Ryan C. Sullivan

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-A10 ARM-NSA-Barrow. This is the FLUXNET version of the carbon flux data for the site US-A10 ARM-NSA-Barrow produced by applying the standard ONEFlux (1F) software. Site Description - This site is located at ARM North Slope of Alaska site near Barrow, AK

Reconstructing the source regions of past atmospheric dust preserved in ice remains a challenge in Antarctic glaciology. Until now, different dust properties were obtained by separate techniques and could not be directly correlated at single particle level limiting the dust characterization. Here we apply a novel technique (single particle Inductively Coupled Plasma-Time of Flight Mass Spectrometry) to characterize millions of individual particles in low-volume (< 2 mL) ice samples. We analyzed more than 2,000,000 individual particles smaller than 2.5 µm in 28 discrete samples from Taylor Glacier, coastal East Antarctica, spanning 44-9 kyr BP. We show a glacial-interglacial shift in particle number and mass concentrations, as well as in the elemental and mineralogical compositions. Our observations suggest a common potential dust source area for central and coastal East Antarctica during the Last Glacial Period, followed by a transition to different dominant sources in coastal sites during the Holocene. These changes likely reflect large-scale variations in dust sources, and environmental conditions in the Southern Hemisphere. We have also identified and measured the elemental composition of thousands of volcanic particles < 2.5 µm, indicating occasional tephra deposition from one of the Victoria Land volcanoes around 14.8 kyr BP.

Biomass-burning aerosol (BBA) is emitted by combustion through wildfires and prescribed burns. As BBA contains chromophoric brown carbon, this aerosol increases radiative forcing and drives particle-phase photochemistry such as generation...

Abstract Ice nucleating particles (INP) capable of nucleating ice crystals via immersion freezing at temperatures above approximately −35°C may strongly influence cloud glaciation, with implications for global precipitation and climate feedback. In addition to mineral dust, soil dust, and marine organics, laboratory and field measurements suggest biomass burning aerosols (BBA) can act as immersion‐mode INP between around −30°C and −15°C. However, the contribution of BBA to the global INP budget remains poorly understood due to poor knowledge of which fuels yield INPs, uncertainties in global coverage of those fuels, and unknown size distributions of the INPs in the BBA. Nonetheless, with some understanding of these uncertainties from sensitivity studies, the relative importance of ice nucleation activity of BBA compared to other INP sources can be quantified. In this work, we investigate the potential global importance of BBA as INP using a global aerosol‐climate model, specifically the UK Met Office Unified Model (UM). We evaluate the model using field campaign data sets. We examine potential uncertainties in fuel types and particle sizes on BBA‐based INP concentrations. Averaged over June–September between 15°S and 50°S, BBA is a more important INP than dust and marine INP about 30% of the time at altitudes with temperatures between −30°C and −20°C. Our simulations therefore suggest BBA INPs may be at least as important as mineral dust and marine INP over the atmospheric regions and seasons where grassland fires are frequent.

The third-order difference equation yn+1=a1yn21+yn2+a2yn−121+yn−12+a3yn−221+yn−22, as a potential discrete time model of population dynamics with three generation involved, is studied. The parts of the basins of attraction of three equilibrium points that this equation admits are described. Some results about period-two and period-three solutions have been established.

High Resolution Image Download MS PowerPoint Slide It is generally assumed that acidic submicron atmospheric aerosol particles do not constitute a significant sink for nitrous acid (HONO), as this weak acid would remain protonated and volatile, yet the uptake of HONO to larger less acidic particles is unexplored. Experiments on optically tweezed aerosol did not observe HONO gas uptake but instead revealed rapid oxidation of HONO to HNO 3 in droplets of initial pH between 0 and 7.75. This oxidation was spontaneous at room temperature with no oxidant added and occurred over a subminute time scale. The reaction is accelerated under acidic conditions of pH < 2. We hypothesize that protonated HONO is restricted to the interfacial region while NO 2 – is not, and HONO is therefore oxidized to HNO 3 following a second-order rate dependence on the HONO concentration. The oxidation of HONO can thus be self-catalyzed in weakly buffered aerosol. Less acidic droplets (pH > 5.0) displayed an approximately 2 orders of magnitude lower conversion rate of HONO to HNO 3, likely due to deprotonation and then slower oxidation of NO 2 – directly to NO 3 – with a first-order dependence on the NO 2 – concentration. Production of HNO 3 can drive a liquid–liquid phase separation of secondary organic aerosol, but an organic shell phase did not prevent oxidation of HONO to HNO 3 . This rapid conversion of HONO to HNO 3 at the droplet interface due to an acidity-based transition in the reaction mechanism could represent a significant new sink for HONO and a source of strong inorganic acids in the atmosphere that are more readily removed through deposition.

Due to its small particle size, nanoparticle (NPs) and and microparticles (&amp;#956;Ps) could reside in the air for a long time affecting human health and the environment. Understanding of its sources and dynamics in the atmosphere remains a complex challenge since direct observations are limited. Ice cores drilled from glaciers around the world contain records of atmospheric composition over time. Single particle Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (spICP-TOFMS) is uniquely capable of quickly (in ~10 minutes) measuring the estimated mass equivalent size distribution, number concentration, and elemental chemical composition (up to 70 elements excluding O, H, N, F, and the noble gases) of more than 100,000 individual insoluble mineral NPs and &amp;#956;Ps using

Ice nucleating particles (INP) capable of nucleating ice crystals via immersion freezing at temperatures above approximately -35oC may strongly influence cloud glaciation, with implications for global precipitation and climate feedback. In addition to mineral and soil dust and marine organics, laboratory and field measurements suggest biomass-burning aerosols (BBA) can act as immersion-mode INP between around -30oC and -15oC. However, the contribution of BBA to the global INP budget remains poorly understood. Large uncertainties mainly stem from poor knowledge of which fuels yield INPs and global coverage of those fuel types. Further uncertainty arises from unknown size distributions of the particles that contain minerals that act as ice nucleants. However, with some understanding of these uncertainties from sensitivity studies, the relative importance of ice nucleation activity of BBA compared to, for example, mineral dust and marine organics, can be quantified. In this work, we investigate the potential global importance of BBA as INP using a global aerosol-climate model, specifically the UK Met Office Unified Model (UM). We evaluate the model using field campaigns over four different regions. We examine potential uncertainties in particle size and fuel type on BBA-based INP concentrations. Averaged over June-September, BBA INP accounts for more than half of annual average total INP in 7% of model grid cells with temperatures between -30oC and -20oC. Our simulations suggest INP concentrations from BBA may be at least as important as mineral dust and marine INP over large regions of the atmosphere in seasons when biomass burning is frequent.

The transport efficiency of microparticles larger than ∼700 nm decreases with size. While SiO 2 particles as large as 5 µm are completely vaporized in the ICP, the ion detection system limited linear dynamic range will often require signal reduction.

The martian soil is of particular interest as it can help us understand the different processes that have occurred on Mars by studying the chemistry and mineralogy of its constituents as a function of grain size. The fine-grained martian soil is thought to be homogeneous across the planet and thus to represent a global component. In this study we report on the soil targets analysed by the SuperCam instrument aboard the Perseverance rover, which is currently exploring Jezero crater. A total of 343 targets were analysed. Their grain size distribution confirms the sparsity of 250–900 Â μ m particles in the martian soil, although both smaller and larger grains are present. We found that the local components, due to erosion of the local bedrock, are present not only in the very coarse grains or larger gravels of the soil, but also in the very fine ones (¡250 Â μ m ). We detected some very coarse grains enriched in olivine, pyroxene and carbonate in both the crater floor and the delta front locations, whereas phyllosilicate-rich grains have been encountered only in the delta front. We have compared the Jezero fine-grained soil targets with those of Gale crater using ChemCam data. We found that those at Jezero show no evidence of Mg sulfates, in contrast to the observation at Gale. In addition, the fine-grained soil at Jezero is more hydrated than that at Gale, probably due to its higher specific surface area .

High Resolution Image Download MS PowerPoint Slide Carbon-based adsorbents used to remove recalcitrant water contaminants, including perfluoroalkyl substances (PFAS), are often regenerated using energy-intensive treatments that can form harmful byproducts. We explore mechanisms for sorbent regeneration using hydrated electrons (e aq – ) from sulfite ultraviolet photolysis (UV/sulfite) in water. We studied the UV/sulfite treatment on three carbon-based sorbents with varying material properties: granular activated carbon (GAC), carbon nanotubes (CNTs), and polyethylenimine-modified lignin (lignin). Reaction rates and defluorination of dissolved and adsorbed model perfluorocarboxylic acids (PFCAs), perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA), were measured. Monochloroacetic acid (MCAA) was employed to empirically quantify e aq – formation rates in heterogeneous suspensions. Results show that dissolved PFCAs react rapidly compared to adsorbed ones. Carbon particles in solution decreased aqueous reaction rates by inducing light attenuation, e aq – scavenging, and sulfite consumption. The magnitude of these effects depended on adsorbent properties and surface chemistry. GAC lowered PFOA destruction due to strong adsorption. CNT and lignin suspensions decreased e aq – formation rates by attenuating light. Lignin showed high e aq – quenching, likely due to its oxygenated functional groups. These results indicate that desorbing PFAS and separating the adsorbent before initiating PFAS degradation reactions will be the best engineering approach for adsorbent regeneration using UV/sulfite.

Pollution by chemicals and waste impacts human and ecosystem health on regional, national, and global scales, resulting, together with climate change and biodiversity loss, in a triple planetary crisis. Consequently, in 2022, countries agreed to establish an intergovernmental science-policy panel (SPP) on chemicals, waste, and pollution prevention, complementary to the existing intergovernmental science-policy bodies on climate change and biodiversity. To ensure the SPP's success, it is imperative to protect it from conflicts of interest (COI). Here, we (i) define and review the implications of COI, and its relevance for the management of chemicals, waste, and pollution; (ii) summarize established tactics to manufacture doubt in favor of vested interests, i.e., to counter scientific evidence and/or to promote misleading narratives favorable to financial interests; and (iii) illustrate these with selected examples. This analysis leads to a review of arguments for and against chemical industry representation in the SPP's work. We further (iv) rebut an assertion voiced by some that the chemical industry should be directly involved in the panel's work because it possesses data on chemicals essential for the panel's activities. Finally, (v) we present steps that should be taken to prevent the detrimental impacts of COI in the work of the SPP. In particular, we propose to include an independent auditor's role in the SPP to ensure that participation and processes follow clear COI rules. Among others, the auditor should evaluate the content of the assessments produced to ensure unbiased representation of information that underpins the SPP's activities.

Abstract The science of mountainous hydrology spans the atmosphere through the bedrock and inherently crosses physical and disciplinary boundaries: land–atmosphere interactions in complex terrain enhance clouds and precipitation, while watersheds retain and release water over a large range of spatial and temporal scales. Limited observations in complex terrain challenge efforts to improve predictive models of the hydrology in the face of rapid changes. The Upper Colorado River exemplifies these challenges, especially with ongoing mismatches between precipitation, snowpack, and discharge. Consequently, the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) user facility has deployed an observatory to the East River Watershed near Crested Butte, Colorado, between September 2021 and June 2023 to measure the main atmospheric drivers of water resources, including precipitation, clouds, winds, aerosols, radiation, temperature, and humidity. This effort, called the Surface Atmosphere Integrated Field Laboratory (SAIL), is also working in tandem with DOE-sponsored surface and subsurface hydrologists and other federal, state, and local partners. SAIL data can be benchmarks for model development by producing a wide range of observational information on precipitation and its associated processes, including those processes that impact snowpack sublimation and redistribution, aerosol direct radiative effects in the atmosphere and in the snowpack, aerosol impacts on clouds and precipitation, and processes controlling surface fluxes of energy and mass. Preliminary data from SAIL’s first year showcase the rich information content in SAIL’s many datastreams and support testing hypotheses that will ultimately improve scientific understanding and predictability of Upper Colorado River hydrology in 2023 and beyond.

Older adults suffer more frequent and worse outcomes from sepsis, a critical illness secondary to infection. The reasons underlying this unique susceptibility are incompletely understood. Prior work in this area has focused on how the immune response changes with age. The current study, however, focuses instead on alterations in the community of bacteria that humans live with within their gut (i.e., the gut microbiome). The central concept of this paper is that the bacteria in our gut evolve along with the host and "age," making them more efficient at causing sepsis.

Prior research has focused on host factors as mediators of exaggerated sepsis-associated morbidity and mortality in older adults. This focus on the host, however, has failed to identify therapies that improve sepsis outcomes in the elderly. We hypothesized that the increased susceptibility of the aging population to sepsis is not only a function of the host, but also reflects longevity-associated changes in the virulence of gut pathobionts. We utilized two complementary models of gut microbiota-induced experimental sepsis to establish the aged gut microbiome as a key pathophysiologic driver of heightened disease severity. Further murine and human investigations into these polymicrobial bacterial communities demonstrated that age was associated with only subtle shifts in ecological composition, but an overabundance of genomic virulence factors that have functional consequence on host immune evasion. One Sentence Summary: The severity of sepsis in the aged host is in part mediated by longevity-associated increases in gut microbial virulence.

the hydrated electron is a promising technology for PFAS remediation and has been well-studied. However, since previous work rarely reports fluorine atom balances and often relies on suspect screening, some transformation products are likely unaccounted for. Therefore, we performed non-target analysis using high-resolution mass spectrometry on solutions of perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate (PFBS), perfluorooctanoate (PFOA), and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate (GenX) that had been treated with UV/sulfite to produce hydrated electrons. We determined fluorine atom balances for all compounds studied, finding high fluorine atom balances for PFOS and PFBS. PFOA and GenX had lower overall fluorine atom balances, likely due to the production of volatile or very polar transformation products that were not measured by our methods. Transformation products identified by our analysis were consistent with literature, with a few exceptions. Namely, shorter-chain perfluorosulfonates (PFSA) and their H/F substituted counterparts were also detected from PFOS. This is an unexpected result based on literature, as no documented pathway exists for the formation of shorter-chain PFSA during UV/sulfite treatment. Furthermore, the nontarget approach we employed allowed for identification of novel, unsaturated products from the hydrated electron treatment of perfluorooctanesulfonate (PFOS) that warrant further investigation.

International audience