[Spatial and temporal variation of Fe and Mn in the stormwater wetland]

To study the purification mechanism and biogeochemical cycle of wetlands, the concentration of Fe/Mn and oxidation reduction potential (ORP) in the pore water were monitored in situ on the Wuhan Zoo stormwater wetland from 2004 to 2006. The results showed that the water level of the wetland was changed from -10 cm to 30 cm, and the range of ORP was-120-220 mV. The elements of sulfur, iron and manganese were the main oxidation and reduction systems in the wetland. The ranges of total Fe, Mn and Fe2+ concentration were 0.60-2.35, 0.75-1.89 and 0.20-1.25 mg x L(-1), respectively. The concentrations of total Fe, Mn and Fe2+ were higher in spring and summer than that in autumn and winter, while the sulfate concentration was on the contrary and the ratio of Fe2+/Fe was slightly various in different seasons. From the surface of 10 cm to 50 cm underground, ORP and pH was decreased, whereas the concentrations of total Fe, Mn and Fe2+ were increased (except for the surface water). Through the correlation analysis, it was showed that the correlation of ORP and total Mn and Fe2+ was negative and significant, while there was no significant correlation between ORP and total Fe (R = -0.169, p < 0.0001). The order of the correlation coefficient was total Mn, Fe and Fe2+ in turn. Therefore, the systems of sulfur, iron and manganese were the important component of the oxidation and reduction system for stormwater wetland.