MERCURY IN THE SEDIMENT OF THE UPPER PARNAÍBA RIVER

Marcelo B Remor,Fagner G Da Conceição,Silvio C Sampaio,Kathleen J Model,Cristiane L Paloschi,Danielle M Rosa

doi:10.1590/1809-4430-eng.agric.v38n5p760-767/2018

Abstract

ABSTRACT The contamination of aquatic environments with chemical trace elements can be evaluated by their accumulation in sediments of the water body. Studies on mercury require the use of exclusive extraction techniques that have relatively high costs when compared to the analysis of other trace elements. This study was conducted aiming at determining the mercury concentration in sediments of the Upper Parnaiba River basin, located in a region of agricultural expansion between the states of Piaui and Maranhao. The sediment was collected at 12 sites in the basin. After drying, the quantification of total mercury was performed by the Zeeman atomic absorption spectrometry coupled to a pyrolysis reactor. Mercury concentrations in sediments of the Parnaiba River ranged from 4.2 to 58.5 ng g−1 and presented a low probability of adverse effects on biota. Mercury had no correlation with the variables clay, silt, sand, total organic carbon, iron, and aluminum, demonstrating its possible anthropogenic origin. Although mercury concentrations have a low probability to disturb the balance of the local ecosystem, there is a need for monitoring the region in order to quantify the risks to biota and human health.

Highlights

The Parnaíba River basin is the second most important in the Northeast of Brazil, located in a region of expansion of the agricultural frontier in the CentralNortheastern direction called Matopiba, which covers the states of Maranhão, Tocantins, Piauí, and Bahia (Freitas & Mendonça, 2016; Santos, 2015, Garcia & Buainain, 2016)
The hydrodynamics of all sampled sites is high according to the Pejrup diagram (Figure 2B)
PC1 separated the sampled sites into three groups: the first group was composed of S1 and S12 and presented the highest values of silt, clay, total organic carbon (TOC), Al, and Fe; the second group was composed of S3, S5, S6, S7, S8, and S10 and presented the highest values of sand; and the third group was composed of S2, S4, S9, and S11 and presented intermediate values for the variables that compose PC1 (Figure 3)

Summary

Introduction

The Parnaíba River basin is the second most important in the Northeast of Brazil, located in a region of expansion of the agricultural frontier in the CentralNortheastern direction called Matopiba, which covers the states of Maranhão, Tocantins, Piauí, and Bahia (Freitas & Mendonça, 2016; Santos, 2015, Garcia & Buainain, 2016). Mercury concentrations in the environment become worrying due to their toxicity, persistence, bioaccumulation capacity, and biomagnification, causing adverse effects to the environment and human health (Kim et al, 2016; Selin, 2014). These effects on organisms exposed to mercury depend primarily on its chemical form and concentration in the environment, the route of exposure to the agent, and the difference in vulnerability between exposed organisms (Kim et al, 2016). High mercury concentrations cause disturbances in the central and immune systems, kidneys, heart, reproductive, and genetic problems, and reductions in cognitive functions (Oliveira et al, 2013; Gibb & O’Leary, 2014)

Objectives

Methods

Results