Mathieu Nsenga Kumwimba1, Bo Zhu2, Fidèle Suanon3, Diana Kavidia Muyembe4, Mawuli Dzakpasu5. 1. Key Laboratory of Mountain Surface Processes and Ecological Regulation, Chinese Academy of Sciences, 610041 Chengdu, PR China; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, 610041 Chengdu, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China; Faculty of Agronomy, Department of Natural Resources and Environmental Management, University of Lubumbashi, PO Box 1825, Democratic Republic of the Congo. Electronic address: kumwimbamatthieu@yahoo.fr. 2. Key Laboratory of Mountain Surface Processes and Ecological Regulation, Chinese Academy of Sciences, 610041 Chengdu, PR China; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, 610041 Chengdu, PR China. Electronic address: bzhu@imde.ac.cn. 3. Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. 4. School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, PR China. 5. Key Laboratory of Northwest Water Resources, Environment and Ecology, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Abstract
We evaluate the long-term performance of a vegetated drainage ditch (VDD) treating domestic sewage with respect to heavy metal/metalloid (HM/M) accumulation in sediments, plants and water. VDD sediment contained significantly higher macro and trace elements compared to an agricultural ditch (AD) sediment. However, concentrations of HM/Ms in VDD sediment were below the ranges considered toxic to plants. Most HM/Ms were efficiently removed in the VDD, whereby removal efficiencies varied between 11% for Al and 89% for K. Accumulation of HM/Ms varied among species and plant parts, although sequestration by plants represents only a small proportion (<1%) of the inflow load. Accumulation of Al, As, Cd, Pb, Cr, Fe and Ni in VDD plants were mostly distributed in the roots, indicating an exclusive strategy for metal tolerance. The opposite was found for Zn, Cu, K, Ca, P, K, Na, N and Mg, which were accumulated either in the stems or leaves. Overall, concentrations of metals in sediment showed significant positive correlations with those in ditch plants. None of the studied species were identified as metal hyper-accumulators (i.e. >10,000mgkg-1 of Zn or Mn). Nevertheless, the high translocation factor (TF) values for Mn, Ni, Cu, Zn, Na, Mg, P, K and Ca in the ditch plants make them suitable for phytoextraction from water/soil, while the low TF values for Pb, Cd, As, Fe, Cr and Al make them suitable for their phytostabilization.
We evaluate the lonpan>g-term performanpan>ce of a vegetated drainage ditch (VDD) treating domestic sewage with respect to heavy pan> class="Chemical">metal/metalloid (HM/M) accumulation in sediments, plants and water. VDD sediment contained significantly higher macro and trace elements compared to an agricultural ditch (AD) sediment. However, concentrations of HM/Ms in VDD sediment were below the ranges considered toxic to plants. Most HM/Ms were efficiently removed in the VDD, whereby removal efficiencies varied between 11% for Al and 89% for K. Accumulation of HM/Ms varied among species and plant parts, although sequestration by plants represents only a small proportion (<1%) of the inflow load. Accumulation of Al, As, Cd, Pb, Cr, Fe and Ni in VDD plants were mostly distributed in the roots, indicating an exclusive strategy for metal tolerance. The opposite was found for Zn, Cu, K, Ca, P, K, Na, N and Mg, which were accumulated either in the stems or leaves. Overall, concentrations of metals in sediment showed significant positive correlations with those in ditch plants. None of the studied species were identified asmetal hyper-accumulators (i.e. >10,000mgkg-1 of Zn or Mn). Nevertheless, the high translocation factor (TF) values for Mn, Ni, Cu, Zn, Na, Mg, P, K and Ca in the ditch plants make them suitable for phytoextraction from water/soil, while the low TF values for Pb, Cd, As, Fe, Cr and Al make them suitable for their phytostabilization.