In hydrogeology, a tracer is any substance contained in water or a water property that can be measured and used to infer environmental processes. An artificial tracer is deliberately released or injected for this purpose. In contrast, an environmental tracer is either naturally present in groundwater or produced as a result of human activity, but not specifically released for tracing purposes. Many of the commonly used environmental tracers are not natural, but have been produced by human activity and either deliberately or accidentally released into the environment.
- Environmental tracer
- artificial tracer