Mapping rain composition in the east of Spain by applying kriging

This paper presents the results of applying kriging to the major inorganic ions from a bulk deposition network on the eastern coast of Spain that has been in operation for more than two years (October 1989 to December 1992). From the calculated variograms spatial correlation up to 70-130 km has been found, depending on the ion. The most suitable models of variograms have been found for sulphates and marine ions (chloride, sodium). Nitrates and pH correlates only at smaller distances. For calcium and pH additional to the correlation at smaller distances, a correlation at distances around 140 km was found. The nugget effect was high for most variograms, suggesting the importance of local influences in rain chemistry in the area. In general, most of the ions follow a spatial pattern that gives the highest values in the south and the lowest in the north inland part of the area of study. It is possible to discern different spatial patterns according to the ions and their main sources: A pattern following the coastline with decreasing values from the coast to inland was followed by chloride, sodium, magnesium and nitrate ions; a pattern divided into four areas, two with pH < 6.2 and less than 220 mu eq L(-1) for calcium and another two zones that surpass these values. Finally total sulphate and non-marine sulphate follow a pattern half-way between the previous patterns.