Measurements of Atmospheric Concentrations of Reduced Sulphur Compounds in the All Saints Bay Area in Bahia, Brazil

Abstract

Atmospheric concentrations of several reduced sulphur compounds (H2S, COS, CH3SH, CH3SCH3 ,C S 2) originating from both natural and anthropogenic sources were measured at a number of locations in the All Saints Bay area and Reconcavo Baiano, Brazil. The volatile reduced sulphur compounds were collected by pre-concentration using cryo-tubes. Analysis of these compounds was carried out at a later date using gas chromatography with a flame photometric detector. In areas dominated by biogenic sources, the COS concentration varied between 0.5 and 1.0 ppbv, consistent with its normal global distribution in the atmosphere. Areas without direct industrial influence showed low atmospheric concentrations for all volatile sulphur compounds (≤0.25 ppbv). The anthropogenic influence of the Petrochemical Complex in Camacari resulted in relatively high levels of some reduced sulphur compounds, such as COS (8 ppbv), CH3SH (1.50 ppbv), H2S (1.35 ppbv) and CS2 (0.3 ppbv). In mangrove areas, the H2S concentrations (0.2 ppbv) were almost twice as high as those in the air masses arriving from the Atlantic Ocean. The maximum H2S concentrations were found in the industrial area of the Petrochemical Complex in Camacari, but did not reach the limit of human perception (0.14 ppbv) and rarely reached the typical recognizable smelling level (0.40 ppbv). Industrial emissions from the Landulfo Alves Refinery increased the COS, DMS and CS2 concentrations to 2.0, 0.55 and 0.2 ppbv, respectively. Ke yw ords: anthropogenic sources, atmospheric concentrations, Brazil, mangrove areas, reduced sulphur compounds