International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2012/4-20/1523-1530 ISSN 2227-670X ©2012 IJACS Journal
Phytoremediation potential of three plant grown in monoculture and intercropping with date palm in contaminated soil Mohebbi. A, h1. harutyunyan. S, s2. chorom. M3. 1. Phd student at agrarian state armenia university 2. Professor at agrarian state armenia university 3. Professor at shahid chamran university *Corresponding Author email:
[email protected] ABSTRACT: High levels of heavy metals in soil can be phytotoxic. Poor plant growth and soil cover caused by metal toxicity can lead to metal mobilization in runoff water and subsequent deposition into nearby bodies of water. In such conditions goal of remediation is to reclaim the site by establishing a vegetative cover to minimize soil erosion and pollution spread. Some of plants extract large concentrations of heavy metals into their roots, translocation the heavy metals to surface biomass. The aim of this study was to evaluate the removal of heavy metals viz; Cd, Cu, Pb, and Mn by root and shoot of different plants in monoculture and diculture. Alfalfa, sunflower and maize were sowed with or without date palm for the natural heavy metals hyper accumulation. Total concentrations of heavy metals in the soils, root and shoot were determined. The results showed copper and manganese in root and shoot did not change statistically differences. Sunflower had more transport pb from root to shoot than alfalfa and maize. Alfalfa with or without date palm had potential to accumulate Cd. All the treatments showed very high BCF values for Cu and Mn which was indicating these treatments retains metals in their roots and limit metal mobility from roots to shoots. Keywords: phytoremediation; translocation factor
heavy
metals;
remediation
factor;
bioconcentration
factor;
INTRODUCTION Heavy metal pollution has become one of the most serious environmental problems today (Annenkov, 1982). There are a great numbers of small industrial plants and other sources of heavy metals emitting source in Khuzestan provinces of Iran (Archer, and Caldwell. 2004). Heavy metals and metalloids are an increasing environmental problem worldwide. Some industrial activities and agricultural practices increase their level in the substrate, and the possible introduction of these elements in the food chain is an increasing human health concern (Baker, et al. 2000). Engineering techniques may efficiently be used to clean up contaminated soils but most of them require sophisticated technology and are expensive and suitable only for small, polluted areas (Bibi, et al, 2008). Phytoextraction implies the use of plants to remove pollutants from the environment and has been proposed as an interesting alternative solution for the decontamination of large areas (Blaylock and Huang, 2000 and Blaylock et al 1997). Metals are natural components in soil. Contamination has resulted from industrial activities such as mining and smelting of metalliferous ores, electroplating, gas exhaust, energy and fuel production, fertilizer and pesticide application, and generation of municipal waste. One of the greatest concerns for human health is caused by Pb contamination. Exposure to Pb can occur through multiple pathways, including inhalation of air and ingestion of Pb in food, water, soil, or dust. Excessive Pb exposure can cause seizures, mental retardation, and behavioral disorders. The danger of Pb is aggravated by low environmental mobility, even under high precipitations. Many plants accumulate Pb in roots, but Pb translocation to shoot is very low. Blaylock and Huang concluded that the limiting step for Pb phytoextraction is the long-distance translocation from roots to shoots (Brooks, 1998). Under
Intl J Agri Crop Sci. Vol., 4 (20), 1523-1530, 2012 chelate-induced conditions, maize and Indian mustard have been successfully used to remove Pb from solution culture and contaminated soil, respectively (Brooks, et al 1998). Discovery of hyper accumulator species has further boosted this technology. In order to make this technology feasible, the plants must extract large concentrations of heavy metals into their roots, translocation the heavy metals to surface biomass, and produce a large quantity of plant biomass. The removed heavy metal can be recycled from the contaminated plant biomass. Factors such as growth rate, element selectivity, resistance to disease, method of harvesting, are also important (Chunilall, et al. 2005). Phytoremediation is defined as the use of green plants in removing pollutants from the environment. Phytoremediation is one of the promising methods for reclamation of soils contaminated with toxic metals by using hyper accumulator plants (Cui, et al. 2007, Cunningham, and Ow, 1996). More than 400 plant species belonging to 45 plant families have been identified and reported from temperate to tropical regions with the ability to tolerate and hyperaccumulate heavy metals. These plants have been considered suitable for soil stabilization and extraction of heavy metals (Del Río-Celestino, et al. 2006). Hyper accumulator plants can play a key role in the fate of the pollutants of contaminated matrixes via their root systems. Python extraction Python extraction refers to the use of metal-accumulating plants that translocate and concentrate metals from the soil in roots and above ground shoots or leaves. It has been used effectively by Phytotech at brown fields' sites with relatively low level lead and cadmium contamination for soil remediation to below action levels (Ghosh and Singh, 2005). Intercropping Intercropping as defined a system with two or more different crops (annual or perennial) grown together on the same land during a single time period. This practice is traditional in the tropics and is starting to be used under temperate climates for environmental purposes. Intercropping can aim to take advantage of the association between leguminous and non-leguminous to optimize the available resources, covering the bare-soil spaces inbetween trees to limit erosion, modifying the main crop microclimate or extending the period of soil cover to limit nitrate lixiviation (La´zaro, 2006). Willey and Osiru reported an increase in gross productivity per hectare within intercropping system. Reasons for the increased crop yield intercropping systems may be summarized as follow: unilateral benefits in crop growth and/or reproduction, reduction in the parent autotoxin effects of certain crops, potential compensatory growth from vagaries of the environment (Willey and Osiru, 1972). Intercropping of plants with date palm did not significantly affect accumulation of Cd, Pb, and Zn compared to the monocultures. Intercropping did not significantly affect the accumulation and removal of heavy metals in contaminated soil (Madejon, et al. 2002). The use of plant species to decontaminate and remediate polluted soils with heavy metals is non-existence in Khozestan. Transfer of toxic elements from soils to plants in industrial areas is of great concern (Malik, et al 2010). To our knowledge there has not been any study that has identified heavy metal accumulator or tolerant plant species from contaminated soils. Therefore, the aim of the present study was to assess the total metal concentration of selected metals in the soils and plant in different planting from contaminated soil. MATERIAL AND METHOD Ahwaz is the capital city of Khoozestan province in Iran that is an industrial zone lies between eastern longitude of 47º40' to 49º20' and 31º5' and northern latitude 32º20' at an elevation of 480-550m (a.s.l). It houses different industrial units which spreads over 63,238 km² of land. Plants growing in the nearby zone of industrial areas along various industrial units exhibiting increased concentrations of heavy metals. A bulk soil from a field (0– 20 cm) nearby well oil and industrial area around Ahwaz city was taken and analyzed for Cu, Mn, Cd and Pb (Tab 1). The soils were air-dried and passed through
