Sulphur inputs from rainfall throughout New Zealand

Abstract

The amount of sulphur (S) deposited in rainfall at four sites in the Waikato/King Country, New Zealand between 1983 and 1989 showed little annual variability. In general, the S concentration in rainfall was inversely related to the amount of rainfall. Data from these four sites, and published and unpublished data from 30 other sites throughout New Zealand, were used to evaluate the source of S in rainfall and to determine the main factors influencing the amount of S deposited in rainfall using multiple correlation analysis. Analysis of ratios of S to chloride indicated that sea-salt contributed c. 80% of S in rainfall near the coast and it declined to c. 10% inland. Of several site parameters examined, the best simple predictor of S in rainfall was the distance from the nearest coast: loge (kg S/ha per year) = 2.14–0.018 × (km from coast).

The accuracy of prediction was significantly improved by inclusion of a quadratic function of the annual rainfall. This accounted for an increase in S inputs with increasing rainfall which occurred only in the drier east coast regions. The most accurate model involved separate equations for sites nearest the west or east coasts and utilised distance from the coast and the amount of annual rainfall. Measurements of S in rainfall varied between 0.5 and 15 kg S/ha per year, being highest near the coast. Thus, in coastal areas, where soils and climate do not generate large leaching losses, inputs of S in rainfall may almost meet the annual S requirements of grazed pasture.

Keywords:

• sulphur
• rainfall
• atmospheric deposition
• marine influence
• sulphur model