Approved Abstracts

Ecological risk assessment of metals and As in the Limoncocha lagoon sediments, a Ramsar site in the Ecuadorian Amazon region

Author(s): Coral Carrillo K; Rodríguez-Romero A; Tovar-Sánchez A; Ruiz-Gutiérrez G; Galán Corta B; Viguri Fuente JR;
Presenter: Javier R. Viguri Fuente

Wetlands of international importance require regular reporting of key indicators to guide management and track ecosystem change effectively. Limoncocha Biological Reserve (Ecuador), a Ramsar site with high ecological and socioeconomic value, has a hydrologic system mainly formed by two rivers that drain into the Limoncocha lagoon, which concentrates increasingly anthropic activities. A strategy based on the application of a combination of single and integrated indices has been widely enforced in order to obtain a more accuracy assessment of the studied area.This study assess the ecological risk of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V and Zn in sediments of the Limoncocha lagoon applying single and integrated pollution indices based on background values, on the reference element and the background concentration, indices including toxic response and indices based on the Sediment Quality Guidelines. Seven sediment sites were analysed for metal(oid)s by ICP-MS. The contamination factor (Cf_(i,j)) and the enrichment factor (Ef_(i,j)) are used as individual indices to estimate the degree of contamination of each potentially toxic element. The Nemerow Pollution Index (NPI_j), the modified Nemerow Pollution Index (mNPI_j), and the potential ecological risk index (RI_j), are used as integrated indices to determine the degree of contamination of the set of pollutants. The evaluation of the sediment quality with respect to potentially toxic elements is determined using freshwater Sediment Quality Guidelines (SQGs) based indices. Under this approach, the probable median effect level quotient mPELq, the effective range median mean quotient mERMq and the toxic risk index TRI based on TEL and PEL guidelines, have been used. Cf and Ef classify the sediment sites in the same contamination level, from a “low contamination” remote site, to the “moderate contamination” and “minor enrichment” of the remaining sites showing the same elements As, Cd and Zn as responsible of such as categorization. NPI and mNPI identify three groups of stations, the centre of the lagoon as “moderately polluted”, a remote site as “unpolluted” and the remaining five sites as “slightly polluted”. In contrast, RI, mPELq, mERMq and TRI classify homogeneously all sediment stations as “Low potential risk (RI<150)”, “Medium-low priority risk level (0.1 Cu ≈ Zn >> Cr > Pb ≈ As ≈ Cd as common behaviour in most of the sediment sites. The toxic risk index TRI classify all stations as “low toxic risk” except the remote site that shows not toxic risk. The overall cluster analysis of the integrated indices leads to Ni, Zn and Cu as priority pollutants because can occasionally be associated with adverse biological effects in the centre of the lagoon and in the most anthropized areas. These are classified as moderately polluted with a medium-low priority risk level. This work provides an integrated analysis of contamination level and risk assessment indicators, which can be incorporated to the assessment and monitoring program of Limoncocha lagoon sediments quality. Ni, Cd and Cr due to the high baseline values in comparison with SQGs, and Cu, Zn due to their potential risk should be of special attention.

Funding: Dr. Araceli Rodríguez-Romero is supported by the Spanish grant Juan de la Cierva Incorporación referenced as IJC2018–037545-I.

Keywords: Sediment Quality Guidelines; Pollution Indices; Monitoring Program




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