Dissolved and particulate metals dynamics in a human impacted estuary from the SW Atlantic

Abstract

In order to evaluate metal behavior in urban stressed estuaries, the distribution of major elements (Feand Mn) and trace elements (Cd and Cu) between suspended particulate matter (SPM) and subsuperficialseawater in the Bahía Blanca Estuary, Argentina, was studied. Four different impacted areas were selectedto study the spatial and temporal distribution of these metals in an estuary in continuous industrialdevelopment and where an environmental law was implemented to supervise industrial discharges inwaters. Sampling was performed within intertidal areas. Physicochemical conditions usually influencethe partitioning of metals between the dissolved and particulate fraction thus, salinity, pH, turbidity,temperature and dissolved oxygen were also measured.Dissolved metals were analyzed with atomic absorption spectrophotometry (AAS) and the particulatefraction with inductively coupled plasma optical emission spectrometry (ICP OES). Metals concentrationranges, within the dissolved fraction (mg/L), were from below the method detection limit for all theelements to 4.7 in the case of Cd, 6.0 for Cu and 62 for Fe. Minimum and maximum values in the particulatefraction (mg/g, d.w.) were from below the method detection limit to 11 for Cd; from 24 to 220 forCu and from 630 to 1500 for Mn. For Fe, concentrations ranged from 2.2 to 9.6 (%). The general order ofthe dissolved/particulate partition coefficients (Log10Kds) for the studied metals, considering meanvalues, were: Fe (7.0) > Cu (4.2) > Cd (3.3).The metals values as well as the physicochemical parameters showed temporal variations and manycorrelations were found among them. Log10Kd Fe values were the highest, highlighting its strong affinityfor particles. Metals concentrations were sometimes higher than those from other polluted areas as wellas from previous studies from the same estuary, which highlights the potential impact of these elementsin the study area.The concentrations of particulate metals achieved in the present work were in some cases of higherranges than the previous from the same estuary and/or from other polluted estuarine environments.Thus, the environmental law that regulates the discharge of industrial waters appeared not to have aspecific impact on the metals concentrations found. Moreover, human activities that surround the estuaryand are in continue development should be considered as they might constitute a source of metalsfor the estuarine system.