residence time
1. (removal time) The time that a given substance remains in a particular compartment of a biogeochemical cycle.

2. The time during which water remains within an aquifer, lake, river, or other water body before continuing around the hydrological cycle. The time involved may vary from days for shallow gravel aquifers to millions of years for deep aquifers with very low values for hydraulic conductivity. Residence times of water in rivers are a few days, while in large lakes residence time ranges up to several decades. Residence times of continental ice sheets is hundreds of thousands of years, of small glaciers a few decades.

3. The average time a particular element of sea water spends in solution between the time it first enters and the time it is removed from the ocean.

4. The average time that a water molecule or particulate pollutant spends in the atmosphere. For pollutants (e.g. dust from a volcanic eruption), the residence time may range from a few weeks in the lower troposphere to several years in the upper stratosphere, before it is scavenged out by precipitation. For water molecules the overall average is believed to be 9–10 days.

residence time
1. (removal time) The time that a given substance remains in a particular compartment of a biogeochemical cycle.

2. The length of time water remains within an aquifer, lake, river, or other water body before continuing around the hydrological cycle. The time involved may vary from days for shallow gravel aquifers to millions of years for deep aquifers with very low values for hydraulic conductivity. Residence times of water in rivers are a few days, while in large lakes residence time ranges up to several decades. Residence times of continental ice sheets are hundreds of thousands of years, of small glaciers a few decades.

3. The average time a particular substance spends in solution in sea water between the time it first enters and the time it is removed from the ocean.

4. The average time that water remains in soil or rock.

5. The average time that a water molecule or particulate pollutant spends in the atmosphere. The residence time for pollutants ranges from a few weeks in the lower troposphere to several years in the upper stratosphere, before it is scavenged out by precipitation. For water molecules the overall average is believed to be 9–10 days.

Residence time

Residence time is the length of time that a substance, usually a hazardous material , can be detected in a given environment . For example, airborne pollutants are carried into the atmosphere by natural updrafts. The concentration and size of the particulates and their residence time exerts varying degrees of influence on the solar radiation balance. Other examples include the period of time that oxidant concentrations such as PAN-type or ozone remain in the atmosphere, or the period of time that nuclear by-products are found in the atmosphere or in the soil .

See also Hazardous waste siting; Radioactive waste

residence time (removal time) The time that a given substance remains in a particular compartment of a biogeochemical cycle. In particular, residence time is used to denote the time taken for pollutants to be removed from the atmosphere by natural processes.