Poplar trees for phytostabilization of abandoned Zinc-Lead smelter

Abstract

Poplar trees represent one vegetation option for phytostabilization of heavy metal-contaminated sites. The objective of this study was to investigate the suitability of deep-planted poplars for phytostabilization of a heavy metal-contaminated site. Tree survival was greatly improved when trees were planted using cattle manure as a soil amendment as compared to no amendment. Survival after 3 years with manure ranged from 18 to 56% for four poplar hybrids, while without manure, the range was 0-18%. Increases in trunk diameter and tree height were also greater with manure than without after the first growing season. Zinc, Cd, and Pb concentrations were as high as 3,606, 44, and 33 mg kg, respectively, in leaves, and there was little influence of manure amendment or hybrid. Zinc phytotoxicity may have been a factor in tree survival. Average metal concentrations in plant tissues followed the order: leaves>bark >twigs>wood for Zn and Cd, and bark>wood>twigs ≅ leaves for Pb. Manured treatments supported higher rates of both photosynthesis and transpiration. Comparisons among varieties indicated that DO1 and Imperial Carolina hybrids had more than twice the rates of photosynthesis of the other two hybrids and that each variety was unique in terms of water-use efficiency (WUE), with Imperial Carolina being higher than any other hybrid. This combination of high rates of photosynthesis and high WUE suggests a unique suitability of this hybrid for remediation of this site. More extensive characterization of the hybrids under a variety of conditions, including drought, is likely to reveal more about inherent suitability of each hybrid for site-specific remediation.