Characterization of nitrogen deposition in a megalopolis by means of atmospheric biomonitors

Abstract

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. The utilization of widely distributed biological species suitable for biomonitoring may be a good alternative. We assessed the suitability of an ensemble of atmospheric biomonitors of nitrogen deposition by means of an extensive sampling of a lichen, two mosses, and a bromeliad throughout the Valley of Mexico, whose population reaches 30 million, and subsequent measurements of nitrogen metabolism parameters. In all cases we found significant responses of nitrogen content, C:N ratio and the δ15N to season and site. In turn, the δ15N for the mosses responded linearly to the wet deposition. 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, the bromeliad was not found in sites with NOx concentrations exceeding 80 ppb, apparently of as a consequence of excess nitrogen. These biomonitors can be utilized in tandem to determine the status of atmospheric nitrogenous pollution in regions without monitoring networks for avoiding health problems for ecosystems and humans.

Ozone will remain a threat for plants independently of nitrogen load

“…However, O 3 effects barely varied with the level of N addition, and this variation mostly occurred when N addition was more than 60 kg N ha −1 year −1 (an unrealistic level in terms of N deposition in the next several decades) and/or O 3 concentrations were not in the rage of 20–40 ppb above control. These results suggest that urban or urban‐affected vegetation, and particularly in megalopolises, may be at higher risks for exacerbated O 3 ‐induced negative effects than non‐urban or urban‐affected vegetation due to higher on‐road ammonia emissions and dry deposition in urban areas (Bettez & Groffman, ; Díaz‐Álvarez & de la Barrera, ; Fenn et al, ). Meanwhile, annual average O 3 concentration seems to be increasing faster in urban than in rural areas; albeit peak values are decreasing in both rural and urban areas (Paoletti et al, ).…”

“…Conversely, since high N addition can negatively affect plants (Sun et al, ), we hypothesized that it may aggravate the negative effects of elevated O 3 . Potential dependence of O 3 effects on N addition is also important for predicting N deposition and O 3 effects because of the spatial variation of N deposition, such as between urban‐affected vegetation and non‐urban‐affected vegetation (Bettez & Groffman, ; Díaz‐Álvarez & de la Barrera, ; Fenn et al, ). We also sought to understand whether the effects of concurrent N addition and O 3 may differ between functional groups of species.…”

Effects of drying methods on plant lipid compounds and bulk isotopic compositions

“…For the n-alkanoic acids, angiosperms generally produced higher concentrations (as high as 200 μg/g) than the gymnosperms (as high as 70 μg/g; Figure 1; Table 2). The n-C 20 , n-C 22 , n-C 24 and n-C 26 alkanoic acids were produced by both taxa, but n-C 28 n-Alkanols were found in all species, ranging widely from 4.9 μg/g (n-C 32 in P. sylvestris) to 1,036.4 μg/g (n-C 28 in T. distichum) ( Figure 1; Table 2). We found lower n-C 22 alkanol concentrations in freeze-dried (12.2 ± 2.0 μg/g) than in air-dried samples (27.1 ± 8.1 μg/g) in T. distichum (ANOVA, p = 0.0076).…”

“…The carbon isotopic compositions (δ 13 C) of leaves have also been used extensively to provide information on plant photosynthetic pathways (C 3 and C 4 plants) and water availability of plants during growth, 19–21 whereas the nitrogen isotopic compositions (δ 15 N) in plants reflect climate, nitrogen source, and availability 22–26 . The combination of the two values in plants can also be used to trace sources and fates of environmental pollution such as CO 2 and NO x emissions 27,28 . These measurements are beneficial for elucidating ecological conditions especially where direct measurements can be challenging.…”

“…[22][23][24][25][26] The combination of the two values in plants can also be used to trace sources and fates of environmental pollution such as CO 2 and NO x emissions. 27,28 These measurements are beneficial for elucidating ecological conditions especially where direct measurements can be challenging.…”