study of the effects of sulfur and citric acid amendment on phytoextraction of cd and pb from contaminated soil

abstract the use of plants to remove contaminants from the environment and concentrate them in above-ground plant tissue is known as phytoextraction. this study was conducted to investigate the potential of phytoextraction of pb and cd metals canola (brassica napus) and sorghum (sorghum bicolor) which are high biomass crop and the effect of amendments on the efficiency of phytoextraction. the soil sample for the experiment was collected from an area adjacent to a zinc concentrate factory in west of zanjan, iran. five treatments compared included powdered sulfur, sulfur plus thiobaccilus inucolum (s+i) at 8g kg -1 rate, citric acid at two levels of 1g kg-1 (ca1) and 3g kg-1 (ca2) and the control (c). the experiment was conducted in two stages. in the first stage of study, the treated soil with the above material were incubated for 8 weeks at field capacity and 25˚c temperature. in the incubation period the subsamples were collected at 0, 4 and 8 weeks to determine the amount of plant available pb and cd using dtpa extraction. in the second stage, a greenhouse experiment was conducted using the same soil and treatments. sorghum and canola were planted and grown for 60 days and then the above ground parts and roots were harvested. plant samples were analyzed for cd and pb content and the amount of dtpa exractable pb and cd were measured in soils before and after planting. both experiments were conducted in the factorial experiment with randomized complete design with 5 treatments (including control) and 4 replications. the statistical analysis was done using sas and mstatc softwares. the resulst indicated that effect of sulfur plus thiobaccilus and citric acid at 1g.kg-1 treatments on cd and pb availability were highest and lowest, respectively. the pot experiment showed that the best of amendment in transfer of metal from root to shoot for two plant species was powdered sulfur plus thiobaccilus inucolum. the results of greenhouse experiment indicated that canola has higher potential for remediation of cd and pb from contaminated soil in comparison with sorghum.