污染廠址水域環境中生物體內汞及戴奧辛生物累積與環境風險之研究

Abstract

汞與戴奧辛為公認毒性物質，易在脂肪組織中積累，從而造成對人類健康的嚴重危險。然而生物體對於污染物累積的途徑，並不只有由環境的直接接觸這一途徑累積，從食物鏈中的累積也是一個可能的途徑。 本研究以南台灣某鹼氯工廠內貯水池及工廠外鄰近水域之生物體為主要調查對象，廠內貯水池的7種生物樣品中戴奧辛濃度以海鰱最高，已超過食品規範中魚貝類限值(4 pg/ g fresh weight)141倍。而汞濃度分析結果亦為海鰱最高，超過WHO水產品中總汞食用安全限值 0.5 mg/kg。另外，亦於廠外6處魚塭與鄰近溪域進行生物體中汞與戴奧辛濃度補充調查，其中發現有5處魚塭中魚體中汞濃度仍有超限情形，而生物體中戴奧辛濃度皆低於限值，鄰近溪域則是部分樣品有超限情形而已。 本研究以Spearman相關性分析結果顯示，魚體內戴奧辛與汞濃度達顯著相關水準(P<0.01)，相關係數為0.811，屬高度相關，故可推知當魚體食用水域中其他生物體或底泥時，會同時攝入戴奧辛與汞二種污染物並逐漸累積。而進一步由統計分析結果發現，戴奧辛濃度與油脂含量達顯著相關水準(P<0.01)，相關係數為0.833，屬高度相關，亦說明了當魚體內器官中油脂含量越高時，其器官中之戴奧辛濃度將會越高。此外，針對底泥與魚體中戴奧辛17種同源物組成比例進行分析，結果顯示底泥戴奧辛成分主要以OCDD、OCDF、1,2,3,4,6,7,8-HpCDF為主，佔全部80-90%，可確定底泥中污染物來源與土壤一致。惟魚體中戴奧辛同源物則以OCDD、1,2,3,4,6,7,8-HpCDD、1,2,3,6,7,8-HxCDD及1,2,3,4,6,7,8-HpCDF為主(70-80%)，顯示污染物進入魚體中，藉由生物轉換機制導致組成比例而不同。 底泥中的戴奧辛同源物以OCDD、OCDF、1,2,3,4,6,7,8- HpCDF及和1,2,3,4,6,7,8- HPCD為主，與其他研究指出底泥主要存在同源物項目一致，魚體內戴奧辛同源以1,2,3,7,8- PeCDF、1,2,3,4,6,7,8- HpCDF、1,2,3,6,7,8- HxCDD及1,2- 3,4,6,7,8-HpCDD為主，且發現1,2,3,4,6,7,8-HpCDF濃度在於底泥中最低，於生物體反而是最高，推測因高氯不易代謝於體外故累積於體內。 最後由風險計算結果已可明確得知本研究區域之污染對於人體健康影響風險具高度危害可能，再加上國人會食用魚體器官的習性，應立即阻絕食物鏈累積降低危害，建議相關主管機關應加強相關行政管制措施，同時提供當地居民更多資訊與觀念，以達到阻絕食物鏈累積可能對人體健康所造成之危害。

Mercury and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) accumulate in organisms through food webs and exert potentially toxic effects on aquatic organisms and humans. This study examined the levels of mercury and PCDD/Fs in organisms and sediment samples collected from a saltwater pond at the site, a chloralkali factory that shut down in Tainan City, Taiwan. It was also a pentachlorophenol production plant. After the factories were shut down in the 1980s, mercury and PCDD/Fs contamination remained, posing severe health hazards. The correlation between PCDD/Fs congener accumulation patterns in distinct fish organs and the sediment was evaluated. Mercury and PCDD/Fs levels in all the fish samples exceeded food safety limits, and the concentrations of mercury and PCDD/Fs in each species were closely correlated (n = 12, Spearman’s rank correlation [R] = 0.811, p < 0.01). The mercury concentrations were positively but non-significantly correlated with the weight (n = 11, R = 0.741, p < 0.01) and length (n = 11, R = 0.618, p < 0.05) of the species. The fish likely accumulated the contaminants through ingestion of other organisms or the sediment. However, after the pollutants entered a fish, they exhibited distinct accumulation patterns because of their differing chemical properties. Specifically, the mercury concentration was correlated with organism weight and length, whereas the PCDD/Fs concentration was associated with organ lipid content. In this study, the 1,2,3,4,6,7,8-HpCDF concentration was lowest in the sediment but highest in the organisms. However, the OCDD concentration was highest in the sediment but lowest in the organisms. The dominant congeners 1,2,3,7,8-PeCDF, 1,2,3,4,6,7,8-HpCDF, 1,2,3,6,7,8-HxCDD, and 1,2,3,4,6,7,8-HpCDD in the fish differed from those found in the sediment samples. The study results are valuable for assessing the health risks associated with ingesting mercury- and PCDF/F-contaminated seafood from the study site. Therefore, it is suggested that the public should be alerted through bans and advisories when a threat to human health may occur from the consumption of contaminated fish.