Investigation on effect of forest plantation of fast growing species of eucalypts at southern provinces of Iran in reducing pollutants caused by Pesian Gulf War

After the Persian Gulf War in 1990 and after the wide Kuwaiti's oil well fire, huge amount of soot, toxic gases and raw oil material spread out by winds, sea waves and acidic rains to Iran and contaminated huge lands, particular southern and south western parts of it. The most important substances made by the oil well fires, are: Ni, V, Fe, Al, Be, Cd, Ca, Cr, As, Se, Ze, and Pb, which are known as toxic and harmful elements. Trees as alive components of an ecosystem are able to convert some of these contaminants to unharmful substances and store some of them in their tissues and reduce their density and intensity in the air and soil by breath, root absorption and photosynthesis and other biotic functions. Trees function in such condition is completely related to environmental and habitat circumstances and their physiological potential. Trees resistance to different contaminants is an important key for their successful in such environments. If a tree was able to survive in a contaminated environment and tolerate the stresses caused by unbalanced environment surrounding the leaves and the roots and continue its biotic performances, could play a good role in reducing the pollutants. At beginning, five research sites at Khuzestan and Bushehr provinces were selected among the contaminated area by the Gulf War. At each site, soil sampling was made from three levels of depth (0-20, 20-40 and 40-60 cm). Soil physical and chemical characteristics test was made to measure Ca, Cd, Cr, Fe, Ni, Pb, V, Zn, N, P, K, Na, OM, pH, EC, pb (soil partial density) and texture. The eucalypt species consisted of: E. camaldulensis, E. camaldulensis 9616, E. microtheca and E. sargentii which were planted under the Randomizes Complete Blocks statistical design with three replicates. Before sampling the trees for determining the contaminant elements, their total height, breast height diameter (DBH), collar height diameter, canopy diameter and freshness were measured. Three individual trees were selected at each plot per one replicate to make sampling for wood sampling (at breath and collar height of a stem) and leaf (four specimens per tree at four mean geographical directions). The data were analyzed under the variance analysis and Duncan test programs, using Excel and SAS computer soft wares. The amount of the contaminants of the soils in 2005 (The date of soil sampling) was very low and mostly less than one mg/kg, except Ca which varied between 94.4 and 174.9 mg/kg. Actually the Ca element was not too high to poison the soils. Overall, amount of the contaminants in different sites and at three levels of depth was not significantly different. Amount of the pollutants in the stem's wood unit was greater than that in the soil unit, but it was less than the standard level and it was not harmful and poisonous for the trees. The wood data indicate a greater amount of the contaminants at past time in the environment which were absorbed by the trees. The pollutant elements in the leaves and at different sites were unbelievable ten time and sometimes thousand time of that in the wood. The significant effect of the interaction between sites and species, shows that the role of the species in absorbing the contaminants is not similar at different sites and it differs due to environmental variation, particularly soil type. The eucalypts wee able to absorb a large amount of the contaminants which differ largely from their amount in the soils in 2005. This is might be a good indicator of the huge absorption of the contaminants at the beginning of the eucalypt plantation in 1990. The best eucalypt species and the best sites for absorbing the contaminants in their leaves are respectively as follows: 1- E. camaldulensis, E. microtheca, E. sargentii and E. camaldulensis 9616 2- Dezful, Isvand, Shooshtar, Karkheh and Kaki. ۵۳ Actually, they also indicate their resistance to pollution and their capacity to absorb the pollutant and store them in their tissues. The species which made the best performance in relation to their site interaction are respectively as follows: 1- E. microtheca firstly at Karkheh and shooshtar sites and secondly at Dezful and Isvand sites. 2- E. camaldulensis 9616 3- E. camaldulensis and E. sargentii.