An increase of nitrogen deposition resulting from human activities is not only a major threat for global biodiversity, but also for human health, especially in highly populated regions. It is thus important and in some instances legally mandated to monitor reactive nitrogen species in the atmosphere. However, deployment of automated networks can be excessively costly for most cities so the utilization of widely distributed biological species suitable for biomonitoring may be a good alternative. The aim of this work was thus to assess the suitability of different atmospheric organisms as biomonitors of nitrogen deposition by means of an extensive sampling of a lichen, two mosses, and one bromeliad throughout the Valley of Mexico, the basin where the megalopolis of Mexico City (population 20 million) is located, and subsequent measurements of nitrogen metabolism parameters
In all cases significant responses of nitrogen content, C:N ratio and δ15N were found for the lichen Anaptychia sp. the mosses Grimmia sp. and Fabronia sp., and the bromeliad Tillandsia recurvata in response to season and collected site. In turn, δ15N for the mosses responded linearly to the wet deposition (R2= 0.7 for Grimmia sp. and R2=0.2 for Fabronia sp.). Also, the nitrogen content (R2=0.7), the C:N ratio (R2=0.6), and δ15N (R2=0.5) for the bromeliad had a linear response to NOx. However, latter species was not found in sites with NOx concentrations above 212 ppm. These biomonitors can be utilized in tandem to determine the status of nitrogenous pollution in regions without monitoring networks.