Ecology of Iranian Forest

Introduction and objective: Today, Metropolises require more green space because of air pollution, but water scarcity in aried areas  should lead to irrigation of unconventional sources such as wastewater, which due to the contamination of these sources, tree species with high phytoremediation capability should be used.

Materials and methods: In this study, two-year-old seedlings of four species of Judas Tree (Cercis siliquastrum L.), Arborvitaes (Thuja orientalis L.), Persian Lilac (Melia azedarach L.) and White Mulberry (Morus alba L.) were planted in pots and were irrigated with Tehran West Water Treatment Plant effluent which contained manganese and chromium from March to October 2017. 

Results: The amount of chromium and manganese in the organs of species irrigated with effluent showed a significant increase compared to ordinary water. All four species irrigated with water treatment plant effluent showed a same growth compared to ordinary water. The highest amount of manganese was in leaf and chromium in root of all four species. The lower than one BCF and more than one TF for manganese in all four species indicated that they were not suitable for phytostabilization of this metal, but all four species (Cercis siliquastrum L.) (1.87), (Morus alba L.) (2.07), (Thuja orientalis L.) (1.96) and (Melia azedarach L.) (1.83) with a more than one TF are suitable for manganese phytoextraction. However, because BCF in them is lower than one, further investigation is needed. White mulberry and Persian lilac with a lower than one BCF and TF for chromium indicated that none of them were suitable for chromium phytostabilization and phytoextraction; But both Judas tree (1.39) and arborvitaes (1.04) with higher than one BCF and lower than one TF for chromium were appropriate to phytostabilization of this metal.

Conclusions: As a result, Judas tree and arborvitaes, which have both the ability to phytostabilization chromium and the ability to phytoextraction manganese, are the best species for the phytoremediation of these two elements in soil irrigated with effluent. Equal growth parameters of all four species after irrigation with this effluent indicated that reuse of Tehran West Water Treatment effluent can be an approach to compensate water scarcity but further studies and monitoring of conditions in order to select the most suitable species for phytoremediation of heavy metals as well as long-term effects of irrigation with effluent, are required.