MOBILIZATION AND TRANSLOCATION OF SUBSURFACE LEAD BY TITHONIA ROTUNDIFOLIA

In countries that are heavily dependent on mining and metal processing, widespread heavy metal contamination is a serious concern. Human exposure to high concentrations of heavy metals, like lead, can cause severe health problems and in some cases death. One contaminant of global health and environmental concern is lead, which can affect soil, air, water, vegetation and people in the area near former and active mining/industrial sites. People living in contaminated areas are at high risk of heavy metal exposure in their daily lives, which can be exacerbated by plants mobilizing the metals in the soil and bringing them to the surface. When the metals are brought to the surface they can easily contaminate the dust, which is one of the major human exposure pathways. This study investigates the ability and capacity of Tithonia rotundifolia to move lead from soils and soil water below ground to the surface. Tithonia rotundifolia was grown in a greenhouse and contaminated with lead through contaminated soils or by watering with a liquid lead nitrate solution. Preliminary results show lead concentrations in the stems ranging from 20 to 172 ppm with an average of 100 ppm. Lead concentrations in the leaves ranged from 7 to 121 ppm with an average of 37 ppm. Concentrations in the flowers ranged from 0.8 to 1 ppm with an average of 0.89 ppm. The seeds had lead concentrations ranging from 1.7 to 10.4 ppm with an average of 4.78 ppm. These results show a significant amount metals being translocated by the plants. The role of plants should, therefore, be considered when attempting to reduce heavy metal exposure in heavily contaminated areas.