Lead cycling in a simulated wastewater-affected mangrove(Avicennia marina) wetland system
CHEN Gui-kui1, CHEN Gui-zhu2
1. College of Agriculture, South China Agricultural University, Guangzhou 510642, China; 2. Institute of Environmental Science, Zhongshan University, Guangzhou 510275, China
A greenhouse experiment was conducted to investigate the cycling of lead in an artificial mangrove wetland system receiving Pb-containing "wastewater". Avicennia marina was selected as the only tested mangrove plant species, which grew in tanks containing soils collected from a mangrove tidal wetland in Shenzhen, South China. Artificial seawater with salinity of 15‰ was pumped into and out of the tanks at regular intervals to simulated semi-diurnal tidal conditions. Synthetic wastewater containing various levels of lead (control, NW, FW and TW) was discharged into the artificial wetland twice a week for a year. The results show that large amounts of lead in the "wastewater" were removed by the soil after entering the artificial wetland system and the amount of soil-retained lead increased with increasing content of lead in the importing wastewater although the amount of lead remained in the artificial tidal water also increased with increasing content of lead in the importing wastewater. In general, the concentration of lead in roots is higher than it in stems and leaves. The study demonstrated that artificial wetland system had high efficiency to remove lead from the synthetic wastewater. The removal rates were 97.97%,97.86% and 98.06% for treatments NW, FW and TW, respectively. As the environmental capacity of lead in soil subsystem is calculated according to the model of matter balance, the simulated wetland has a high capacity for bearing the heavy metal pollution of lead, which has implications for the management of wastewater using mangrove wetlands.
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