Horizontal Distribution of Cadmium in Urban Constructed Wetlands: A Case Study

Abstract

Here, we used a radioactive distribution approach for water samples from the Liu Shao Yan constructed wetland to investigate the horizontal advection of cadmium (Cd) in this urban constructed wetland. The objective of this study was to assess the effectiveness of Cd removal in constructed wetlands. Additionally, this study examined the factors affecting the horizontal distribution of Cd. Sediment samples were collected from an enclosed wet area. A predictive advection model was executed using a combination of observed Cd concentrations and predicted Cd concentrations from a genetic algorithm–backpropagation artificial neural network (GA–BPANN). A coefficient of variation was used to assess differences in Cd distribution due to flow rate, precipitation, and water plants. Scanning electronic microscopy–energy dispersive spectrometry (SEM–EDS) results suggested that the plant species Pontederia cordata could absorb Cd, but the influence was negligible. All plants investigated in our experiment were unsuitable for Cd removal. However, predictions from the GA–BPANN algorithm indicated that 13–25% of Cd loading was efficiently removed by constructed wetland, which mainly resulted from sediment sorption, bacterial uptake, and the dilution caused by water advection. Consequently, we conclude that the constructed wetlands are an environmentally friendly and cost-effective technology that can remove Cd to a certain extent.