PERFORMANCE OF VARIOUS TREE SPECIES AS IRRIGATED BY URBAN WASTEWATER

Abstract

The Research work was designed to determine growth behaviour and to assess the potential of various tree species for uptake of heavy metals under different irrigation regimes. Domestic wastewater (DW) accelerated the growth of almost all the species. Municipal wastewater (MW) irrigation was the second best in this regard. Tree heights gained by the tree species under MW irrigation were 8% less than DW followed by canal water (CW) (25% less). Similarly, collar diameter of all the species under MW irrigation was 10% less than the diameter gained under DW irrigation (7.41cm) but greater than CW (23% less). Relatively smaller collar diameter under MW might be due to stress of some metal contamination found in it. Maximum diameter under DW was due to highly favourable status of nutrients, organic matter and moderate level of pollutants. Almost all of the tree species showed higher uptake of metals under MW irrigation followed by DW. Metal uptake by the tree species under CW irrigation was significantly low. However, Ni uptake was maximum under DW followed by MW irrigation. Populus deltoides (38.95 mg kg -1 ) and Dalbergia sissoo (29.70 mg kg -1 ) efficiently absorbed Cd metal. Leucaena leucocephala and Albizzia procera absorbed 66 and 70% less Cd than Populus deltoides, respectively. Melia azedarach and Eucalyptus camaldulensis had 22.3 mg kg -1 and 20.16 mg kg -1 Cd, respectively. P. deltoides, A. procera and M. azedarach proved to be good absorbents of Cr. However, E. camaldulensis (~53% less uptake), L. leucocephala and D. sissoo (73% less uptake) were poor in this regard. Cu concentration was highest in P. deltoides (245.45 mg kg -1 ). The performance of M. azedarach and A. procera (61% and 59% Cu uptake) was quite reasonable. The rests of the species were not very active to absorb Cu. Tree species like P. deltoides, M. azedarach and A. procera were efficient absorbents of Ni. All other species had negligible absorption of Ni from soil and water mediums. P. deltoides was most effective in Pb uptake followed by D. sissoo. A. procera and M. azedarach performed moderately in this regard. Data revealed that L. leucocephala remained Pb free under each irrigation source. The results suggested that L. leucocephala was suitable for forage purpose as it was free from Pb causing low risk to animal health. A. procera, M. azedarach and P. deltoides captured more Zn than all other species.