Acidified lakes and streams without, or with impoverished fish populations, occur mainly in areas that receive high levels of acid deposition from the atmosphere and have soils derived from granite or other rocks of similar composition that are resistant to weathering and low in exchangeable elements such as calcium and magnesium. Catchments with thin soils are particularly sensitive with respect to the rate and extent of acidification.

Examination of the remains of diatoms and other biological material in lake sediments laid down over centuries has established that many lakes in southern Norway and Sweden and in the U.K. have undergone progressive acidification from ca. 1850 until very recently. The magnitude of this acidification is appreciably greater than any that has occurred in the past 10000 years and has marched in parallel with accelerated industrial development, as indicated by increases in several trace pollutants in the sediments. These changes and the extent of inferred acidification are geographically correlated with the intensity of acid deposition and with the geo-chemical status of the catchment.

For a given input of acid deposition, the degree of acidification of lakes and streams is largely determined by the structure and chemistry of the mineral and organic soils, and the pathways that the incoming rainwater takes through the soil.[…]