Tillandsia strictaSol (Bromeliaceae) leaves as monitors of airborne particulate matter-A comparative SEM methods evaluation: Unveiling an accurate and odd HP-SEM method

Abstract

Airborne particulate matter (PM) has been included among the most important air pollutants by governmental environment agencies and academy researchers. The use of terrestrial plants for monitoring PM has been widely accepted, particularly when it is coupled with SEM/EDS. Herein, Tillandsia stricta leaves were used as monitors of PM, focusing on a comparative evaluation of Environmental SEM (ESEM) and High-Pressure SEM (HPSEM). In addition, specimens air-dried at formaldehyde atmosphere (AD/FA) were introduced as an SEM procedure. Hydrated specimen observation by ESEM was the best way to get information from T. stricta leaves. If any artifacts were introduced by AD/FA, they were indiscernible from those caused by CPD. Leaf anatomy was always well preserved. PM density was determined on adaxial and abaxial leaf epidermis for each of the SEM proceedings. When compared with ESEM, particle extraction varied from 0 to 20% in air-dried leaves while 23-78% of particles deposited on leaves surfaces were extracted by CPD procedures. ESEM was obviously the best choice over other methods but morphological artifacts increased in function of operation time while HPSEM operation time was without limit. AD/FA avoided the shrinkage observed in the air-dried leaves and particle extraction was low when compared with CPD. Structural and particle density results suggest AD/FA as an important methodological approach to air pollution biomonitoring that can be widely used in all electron microscopy labs. Otherwise, previous PM assessments using terrestrial plants as biomonitors and performed by conventional SEM could have underestimated airborne particulate matter concentration.

Surface-Based Analysis of Leaf Microstructures for Adsorbing and Retaining Capability of Airborne Particulate Matter in Ten Woody Species

“…Particulate matter (PM) is an air pollutant in urban and industrial areas and PM fractions with a diameter of 10 µm or less often exceed air quality standards and cause serious concerns on ecosystems and humans including a wide range of respiratory and vascular diseases [1][2][3][4]. Recently, PM abatement technologies have become a global issue, and technological developments for purifying and improving air quality are rapidly expanding in Asia, North America, and Europe [5][6][7][8].…”

“…PM deposition onto leaf surfaces can markedly induce the possibility of stomatal blocking and photosynthetic inhibition [26,27]. Nevertheless, most recent previous results deal with coupling the presence of complex leaf shape, large surface area, or trichomes (projecting structures on the epidermal surfaces) that can improve particle adsorption capacity [2,11]. Therefore, a detailed understanding of the causal relationships between the unique microstructures and the PM adsorption feedback on different leaf surfaces is important for improving air quality.…”