Trace metals in streams can be toxic to fish and aquatic insects. Therefore, sampling streams for metals is an important aspect of water-quality monitoring. In the past, scientists assumed that a stream water sample collected at any time of the day would provide an accurate assessment of metal concentrations on that day assuming streamflow was relatively constant. Recent studies, however, have shown that dissolved concentrations of some trace metals exhibit substantial and consistent variation throughout the day.
An increasing body of evidence indicates that the concentration of many potentially toxic trace elements (such as arsenic, cadmium, copper, manganese, zinc) in streams can vary over a large range (up to 500 percent) during a 24-hour period irrespective of changes in streamflow. These diel concentration cycles have been shown to be robust and reproducible, having been documented in many streams separated by large distances, in different geologic environments, and over a large range of metal concentrations.
Trace metals in streams can be toxic to fish and aquatic insects. Therefore, sampling streams for metals is an important aspect of water-quality monitoring. In the past, scientists assumed that a stream water sample collected at any time of the day would provide an accurate assessment of metal concentrations on that day assuming streamflow was relatively constant. Recent studies, however, have shown that dissolved concentrations of some trace metals exhibit substantial and consistent variation throughout the day.
An increasing body of evidence indicates that the concentration of many potentially toxic trace elements (such as arsenic, cadmium, copper, manganese, zinc) in streams can vary over a large range (up to 500 percent) during a 24-hour period irrespective of changes in streamflow. These diel concentration cycles have been shown to be robust and reproducible, having been documented in many streams separated by large distances, in different geologic environments, and over a large range of metal concentrations.