โครงการ การแพร่กระจายและสะสมของสารปรอทในสิ่งแวดล้อมทางทะเล บริเวณชายฝั่งภาคตะวันออก : รายงานวิจัยฉบับสมบูรณ์ = Distribution and accumulation of Hg in the marine environment of The Eastern Coast of Thailand / วรวิทย์ ชีวาพร ... [และคนอื่น ๆ อีก 3 คน]
Objectives : 1. To investigate the extent of Hg contamination in the marine environment and the biomagnification of Hg in the economic marine animals of the Eastern Coast of Thailand. 2. To assess the risk of marine animal consumption due to the Hg contamination in the Eastern Coast of Thailand. Methodology : 1) Thirty sediment cores were taken from 5 stations namely: Angsila, Sriracha, Laem- Chabang, Pattaya, and Mabtapud for Hg analysis and studies regarding history of Hg contamination in sedimentary column. 2) Marine organisms were collected from Angsila, Laem Chabang, and Rayong province ( Ban Pae) by trawler and plankton net. The samples were kept for bioaccumulation and biomagnification studies. 3) Samples were then analysed for Hg by Nitric acid digestion and measured by means of Hydride generation Atomic Absorption Spectrophotometry ( Perkin Elmer 3300). 4) The data obtained was statistical analysis by ANOVA, Duncan’s New Multiple Range Test and Pearson Correlation analysis. Results : Thirty sediment cores were taken from 5 stations along the coastal line of Chonburi and Rayong provinces. Mercury concentrations were then determined by using a hydride generation atomic absorption spectrophotometer. Sediment texture was analysed by wet sieving techniques, whereas the titration method was used for determination of organic carbon in the sediments. Results of the analysis revealed no significant differences of the mercury level in each depth of the sedimentary column. These findings indicated that there was no increase of the present-day anthropogenic inputs of the mercury contamination when comparing with those of the previous day. Furthermore, the results also demonstrated that there was a significant correlation between the concentration of mercury and the texture of the sediments (%silt&clay) or the total organic carbon contents in the sediments. The mercury content ranged from 4.80 – 37.49 ng/g, which was similar to the un-polluted sediment standard (50ng/g) and lower than the world average value for sediment ( 300ng/g). In finding of the study, it was also found that there were significant differences among the mercury level collected from different seasons and also among those collected from different stations. These temporal and spatial variations were due to different textures of the collected sediments. These findings supported the idea that clay –minerals and organic materials have strong affinity with free mercuric ions. Horizontal distribution of mercury contamination in the area showed higher concentration of mercury contamination in the urban area than in the aquaculture area ( Angsila), tourist area ( Pattaya), and industrial areas ( Laem Chabang and Mabtapud). In a present study, biomagnification of Hg was found in the marine food-chain of Angsila, Laem Chabang, and Rayong province. Hg levels tend to increase at higher trophic levels and according to the animal’s size ( i.e., White shrimp (Peneaus merguiensis) , and Banded crevalle fish (Atule mate) ). The mechanism of this accumulation was not well understood. Discussion, Conclusion : Results of the studies indicated that there was no significant increase of the present-day anthropogenic inputs of the mercury contamination when comparing with those of the previous day. Furthermore, the results also demonstrated that there was a significant correlation between the concentration of mercury and the texture of the sediments (%silt&clay) or the total organic carbon contents in the sediments. Mercury levels tend to increase at higher trophic levels in the food chain and according to the animal’s size. The calculation of PTWI ( Provisional tolerate-weekly intake) indicated that the mercury levels of marine animals from the Easterm Coast of Thailand are within safety limit. Suggestions/Further Implication/Implementation : Results of the studies revealed that there was no significant increase of the Hg levels in the marine sediments from the Eastern Coast of Thailand. However, the results demonstrated that mercury levels tend to increase at higher trophic levels in the marine food-chain and according to the animal’s size. Provisional tolerate weekly intake(PTWI) value indicated that marine animal from the Eastern Coast are still safe for consumption. For further studies, we recommend to extend the study areas to cover the whole gulf of Thailand.
CONTENT
History of Hg contamination as recorded in the sediment core from the Eastern Coast of Thailand -- Bioaccumulcation and biomagnification of Hg in the Eastern Coast of Thailand
