Emissions of marine biogenic sulfur to the atmosphere of northern Europe

Abstract

Measurements of DMS and other reduced sulfur compounds in surface waters have been carried out from a helicopter in the seas surrounding Scandinavia. Average summer time concentrations of DMS ranged from 70 to 150 ngS L-1. Simultaneous measurements of biological and physical parameters revealed no correlation between DMS and phytoplankton species, species assemblages, total phytoplankton biomass, chlorophyll a, temperature, and salinity. The only exception was a correlation between DMS concentration, Chrysochromulina spp. belonging to the Prymnesiophyceae, and salinity over a narrow range of salinity in the Baltic Sea. The flux of reduced sulfur to the atmosphere in July in this region is estimated to be 120–170 μgS m-2 d-1 from the Baltic, 240–810 in the Kattegat/Skagerrak, and 120–690 in the North Sea. Annual fluxes are roughly 100 times higher than these daily fluxes. On an annual basis, biogenic sulfur emissions from the coastal seas are negligible (<1%) compared to the anthropogenic emissions in northern Europe. However, during the summer months, the biogenic sulfur emissions from the seas surrounding the Scandinavian peninsula are estimated to be as high as 20–70% of the anthropogenic emissions in Scandinavia. This makes it of interest to incorporate the biogenic emissions in calculations of long-range transport and deposition of sulfur within the region. Other volatile sulfur species, mainly methyl mercaptan, contribute about 10% of the total flux of reduced sulfur. Estimated fluxes of CS2 to the atmosphere ranged from 1 μgS m-2 d-1 in the Baltic Sea to 6 μgS m-2 d-1 in the North Sea. No emissions for H2S or COS were detected.