Environmental Science and Pollution Research

, Volume 23, Issue 11, pp 10529–10541 | Cite as

Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania)

  • Andrea G. Bravo
  • Jean-Luc Loizeau
  • Perrine Dranguet
  • Stamatina Makri
  • Erik Björn
  • Viorel Gh. Ungureanu
  • Vera I. Slaveykova
  • Claudia CosioEmail author
Recent sediments: environmental chemistry, ecotoxicology and engineering


Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out.


Bacterial activity Biota Dispersion Methylmercury Reservoir Sediments Water 



This work is part of the Romanian–Swiss Research Program with the project number IZERZO-142228, funded by the Swiss National Science Foundation (SNF) and Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI). The work was also partially supported by the SNF (project 205321_138254) and Swedish Research Council (project 623-2011-7191). We thank the National Administration Apele Romane Olt for permission to work in their laboratory, GeoEcoMar for providing the boat, Aline Freiburghaus and Dany Dumitru Grosu for support and help during the sampling, Dolly Kothawala for English editing and improvement.

Supplementary material

11356_2015_5906_MOESM1_ESM.docx (29 kb)
Table S1 Sequences and characteristics of primers used to analyze the microbial activity by RT-qPCR. (DOCX 29 kb)
11356_2015_5906_MOESM2_ESM.xlsx (19 kb)
Table S2 Pearson correlation coefficients (α = 0.05) between water surface sediments, transcripts’ abundance, and biota sampled in several reservoirs along the Olt River (Romania) during field campaign in September 2014. Coefficients higher than 0.75 are shown in bold. (XLSX 18 kb)
11356_2015_5906_MOESM3_ESM.docx (20 kb)
Table S3 Pearson correlation coefficient (α = 0.05) between sediments and transcripts’ abundance in sediments sampled in several reservoirs along the Olt River (Romania) during field campaign in September 2014. Coefficients higher than 0.75 are shown in bold. (DOCX 19 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Andrea G. Bravo
    • 1
  • Jean-Luc Loizeau
    • 2
  • Perrine Dranguet
    • 2
  • Stamatina Makri
    • 2
  • Erik Björn
    • 3
  • Viorel Gh. Ungureanu
    • 4
    • 5
  • Vera I. Slaveykova
    • 2
  • Claudia Cosio
    • 2
    Email author
  1. 1.Limnology/Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
  2. 2.Institute F.-A. Forel, Earth and Environmental SciencesUniversity of GenevaVersoixSwitzerland
  3. 3.Department of ChemistryUmeå UniversityUmeåSweden
  4. 4.Faculty of Geology and GeophysicsUniversity of BucharestBucharestRomania
  5. 5.GeoEcoMarNational Research and Development Institute for Marine Geology and GeoecologyBucharestRomania

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