Contribution of bacteria-like particles to PM2.5 aerosol in urban and rural environments

Publication date: July 2017
Source:Atmospheric Environment, Volume 160
Author(s): R. Wolf, I. El-Haddad, J.G. Slowik, K. Dällenbach, E. Bruns, J. Vasilescu, U. Baltensperger, A.S.H. Prévôt
We report highly time-resolved estimates of airborne bacteria-like particle concentrations in ambient aerosol using an Aerodyne aerosol mass spectrometer (AMS). AMS measurements with a newly developed PM2.5 and the standard (PM1) aerodynamic lens were performed at an urban background site (Zurich) and at a rural site (Payerne) in Switzerland. Positive matrix factorization using the multilinear engine (ME-2) implementation was used to estimate the contribution of bacteria-like particles to non-refractory organic aerosol. The success of the method was evaluated by a size-resolved analysis of the organic mass and the analysis of single particle mass spectra, which were detected with a light scattering system integrated into the AMS. Use of the PM2.5 aerodynamic lens increased measured bacteria-like concentrations, supporting the analysis method. However, at all sites, the low concentrations of this component suggest that airborne bacteria constitute a minor fraction of non-refractory PM2.5 organic aerosol mass. Estimated average mass concentrations were below 0.1 μg/m³ and relative contributions were lower than 2% at both sites. During rainfall periods, concentrations of the bacteria-like component increased considerably reaching a short-time maximum of approximately 2 μg/m³ at the Payerne site in summer.



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Selection of suitable wavelengths for estimating total ozone column with multifilter UV radiometers

Publication date: July 2017
Source:Atmospheric Environment, Volume 160
Author(s): A.A. Piedehierro, M.L. Cancillo, A. Serrano, M. Antón, J.M. Vilaplana
The complete recovery of the ozone layer is expected by mid-century but projections depend on the greenhouse scenario and the possible interaction with other atmospheric constituents. Therefore, enlarging the ground-based measuring network is necessary in order to accurately monitor the foreseeable recovery of the ozone layer in the next decades. Multifilter instruments can be used to complement the networks of Dobson and Brewer spectroradiometers. Total ozone column (TOC) can be retrieved from spectral or narrowband global ultraviolet (UV) measurements by comparing the ratio of two close wavelengths with significantly different ozone cross-sections against ratios simulated using a radiative transfer code. This methodology has been widely applied to multifilter radiometers but some unsolved discrepancies between the analyses of different authors regarding which pair of channels to use still remain, even for studies involving the same instrument. The present work aims to analyze TOC estimations derived using different pairs of wavelengths in the UV range (spectral and weighted by the filter response) as it would be recorded by the two main families of multifilter instruments (NILU-UV and GUV). Their spectral responses have been used for determining the response-weighted quantities from Brewer spectra. Validation against TOC values retrieved from direct solar measurements by a reference Brewer spectroradiometer shows that 340:305 wavelengths/channels result in the most accurate TOC estimations. According to our results, TOC values retrieved using response-weighted irradiance are more robust than those obtained using spectral irradiances at certain nominal wavelengths. This finding suggests calibrating multifilter radiometers towards the accurate measurement of response-weighted irradiances, being necessary to characterize the spectral response of each channel.



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Impact of partitioning and oxidative processing of PAH in fogs and clouds on atmospheric lifetimes of PAH

Publication date: July 2017
Source:Atmospheric Environment, Volume 160
Author(s): Jershon Dale Eagar, Barbara Ervens, Pierre Herckes
The importance of the atmospheric aqueous phase of fogs and clouds, for the processing and removal of polycyclic aromatic hydrocarbons (PAHs) is not well known. A multiphase model was developed to determine the fate and lifetime of PAHs in fogs and clouds for a limited set of daytime conditions. The model describes partitioning between three phases (aqueous, liquid organic, and gas), experimental and estimated (photo)oxidation rates. Using a limited set of microphysical and chemical input conditions, the loss rates of PAHs in the complex three-phase system are explored.At 25 °C, PAHs with two, three and four rings are predicted to be primarily in the gas phase (fraction in the gas phase xg > 90%) while five- and six-ring PAHs partition significantly into droplets with aqueous phase fractions of 1–6% and liquid organic phase fractions of 31–91%, respectively. The predicted atmospheric chemical lifetimes of PAHs in the presence of fog or cloud droplets (<8 h) are significantly shorter than literature predictions of PAH lifetimes due to wet and dry deposition (1–14 days and 5–15 months, respectively) and shorter than or equal to predicted lifetimes due to chemical reactions in the gas and organic particulate phases (1–300 h). Even though PAH solubilities are ≤4 × 10⁻² g L⁻¹, the results of the current study show that often the condensed phase of fog and cloud droplets cannot be neglected as a PAH sink.

Graphical abstract

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Investigation of the vertical distribution and speciation of 137Cs in soil profiles at burnt and unburnt forest sites in the Belarusian Exclusion Zone

Publication date: September 2017
Source:Journal of Environmental Radioactivity, Volumes 175–176
Author(s): M. Dowdall, Y. Bondar, L. Skipperud, V. Zabrotski, M. Nandrup Pettersen, Ø.G. Selnæs, J.E. Brown
The effects of fire events on contaminant radionuclides within soils of the Belarusian Exclusion Zone were investigated. A number of cores were taken from locations known to have been subject to fire events in the past as well as a series of cores from nearby unburnt locations. Both burnt and unburnt cores were analyzed for contaminant radionuclides as well as a range of relevant soil parameters. The distribution of ¹³⁷Cs between various fractions (reversibly bound, irreversibly bound and insoluble) was analyzed. Results indicate no evidence of enhancement or enrichment of radionuclides within the soil column although this does not negate the possibility that such effects were evident at some point in the past, the fire events at two of the sites having occurred almost ten years earlier. Evidence was present of a persistent effect on how ¹³⁷Cs was distributed between different fractions of the soil, primarily in relation to the proportions associated with oxides of Fe and Mn and organic matter. The results of the study appear to indicate that the long-term effects of a forest fire on contaminant ¹³⁷Cs within the soil column are expressed through changes in the physico-chemical forms of the nuclide to a larger extent than simple redistribution of the contaminant within the soil column.



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Left and right reaction time differences to the sound intensity in normal and AD/HD children

Publication date: June 2017
Source:International Journal of Pediatric Otorhinolaryngology, Volume 97
Author(s): Golnaz Baghdadi, Farzad Towhidkhah, Reza Rostami
ObjectivesRight hemisphere, which is attributed to the sound intensity discrimination, has abnormality in people with attention deficit/hyperactivity disorder (AD/HD). However, it is not studied whether the defect in the right hemisphere has influenced on the intensity sensation of AD/HD subjects or not. In this study, the sensitivity of normal and AD/HD children to the sound intensity was investigated.MethodsNineteen normal and fourteen AD/HD children participated in the study and performed a simple auditory reaction time task. Using the regression analysis, the sensitivity of right and left ears to various sound intensity levels was examined.ResultsThe statistical results showed that the sensitivity of AD/HD subjects to the intensity was lower than the normal group (p < 0.0001). Left and right pathways of the auditory system had the same pattern of response in AD/HD subjects (p > 0.05). However, in control group the left pathway was more sensitive to the sound intensity level than the right one (p = 0.0156).ConclusionsIt can be probable that the deficit of the right hemisphere has influenced on the auditory sensitivity of AD/HD children. The possible existent deficits of other auditory system components such as middle ear, inner ear, or involved brain stem nucleuses may also lead to the observed results. The development of new biomarkers based on the sensitivity of the brain hemispheres to the sound intensity has been suggested to estimate the risk of AD/HD. Designing new technique to correct the auditory feedback has been also proposed in behavioral treatment sessions.



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Prevention of post-operative pediatric tracheotomy wounds: A multidisciplinary team approach

Publication date: June 2017
Source:International Journal of Pediatric Otorhinolaryngology, Volume 97
Author(s): Timothy P. McEvoy, Nolan B. Seim, Abdullah Aljasser, Charles A. Elmaraghy, Brenda Ruth, Leslie Justice, Sarah Begue, Kris R. Jatana
ObjectiveTracheotomy-related pressure wounds have been reported as high as 29%. All advanced stage (stage 3 or 4) wounds are reported by hospitals, and CMS will no longer reimburse healthcare costs to manage them. We present the results of an intensive, multidisciplinary wound prevention strategy starting in the operating room at the time of tracheotomy placement.MethodsProspective analysis of a tracheostomy wound care protocol at an academic, tertiary-care pediatric hospital from September 2012 to February 2016. Participants include all patients having undergone tracheostomy placement followed by protocoled daily dressing changes until the first tracheostomy tube change by team consisting a senior level otolaryngology resident or pediatric otolaryngology fellow, certified wound care specialist, respiratory therapist, and bedside nurse.ResultsPost-operative tracheostomy-related wound data from 3 years prior to clinical intervention was obtained and compared to the intervention cohort. From March 2010–August 2012, 161 tracheotomy procedures were performed with 36 (22.4%) subsequent pressure wounds; 31% of these were stage 3 or 4 wounds. After multidisciplinary protocol implementation, there have been 121 additional tracheotomy procedures with reduction to 12 (9.9%) total tracheotomy-related wounds (p = 0.0064) and none (0%) were stage 3 or 4 (p = 0.0014). All stage 1 and 2 wounds were identified early, underwent appropriate intervention, and avoided further progression.ConclusionsThis protocol was successful in the elimination of all tracheostomy-related advanced stage, hospital-acquired pressure injuries and led to prompt identification of early stage wounds post-operatively.



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Photodynamic therapy in the management of basal cell carcinoma: Retrospective evaluation of outcome

Publication date: Available online 22 April 2017
Source:Photodiagnosis and Photodynamic Therapy
Author(s): Waseem Jerjes, Zaid Hamdoon, Colin Hopper
IntroductionPhotodynamic therapy (PDT) is a relatively new method of treating various kinds of pathologies. In this retrospective study, a total of 148 patients with basal cell carcinoma (BCC) were treated with surface illumination methyl aminolevulinate − photodynamic therapy (MAL-PDT) or meta-tetrahydroxyphenylchlorin (mTHPC-PDT). Comparisons with the clinical features, rate of recurrence and overall outcome were made.Materials and methodsSurface illumination PDT was offered under local or general anaesthesia. For thin BCCs, the 16% strength cream (MAL) was applied topically 3hours prior to tissue illumination. A single-channel 628nm diode laser was used for illumination and light was delivered at 100J/cm² per site. For thick BCCs, 0.05mg/kg mTHPC was administered intravenously prior to tissue illumination. A single-channel 652nm diode laser was used for illumination and light was delivered at 20J/cm² per site. Lesion response evaluation was carried out according to RECIST.ResultsThe MAL-PDT sub-group included 86 patients with 127 thin BCCs; 80 patients had complete response (CR) after one round of treatment. The mTHPC-PDT sub-group included 62 patients with 116 thick BCCs; 60 patients had complete response after one round of treatment. Statistically significant factors associated with complete response to MAL-PDT included superficial BCC histotype (P <0.001), ≤0.5mm tumour thickness (P <0.001) and lack of ulceration (P <0.001). While for the mTHPC-PDT sub-group, both superficial and nodular types responded significantly better than invasive type (P<0.001); the lack of ulceration was insignificant factor in achieving complete responseConclusionPDT achieved high efficacy in the treatment of basal cell carcinomas with greatly reduced morbidity and disfigurement. The technique is simple, can commonly be carried out in outpatient clinics, and is highly acceptable to patients.



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