Masters Thesis

The effectiveness of using Typha latifolia (broadleaf cattail) for phytoremediation of increased levels of lead-contamination in soil

In this study, two ways of accumulating Pb were investigated: natural accumulation and chemically enhanced accumulation with the chelating agent ethylenediaminetetraacetic acid (EDTA). Young cattails (Typha latifolia) were removed from the Arcata Community Pond in Northern California and transplanted into two-quart mason jars containing four different levels of Pb contamination: 0, 2000, 4000, and 6000 mg Pb/kg soil. Three cattails per jar were grown for a three-week period with half of the plants receiving 10 mmol EDTA on the 15th day of the experiment and allowed to continue growth for the remaining 6 days of treatment. Cattails were harvested, separated into shoots, rhizomes and roots, and then analyzed for Pb concentration in these tissues using Atomic Absorption Spectrophotometry (AAS). For the natural accumulation of Pb, no significant differences among the 2000, 4000, and 6000 mg Pb/kg groups for shoots (p = 0.1063), rhizomes (p = 0.1096) or roots (p = 0.2526) were detected. When EDTA was added to the soil, there was a significant difference among the various levels of soil contamination (p = 0.0002). In this particular case, the largest accumulation of Pb occurred at the 4000 mg Pb/kg soil contamination level with shoots accumulating a combined average of 4744.03 mg Pb/kg. These results show that three cattails can remove Pb from the environment in larger quantities if a chelating agent is present in a short period of time. In addition, it appears that the 6000 mg Pb/kg soil contamination is a threshold of toxicity as all aspects of the experiment showed a decrease in the health, natural accumulation of Pb, and the accumulation of Pb with the addition of EDTA. Typha latifolia has a wide tolerance to many different environments and produces a large amount of biomass, which make it a good candidate for use in phytoremediation. Further research should consider increasing the quantity of cattails to optimize Pb removal from the soil.

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