ABSTRACT
The fate of Cd, Pb, Cu, Zn, Ni, Cr, and As in a horizontal subsurface flow-constructed wetland was studied. The concentrations of the risk elements in treated municipal wastewater, wetland sediments, and Phragmites australis biomass were determined. Most of the studied elements were removed from the wastewater with fair efficiencies. On the other hand, As was released to treated water in the wetland bed. The removal efficiencies obtained for the individual elements were as follows: 64.2, 48.7, 70.0, 93.9, 63.6, 63.8, and -236.2%, respectively. The concentrations measured in sediments were the highest for samples taken 1 m from the inflow zone. They were 4.11, 2.01, 6.01, 4.85, 3.39, 9.30, and 3.17 times higher as compared to the samples taken in the distance of 10 m. The pollutants were preferentially deposited at the front part of the wetland bed where anaerobic conditions predominated and sulfate reduction took place. There were no significant differences in the concentrations of the studied elements in the aboveground biomass (Phragmites australis) samples taken in the distances of 1, 5, and 10 m from the inflow zone. However, the concentrations measured in the belowground biomass samples were significantly higher for samples taken at the front part of the wetland bed. The individual element concentration ratios between the below- and aboveground biomass measured for samples taken 1 m from the inflow zone were 4.97, 5.97, 2.21, 1.58, 2.26, 5.70, and 2.66 for Cd, Pb, Cu, Zn, Ni, Cr, and As, respectively.
