Scientists say they have found the cleanest air on Earth
CNN article: https://www.cnn.com/2020/06/02/world/cleanest-air-intl-scli-scn-climate/index.html
PNAS article: https://www.pnas.org/doi/full/10.1073/pnas.2000134117
Zach Rose
Chem 474
As we read through the PNAS article, beyond the errors previously mentioned, the CNN article seems to be fairly accurate, albeit far less technical and detailed. Woodyatt used “wind back trajectories” instead of “atmospheric back trajectory analysis” to describe the method used to determine the origin of the airborne microbes that were tested, but I’d say this is a fairly small mistake. The CNN article does mention that aerosols over the Southern Ocean were dominated by marine bacteria, which is echoed in the PNAS article in addition to a wealth of taxonomic details of the composition and phylum level variation of these microbial communities at different latitudes. However, Woodyatt fails to capture the significance of this finding, as most bioaerosol studies typically find a larger contribution from terrestrial bacteria. The PNAS article goes on to explain that microbial communities clustered at three distinct latitudinal bands (44-51°S, 54-62°S, and 64.5-65.5°S) and that species richness decreased as latitude moved south.
Overall, Woodyatt does a modestly good job at capturing the main takeaway of Kreidenweis’s research, including most of the major findings, with the notable exception of discussing any of the findings relating to microbial community diversity gradients. This mistake, along with a few smaller ones mostly relating to terminology lead me to give this article from Woodyatt a 5/10.
The CNN article, “Scientists say they have found the cleanest air on Earth” was published on June 2, 2020, by Amy Woodyatt. In it, she describes the findings of Sonia Kreidenweis and team published in PNAS a day earlier. Woodyatt calls it a “first-of-its-kind study” of the bioaerosol composition over the Southern Ocean, detailing the results while mixing in some necessary background information and key methods used by Kreidenweis’s team. The CNN article states that the researchers found the boundary layer air, which “feeds the lower clouds over the Southern Ocean”, was free from anthropogenic aerosols. Woodyatt explains that the scientists sampled the air at the marine boundary level (which I had to assume is different from the boundary layer mentioned previously) as well as the composition of airborne microbes and found “from the bacterial composition of the microbes” that aerosols from human activities were not traveling south. The team essentially found that there was a sort of barrier overtop Antarctica and the Southern Ocean, leading air in this region to be “truly pristine”.
Although CNN did not provide a link to the article, it mentioned enough of the authors as well as the journal it was published in to make it an easy find. When reading through the PNAS article, it became clear where Woodyatt succeeded in ‘translating’ and where her shortcomings were.
From the abstract alone, we can learn that she was correct in that no other regionwide studies of bioaerosol composition over the Southern Ocean had been conducted. However, she failed to mention that the study was conducted only in the summer and thus could not be generalized to year-round conditions as weather patterns, especially over the Southern Ocean and Antarctica, change with the seasons and so the aerosol composition could also vary. Woodyatt correctly described the method of data collection, sampling from a research boat, but misled readers (including myself) by using two different terms for the region of air that was sampled (“boundary layer” and “marine boundary level”). The CNN article also missed another important finding from the PNAS article: that ꞵ-diversity (ratio of local to regional diversity) varied only with latitude and temperature. No mention of anything related to diversity or community composition could be found in the CNN article.
Although CNN did not provide a link to the article, it mentioned enough of the authors as well as the journal it was published in to make it an easy find. When reading through the PNAS article, it became clear where Woodyatt succeeded in ‘translating’ and where her shortcomings were.
From the abstract alone, we can learn that she was correct in that no other regionwide studies of bioaerosol composition over the Southern Ocean had been conducted. However, she failed to mention that the study was conducted only in the summer and thus could not be generalized to year-round conditions as weather patterns, especially over the Southern Ocean and Antarctica, change with the seasons and so the aerosol composition could also vary. Woodyatt correctly described the method of data collection, sampling from a research boat, but misled readers (including myself) by using two different terms for the region of air that was sampled (“boundary layer” and “marine boundary level”). The CNN article also missed another important finding from the PNAS article: that ꞵ-diversity (ratio of local to regional diversity) varied only with latitude and temperature. No mention of anything related to diversity or community composition could be found in the CNN article.
Fig 1: ship track and sampling sites. Kreidenweis's team sampled soil, ocean sediment, air, and water (via PNAS article)
Overall, Woodyatt does a modestly good job at capturing the main takeaway of Kreidenweis’s research, including most of the major findings, with the notable exception of discussing any of the findings relating to microbial community diversity gradients. This mistake, along with a few smaller ones mostly relating to terminology lead me to give this article from Woodyatt a 5/10.
These findings were interesting to me, especially regarding the fact that the majority of the aerosols found were microbial. Typically, when I think of aerosols, I default to thinking of harmful particulate matter put into the atmosphere from human activity, not naturally occurring bioaerosols . In the scientific article, did they differentiate between different types of aerosols, with some being more or less polluting?
ReplyDeleteThe only aerosols discussed in this article were the ambient samples collected by the research team on their voyage. Most of these aerosols came from ocean spray, and they happened to contain a large amount of microbes.
DeleteAfter looking through the paper, I'm wondering what the patch of air is like during the winter and if it's as pristine as it is during the summer. If that's the case, how would the biodiversity of the bacteria change? This paper brings up a lot of questions for me and I hope the scientists come back to answer them.
ReplyDeleteIn terms of the article, I am a bit dismayed that the author generalized the findings, but I honestly think she did that to encourage people to read it. To most people, most of what they read on atmospheric pollution is negative, so her title stands out a lot.
Agreed, the "pristine air" finding was clearly the most positive and the CNN author wanted to share some optimism. As to how the atmosphere patterns over Antarctica and the SO change from summer to winter, I am less sure, but a rudimentary guess is that an increase in solar energy in the winter (assuming seasons are flipped in the southern hemisphere) would lead to increases in microbial populations, and maybe diversity too.
DeleteI think it's very crucial that you pointed out the mistake the CNN article made of not mentioning anything microbial related. I read the CNN article first and thought that everything was nicely laid out and explained properly. Then when I opened the PNAS link, literally in the first paragraph
ReplyDelete(titled "significance" no less) it talks about how in the marine boundary layer there is an abundance of marine bacterial due to sea sprays. Even in the abstract it talks about how the aerosol samples they collected were profiled for marine bacteria. Despite that major shortcoming the CNN article definitely does a good job of putting the PNAS article into simpler terms. I was wondering though why the CNN article chose that title about "the cleanest air on earth". Does the bacterial profile of the aerosols in the region correlate to purity or cleanliness of the air? I feel like that is a very bold claim to make especially with the limitations on the study like the fact that they took a summertime reading of the aerosols.
My best guess is that the CNN author keyed into the "truly pristine" quote from the research team and ran with it, which stemmed from the near-absence of anthropogenic aerosols that the research team found in their samples. Adding in the information about the microbial communities would have made things too complicated, I guess.
DeleteHi Zach, I think you made some really good points about how the article conveys the PNAS article published by the Colorado State researcher team. In addition to some of the factual gaps/lack of clarifications you mentioned, the title is quite misleading. I think Woodyatt saw a sentence or two from the significance/abstract and rolled with it, but considering this research was only done south of Australia (and simply looked at bacterial profiling) makes her claim a tad outlandish. Combining those points with having no imagery relayed from the research, I would think a 4/10 would be my rating even though some key facts are relayed. One question I have after reading the peer-reviewed article a bit--they mention "prior research...suggested strongest [aerosols bacteria-profiling] transport...occurs in wintertime"--did they mention anything about the specific anthropogenic sources when comparing these differences? Perhaps I'm reading over something, but I guess it'd be good to know more info about what's in the aerosols in the region.
ReplyDeleteLucas,
ReplyDeleteI was actually okay with the title since I think the CNN author is mostly referencing the lack of anthropogenic/continental PM found in the aerosol samples. But you're right, the fact that testing was only conducted in summer and mainly focusing on microbial community compositions makes it a bit of a stretch. To answer your question, based on the context of the rest of the paragraph my guess would be that the sources they were concerned with here was dust from inland Australia blowing south in winter, which is likely not an anthropogenic source.
My biggest qualm with this news article is, as you mentioned, no distinction of the time period of which this study was conducted. If the study was year long and took into account measurements from all seasons, that would provide greater support for "the cleanest air on earth" claim. This study also only measures bioaerosols. I'm sure there are trends for the bioaerosol composition of the atmosphere based on human activities in the area, such as large agricultural areas often contributing to harmful algal blooms which can generate bioaerosols. However, this study did not measure any other pollutants such as ozone, NOx, or biomass burning emissions. I don't think the article's tittle can accurately make the claim that scientists have found the "cleanest air on earth" purely based on this study. To accurately make that claim, many other pollutants would need to be measured year round and compared to other regions. For this reason, I agree with the low rating of 5/10.
ReplyDeleteHi Zach, thank you for sharing this crucial point with us. In a groundbreaking study, researchers from Colorado State University have pinpointed the world's purest air, untouched by human activity, over the Southern Ocean surrounding Antarctica. Their innovative approach involved analyzing airborne microbes to assess the air's pristine nature. Unlike many other regions, the boundary layer air over the Southern Ocean was found to be free from aerosol particles originating from human activities such as fossil fuel burning, agriculture, and industrial processes. This revelation casts a luminous spotlight on the Southern Ocean as one of the planet's rare untouched sanctuaries, all the while accentuating the pervasive global dilemma of air pollution, which transcends boundaries and reverberates through public health concerns. This remarkable discovery not only unveils the purity of the Southern Ocean's air but also invites us to think innovatively about how we can protect and cherish the unspoiled corners of our planet in the face of mounting environmental challenges. But, I am wondering how could innovative technologies or sustainable practices inspired by this discovery help mitigate the effects of air pollution in more populous and polluted regions of the world?
ReplyDeleteI would agree with yours and other students comments on the limited sample size of the study. The paper does discuss this limitation, but the article makes these findings out to be a declarative fact. Additionally, the article has very limited information on how these bioaerosols were actually studied and distinguished. It would have been nice if they elaborated on anthropogenic aerosols versus those found naturally over the South Ocean. Furthermore, I would have liked to have seen the author put the scientific findings and processes into simple terms rather than just gloss over the process and cut straight to the results. However, I think the article does do a good job at elaborating on the human health impacts of various pollutants. Overall, I would agree with your rating.
ReplyDeleteI agree with you and a few of the other commenters. It is alarming that the article focuses so much on what the scientists say but it fails to cover the true scope of the research and some of their most important findings. I also would be very interested if they expanded their research to different areas and times of year since. The article does a decent job of making sense of aerosols for the general population and why they are important, however they should have done so without using such definite words that lead to readers being confused about how much research really has been done.
ReplyDeleteThis is a cool article! I think during discussions of air pollution and how far pollutants actually travel, it can be relatively easy to assume that nowhere is left on Earth where there is purely "untouched" air. I think it's interesting that they started out the article by focusing heavily on the last sentence of the "significance" section of the original paper. However, it's understandable as their job is to grab people's attention, so I get why this was done from a science communication perspective. Additionally, I do think it's nice that the article gave numbers on air pollution and just how much people are affected, saying things like "air pollution is already a global public health crisis, and kills seven million people each year", "air pollution increases the risk of heart disease, stroke and lung cancer", and "more than 80% of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed WHO guideline limits." All of these statistics definitely convey the sense of importance of understanding our air chemistry to the average person.
ReplyDeleteAs other commenters have mentioned, I'm curious to see if this study would be any different if conducted in other seasons. I think it would've been interesting to see how climate impacted these aerosols especially because it seems like pollution is worse in colder months so I wonder if this would still be considered the "cleanest air on earth".
ReplyDelete