Penobscot River Mercury Study, 479 Beechwood Ave., Old Town, ME 04468, USA.
Department of Biology, McMaster University, 1280 Main St W., Hamilton, Ontario L85 4K1, Canada.
Sci Total Environ. 2019 Feb 1;649:770-791. doi: 10.1016/j.scitotenv.2018.08.203. Epub 2018 Aug 23.
Mercury (Hg) concentrations in aquatic biota, including fish and shellfish, were measured over the period 2006-2012 in the lower Penobscot River and upper estuary (Maine, USA). The Penobscot is a system contaminated with Hg by a chlor-alkali plant that operated from 1967 to 2000, discharging 6-12 tons of mercury into the river. Mercury levels in aquatic biota were highest at sites downstream of the chlor-alkali plant and spatial trends were similar to those of sediments. Mean total Hg concentrations in fish muscle (adjusted for size or age) in the most affected areas were 521 (480, 566; 95% CI) ng/g ww in American eels, 321 (261,395) in mummichog, 121 (104, 140) in rainbow smelt, 155 (142,169) in tomcod, 55.2 (42.7,71.4) in winter flounder, and 328 (259,413) in American lobster tail and 522 (488,557) ng/g dw in blue mussel. Levels exceeded the 50 ng/g ww considered protective for piscivorous predators and were of concern for human health, with American eels and American lobster exceeding Maine's mercury action level of 200 ng/g ww. Calculations of trophic position (using nitrogen isotopes) suggested that the spatial patterns observed in total Hg concentrations were not due to changes in feeding habits of the species. Fish feeding in benthic food webs, as defined by stomach content and stable carbon isotope analyses, showed no change in Hg concentrations over time. In contrast, declining trends in Hg were found in two species dependent on pelagic food webs. The absence of declines in Hg concentrations in the benthically-based food webs, despite the fact that most Hg was discharged into the system >40 years ago, is consistent with the long recovery predicted from dated sediment cores and from similar studies elsewhere.
2006 年至 2012 年期间，在美国缅因州的下彭布罗克河和上游河口处测量了水生生物（包括鱼类和贝类）中的汞浓度。彭布罗克河系统受到一家氯碱厂的汞污染，该氯碱厂于 1967 年至 2000 年运营，向河流排放了 6-12 吨汞。在氯碱厂下游的地点，水生生物中的汞含量最高，空间趋势与沉积物的趋势相似。在受影响最严重的地区，调整大小或年龄后的鱼类肌肉中总汞浓度（ng/g ww）分别为美洲鳗鱼 521（480，566；95%置信区间）、美洲鱚 321（261，395）、虹鳟 121（104，140）、海鲷 155（142，169）、比目鱼 55.2（42.7，71.4）和美洲龙虾尾 328（259，413），贻贝 522（488，557）ng/g dw。这些水平超过了 50ng/g ww，被认为对以鱼为食的捕食者具有保护作用，这对人类健康构成了担忧，其中美洲鳗鱼和美洲龙虾超过了缅因州 200ng/g ww 的汞行动水平。营养位（使用氮同位素）的计算表明，总汞浓度的空间模式不是由于物种摄食习惯的变化造成的。根据胃内容物和稳定碳同位素分析，以底栖食物网为食的鱼类，其汞浓度随时间没有变化。相比之下，在两种依赖于浮游食物网的物种中，发现了汞浓度下降的趋势。尽管大多数汞是在 40 多年前排放到系统中的，但底栖食物网中的汞浓度没有下降，这与从年代测定的沉积物芯和其他地方的类似研究中预测的长期恢复情况一致。
