Abstract
The distribution of yearly averages of the concentration of various inorganic ions in rain water over the United States is discussed. The major source of Cl−is the ocean. The Cl−/Na+ ratio, however, is considerably less than that in sea water. It is very likely that this is caused by excess Na+ from the soil. A similar distribution of excess material from the soil is observed with K+. In contrast to Na&plus: and K+, which are rather uniformly distributed over the United States, Ca+ shows highest values over the Southwest, in agreement with the occurrence of dust storms.
Most of the SO4— over the ocean originates from sea spray. The source of additional SO4— is the land. Budget considerations indicate that about 30 per cent of this additional SO4— on a global scale is due to human activities.
On the basis of the data presented, the average global residence time of SO2 is estimated to be 40 days. This value is compared with available data on residence times of other constituents which are also primarily controlled by washout.
