Mercury emission from industrially contaminated soils in relation to chemical, microbial, and meteorological factors. (July 2019)

• Record Type: Journal Article
• Authors: Osterwalder, Stefan; Huang, Jen-How; Shetaya, Waleed H.; Agnan, Yannick; Frossard, Aline; Frey, Beat; Alewell, Christine; Kretzschmar, Ruben; Biester, Harald; Obrist, Daniel
• Is Part Of: Environmental pollution. Volume 250(2019)
• Page Start: 944
• Page End: 952
• Publication Date: 2019-07
• Subjects: Air-surface exchange -- Flux -- Soil -- Contamination -- Bacteria -- merA; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2019.03.093
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The Minamata Convention entered into force in 2017 with the aim to phase-out the use of mercury (Hg) in manufacturing processes such as the chlor-alkali or vinyl chloride monomer production. However, past industrial use of Hg had already resulted in extensive soil pollution, which poses a potential environmental threat. We investigated the emission of gaseous elemental mercury (Hg 0 ) from Hg polluted soils in settlement areas in the canton of Valais, Switzerland, and its impact on local air Hg concentrations. Most soil Hg was found as soil matrix-bound divalent Hg (Hg II ). Elemental mercury (Hg 0 ) was undetectable in soils, yet we observed substantial Hg 0 emission (20–1392 ng m −2 h −1 ) from 27 soil plots contaminated with Hg (0.2–390 mg Hg kg −1 ). The emissions of Hg 0 were calculated for 1274 parcels covering an area of 8.6 km 2 of which 12% exceeded the Swiss soil remediation threshold of 2 mg Hg kg −1 . The annual Hg 0 emission from this area was approximately 6 kg a −1, which is almost 1% of the total atmospheric Hg emissions in Switzerland based on emission inventory estimates. Our results show a higher abundance of Hg resistance genes ( merA ) in soil microbial communities with increasing soil Hg concentrations, indicating that biotic reduction of Hg II is likely an important pathway to form volatile Hg 0 in these soils. The total soil Hg pool in the top 20 cm of the investigated area was 4288 kg; hence, if not remediated, these contaminated soils remain a long-term source of atmospheric Hg, which is prone to long-range atmospheric transport. Graphical abstract: Image 1 Highlights: Long-term contamination of Hg in soils results in substantial Hg 0 emission to air. Emission of Hg 0 increases daily average ambient Hg 0 concentrations by about five times. Hg 0 emission occurs although Hg 0 was undetectable (<0.1 mg kg −1 ) in soil. Positive correlation between merA gene copies and contamination indicates biotic Hg II reduction. Topsoil excavation will reduce Hg 0 emission and long-range transboundary air pollution. Abstract : Long-term industrial Hg contamination of soils and biotic reduction of Hg II resulted in atmospheric emissions of 6 kg Hg a −1 from an area of 8.6 km 2 . Relative to background concentrations, ambient Hg 0 was elevated by up to fourteen times.