Effects of CO2on Spray Solution pH

Abstract

The pH of deionized water, initially adjusted to a pH of 6 to 9, all decreased to near pH 5 upon pressurization with CO2in a backpack spray system. When deionized water contained bicarbonate (NaHCO3or KHCO3) at 0 to 800 mg/L to buffer against a pH decrease from CO2pressurization the return to their initial pH was more rapid than deionized water alone regardless of bicarbonate source. Acidification of spray solution following CO2pressurization of 138, 276, or 414 kPa was similar and bicarbonate had a greater effect than spray pressure. Addition of acidifying buffer and bicarbonate to the solution resulted in an initial and post-CO2pressurization pH range of less than one pH unit. All spray solution pH levels returned to near their initial pH following depressurization, indicating that the pH decrease was not permanent. Rate of recovery from acidification with CO2increased with initial pH and bicarbonate concentration.