Â
Pollution is considered one of the five drivers of anthropogenic global change, and of all forms of pollution, that involving water is one of the biggest ecological problems in the contemporary world. Much of the pollution in the seas and oceans —whether in the form of solid waste, microplastics or substances dissolved in the water— comes from the mainland, from where it is carried by water currents towards riverbeds.
At first glance, it would be easy to assess when a river is more polluted than another if one has clear, clean and good quality water, and the other carries large amounts of plastics and toxins. There are certain markers —physical, chemical and biological— that allow the quality of a body of water to be objectively quantified. However, when trying to assess rivers with extreme levels of contamination, discerning which ones are worse off can become a complex task.
One river may have a much higher load of dissolved pollutants in the water than another, but a smaller amount of suspended solids. Choosing which of the two is in worse condition will depend on the scale used in the evaluation.
In this article we will talk about some of the most polluted rivers in the world, based on the amount of waste they throw into the sea, and the danger of that waste. Go ahead that, although they are all those who are, they are not, far from it, all those who are. Surely there are some rivers that, depending on the scale used, are more polluted than those presented here.
Ohio River
Of all the mouths of North American rivers, the one that presents the greatest amount of pollution is that of the great Mississippi River, and of its main confluents, ahead of the upper branch of the same or the Missouri River, the one that contributes the most pollution to that mouth is the Ohio River.
As it passes through the cities of Pittsburgh, Cincinnati, Louisville or Evansville, the Ohio River is not only loaded with huge amounts of urban wastewater, in many cases untreated; In addition, large companies and corporations in the steel industry in its highest section, and intensive agriculture in its lower basin, generate discharges or accumulate garbage whose leachates end up in the river waters.
The levels of pesticides found in the tissues of the fish in this river exceed all levels considered safe, including some that have been banned for decades, such as DDT. Many of these pollutants are bioaccumulative in nature, and this means that once incorporated into the food webs of ecosystems, it is particularly difficult to eliminate them.
Yangtze, Ganges and Yellow Rivers
China and India are the countries that contribute the most to the current microplastic pollution problem. The Yangtze River, in China, is the river that deposits the most plastics in the sea in the world, it is estimated that it exceeds 300,000 tons of plastic per year.
Most of this waste appears in the form of microplastics, particles less than five millimeters in size. The Ganges system, which includes the Brahmaputra and Megna rivers, is estimated to release up to 3 billion plastic particles into the sea each day into the Bay of Bengal; amount that decreases after the passage of the monsoon.
Apart from the problem of plastic, these rivers reach such a level of contamination that their waters, in some sections, are not even suitable for fishing or for agricultural use. An unhealthy concentration of nitrates, ammonium, phosphates, phenols, and fecal bacteria have been found in the Yellow River . Its waters also carry arsenic and heavy metals such as lead and chromium, which pose serious health risks to people who drink that water or feed on its fish. These dangerous contaminants also accumulate in the crop fields irrigated with river waters, and are retained by the plants, also entering the food chain.
In these cases, the source of pollution comes from agriculture, industry —the main source of heavy metals— and untreated or poorly treated domestic wastewater.
Citarum River
The Citarum River is considered by many to be the most polluted river on the planet. It is located in the western region of the island of Java, Indonesia. It barely measures 300 km in length, somewhat less than the Segura, and less than half the Guadalquivir.
The deplorable state of this river is a consequence of the constant discharges from the industry —especially textiles—, as well as urban waste and, inexplicably, its use as a landfill. Some studies describe the uses given to the Citarum basin as “environmental crimes”, causing an environmental disaster, in the form of highly dangerous toxic waste, which is difficult to quantify.
For more than a decade, the national authorities of Indonesia have shown good intentions and even budget allocations for the cleaning, sanitation and recovery of the Citarum. However, researchers continue to denounce the catastrophic ecosystem situation, for which no efforts seem to be made to solve it.
References:
Blocksom, K. A. et al. 2010. Persistent organic pollutants in fish tissue in the mid-continental great rivers of the United States. Science of The Total Environment, 408(5), 1180-1189. DOI: 10.1016/j.scitotenv.2009.11.040
Chen, Y. et al. 2020. Sustainable development in the Yellow River Basin: Issues and strategies. Journal of Cleaner Production, 263, 121223. DOI: 10.1016/j.jclepro.2020.121223
Napper, I. E. et al. 2021. The abundance and characteristics of microplastics in surface water in the transboundary Ganges River. Environmental Pollution, 274, 116348. DOI: 10.1016/j.envpol.2020.116348
Riyadi, B. S. et al. 2020. Environmental Damage Due to Hazardous and Toxic Pollution: A Case Study of Citarum River, West Java, Indonesia. International Journal of Criminology and Sociology, 9, 1844-1852.
Zhu, X.-T. et al. 2018. [Distribution and Settlement of Microplastics in the Surface Sediment of Yangtze Estuary]. Huan jing ke xue= Huanjing kexue, 39(5), 2067-2074. DOI: 10.13227/j. hjkx.201709032
