THE POTENTIAL EFFECTS OF FIREWORKS ON WOODLAWN LAKE, SAN ANTONIO, TEXAS

Recent work has demonstrated that fireworks displays can leave trace chemicals in the environment, affecting air, precipitation, and surface water quality. The focus of this project is to examine potential effects from an annual 4^th of July fireworks display on the water chemistry of Woodlawn Lake, a manmade urban lake located in a residential area on the Westside of San Antonio, Texas. Three locations were selected based on historical water quality information and weather records, and sampled both immediately before and after the July 4, 2013 fireworks display. Major and minor element chemistry was determined through a combination of field and laboratory techniques using pH/conductivity meters, colorimetry, direct titration, and Flame Atomic Absorption Spectroscopy (Flame AAS).

Pyrotechnics involve many elements including coloring agents and fuels such as Na, Ca, Cu, Fe, Sr, Ba, Ti, and Al. In addition fireworks are typically launched using black powder (KNO₃, charcoal, and S) as a propellant. Because of the natural chemical composition of Woodlawn Lake (Na-Ca-HCO₃-SO₄), unambiguous concentration changes from pre- to post-display were not observed for major elements/compounds. Changes in concentration were observed for the minor constituents NO₃ and NO₂, however, with a peak observed closest to and downwind from the fireworks barge immediately following the display, and declining to pre-display levels within two weeks. No similar increase was noted in samples collected upwind from the fireworks launch site. The observed increase in NO₃ concentration is consistent with a signature from black powder, but potassium did not show a similar increase-then-decrease. Possible complicating effects include fertilizer/animal waste input, and evaporation/dilution associated with near-term precipitation.

Future work will include analyzing additional trace elements that are more likely to leave a distinctive fireworks signature such as Sr, Ti, Al, and Ba. Re-analysis of selected samples using Flame AAS will also help better understand potential uncertainties between different analytical methods (titration, colorimetry). In addition, a more detailed examination of historical water quality records and analysis of soils may help identify similar longer-term trends.