2024-07-19 パシフィック・ノースウェスト国立研究所(PNNL)
＜関連情報＞
- https://www.pnnl.gov/publications/agricultural-soils-are-efficient-ice-nucleating-particles-southern-great-plains
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JD040826
サザン・グレート・プレインズ・サイトのINPにおけるリン酸塩、鉛、混合土壌有機粒子の濃縮 Enrichment of Phosphates, Lead, and Mixed Soil-Organic Particles in INPs at the Southern Great Plains Site
Gavin C. Cornwell, Isabelle Steinke, Nurun Nahar Lata, Alla Zelenyuk, Gourihar Kulkarni, Mikhail Pekour, Russell Perkins, Ezra J. T. Levin, Swarup China, Paul J. DeMott, Susannah M. Burrows
Journal of Geophysical Research: Atmospheres Published: 26 June 2024
DOI:https://doi.org/10.1029/2024JD040826
Abstract
Ice nucleating particles (INPs) are rare particles that initiate primary ice formation, a critical step required for subsequent important cloud microphysical processes that ultimately govern cloud phase and cloud radiative properties. Laboratory studies have found that organic-rich dusts, such as those found in soils, are more efficient INPs compared to mineral dust. However, the atmospheric relevance of these organic-rich dusts are not well understood, particularly in regions with significant agricultural activity. The Agricultural Ice nuclei at the Southern Great Plains field campaign (AGINSGP) was conducted in rural Oklahoma to investigate how soil dusts contribute to INP populations in the Great Plains. We present chemical characterization of ambient and ice crystal residual particles from a single day of sampling, using single particle mass spectrometry (SPMS) and scanning microscopy. Ambient particles were primarily carbonaceous or secondary aerosol, while the fraction of dust particles was higher in the residual particles. We also observed an unusual particle type consisting of a carbonaceous core mixed with dust fragments on the surface, which was found in higher proportion in residuals. Dust particles measured during residual sampling contained greater proportions of phosphate (63<?XML:NAMESPACE PREFIX = “[default] http://www.w3.org/1998/Math/MathML” NS = “http://www.w3.org/1998/Math/MathML” />PO2− and 79PO3−) and lead (206Pb+). Strong sulfate signals were not seen in the residual dust particles measured by the SPMS, while nitrate was slightly depleted relative to ambient dust. This study shows that organic-rich soils may be important contributors to the ambient INP population in agricultural regions.
Key Points
- Ice nucleating particle composition was directly measured with the ice crystal residual method using two characterization techniques
- Dust residual particles contained greater phosphate and lead relative to ambient dust particles
- Carbonaceous particles internally mixed with dust fragments were found in residual particles measured by SEM/EDX
Plain Language Summary
Ice nucleating particles (INPs) affect climate by causing clouds to freeze at warmer temperatures. However, they are very rare which this means that they are challenging to characterize. Agricultural soils have exhibited high ice nucleation activity in lab studies though their relevance to ambient INP populations is unknown. In this work, we directly measure INP composition in a field campaign at a site in the middle of farmlands to determine whether they are an important source of INPs. We show that dust particles, along with carbonaceous particles mixed with dust, are enriched in INP samples relative to ambient particles. We also show that phosphate (presumed to come from biological fragments) and lead may enhance the IN activity of dust particles.
