Sulfur isotope composition of soils and fertilizers: Differences between Northern and Southern Hemispheres

The sulfur isotope composition (delta(34)S) of available sulfate was measured for 44 soils developed on volcanic ashes and basaltic terrains in Japan, Hawaii, Australia, New Zealand, Brazil and Chile. Native soil sulfates are a mixture of seaspray (delta(34)S = + 20 parts per thousand) and anthropogenic (around + 5 parts per thousand on average) sulfates. The isotopic values are generally higher in areas of the Southern Hemisphere than in the Northern Hemisphere. Such a hemispheric difference is due to differences in the relative contribution of sulfur from marine aerosols and human activity. Native Japanese soil samples collected at the sites more than 16 km inland from the coastal line tend to show lower delta(34)S values (+ 1.7 to + 8.9 parts per thousand), compared to those from the coastal regions (+ 10.9 to + 17.5 parts per thousand). Dominance of anthropogenic sulfur in the Japanese islands apparently existed as early as the early 1950's. Application of chemical fertilizers rich in sulfur has modified the sulfur isotope composition of native soils. Ammonium sulfate and single superphosphate from the current market in Japan have relatively low delta(34)S values (- 4.9 to + 10.2 parts per thousand), which reflect sulfur sources from crude oils and ore sulfides. In contrast, sulfur in fertilizers commonly used in New Zealand and elemental sulfur in sulfur-fortified single superphosphate from Australia gave higher delta(34)S values (+ 15.7 to + 20.7 parts per thousand). Extensive application of sulfur in the form of fertilizers, as in Japan and New Zealand, affects the sulfur isotope composition of arable soils.