Rapid Measurement of Airborne Particles and Metals Using Plant Leaves

Greg Howard
11th July, 2024

Rapid Measurement of Airborne Particles and Metals Using Plant Leaves

This study found that while both Siamese cassia (Senna siamea) (left) and blackboard tree (Alstonia scholaris) (right) capture airborne pollutants, S. siamea is a more effective bio-filter due to its superior leaf micro-morphological properties for trapping particulate matter.

Composite: Natural Science News / CC BY. [Sources]
Adapted from photos by:

Key Findings

  • The study was conducted in Bilaspur, India, focusing on the plants Senna siamea and Alstonia scholaris to assess their ability to capture airborne toxic metals and particulate matter (PM)
  • Both plants were found to capture PM of various sizes, but S. siamea showed a higher capacity for PM retention due to its superior leaf micro-morphological properties
  • Harmful airborne toxic metals like lead, cadmium, and copper were found on the leaf surfaces, indicating these metals can enter leaves through stomatal openings
  • The study recommends using these plants as bio-filters to reduce PM pollution in urban areas
Particulate matter (PM) pollution is a significant environmental concern, especially in urban areas where traffic and industrial activities contribute heavily to air quality degradation. A recent study conducted by Guru Ghasidas Vishwavidyalaya aimed to assess the accumulation of airborne toxic metals on plant leaves in an urban environment[1]. This study focused on two commonly growing plants, Senna siamea and Alstonia scholaris, in Bilaspur, India, to understand their role in capturing PM and toxic metals from the air. The researchers collected leaf samples from both plants at busy traffic squares and a reference site with lower pollution levels. Using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), they analyzed the accumulation of PM and toxic metals on the leaf surfaces. The study found that both plants could capture PM in various size ranges, from respirable suspended particulate matter (RSPM) to ultra-fine particles (UFPs) smaller than 100 nm. However, S. siamea demonstrated a higher capacity for PM retention due to its superior micro-morphological properties. The presence of harmful airborne toxic metals such as lead (Pb), cadmium (Cd), copper (Cu), zirconium (Zr), aluminum (Al), and cobalt (Co) was confirmed in the PM collected from the leaf surfaces. This indicates that these toxic metals can enter the leaves through stomatal openings, a finding that aligns with previous studies on foliar uptake mechanisms[2]. The study recommended using both plants as bio-filters to minimize PM pollution in urban areas. This study builds on earlier research that highlighted the role of trees as bio-filters of urban air pollution[3]. Previous findings suggested that the shape and surface characteristics of leaves play a crucial role in PM capture. For instance, conifers with acicular needle shapes were found to be more efficient in PM2.5 accumulation compared to broadleaved species[3]. The current study extends this understanding by demonstrating that even among broadleaved species, micro-morphological properties such as trichomes and grooves significantly influence PM retention. The study also corroborates findings from other research on the foliar transfer of toxic heavy metals[4]. In particular, the enrichment factor (EF) values for Pb and Cd indicated significant anthropogenic contributions to regional pollution. The SEM studies confirmed that leaf morphology, including epidermis, trichomes, and stomata, helps accumulate toxic metals from deposited particulate matter. This aligns with the current study's findings that S. siamea leaves, with better micro-morphological properties, retained higher levels of PM and associated toxic metals. Furthermore, the study's use of SEM-EDS to identify toxic metals in PM highlights the importance of advanced analytical techniques in environmental research. This approach provides a detailed understanding of the types and quantities of pollutants that plants can capture, thereby offering valuable insights into how urban greenery can be optimized for air quality improvement. In conclusion, the study by Guru Ghasidas Vishwavidyalaya provides compelling evidence that certain plant species can effectively capture PM and toxic metals from urban air. By selecting plants with favorable micro-morphological properties, urban planners can enhance the role of greenery in mitigating air pollution. This research not only supports previous findings on the effectiveness of trees in capturing PM[3][4] but also offers new insights into the specific mechanisms and capabilities of different plant species.

EnvironmentBiochemPlant Science

References

Main Study

1) SEM-EDS-based rapid measurement and size-fractionated speciation of airborne particulate matter and associated metals utilizing plant leaves.

Published 10th July, 2024

https://doi.org/10.1007/s11356-024-34222-9

Related Studies

2) Size exclusion limits and lateral heterogeneity of the stomatal foliar uptake pathway for aqueous solutes and water-suspended nanoparticles.

https://doi.org/10.1111/j.1399-3054.2008.01135.x

3) Variation in Tree Species Ability to Capture and Retain Airborne Fine Particulate Matter (PM2.5).

https://doi.org/10.1038/s41598-017-03360-1

4) Airborne foliar transfer of PM bound heavy metals in Cassia siamea: A less common route of heavy metal accumulation.

https://doi.org/10.1016/j.scitotenv.2016.08.099


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