Measurements of Reduced Sulphur Compounds in an Industrialized Tropical Region—Cubatão (BRAZIL)

Abstract

Ambient concentrations of SO₂, H₂S, COS and CS₂ have been determined at various sites in the highly industrialized area of Cubatão (Brazil) and in adjacent ecosystems during the years 1990 to 1993. Sulphate has been analyzed in rain samples collected at three sites in the Serra do Mar. The sites are called Vale do Mogi (heavily polluted), Paranapiacaba (moderately polluted), and Vale do Pil[otilde]es (less polluted). Gas exchange of reduced sulphur compounds between biosphere and atmosphere has been examined with the aid of ambient air enclosures. The investigated sulphur sources (and sinks) were the estuaries south of Cubatão, a reservoir north of Cubatão, and vegetated soils at Vale do Mogi, Paranapiacaba, and Vale do Pil[otilde]es. The content of reduced sulphur compounds was determined in surface water samples from lakes, rivers, and estuaries in the area under investigation.

Wet sulphate deposition and ambient SO₂ concentrations revealed a similar hierarchy of Vale do Mogi, Paranapiacaba, and Vale do Pil[otilde]es confirming the assumed pollution levels. In addition all investigated sites showed considerably elevated ambient concentrations of H₂S, COS, and CS₂ when exposed to industrial emissions. Emissions from biogenic sources are dominant over the Billings reservoir and over the estuaries. Flux measurements showed emissions of DMS and CH₃SH from vegetated soils. Deposition or uptake were observed with respect to H₂S, COS, and CS₂ mainly due to high ambient concentrations of these gases. DMS, COS, and CH₃SH were present in most of the water samples analysed. Maximum DMS concentrations have been detected in anoxic freshwater and estuarine water.

Key Words:

• Reduced sulphur compounds
• ambient concentrations
• gas exchange
• estuaries
• freshwater ecosystems
• vegetated soils
• Brazil