Details zur Publikation

Referenztyp Zeitschriften
DOI / URL Link
Titel (primär) Sulfur transformations in pilot-scale constructed wetland treating high sulfate-containing contaminated groundwater: a stable isotope assessment
Autor Wu, S.B.A.; Jeschke, C.; Dong, R.J.; Paschke, H.; Kuschk, P.; Knöller, K.;
Journal / Serie Water Research
Erscheinungsjahr 2011
Department UBT; ANA; CATHYD;
Band/Volume 45
Heft 20
Sprache englisch;
Keywords Constructed wetland; Bacterial sulfate reduction; Sulfide re-oxidation; Stable isotopes
Abstract

Current understanding of the dynamics of sulfur compounds inside constructed wetlands is still insufficient to allow a full description of processes involved in sulfur cycling. Experiments in a pilot-scale horizontal subsurface flow constructed wetland treating high sulfate-containing contaminated groundwater were carried out. Application of stable isotope approach combined with hydro-chemical investigations was performed to evaluate the sulfur transformations. In general, under inflow concentration of about 283 mg/L sulfate sulfur, sulfate removal was found to be about 21% with a specific removal rate of 1.75 g/m2·d. The presence of sulfide and elemental sulfur in pore water about 17.3 mg/L and 8.5 mg/L, respectively, indicated simultaneously bacterial sulfate reduction and re-oxidation. 70% of the removed sulfate was calculated to be immobilized inside the wetland bed. The significant enrichment of 34S and 18O in dissolved sulfate (δ34S up to 16‰, compared to average of 5.9‰ in the inflow, and δ18O up to 13‰, compared to average of 6.9‰ in the inflow) was observed clearly correlated to the decrease of sulfate loads along the flow path through experimental wetland bed. This enrichment also demonstrated the occurrence of bacterial sulfate reduction as well as demonstrated by the presence of sulfide in the pore water. Moreover, the integral approach shows that bacterial sulfate reduction is not the sole process controlling the isotopic composition of dissolved sulfate in the pore water. The calculated apparent enrichment factor (ɛ = −22‰) for sulfur isotopes from the δ34S vs. sulfate mass loss was significantly smaller than required to produce the observed difference in δ34S between sulfate and sulfide. It indicated some potential processes superimposing bacterial sulfate reduction, such as direct re-oxidation of sulfide to sulfate by oxygen released from plant roots and/or bacterial disproportionation of elemental sulfur. Furthermore, 41% of residual sulfate was calculated to be from sulfide re-oxidation, which demonstrated that the application of stable isotope approach combined with the common hydro-chemical investigations is not only necessary for a general qualitative evaluation of sulfur transformations in constructed wetlands, but also leads to a quantitative description of intermediate processes.
ID 12029
dauerhafte UFZ-Verlinkung https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=12029
Wu, S.B.A., Jeschke, C., Dong, R.J., Paschke, H., Kuschk, P., Knöller, K. (2011):
Sulfur transformations in pilot-scale constructed wetland treating high sulfate-containing contaminated groundwater: a stable isotope assessment
Water Res. 45 (20), 6688 - 6698