Formaldehyde (CH2O), a key atmospheric oxidation intermediate that is detectable from satellite‐based UV/visible spectrometers, is primarily formed when hydroxyl radical (OH) reacts with volatile ...organic compounds (VOC) and is removed by photolysis, reaction with OH or deposition. We investigate the influence of OH and VOC variability on the CH2O column using a steady state model and the WRF‐Chem regional chemical transport model over the southeast United States for the summer of 2012 (June–August). The steady state model indicates that the CH2O column primarily depends on OH production rates (POH) at low concentrations of OH (<3 × 106 molecules cm−3), on both POH and VOC reactivity (VOCR: ΣikiVOCi) at moderate concentrations of OH (3 × 106–7 × 106 molecules cm−3) and on VOCR at high concentrations of OH (>7 × 106 molecules cm−3). When constrained with WRF‐Chem values of boundary layer average POH and VOCR, the steady state model of CH2O explains most of the daily (r2 = 0.93) and average June–August (r2 = 0.97) spatial variance of the fully simulated cloud‐free CH2O column. These findings imply that measurements of the CH2O column offer the potential to better understand the processes affecting oxidation, particularly in remote regions, where OH concentrations are low. The findings also suggest that the inference of VOC emissions based on measurements of CH2O, or any other intermediate oxidation species with a photolytic lifetime that is short relative to removal by reaction with OH (e.g., glyoxal), should carefully account for the influence of OH on the observed pattern, especially where OH concentrations are below 5 × 106 molecules cm−3, as occurs in remote forests, where OH strongly varies, as occurs downwind of large nitrogen oxide (NOx: NO+NO2) emission sources, or where OH sources are potentially biased.
Key Points
The formaldehyde column depends on the concentrations of OH radical and volatile organic compounds
Top‐down constraints of volatile organic compound emissions should consider variations of OH radical
The influence of nitrogen oxides on the formaldehyde column includes its feedback on OH radical concentrations
Accurate estimates for North American background (NAB) ozone (O3) in surface air over the United States are needed for setting and implementing an attainable national O3 standard. These estimates ...rely on simulations with atmospheric chemistry-transport models that set North American anthropogenic emissions to zero, and to date have relied heavily on one global model. We examine NAB estimates for spring and summer 2006 with two independent global models (GEOS-Chem and GFDL AM3). We evaluate the base simulations, which include North American anthropogenic emissions, with mid-tropospheric O3 retrieved from space and ground-level O3 measurements. The models often bracket the observed values, implying value in developing a multi-model approach to estimate NAB O3. Consistent with earlier studies, the models robustly simulate the largest nation-wide NAB levels at high-altitude western U.S. sites (seasonal average maximum daily 8-h values of ∼40–50 ppb in spring and ∼25–40 ppb in summer) where it correlates with observed O3. At these sites, a 27-year GFDL AM3 simulation simulates observed O3 events above 60 ppb and indicates that year-to-year variations in NAB O3 influence their annual frequency (with NAB contributing 50–60 ppb or more during individual events). During summer over the eastern United States (EUS), when photochemical production from regional anthropogenic emissions peaks, NAB is largely uncorrelated with observed values and it is lower than at high-altitude sites (average values of ∼20–30 ppb). Four processes contribute substantially to model differences in specific regions and seasons: lightning NOx, biogenic isoprene emissions and chemistry, wildfires, and stratosphere-to-troposphere transport. Differences in the representations of these processes within the GFDL AM3 and GEOS-Chem models contribute more to uncertainty in NAB estimates, particularly in spring when NAB is highest, than the choice of horizontal resolution within a single model (GEOS-Chem). We propose that future efforts seek to constrain these processes with targeted analysis of multi-model simulations evaluated with observations of O3 and related species from multiple platforms, and thereby reduce the error on NAB estimates needed for air quality planning.
•North American Background (NAB) surface O3 provided by two independent global models.•Models often bracket observations implying, value in multi-model approach.•NAB is highest at high-altitude sites in spring where it correlates with total O3.•NAB is lowest over the Eastern U.S. in summer where it generally does not correlate with total O3.•Largest model differences in NAB due to stratosphere, wildfires, lightning, isoprene.
•CIRT is a good option for retreatment of inoperable recurrent salivary gland tumors.•GTV volume of retreated tumors might significantly influence local control.•For the future we aim to further ...escalate the CIRT retreatment dose.•Our data might be of interest for other particle therapy facilities in operation.
To report oncologic and functional outcomes in terms of tumor control and toxicity of carbon ion radiotherapy (CIRT) in reirradiation setting for recurrent salivary gland tumors at CNAO.
From November 2013 to September 2016, 51 consecutive patients with inoperable recurrent salivary gland tumors were retreated with CIRT in the frame of the phase II protocol CNAO S14/2012C for recurrent head and neck tumors.
Majority of pts (74.5%) had adenoid cystic carcinoma, mainly rcT4a (51%) and rcT4b (37%). Median dose of prior photon based radiotherapy was 60 Gy. Median dose of CIRT was 60 Gy RBE at a mean of 3 Gy RBE per fraction. During reirradiation, 19 patients (37.3%) experienced grade G1 toxicity, 19 pts (37.3%) had G2 and 2 pts (3.9%) had G3. Median follow up time was 19 months. Twenty one (41.2%) patients had stable disease and 30 (58.8%) tumor progression at the time of last follow up. Furthermore, 9 (18%) patients had G1 late toxicity, 19 (37%) had G2 and 9 (17. 5%) had G3. Using the Kaplan Meier method, progression free survival (actuarial) at one and two years were 71.7% and 52.2% respectively. Estimated overall survival (actuarial) at one and two years were 90.2% and 64%, respectively.
CIRT is a good option for retreatment of inoperable recurrent salivary gland tumors with acceptable rates of acute and late toxicity. Longer follow up time is needed to assess the effectiveness of CIRT in reirradiation setting of salivary gland tumors.
Purpose
To define the role of Enneking staging system and of the consequent different treatment options on the outcome of osteoblastoma (OBL) of the spine.
Methods
A retrospective review of 51 ...patients with OBL of the mobile spine conducted to compare the outcomes among the different types of treatments at long term follow-up (25–229 months, av.90). These 51 patients were previously staged according to Enneking staging system and treatment selected accordingly. 10 stage two (st.2) OBLs were treated with intralesional excision and 41 stage three (st.3) OBLs were treated either by intralesional excision or en bloc resection. The intralesional excision group was divided considering the use or not of radiation therapy after surgery. The recurrence rate was compared among these groups and also considering previous open surgery (“non intact” vs. “intact”). The statistical significance was defined using the Fisher Exact test.
Results
No local recurrence occurred in the st.2 patients treated by intralesional excision. Considering the st.3 patients, 2 local recurrences out of 13 patients occurred in the en bloc resection (15.4 %) group. All occurred in “non intact” cases (67 %). In the intralesional group, 5 local recurrences out of 27 patients occurred (18 %) being none in the group that received radiation therapy after surgery. Two occurred in the “intact” (7 %) and three in the “non intact” group (75 %). Considering all patients, the difference between the recurrence rate between “intact” and “non intact” groups was statistically significant (
p
< 0.002).
Conclusions
Intralesional excision proved to be effective in st.2 lesions and en bloc resection in st.3. Radiotherapy seems to be an effective adjuvant treatment when en bloc resection is not feasible or requires unacceptable functional sacrifices. The first treatment significantly affects the prognosis as previously treated patients have worse prognosis.
Ground level ozone concentrations (O₃) typically show a direct linear relationship with surface air temperature. Three decades of California measurements provide evidence of a statistically ...significant change in the ozone-temperature slope (Δm O3-T ) under extremely high temperatures (>312 K). This Δm O3-T leads to a plateau or decrease in O₃, reflecting the diminished role of nitrogen oxide sequestration by peroxyacetyl nitrates and reduced biogenic isoprene emissions at high temperatures. Despite inclusion of these processes in global and regional chemistry-climate models, a statistically significant change in Δm O3-T has not been noted in prior studies. Future climate projections suggest a more frequent and spatially widespread occurrence of this Δm O3-T response, confounding predictions of extreme ozone events based on the historically observed linear relationship.
Objective To test the hypothesis that preterm infants randomized to a low vs high O2 saturation target range have a higher incidence of intermittent hypoxemia. Study design A subcohort of 115 preterm ...infants with high resolution pulse oximetry enrolled in the Surfactant, Positive Pressure, and Oxygenation Randomized Trial were randomized to low (85%-89%) or high (91%-95%) O2 saturation target ranges. Oxygen saturation was monitored until 36 weeks postmenstrual age or until the infant was breathing room air without respiratory support for ≥72 hours. Results The low target O2 saturation group had a higher rate of intermittent hypoxemia (≤80% for ≥10 seconds and ≤3 minutes) prior to 12 days and beyond 57 days of life ( P < .05). The duration shortened ( P < .0001) and the severity increased ( P < .0001) with increasing postnatal age with no differences between target saturation groups. The higher rate of intermittent hypoxemia events in the low target group was associated with a time interval between events of <1 minute. Conclusion A low O2 saturation target was associated with an increased rate of intermittent hypoxemia events that was dependent on postnatal age. The duration and severity of events was comparable between target groups. Further investigation is needed to assess the role of intermittent hypoxemia and their timing on neonatal morbidity.
Over the eastern United States (EUS), nitrogen oxides (NOx) emission controls have led to improved air quality over the past two decades, but concerns have been raised that climate warming may offset ...some of these gains. Here we analyze the effect of changing emissions and climate, in isolation and combination, on EUS summertime surface ozone (O3) over the recent past and the 21st century in an ensemble of simulations performed with the Geophysical Fluid Dynamics Laboratory CM3 chemistry‐climate model. The simulated summertime EUS O3 is biased high but captures the structure of observed changes in regional O3 distributions following NOx emission reductions. We introduce a statistical bias correction, which allows derivation of policy‐relevant statistics by assuming a stationary mean state bias in the model, but accurate simulation of changes at each quantile of the distribution. We contrast two different 21st century scenarios: (i) representative concentration pathway (RCP) 4.5 and (ii) simulations with well‐mixed greenhouse gases (WMGG) following RCP4.5 but with emissions of air pollutants and precursors held fixed at 2005 levels (RCP4.5_WMGG). We find under RCP4.5 no exceedance of maximum daily 8 hour average ozone above 75 ppb by mid‐21st century, reflecting the U.S. NOx emissions reductions projected in RCP4.5, while more than half of the EUS exceeds this level by the end of the 21st century under RCP4.5_WMGG. Further, we find a simple relationship between the changes in estimated 1 year return levels and regional NOx emission changes, implying that our results can be generalized to estimate changes in the frequency of EUS pollution events under different regional NOx emission scenarios.
Key Points
Ensemble simulations to attribute O3 response to changing emissions and climate
Bias‐correction to derive policy‐relevant metrics from biased models
Emission reductions can offset climate penalty on Eastern US surface O3
Changing emissions can alter the surface O3 seasonal cycle, as detected from northeastern U.S. (NE) observations during recent decades. Under continued regional precursor emission controls (>80% ...decreases in NE NOx by 2100), the NE surface O3 seasonal cycle reverses (to a winter maximum) in 21st century transient chemistry‐climate simulations. Over polluted regions, regional NOx largely controls the shape of surface O3 seasonal cycles. In the absence of regional NOx controls, climate warming contributes to a higher surface O3 summertime peak over the NE. A doubling of the global CH4 abundance by 2100 partially offsets summertime surface O3 decreases attained via NOx reductions and contributes to raising surface O3 during December–March when the O3 lifetime is longer. The similarity between surface O3 seasonal cycles over the NE and the Intermountain West by 2100 indicates a NE transition to a region representative of baseline surface O3 conditions.
Key Points
Changing regional NOx emissions alter peak surface ozone seasonClimate change increases peak summertime surface ozone over NE U.S.Rising global methane enhances surface ozone most strongly during winter
The ozone (O3) dry depositional sink and its contribution to observed variability in tropospheric O3 are both poorly understood. Distinguishing O3 uptake through plant stomata versus other pathways ...is relevant for quantifying the O3 influence on carbon and water cycles. We use a decade of O3, carbon, and energy eddy covariance (EC) fluxes at Harvard Forest to investigate interannual variability (IAV) in O3 deposition velocities (
vd,O3). In each month, monthly mean
vd,O3 for the highest year is twice that for the lowest. Two independent stomatal conductance estimates, based on either water vapor EC or gross primary productivity, vary little from year to year relative to canopy conductance. We conclude that nonstomatal deposition controls the substantial observed IAV in summertime
vd,O3 during the 1990s over this deciduous forest. The absence of obvious relationships between meteorology and
vd,O3 implies a need for additional long‐term, high‐quality measurements and further investigation of nonstomatal mechanisms.
Key Points
Observed factor of 2 in interannual variability (IAV) of ozone dry deposition velocities, dominated by nonstomatal processes
Stomatal conductance estimates from two observation‐driven independent models show similar but weak IAV
High‐quality, long‐term measurements needed to identify processes driving IAV in ozone dry deposition
PDF
