Pathways of Plastic Pollutants

By- Ankita

(3 min read)

Scientists are tracking transportation pathways of microplastics across water, soil and air across the globe and have found some interesting results. They have found that decades old plastic waste is much relevant even today and are actively distressing various processes starting from plant growth to affecting incoming solar radiation on a microscale.

Image Credit: Janice Brahney/S.J. & Jessie E. Quinney College of Natural Resources at Utah State University

Today microplastics are found in each and every corner of the earth –from Mount Everest to Mariana Trench and even inside the human body, and in glaciers and ice sheets – they are everywhere, and they are pretty much indestructible.

Plastics can degrade and disintegrate and break down into smaller pieces – micro plastics (less than 5milimetres in size) or nanoplastics (ranging from 1 to 1000 nanometers in size), and they will remain in the environment for a seemingly long time, with a life span of atleast 450 years, in these tiny forms.

Scientist Janice Brahney from the Department of Watershed Sciences at Utah State University is researching on how these tiny plastic fragments get into the atmosphere and how do they stay there and for how long as well as where can the plastic deposition global hotspots be.

The plastic straw you discarded in 1980 hasn’t disappeared; it has fragmented into pieces too small to see, and is cycling through the atmosphere, infiltrating soil, ocean waters and air. Microplastics are so pervasive that they now affect how plants grow, waft through the air we breathe, and permeate distant ecosystems. They can be found in places as varied as the human bloodstream to the guts of insects in Antarctica. Understanding how microplastics move through global systems is essential to fixing the problem”, said Brahney.

The study reports that roads are huge sources of atmospheric plastics as vehicles run over and break down smaller plastic pieces even further and the turbulence launches these tiny fragments in the air where they remain airborne and are carried further by the action of wind.

Similar environment is created in oceans too, where these microplastics are churned and launched upwards by the action of the waves. Agricultural fields are another important source of plastic emission where plastics are introduced either through polymer coated fertilizers or bio-fertilizers derived from various waste treatment procedures where the waste may already be contaminated with plastic pollutants.

Additionally, wind can carry as well as deposit fine plastic particles in virtually anywhere in the planet. The study adds that airborne plastic pieces may remain suspended for upto 6.5 days, which is enough time for these pollutants to be transported across a continent.

While Pacific Ocean and Mediterranean Sea are more likely to receive these airborne plastic particles, continents receive far more deposits. The United States, Europe, Middle East, India and Eastern Asia are the major hotspots for land-based plastic deposition. The ocean-based sources of airborne plastic are more prominent along the west coast of America, the Mediterranean and southern Australia.

Dust and agriculture based sources of airborne plastics are prominent in northern Africa and Eurasia, while road-based sources are prominent in the highly populated regions across the world.The various factors that affect these pathways is still unknown and it is assumed that climatic and environmental factors – such as landscapes, precipitation patterns, etc. – may play a huge role in plastic transportation.

Since we are so plastic dependent and there is no slowing down on this dependency in the near future, it is important to atleast understand how these pathways work and what can be done to control these. Their presence is not only polluting, but also altering the ecosystem.

Peter Deneen, a writer at Watershed Progressive explained, “Most often microplastics end up in snow via airborne deposition. Microplastics tend to be lighter than dust particles and become airborne more easily. These particles, due to their shape, can remain airborne and gain enough altitude to circulate with large-scale weather and be transported to faraway places.”

(Source: https://eos.org/opinions/microplastics-hidden-contribution-to-snow-melting)

Another researcher, Jing Ming, explains “Microplastics depositing in snow will last hundreds of years or even longer. They can absorb solar radiation and reduce surface albedo given they are not completely transparent but with colour.” (Albedo is the property of reflecting sunlight back to the atmosphere.)

As snow and ice melts, the microplastic particles are transported through a variety of ecosystems, contaminating riparian habitat, estuarian, and eventually marine habitats.

Deneen adds “As they reach these ecosystems, whether through snow melt or otherwise, microplastics pick up chemical contaminants and can disturb many forms of life: animals can ingest them, harming not only themselves, but also humans who eat them. Smaller invertebrates will consume microplastics, then be consumed by fish, and the plastic makes its way up the food chain until it arrives on a plate.”

Plastic pollution is truly a global menace that is affecting the environment in numerous ways. We all can contribute towards beating plastic pollution by reducing usage of single use plastics, carrying our own water bottles and bags, by opting for proper waste disposal and finally the 3Rs – Reduce, Reuse, Recycle.

Science Next Door has covered some interesting articles in this topic so far –

Accumulation of Microplastics in Human placenta(Plastics are ubiquitous)

Microplastics found near the top of Mount Everest

References:

1. https://www.eurekalert.org/pub_releases/2021-04/sje-ppt040721.php

2. https://phys.org/news/2021-04-microplastics-affecting-ice.html

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