“Having been in my progress so often misled by taking for granted the results of others, I have determined to write as little as possible but what I can attest by my own experience.” – John Dalton, Independent Scientist (1766-1844)
UPDATE (May 2, 2009): In the past 24 hours it has rained 0.93″ here in Big Sur with a pH of 4.56. I have amended the seasonal data accordingly.
UPDATE 2 (May 5, 2009): An additional 0.08″ was recorded, but the sample was too small to obtain an accurate pH reading. The seasonal data have been amended.
Anyone who thinks acid rain does not occur in pristine, unpolluted environments had better think again. Or better yet, go get some litmus paper and check it out for yourself.
Scientists studying Sudden Oak Death have dismissed acid rain as a relevant factor in oak mortality, pointing out that areas of severe decline are near the coast, upwind of the major sources of pollution, thus rainfall could not be acidic. Here along the coast of California storms blow in from the ocean where there are few sources of manmade pollutants. Rainfall pH, then, is not expected to be any more acidic than about 5.6, which is the theoretical pH of unpolluted rainwater in equilibrium with atmospheric CO2.
Acid precipitation in southeast Alaska (photo by Lee Klinger)
However, I have learned from past research that rainfall in pristine environments can sometimes be quite acidic[1]. So for the past three years I have been recording rainfall at my home in Big Sur using a Stratus RG202 rain gauge. Readings of rainfall pH have been made with a high-precision Beckman (Model Φ250) pH meter using a standard two-point (4.00 & 7.00) calibration. The rain station is located 1.2 miles from the coast at 36° 16’N; 121° 49’W, and 922’ (281 m) elevation.
Here are the results: Read the rest of this entry »
Sudden Oak Life 
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