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In many cities, the concentrations of some pollutants decreased while others increased. However, Jakarta, Indonesia was the only country to see a statistically significant improvement in overall air quality as a result of government policies.
The improvement is relative as Jakarta still has a serious air pollution problem, but the trends there have pointed to how effective targeted policies can be in reducing pollution. The city has emissions standards for vehicles and has seen a reduction in nitrogen dioxide associated with vehicle exhaust, the researchers said. But it has no limits on burning biomass, such as burning it to clear soil after a harvest, and has seen increased ammonia concentrations associated with such agricultural activities.
Overall, however, the researchers found that most of the increased pollution came from sources such as traffic and fuel burning, not from biomass combustion—a distinction the researchers were able to make because biomass combustion occurs in intense but relatively short bursts in satellite observations. , often with a seasonal pattern. Other human activities produce less intense but longer-lasting pollution.
“Open combustion of biomass for land clearing and agricultural waste disposal has in the past dominated air pollution in the tropics overwhelmingly,” said Karn Vohra, research fellow at University College London and lead author of the study. “Our analysis shows that we are entering a new era of air pollution in these cities, with some of the degradation rates experienced within a decade that other cities experienced in a decade.”
The study does not specifically answer the question of which activities are most responsible.
Dr. “The driver of these trends is anthropogenic activity, but it’s so broad—there’s a lot of anthropogenic activity happening in a city,” Marais said, adding that more scientific research is needed to identify the biggest contributors.
Next, he said, it will be up to policymakers to conduct cost-benefit analyzes and identify the most effective and economically viable ways to reduce pollution.
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