Of Fireworks and Tourism: GC×GC-HRMS Analysis of Summer Impacts on Lake Michigan Water Quality

Significance of the Topic

Fireworks events and peak tourism on Lake Michigan beaches can introduce a complex mixture of chemicals into the water. Evaluating these short-term impacts is important for environmental monitoring, public health protection, and informing regulatory strategies for popular recreational areas.

Study Objectives and Overview

The primary goal was to compare the chemical composition of water samples collected before and after July 4th fireworks at two Lake Michigan sites. Researchers aimed to identify residues from pyrotechnic materials and assess increases in personal care and recreational product markers associated with elevated beach attendance.

Methodology and Used Instrumentation

Water samples (60 mL) were collected at Silver Beach and Tiscornia Beach on July 2nd and within one hour after fireworks on July 4th. Samples were acidified to pH 2 and stored frozen until analysis. Extraction employed SPME Arrow fibers (1.5 mm DVB/Carbon WR/PDMS) with increased phase volume:

• Conditioning: 270 °C for 1 min
• Extraction: 30 min at 30 °C, stirring at 1200 rpm
• Desorption: 2 min in splitless mode at 250 °C

Comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC×GC-HRTOFMS) was performed using:

• Primary column: Rxi-5ms (30 m × 0.25 mm × 0.25 µm)
• Secondary column: Rxi-17SilMS (1.50 m total; 1.00 m in second oven, 0.31 m in transfer line)
• Oven program: 2 min at 40 °C, ramp 10 °C/min to 300 °C (hold 5 min); secondary oven +5 °C, modulator +15 °C; modulation period 5 s
• Carrier gas: He at 1.4 mL/min constant flow
• Mass spectrometer: LECO Pegasus HRT+ (EFP source at 250 °C), mass range 40–520 m/z, acquisition 200 spectra/s

Main Results and Discussion

Non-target screening revealed no direct pyrotechnic by-products at detectable levels. However, post-fireworks samples showed significant increases in compounds associated with sunscreen, insect repellent, and personal care formulations. Key observations included:

• Homosalate (sunscreen) increased ~40× and octocrylene ~15×; oxybenzone and 2-ethylhexyl salicylate emerged post-event
• DEET (insect repellent) increased ~5×
• Diisopropyl adipate (skin softener) rose 10×; various fragrance esters and lactones appeared or increased

GC×GC separation resolved coeluting species—such as acetophenone, heptanoic acid, and 1-methyl-4-propylbenzene—enabling cleaner mass spectra. High-resolution MS delivered mass accuracies below 2 ppm, supporting confident identification of sulfur- and nitrogen-containing compounds like benzothiazole and oxygenated phenols such as 2,4-di-tert-butylphenol.

Practical Benefits and Applications

This combined SPME Arrow and GC×GC-HRTOFMS approach offers a robust non-target screening tool for monitoring transient pollution events in recreational waters. It can inform beach management policies, guide public advisories, and facilitate rapid assessment of anthropogenic chemical loads associated with tourism and special events.

Future Trends and Opportunities

Advances may include miniaturized field-deployable SPME devices, automated data processing workflows for rapid non-target identification, and integration with environmental risk assessment models. Expanding this methodology to other event-driven scenarios and diverse water bodies could enhance global water quality monitoring frameworks.

Conclusion

Although fireworks residues were not directly detected, elevated levels of personal care chemicals closely linked to increased beach activity were clearly identified. The study demonstrates the power of SPME Arrow combined with GC×GC-HRTOFMS for high-sensitivity, high-selectivity environmental screening of complex water matrices.