Interaction of Pb, Ni and Cd with Aquatic Humic Substances of Amazonian Blackwater Rivers

In this study, the extraction and characterization of aquatic humic substances (AHS) from two blackwater rivers in the Amazon basin was carried out in order to assess the seasonal effects in the AHS structure. In addition, an investigation of the complexing capacities (CC) of the structures containing the metal ions CdII, NiII and PbII was also done. The characterization (of the AHS) was done using UV-Vis, molecular fluorescence, and infrared spectroscopy. AHS from the Negro River showed more aromatic characteristics in its structures and molecular weight, than the AHS from the Carú River. The AHS studied presented a seasonal pattern characterized by higher humification levels during the rainy season. For all the metals, the AHS complexing capacity was higher for the Negro River. The highest complexing capacities were observed for the NiII assays, which were 0.56 and 0.12 µmol NiII mg-1 dissolved organic carbon (DOC), for AHS RN and AHS RC-II, respectively. We concluded that the transport, bioavailability, and toxicity, of these metal species should be higher for Carú River.

本研究针对亚马逊流域两条黑水河流中的水生腐殖物质 (aquatic humic substances，以下简称AHS) 开展提取与表征工作，以探究其结构的季节变化效应。此外，本研究还测定了AHS对镉(II)、镍(II)及铅(II)金属离子的络合容量 (complexing capacities, CC)。本次表征采用紫外-可见分光光度法、分子荧光光谱法及红外光谱法完成。相较于卡鲁河的AHS，内格罗河的AHS不仅芳香性结构特征更显著，分子量也更高。本次研究涉及的AHS呈现出显著的季节变化规律：雨季时其腐殖化程度更高。针对所有受试金属而言，内格罗河AHS的络合容量均高于卡鲁河AHS。其中镍(II)离子的络合容量测定结果最高：内格罗河AHS（AHS RN）与卡鲁河AHS（AHS RC-II）的络合容量分别为0.56与0.12微摩尔镍(II)/毫克溶解有机碳 (dissolved organic carbon, DOC)。本研究最终得出结论：卡鲁河中的此类金属形态，其迁移行为、生物有效性与毒性均更高。