MEASUREMENTS OF REDUCED SULFUR-COMPOUNDS IN AN INDUSTRIALIZED TROPICAL REGION - CUBATAO (BRAZIL)

Ambient concentrations of SO2, H2S, COS and CS2 has been determined at various sites in the highly industrialized area of Cubatao (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 Piloes (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 Cubatao, a reservoir north of Cubatao, and vegetated soils at Vale do Mogi, Paranapiacaba, and Vale do Piloes. The content of reduced sulphur compounds was determined in surface water samples from lakes, rivers, and estuaries in the area under investigation. We sulphate deposition and ambient SO2 concentrations revealed a similar hierarchy of Vale do Mogi, Paranapiacaba, and Vale do Piloes 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.