Soil contamination by copper: Sources, ecological risks, and mitigation strategies in Brazil

Background: Several activities can build up soil copper (Cu) concentrations leading to incorporation into the food chain and adversely affect natural and managed ecosystems. This study provides a synthesis of Cu sources, ecological risks, and mitigation strategies of Cu-contaminated soils in Brazil. Methods: A systematic data search was conducted based on publications from three databases. Data on Cu contamination in Brazilian soils were collected from selected publications; descriptive statistics, regressions, and geo-accumulation indices were obtained. Ecological risks and remediation methods were identified. Results: Based on total soil Cu concentrations and the geo-accumulation index (Igeo), it was evident that some Cu sources are more problematic for soils. These sources include antifouling paint particles (Igeo = 9.5), tailings from Cu mining (Igeo = 2.8), and Cu-based fungicides applied to vineyards/orchards (Igeo = 1.8). Other Cu sources such as organic waste, solid waste, dust fallout, and metal scraps have generally resulted in moderate to low levels of soil contamination. Soils contaminated by Cu can also impact water since soil erosion carries elements into water bodies. Contaminated environments may lead to increased Cu absorption by organisms, which pose ecological risks. Reference values of total Cu concentrations used for assessing soil quality have been proposed for almost half of Brazilian states. The most prescribed Cu mitigation actions for soil amelioration are phytomanagement with non-accumulator cover crops or native plant species that can accumulate up to 1000 mg Cu kg−1 in roots/stems combined with liming/fertilization and microbial inoculation. Conclusion: The most Cu contaminated sites in Brazil occur on soils affected by Cu mine tailings and vineyards where Cu-based fungicides have been applied for several decades, which results in environmental, social, economic, and health issues. Strategies have been proposed for the mitigation of Cu contaminated soils, mainly phytomanagement options. However, there is still a strong need for joint efforts by public and private sectors to implement remediation practices on contaminated soils and to prevent Cu contamination of new areas.