Ultrafiltration was conducted using a 0.2 μm membrane during groundwater flow-through in the sampling intervals in the boreholes.
Table 2 shows the chemical compositions of the filtered groundwater in each sample interval volume from the 09MI20 and 10MI26 boreholes during purging of groundwater by allowing flow-through in the boreholes.
In contrast to the size-fractionated groundwater and colloid sampling, the groundwater was passed through a 0.2 μm membrane during groundwater flow-through in the sampling interval space in the boreholes.
The concentrations of REEs were approximately constant and within analytical error (±10%) during groundwater flow-through in the sampling intervals in the 09MI20 and 10MI26 boreholes (Figure 9). Figure 8 Size-fractionated concentrations of REEs from boreholes.
Despite the changes in the concentrations of Fe and TOC, the Al concentrations were approximately constant (6.1 ± 0.8 μg/L) during groundwater flow-through in the 09MI20 borehole (Figure 6d).
Although the concentrations of Fe, Al, and TOC for the filtered groundwater changed, the REE patterns in the groundwaters did not change during the groundwater flow-through in the boreholes and were significantly enriched in HREEs.
Although the concentrations of Fe and TOC changed during groundwater flow-through in the 09MI20 borehole, they were approximately constant (2.9 ± 0.4 μg/L and 1.3 ± 0.1 mg/L, respectively) during the flow-through of the groundwater in the 10MI26 borehole (Figure 6b,c).
After centrifuging at 7,500× g for 2 h, the flow-through in the concentrator was collected for further assay.
