In an article published inwards the periodical Environmental Pollution, Brazilian researchers showed that tree species Tipuana tipu lead keep been successfully employed every bit a marking of atmospheric pollution past times heavy metallic in addition to other chemic compounds inwards Sao Paulo, Brazil's biggest metropolis.
 |
| The chemic composition of the tree's growth rings reflects the levels of heavy metals inwards the soil twelvemonth past times twelvemonth [Credit: Giuliano Maselli Locosselli] |
Tests were carried out inwards enterprise to compare the functioning of iii of the nearly mutual tree species inwards the city: privet (Ligustrum sp.), sibipiruna or partridgewood (Caesalpinia pluviosa), in addition to tipuana.
With the back upward of São Paulo Research Foundation - FAPESP via a Thematic Project , a regular question grant in addition to a postdoctoral question scholarship, the question attested a reduction inwards the levels of pollution past times cadmium, copper, nickel in addition to Pb inwards the westward of the urban centre inwards the final thirty years.
The roots of the tipuana tree absorb heavy metals in addition to other chemicals that are acquaint inwards the atmosphere in addition to autumn to the solid lay down inwards rainwater. These chemicals are transported inwards sap past times the tree's xylem cells in addition to stored inwards the woods of its growth rings - those concentric circles visible inwards a cross-section of the trunk.
Each growth band represents a twelvemonth of the tree's life. The to a greater extent than recent rings are wider in addition to further from the center. Those closest to the optic are narrower. The chemic composition of the tree's growth rings reflects the levels of heavy metals inwards the soil twelvemonth past times year, in addition to the results tin lav live compared to decide how this type of pollution has varied on a scale of decades.
"If a tree is fifty years old, for example, it volition say the story of pollution inwards the urban centre during that period," said Giuliano Maselli Locosselli, a postdoctoral researcher at IB-USP in addition to commencement writer of the study.
All the spell Tipuana bark analysis shows the levels of atmospheric chemicals that lead keep been passively deposited inwards this external role of the trunk.
By touchstone the levels of heavy metals inwards samples of bark from trees all the same standing inwards unlike neighborhoods of the city, the researchers tin lav map spatial variations inwards these levels on a scale of years.
"It's easier to obtain samples of bark than annual growth rings, in addition to the chemic analysis of bark is less costly, in addition to hence nosotros tin lav analyze samples from many trees in addition to comprehend a large area", said the FAPESP scholarship holder. "The trial is a map of pollution past times heavy metals in addition to other chemic elements throughout the city."
Falling levels of pollution past times heavy metals
The researchers conducted an initial written report inwards which they measured the levels of cadmium, copper, mercury, nickel, sodium, Pb in addition to zinc inwards rings from 2 tipuana specimens growing inwards the gardens of the University of São Paulo's Medical School inwards the westward of the city's cardinal region. Their destination was to analyze the temporal changes inwards the levels of heavy metallic pollution inwards this role of São Paulo.
The 2 trees used inwards this written report were 35 years old. Samples were taken from their growth rings using an musical instrument called a Pressler increment borer, which has a hollow auger fleck in addition to is designed to extract a cylindrical department of woods tissue from a living tree throughout its radius amongst relatively tike injury to the establish itself.
"The physical care for tin lav live compared to a tree biopsy," Locosselli said.
The 15-mm annual growth band samples were sent to Marco Aurelio Zezzi Arruda, a professor at the University of Campinas's Chemistry Institute (IQ-UNICAMP). There, the samples were scanned past times Light Amplification by Stimulated Emission of Radiation ablation coupled amongst volume spectrometry, generating software-processed images for chemic analysis.
The researchers selected the cells of involvement in addition to performed a continuous analysis of all the annual growth rings to mensurate the levels of heavy metals absorbed past times the trees inwards each twelvemonth of their lives.
The information analysis pointed to a pregnant reduction inwards pollution past times cadmium, copper, nickel in addition to Pb inwards the final iii decades inwards the role of the urban centre inhabited past times the sampled tipuana trees, likewise every bit a to a greater extent than moderate decrease inwards the levels of sodium in addition to zinc.
"The falling levels of Pb reflected the gradual elimination of this chemic chemical factor from the composition of Brazilian gasoline," said Marcos Buckeridge, coprincipal investigator at the FAPESP Thematic Project in addition to a coauthor of the study.
"The downtrend inwards cadmium, copper in addition to nickel pollution in all likelihood reflects enhanced vehicle efficiency in addition to deindustrialization inwards São Paulo," Buckeridge said.
Tetraethyl Pb was used worldwide every bit an antiknock agent inwards automotive gasoline for much of the twentieth century to amend engine functioning in addition to trim down wear. The resulting unloosen of Pb into the atmosphere via vehicle exhaust was a severe wellness hazard.
Brazil banned the add-on of tetraethyl Pb to automotive gasoline inwards 1988.
The principal sources of cadmium inwards ambient air pollution are the electronic appliance industry, pigments used inwards pigment in addition to dye, batteries, photography, lithography, fireworks, plastic, semiconductors, solar cells, fuels, urban garbage, tire rubber, in addition to electroplating. The principal sources of copper emissions are the burning of urban in addition to industrial waste, metallic alloy casting, in addition to pesticides.
"The levels of these chemic elements inwards São Paulo's ambient air lead keep fallen inwards recent decades owing to deindustrialization," Locosselli said.
Author: Elton Alisson | Source: Fundação de Amparo à Pesquisa produce Estado de São Paulo [September 13, 2018]
Sumber http://archaeologynewsnetwork.blogspot.com
Buat lebih berguna, kongsi:
