LAUSR

Abstract Chemical characterization of hurricane wet deposition is integral to understanding how future extreme weather events will impact coastal biogeochemical cycles. Sequential Hurricane Harvey wet deposition samples (n = 7 over 20.5 h) were collected in southeastern Texas, U.S. and the isotopic composition of nitrate and water (δ15N–NO3-, δ18O–NO3- and δ18O–H2O, δ2H–H2O) and the concentrations of ammonium, anions, and dissolved organic carbon were measured. Areas of peak deposition (~1500 mm) received up to 75% of the region's typical average annual inorganic nitrogen wet deposition. After δ15N–NO3- values were corrected for potential fractionation effects, contributions of lightning, natural gas combustion, vehicle exhaust and biogenic sources to NO3− in wet deposition (43.7 ± 31.2%, 7.8 ± 6.1%, 42.6 ± 27.5% and 5.9 ± 5.3%, respectively) were determined using a Bayesian isotope mixing model. Results highlight the significance of natural-sourced nitrogen being deposited to terrestrial systems during hurricane events. The relatively low δ18O–NO3- (36.1 ± 3.0‰) emphasized the role played by hydroxyl and peroxy radicals in HNO3 formation during the tropical summer. An established global NOx oxidation model in combination with δ18O–NO3- approximates the significance of RO2 vs O3 oxidation of NO during the daytime (36.0% vs 64.0%, respectively) and results provide valuable insight to low-latitude atmospheric chemistry.