Coastal rainwater hydrogen peroxide: Concentration and deposition

Correlation analysis between rainwater component concentrations (hydrogen peroxide, hydrogen ion, nitrate, nonseasalt sulfate and chloride ion) was used to investigate patterns of variation in hydrogen peroxide concentrations in rain collected in Wilmington, North Carolina, a coastal southeastern United States location, between October 1992, and October 1994. Rainwater hydrogen peroxide concentrations in general correlated positively with the pollutant components (hydrogen ion, nitrate and non-seasalt sulfate). This pattern suggests that destruction of hydrogen peroxide by sulfur dioxide is not the dominant factor controlling the concentration of hydrogen peroxide in this rainwater, with the possible exception of winter rain from coastal storms where an inverse correlation between hydrogen peroxide and nonseasalt sulfate was observed. Sequential sampling indicates rapid production of hydrogen peroxide and incorporation into rain within time periods of hours during summer daytime rains. Rain is an important transport mechanism for removal of atmospheric hydrogen peroxide, which may affect the oxidizing capacity of surface waters that receive the rain. During this study time, the annual deposition of hydrogen peroxide by rain was 12 mmole m(-2) yr(-1). An average rain event added approximately half of the resident amount of hydrogen peroxide to the shallow lakes typical of eastern North Carolina; extreme rain events can triple the amount normally present. The episodic nature of rain contributes to the variability in hydrogen peroxide concentration in surface waters. Higher hydrogen peroxide concentrations and greater rainfall amounts cause wet deposition of hydrogen peroxide to be approximately seven times greater during the warm season than the cold season.