New Publication: Human influence on particulate matter in the Amazon

We hear a lot about particulate matter these days, mostly in the context of air pollution in inner cities. But what about particulate matter in the Amazon rainforest? Well, the short answer is that particulate matter is present in the air above the Amazon, too. And although its concentrations are lower than those in large cities, urbanization and deforestation fires have a significant impact. To find out what that impact exactly is, was the aim of a new study by Suzane de Sá and co-authors.

They analyzed the concentration, composition and properties of particulate matter in the central Amazon. As part of the GoAmazon campaign, they collected data during the dry season, when burning events are most frequent. Their primary study site was downwind of Manaus, but they used the ATTO site with its relatively clean air upwind of Manaus for comparison. To have this comparison is important to identify the effects of urban pollution and forest burning on the natural background. The mean concentration of particulate matter found at the study site was ca. 12 µg/m3 in the small PM1 fraction (particles smaller than 1µm in diameter). For comparison, average values in European cities are in the range of 15 to 20 µg/m3. But in areas with severe air pollution, those values can skyrocket and reach over 100 µg/m3.

In the Amazon, particles from biomass burning and urban pollution account for ca. 30 % of all particulate matter, while the rest comes from biogenic sources. The team also found a much higher overall concentration of particulate matter during the dry season. This is in part because of the increase in particles from anthropogenic sources. But the amount of particles from biogenic sources also increases during that time. But even though the anthropogenic fraction of particulate matter is relatively low, they absorb much more light than biogenic particles do. This, in short, makes the air warmer. Biogenic particles reflect more light, counteracting the greenhouse effect to some degree.

The paper was recently published in Atmospheric Chemistry and Physics and is available Open Access: 10.5194/acp-19-7973-2019

New Publication: biodiversity of microorganisms within aerosols of the Amazon rainforest

It is well established that aerosols are relevant for the climate, for example, because they contribute to cloud formation. However, natural, biological aerosols emitted by plants serve another important purpose. They help disperse living microorganisms across the globe, affecting their distribution. Yet little is known about those bioaerosols emitted by pristine forests such as the Amazon. And even less about the diversity of the microorganisms in the aerosols.

Felipe Souza and co-authors now collected bioaerosols at our ATTO site. Then they extracted and analyzed the DNA to determine the communities present. This is the first study which described the community of microorganisms within aerosols in the Amazon. They found many different types of bacteria and fungi. Some were cosmopolitan taxa, but they also identified many that are specific to certain environments such as soil or water. This suggests that the atmosphere may act as an important gateway for bacteria to be exchanged between plants, soil, and water.

Their results also reveal that the main source for bioaerosols emitted from the Amazon rainforest are organisms that are known to disperse their spores through the atmosphere: fungi and bacteria. We know that these groups of organisms can produce enzymes and metabolites including antibiotics. Finding them in the vast jungle wilderness of the Amazon, however, is difficult. Analyzing forest aerosols may be a way to localize them for the potential use in biotechnological applications.

Souza et al. published this paper as a Short Communication in Science of the Total Environment.

Dias‐Júnior et al. (2019) analysed prokaryotic diversity from DNA in the Amazon
Graphic Abstract from Souza et al. (2019)

New Publication: Inertial Sublayer over the Amazon Rainforest?

The Amazon rainforest interacts with the atmosphere by exchanging many substances. Many of these, such as carbon dioxide, methane, ozone, and organic compounds, are produced by the vegetation. They are very influential in both the regional and global climates. Until now, the estimates of their emission and absorption rates are based on classical theories. But those were developed over relatively short vegetation and are valid for the so-called the “inertial sublayer.”

Cléo Quaresma Dias‐Júnior and co-authors now checked if such an inertial sublayer even exists over the Amazon, where trees grow much higher. With an average tree height of some 40 meters, they expected it at around 100 meter above the forest floor.

They measured a number of atmospheric parameters that typically change between layers at different heights of the ATTO 80m tower and the Tall Tower. However, they found no evidence that such an inertial sublayer exists. Instead the roughness sublayer (the layer directly above the surface) directly merges with the convective mixed layer above. Crucially, this means that new methods and theories will be needed to address the absence of the inertial sublayer to improve the estimates of fluxes over the Amazon rainforest.

The paper was recently published in Geophysical Research Letters: 10.1029/2019GL083237

ATTO Meeting 2019

We’re excited to announce that this year our annual ATTO meeting takes place on September 16-18 and will be hosted by INPA in Manaus.

The meeting is open to all consortium member and invited guests and we can’t wait to see everyone there! The focus of the meeting will be scientific exchange. We will share progress on ongoing projects, discuss upcoming ones and perhaps even find new collaborators. Therefore, we will dedicate a considerable portion of the meeting time to posters.

We will announce more details on schedule, program and logistics shortly so stay tuned and save the date!