Sulphur deposition from atmosphere increased

The amount of sulphur entering the oceans in river runoff has probably more than doubled due to human activities (compare the fluxes in Fig. 7.17a b). This has been caused in part by sulphur-rich wastewaters and agricultural fertilizers entering river and groundwaters and thence the sea, although another major factor is sulphur deposited directly into surface waters from the atmos-ph ere. The combined (atmospheric and runoff) effects of enhanced sulphur inputs to seawater cause an increase of sulphur (as SO)- in the oceans) of only about 10 5% per annum. This estimate is probably an upper limit, since it assumes that removal of seawater sulphur into ocean sediments (see Section 6.4.6) remains as previously and has not increased following the enhanced inputs from the atmosphere and rivers. 

The deposition flux of sulphur from the atmosphere on to the oceans and land surfaces has increased by approximately 2 5 and 163%, respectively. Although this input has essentially no impact on the chemistry of seawater, due to its buffer capacity and the large amount of sulphate (SO -) it contains (see... 

The OECD project showed that the acidification of precipitation was due to an increased content of sulphuric and nitric acid. The main cause was identified as the increased use of fossil fuels, including motor vehicle traffic. In the atmosphere, sulphur dioxide and nitrogen oxides from combustion processes are oxidized to sulphuric acid and nitric acid, which are taken up and deposited by the precipitation. 

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