| Summary: | As a result of damage caused during the First Gulf War in 1990-1991, the Kuwaiti environment suffered from drastic pollution caused by massive petroleum hydrocarbon contamination resulting from the destruction and burning of 700 oil wells across Kuwait. A range of types of polluted soils, including fresh oil lakes, dry oil lakes, and tarcretes, damaged desert wildlife. The idea of phytoremediaton using native plants was introduced and concluded that the native species Haloxylon salicornicum (Amaranthaceae) had potential as a phytoremediator. In the initial phase of this study a follow-up survey of clean and polluted sites in 7 areas in Kuwait was undertaken: Bahra, Sabah Alahmad protected area, Burgan oil field, Um Alaish oil field, Um Alrros Military Base, Sabriya oil field, and Um Ghadaier oil field where 41 plant species were found to be present. TWINSPAN classification of the dataset identified four assemblages of plant species, occurring in four ecologically-distinguishable habitat types (represented by 7 sample-groups produced by the classification procedure); one of them is mostly north of Kuwait where Sabah Alahmad protected area is and Bahra and Um Alaish oil fields and tends to be more in the oil damaged areas and characterized by the presence of the Haloxylon salicornicum; the other one is in both the north (Um Alaish oil field) and south of Kuwait (Burgan oil fields) and is characterized by the presence of both Cyperus conglomeratus and Rhanterium epapposum while the third and fourth assemblages can be mostly considered variant and characterized by the presence of Pennisitum divisum. These native species (former 3) were hence selected as the focus for subsequent investigation. The survival of Haloxylon salicornicum plants in weathered oil-polluted soils was experimentally investigated under greenhouse conditions, using a random block design with 4 replicates and 5 treatments: pots containing 100%, 75%, 50%, and 25% polluted soil, mixed with clean soil, and clean soil only as a control. The results indicated that the plants could grow successfully even in 100% oil-polluted soil. The experimental results also provided evidence that water applied to the surface (simulating rainfall) could reach the root system in all of the treatments (even for the 100% oil contamination treatment). Following on from the greenhouse study, a field trial was undertaken to examine the survival and growth of Haloxylon plants introduced into clean and oil-polluted soils (in and adjacent to a weathered dry oil lake) under field conditions. Three replicate two-year old iii (nursery-grown) Haloxylon plants were planted at each randomly-chosen location in the dry oil lake soil, and the design was repeated at 10 random locations in clean soil close to the lake boundary. The experiment was set up in two different locations (Bahra area in the north; and in Burgan oil field in the south of Kuwait). there was no significant difference in growth rates between plants in clean and polluted soil, in either area. The biomass data showed a significant difference in fresh weight between plants from clean and polluted soils, with those growing in clean soil having higher moisture content (possibly less woody than those from the polluted sites). However there was no significant difference in either fresh or dry biomass between the two experimental areas in the north and south. Data produced by analysis of amount of TPH in the polluted soils in both experimental areas showed some variability, but overall there was no significant difference between the two polluted areas, in terms of their weathered petroleum hydrocarbon content. Successful phytoremediation usually, if not always, is a function not only of phytoremediator plant physiology, but also the activity of the phytoremediator species associated rhizosphere microflora. In order to gain some insight into the hitherto unknown rhizosphere microflora of Haloxylon salicornicum plants, bacterial and fungal isolation procedures were carried out on samples taken from the roots of wild Haloxylon salicornicum plants, and from cultured plants growing in oil-contaminated soils in the greenhouse experiment, using media enriched with petroleum hydrocarbons to encourage the culture to survive in such conditions. Bacteria organisms found to be associated with the rhizosphere of wild Haloxylon are Streptomyces spp. and Inquilinus sp., while in 100% oil contaminated soil Rhodococcus manshanensis, Agrobacterium tumefaciens, Nocardia cyriacigeorgica, Gordonia lacunae / Gordonia terrae and Lysobacter spp., occurred. In the 50% oil contamination treatment soil, around the roots of Haloxylon plants contained Gordonia lacunae / Gordonia terrae and Agrobacterium tumefaciens and finally the clean soil Sphingopyxis spp. was present. Fungi found in the Haloxylon rhizosphere included organisms known to be associated with petroleum hydrocarbon degradation, including Penicillium spp. in wild Haloxylon (and also 50%, 100% and clean soil from the greenhouse trial), as well as Trichoderma asperellum in the clean soil. The conclusion is that Haloxylon salicornicum, together with its rhizosphere microflora it contain, offers high potential for use in phytoremediation operations designed to assist in the clean-up of oil polluted desert soils in Kuwait.
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