Presented paper

IMWA2019 Students work

Metal fluxes from the Tinto River (SW Spain) to the Atlantic Ocean: importance of flood events T

Ruiz Cánovas, Carlos; Basallote, Maria Dolores; Macías, Francisco; Olias, Manuel; Pérez López, Rafael; Nieto, Jose Miguel
University of Huelva (Spain), Spain

Flood events may play a key role in the metal transport fluxes from rivers to oceans. This is especially relevant in semi-arid and arid climate regions, which alternate long drought periods and short but intense rainfall events. During these events, most of the water discharge, dissolved contaminants, and suspended matter transport occurs. For this reason, the flood rainfall events need to be studied with a high temporal sampling resolution considering the great geochemical and hydrological variability observed in these episodes. These studies should be extended to large data series in order to assess the impact of flood events on metal fluxes upon different hydrological regimes. Changes in metal transport patterns associated with climate and land use changes such as closure or reopening of mines and adoption of remediation measures in mine sites should be also addressed.

The most outstanding example is the Tinto River, in which the metal content delivered to the Atlantic Ocean during the first flood events is 3 order of magnitude higher in the rainy season than during the entire dry season. The current study provides information on the metal transport from the Tinto River to the Atlantic Ocean during high resolution samplings of different flood events for the periods 2004/06 and 2017/18. A comparison between flood events of both periods has been performed in order to evaluate the impact of the reopening of the Riotinto mines in 2017 on the metal fluxes in the Tinto River. Several flood events sampled during both periods allowed establishing several metal transport patterns upon different climatologic episodes, i.e. flash floods, cyclonic episodes, etc.

This study highlights the need to monitor the flood events in detail in other watersheds, especially those affected by mining in semi-arid and arid climates, in order to accurately quantify the annual pollutant transport budget from rivers to the Ocean. This information should be used to put into practice remediation measures to limit the release of these pollutants from mine sites to the ocean.