Contribution of ultrafine particles to alkalinity in a limestone‐treated waterbody

While it is well recognized that suspended particles can bias titration‐based total alkalinity (TA), whether addition of minerals for alkalinity enhancement introduces systematic TA artifacts remains poorly quantified. To address this gap, we quantified the contribution of ultrafine particles (< 0.2 μ m) to TA titration introduced by limestone (0.1, 0.5, 1, and 2 g L −1 ) under two p CO 2 conditions (420 and 1495 ppm). We found that the TA increase is much higher than the theoretical increase determined by [Ca 2+ ] when added limestone is over 0.1 g L −1 . However, this excess TA is negligible when the added mineral particles exclude ultrafine particles. Also, the particulate TA decreases when there is more mineral dissolution under the high p CO 2 treatment. These findings suggest that even after 0.2 μ m filtration, traditional TA titration of mineral‐treated water may still overestimate true mineral dissolution, potentially leading to inflated carbon dioxide removal estimates.