Phytoremediation to clean up environmental spills

Topics: Soil, Phytoremediation, Root Pages: 6 (1844 words) Published: January 28, 2014


Overview
The rise in contaminants in the environment after the industrial revolution has led to deposition of metals, organic compounds and metalloids in high amounts in the soil. Some of the major sources of these pollutants are mining, smelting, mellaurgical industries, sewage sludge treatment, fertilizers, warfare and military training, electronic industries etc. (Padmavathiamma and Li 2007). There are several ways to remediate the soil chemically, physically, or biologically. However, chemical and physical treatments may seem to affect the soil properties heavily, affect biodiversity, make soil less fertile for plant growth and can be quiet expensive too. Phytoremediation is the most cost efficient method of remediating soil without any known side effects that could severely alter the ecosystem of the location (Padmavathiamma and Li 2007). Table Different factors and the cost of process to remediate soil Process

Cost (US $/ton)
Factors in affect
Vitrification
75-425
Requires monitoring over longer periods
Land Filling
100-500
Transportation and excavation of materials. Long period monitoring. Chemical treatment
100-500
Disposal and recycling of contaminants
Electrokinetics
20-200
Monitoring over long periods
Phytoextraction
5-40
Disposal of biomass

The process of using plants to remove pollutants from the environment or reduce them to harmless levels is called phytoremediation. Phytoremediation deals with clean-up of organic and inorganic chemicals. There are four methods of phytoremediation that leads to decrease in pollutants: 1. rhizodegradation and phytodegradation

2. phytoextraction
3. rhizofiltration
4. phytovolatization,
5. phytostabilization.
Rhizodegradation and Phytodegradation are the process of degradation and metabolization of contaminants in the plants or in the soil, sediments, sludge, groundwater or surface water through enzymes produces and released by plants. The microorganisms located in the roots of the trees help in breakdown of organic contaminants into smaller inorganic products such as carbon dioxide and water and other products that are taken up by these microorganisms. As the roots grow bigger, the microbial population increases too leading to more intake and breakdown of contaminants (Dhir 2013). Phytoextraction is removal of metals or organics from the soil by pollutant –accumulating plants by concentrating them in the harvestable parts (Salt et al. 1998). Rhizofiltration is the process of removing heavy metals from water using plant roots. These plants are hydroponics but grown terrestrially to remove toxic metals such as Cu2+, Cd2+, Cr6+, Ni2+, Pb2+ and Zn2+ from aqueous solutions (Dushenkov et al. 1995). Phytovolatization is the taking up on contaminants by plant roots especially metals and metalloids and as it travels to the leaves, it gets converted into gaseous form that evaporates through gas exchanges occurring between stomata of leaves and environment (Suresh and Ravishankar, 2004, Kotrba et al 2009). Phytostabilization is the process of reducing bioavailability of contaminants. As most organic contaminants are lipophilic, this attracts these compounds to hydrophobic surfaces on organic matter like humus, soil particle and plant cell wall components (Suresh and Ravishankar 2004). Development of the concept

Phytoremediation is a fairly old concept as plants were used as farming progressed for beautification and remediation of soils that were either destroyed by natural calamities. Although, it was lost for 300 years, until treatment of wastewater was suggested to be treated by plants. The earliest plants used for phytoremediation were Thlaspi caerulescens and Viola Calaminaria. Eventually, several plants were identified that could be used for phytoremediation such as Astragalus could accumulate 0.6% selenium in dry shoot biomass and other plants that could tolerate and accumulate high concentrations of Co, Cu, Mn, Cd, Ni, Se and Zn. Utsunamyia...

References: Cooney, C. M. (1996). News: Sunflowers remove radionuclides from water in ongoing phytoremediation field tests. Environmental Science & Technology, 30(5), 194A-194A. doi: 10.1021/es962219c
Dushenkov, V., Kumar, P
Lasat, M. M. (2000). Phytoextraction of metals from contaminated soil: a review of plant/soil/metal interaction and assessment of pertinent agronomic issues.Journal of Hazardous Substance Research, 2(5), 1-25.
Lee, J. (2013). An overview of phytoremediation as a potentially promising technology for environmental pollution control. Biotechnology and Bioprocess Engineering, 18(3), 431-439. doi: 10.1007/s12257-013-0193-8
Natalie DeWitt , Robert Frederickson
Padmavathiamma, P. K., & Li, L. Y. (2007). Phytoremediation technology: Hyper-accumulation metals in plants. Water, Air, and Soil Pollution, 184(1-4), 105-126. doi: 10.1007/s11270-007-9401-5
Suresh, B., & Ravishankar, G
Wolfe, A. K., & Bjornstad, D. J. (2002). Why would anyone object? an exploration of social aspects of phytoremediation acceptability.Critical Reviews in Plant Sciences, 21(5), 429-438. doi: 10.1080/0735-260291044304
A citizen 's guide to phytoremediation
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