Tatiane Araujo de Jesus (right) and her team have done pioneering research in São Paulo, Brazil. With a unique method known as paleolimnology, they revealed a long century of metal pollution, primarily manganese and lead. Scientists studied the sediment layers from Garças Lake, located in Ipiranga Fountains State Park (PEFI). More importantly, they were even able to document large increases in metal concentrations over time to directly attribute these changes to urban development and industrialization.
The study focused on eight metals: cobalt, chromium, copper, iron, manganese, nickel, lead, and zinc. Overall, the study’s results suggest that before the year 1950—when global industrial activity began to increase—metal levels were at a pre-industrial baseline level. As São Paulo began going through an intense industrial development and urbanization, pollution increased exponentially.
Methodology and Significance of the Study
Tatiane Araujo de Jesus leads the Ecological Engineering Systems Laboratory at the Federal University of ABC (UFABC). She emphasized the important role that Garças Lake has in this research. The lake was chosen for its relatively undisturbed sediment layers, which have formed a natural record of contaminant deposition.
Nearly all the processes that occur in a drainage basin ultimately become encoded in the sediments of aquatic landscapes. We had selected Garças Lake since it had never been dredged before. This decision gave us the opportunity to maintain the temporal order of pollutant deposition,” said Araujo de Jesus.
In order to analyze the sediment layers properly, the researchers dug deep into each layer’s history using lead-210 isotopes to date the layers precisely. Araujo de Jesus explained, “Lead-210 has a half-life of approximately 22.3 years, so through the activity of this isotope, we were able to assign an age to each layer of sediment, as if we were numbering the pages of a book.”
Pollution Trends Over Time
For the first time, this analysis demonstrated that metal pollution started increasing steadily between 1950 and 1975. For example, the opening of the Imigrantes Highway in this era greatly increased vehicle traffic in the region. The darkest times in peak pollution years were 1975-2000. Over the years, metals including lead, nickel, iron, chromium, and copper saw increased tidal levels.
Araujo de Jesus noted that “we observed that most of the metals detected came from vehicle and industrial emissions.” The findings paint a bleak picture. Rapid urbanization and industrial activity had taken a major toll on the environment in São Paulo.
In 1986, Brazil adopted the Vehicle Emissions Control Program (PROCONVE) that phased out leaded gasoline. This concerted effort prompted a rapid reduction in lead concentrations in the lake’s sediments. “Until then, lead was used as an additive in gasoline, and with its ban, we saw a decrease in its concentration in sediments. This shows how environmental policies can have positive and measurable impacts,” she stated.
Even while lead levels dropped, the levels of other metals more than tripled across the 1990s. Cobalt, nickel, and copper were among the metals with the largest price gains. Araujo de Jesus stressed that even with past pollution, new pollution is still an issue.
Implications for Urban Environmental Management
Overall, the study’s historical data findings underscore the need to look back in order to go forward with the best environmental management strategies. By trying to piece together the historical pollution timeline, researchers can more accurately determine the lasting effects of urbanization on aquatic ecosystems.
“Historical data helps us understand how we got here and can serve as a basis for more informed decisions about the future of the city’s environmental quality,” said Araujo de Jesus. She claimed that sediment analysis can be an important tool for directing restoration work.
It’s not enough only to fence in a space and label it a park. If air pollution and the deposition of pollutants aren’t controlled in the surrounding area, the impact will continue,” she cautioned.
The researchers hope to use what they learned to determine restoration targets for Garças Lake and other ecosystems like it. “What we can do now is use this data to set restoration goals. We know what the natural levels of these metals were before industrialization, and we can work to try to reverse some of the impact,” Araujo de Jesus concluded.