Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances parti...Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances partition strongly to organic particulate matter. In order to evaluate this premise, the study investigated the organic matter, pesticides and PCBs content in wastewater and in soil within the reed beds, in their entry, middle, and exit-part areas in a full-scale operating subsurface-flow （SSW） constructed wetland （CW） in Poland. It is found that chlorinated pesticides such as 2,4＇dichlorodiphenyltrichloroethane （2,4＇DDT）, 4,4＇dichlorodiphenyldichloroethylene （4,4＇DDE）, hexachlorobenzene （HCB）, as well as PCBs in the wastewater. In the entry-part area of reed beds, nearly all of the pesticides and PCBs content in the wastewater had been removed by soil. The level of contamination by these compounds declined with increasing distance from the point of discharge of the wastewaters into the reed beds, as well as downwards through the soil profile from the surface into the deeper layers. Vertical distributions of pesticides and PCBs content were proportional to the organic carbon content in the soil. It is therefore concluded that reed beds act as a trap for pesticides and PCBs, and thus can provide a very effective mechanism for their removal from wastewater.展开更多
文摘Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances partition strongly to organic particulate matter. In order to evaluate this premise, the study investigated the organic matter, pesticides and PCBs content in wastewater and in soil within the reed beds, in their entry, middle, and exit-part areas in a full-scale operating subsurface-flow （SSW） constructed wetland （CW） in Poland. It is found that chlorinated pesticides such as 2,4＇dichlorodiphenyltrichloroethane （2,4＇DDT）, 4,4＇dichlorodiphenyldichloroethylene （4,4＇DDE）, hexachlorobenzene （HCB）, as well as PCBs in the wastewater. In the entry-part area of reed beds, nearly all of the pesticides and PCBs content in the wastewater had been removed by soil. The level of contamination by these compounds declined with increasing distance from the point of discharge of the wastewaters into the reed beds, as well as downwards through the soil profile from the surface into the deeper layers. Vertical distributions of pesticides and PCBs content were proportional to the organic carbon content in the soil. It is therefore concluded that reed beds act as a trap for pesticides and PCBs, and thus can provide a very effective mechanism for their removal from wastewater.
