Phytoremediation: An effective remedial technique
Muhammad Umair Yasin*1, Hina Ahmed Malik2.
1Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.
2Soil Agriculture Research Center Lab D-138, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.
*Corresponding author’s email: [email protected]
Phytoremediation is a technique which use green plants to clean up the contaminated sites. Generally phytoremediation depends upon some factors. First, for high concentration accumulation of metal, plant must have to produce sufficient biomass. In some cases total metal concentration in plants decreased by increasing the plant biomass, but overall it allow large amount of metal to accumulate. Second the metal rich tissues should be planted and harvested repeatedly because metal accumulating plants are responsive to agricultural practices. Therefore, it is preferable that accumulated metal should be in shoots rather than the roots, because metal accumulated in shoot can be cut and removed from plant. This practice is done on small scale but impossible on large scale. The entire plant should be removed in case of metal accumulation in roots. There is increased cost of phytoremediation in case of removal of full plant because of additional labour and plantings and it is also harmful for environment and more time is required for establishing new plants.
Heavy metals are harmful for human and animal health due to their long term persistence in environment as well as they are major environmental contaminants. Heavy metal contaminated soils remedy is very difficult due to its costly and complex procedure. Physical, chemical and biological methods are basic tools of conventional remediation technologies which can be utilized either individually or in combination in order to minimize contamination to an acceptable level. Although used efficiently these methods are costly, environmentally destructive and time consuming. These methods are not only dangerous for natural soil environment but also a cause of large amount of waste.
Phytoremediation processes are very efficient at low or medium levels of contaminations because high levels of contamination may result in inhibition of plant growth as well as microbial activity. Mechanism involved in micronutrients uptake, translocation and storage are same as in translocation and storage of heavy metals. Four phytoremediation processes are recognized for heavy metal contaminated soils. Phytoextraction, phytostabilisation, phytovolatilization and rhizofiltration. The first two mechanisms are more consistent.
Phytoremediation has both advantages and limitations as other remediation technologies. Phytoremediation is more cost effective, environment friendly, has wide range application on toxic metals and more aesthetically pleasing technique. Besides these advantages phytoremediation is a lengthy process and it can be applied on surface soil.
Selection of plant species for phytoremediation is based on their nature of contaminants and the soil, their root depth and regional climate. Root depth has direct impact on depth of soil that can be remediated. It greatly varies among different plant types and depending on local conditions such as soil structure, soil fertility, depth of a hard pan, contaminant concentration, cropping pressure, it significantly vary for one species.
Phytoremediation is used as an effective remedial technique to clean up soils contaminated with heavy metals. There is need to conduct research on factors which directly control efficiency of this process. These factors include climatic conditions, soil properties and plant species. Species with high remediative abilities should be identified in order to raise social and environmental improvement of population. There is need to do research which mainly focus on development of such agriculture techniques which results in improvement of phytoremediation efficiency and helps to cut down the budget and time of removal of heavy metals from soils.