Heavy metals in Venezuelan marine sediments: concentrations, degree of contamination, and distribution

Ruth Ramos,Elia M García,Alejandra Verde

doi:10.7773/cm.v47i3.3124

Abstract

Venezuelan oil exploration and exploitation activities have been taking place since the 18th century. These long-term activities are closely related to heavy metal contamination because of the increasing input of toxic pollutants. Variations in heavy metal concentrations can cause, among other things, changes in metal distribution patterns, alterations in biogeochemical cycles, and increments in environmental and biological risks. The need for a complete baseline on heavy metal concentrations along the Venezuelan coast is critical. For this reason, we present the concentrations, distribution, and degree of contamination of 9 heavy metals (barium, mercury, copper, nickel, chromium, cadmium, zinc, lead, and vanadium) in marine sediments along the Venezuelan coast. We used the enrichment factor, the geoaccumulation index, and the mean effects range median quotients to evaluate the degree of contamination, comparing areas with and without intervention. Our results indicate that higher concentrations of these heavy metals are associated with places with greater anthropic activity, especially on the central and eastern coasts of Venezuela. Only cadmium showed extremely severe enrichment and a high degree of contamination. The biohazard potential was between 12% and 30% and was primarily associated with locations having high oil activity, which suggests that these places must be monitored, given the potential hazard they represent. This work encompasses the distribution and concentration of 9 heavy metals along the Venezuelan coast and takes relevance as a baseline for heavy metal concentrations and pollution indicators in marine sediments for Venezuela and the Caribbean.

Highlights

Heavy metal contamination is a global problem as large amounts of these pollutants have been and continue to be released into the environment by industrial activities (Yuang et al 2014, Mahu et al 2015)
The concentration of metals varied in the different coastal localities and between intervened areas (IT) and non-intervened areas (NI) within each region
Los valores dados en las tablas de Turekian y Wedepohl (1961), que corresponden a sedimentos marinos, se utilizaron como valores de concentración de referencia en la corteza terrestre para estimar el grado de contaminación por metales

Summary

Introduction

Heavy metal contamination is a global problem as large amounts of these pollutants have been and continue to be released into the environment by industrial activities (Yuang et al 2014, Mahu et al 2015). The study of sediments as a record of contamination in marine environments has been widely used in environmental assessments, monitoring programs, and environmental risk assessments (Abrahim and Parker 2008, Muñoz-Barbosa et al 2012, Maanan et al 2014, Yuang et al 2014, Birch 2017); it requires reference values and comparisons with control sites in order to detect changes in pollutant concentrations. In Venezuela, oil exploration and exploitation began in 1878 (Lieuwen 1955), but it is offshore oil activities, which began about 20 years ago, that have rapidly increased the input of organic and inorganic pollutants in marine environments (GESAMP 2007, García et al 2011). Among the activities of greatest influence in the incorporation of metallic elements are the discharge of drilling gravel, which usually has high contents of barite, cadmium, and mercury (Olsgard and Gray 1995, Neff 2005); sediment dredging, which removes and exposes the entire sediment matrix that was at rest, increasing the bioavailability of some elements; and pipe laying and testing

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Results

Conclusion