Phytoremediation: Utilizing Hyperaccumulator Plants to Extract Toxic Chemical Waste from Soil & Groundwater


By Luci C. Edenlord

Soil and groundwater contaminants represent one of the most harmful pollutants in the world by destroying habitats, wrecking ecosystems, poisoning clean water and being a huge detriment to human and animal health. Imagine that by just planting a few simple seeds, the destruction would melt away without negatively affecting human and animal health and the environment. One field of sunflowers (Helianthus) has the capability to extract industrial contaminants such as lead (Pb), zinc (Zn), cadmium (Cd), copper (Cu) and manganese (Mn). Amazingly, young sunflower seedlings may extract ninety-five percent of uranium (U) deposits, a highly toxic radioactive element, in only twenty-four hours (García, 2015). Corporations today create harmful fossil fuels, expel toxic air pollutants and produce billions of pounds of destructive solid waste byproducts, unnecessarily damaging the biosphere in the process. These contaminants come from the overcompensation of industrial waste, which seeps into the environment, disrupting valuable ecosystems and polluting fragile habitats. In addition, industrial chemical waste jeopardizes human health by polluting the air with carbon monoxide and creating hazardous wastelands strewn with radioactive elements. From oil-polluted bodies of water to soil contaminants such as arsenic (As), these destructive chemical compounds destroy pre-existing ecosystems, becoming a significant threat to people and animals. Many remediation companies profit greatly by extracting harmful contaminants from from soil and groundwater. However, the amount of pollution emitted during remediation exacerbates the environment, adding to pre-existing waste, creating even more harmful chemical compounds. Even though organizations such as the U.N. establishes laws preventing corporations from manufacturing enormous amounts of harmful contaminants and pollutants such as carbon dioxide (CO2), the atmospheric concentration of pollution continues to grow at an alarming rate (Woolley, 2015). Luckily phytoremediation, an eco-friendly and inexpensive solution that benefits both the environment and human health has emerged. Hyperaccumulators are plants that specialize in extracting soil and groundwater contaminants through their root xylem, converting toxic chemical matter into harmless plant tissue, undergoing the process of phytoremediation (Sharma & Mudhoo, 2011). Rather than paying corporations to remove soil and groundwater contaminants, a simple hyperaccumulate plant accomplishes the same job without harming the environment. Phytoremediation represents a highly effective, cost efficient system by naturally extracting soil and groundwater contaminants from the environment because it supports human and animal health and sustains entire ecosystems of people, animals and nature.

The process of phytoremediation using hyperaccumulators to extract soil and groundwater contaminants such as lead, (Pb), cadmium (Cd), selenium (Se), zinc (Zn), mercury (Hg) and copper (Cu) is extremely valuable to improving environmental health. By isolating toxic soil contaminants such as destructive metals and radionuclides, the hyperaccumulators undergo the process of phytoremediation and photosynthesis to extract pollutants from the soil and groundwater (Sharma & Mudhoo, 2011). First, the plant completes phytostabilization, as the roots of the plant decrease the amount of groundwater in the soil matrix to isolate and metabolize the contaminant. Next, during the process of phytoextraction, or phytoaccumulation, the plant’s root xylem absorb the polluted groundwater without significantly altering the physical structure or fertility of the soil matrix. Then, the plant isolates the contaminant, concentrating it into a biomass stored in the plant’s tissues. However, if the plant must store metal-based contaminants, it will use a vacuole created by phytochelatins, oligomers of glutathione which are produced from the phytochelatin synthase, a chelator for heavy metal detoxification and metallothioneins, molecular proteins composed of cysteine found in the golgi apparatus of plant cells (Sharma & Mudhoo, 2011). Once the plant collects the contaminated groundwater into its tissue, the process of phytodegradation begins. Figure 1 below shows the biochemical process in which the plant breaks down toxic compounds inside its tissues, using enzymes including dehalogenases, oxygenases and reductases to effectively decompose the pollutants. The plant then undergoes rhizodegradation, the breakdown of organic matter through microbial activity in the rhizosphere. Once completed, the plant concludes with phytovolatilization where microbes inside the plant chemically change the toxins into a harmless form, and then release them into the atmosphere (Sharma and Mudhoo, 2011).

Figure 1: The diagram above represents the transfer of cells through the plant’s xylem with the contaminant metals (Sharma & Mudhoo, 2011).

Imagine that by planting a simple poplar tree or growing a field of Indian mustard that all of the harmful contaminants in the soil and groundwater would be removed by a non-toxic, non-GMO (Genetically Modified Organism) and eco-friendly solution. These plants are known as hyperaccumulators, botanical species of plants found in almost every state in America. The most sustainable hyperaccumulators exhibit the full photosynthetic process of turning environmentally detrimental contaminants into a tissue-based biomass, successfully ridding the environment of destructive and persistent contaminants. These contaminants are extremely dangerous as lead (Pb), a common contaminant found in soil, which causes internal organ malfunctions and nausea once ingested in the human body, while mercury (Hg) spurs respiratory problems. Lastly, uranium, a radioactive metalloid that is lethal to humans and animals is easily removed by poplar trees and sunflower hyperaccumulators. In addition, Indian mustard (Brassica juncea L.) may accumulate high levels of metals in soils, transforming large quantities of concentrated biomass into tissue. By collecting triple the amount of cadmium metals (Cd), reducing 28% of lead (Pb), and removing up to 48% of selenium (Se), zinc (Zn), mercury (Hg), and copper (Cu) effectively, Indian mustard is a simple solution to removing waste contaminants that may benefit diverse environments (García, 2015). Hyperaccumulators thrive in a variety of different habitats including near water. For example, the Willow tree (Salix species), a hyperaccumulate that grows best in aquatic habitats removes lead (Pb), cadmium (Cd) and nickel (Ni) out of the soil safely (García, 2015). In addition, during the process of rhizofiltration, metals such as lead (Pb), cadmium (Cd), zinc (Zn), nickel (Ni), and copper (Cu) are extracted as well as radionuclides including 137Cs, 90Sr and U and other hydrophobic organics. These hyperaccumulators include cattails (Typha), duckweed (Lemnoideae) and arrowroot (Maranta arundinacea) (Schnoor, 1997). The poplar tree (Populus deltoides), utilizes its sustainable root system to extract trichloroethylene (C2HCl3) a volatile form of anesthetic and removes 95% of other chlorinated solvents such as carcinogenic carbon tetrachloride from the soil. Indian grass (Sorghastrum nutans) has the ability to detoxify harmful pesticides and herbicides as well as remediate petroleum hydrocarbons. The sunflower (Helianthus Annuus L.) removes radioactive metals such as caesium (Cs) and strontium (Sr) (García, 2015). Through the stage of phytotransformation, chemical contaminants such as the herbicides atrazine and alachlor, chlorinated aliphatics (TCE), Nutrients (NO3, NH4+, PO43-) and ammunition wastes (TNT, RDX) are all extracted from soil and wastewater by the hyperaccumulators clover (Trifolium) and cowpeas (Vigna unguiculata) (Schnoor, 1997). Hyperaccumulators represent the best solution to removing harmful contaminants from the environment because of they are easy to plant and out-perform corporate remediation methodologies. They are inexpensive, readily available in most stores, and easily acclimate to new environmental surroundings. One package of sunflower seeds has the ability to extract radioactive metals from groundwater without disrupting the environment and being too expensive.

Phytoremediation represents the most effective solution to rehabilitate damaged environments because of its low cost and easy accessibility in comparison to corporate remediation solutions. Corporations today have created harmful remediation machines to mimic hyperaccumulator actions, however, these responses do not only destroy the environment but cost more than their true worth. Traditional manufactured remediation solutions such as Soil Vapor Extraction, where wells drilled three feet deep into the ground and then vented to create water vapor (H2O) in attempt to extract the groundwater contaminants and pollutants which are extremely deadly are not as productive as phytoremediation (EPA, 2012). This unreliable function alone costs from $20-220 when only a margin of the price could be spent on a tray of poplar tree seedlings that would complete the same job without disrupting the environment (Schnoor, 1997). Thermal desorption, another manufactured remediation creation attempts to solve soil and groundwater contamination relying on two different forms of adsorbates based on the situation of remediation; direct fired thermal desorption and indirect fired thermal desorption. In direct fired thermal desorption, large amounts of soil are fed into a rotating cylinder heated from 500° to 800°F, discharging the contaminants from the solvent creating exhaust and polluting the air. Contaminants are then obliterated in downstream organic control devices such as thermal oxidizers. During the indirect fired thermal desorption method, drum-like containers covered in thermal heaters are filled with soil which is mixed by paddles to distribute the heat and discharge the contaminants from the soil. When these methods remove contaminants from the soil and groundwater, they also destroy multiple supportive trophic minerals that promote plant growth. These minerals include potassium (K), which retains the level of salt in plants, magnesium (Mg) which assists the chlorophyll molecule, and nitrogen (N) which creates amino acids. Without these minerals, the quality of food both people and animals eat would drastically lose nutrients and abundance, becoming a huge threat. Using phytoremediation would guarantee that the quality and quantity of plants would always remain healthy and sustainable, supporting the ecosystems they are a part of. In addition, this method does not eliminate any metal compounds from the soil, therefore not extracting the full majority of contaminants (Midwest Soil Remediation, 2016). This procedure costs $120-300, while a simple hyperaccumulate start can be bought for less than $10 (Schnoor, 1997). Incineration, or open-air burning, represents the most harmful form of traditional remediation. The process involves using a controlled flame combustion reaction, the chemical property where heat is introduced to a substance leading to explosion, into a burner causing thermal decomposition of the solvent. By applying heat from 1,400° to 3,000°F, inceration attempts to destroy any form of soil and groundwater contaminant at huge prices (Engineering and Expeditionary Warfare Center, 2016). These prices range from $200 to 1,500 in comparison to the modest price of a simple tray of sunflower starts (Schnoor, 1997) Clearly, the availability, price and effectiveness of phytoremediation proves far more sustainable than other competing solutions. Phytoremediation constitutes the best way for supporting both humans and animals because of the minimal ecological footprint.

Phytoremediation supports human and animal health by creating a sustainable environment as plants represent an integral role in both aquatic and terrestrial ecosystems. Using hyperaccumulator plants as a way to clean up biocontaminants such as lead (Pb), mercury (Hg) and uranium (U) avoids more corporate remediation distributive methods such as the process of incineration and thermal desorption. In addition, corporate solutions for remediation creates harmful exhaust that is filtered in attempt to minimize the amount of pollutants released into the atmosphere, yet this kind of technology poses a direct threat to humans and the biosphere (Midwest Soil Remediation, 2016). The dangers of carbon monoxide gases produced by corporate machinery demonstrates a hazardous addition to pollution.  In contrast, phytoremediation represents an environmentally friendly remediation process that does not create pollution byproducts that layer onto the pre-existing contaminants. Incineration, a corporate remediation system contributes more to pollution than strengthening the environment throughout its procedure. During the hazardous process of removing soil and groundwater contaminants, an incomplete combustion reaction or other chemical processes may lead to the formation of dioxins, an extremely toxic compound that comes from manufactured waste (Engineering and Expeditionary Warfare Center, 2016). Dioxins cause reproductive and developmental problems in people as well as hurting the immune system. In addition, dioxins also interfere with hormones and cause cancer. They remain in the body for extended periods of time stored in fat tissue with a half-life 7 to 11 years. By trimming fat off of meat and eating a well-balanced diet that does not depend on seafood, where many dioxins are found in animals, people can limit their exposure to this acute and highly toxic compound (World Health Organization, 2016). People exposed to high levels of dioxins cancer rates increase by 40% (Green Facts, 2016). Dioxins have been also known to harm animals as well. When exposed to this toxin, animals may become infected with endometriosis (uterine disease) and neurobehavioral or cognitive defects. Male animals have been known to have reduced sperm counts while female animals develop urogenital malformations and which harmful effects on the immune system. TCDD, an extremely potent and destructive dioxin proves as a harmful carcinogen that promotes the growth of cancer cells in animals (Green Facts, 2016).  Another side effect of incineration includes the threat of lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) leaving the unit of combustion through flue gases requiring in an instant installation of gas cleaning systems for their removal (Engineering and Expeditionary Warfare Center, 2016). These cleaning corporations are expensive, and lead to spending more money towards a remediation system and become detrimental to people’s health. In addition to this, during the heating process of incineration, metals present may react to each other including chlorine (Cl) and sulfur (S) in the feed stream causing the formation of more volatile and extremely toxic compounds than the ones meant to be removed through remediation. These compounds live only for short periods of time but cause reactions that may be destroyed (Engineering and Expeditionary Warfare Center, 2016) Because of these harmful gases and fossil fuels expelled into the air, the amount of carcinogens continues to grow steadily. Throughout the development of the economy comes the growing need for corporations to surpass new economical demands of technology by providing the world’s population with more products to fit the growing technology and agricultural expectancies. However, with this comes byproducts from factories and warehouses, creating chemical compounds and mixtures that create more deadly elements that leak into our environments contaminating human and animal life. The Gulf Oil Spill devastated Mexico causing 87 days of spewing methane gas and oil from an uncapped wellhead 1 mile under the ocean as the result of a corporate miscalculation (Griffin, 2015). Rather than exploiting natural resources and elements, phytoremediation extracts toxins from soil and water without harming the environment in the process. By using a phytoremediation as an eco-friendly tool to support the environment, the negative impact on people and animals is greatly reduced. Through each use of phytoremediation using the right hyperaccumulators, the majority of contaminants in soil and groundwater are removed.

Anything that supports human and animal health and is overall able to sustain entire ecosystems of people, animals and nature and represents a highly effective and cost efficient system. By utilizing nature’s plants in an effective way to eliminate man-made and caused waste in the environment, people, plants and animals can begin to clean up the earth in the most sustainable way possible. Instead of using harsh mechanical methods with fire and destruction, adding to manufacture by-products in the environment, phytoremediation creates a healthy and safe environment for all natural things to grow without affecting other ecosystems in negative ways. Phytoremediation has the power to help people, plants and animals across the globe, strengthening environments and helping to heal deforestation, pollution and other human-caused forms of waste expelled into the environment. This plant-based solution aids in the production of turning harsh CO2 into oxygen, creating a more stable environments and safer living spaces for people and animals. By using affordable and easily accessible hyperaccumulators like sunflowers, willows and and poplar trees to extract dangerous compounds like lead (Pb) and mercury (Hg) from the groundwater and soil instead of Soil Vapor Extraction, habitats will benefit from the natural support to rehabilitate the environment (EPA, 2012). Finally, tradition remediation corporations have invented a device that literally eliminates all the compounds from the soil, leaving it malnourished and unhealthy while phytoremediation promotes human, animal and environmental growth, supporting everyone. If everyone knew that they could sustain the earth’s viability and their own health by planting a few simple hyperaccumulators, the world’s overall health would greatly increase. Simple things like planting hyperaccumulators improve the earth one plant at a time. Phytoremediation displays the only effective solution to extracting soil and groundwater contaminants because of its positive impact on the environment around it.  It is extremely vital to be outside and a part of nature because people are the solution to making the world a better place and the only ones that can fix our mistakes to benefit ourselves and others. By supporting soil and water health, the world would become a better place, one sunflower seedling at a time.

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