|Title (Primary)||Sulfur isotope fractionation and sequential extraction to assess metal contamination on lake and river sediments|
|Author||Ribeiro De Souza, L.; Knöller, K.; Queiroz Ladeira, A.C.|
|Journal||Journal of Soils and Sediments|
|Keywords||Acid volatile sulfides Bacterial sulfate reduction Metals Sediments Sulfur isotopes|
|UFZ wide themes||RU2;|
The present study investigated lake and river sediments affected by metals from an acid mine drainage (AMD) from a former uranium mine. The role of bacterial sulfate reduction in the immobilization of contaminants was evaluated, and the analyses of acid volatile sulfide (AVS) and sequential extraction were performed. Consequently, the potential mobility and bioavailability of contaminants were established.
Materials and methods
Sulfur isotopic fractionation (δ34S), AVS, and sequential extraction procedure were used to assess the sulfate bacterial reduction and the availability of contaminants in the environment at six sampling stations.
Results and discussion
The δ34S indicated that bacterial reduction is a key process in the natural attenuation of contamination in the Águas Claras reservoir, precipitating metal sulfides. According to the USEPA criteria, adverse biological effects are expected for sample S1 (inside the reservoir) which is likely to be toxic, while for sediment S4 (in the river), the toxicity is uncertain. The other samples were classified as non-toxic, likely because of the decreased solubility of zinc sulfide. A decrease in the concentration of the contaminants downstream of the reservoir was observed. The predominance of U (0.4 %) in the labile fraction and the elevated concentrations of Zn (0.5 %) and Mn (0.7 %) in the sediments inside the reservoir raises concerns regarding the availability of these contaminants in the environment.
The main environmental impact appears to be concentrated in the Águas Claras reservoir, whereas the Antas creek does not seem to be affected by the AMD process. Although the bacterial sulfate reduction is effective in its production of sulfides capable of immobilizing the contaminants, the presence of Zn and U in the labile and reducible fraction is a matter of concern due to its long-term bioavailability. Thus, continuous monitoring of the redox potential of the waters and sediments, mainly in the reservoir, is recommended in order to assess and possibly prevent later dissolution of sequestered contaminants.
|Persistent UFZ Identifier||https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=17680|
|Ribeiro De Souza, L., Knöller, K., Queiroz Ladeira, A.C. (2016):
Sulfur isotope fractionation and sequential extraction to assess metal contamination on lake and river sediments
J. Soils Sediments 16 (7), 1986 - 1994