Groundwater colloid properties in sedimentary rocks; Preliminary results from the Horonobe URL

Sasamoto, Hiroshi   ; Ohara, Shigeru*

In the present study, a non-destructive technique using Particle Tracking Analysis (PTA) has been tested to determine size distribution and concentration of colloids in groundwater. The groundwaters were sampled from water-rings (4 samples) located in the vertical shafts and boreholes (6 samples) drilled in the drifts of the Horonobe URL. Results suggest that colloid particle concentrations range from 9.110 to 7.810 particle/mL (pt/mL) and the estimated colloid mass concentrations range from 3.410 to 4.2 mg/L for the diameter of 1 to 1000 nm, respectively. Colloid concentrations of groundwater sampled from water-rings are generally higher than those sampled from boreholes due to differences in groundwater sampling conditions. For sizes 100 nm of particles, colloid stability was evaluated on the basis of DLVO theory. DLVO theory predicts that particle sizes 100 nm would be unstable (i.e., coagulation could occur). Particle and mass colloid concentrations in the groundwater were therefore reevaluated to obtain the reliable colloid particle concentrations range from 5.810 to 3.010 pt/mL and colloid mass concentrations range from 2.010 to 1.310 mg/L for the diameter range 100 nm, respectively. Furthermore, the reevaluated results indicate a negative correlation between colloid concentrations and IS of groundwater.