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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Pollen production could impact climate change by helping clouds form   
      
      
     Date:   
         May 8, 2023   
     Source:   
         American Chemical Society   
     Summary:   
         For millions of people with seasonal allergies, springtime means   
         runny noses, excessive sneezes and itchy eyes. And, as with many   
         things, climate change appears to be making allergy season even   
         worse.   
      
         Researchers have now shown that common allergen-producing plants   
         ryegrass and ragweed emit more smaller, 'subpollen particles'   
         (SPPs) than once thought, yet climate would likely be most affected   
         by their intact pollen grains, which can boost cloud formation.   
      
      
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   FULL STORY   
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   For millions of people with seasonal allergies, springtime means runny   
   noses, excessive sneezes and itchy eyes. And, as with many things, climate   
   change appears to be making allergy season even worse. Researchers   
   reporting in ACS Earth and Space Chemistry have shown that common   
   allergen-producing plants ryegrass and ragweed emit more smaller,   
   "subpollen particles" (SPPs) than once thought, yet climate would likely   
   be most affected by their intact pollen grains, which can boost cloud   
   formation.   
      
   In addition to annoying sinuses, pollen naturally functions as a way   
   for plants to exchange genetic material and reproduce. When exposed to   
   moisture, these pollen grains can burst into tiny SPPs less than a micron   
   long. Their smaller size allows them to reach the lower respiratory   
   system, where they can last longer and cause more inflammation than   
   their larger counterparts. Both SPPs and whole pollen grains are also   
   thought to act as ice nucleation sites - - miniature starting points for   
   clouds. But compared to regular clouds, SPPs and pollen form smaller,   
   more numerous clouds that tend to hold onto their precipitation, helping   
   trap in radiant heat and contributing to climate change.   
      
   In turn, higher temperatures can extend pollen-release periods, further   
   exacerbating the problem. Previously, Brianna Matthews, Alyssa Alsante   
   and Sarah Brooks studied how oak trees emit SPPs at different humidity   
   levels. But this time, the team wanted to investigate how two other common   
   allergen- producing plants, ragweed and ryegrass, release SPPs under humid   
   conditions, and how those particles could affect ice cloud formation.   
      
   The researchers collected samples of ryegrass and ragweed, then placed   
   them into a specialized "pollen chamber." There, the samples were exposed   
   to different humidity levels and bursts of wind over several hours to   
   simulate real-world conditions.   
      
   The group assessed the number of SPPs per pollen grain, as well as the   
   abilities of both to nucleate ice. Surprisingly, the team found that   
   previous experiments on the same types of plants underestimated the   
   amount of SPPs by a factor of 10 to 100. This was likely because the   
   other experiments used a less realistic means of spreading the pollen and   
   generating the SPPs, say the researchers. Ragweed and ryegrass SPPs were   
   very poor ice-nucleating sites, however -- barely better than plain water   
   -- while whole pollen grains facilitated cloud growth. The researchers   
   say that these updated parameters and numbers of emitted pollen grains and   
   particles could ultimately be used to create more-accurate climate models.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Endangered_Plants # Nature # Agriculture_and_Food #   
                   Endangered_Animals   
             o Earth_&_Climate   
                   # Climate # Global_Warming # Environmental_Awareness   
                   # Ice_Ages   
       * RELATED_TERMS   
             o Hypoallergenic o Allergen o   
             Paleoclimatology o Global_climate_model o   
             Global_warming_controversy o Kyoto_Protocol o   
             Consensus_of_scientists_regarding_global_warming o   
             Temperature_record_of_the_past_1000_years   
      
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   Story Source: Materials provided by American_Chemical_Society. Note:   
   Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Brianna H. Matthews, Alyssa N. Alsante, Sarah D. Brooks. Pollen   
      Emissions   
         of Subpollen Particles and Ice Nucleating Particles. ACS Earth   
         and Space Chemistry, 2023; DOI: 10.1021/acsearthspacechem.3c00014   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230508150934.htm   
      
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