Molecular and physical characteristics of aerosol at a remote free troposphere site: implications for atmospheric aging

Aerosol properties are transformed by atmospheric processes during long-range transport and play a key role in the Earth's radiative balance. To understand the molecular and physical characteristics of free tropospheric aerosol, we studied samples collected at the Pico Mountain Observatory in the North Atlantic. The observatory is located in the marine free troposphere at 2225&thinsp;m above sea level, on Pico Island in the Azores archipelago. The site is ideal for the study of long-range-transported free tropospheric aerosol with minimal local influence. Three aerosol samples with elevated organic carbon concentrations were selected for detailed analysis. FLEXPART retroplumes indicated that two of the samples were influenced by North American wildfire emissions transported in the free troposphere and one by North American outflow mainly transported within the marine boundary layer. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry was used to determine the detailed molecular composition of the samples. Thousands of molecular formulas were assigned to each of the individual samples. On average  ∼ 60&thinsp;% of the molecular formulas contained only carbon, hydrogen, and oxygen atoms (CHO),  ∼ 30&thinsp;% contained nitrogen (CHNO), and  ∼ 10&thinsp;% contained sulfur (CHOS). The molecular formula compositions of the two wildfire-influenced aerosol samples transported mainly in the free troposphere had relatively low average O∕C ratios (0.48±0.13 and 0.45±0.11) despite the 7–10 days of transport time according to FLEXPART. In contrast, the molecular composition of the North American outflow transported mainly in the boundary layer had a higher average O∕C ratio (0.57±0.17) with 3 days of transport time. To better understand the difference between free tropospheric transport and boundary layer transport, the meteorological conditions along the FLEXPART simulated transport pathways were extracted from the Global Forecast System analysis for the model grids. We used the extracted meteorological conditions and the observed molecular chemistry to predict the relative-humidity-dependent glass transition temperatures (Tg) of the aerosol components. Comparisons of the Tg to the ambient temperature indicated that a majority of the organic aerosol components transported in the free troposphere were more viscous and therefore less susceptible to oxidation than the organic aerosol components transported in the boundary layer. Although the number of observations is limited, the results suggest that biomass burning organic aerosol injected into the free troposphere is more persistent than organic aerosol in the boundary layer having broader implications for aerosol aging.</p

Evaluation of organic markers for chemical mass balance source apportionment at the Fresno Supersite

International audienceSources of PM2.5 at the Fresno Supersite during high PM2.5 episodes occurring from 15 December 2000?3 February 2001 were estimated with the Chemical Mass Balance (CMB) receptor model. The ability of source profiles with organic markers to distinguish motor vehicle, residential wood combustion (RWC), and cooking emissions was evaluated with simulated data. Organics improved the distinction between gasoline and diesel vehicle emissions and allowed a more precise estimate of the cooking source contribution. Sensitivity tests using average ambient concentrations showed that the gasoline vehicle contribution was not resolved without organics. Organics were not required to estimate hardwood contributions. The most important RWC marker was the water-soluble potassium ion. The estimated cooking contribution did not depend on cholesterol because its concentrations were below the detection limit in most samples. Winter time source contributions were estimated by applying the CMB model to individual and average sample concentrations. RWC was the largest source, contributing 29?31% of measured PM2.5. Hardwood and softwood combustion accounted for 16?17% and 12?15%, respectively. Secondary ammonium nitrate and motor vehicle emissions accounted for 31?33% and 9?15%, respectively. The gasoline vehicle contribution (3?10%) was comparable to the diesel vehicle contribution (5?6%). The cooking contribution was 5?19% of PM2.5. Fresno source apportionment results were consistent with those estimated in previous studies

Modelling the hygroscopic growth factors of aerosol material containing a large water-soluble organic fraction, collected at the Storm Peak Laboratory

The compositions of six aggregated aerosol samples from the Storm Peak site have been comprehensively analysed (Hallar et al., 2013), focusing particularly on the large water-extractable organic fraction which consists of both high molecular weight organic compounds and a range of acids and sugar-alcohols. The contribution of the soluble organic fraction of atmospheric aerosols to their hygroscopicity is hard to quantify, largely because of the lack of a detailed knowledge of both composition and the thermodynamic properties of the functionally complex compounds and structures the fraction contains. In this work we: (i) develop a means of predicting the relative solubility of the compounds in the water-extractable organic material from the Storm Peak site, based upon what is known about their chemical composition; (ii) derive the probable soluble organic fraction from comparisons of model predictions with the measured hygroscopicity; (iii) test a model of the water uptake of the total aerosol (inorganic plus total water-extractable organic compounds). Using a novel UNIFAC-based method, different assignments of functional groups to the high molecular weight water soluble organic compounds (WSOC) were explored, together with their effects on calculated hygroscopic growth factors, constrained by the known molecular formulae and the double bond equivalents associated with each molecule. The possible group compositions were compared with the results of ultrahigh resolution mass spectrometry measurements of the organic material, which suggest large numbers of alcohol (–OH) and acid (–COOH) groups. A hygroscopicity index (HI) was developed. The measured hygroscopic growth is found to be consistent with a dissolution of the WSOC material that varies approximately linearly with RH, such that the dissolved fraction is about 0.45–0.85 at 90% relative humidity when ordering by HI, depending on the assumptions made. This relationship, if it also applies to other types of organic aerosol material, provides a simple approach to calculating both water uptake and CCN activity (and the κ parameter for hygroscopic growth). The hygroscopicity of the total aerosol was modelled using a modified Zdanovskii-Stokes-Robinson approach as the sum of that of the three analysed fractions: inorganic ions (predicted), individual organic acids and “sugar alcohols” (predicted), and the high molecular weight WSOC fraction (measured). The calculated growth factors broadly agree with the measurements, and validate the approach taken. The insights into the dissolution of the organic material seem likely to apply to other largely biogenic aerosols from similar remote locations

Former Foodstuff Products (FFPs) as Circular Feed: Types of Packaging Remnants and Methods for Their Detection

Alternative feed ingredients in farm animal diets are a sustainable option from several perspectives. Former food products (FFPs) provide an interesting case study, as they represent a way of converting food industry losses into ingredients for the feed industry. A key concern regarding FFPs is the possible packaging residues that can become part of the product, leading to potential contamination of the feed. Although the level of contamination has been reported as negligible, to ensure a good risk evaluation and assessment of the presence of packaging remnants in FFPs, several techniques have been proposed or are currently being studied, of which the main ones are summarized in this review. Accordingly visual inspections, computer vision (CV), multivariate image analysis (MIA), and electric nose (e-nose) are discussed. All the proposed methods work mainly by providing qualitative results, while further research is needed to quantify FFP-derived packaging remnants in feed and to evaluate feed safety as required by the food industries

Human iPSC-Derived 3D Hepatic Organoids in a Miniaturized Dynamic Culture System

The process of identifying and approving a new drug is a time-consuming and expensive procedure. One of the biggest issues to overcome is the risk of hepatotoxicity, which is one of the main reasons for drug withdrawal from the market. While animal models are the gold standard in preclinical drug testing, the translation of results into therapeutic intervention is often ambiguous due to interspecies differences in hepatic metabolism. The discovery of human induced pluripotent stem cells (hiPSCs) and their derivatives has opened new possibilities for drug testing. We used mesenchymal stem cells and hepatocytes both derived from hiPSCs, together with endothelial cells, to miniaturize the process of generating hepatic organoids. These organoids were then cultivated in vitro using both static and dynamic cultures. Additionally, we tested spheroids solely composed by induced hepatocytes. By miniaturizing the system, we demonstrated the possibility of maintaining the organoids, but not the spheroids, in culture for up to 1 week. This timeframe may be sufficient to carry out a hypothetical pharmacological test or screening. In conclusion, we propose that the hiPSCderived liver organoid model could complement or, in the near future, replace the pharmacological and toxicological tests conducted on animals

Green Tattoo Pre-Operative Renal Embolization for Robotic-Assisted and Laparoscopic Partial Nephrectomy: A Practical Proof of a New Technique

Background: Our aim is to describe a new mixed indocyanine-non-adhesive liquid embolic agent (Onyx-18) pre-operative renal embolization technique for assisted-robotic and laparoscopic partial nephrectomy with near-infra-red fluorescence imaging. (2) Methods: Thirteen patients with biopsy-proven renal tumors underwent pre-operative mixed indocyanine–ethylene vinyl alcohol (EVOH) embolization (Green-embo) between June 2021 and August 2022. All pre-operative embolizations were performed with a super selective stop-flow technique using a balloon microcatheter to deliver an indocyanine-EVOH mixture into tertiary order arterial branch feeders and the intra-lesional vascular supply. Efficacy (evaluated as complete embolization, correct tumor mapping on infra-red fluorescence imaging and clamp-off surgery) and safety (evaluated as complication rate and functional outcomes) were primary goals. Clinical and pathological data were also collected. (3) Results: Two male and eleven female patients (mean age 72 years) received pre-operative Green-embo. The median tumor size was 29 mm (range 15–50 mm). Histopathology identified renal cell carcinoma (RCC) in 9 of the 13 (69%) patients, oncocytoma in 3 of the 13 (23%) patients and sarcomatoid RCC in 1 of the 13 (8%) patients. Lesions were equally distributed between polar, meso-renal, endo- and exophytic locations. Complete embolization was achieved in all the procedures. A correct green mapping was identified during all infra-red fluorescence imaging. All patients were discharged on the second day after the surgery. The median blood loss was 145 cc (10–300 cc). No significant differences were observed in serum creatinine levels before and after the embolization procedures. (4) Conclusions: The Green-tattoo technique based on a mixed indocyanine-non-adhesive liquid embolic agent (Onyx-18) is a safe and effective pre-operative embolization technique. The main advantages are the excellent lesion mapping for fluorescence imaging, reduction in surgical time, and definitive, complete and immediate tumor devascularization based on the deep Onyx-18 penetration, leading to a very low intra-operative blood loss

Brown carbon in tar balls from smoldering biomass combustion

We report the direct observation of laboratory production of spherical, carbonaceous particles- tar balls -from smoldering combustion of two commonly occurring dry mid-latitude fuels. Real-time measurements of spectrally varying absorption Ångström coefficients (AAC) indicate that a class of light absorbing organic carbon (OC) with wavelength dependent imaginary part of its refractive index-optically defined as brown carbon -is an important component of tar balls. The spectrum of the imaginary parts of their complex refractive indices can be described with a Lorentzian-like model with an effective resonance wavelength in the ultraviolet (UV) spectral region. Sensitivity calculations for aerosols containing traditional OC (no absorption at visible and UV wavelengths) and brown carbon suggest that accounting for near-UV absorption by brown carbon leads to an increase in aerosol radiative forcing efficiency and increased light absorption. Since particles from smoldering combustion account for nearly three-fourths of the total carbonaceous aerosol mass emitted globally, inclusion of the optical properties of tar balls into radiative forcing models has significance for the Earth\u27s radiation budget, optical remote sensing, and understanding of anomalous UV absorption in the troposphere