Search

Graphical abstract Highlights • Inorganic mercury and methylmercury studied in sediments of contaminated lagoon. • Multiple regression model demonstrated different behavior for mercury species. • Inorganic mercury (IHg) depends on the distance to the IHg source and Al levels. • Methylmercury (MeHg) depends on IHg levels in contaminated sediments. • MeHg depends also on the levels of Ca (marine proxy), Mn and organic matter. Abstract The concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in surface sediments from the contaminated Aveiro Lagoon (Portugal) were determined by species-specific isotope dilution analysis. Different behaviour of IHg and MeHg was observed based upon multiple regression analysis, including geochemical characteristics of the surface sediments (fine fraction, concentrations of organic matter and metals) and non-Euclidean distances between sampling points. This data treatment method was valid over the entire concentration range of IHg and MeHg, allowing robust quantitative evaluation with respect to extrapolation. For IHg, there was statistical separation of the dispersion away from the contamination source and of Al concentration in the sediments. The MeHg concentrations followed those of IHg at high concentrations. The geochemical variables, such as concentrations of Ca (marine influence proxy), Mn and organic matter, were necessary to describe the behaviour of MeHg across the whole concentration range. The models for MeHg demonstrated that, close to the mouth of the lagoon, net production of MeHg was higher. In future, multiple regression analysis could be applied to separate and to evaluate quantitatively the effects of geochemistry and dispersion away from the contamination source in sediments contaminated with other substances. [ABSTRACT FROM AUTHOR]

Spatial and seasonal variation of mercury species aqueous concentrations and distributions was carried out during six sampling campaigns at four locations within Laranjo Bay, the most mercury-contaminated area of the Aveiro Lagoon (Portugal). Inorganic mercury (IHg(II)) and methylmercury (MeHg) were determined in filter-retained (IHg PART , MeHg PART ) and filtered (<0.45 μm) fractions (IHg(II) DISS , MeHg DISS ). The concentrations of IHg PART depended on site and on dilution with downstream particles. Similar processes were evidenced for MeHg PART , however, its concentrations increased for particles rich in phaeophytin (Pha). The concentrations of MeHg DISS , and especially those of IHg(II) DISS , increased with Pha concentrations in the water. Multiple regression models are able to depict MeHg PART , IHg(II) DISS and MeHg DISS concentrations with salinity and Pha concentrations exhibiting additive statistical effects and allowing separation of possible addition and removal processes. A link between phytoplankton/algae and consumers’ grazing pressure in the contaminated area can be involved to increase concentrations of IHg(II) DISS and MeHg PART . These processes could lead to suspended particles enriched with MeHg and to the enhancement of IHg(II) and MeHg availability in surface waters and higher transfer to the food web. [ABSTRACT FROM AUTHOR]