The Junín Lake basin, also called Chinchaycocha, lies in the Peruvian highlands at 4,100 metres above sea level. It is the second largest body of water in Peru, the source of the Mantaro River and part of the Junín National Reserve. A study published in Science of the Total Environment reports critical contamination by several toxic metals and metalloids across the basin.
Researchers from the National Institute of Agricultural Innovation of Peru and the National University Toribio Rodríguez de Mendoza tested more than 200 surface soil samples around the lake. They measured 14 heavy metals, metalloids and trace elements, and mapped their distribution, ecological risk and human health implications. The analysis combined grid sampling points and machine learning with environmental variables such as flooding to identify contamination patterns.
The study found that 99 per cent of the area shows "very high to ultra-high" ecological risk and reports a "100 per cent carcinogenic risk" for adults. It notes that children are highly exposed to arsenic and that arsenic, lead, cadmium and zinc substantially exceed ecological and human health thresholds. In agricultural areas the toxins exceeded ecological thresholds by more than 100 times. Samuel Pizarro, one of the authors, said: “The levels of arsenic are extremely high, as are those of lead and cadmium, far exceeding acceptable thresholds.” He also warned that chromium levels are significant and pose a serious threat to human health.
Authors describe a bioaccumulation process: animals consume contaminated fodder, which affects local food and exposes people who use the land and water. They link contamination to mines abandoned for a century or more, and to agriculture and urbanisation. With a mining tradition of more than 300 years, the basin has become a sink for metals and metalloids that accumulate in water, sediments and grazing soils.
The area directly hosts about 50,000 people in urban and rural communities, and the authors note the impact reaches 1.3 million people because some of the water is used downstream in valleys and in dams. The team says further work is needed to calculate the full size of that impact and the effects on children and pregnant women. Anna Heikkinen, a researcher not involved in the study, said the findings match her work and called mining-related contamination a serious ecological, socio-economic and health risk. The regional environmental authority for the Junín area did not respond to requests for comment on the study's findings.
Difficult words
- basin — low area where water collects
- contamination — presence of harmful substances in something
- metalloid — element with properties between metal and nonmetalmetalloids
- bioaccumulation — build up of chemicals in animals over time
- carcinogenic — likely to cause cancer in humans
- threshold — limit above which harm is expectedthresholds
- sediment — solid material that settles in watersediments
- fodder — food especially dried plant food for animals
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What short-term and long-term effects might this contamination have on people who live and farm around the lake? Give reasons from the article.
- What actions could local or national authorities take first to reduce risks to children and pregnant women in the affected area?
- How could abandoned mines continue to affect water and soil, and what practical challenges might make cleanup difficult?
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