Variation in pH during Summer Storms near the Continental Divide in Central Colorado, U.S.A.

Publisher Website
Google Scholar
Abstract
Precipitation acidity was monitored continuously from July-Sept. 1983 at a well-instrumented research site located near the Continental Divide in central Colorado. Rainfall amount, temperature, pH and specific conductance were determined using a prototype device consisting of a modified wet-only precipitation collector with appropriate sensors. Data were recorded automatically with microprocessor control by preset time intervals. Weekly wet-only composite precipitation samples were also collected. Precipitation totaled 190 mm during the period, all as rain. Of the continuous pH measurements 65% were between 3.40 and 4.10, with an average of pH 3.80. Values of pH greater than 5.00 were rare. Composite samples were significantly less acidic and averaged ph 4.36. Precipitation pH typically decreased rapidly as a storm began, was lowest near or slightly after the time of maximum rainfall intensity, then increased slightly. Paradoxical low pH and low specific conductance were recorded; it is possible that some initial continuous pH measurements were too low. Acid loading varied widely among storms, and may have resulted largely from short bursts of high-intensity, low-pH rainfall.