Acceleration of Lead Phytostabilization by Maize (Zea mays) in Association with Gliricidiasepium Biomass
Abstract
Soil where shooting practices are conducted is extremely contaminated with heavy metals, exclusively by Pb, due to the bullets and bullet f ragments. These extreme concentrations of Pb, generate an unfavourable surroundings for agriculture and human health through phytoaccumulation. This study was conducted to assess the possibility of particular bio-amendment, phytostabilization on the reduct ion of bioavailable Pb in such contaminated soil. Biomass (BM) produced from Gliricidiasepium was used to see its ability to be used in soil remediation together with Maize (Zea mays) as phytostabilizer. A pot experiment was conducted with Maizeby adding B M at three different percentages, 1, 2.5 and 5% (w/w). Soil without amendments served as the control and arranged in a complete randomized design. By maize, translocation rate of heavy metals into crop were determined. After sixth week, grown maize were ha rvested and analyzed followed by digestion with con.HNO 3. The most significant immobilization (p<0.05) was indicated by treatment 5% BM for Pb than control. Metal translocation towards plant decreased with increasing application rate of soil amendment,Glir icidia woody BM. Determination of Plant factor (PF) and Translocation factor (TF) indicates that PF>TF in maize. For the treatment 5% BM, PF and TF for Pb are 1.22 and 0.15 respectively. Thereby maize can be considered as a potential phytostabilizer. At th e same time efficiency of phytostabilizing nature of maizecan increase together with the application of soil amendment – BM.
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Introduction
Soils polluted with heavy metals have become common across the world due to increase in geologic and anthropogenic activities [1]. Some of these happenings include mining and smelting of metals, burning of fossil fuels, use of fertilizer and pesticide, exhaust of auto mobiles and effluent from battery industries [2, 3]. Some heavy metals such as Co, Cu, Fe, Mn and Zn are required in minute quantities by organism; however, excessive amount of these elements can become harmful to organism. Other heavy metals such as Pb, Cd, Hg and As don’t have any beneficial effect on organism and are thus regarded as the keypressures since they are very detrimental to both plant and animal [3, 4].
Lead is a non-essential water soluble heavy metals that contaminates food chain by phytoaccumulation in plant parts as it is easily mobile in soil and bioavailable eventually transisting and accumulating in top consumers of food chain i.e. human. Pb backlog in environment causes harmful effects to both plants and animals. Plants growing on these soils show a reduction in growth, performance and yield [1]. This has been recorded by Oancea[5]. So the problems which are raised by the contamination of heavy metal in the eco system can be partially solved by the approaches of bioremediation technologies. It is an economically feasible method when associate with other treatment systems[6]. In recent times, phytoremediation act as an emerging technology, which involves rising of plants in metal polluted soil [7].
This phytoremediation mechanism includes phytoextraction, phytostabilization and phytovolatilization[1]. Plants which act as phytostabilizers accumulate metals in roots than plant shoots [6]. The efficiency of phytostabilization depends on the plants used together with soil amendments [1]. Biomass (BM) of Glirecidiasepium as soil amendment, which is easy to handling, inexpensive, and most importantly aren’t toxic to plants and eco system.
Thereby, the objective of the study was to explore the potentiality of Maize (Zea mays) as phytostabilizer together with soil amendment - GliricidiasepiumBM to clean the agricultural sites which are affected by Pb contamination.
Conclusion
Maize has been renowned as a best phytostabilizer to enhance the quality of soil, which is severely affected by accumulated Pb.Results of the presence study suggest that maize has the potential to remove the metal Pb from contaminated site significantlytogether with the application of BM as soil amendment. BM affects the behavior of Pbin contaminated soil by altering their solubility and availability. BM, which was ap plied at the rate of 5% was the most effective amendment when compare to other application rate of BM – 1% and 2.5%. Maize which was grown together with 5%BM had higher PF than TF. These resultsindicate that maize + 5% BMare the best treatment of phytostab ilization to eradicate the metal concentration from contaminated site. These types of treatments can be carried out in field level to enrich the quality of affected soils i n Sri Lanka. Furthermore, additional studies should be designed to get maximum posit ive result by increasing the application rate of BM above 5% together with Maize .
