. Accumulation and depuration in the experiment two indicated that the concentration of metal played an important role in the processes. |