Assessment of water quality and macroinvertebrates at sites upstream and downstream of the inflow of treated mine drainage: A case study of Yoshino legacy mine

Abstract

We aimed to investigate the changes in water quality and benthic macroinvertebrates at two sites (N1 and N2) downstream and upstream of the inflow of treated mine discharge from a legacy mine (Yoshino mine located in Akita prefecture) in the Naruse river. Based on field surveys conducted in spring (May) and fall (October) 2022, detectable increases in dissolved concentrations of trace metals (Cu, Zn, Cd, and Pb) were observed at the downstream site (N2) but those concentrations were well below the U. S. water quality criteria. In addition, reductions of richness (number of taxa) and abundances (number of individuals) of metal-sensitive mayflies were not detected at the downstream site, and most of the richness and abundance metrics for macroinvertebrates showed no significant difference between the two sites.