The contamination product of environmental liabilities in Peru, represents an environmental concern, due to the risk associated with the high toxicity, long persistence, and non-biodegradability of the toxic elements that may be present and cause alterations in the biological and physicochemical properties of the ecosystem and induce harmful effects both for flora and fauna, as well as for human health.
The environmental liabilities studied are located in high Andean areas close to peasant communities (associated with economic activities of agriculture and livestock) where high concentrations of arsenic, lead, cadmium, and free cyanide have been found that exceed the limits established by Peruvian regulations. This may be due to the extraction process of copper and sulfur minerals, which are subjected to a grinding, smelting, and refining process, generating waste in each of these stages (Issaka and Ashraf 2021). It can also be due to the incomplete closure of the mine or an inadequate recovery of the mineral, the lack of compliance with environmental policies by the operators (Issaka and Ashraf 2021), in the development of the activities of the extractive process, which represents a risk for the ecosystem (Mayes and Jarvis 2011; Issaka and Ashraf 2021) and human health (Bini et al. 2017). When evaluating the toxic elements and the contamination indexes in the 5 environmental liabilities of mining origin, it was obtained that the areas of Chulluncane and Cercana present high and alarming contents of As, Cd, and Pb. However, when evaluating environmental indexes, Hg is also included as a polluting agent, because these elements are found with high and extreme contamination, resulting in both contaminated areas, which may be due to the development of anthropogenic activities such as industrial mining, the accumulation, discharge of mining waste as reported by other authors (Huang 2014; Zakir et al. 2015; YUAN et al. 2017; Chen et al. 2021; Akpambang et al. 2022) High concentrations of toxic metals, such as As, can cause negative health effects with a possible carcinogenic risk (Gupta et al. 2014). As may be associated with the copper extraction process (Valenzuela et al. 2000), as reported in other investigations that evaluated the concentration of arsenic in abandoned mines and tailings impoundment areas (Garcia-Sanchez and Alvarez-Ayuso 2003); (Razo et al. 2004). On the other hand, the high concentrations of Pb and Cd may be due to a large amount of slag from mining residues or from the mining extraction process itself, similar to what has been reported in other studies (YUAN et al. 2017; Candeias et al. 2018; Abouian Jahromi et al. 2020; Chen et al. 2021) Concerning this topic, the high availability of Hg in the environment is associated with sulfur concentrations and pH, producing greater bioavailability, and being able to form soluble or solid complexes (De Astudillo et al. 2008). In addition, there is the possibility that metals are mobilized due to biogeochemical processes associated with them and come into contact with water bodies and soils (Asmoay et al. 2019; Oyewo et al. 2020; Pabón et al. 2020). However, Hg tends to decrease when moving away from the contamination source, due to low mobility (Camargo et al. 2013).
The high rates of free CN in Tutupaca, Yucamane, and Cano are alarming since they indicate that the free cyanide present is extremely polluting. Therefore, when cyanide ions are transferred from sediments to water or aquatic systems through mutual interaction, they can affect the health of local people as well as natural ecosystems, with natural weathering being a factor that has been related to the release. to the environment and increased concentration in the soil of toxic contaminants present in tailings and mining waste (Abdulnabi et al. 2020; Chen et al. 2021). In addition, the presence of complexes (metal-cyanide) makes essential metals unavailable to soil organisms, thus altering the ecosystem due to the persistence of heavy metals and their non-biodegradability (Demková et al. 2017). This is worrying in the areas surrounding Cano and Yucamane due to the presence of nearby populations, as well as rivers, wetlands, and agricultural and grazing activities.
Likewise, the I-geo, Cf, and PLI contamination indexes showed the 05 high Andean zones present some level of contamination by one or more contaminants, which are directly related to the availability and extractive activity of copper, sulfur and acidic pH of the study areas, which suggests a deterioration of the soil. However, the effect of runoff through the rains and nearby rivers can cause the mobilization of contamination towards the environment of the surrounding communities such as the Cano and Yucamane peasant communities, constituting a potential risk for the infiltration and reaction of mining waste with the surrounding natural watercourses (Oyarzún et al. 2011).
It is important to consider the evaluation and characterization of mining environmental liabilities that will allow the development of approaches, ecological techniques, and scenarios to formulate policies that promote their mitigation, containment, and elimination in an economically viable way (Kumar et al. 2020). Among the conventional techniques that could be used for the treatment of heavy metals are adsorption, electrodialysis, precipitation, and ion exchange, but they have disadvantages because they cannot eliminate heavy metals that are in low concentrations, they are sensitive to pH, have a high cost, are usually slow and inefficient, and generate contaminated sludge that requires careful disposal, among other aspects (Kapahi and Sachdeva 2019).
In this sense, the use of technologies based on bioremediation, nanotechnology, bioventilation, biospray, biostimulation, bioaugmentation, and phytoremediation, could be efficient in mitigating contamination in the mining environmental liabilities studied (Kapahi and Sachdeva 2019; Roychowdhury et al. 2019; Subramaniam et al. 2019; Alharbi et al. 2020; Tahir et al. 2020; Sayqal and Ahmed 2021). Bioremediation requires less labor, is economical, ecological, sustainable, and relatively easy to implement, although it has the disadvantage of being slow, and time-consuming. In some cases, is required the treatment of toxic elements generated in the biodegradation process (Sayqal and Ahmed 2021). In addition, soil replacement, surface layer improvements, compatible land covers (surface coating), soil washing, use of organic matter, and planting of native or exotic species, among others, (Prieto Méndez et al. 2018; Sen Gupta et al. 2020; Peco et al. 2021; Adnan et al. 2022; Durante-Yánez et al. 2022; Lin et al. 2022) can be integrated perfectly with before mentioned techniques and accelerate the recovery processes of contaminated soils.
There is no recipe to solve this problem, however, it is possible to use different integrated technologies that allow accomplishing solutions in the short, medium, and long term to ensure that the ecosystem sustainably recovers its ecological integrity (Lin et al. 2017). The strategies to be used depending on the characteristics of the area, and the level and type of contamination of the site.