Direct Analysis of Trace Contaminants on Indoor Surfaces and their Loss via Reaction with Hydroxyl Radicals

It is well known that semivolatile organic compounds (SVOCs) are persistent indoors and can sorb onto surfaces creating organic films. Most previous studies on indoor chemistry have focused on gas-phase and surface oxidation reactions with ozone. However, several studies have measured and reported gas-phase OH radical concentrations in indoor environments. This work focuses on the heterogeneous surface chemistry that occurs when compounds ubiquitously found indoors, such as palmitic acid (PA) or di-n-octyl phthalate (DnOP, a plasticizer) sorb onto indoor surfaces. In this study, we find that these compounds are subject to heterogeneous OH oxidation, challenging the idea that they persist indefinitely. Lifetimes of pure PA and DnOP samples are 18.5 and 6.0 days, respectively at an assumed [OH] value of 5x105 molec cm-3. Organic films developed in genuine indoor environments contain several species that are also subject to heterogeneous OH oxidation, with lifetimes varying from one week to several months.M.Sc.2019-01-11 00:00:0

Stability and Biodistribution of Thiol-Functionalized and ¹⁷⁷Lu-Labeled Metal Chelating Polymers Bound to Gold Nanoparticles

We are studying a novel radiation nanomedicine approach to treatment of breast cancer using 30 nm gold nanoparticles (AuNP) modified with polyethylene glycol (PEG) metal-chelating polymers (MCP) that incorporate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators for complexing the β-particle emitter, ¹⁷⁷Lu. Our objective was to compare the stability of AuNP conjugated to MCP via a single thiol [DOTA-PEG-ortho-pyridyl disulfide (OPSS)], a dithiol [DOTA-PEG-lipoic acid (LA)] or multithiol end-group [PEG-<i>p</i>Glu­(DOTA)₈-LA₄] and determine the elimination and biodistribution of these ¹⁷⁷Lu-labeled MCP-AuNP in mice. Stability to aggregation in the presence of thiol-containing dithiothreitol (DTT), l-cysteine or glutathione was assessed and dissociation of ¹⁷⁷Lu-MCP from AuNP in human plasma measured. Elimination of radioactivity from the body of athymic mice and excretion into the urine and feces was measured up to 168 h post-intravenous (i.v.) injection of ¹⁷⁷Lu-MCP-AuNP and normal tissue uptake was determined. ICP-AES was used to quantify Au in the liver and spleen and these were compared to ¹⁷⁷Lu. Our results showed that PEG-<i>p</i>Glu­(DOTA)₈-LA_4‑AuNP were more stable to aggregation in vitro than DOTA-PEG-LA-AuNP and both forms of AuNP were more stable to thiol challenge than DOTA-PEG-OPSS-AuNP. PEG-<i>p</i>Glu­(¹⁷⁷Lu-DOTA)₈-LA₄ was the most stable in plasma. Whole body elimination of ¹⁷⁷Lu was most rapid for mice injected with ¹⁷⁷Lu-DOTA-PEG-OPSS-AuNP. Urinary excretion accounted for >90% of eliminated ¹⁷⁷Lu. All ¹⁷⁷Lu-MCP-AuNP accumulated in the liver and spleen. Liver uptake was lowest for PEG-<i>p</i>Glu­(¹⁷⁷Lu-DOTA)₈-LA₄-AuNP but these AuNP exhibited the greatest spleen uptake. There were differences in Au and ¹⁷⁷Lu in the liver for PEG-<i>p</i>Glu­(¹⁷⁷Lu-DOTA)₈-LA₄-AuNP. These differences were not correlated with in vitro stability of the ¹⁷⁷Lu-MCP-AuNP. We conclude that conjugation of AuNP with PEG-<i>p</i>Glu­(¹⁷⁷Lu-DOTA)₈-LA₄ via a multithiol functional group provided the greatest stability in vitro and lowest liver uptake in vivo and is, therefore, the most promising for constructing ¹⁷⁷Lu-MCP-AuNP for radiation treatment of breast cancer

Total ozone loss during the 2021/22 Arctic winter and comparison to previous years

International audienceThe amplitude and rate of ozone depletion in the Arctic is monitored every year since 1994 by comparison between SAOZ UV-Vis ground-based network from NDACC and Multi-Sensor Reanalysis 2 (MSR-2) total ozone measurements over 8 stations in the Arctic and 3-D chemical transport model simulations in which ozone is considered as a passive tracer. The passive ozone method allows determining the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relatively warm and short vortex duration years to 25-38% in colder and longer ones, which the record winters estimated in 2010/2011 and 2019/2020.In this study, the interannual variability of 10-days average rate of 2021/2022 winter will be analyzed and compared to previous years. In addition, SAOZ NO2 data will be used to evaluate re- noxification in the Arctic. The long-term ozone loss series estimated from measurements will be compared to REPROBUS and SLIMCAT CTM simulations. Relationship with illuminated Polar Stratospheric Clouds will be also presented

Tropospheric and Surface Nitrogen Dioxide Changes in the Greater Toronto Area during the First Two Years of the COVID-19 Pandemic

We present tropospheric nitrogen dioxide (NO2) changes observed by the Canadian Pandora measurement program in the Greater Toronto Area (GTA), Canada, and compare the results with surface NO2 concentrations measured via in situ instruments to assess the local emission changes during the first two years of the COVID-19 pandemic. In the City of Toronto, the first lockdown period started on 15 March 2020, and continued until 24 June 2020. ECMWF Reanalysis v5 (ERA-5) wind information was used to facilitate the data analysis and reveal detailed local emission changes from different areas of the City of Toronto. Evaluating seven years of Pandora observations, a clear NO2 reduction was found, especially from the more polluted downtown Toronto and airport areas (e.g., declined by 35% to 40% in 2020 compared to the 5-year mean value from these areas) during the first two years of the pandemic. Compared to the sharp decline in NO2 emissions in 2020, the atmospheric NO2 levels in 2021 started to recover, but are still below the mean values in pre-pandemic time. For some sites, the pre-pandemic NO2 local morning rush hour peak has still not returned in 2021, indicating a change in local traffic and commuter patterns. The long-term (12 years) surface air quality record shows a statistically significant decline in NO2 with and without April to September 2020 observations (trend of &minus;4.1%/yr and &minus;3.9%/yr, respectively). Even considering this long-term negative trend in NO2, the observed NO2 reduction (from both Pandora and in situ) in the early stage of the pandemic is still statistically significant. By implementing the new wind-based validation method, the high-resolution satellite instrument (TROPOMI) can also capture the local NO2 emission pattern changes to a good level of agreement with the ground-based observations. The bias between ground-based and satellite observations during the pandemic was found to have a positive shift (5&ndash;12%) than the bias during the pre-pandemic period

Record springtime stratospheric ozone depletion at 80°N in 2020

International audienceThe Arctic winter of 2019-2020 was characterized by an unusually persistent polar vortex and temperatures in the lower stratosphere that were consistently below the threshold for the formation of polar stratospheric clouds (PSCs). These conditions led to ozone loss that is comparable to the Antarctic ozone hole. Ground-based measurements from a suite of instruments at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Canada (80.05°N, 86.42°W) were used to investigate chemical ozone depletion. The vortex was located above Eureka longer than in any previous year in the 20-year dataset and lidar measurements provided evidence of polar stratospheric clouds (PSCs) above Eureka. Additionally, UV-visible zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements showed record ozone loss in the 20-year dataset, evidence of denitrification along with the slowest increase of NO2 during spring, as well as enhanced reactive halogen species (OClO and BrO). Complementary measurements of HCl and ClONO2 (chlorine reservoir species) from a Fourier transform infrared (FTIR) spectrometer showed unusually low columns that were comparable to 2011, the previous year with significant chemical ozone depletion. Record low values of HNO3 in the FTIR dataset are in accordance with the evidence of PSCs and a denitrified atmosphere. Estimates of chemical ozone loss were derived using passive ozone from the SLIMCAT offline chemical transport model to account for dynamical contributions to the stratospheric ozone budget

Unprecedented spring 2020 ozone depletion in the context of 20 years of measurements at Eureka, Canada

International audienceIn the winter and spring of 2019/2020, the unusually cold, strong, and stable polar vortex created favorable conditions for ozone depletion in the Arctic. Chemical ozone loss started earlier than in any previous year in the satellite era, and continued until late March, resulting in the unprecedented reduction of the ozone column. The vortex was located above the Polar Environment Atmospheric Research Laboratory in Eureka, Canada (80°N, 86°W) from late February to the end of April, presenting an excellent opportunity to examine ozone loss from a single ground station.Measurements from a suite of instruments show that total column ozone was at an all‐time low in the 20‐year dataset, 22‐102 DU below previous records set in 2011. Ozone minima ( < 200 DU), enhanced OClO and BrO slant columns, and unusually low HCl, ClONO2, and HNO3 columns were observed in March. Polar stratospheric clouds were present as late as 20 March, and ozonesondes show unprecedented depletion in the March and April profiles (to < 0.2 ppmv).While both chemical and dynamical factors lead to reduced ozone when the vortex is cold, the contribution of chemical depletion (based on the variable correlation of ozone and temperature) was exceptional in spring 2020 when compared to typical Arctic winters.Mean chemical ozone loss over Eureka was estimated to be 111‐126 DU (27‐31%) using April measurements and passive ozone from the SLIMCAT chemical transport model. While absolute ozone loss was generally smaller in 2020 than in 2011, percentage ozone loss was greater in 2020