Evaluation of mercury methylation and methylmercury demethylation rates in vegetated and non-vegetated saltmarsh sediments from two Portuguese estuaries
Autor: | Brian Dimock, Kevin Eckey, João Canário, Holger Hintelmann, Ana Maria Mota, Beatriz Ferreira Araújo, Ricardo Mendes, Rute Cesário |
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Rok vydání: | 2017 |
Předmět: |
Geologic Sediments
010504 meteorology & atmospheric sciences Health Toxicology and Mutagenesis chemistry.chemical_element 010501 environmental sciences Toxicology Methylation 01 natural sciences chemistry.chemical_compound Isotopes Methylmercury 0105 earth and related environmental sciences Demethylation geography geography.geographical_feature_category Portugal Stable isotope ratio Sediment Estuary Mercury General Medicine Methylmercury Compounds Plants Pollution Macrophyte Mercury (element) chemistry Wetlands Environmental chemistry Salt marsh Estuaries Water Pollutants Chemical Geology Environmental Monitoring Half-Life |
Zdroj: | Environmental Pollution. 226:297-307 |
ISSN: | 0269-7491 |
Popis: | Neurotoxic methylmercury (MMHg) is formed from inorganic divalent mercury (Hg2+). However, it is poorly understood to what extent different mercury (Hg) pools contribute to existent MMHg levels. In this study, ambient concentrations of total Hg (THg) and MMHg as well as rates of methylation and demethylation were measured simultaneously in sediments with and without salt-marsh plant vegetation, which were collected in Guadiana and Tagus estuaries, Portugal. Concurrent processes of Hg methylation and MMHg demethylation were directly monitored and compared by spiking sediments cores with stable isotope tracers of 199Hg2+ and CH3201Hg+ followed by gas chromatographic separation and isotope-specific detection using inductively coupled plasma mass spectrometry. Compared to the Guadiana estuary, where concentrations were comparatively low, THg and MMHg levels varied between vegetated and non-vegetated sediments collected at the Rosario site (ROS) of the Tagus estuary. Methylation (KM) and demethylation rates (KD) were also different between estuaries being dependent on the presence of vegetation. In addition, the type of macrophyte species influenced KM and KD values. In fact, the highest KM value was found in Sarcocornia fruticosa vegetated sediments at the Castro Marim site in Guadiana (CM, 0.160 day−1) and the lowest KM was observed in non-vegetated sediments at the Alcochete site in Tagus (ALC, 0.009 day−1). KD varied by a factor of three among sites with highest rates of demethylation observed in non-vegetated sediments in Guadiana (12 ± 1.3 day−1, corresponding to a half-life of 1.4 ± 0.2 h). This study clearly shows that the presence of vegetation in sediments favors the formation of MMHg. Moreover, this effect might be site specific and further studies are needed to confirm the findings reported here. |
Databáze: | OpenAIRE |
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