Response of a free-water surface constructed wetland after a Cr(VI) accidental dump.

MAINE, M. A.; SANCHEZ, G.C.; MUFARREGE, M. M.; HADAD H. R.; DI LUCA, G. A.; CAFFARATTI, S. E.; PEDRO, M. C.

Nantes

Congreso; WETPOL 2013; 2013

Ecole des Mines de Nantes-GEPEA

The aim of this work was to evaluate the response of the wetland system faced with an accidental dump of Cr(VI). The concentration of Cr(VI) and total Cr in water decreased significantly in the outlet effluent (Fig. 1). No significant differences were found between the concentration of total Cr and Cr(VI) in water over time. Cr(VI) can be reduced by organic matter, Fe(II), dissolved sulfides, and humic compounds with sulfhidryl groups. In this case, organic matter probably caused the reduction of Cr(VI) to Cr(III), which immediately precipitated as oxihydroxides. After the dump, Cr concentration in sediment was significantly greater in the inlet than in the outlet area, indicating retention by sediment. T. domingensis tolerated the treatment in the outlet area while it died in the inlet area. A layer of plant detritus covered the sediment in the inlet area. Plant detritus showed higher Cr concentration than sediments. Cr concentration increased significantly in root tissues of the inlet area, reaching values higher than those reported in literature. Cr concentration in leaves was significantly lower than that found in roots, indicating low translocation. As Cr concentration in water decreased after 30 days, the wetland was emptied, plant detritus containing high Cr concentrations was removed and new specimens of T. domingensis were planted in the inlet area.