Risk assessment and copper geochemistry of an orchard irrigated with mine water: a case study in the semiarid region of Brazil.

This study aimed to evaluate mine water reuse, elucidating the potential problems related to trace metal biogeochemistry focusing on Cu dynamics in water, soil, and plants. Water samples were collected from a Cu mine and a reservoir used to store mine water. Additional samples were taken from soils from an uncultivated area and a banana orchard (irrigated with mine water for at least 10 years) and plant from the irrigated area. The following parameters were analyzed: pH, redox potential, dissolved ions in water samples (e.g., Ca2+, Mg2+, Na+, K+, Cu2+, SO 4 2- , and Cl-), bioavailable Cu and Cu solid-phase fractionation (in soils and reservoir sediments samples), as well as Cu content in banana plants. Mine water presents high dissolved Cu concentration (mean 2.3 ± 0.0 mg L-1), limiting its use for irrigation. Water storage at the reservoir increased water quality, reducing dissolved Cu concentration (mean 0.2 ± 0.0 mg L-1), due to adsorption/precipitation as carbonates (mean 131.8 ± 24.6 mg kg-1), organic matter (mean 1526.2 ± 4.7 mg kg-1) and sulfides (mean 158.4 ± 56.9 mg kg-1). Despite higher water quality at the reservoir, the use of mine water increased the amount of bioavailable Cu in soils, which was primarily associated with organic matter. Increased bioavailable Cu in the soil did not increase the Cu content of banana leaves but resulted in high Cu content of roots and fruit, increasing the risk of toxicity for the population.

Copper release from waste rocks in an abandoned mine (NE, Brazil) and its impacts on ecosystem environmental quality.

This study aimed to estimate the impact of an abandoned copper (Cu) mine on ecosystem environmental quality, using integrated ecological and biogeochemical analyses. Through a controlled experiment, the amount of Cu released by waste rocks, Cu adsorbed in soils, Cu geochemical behaviour and its leached amount were measured. Furthermore, to investigate the impacts of mine drainage on the adjacent ecosystem, samples of sediments, water and aquatic macroinvertebrates were analysed. We found that waste rocks still have high Cu concentration even after 30 years under weathering, ranging from 7782 to 8717 mg kg-1, associated mainly with carbonates, amorphous oxides and sulphides. It was estimated that 7.2 tonnes of Cu were released by waste rocks into the environment over last 30 years. The concentration of Cu observed in Ubari stream water was (

Geochemical speciation and dynamic of copper in tropical semi-arid soils exposed to metal-bearing mine wastes.

The potentially hazardous effects of rock wastes disposed at open pit in three different areas (Pr: Ore processing; Wr: Waste rock and Bd: Border) of an abandoned copper mine were evaluated in this study, with emphasis on acid drainage generation, metal contamination and copper geochemical dynamics in soils. Samples of waste rock were analyzed by Energy dispersive X-ray fluorescence (XRF), scanning electron microscopy with microanalysis (SEM-EDS) and X-ray diffraction (XRD). Soil samples were analyzed to determine the total metal contents (XRF), mineralogy (XRD), pH (H2O and H2O2), organic and inorganic carbon, % of total N, S and P, particle size, and a sequential extraction procedure was used to identify the different copper fractions. As a result of the prevalence of carbonates over sulphides in the wastes, the soil pH remained close to neutral, with absence of acid mine drainage. The geochemical interaction between these mineral phases seems to be the main mechanism to release Cu(2)(+) ions. Total Cu in soils from the Pr area reached 11,180mg.kg(-1), while in Wr and Bd areas the values reached, on average, 4683 and 1086mg.kg(-1), respectively, indicating a very high level of soil contamination. In the Pr and Wr, the Cu was mainly associated with carbonates and amorphous iron oxides. In the Bd areas, the presence of vegetation has influenced the geochemical behavior of copper by increasing the dissolution of carbonates, affecting the buffer capacity of soils against sulphide oxidation, reducing the pH levels and enhancing the proportion of exchangeable and organic bound Cu. The present findings show that the use of plants or organic amendments in mine sites with high concentration of Cu carbonate-containing wastes should be viewed with caution, as the practice may enhance the mobilization of copper to the environment due to an increase in the rate of carbonates dissolution.