Experimental acidification of Little Rock Lake, Wisconsin : The first four years of chemical and biological recovery

• Published in: Water, air and soil pollution air and soil pollution, 1995-01, Vol.85 (3), p.1713-1719
• Main Authors: SAMPSON, C. J, BREZONIK, P. L, FROST, T. M, WEBSTER, K. E, SIMONSON, T. D
• Format: Article
• Language: English
• Subjects: Applied sciences; Continental surface waters; Exact sciences and technology; Freshwater; Natural water pollution; Pollution; Water treatment and pollution
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/BF00477227

One basin of Little Rock lake was acidified during 1984-1990 with sulphuric acid, causing progressive decreases in pH from 6.1 to 4.7. The lake was then allowed to recover, so that by the fourth year about 50 per cent of the change necessary to return to pre-acidification values of pH, acid neutralizing capacity (ANC), sulphate and calcium had occurred. Increases in ANC during the first 2 years of recovery were closely predicted by models, but those in years 3-4 were slower than expected. This was possibly due to the 0-5 cm sediment layer acting as a sink for ANC generated by sulphate reduction. The biological recovery of the lake was not as swift or straightforward. Zooplankton species diminished by acidification had not returned while those favoured by acidity had diminished. The mayfly species Caenis had also failed to return. Further studies of the recovery responses were needed to produce more accurate models of recovery from acidification.