City's Dust Net: Six BC Pinophyta Conifers’ Dust Retention Ability and Impact on Photosynthesis Productivity
Herong (Alina) Zhang
Sir Winston Churchill Secondary
Floor Location : M 095 V

The problem of the experiment is “out of the six west coast native conifers, Pinus ponderosa (ponderosa pine), Picea glauca (white spruce), Thuja plicata (western red cedar), Thuja plicata ‘Zebrina’ (Zebrina western red cedar), Pinus monticola (western white pine), and Taxus chinensis (Chinese yew), which tree provides the highest result in dust retention? How does the dust they retained negatively affect the plant photosynthesis productivity?”

This experiment’s focuses are 1) finding the west coast native conifer species with high dust retention ability and low negative impact of the dust on the species’ photosynthesis ability, 2) investigating the effect of urban pollution on photosynthesis, and 3) observing tree species’ characteristics that work for and against dust retention and its easiness to be washed off by rain. It hopes to find the most compatible urban green space species to plant in more polluted areas in Vancouver to retain and reduce the drift of dust through the allocation of urban green space species and community design.

The hypotheses were that Thuja plicata will have the most dust retained and the most negative impact on photosynthesis, while Taxus chinesis’s photosynthesis productivity will be least impacted.

The first part of the method is finding the amount of dust each tree species can retain. It involves washing the leave samples with an ultrasonic washer, filtering out the pollution particles, then oven drying them to get accurate mass. While it is important to consider the correlations between multiple factors, the second part investigates the negative impact of the dust on the surface on the photosynthesis rate by using the dry mass to indicate the decrease in photosynthesis. Samples collected from different dates were oven-dried and weighed to compare the changes in mass. The extension looks at the micromorphology aspect of the leaf characteristics. I have observed different samples before and after a gentle rinse, representing the precipitation. By examining under the microscope, I could observe, record, and analyze unique characteristics and structures of the leaves that work for and against the ideal outcome of dust retention, being able to retain a lot of dust and allow dust to be washed off by rain easily.

From the first section, after multiple trials, the result shows that Thuja plicata retained most dust due to its scale-liked leave structure, the waxy, dust-attracting surface, and its flat positioning of the leaves. The second part shows that Thuja plicata also was most negatively impacted by the dust it retained. Its dry product mass gradually decreases as the dust overlay on the left surface throughout the dust retention process. Due to the texture and complex structure of the leaves, both micro and macro dust could not be washed off by precipitation easily. This was further proved and analyzed during the microscope observation extension. It proves the assumption of precipitation being able to wash off all dust false.

In conclusion, my hypotheses were right. It is important to take what nature has given us and use and protect it well.