Assessing the Particulate Matter Removal Abilities of Tree Leaves
October 7th, 2018
The ultrasonic cleaning method was applied to elute the particulate matter (PM) retained on leaf surfaces after PM was eluted by the conventional cleaning methods (water cleaning only or water cleaning plus brush cleaning). The methodology can help to improve the estimation accuracy for PM retention capacity of leaves.
This method can help answer key questions in the relationship between urban forests and particulate matter pollution field, such as how to select tree species with high particulate matter removal abilities. The main advantage of this technique is that the PM removal abilities of trees can be assessed accurately and quantitatively by collecting the PM retained on leaf surface completely. To begin, select five healthy individual trees with similar diameter at breast height of each tree species.
Then, randomly collect four larger branches from four directions of the out canopy in the middle canopy layer, and cut off all intact leaves. Place the leaves in labeled valve bags before transporting the bags to the laboratory and storing them in the fridge. Next, wash and dry beakers in an oven set to 80 degrees Celsius.
Equilibrate the beakers to room temperature and humidity before weighing them. After this, place randomly selected leaves into one of the large beakers. Then, add 270 milliliters of DI water to beaker A, and immerse the leaves completely.
Stir the water for 60 seconds in one direction with a glass rod. Then, evenly pour the eluent into three smaller beakers. Next, add 270 milliliters of DI water to a different large beaker, and immerse the leaves in water once more.
Using a nylon brush, scrub the leaf surfaces with the DI water, taking care to avoid destroying the leaf microstructure. Next, wash the leaves in DI water with a squeezable bottle with a fine tip, and transfer them to a new large beaker. After this, pour the eluent into a clean set of three smaller beakers.
Add 270 milliliters of DI water to the large beaker, and immerse the leaves in water again. Then, place the beaker in an ultrasonic cleaning machine for three to 10 minutes, and stir the leaves in one direction with a glass rod. Then, transfer the leaves to a new large beaker.
Next, pour the eluent into a new set of three small beakers. Cover each of the sets of three small beakers with clean filter paper, and dry the beakers in the drying oven for five days or until the mass of the beakers becomes constant. After this, put the beakers on a laboratory bench for 30 minutes, and measure the mass of each beaker.
First, add 50 milliliters of DI water to each of the small beakers. Then, place the beakers in the ultrasonic cleaning machine for 30 minutes until the PM disperses in the liquid. Add the supernatant from the beakers to a laser granularity instrument, and measure the size distribution of the PM eluted in the various cleaning steps.
Next, spread the leaves on a plastic board, and scan the leaves with a scanner. Finally, use image analysis software to estimate the surface area and projected area of the leaves. In this study, PM was eluted from the leaves of five species of trees via different cleaning methods.
A large number of different-sized PM were eluted from leaf surfaces after supplement ultrasonic cleaning to water cleaning plus brush cleaning. The average eluted proportions of various-sized PM of the five tree species by ultrasonic cleaning were 41%and 36%under the short dust retention and long dust retention periods, respectively. While attempting this procedure, it's important to remember to control the ultrasonic pulse and ultrasonic time strictly.
Following this procedure, other methods like collecting the PM retained in waxy layer of leaves can be performed in order to answer additional questions, like the production of the mass of PM on surface and in waxy layer of leaves. After its development, this technique paved the way for research in the field of forest and particulate matter pollutions to explore the particulate matter retained on leaves in selecting tree species with how particulate matter removal abilities.
View the full transcript and gain access to thousands of scientific videos
Overview
The ultrasonic cleaning method was utilized to enhance the elution of particulate matter (PM) from leaf surfaces, improving the accuracy of PM retention capacity estimations. This methodology is crucial for understanding the relationship between urban forests and particulate matter pollution.
Key Study Components
Area of Science
- Environmental Science
- Urban Forestry
- Pollution Mitigation
Background
- Particulate matter (PM) affects air quality and human health.
- Urban forests play a significant role in PM removal.
- Accurate assessment of PM retention by trees is essential.
- Conventional cleaning methods may not fully elute PM from leaves.
Purpose of Study
- To develop a method for accurately assessing PM removal abilities of tree species.
- To improve the estimation of PM retention capacity on leaf surfaces.
- To facilitate better selection of tree species for urban environments.
Methods Used
- Selection of five healthy trees of similar size from each species.
- Collection of branches and intact leaves from the middle canopy layer.
- Transporting leaves in labeled bags to the laboratory.
- Utilizing ultrasonic cleaning for effective PM elution.
Main Results
- The ultrasonic method significantly improved PM elution from leaves.
- Quantitative assessment of PM retention was achieved.
- Results support better tree species selection for PM removal.
- Methodology enhances understanding of urban forest contributions to air quality.
Conclusions
- The ultrasonic cleaning method is effective for PM assessment.
- This technique can inform urban forestry practices.
- Accurate PM retention data is vital for environmental management.
Frequently Asked Questions
Executive Industry Relevance
Accurate quantification of particulate matter (PM) retention on leaf surfaces enables data-driven selection of tree species for urban forestry programs aimed at air quality improvement. This method supports predictive confidence in evaluating natural PM mitigation strategies by providing reproducible, quantitative elution data across species and retention periods. It addresses a key discovery-stage challenge in environmental biotechnology: translating biological PM capture mechanisms into scalable, assessable systems for urban planning and green infrastructure investment.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of biological PM capture hypotheses by quantifying species-specific retention efficiencies across particle sizes.
- Operational Value: Provides standardized elution protocol (WC+BC+UC) to reduce variability in PM measurement across laboratories.
- Predictive Value: Supports triage of tree species based on measurable PM removal capacity, informing early-stage selection for urban planting programs.
Screening & Assay Development
- Assay Readiness: Delivers quantitative outputs (eluted PM mass, size distribution) suitable for high-throughput screening of plant genotypes or cultivars.
- Reproducibility: Ultrasonic cleaning step ensures near-complete PM elution, minimizing underestimation and improving assay precision.
- Scalability: Protocol uses standardized beaker volumes and controlled sonication parameters, enabling adaptation across leaf sample sizes and species.
Translational & Preclinical Research
- Translational Continuity: Links leaf-level PM retention data to urban-scale air quality modeling through species-specific retention coefficients.
- Disease-Relevant System: Uses tree leaf surfaces as a biomimetic system for assessing ambient PM capture, relevant to respiratory health impact studies.
- Mechanistic De-risking: Clarifies contribution of leaf microstructure and wax layer to PM retention, reducing ambiguity in biological mechanism attribution.
Pipeline & Workflow Integration
The method fits within the environmental discovery continuum, supporting early-stage biological screening of plant systems for PM capture capacity prior to field validation and large-scale urban deployment.
- Discovery Biology: Enables hypothesis testing on leaf traits (e.g., surface roughness, wettability) influencing PM adhesion and removal.
- Screening: Provides assay-ready, quantitative PM elution data for comparing genotypes, species, or treatments under controlled conditions.
- Analytics: Generates size-resolved PM data (ERP, DRP, TRP) enabling comparison across cleaning methods and retention periods.
- Translational Research: Supports scaling leaf-level retention data to canopy-level PM flux estimates for urban modeling.
- Enterprise Reuse: Establishes a reusable, standardized protocol for PM assessment across multiple tree species and environmental conditions.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in PM-plant interactions by enabling complete elution and size-fractionated analysis.
- Operational Value: Standardizes PM recovery via WC+BC+UC, improving inter-laboratory reproducibility and data comparability.
- Strategic Value: Informs risk-adjusted investment in urban greening by identifying species with high, quantifiable PM removal performance.
- Portfolio Impact: Enables evidence-based prioritization of tree species in urban forestry portfolios based on validated retention efficiency.
Implementation Considerations
- Requires expertise in environmental sample handling, particle sizing, and gravimetric analysis.
- Depends on access to ultrasonic cleaning equipment with controllable frequency and time parameters.
- Necessitates standardized leaf collection, storage, and cleaning protocols to minimize pre-analytical variability.
- Involves cross-team alignment between field sampling, laboratory processing, and data analysis units.
- Limited by leaf surface integrity; aggressive sonication may damage microstructure and affect PM retention accuracy.
