The chemical composition of rainfall at Menlo Park, on San Francisco Bay, is compared with rainfall at Petrolia, which is near the coast about 500 km north of San Francisco. Sequential samples representing 1.35 to 5.4 mm of rain were collected from November 1971 to January 1972. At rural Petrolia the Cl:Na ratio was that of seawater for Cl concentrations ranging from 0.02 to 38 mg/l. In metropolitan Menlo Park the Cl:Na ratio in rain closely approximated that in seawater above about 0.5 mg/l Cl, but at lower Cl concentrations the ratio exceeded that in seawater, a fact attributed to the presence of anthropogenic Cl. Other constituents dissolved in Menlo Park rain (along with their concentration ranges in milligrams per liter), and believed to be derived in part from anthropogenic sources, were Ca (0.01–1.07), Mg (<0.01–1.08), Pb (0.003–0.035), Zn (0.002–0.013), Mn (0.0001–0.0057), Cu (0.0008–0.0024), NO3‐N (0.02–0.54), and Br (<0.01–0.12). The range of pH values was smaller in the rural than in the metropolitan areas; average H+ activity corresponded to a pH of 5.1 to 5.2 in both areas. At Petrolia, pH decreased with increased dissolved salts in rainfall, but no relation between pH and dissolved salts was evident at Menlo Park.
Additional publication details
|Publication Subtype||Journal Article|
|Title||Variation of rain chemistry during storms at two sites in northern California|
|Series title||Water Resources Research|
|Publisher||American Geophysical Union|
|Contributing office(s)||California Water Science Center|