Tracing Copper Migration in the Tongling Area through Copper Isotope Values in Soils and Waters.

Jingwen Su,Peter D’Amico,Joaquin Ruiz,Ryan Mathur,Linda Godfrey,Shiming Song,Glen Brumm

doi:10.3390/ijerph15122661

Abstract

Copper mining in Tongling has occurred since the Bronze Age, and this area is known as one of the first historic places where copper has been, and is currently, extracted. Multiple studies have demonstrated, through concentrated work on soils and waters, the impact of mining in the area. Here we present copper isotope values of 13 ore samples, three tailing samples, 20 water samples (surface and groundwater), and 94 soil samples (15 different profiles ranging in depth from 0–2 m) from proximal to distal (up to 10 km) locations radiating from a tailings dam and tailings pile. Oxidation of the copper sulfide minerals results in isotopically heavier oxidized copper. Thus, copper sourced from sulfide minerals has been used to trace copper in mining and environmental applications. At Tongling, higher copper isotope values (greater than 1 per mil, which are interpreted to be derived from copper sulfide weathering) are found both in waters and the upper portions of soils (5–100 cm) within 1 km of the source tailings. At greater than 1 km, the soils do not possess heavier copper isotope values; however, the stream water samples that have low copper concentrations have heavier values up to 6.5 km from the source. The data suggest that copper derived from the mining activities remains relatively proximal in the soils but can be traced in the waters at greater distances.

Highlights

Tracing the release of metals due to mining practice is an essential activity to understand the overall ecological well-being of an area
The ranges of copper ores are in line with those previously reported for skarns and higher temperature mineralization systems as those present in Tongling [25,26,27,28,29,30]
The results presented show that copper derived from mining practices cause a dispersion of metal into the surrounding areas approximately 6 km down hydrogeological gradient, because the heavier copper isotope values diminish beyond this distance

Summary

Introduction

Tracing the release of metals due to mining practice is an essential activity to understand the overall ecological well-being of an area. Tongling has been an active mining area of a copper skarn deposit for over 3000 years, and multiple studies have shown metal dispersion related to mining with both concentration and isotope data from soils, waters, aerosols, and plants [1,2,3]. We use copper isotope compositions of soils and waters to trace Cu migration from an actively weathering tailings pile, along with assessing airborne contaminates (derived from a prevailing northwesterly wind) from a metal processing plant in Tongling (Figure 1). Transition metal and metal isotope geochemistry are relatively new techniques that have been applied to understand the rates, dispersion, and ability to trace sources of metal release induced by surface and subsurface mining activities. It has been shown that copper isotope values can provide key insights into the kinetics

Methods

Results

Discussion

Conclusion