汞在污染場址魚體及環境介質分佈以及生物習性影響之探討

Abstract

在受到汞污染的水體中，水產生物會經由其食物來源累積汞，進而被人們食用，對人體造成傷害。因此本研究嘗試建立預測魚肉中汞濃度的方法，藉以評估污染可能造成之風險。本研究於2005年2月至2006年3月採集底泥樣品水樣，於2005年2月及魚體樣品進行研究。 在魚體樣品分析結果中總汞濃度以海鰱最高達3.26±0.70ppm，鯔最低為0.30±0.06ppm，甲基汞濃度以海鰱最高達3.08±0.72ppm，鯔最低為0.25±0.05ppm，顯示該區魚體遭受污染，其生物對於底泥之累積因子為0.1297。 δ15N分析結果顯示魚體樣品體內δ15N之大小次序和資料庫所記載之營養階層有相當程度之差異，並且各魚種間魚體中汞濃度之含量與δ15N相關性並不明顯，但可以確定的是一般認為營養階層較高之肉食性魚類其體內易有較高之汞濃度。且發現雖然個別魚種內δ15N與汞濃度具有相關性，但卻易隨著季節有大的變化，例如冬天有較低的汞濃度。比較各魚體汞濃度及基本特性之相關性後，發現魚體體重及體長可能是影響魚體汞濃度之因子。 風險評估結果顯示以居民食用十分之一場址水產之情況下，其危害商數並未大於1，表示並無立即危害。但因魚體內甲基汞濃度仍超過魚蝦類管制標準，顯示底泥遭受汞污泥之污染，雖對於當地居民並無立即危害，但若以保守情況估計，其危害商數仍會大於1，仍建議封閉該場區並禁止捕撈水產生物。

Fishery products will accumulate mercury via their food source in contaminated water bodies, and then be consumed by people, and causing the injury to human bodies. This study is aimed to develop the method predicting the mercury concentration in fish and the human risk. The bottom mud samples, water sample, fish, specimen were collected during September 2005 to March 2006. The results showed that the total mercury concentrations of Elops machnata was up to 3.26±0.70ppm. The concentrations of total mercury for Mugil cephalus was only 0.30±0.06ppm. However, biomagnification is not obvious. The result of δ15N analysis indicates no correlation with the trophic level base on the fish. The concentration of mercury in the fish`s body is independ of δ15N, however that the carnivorous fish of high trophic level contains higher concentration of mercury is confirmed. The mercury concentration is related to δ15N in some individual fish, but varied with season. There is lower mercury concentration in winter. Comparing the fish's mercury concentration to the basic fish's character, we found that the mercury concentration is affected by the weight and length of fish. The result of risk assessment suggest that Non-cancer Hazard Quotient (HQ) was lower than 1. There is no imminent hazard. However, the methyl mercury concentration in fish still exceeds the fish and shrimp's regulatory standard. Although the bottom residents which contains it is suggested, mercury has no danger immediate to local residents, that sealing this place and stopping harvesting the aquatic products is necessary.