Oxidants in Precipitation

Abstract

Large quantities of chlorine are produced in the United States each year. A by-product of industrial use and manufacture is that some chlorine gas escapes into the atmosphere. However, a general lack of information exists on precipitation washout of these oxidant residuals despite recognized emissions into the atmosphere. It is hypothesized that acid precipitation is only an indicator of other less obvious phenomena,and the pH of precipitation may well serve as an index of a variety of atmospheric pollutant problems.

Significant inputs of chlorine gas are emitted into the atmosphere in New York State; the major source of chlorine emissions occurs in Niagara County, New York. Oxidant residuals have been measured in rainfall from Central New York. Maximum residuals in rainfall coincided with depressed pH values and maximum rainwater temperature. The observed chlorine residuals and dominance of NH3 ions in rainfall suggest the residual may be a combined form of the type NHxCly. One hypothesis is that industrial emissions of this gas combine with NH3 in the atmosphere to form NHxCly compounds or chloramines which are later removed by atmospheric washout.

Laboratory and field studies reported in the literature suggest that oxidant residuals are toxic to biological organisms and the impact is highly dependent on concentration and duration of exposure. In dilute aquatic systems of low buffering capacity, measured oxidant residuals can potentially affect biological organisms and may pose a new element of concern.