Combined use of native and transplanted moss for post-mining characterization of metal(loid) river contamination

Abandoned mine sites are a cause of great environmental concern, being potential sources of toxic elements for adjacent aquatic ecosystems with intrinsic difficulties for their management (i.e. episodic nature of pollution, technical difficulties and high costs of monitoring, remoteness). Aquatic macrophytes can find effective application in these situations, providing cost-effective data for instreamwater quality assessment. In this study, native and transplanted specimens of the aquaticmoss Platyhypnidium riparioides were used to evaluate metal(loid) contamination in a river receivingmultiple acidic andmetalliferous drainages from sulphide mineralized areas and derelictmines. Analysis of native P. riparioides thalli was used to identify, in the upland course of the river, the pattern of contamination (As, Cd, Cu, Pb and Zn) which was related to the geo-environmental features of thewatershed and the nearby historical mining areas. Attenuation of metal(loid) availability in the lowland river, apparently due to eco-hydrological and physicchemical processes, was also highlighted by spatial trends of concentrations data of native and transplanted moss. The latter, deployed for 21 days at specific stretches of the river and in a tributary hydrologically connected with a dismissed mine, supported the identification of point sources (i.e. mine effluents, metallurgical waste piles a massed on the banks of the river) and the reckoning of their quantitative impact on different segments of the watercourse. By exploring multi-elemental and native-to-transplant relationships, differences in metal(loid) accumulative capacities were recognized between sampled thalli and exposed moss bags in relation to the severity of the contamination. The observed discrepancy in the accumulation of As, Fe, Ni and Pb in highly contaminated areas between native and transplanted moss of P. riparioides raises questions on the possible competing mechanisms of element uptake and retention. These findings prompt studies to discern possible limitations of the transplanting moss technique under extreme stream-quality conditions. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

In this study, native and transplanted aquatic moss specimens were used to assess metal contamination in a river affected by acidic and metalliferous drainage from mining areas. The analysis identified patterns of contamination in the watershed and highlighted attenuation of metal availability downstream. Differences in metal accumulation capacities between native and transplanted moss raise questions about element uptake and retention mechanisms.