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Activation of liquids with atmospheric pressure plasmas is being investigated for envi-ronmental and biomedical applications. When activating the liquid using gas plasma produced species (as opposed to plasmas sustained in the liquid), a rate limiting step is transport of these species into the liquid. To first order, the efficiency of activating the liquid is improved by in-creasing the ratio of the surface area of the water in contact with the plasma compared to its vol-ume – often called the surface-to-volume ratio (SVR). Maximizing the SVR then motivates the plasma treatment of thin films of liquids. In this paper, results are discussed from a computa-tional investigation using a global model of atmospheric pressure plasma treatment of thin water films by a dielectric barrier discharge (DBD) sustained in different gases (Ar, He, air, N2, O2). The densities of reactive species in the plasma activated water (PAW) are evaluated. The resi-dence time of the water in contact with the plasma is increased by recirculating the PAW in plasma reactor. Longer lived species such as H2O2aq and NO3−aq accumulate over time (aq de-notes an aqueous species). DBDs sustained in Ar and He are the most efficient at producing H2O2aq, DBDs sustained in argon produces the largest density of NO3−aq with the lowest pH, and discharges sustained in O2 and air produce the highest densities of O3aq. Comparisons to experi-ments by others show agreement in the trends in densities in PAW including O3aq, OHaq, H2O2aq and NO3−aq, and highlight the importance of controlling desolvation of species from the activated water.