Source identification of Zn in Erren River, Taiwan: An application of Zn isotopes

Source identification of environmental pollutants is critical for pollution prevention and controlling. In this work, Zn isotopic compositions and Zn spatial distribution from headwater to estuary of Erren River (ER) catchments (southern Taiwan) were systematically investigated as a potential source tracer for distinguishing natural weathering and anthropogenic activities. Industrial wastewaters/effluents including leather, printed circuit board (PCB), metal surface treatment (MST), semiconductor wafer (SCW), and electroplating (EP) industries were collected and analyzed as the potential sources of Zn isotopic database. Results implied that MST wastewaters/effluents had the lowest δ⁶⁶Zn values (Zn isotopic composition) in the range of -0.40 to +0.04. Oppositely, high Zn isotopic composition was observed in leather (δ⁶⁶Zn = +0.41 to +0.71) and EP wastewaters/effluents (δ⁶⁶Zn = +0.54 to +1.84). Significantly, the plot of δ⁶⁶Zn versus 1/Zn clearly indicates that riverine Zn isotope in the ER waters (-0.73 to 1.77‰) can be simply explained by at least three end-member mixing which contains EP, MST wastewaters, and natural component. Our data importantly proved that Zn isotopic composition is a powerful tracer for distinguishing different Zn sources of anthropogenic pollution in rivers.