As well as causing considerable damage to human health, air pollutionit also cascades the growth of trees, one of the elements that canthis typical urban environmental problem.
Researchers at the University of São Paulo (USP) in Brazil havehave shown that air pollutants reduce tree growth and the ecosystemservices provided by trees, such as filtering pollution absorptionairborne metals in the crust, assimilating CO2, reducing heatisland effect by attenuating sunlight, relieving rainwaterDrain and moisture control.
The study was supported by the São Paulo Research Foundation FAPESP. The results were published in a journalThe overall environment science.
“We found that in the years when the levels of particles in the atmosphere were higher, for example, trees grew less. As a result, throughout their lifetime, they began to provide ecosystem services that play an important role in reducing urban pollution and mitigating or adapting the city to climate change, ”said Giuliano Maselli Locosselli, postdoctoral researcher at the Bioscience Institute of São Paulo (IB-USP) with the FAPESP scholarship and the first author of the study.
As a model we use tipuana tree (Tipuana tipu), also known asrosewood or tip, tall tree with large spread canopy andubiquitous in the city, scientists measured the impact of airpollution and weather on tree growth in São Paulo. They analyzed the samples41 tipuanas at age 36 on average and located at different distancesfrom industrial area Capuava in village Mauá, village in village. tMetropolitan area. Capuava is one of the most industrialized districtsoil refineries, cement plants and fertilizersfactories, as well as heavy goods and automobile transport.
Samples were taken from tree growth rings using a toolcalled a Pressler incremental drill that has a hollow drill and isdesigned to extract the cylindrical part of the wood tissue from the livinga tree over its entire radius with a relatively small plant injury.All specimens were collected at chest height, approximately 1.3 m awaytopsoil.
Analysis of bark chemistry and sizegrowth rings, scientists were able to measure changes in airpollution levels based on the different chemical elements on which they are tthe trees were exposed and estimated how they werefactor influenced tree growth.
“Tipuana is an excellent marker that clearly represents levelsair pollution by heavy metals and other chemical elements in the EU. tsaid Locosselli.
Metals and other chemicals suspended in the air are absorbedbark. The particles are deposited on the leaves and increase their contenttemperature and reduce light supplies for photosynthesis. GrowThe rings indicate how pollution has affected plant life in the yearyear. Thicker rings show years of steep growth and lower levelspollution, while thinner rings mark the opposite.
Growth ring analysis showed that these tipuans grew fasterwarmer parts of the hood with higher levels of phosphorus in the air.Phosphorus is a well-known macronutrient for plants and acts as a foundationtheir energy metabolism through photosynthesis and breathing.
On the other hand, trees near traffic and exposed to high levelsaluminum, barium and zinc associated with the automotive industryparts (eg tires, brake linings and clutch plates) are shown lessgrow.
Particles up to 10 micrometers in diameter (PM10)factories and plants have reduced the average growth of trees by so muchas 37%.
“Trees exposed directly to high levels of pollution fromfactories in the area grew less in terms of hull diameter developmentlife than plants exposed to medium and low levels, ”Said Locosselli. “Under normal growth conditions, it's a tipuanachest diameter can be 1 meter. "
The time series of PM10 levels in Cape Town for 20 years wereacquired by São Paulo State Environmental Corporation (CETESB)and compared with bark and leaf analysis results.
Researchers found that PM10 levels accounted for 41% of the year-on-yeartree growth variability, with a higher degree of pollution duringthe driest months (April – September) decreasing the growth rate.
“The diameter increases rapidly when the tree grows normallybut it changes slightly when the rate of growth is slow, "said Locosselli. "Thethe size of ecosystem services provided by a high tree can be 70times larger than a small tree. "
Effects on trees
According to the authors of the study, heavy metals and particlesmatter affects the growth of trees by changing the optical properties of the leafsurfaces. As mentioned above, these pollutants increase temperature and decreasethe availability of light for photosynthesis. They can also reduce gasexchange due to accumulation on leaf stomata (pores that open and close)carbon dioxide and oxygen release).
“We want to try to find out whether pollution also affects usthe longevity of these trees. Because the pollution limits differentphysiological systems, which prevent plant growth, probably alsothey are more vulnerable to the effects that lead to aging, "said MarcosBuckeridge, Professor in IB-USP and Chief Investigator forresearch project.
Urban pollution is also likely to damage other species in the samefamily as tipuana found in São Paulo, such as partridgewood (Caesalpiniapluviosa) and iron wood (C. leiostachya).
"Measures to reduce air pollution, such as promoting the use of biofuels,transport electrification and material developmentreduction of heavy metal emissions could improve maintenanceThese trees and ecosystem services they provide, "said Buckeridge.