Detection of morphological and eco-physiological traits of ornamental woody species to assess their potential Net O 3 uptake.

Urban greening can improve cities' air quality by filtering the main gaseous pollutants such as tropospheric ozone (O ₃ ). However, the pollutant removal capacity offered by woody species strongly depends on eco-physiological and morphological traits. Woody species with higher stomatal conductance (g _s ) can remove more gases from the atmosphere, but other species can worsen air quality due to high O ₃ forming potential (OFP), based on their emitting rates of biogenic volatile organic compounds (bVOCs) and Leaf Mass per Area (LMA). Presently, there is a lack of data on eco-physiological (g _s , bVOCs emissions) and foliar traits (LMA) for several ornamental species used in urban greening programs, which does not allow assessment of their O ₃ removal capacity and OFP. This study aimed to (i) parameterize g _s , assess bVOCs emissions and LMA of 14 ornamental woody species commonly used in Mediterranean urban greening, and (ii) model their Net O ₃ uptake. The g _s Jarvis model was parameterized considering various environmental conditions alongside isoprene and monoterpene foliar bVOCs emission rates trapped in the field and quantified by gas chromatography-mass spectrometry. The results are helpful for urban planning and landscaping; suggesting that Catalpa bignonioides and Gleditsia triacanthos have excellent O ₃ removal capacity due to their high maximum g _s (g _max ) equal to 0.657 and 0.597 mol H ₂ O m ^-2 s ^-1 . Regarding bVOCs, high isoprene (16.75 μg g _dw ^-1 h ^-1 ) and monoterpene (13.12 μg g _dw ^-1 h ^-1 ) emission rates were found for Rhamnus alaternus and Cornus mas. In contrast, no bVOCs emissions were detected for Camellia sasanqua and Paulownia tomentosa. In conclusion, 11 species showed a positive Net O ₃ uptake, while the use of large numbers of R. alaternus, C. mas, and Chamaerops humilis for urban afforestation planning are not recommended due to their potential to induce a deterioration of outdoor air quality.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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