Oil activity is polluting the headwaters of the Amazon rivers in a generalized way and modifying the chemical composition of their waters, according to a study carried out by researchers from the Institut de Ciència i Tecnologia Ambientals and the Department of Animal Health and Anatomy. of the Autonomous University of Barcelona (ICTA-UAB), as well as of the International Institute of Social Studies of the Erasmus University of Rotterdam (ISS-EUR, Netherlands), which has quantified the environmental impact that discharges from extractive activity have provoking in the area for three decades.
The research, published in the journal Environmental Pollution, is part of a broad scientific project developed by both groups to analyze the worrying levels of oil pollution in an area of the Peruvian Amazon near the border with Ecuador.
In the waters of these rivers, much higher than usual levels of harmful compounds such as chloride, chromium, barium and lead have been detected
“Although we were aware that it was taking place, there was no scientific evidence on the environmental impact of oil spills in the area. It had not been possible to quantify it as they are very remote and difficult to access areas ”, explains Antoni Rosell, ICREA researcher at ICTA-UAB. To carry out the study, data from 2,951 surface water samples from four rivers of the Amazon collected by Peruvian public agencies and oil companies between 1987 and 2013 have been analyzed.
The results reveal the presence in river water of much higher than usual levels of chloride, chromium, barium, lead and hexavalent chromium, some of them highly polluting compounds for the environment and dangerous for health. The source of contamination is not only accidental oil spills but, to a greater extent, the habitual discharge of formation waters, extracted from the fields together with oil (rich in heavy metals, hydrocarbons and salts). "Until now, the polluting impact of the formation waters had not been assessed", comments Raúl Yusta, co-author of the study.
98 barrels of water for each one of oil
For every barrel of oil produced, companies extract up to 98 barrels of formation water that has been discharged directly to the soil and rivers of the tropical forest of the Peruvian northern Amazon from 1972 to 2009. These formation waters contain levels of chloride 13,379 times higher than the waters of Amazonian rivers, while the chromium levels are multiplied by 67, those of cadmium by 40, those of lead by 31 and those of barium by 22.
Researchers estimate that these oil activities have discharged an average of 5 tons of lead a year, 8 tons of hexavalent chromium, and 3.7 tons of salt a year into the river beds. These large concentrations of heavy metals and salts are modifying the chemical composition of the headwaters of the Amazon rivers and altering one of the most preserved and natural ecosystems in the world. "It is estimated that at present, the waters of the Amazon River exceed their natural concentration of salts by 30%," says Rosell.
Discharges at the headwaters of rivers, such as Corrientes and Tigre, impact the lower areas of the Amazon
This local contamination as a result of hydrocarbon activity has a very broad supraregional and transnational implication, since the discharges at the headwaters of the rivers (mainly the Corrientes and the Tigre) impact the lower areas of the Amazon. Thus, pollution extends to thousands of kilometers of rivers, sediments and soils, leading to the bioaccumulation of heavy metals in fish, animals and people who eat river fishing and the hunting of animals that ingest river waters. training in an attempt to make up for the lack of mineral salts in their usual diet.
"This contamination would not only be directly impacting wildlife in general in a region that is megadiverse and where some species that are already in danger of extinction live, but it also affects indigenous communities that depend on hunting and fishing as a source of animal protein ", comments Pedro Mayor, co-author and professor at the Department of Animal Health and Anatomy at the UAB.
As a consequence, the investigation links this chronic contamination with the high levels of lead and cadmium detected in the blood of the 45,000 inhabitants of the five indigenous ethnic groups residing in the area. Although the impact on the health of the inhabitants has not been specifically evaluated, scientists recall that these compounds are neurotoxic and carcinogenic.
“For years, environmental malpractice by oil companies has been denounced by indigenous populations, until the Peruvian government declared the area an environmental emergency in 2013 and a health emergency in 2014. However, now we have been able to quantify the compounds that are being dumped ”, indicates Martí Orta, co-author of the study, who explains that for many years it was denied that lead contamination in the jungle came from hydrocarbon activity“ without taking into account that the million barrels per day of water of formation spilled in the area do contain lead ”.
The scientists warn that the contamination rates found by the study could be even higher, since many of the samples analyzed were taken by companies and government agencies outside of established procedures. Legislation requires that water samples be taken within a radius of 500 meters from the source of contamination and some were taken up to 36 km downstream from the discharge point, concludes Rosell.