Title: How Expansion and Contraction of Colloid-Surface Interactions Drives Rise and Fall of Repulsive Barriers and Stochastic Colloid Attachment

The magnitude of repulsive barriers is of primary importance in colloid transport and surface interaction.  Experimentally observed colloid retention typically decreases and increases with rises and falls of repulsive barriers in response to decreases and increases in solution ionic strength, respectively. However, despite the observation that colloid attachment increases as barriers decrease, the mean field barriers remain hundreds to thousands of times too large to explain attachment.  Incorporation of nanoscale charge heterogeneity amplifies the rise and fall of repulsive barriers via expansion and contraction of the zone of colloid-surface interaction around heterodomains in response to decreased and increased ionic strength, respectively. This amplified impact of nanoscale heterogeneity explains experimentally observed attachment and introduces a stochastic nature to attachment that underlies explanation of non-exponential decreases of colloid concentrations with distance from source.  This success in prediction highlights the need for further efforts to directly characterize nanoscale heterogeneity.