Alvarez-Iglesias P, Rubio B
Departamento de Geociencias Marinas y Ordenación del Territorio, Facultad de Ciencias, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Pontevedra), Spain.
Mar Pollut Bull. 2009 Apr;58(4):542-51. doi: 10.1016/j.marpolbul.2008.11.026. Epub 2008 Dec 27.
Mariculture is an important economic activity in shallow marine areas of the Rías Baixas (Galicia, NW Spain). The maintenance of high product quality requires surveillance of environmental quality, including the risk of metal toxicity. In this study the redox status of intertidal sediments in the Bay of San Simón, and the risk of toxicity posed by their As, Cd, Cr, Cu, Mn, Ni, Pb and Zn contents, were evaluated by determination of operationally defined reactive, silicate-bound, organic and pyrite-related fractions of these elements and of Fe. The large silicate-bound fractions of most of these metals indicate their lithogenic origin; the main exception is Pb, which in all respects exhibits singular behaviour associated with its predominantly anthropogenic origin in a ceramics factory. In sediments with larger fine-grained particle contents, which are oxic only in the top few centimetres, greater proportions of the trace elements are present as sulphides or associated with sulphide minerals: the degree of pyritization of Fe (DOP) is 46% overall, and the pyrite fraction of some elements doubtless increases at the expense of the reactive fraction, most overall degrees of trace metal pyritization (DTMPs) lying in the range 10-50%. A decline in pyrite genesis at depths below about 18 cm in these sediments is attributed to the exhaustion of organic matter susceptible to metabolization by sulphide-generating bacteria. In coarse-grained, oxic sediments the oxidation of sulphides makes pyrite-related fractions very small, and reactive and silicate-bound fractions are negatively correlated; reactive fractions associated with Fe-Mn oxyhydroxides are large, and DOP and DTMPs are low (generally much lower than in mud-rich sediments), except for Pb. Most of the elements studied are mainly present in forms that are neither bioavailable nor potentially bioavailable, and so do not constitute a significant environmental threat. However, the high DTMPs of Cu and Pb indicate significant potential bioavailability, which should be taken into account in evaluations of environmental quality and the risk to bivalve cultures.
海水养殖是西班牙西北部加利西亚下海湾浅海区域的一项重要经济活动。维持高产品质量需要监测环境质量，包括金属毒性风险。在本研究中，通过测定这些元素以及铁的可操作定义的活性、硅酸盐结合、有机和黄铁矿相关部分，评估了圣西蒙湾潮间带沉积物的氧化还原状态，以及其砷、镉、铬、铜、锰、镍、铅和锌含量所造成的毒性风险。这些金属中大多数的硅酸盐结合部分较大，表明它们来自岩石成因；主要例外是铅，在各方面都表现出与陶瓷厂中主要人为来源相关的独特行为。在细颗粒含量较高的沉积物中，仅顶部几厘米为有氧环境，更多比例的微量元素以硫化物形式存在或与硫化物矿物相关：铁的黄铁矿化程度（DOP）总体为46%，一些元素的黄铁矿部分无疑以活性部分为代价而增加，大多数痕量金属黄铁矿化程度（DTMPs）在10 - 50%范围内。这些沉积物中约18厘米以下深度黄铁矿生成的下降归因于易被产硫化物细菌代谢的有机物的耗尽。在粗颗粒、有氧沉积物中，硫化物的氧化使黄铁矿相关部分非常小，活性和硅酸盐结合部分呈负相关；与铁 - 锰羟基氧化物相关的活性部分较大，DOP和DTMPs较低（通常远低于富含泥质的沉积物），铅除外。所研究的大多数元素主要以既非生物可利用也非潜在生物可利用的形式存在，因此不构成重大环境威胁。然而，铜和铅的高DTMPs表明存在显著的潜在生物可利用性，在评估环境质量和双壳贝类养殖风险时应予以考虑。
