The potential wildfire effects on mercury remobilization from topsoils and biomass in a smelter-polluted semi-arid area. (May 2020)

• Record Type: Journal Article
• Authors: Tuhý, Marek; Rohovec, Jan; Matoušková, Šárka; Mihaljevič, Martin; Kříbek, Bohdan; Vaněk, Aleš; Mapani, Ben; Göttlicher, Jörg; Steininger, Ralph; Majzlan, Juraj; Ettler, Vojtěch
• Is Part Of: Chemosphere. Volume 247(2020)
• Publication Date: 2020-05
• Subjects: Mercury -- Topsoils -- Vegetation -- Wildfire -- Smelter pollution -- Semi-arid Namibia; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.125972
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Wildfires can be responsible for significant mercury (Hg) emissions especially in contaminated areas. Here, we investigated the Hg distribution in topsoils and vegetation samples and temperature-dependent Hg mobilization from biomass-rich topsoils collected near a copper (Cu) smelter in Tsumeb (semi-arid Namibia), where Hg-rich Cu concentrates are processed. The thermo-desorption (TD) experiments conducted on representative biomass-rich topsoils (3.9–7.7 mg Hg/kg) indicated that more than 91% of the Hg was released at ∼340 °C, which corresponds to the predominant grassland-fire conditions. The mineralogical investigation indicated that the Hg comes mainly from the deposited smelter emissions because no distinct Hg-rich microparticles corresponding to the windblown dust from the nearby disposal sites of the technological materials (concentrates, slags, tailings) were found. A comparison with the TD curves of the Hg reference compounds confirmed that the Hg in the biomass-rich topsoils occurs as a mixture of Hg bound to the organic matter and metacinnabar (black HgS), which exhibits similarities with the TD pattern of smelter flue dust residue. Despite the installation of a sulfuric acid plant in the smelter in 2015 and a calculated drop in the estimated Hg emissions (from 1301 ± 457 kg/y for the period 2004–2015 to 67 ± 5 kg/y after 2015), the Hg legacy pool in the smelter surroundings can potentially be re-emitted back to the atmosphere by wildfire. Using the Hg spatial distribution data in the area (184 km 2 ), the estimates indicate that up to 303 kg and 1.3 kg can be remobilized from the topsoils and vegetation, respectively. Graphical abstract: Image 1 Highlights: Wildfires can affect smelter-impacted soils and vegetation in semi-arid Namibia. Mercury released from contaminated biomass-rich topsoils at ∼340 °C. Smelter surroundings (184 km 2 ) contain ∼300 kg of Hg remobilizable by wildfire.