A sample made up smaller of portions, collected from various locations.is a mixture of spot samples taken at different times, or places, from a larger mass of the same material. It is produced by thoroughly mixing the combined spot samples and, if necessary, sub-diving the quantity of the resulting mixture, using approved techniques.
A series of water samples taken over a given period of time and weighted by flow rate. 
A sample which is made by combining samples from two or more locations. The sample can be of water, soil or another medium.