A new method for monitoring temporal trends in the acidity of fresh waters

Abstract

Acid precipitation and the consequent increased acidity of fresh waters are subjects of widespread concern. Several organizations in the United States, Canada and Europe have established extensive monitoring programmes in an attempt to determine the relationship between the acidity of preciptation and the change in acidity of fresh waters. We contend here that the present strategies for monitoring temporal trends in the acidity of fresh waters will not yield results sensitive enough to detect trends in acidity even on a 10-year timescale. We propose here an alternative scheme based on calculations using precise measurements of dissolved inorganic carbon (DIC) and partial pressure of CO₂ ($P_{\text{C}{\text{O}}_{\text{2}}}$)· This scheme eliminates biases inherent in pH electrode determinations and minimizes the perturbations in acidity caused by changes in the $P_{\text{C}{\text{O}}_{\text{2}}}$ of lake waters associated with biological cycles.