Catchment scale variation of contaminants in glacial sediments from the Cordillera Blanca, Peru

Historically, glaciers have been seen as pristine environments. However, research has shown that glaciers can accumulate and store contaminants through processes such as atmospheric deposition, mass movements, and anthropogenic activities. Numerous anthropogenically and naturally-derived contaminants have been found within glacial sediments, including fallout radionuclides, potentially toxic elements, and heavy metals. The introduction of these contaminants often come from human activities such as the use of agricultural fertilisers, carbon based industries, vehicular use, and nuclear power plants. However, these contaminants can also originate from natural sources such as erosion of metal-rich rock and forest fires. Through mechanisms of secondary release, these often legacy contaminants are remobilized, finding their way into glacial riverine systems and downstream environments. This can then pose potential threats to human and ecosystem health, as well as impacting food quality, water resources, livelihoods, and social justice.

When assessing potential downstream risk from glacial contaminants, it is crucial to know what types of contaminants may be released in meltwaters and in what quantity. Here we identify contaminants in cryoconite – a sediment found on the surface of glaciers – in Peru’s Cordillera Blanca, from which meltwater feeds into the Rio Santa. Previous studies have shown that glaciers in similar environments (i.e. high mountain glacier catchments) have been found to contain differing types and concentrations of contaminants within cryoconite. However, until now this had not been reported for cryoconite on glaciers in Peru. This research investigates the variation in contaminant load in cryoconite from four different glaciers (Pastoruri, Shallap, Vallunaraju, and Yanapacca) within the Cordillera Blanca. Key contaminants in cryoconite from this region have been analysed using X-ray fluorescence, gamma spectrometry, and ICP-MS. These results contribute to an improved understanding of the extent to which glaciers may act as a secondary source of contaminants to the Rio Santa catchment. This is an important first step towards assessing the risk of contaminant release from glaciers in this region.