Srishti Sati
University of Petroleum and Energy Studies
The amount of plastic garbage generated has increased, and traditional techniques are unable to handle these microscopic particles efficiently. This study assesses the ability of emerging technologies, including improved sensors, bioremediation methods, and nanomaterial-based approaches, to identify, measure, and reduce micro- and nanoplastic pollutants in soil matrices through a methodical investigation.
INTRODUCTION
Natural substances when exposed to physical or chemical changes mainly through the process of polymerization and polycondensation, due to which the core natural elements get converted to polymer chains, thus forming plastics. These plastics when exposed to the environment get broken down due to wear and tear into minuscule particles called Micro and Nano-plastics. Microplastics are smaller than 0.5 mm in diameter and nanoplastics are less than 100 nm, however, both these terms are used interchangeably since a clear distinction between the two is yet to be agreed upon.
MPs and NPs pose a serious threat to living organisms as due to their small size and chemical stability, they exist in the environment for a very long period of time and can be transmitted from place to place very easily. They can enter the human body in three ways- inhalation, ingestion and skin contact and cause innumerable health issues such as inflammation, genotoxicity, DNA damage, metabolism etc. Many human activities such as inappropriate disposal of plastic waste, sewage dumping into various waterbodies, dumping plastic waste openly in landfills etc.
These particles get discharged into the environment during all the stages of the value chain i.e. during the extraction of raw material, production of plastic, and converting the plastic to an object or utility. Since most of the plastic products are simply landfilled after their consumption, soil contains 4-23 times more MPs and NPs than the ocean. To separate and purify these plastic particles from the soil, several methods are under research.
Oxidation with Hydrogen Peroxide (H2O2)- This method can be used in isolating the MPs and NPs from the soil as when H2O2 comes in contact with the soil, it breaks down the organic matter of the soil, leaving behind the plastic particles. This method is based on the Oxidative property of H2O2 by which it can decompose the organic matter of the soil, facilitating the separation of MPs and NPs. However, the efficiency of its method is yet to be proven as it is subjective to several factors such as soil composition, its concentration and the type of microplastics.
Enzymatic Digestion- This procedure involves employing specific enzymes to target and break down the organic material of the soil, leaving unaffected, the plastic particles present in the soil. Some common enzymes used for their ability to break down organic material without affecting the plastic products are lipases and proteases. However, for the seamless implementation of this method, the optimization, soil composition, reaction time and an understanding of enzymatic action on different soil types is important.
Flow Field-flow Fractionation- It is yet another separation technique used to extract microplastics from the soil. In this method, the soil sample passes through a thin channel of flowing water where the particles are separated based on their different sizes and proportions and by controlling the flow rate, MPs and NPs are separated from the soil matrix allowing their collection. It is effective in distinguishing plastic particles based on their shapes, sizes and density providing an enhanced form of separation. However, some challenges of this procedure include potential interference from soil components in the flow channel process along with the challenge of moderating the flow parameter and minimizing particle aggregations.
Centrifugal liquid sedimentation- This process of sedimentation includes spinning the soil sample at high speeds, resulting in the particles getting separated based on their density, weight and size. I is used to separating heavier soil particles from light Micro plastic particles. When the sample spins, there emerges a centrifugal force which causes the particles to settle at different rates, leading to the stratification of materials according to their weight and mass. The plastic particles sediment differently from the soil particles due to their lower density. However, one challenge of this process amongst others is identifying the microplastics from other sedimented materials.
Electrostatic separation- This technique makes use of the difference in the electrical properties of microplastics and soil. By applying an electrical field, charged microplastics can be either attracted or repelled from other soil components based on their charge. This process works based on various electrostatic behaviours of several materials. Some shortcomings of this procedure include controlling the charge on plastic and soil particles, minimum interference of the soil components and understanding the conductivity of the soil is also crucial for the effective extraction of microplastics from the soil.
CONCLUSION
Managing MPs and NPs existent in the soil necessitates a multifaceted approach involving several technologies and in lieu of separating micro and nano plastic particles from the soil, several techniques provide promising opportunities and each method has its own unique set of characteristics and shortcomings. It is pivotal to implement various strategies and policies to curb plastic production and consumption and promote sustainable alternatives that enhance waste management practices and help in reducing the influx of MPs and NPs into the soil environment.
Oxidation with hydrogen peroxide uses its oxidative character to decompose the organic matter, isolating the plastics. Enzymatic digestion also performs the same function with the help of some specific enzymes and the flow field flow fractionation technique relies on the rate of flow to segregate microplastics based on size and proportions, density and weight and electrostatic separation also falls under the same category that extracts MPs and NPs from the soil by using its electrostatic property.
There are several options or methods to extract microplastics from the soil, however, each technique faces certain obstacles such as soil optimization, interference from soil components etc. that need to be addressed to efficiently perform their functions. Tackling these challenges requires an in-depth knowledge and understanding of each of the components used in the process and ensuring minimum alteration or loss of plastics during extraction.
Ultimately, addressing the challenge posed by these microplastics at large demands a unified global effort, relevant and active policies, innovative technologies and a sense of collective responsibility towards the planet.
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