Abstract
In Egypt, Lake Manzala is the largest and the most polluted lake due to its use as sink for agricultural drainage, industrial effluents, and sanitary wastes. Pollution indices and associated bacteria of Arthrocnemum macrostachyum were assessed in up and down streams. The concentrations of heavy metal in upstream soil significantly exceeding those in downstream. The highest concentration in upstream soil was recorded by Fe (> 200000 mgkg-1), followed by Al, Mn and Zn (143733.3, 5032.67 and 1036.43 mgkg-1, respectively). Concerning the plant organs, the levels of all elements in root were higher than those in shoot at both up and down streams. The pollution indices of upstream soil were higher than those of downstream for all metals except for Mo. A. macrostachyum has the ability as hyperaccumulator for Al, Fe and V in both up and downstreams and for Cr and Cu in downstream. Plant juice culture media of the halophyte was succeed to develop translucent and slimy colonies. More than 50% of plant juice culture media diluted with upstream water isolates were tolerant to Al, Cr, Cu and Zn at maximum tolerable concentrations 71.26, 12.5, 0.32 and 0.74 mM, respectively. Nine heavy metal-tolerant bacterial isolates were identified according to API microtube systems. Four isolates were matching Burkholderia cepacia, 2 isolates belonged to Providencia retgeri, and the rest isolates referring to Bacillus circulanc, Bacillus lentus and Raoultella ornithinoltica. The study suggests that A. macrostachyum could be classified as an appropriate candidate for phytoremediation efficiency of extremely heavy metal polluted soils.
Highlights
Several heavy metal ions and metalloids such as copper, manganese, iron and zinc play significant roles as cofactors for many enzymes and are essential components of living organisms
Results indicated that the metal load, in general, was sampling site-dependent where soil taken from upstream area contained extraordinary levels compared to the downstream
The higher concentrations of all measured heavy metals in A. macrostachyum roots of upstream in comparison with their counterparts of downstream could be due to nearby effluents from Bahr El Baqar drainage which is the main source of pollutants and heavy metals in lake Manzala [22,26,55]
Summary
Several heavy metal ions and metalloids such as copper, manganese, iron and zinc play significant roles as cofactors for many enzymes and are essential components of living organisms. Identification of biota that are adapted to both salinity and heavy metals stress is essential to bioremediation of contaminated habitats especially in arid and semi-arid regions. In this respect, halophytic plant species and their associated bacteria are receiving increasing attention for bioremediation of the highly contaminated heavy-metal sites [12,13]. The role of halophytic plantassociated bacteria in removal of heavy metals is confined to their unique properties and metabolic activities [15,16]
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