tailieunhanh - Coastal and Estuarine Risk Assessment - Chapter 6

The Bioaccumulation of Mercury, Methylmercury, and Other Toxic Elements into Pelagic and Benthic Organisms - Rất nhiều yếu tố độc hại đối với sinh vật, nhưng thường chỉ trong một hình thức hóa học cụ thể. Ví dụ, mặc dù vô cơ thủy ngân (Hg) là độc hại cho sinh vật ở nồng độ thấp, nó là hình thức hữu cơ của Hg, monomethylmercury (mmHg), đó là cao bioaccumulative và tài khoản cho những mối quan tâm động vật hoang dã và sức khỏe từ việc tiêu thụ cá cao mmHg Đối với kim loại và kim khác, chẳng hạn. | 6 The Bioaccumulation of Mercury Methylmercury and Other Toxic Elements into Pelagic and Benthic Organisms Robert P. Mason CONTENTS Introduction Bioaccumulation in Pelagic Food Webs Bioaccumulation in Benthic Organisms Membrane Transport Processes Summary Acknowledgments References INTRODUCTION Many elements are toxic to organisms but often only in a specific chemical form. For example although inorganic mercury Hg is toxic to organisms at low concentrations it is the organic form of Hg monomethylmercury MMHg that is highly bioaccumulative and accounts for the wildlife and health concerns resulting from the consumption of fish with elevated MMHg For other metals and metalloids such as cadmium Cd lead Pb arsenic As and selenium Se it is also often specific chemical forms such as the free ion . Cd2 or the methylated or reduced species . mono- and dimethylAs or As III that are the most Thus knowledge of the total concentration . the sum of all chemical forms of a potentially toxic element in the environment is insufficient to assess its toxicity accurately. Furthermore it is accepted that contaminants must be in solution to be taken up directly from water3 4 and as a result it is the competitive binding of 2002 CRC Press LLC contaminants to dissolved organic and inorganic ligands colloids and to particulate phases that ultimately controls the availability of an element in an aquatic In sediments it is also the specific composition of the solid matrix such as the amount of organic carbon or sulfide acid volatile sulfide or AVS or pyrite that determines the amount in solution in the sediment pore water 4 5 as well as the bioavailability of the contaminants in the solid phase. For example Lawrence and Mason6 showed that the MMHg bioaccumulation factor BAF for amphipods living in sediment was a function of the sediment particulate organic content POC . Additionally a number of studies have shown that the .