By Dalia Saad, University of the Witwatersrand | –
The Nile is one of the most famous rivers in the world. It is also the most important freshwater system in Africa. About 300 million people live in the 11 countries it passes through. Many depend on its waters for agriculture and fishing for income.
The two main tributaries of the Nile, the Blue Nile and the White Nile, converge in Sudan’s capital city, Khartoum. This industrial hub has grown rapidly over the past few decades.
The Nile is not immune to the same pollutants that affect rivers around the world. Plastic debris is of particular concern. Over time, plastics break down into smaller pieces known as microplastics. These are small plastic particles with a maximum size of five millimeters, down to the nanoscale. Recent research has found this out
rivers have been modeled to export up to 25,000 tons of plastics from their sub-basins to the seas annually. More than 80% of this amount is microplastic.
This has major negative consequences for biodiversity and the climate. As microplastics degrade, scientists have discovered, they produce greenhouse gases. Airborne microplastics can influence the climate by scattering and absorbing solar and terrestrial radiation, leading to warming or cooling of the atmosphere depending on particle size, shape and composition. It also negatively affects animal and human health. Microplastics have been shown in laboratory studies to be toxic to animals and cells.
Most research on microplastics in African waters has focused on marine and coastal areas. To address this gap, I conducted a study to assess the presence of microplastics in the Nile River in Khartoum. My students and I analyzed the presence of microplastics in Nile tilapia. This popular African freshwater fish species forms the basis of commercial fisheries in many African countries, including Sudan.
Photo by Islam Hassan on Unsplash
The results do not make for happy reading. In the 30 freshly caught fish we analyzed, we found a total of 567 microplastic particles. This shows that the Nile River is contaminated with microplastics that can be consumed or absorbed in various ways by tilapia and other aquatic organisms.
Our sample
The fish used in our study were caught just after the confluence of the two Niles, known in Arabic as Al-Mogran.
We visited the Al-Mawrada fish market in the Omdurman area, which is also next to the Nile. All 30 specimens we purchased were freshly caught.
We dissected the fish to remove their digestive tracts. Individual tracts are treated so that they dissolve any organic matter they contain without interfering with the analysis of microplastics. The resulting solution was subjected to another extraction procedure and then we performed physical and chemical analysis.
Each specimen had microplastics in its digestive tract.
The count ranged from as few as five to as many as 47 particles per single fish. In total, we identified 567 particles. This is high compared to studies that have reported microplastics in tilapia species in other rivers and lakes. To date, there are no global guidelines or standards for what might be an “acceptable” number.
Shape, size and color
We found different sizes of microplastics (0.04mm to 4.94mm), shapes (fibers, fragments, films, foams and pellets) and colors. The most common are very small (less than 1mm), fibrous – they appear thin and elongated – and colored (dyed).
These characteristics make sense because of how fish and other aquatic organisms eat. Nile tilapia are versatile feeders: they eat a variety of organisms including phytoplankton, aquatic plants, invertebrates, detritus, bacterial films, as well as other fish and fish eggs. That puts them at a high risk of ingesting microplastics.
Nile tilapia are more likely to consume particles that are the same size as their natural prey, as well as the same shape and color.
Smaller microplastics are excellent carriers for other pollutants such as heavy metals, resulting in additional health risks. Their small size makes it easier for them to migrate to organs such as the liver. Studies have found microplastics in the tissues, muscles, liver, blubber and lungs of other aquatic as well as marine mammal species.
Fibers, the most predominant shape found in our specimens, remained in the gut longer than other microplastic shapes. This can also lead to fish health problems. Colored microplastics contain dyes, many of which contain toxic chemicals.
All of this has serious implications for human health, as people catch and eat fish, introducing microplastics and associated chemicals into their bloodstreams.
Source of pollution
Where does all this plastic come from? For starters, 65% of plastic waste in Khartoum is dumped in open dumps. From there, it contaminates water bodies and other parts of the environment.
Image by Refaat Naiem from Pixabay
The city’s wastewater treatment system is ineffective. The three wastewater treatment plants in Khartoum state, Karary, Wd-Daffiaa and Soba, are outdated and do not meet local and international standards. That means untreated effluent from domestic, industrial and agricultural activities is another possible source of microplastic pollution.
There are also countless recreational sites along the River Nile in Khartoum. Nile Street is the most popular in the capital city, hosting water sports, restaurants, cafes, clubs, event venues and hotels, as well as tea ladies (women who serve hot drinks from makeshift mobile cafes by the river) . However, waste disposal and collection practices are lacking, so plastic waste from these recreational activities ends up in the river.
Nothing is easy to fix
Dealing with microplastic pollution is not easy. This will require technological advances, as well as the collective efforts of consumers, producers, governments and the scientific community.
As consumers, we need to change our behavior towards plastic products, especially single-use plastics. For example, choose cloth shopping bags instead of plastic bags; use glass and metal containers. Recycling is also important.
Governments should enforce waste management regulations and improve waste management practices, as well as help improve public awareness. Strategies and policies should explicitly feature microplastics.
Scientists can’t just fill in the knowledge gaps around microplastics. Communicating scientific findings is important; as well as developing innovations to protect against microplastics and their harmful effects.
I would like to thank and acknowledge my student, Hadeel Alamin, who conducted this study with me.
Dalia Saad, Researcher, School of Chemistry, University of the Witwatersrand, University of the Witwatersrand
This article is republished from The Conversation under a Creative Commons license. Read the original article.
