With time, the high initial acidity and metal concentrations of the first flush decay. The con- centrations often seem to follow a quasi-exponential decay curve, indicative of flushing out of accumulated oxidation products (“vestigial” acidity/contaminant loading) from the mine sys- tem with fresh recharge water. The concentrations tend, in the long term, towards a steady state contaminant loading that reflects new, ongoing (“juvenile”) acidity production from pyrite weathering.