Site-specific P absorbency of ochre from acid mine-drainage near an abandoned Cu-S mine in the Avoca-Avonmore catchment, Ireland

Acid mine-drainage from an abandoned Cu-S mine adit, located in the Avoca- Avonmore catchment in the southeast of Ireland, results in low-value ochre deposition. Ochre found on-site had similar physical (particle size 97.7% <2 mm and dry bulk density 0.8 g cm³), but dissimilar maximum P-retention characteristics (16-21 g P kg^-1) to coal-mining ochre found in the UK. Stereomicroscopy identified oolites and diatoms in the ochre that were indicative of acidic environments. X-ray diffraction showed Fe mineralogy consisting of goethite, jarosite and minor amounts of ferrihydrite. Investigations by inductively coupled plasma-mass spectrometry and bulk energy-dispersive spectroscopy showed potentially toxic concentrations of Fe, Zn, Pb, As and Cu. Rapid mobilization of metals occurred during P-adsorption tests, which makes Avoca ochre unsuitable for use in a surface-water environmental technology.