『Abstract
Based on back scattered electron images and electron microprobe
analysis results, four alteration layers, including a transition
layer, a reticulated ferric oxide layer, a nubby ferric oxide
layer and a cellular ferric oxide layer, were identified in the
naturally weathering products of pyrite. These layers represent
a progressive alteration sequence of pyrite under weathering conditions.
The cellular ferric oxide layer correlates with the strongest
weathering phase and results from the dissolution of nubby ferric
oxide by acidic porewater. Leaching coefficient was introduced
to better express the response of element mobility to the degree
of pyrite weathering. Its variation shows that the mobility of
S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite
is oxidized to sulfuric acid and sulfate that are basically released
into to porewater, and heavy metals Co and Bi are evidently released
by acid dissolution. As, Cu and Zn are enriched in ferric oxide
by adsorption and by co-precipitation, but they would re-release
to the environment via desorption or dissolution when porewater
pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may
pose a substantial impact on water quality. Considering that metal
mobility and its concentration in mine waste are two important
factors influencing heavy metal pollution at mining-impacted sites,
Bi and Co are more important pollutants in this case.
Keywords: Environmental implications; Element mobility; Pyrite
weathering』
Introduction
Site description
Materials and methods
Element mobility index: leaching coefficient
Results and discussion
Alteration layers of the weathered pyrite
Environmental mobility and its environmental effect
Mechanism of element transfer or transport
Conclusions
Acknowledgements
References