Development of a Low Cost Remediation Method for Heavy Metal Polluted Soil

Sammanfattning: High concentrations of heavy metals in the soils have potential long-term environmental and health concerns because of their persistence and accumulation tendency in the environment and along the food chain. This study was aimed at studying the feasibility of heavy metals removal from the soil using plants naturally growing in the surroundings of selected polluted sites in Tanzania and soil application of the sorbent materials zeolite and autoclaved aerated concrete (AAC). The results showed thatSporobolus sp. is a hyperaccumulator of Cu. Four other species, Launea cornuta (Oliv & Hiern) O. Jeffrey, Tagetes minuta (L.), Sporobolus sp. and Blotiella glabra (Bory) Tryon showed high potential for phytoextraction of Cu. No hyperaccumulators of Pb and Zn were identified in the area, but Tephrosia candida and Tagetes minuta (L.) were identified as potential plants for phytoextraction of Pb, while Conyza bonariensis (L.) Cronquist, Launea cornuta (Oliv & Hiern) O. Jeffrey, Tagetes minuta (L.), Blotiella glabra (Bory) Tryon, Pteridium aquilinum (L.) Kulm and Polygonum setogulum A. Rich were identified as potential plants for phytoextraction of Zn. The result from sorbent experiments showed that both materials had a potential for remediating metal polluted soils. The AAC had a higher removal capacity for both Zn and Pb than zeolite. The removal capacity of zeolite and AAC in a mixed metal experiment (Pb and Zn) showed a little difference in the sorption capacity of AAC and Zeolite for Pb and Zn respectively. Speciation of the metal in soil shows that the major part of the metal was associated with firmly attached component of the metal in the soil. Compared with the total metal concentration analysed, the available component accounted for 13-39% for Zn and 31-39% for Pb. It can be suggested to co-remediate polluted soils using reactive sorbent nodules and hyper-accumulating plant species. Identification of the best combinations and designs remains the subject of future research.