Marques Aguinaldo N, Monna Fabrice, da Silva Filho Emmanoel V, Fernex François E, Fernando Lamego Simões Filho F
Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal Fluminense, Outeiro São João Batista, s/n, Centro-Niterói, Caixa Postal 100 644, 24 001-970, RJ, Brazil.
Mar Pollut Bull. 2006 May;52(5):532-9. doi: 10.1016/j.marpolbul.2005.09.048. Epub 2005 Nov 23.
Zn and Cd concentrations, stable lead isotopes and 210Pb-derived chronology were determined in a sediment core sampled at Sepetiba Bay (South-eastern Brazil). During the last decades, the bay's watershed has been modified by the increase of industrial activities and human interventions. In particular, Zn and Cd ore treatment plants were built near the coast in 1960 and 1970, respectively, and water has been diverted from the adjacent Paraíba do Sul River watershed since 1950. The core collected at shallow depth near the industrial area exhibits four successive events: (i) at 50 cm depth, a change in the 206Pb/207Pb ratio from about 1.162 to more than 1.18 might be the result of the São Francisco Channel opening and water diversion from Paraíba do Sul river; (ii) at 40 cm depth, Zn concentration starts to increase (up to 0.8 mg g(-1)) (iii) above 30 cm depth, relatively high Cd concentrations (up to 1.6 microg g(-1)) are observed and (iv) at 16 cm depth, change in unsupported 210Pb slope is probably related to a waste dam built to prevent strong metal contamination in the bay. Sediment accumulation rates evaluated by Zn and Cd profiles used as time-markers are higher than those calculated from 210Pb-based chronology models. Using the constant initial concentration (CIC) model both events are supposed to date back to about 1884 and 1902, respectively, while using the constant rate of supply (CRS) model it shifts to about 1925 and 1935. Such discrepancies are probably assigned to the fact that these models do not take into account site-specific local sedimentation dynamics. In the study area, particles deposition seems to be controlled by enrichment with unsupported 210Pb transported by runoff from a mangrove flat bank. Chronology derived from a model that assumes an exponential increase of the initial 210Pb activity fits well with the estimated rates obtained from historical events.
对在塞佩蒂巴湾（巴西东南部）采集的一根沉积物岩芯测定了锌和镉浓度、稳定铅同位素以及源自210Pb的年代学。在过去几十年间，该湾的流域因工业活动增加和人类干预而发生了改变。特别是，锌矿和镉矿处理厂分别于1960年和1970年在海岸附近建成，并且自1950年以来水已从邻近的帕拉伊巴杜斯尔河流域被分流。在工业区附近浅深度采集的岩芯呈现出四个连续事件：（i）在50厘米深度处，206Pb/207Pb比值从约1.162变为超过1.18，这可能是圣弗朗西斯科海峡开通以及帕拉伊巴杜斯尔河的水被分流的结果；（ii）在40厘米深度处，锌浓度开始增加（高达0.8毫克/克（-1））；（iii）在30厘米深度以上，观察到相对较高的镉浓度（高达1.6微克/克（-1））；以及（iv）在16厘米深度处，无支撑210Pb斜率的变化可能与为防止该湾受到强烈金属污染而建造的一个废渣坝有关。通过用作时间标记的锌和镉剖面评估的沉积物堆积速率高于根据基于210Pb的年代学模型计算得出的速率。使用恒定初始浓度（CIC）模型，这两个事件分别被认为可追溯到约1884年和1902年，而使用恒定供应速率（CRS）模型时，时间则变为约1925年和1935年。这种差异可能归因于这些模型没有考虑特定地点的局部沉积动力学这一事实。在研究区域，颗粒沉积似乎受来自红树林滩岸径流输送的无支撑210Pb富集的控制。源自假设初始210Pb活度呈指数增加的模型的年代学与从历史事件获得的估计速率拟合良好。
