Describe how isotopic fingerprinting can be used for source attribution in environmental forensics and provide a basic example.

• A. Distinct isotopic ratios (e.g., nitrate 15N/14N, sulfate 34S/32S) link contamination to specific sources; example: distinguishing fertilizer-derived nitrate from septic system nitrate in groundwater.
• B. Isotopic fingerprinting uses concentration levels to identify sources.
• C. Isotopic fingerprints cannot distinguish sources due to identical isotopic ratios across sources.
• D. It is used only for dating samples, not source attribution.

Answer: (A)