【摘 要】
：
Bioaccumulation of methylmercury through food chains is of great concern due to health risks associated with high levels of mercury in high trophic level organisms,such as sea birds or predatory fish.
【机 构】
：
Water Quality Centre,Trent University,Peterborough,ON,Canada
【出 处】
：
The 17th International Conference on Heavy Metals in the Env
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Bioaccumulation of methylmercury through food chains is of great concern due to health risks associated with high levels of mercury in high trophic level organisms,such as sea birds or predatory fish.Of particular concern are areas that may have increased exposure to mercury and methylmercury and areas populated by already endangered species.One site of interest is the Ebro River catchment of North-eastern Spain,a region of~85,000 km that is influenced by mercury producing industries and a large human population(~3 million)and is the breeding grounds of several piscivorous birds including sea gull and purple heron.Feathers from purple herons that fed on freshwater fish near the discharge site had the highest Hg levels of up to 7 ?g/g.In some bird species,Hg concentrations over 3 μg/g in blood has been associated with nesting behaviour changes that adversely influence reproductive success.Therefore it is likely that the purple heron is experiencing similar stresses and monitoring of behaviour and testing of other material,such as blood and eggs,is warranted.Hg mass-dependent fractionation(MDF),represented by ? 202Hg,and mass-independent fractionation(MIF),represented by Δ199Hg were both detected.The variations in isotope ratios between the bird species probably reflect the difference between marine and freshwater food sources.The MIF signature from all three freshwater sites appeared different from one another,but were also lower than the marine site values.Longer time for photodegradation,thought to be the primary mechanism responsible for MIF in aquatic reservoirs,could explain some of this pattern.
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