Mercury used in mining causes environmental risk to soil, water and air


The same mercury used by illegal mining that is causing illness among the Yanomami people also contaminates animals, the water in rivers and creeks, the forest floor and even the air. Highly toxic and difficult to remove, the metal represents a health and environmental risk. In Brazil, its use is controlled by Ibama (Brazilian Institute for the Environment and Renewable Natural Resources).

Today, all mercury that is used in mining is illegal, according to a member of Ibama’s coordination of the Hermes operation (Hg), who, last year, investigated the “laundering” of the smuggled metal. While mining operations normally seize between five and ten kilos of mercury, the action in partnership with the Federal Police confiscated 200 kg and destroyed the authorization for the use of another seven tons of mercury.

Added to an operation in 2018, which seized another 340 kg of mercury and suspended the import license of a company that controlled almost the entire market, the regular circulation of mercury for mining in Brazil was completely paralyzed.

The Ibama official, who spoke on condition of anonymity for fear of reprisals from criminals, explains that there is currently no legal source for mercury and that no company is allowed to import mercury for retail sale, nor is any recycler authorized.

Even so, mercury is used in large quantities in illegal mining operations, such as those carried out in Kayapó, Munduruku and Yanomami territories. A recent study showed that mining on indigenous lands in the Legal Amazon has increased by 1,217% over the last 35 years.

Gold can be found in nature in two forms: in nuggets (that is, stones) and as very fine particles mixed with soil or sediment from the bottom of rivers. “It is in this form of fine particles that it appears in the Amazon”, says environmental chemist Anne Fostier, a researcher at Unicamp’s Institute of Chemistry who has been studying the mercury cycle in the region for three decades.

To find the gold, it is necessary to dig the ground or suck the sediment from the bottom of the rivers, which is done with rafts. This mud is mixed with metallic mercury (the same form found in thermometers, for example), which forms an amalgam with the gold. Then this amalgam is burned. As mercury is volatile, when it is burned it turns into a gas and only gold remains.

With the disposal of contaminated mud, the mercury ends up in the soil and in the water of rivers and groundwater. With burning, it pollutes the atmosphere.

Both the mercury that goes into the soil and the one that goes into the atmosphere can, at some point, end up falling into rivers. This is the biggest focus of concern, because it is in aquatic environments that mercury assumes one of its most toxic forms.

Through the action of microorganisms, inorganic mercury from mining will be associated with carbon and transformed into methylmercury. “Once transformed into methylmercury, it will accumulate along the food chain”, explains Fostier. “First, it accumulates within organisms, in a process called bioaccumulation. Furthermore, it has a process called biomagnification, which results from accumulation along the food chain.”

This means that when small animals, which have lower concentrations of methylmercury, are eaten by larger ones, they cause these carnivorous fish, which are at the top of the food chain, to accumulate these contaminants. “And at the end of the chain we have the human being, who consumes fish — and preferably carnivorous fish, which are tastier, but contain more mercury”, says the researcher.

The problem is especially serious in communities where fish are the main source of protein, as is the case of riverside dwellers and indigenous peoples in the Amazon.

“The Tapajós River region has places, like Santarém, and Itaituba, in Pará, that are very contaminated by mercury”, exemplifies Paulo Moutinho, interim executive director of Ipam (Amazon Environmental Research Institute). “This exposure causes several health problems. It can attack the central and peripheral nervous system, cause problems in the digestive tract, with reduced absorption of nutrients, and damage the immune system”.

Also, mercury vapor that goes into the atmosphere after burning can become a far-reaching problem. In gaseous form, this metal is very slightly soluble in water and does not react with almost anything. Thus, it will not be washed off by rain and will stay in the atmosphere for a long time. By air, it can be transported over medium or long distances.

“Currently it is considered that the time that mercury can remain in the atmosphere varies from five months to a year. Consequently, it will contaminate other environments, other places different from the one where it is emitted”, highlights the specialist.

In duly regulated mining operations, it is mandatory that due care is taken so that this contamination does not occur. But, illegally, protocols are not followed that guarantee the health of the environment or of the miners themselves, who inhale large amounts of this gaseous mercury.

Illegal mining also has other serious environmental impacts. The main thing is deforestation, but the rivers are also harmed by this activity. Affected by mining tailings, turbid waters are unable to absorb light, impacting aquatic ecosystems.

There is a lack of precise data on the size of the impact of mercury contamination by illegal mining, but Ibama claims that it is implementing studies in this direction.

“A project to monitor rivers in the Amazon Basin is under development, within the scope of the Mercúrio Program, in order to identify the impacts of mining activities on indigenous peoples and riverside dwellers and to assess the environmental quality of tributary and main rivers in terms of the presence of contaminants” , informs Cinthia Masumoto, coordinator of Registration and Information on Remediation and Environmental Contamination at the institute.

Although it is a slow process, mercury poisoning of the environment is reversible, as long as the source of contamination is interrupted. “In the case of garimpos, illegal garimpos would have to be eliminated”, says Fostier. “In addition, there is the possibility of decontamination of specific sites. In industrial plants, for example, the contaminated soil may be removed. But this is very expensive and could hardly be implemented in the Amazon, precisely because of the environmental impact.”

The Planeta em Transe project is supported by the Open Society Foundations.

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