ACCUMULATION OF HEAVY METAL IN GRASS AND VEGETABLES

The demand for natural resources has continued to grow in line with human economic development and global population growth. Unfortunately, the exploitation of natural resources, especially when using mining processes, has numerous unintended environmental consequences. In previous studies, we investigated the occurrence of lead in soils, plants and water in Kabwe, one of the Zambian mining towns with widespread lead pollution. We had also investigated the ability of certain vegetables (Chinese cabbage, Brown Mustard and Mizuna Mastard) to absorb lead from soils. The results showed significant levels of lead in the environment near the old lead and zinc mine. Vegetables such as Chinese cabbage absorbed relatively high amounts of lead from the soils. These results have escalated concerns about the health of the people and the environment in this town and other areas with similar problems. In response to these concerns, best management practices for reducing human and animal exposure to lead and other heavy metals are being investigated. This study looks at grass as a possible remedy for reducing exposure through dust as well as a way for removing some heavy metals from the soils. This project, therefore, investigates the ability of grass and other vegetables to accumulate heavy metals such as copper, chromium, lead, zinc and manganese. Some of the grass and vegetables studied were grown in a controlled setting with soils that were treated with 400 ppm of lead and controls that were not treated. The other plant samples were collected in Kabwe where they were grown by the local farmers and residents. Preliminary results show slight accumulation of lead, up to 33 ppm of lead in the grass, and significant bioaccumulation of manganese and zinc in the lab-grown grass. No detectable levels of other metals were observed in the grass, despite them being present in the soils.