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Title (Primary) Redox dynamics of arsenic species in the root-near environment of Juncus effusus investigated in a macro-gradient-free rooted gravel bed reactor
Author Rahman, K.Z.; Wießner, A.; Kuschk, P.; Mattusch, J.; Offelder, A.; Kästner, M.; Müller, R.A.;
Journal Engineering in Life Sciences
Year 2008
Department UBT; ANA; UBZ;
Volume 8
Issue 6
Page From 612
Page To 621
Language englisch;
Keywords Arsenic removal; Arsenic species; Artificial wastewater; Laboratory-scale constructed wetlands
Abstract In the framework of investigating the dynamics of As species within the planted soil beds of treatment wetlands, the redox dynamics of As species particularly in the root-near environment of the rhizosphere were investigated. For this purpose, long-term experiments were carried out using a specially designed macro-gradient-free rooted gravel bed reactor, planted with Juncus effusus to treat an artificial wastewater containing As (200 g As/L). The exceptional quality of the biofilm processes at the helophyte root-surfaces in treatment wetlands were of special importance in this investigation. The results showed that under C-deficient conditions, a highly efficient As immobilization (> 85 %), obviously due to adsorption and/or co-precipitation, was attained. The addition of organic carbon immediately caused an elevated As concentration and enrichment of As(III) (nearly 80 % of total As) in the reactor. Increasing the SO42- concentration in the artificial wastewater inflow facilitated a high As immobilization (> 82 %) under sulfate reducing condition. In principle, a highly efficient microbial dissimilatory sulfate reduction contributed to S2- formation and a greater As immobilization (most likely as As2S3) under C surplus and reducing conditions. Significant differences in As immobilization were observed by varying the inflow of the SO42- concentration (0.2, 5, 10, 25 S/L) under C surplus conditions. More As(III) precipitates (15 % less in the outflow) when the inflow of the SO42- concentration was decreased from 25 mg S/L to 10 mg S/L. Immobilized As showed greater instability by releasing As(V) (up to 85 % of total As) due to changes in the dynamic redox conditions inside the reactor. Re-oxidation of reduced sulfur into other S species (e.g. S0, SO42-) due to plant-root mediated O2 release probably caused an oxidative dissolution of already precipitated insoluble As (e.g. As2S3) and as a consequent As remobilization. The findings of this study highlighted the significance of SO42- in relation to organic C supply in planted soil beds treating As-contaminated wastewater under constructed wetland conditions.
ID 1333
Persistent UFZ Identifier
Rahman, K.Z., Wießner, A., Kuschk, P., Mattusch, J., Offelder, A., Kästner, M., Müller, R.A. (2008):
Redox dynamics of arsenic species in the root-near environment of Juncus effusus investigated in a macro-gradient-free rooted gravel bed reactor
Eng. Life Sci. 8 (6), 612 - 621