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River capture events may create short‐term pulses of incision in orogenic settings, complicating the interpretation of tectonic and climatic influences on exhumation patterns. The Sutlej River in northwestern India offers a compelling case study, as recent exhumation has been linked primarily to tectonic and climatic factors, whereas the capture of the Zhada Basin has been identified at <1 Ma. This region also features active faults and a river anticline formed by rapid river incision. The integration of new (U‐Th)/He data, inverse modeling and a geomorphic analysis has revealed two recent episodes of rapid exhumation along the river anticline: (a) a 0.8–0.3 Ma pulse coinciding with the capture of the Zhada Basin, which is associated with a 2‐ to 3‐fold increase in exhumation rates in the river anticline region, and (b) a 2–1 Ma pulse linked to the potential capture of the Pare Chu River, another major tributary of the Sutlej River. Our findings suggest that these Pleistocene river capture events both led to increased exhumation downstream along the river anticline, a region susceptible to rapid exhumation via ongoing deformation and a warm weak crust. Thus, this study emphasizes how erosional perturbations, triggered by changes in drainage systems, can significantly impact topography, local exhumation patterns, and deformation dynamics during <1 Myr time periods. 

Abstract Mercury (Hg) is a global pollutant whose atmospheric deposition is a major input to the terrestrial and oceanic ecosystems. Gas‐particle partitioning (GPP) of gaseous oxidized mercury (GOM) redistributes speciated Hg between gas and particulate phase and can subsequently alter Hg deposition flux. Most 3‐dimensional chemical transport models either neglected the Hg GPP process or parameterized it with measurement data limited in time and space. In this study, CMAQ‐newHg‐Br (Ye et al., 2018,https://doi.org/10.1002/2017ms001161) was updated to CMAQ‐newHg‐Br v2 by implementing a new GPP scheme and the most up‐to‐date Hg redox chemistry and was run for the northeastern United States over January‐November 2010. CMAQ‐newHg‐Br v2 reproduced the measured spatiotemporal distributions of gaseous elemental mercury (GEM) and particulate bound mercury (PBM) concentrations and Hg wet deposition flux within reasonable ranges and simulated dry deposition flux in agreement with previous studies. The GPP scheme improved the simulation of PBM via increasing winter‐, spring‐ and fall‐time PBM concentrations by threefold. It also improved simulated Hg wet deposition flux with an increase of 2.1 ± 0.7 μgm²in the 11‐month accumulated amount, offsetting half of the decreasing effect of the updated chemistry (−4.2 ± 1.8 μgm²). Further, the GPP scheme captured the observedK_p‐T relationship as reported in previous studies without using measurement data and showed advantages at night and in rural/remote areas where existing empirical parameterizations failed. Our study demonstrated CMAQ‐newHg‐Br v2 a promising assessment tool to quantify impacts of climate change and emission reduction policy on Hg cycling. 

Abstract Hyporheic zones are commonly regarded as resilient and enduring interfaces between groundwater and surface water in river corridors. In particular, bedform‐induced advective pumping hyporheic exchange (bedform‐induced exchange) is often perceived as a relatively persistent mechanism in natural river systems driving water, solutes, and energy exchanges between the channel and its surrounding streambed sediments. Numerous studies have been based on this presumption. To evaluate the persistence of hyporheic zones under varying hydrologic conditions, we use a multi‐physics framework to model advective pumping bedform‐induced hyporheic exchange in response to a series of seasonal‐ and event‐scale groundwater table fluctuation scenarios, which lead to episodic river‐aquifer disconnections and reconnections. Our results suggest that hyporheic exchange is not as ubiquitous as generally assumed. Instead, the bedform‐induced hyporheic exchange is restricted to a narrow range of conditions characterized by minor river‐groundwater head differences, is intermittent, and can be easily obliterated by minor losing groundwater conditions. These findings shed light on the fragility of bedform‐induced hyporheic exchange and have important implications for biogeochemical transformations along river corridors.