Nitrogen dioxide (NO2) dry deposition into the environment can lead to eutrophication, soil acidification, algal blooms, and hypoxia. Across watersheds-marine and terrestrial-wet deposition of Nr is well documented while dry deposition is under characterized. To have an accurate representation of the total nitrogen budget and its relationship to critical load exceedance, it is essential to have an accurate representation of dry deposition specific to each watershed. Here we model NO2 dry deposition in terrestrial and marine watersheds (i.e., Galveston Bay, Corpus Christi Bay, Trinity River, and San Antonio River watersheds) using in situ federal equivalent networks by Texas Commission for Environmental Quality (TCEQ) and U.S. EPA, ground-level remote sensing from Pandonia Global Network, as well as data from TROPOMI. This allows us to compare the accuracy of both satellite-borne and ground-based remote sensing to a more robust network. Data from the Galveston watershed FEM data has shown that in the Galveston area 6.09x106 kg of N is deposited into the environment in the year 2023. This NO2 loading estimate is a missing component in previous models in the region and represents an 18% underestimate which highlights the need for a more well-rounded approach to air pollution mitigation. The comparison between the TROPOMI-with a higher spatial resolution-in contrast of the FEM network has shown that there could be biases in the outskirts of the watershed. In areas where there is a high density of FEM monitors, like is the case of Houston, there is good agreement (p=0.003) between the conversion of tropospheric column density and FEM ambient concentration. This is especially true with concentrations lower than 14 ppb (R =0.9995). Combining the spatiotemporal advantages of these networks combined gives a more complete understanding of deposition trends across Texas. However, increasing the accuracy of remote sensing-based deposition models would offer a lower cost and larger coverage network in the future.

¹ Department of Physical and Environmental Sciences, Texas A&M University-Corpus Christi , Corpus Christi, TX

² Center of Water Supply Studies, Texas A&M University-Corpus Christi, Corpus Christi, TX

* Corresponding Author: agarcialunar@islander.tamucc.edu