Different interpretations of the importance of internal alkalinity generation in the alkalinity budgets of lakes and watersheds: A response to Schaffer, P. W., Hooger, R. P., Eshleman, K. N., and Church, M. R.:Water, air and soil pollut, 1988,39, 263
✍ Scribed by D. W. Schindler
- Publisher
- Springer Netherlands
- Year
- 1989
- Tongue
- English
- Weight
- 178 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0049-6979
No coin nor oath required. For personal study only.
✦ Synopsis
Schaffer et al. (1988)
perform an interesting analysis of the alkalinity budgets of several lakes and watersheds. However, their discussion of differences in interpretation to mine (pp 269-270) takes some quotes from my 1986 paper (Schindler, 1986) out of context, making the disagreements seem larger than they actually are. Also, their calculations do not account for the facts that non-steady state conditions may exist in lakes and watersheds, that watersheds and lakes may differ in their temporal response to increases or decreases in the acidity of deposition, and that dry inputs of elements other than sulfur contribute to alkalinity budgets of lakes and watersheds.
On p. 269, Schaffer et al. (1988) criticize me for disregarding the possibility that excess yields of S from watersheds may be due to dry deposition. This is not so; on p. 934 of my paper, I devote a full paragraph to the topic, including three references that have shown the phenomenon in the Sudbury area. However, in view of the threefold decrease in deposition in the Sudbury area following reductions in emissions by the International Nickel Co. since the early 1970's, I believe that the excess could be as well explained by delays in watershed response to reduced sulfur depositions as to dry deposition. In fact, the two processes cannot be distinguished, a common problem when one must rely on observations of ecosystems with uncontrolled pollutant inputs.
On p. 270, Schaffer et al. (1988) discuss the differences between production and yield, as I have done in earlier papers (Schindler, 1986, p. 934 and Schindler et al., 1986, Table I). Their quotation from my paper that internal alkalinity generation is 'in all cases.., too important to be ignored in budget calculations' is correct, except that it was taken from a paragraph discussing the importance of alkalinity sources f o r lakes (p. 939), and not of relative contributions o f lakes and watersheds to total basin alkalinity production, as their discussion implies. The former is terrestrial yield +IAG, while the latter is WAG + IAG. Once this is understood, it is clear that my quotation would apply to the 'pct lake alk from' columns of their Table III, and not to the 'pct basin alk production by' columns. The lowest