Interactions of copper and pyrene on phytoremediation potential of Brassica juncea in copper-pyrene co-contaminated soil.

Phytoremediation which is a plant based remediation process is an emerging technology for treating inorganic (heavy metals) as well as organic pollutants. It may also be suitable for remediation of sites co-contaminated with heavy metals and organics which have become more prevalent. A glasshouse experiment was carried out to investigate the effect of 50 and 100 mg kg(-1) of copper or 250 and 500 mg kg(-1) of pyrene and the combined effect of copper and pyrene on the growth of Brassica juncea together with the uptake and accumulation of copper as well as dissipation of pyrene. Results showed a negative effect of copper-pyrene co-contamination on shoot and root dry matter and an inhibition of copper phytoextraction. Pyrene was significantly decreased in planted and non-planted soils accounting for 90-94% of initial extractable concentration in soil planted with B. juncea and 79-84% in non-planted soil which shows that the dissipation of pyrene was enhanced with planting. The occurrence of copper tended to increase the residual pyrene in planted soil, however in the presence of high concentration of Cu (100 mg kg(-1)), the residual pyrene concentration in soil were similar to those in unplanted soil. This may suggest that changes in the root physiology or rhizospheric microbial activity resulting from Cu stress could be an impediment to pyrene dissipation. The inhibition of Cu phytoextraction and degradation of pyrene by B. juncea under co-contamination may reduce the viability of phytoremediation in sites containing multiple pollutants.