Long-term influence of red mud on As mobility and soil physico-chemical and microbial parameters in a polluted sub-acidic soil.
In this study we evaluated the efficiency of red muds (RM, a bauxite residue) to immobilize the arsenic present in a polluted sub-acidic soil (UP-soil; total As 2428 mg kg(-1)) and to influence some chemical, biochemical and microbiological properties after 2 years since RM addition. The RM addition caused a pH increase, a striking decrease of total organic carbon and a significant increase of water-soluble C, N and P. The analysis of As mobility through sequential extraction showed a reduction of the water-soluble arsenic in the RM-soil compared to the UP-soil (3.44% and 5.59% of the total As respectively) and a remarkable increase of the residual (non extractable) arsenic fraction in the RM-soil (>300% compared to UP-soil). RM addition increased significantly the microbial abundance and the activity of selected enzymes (dehydrogenase, urease) with respect to UP-soil while had a major influence on the structure of soil microbial communities as evaluated by the Biolog Community Level Physiological Profile. The reduced As mobility, together with an increase of C, N and P labile-pool (likely originating from a "de-structuring effect" of RM on the soil organic matter) were identified as the key factors affecting the biological activity in the RM-treated soil.
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agro-Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy. ggarau@uniss.it
Giovanni
G
Garau
Margherita
M
Silvetti
Salvatore
S
Deiana
Pietrino
P
Deiana
Paola
P
Castaldi
D000537:Aluminum Oxide / Q000737:chemistry*; D001151:Arsenic / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry*
D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D000537:Aluminum Oxide; D001151:Arsenic