Mercury and halogen emissions from Masaya and Telica volcanoes, Nicaragua

Abstract

We report measurements of Hg, SO 2 , and halogens (HCl, HBr, HI) in volcanic gases from Masaya volcano, Nicaragua, and gaseous SO 2 and halogens from Telica volcano, Nicaragua. Mercury measurements were made with a Lumex 915+ portable mercury vapor analyzer and gold traps, while halogens, CO 2 and S species were monitored with a portable multi gas sensor and filter packs. Lumex Hg concentrations in the plume were consistently above background and ranged up to 350 ng m −3 . Hg/SO 2 mass ratios measured with the real‐time instruments ranged from 1.1 × 10 −7 to 3.5 × 10 −5 (mean 2 × 10 −5 ). Total gaseous mercury (TGM) concentrations measured by gold trap ranged from 100 to 225 ng m −3 . Reactive gaseous mercury accounted for 1% of TGM, while particulate mercury was 5% of the TGM. Field measurements of Masaya's SO 2 flux, combined with the Hg/SO 2 ratio, indicate a Hg flux from Masaya of 7.2 Mg a −1 . At Masaya's low temperature fumaroles, Hg/CO 2 mass ratios were consistently around 2 × 10 −8 , lower than observed in the main vent (Hg/CO 2 ∼ 10 −7 ). Low‐temperature fumarole Hg fluxes from Masaya are insignificant (∼150 g a −1 ). Ratios of S, C and halogen species were also measured at Masaya and Telica volcanoes. CO 2 /SO 2 ratios at Masaya ranged from 2.8 to 3.9, comparable to previously published values. At Masaya molar Br/SO 2 was 3 × 10 −4 and I/SO 2 was 2 × 10 −5 , suggesting fluxes of 0.2–0.5 Mg HBr d −1 and 0.02–0.05 Mg HI d −1 . At Telica the Br/SO 2 ratio was also 3 × 10 −4 and the I/SO 2 ratio was 5.8 × 10 −5 , with corresponding fluxes of 0.2 Mg HBr d −1 and 0.06 Mg HI d −1 . Gases at both volcanoes are enriched in I relative to Br and Cl, compared to gases from volcanoes elsewhere.