ABSTRACT
This chapter focuses on inorganic colloids and particles, but will also refer to data on biocolloid transport. It highlights the sampling and analytical considerations that need to be addressed in studies of groundwater colloids. Colloids in groundwater can arise from a number of sources and be removed or stabilized by a number of hydrogeochemical mechanisms. Colloidal particles can be dispersed and become mobile in aquifers as a result of changes in the groundwater chemistry such as a decrease in ionic strength or changes in ionic composition from calcium- to sodium-dominated chemistry. Groundwater samples are most often recovered by pumping, but the recovery of colloids is affected by the type of pump and by the rate of pumping. Sample tubing has intimate contact with the groundwater, and the slow pumping rates recommended for colloid sampling can increase this contact time even further. The on-line approach involves analyses of the sample before it exits the groundwater sampling tube.
