Variation Of SO Research Articles

Constraining the sulfur dioxide degassing flux from Turrialba volcano, Costa Rica using unmanned aerial system measurements

Observed sulfur dioxide (SO2) mixing ratios onboard unmanned aerial systems (UAS) during March 11–13, 2013 are used to constrain the three-day averaged SO2 degassing flux from Turrialba volcano within a Bayesian inverse modeling framework. A mesoscale model coupled with Lagrangian stochastic particle backward trajectories is used to quantify the source-receptor relationships at very high spatial resolutions (i.e., <1km). The model shows better performance in reproducing the near-surface meteorological properties and observed SO2 variations when using a first-order closure non-local planetary boundary layer (PBL) scheme. The optimized SO2 degassing fluxes vary from 0.59±0.37 to 0.83±0.33ktd−1 depending on the PBL scheme used. These fluxes are in good agreement with ground-based gas flux measurements, and correspond to corrective scale factors of 8–12 to the posteruptive SO2 degassing rate in the AeroCom emission inventory. The maximum a posteriori solution for the SO2 flux is highly sensitive to the specification of prior and observational errors, and relatively insensitive to the SO2 loss term and temporal averaging of observations. Our results indicate relatively low degassing activity but sustained sulfur emissions from Turrialba volcano to the troposphere during March 2013. This study demonstrates the utility of low-cost small UAS platforms for volcanic gas composition and flux analysis.

Numerical Model-Based Artificial Neural Network Model and Its Application for Quantifying Impact Factors of Urban Air Quality

Knowledge of the relationship between air quality and impact factors is very important for air pollution control and urban environment management. Relationships between winter air pollutant concentrations and local meteorological parameters, synoptic-scale circulations and precipitation were investigated based on observed pollutant concentrations, high-resolution meteorological data from the Weather Research and Forecast model and gridded reanalysis data. Artificial neural network (ANN) model was developed using a combination of numerical model derived meteorological variables and variables indicating emission and circulation type variations for estimating daily SO2, NO2, and PM10 concentrations over urban Lanzhou, Northwestern China. Results indicated that the developed ANN model can satisfactorily reproduce the pollution level and their day-to-day variations, with correlation coefficients between the modeled and the observed daily SO2, NO2, and PM10 ranging from 0.71 to 0.83. The effect of four factors, i.e., synoptic-scale circulation type, local meteorological condition, pollutant emission variation, and wet removal process, on the day-to-day variations of SO2, NO2, and PM10 was quantified for winters of 2002–2007. Overall, local meteorological condition is the main factor causing the day-to-day variations of pollutant concentrations, followed by synoptic-scale circulation type, emission variation, and wet removal process. With limited data, this work provides a simple and effective method to identify the main factors causing air pollution, which could be widely used in other urban areas and regions for urban planning or air quality management purposes.

Process Contributions to Secondary Inorganic Aerosols during Typical Pollution Episodes over the Pearl River Delta Region, China

The Integrated Process Rate (IPR) analysis embedded in CAMx model was used to quantify contributions from different atmospheric processes to the formations and accumulations of ambient PM_(2.5) and the secondary inorganic aerosol (SIA) during two typical particulate pollution episodes in different seasons in the Pearl River Delta (PRD) region. Process analysis results indicated that primary fine particle emissions were the major sources of high ambient PM_(2.5) in urban areas with intensive anthropogenic activities. Aerosol process and advection transport were another two major processes contributing to the increasing PM_(2.5) and SIA over the PRD region. Regarding formation of SIA species, elevations of nitrate and ammonium at Guangzhou (urban), Heshan (rural) and Panyu (suburban) sites were largely associated with aerosol process, while those at Huizhou (urban) site were dominated by advection process, but elevated sulfate concentrations at these four sites were all dominated by advection process. The difference can be attributed to spatial variations of SO_2, NO_x and NH_3 emissions, site locations and meteorological conditions. Advection, aerosol chemistry, deposition and vertical diffusion were important pathways to remove SIA at these four sites. Within the hours with most growing PM_(2.5) concentrations, aerosol process was the most important contributor to the formation of new SIA throughout the entire planetary boundary layer.

Characteristics of Gaseous Pollutants at a Regional Background Station in Southern China

Measurements of gaseous pollutants(O3, NOx, SO2, and CO) were conducted at Dinghushan background station in southern China from January to December 2013.The levels and variations of O3, NOx, SO2, and CO were analyzed and their possible causes discussed. The annual average concentrations of O3, NOx, SO2, and CO were 24.6 ± 23.9, 12.8 ± 10.2, 4.0 ± 4.8, and 348 ± 185 ppbv, respectively. The observed levels of the gaseous pollutants are comparable to those at other background sites in China. The most obvious diurnal variation of O3 was observed in autumn, with minima in the early morning and maxima in the afternoon. The diurnal variations of SO2 showed high values during the day. The diurnal cycles of NOx showed higher values in the morning and lower values during the night. Higher CO concentrations were observed in spring followed by winter, autumn, and summer. Biomass burning, in combination with the transport of regional pollution, is an important source of CO, SO2, and NOx in spring and winter. Backward trajectories were calculated and analyzed together with corresponding pollutant concentrations. The results indicate that air masses passing over polluted areas are responsible for the high concentrations of gaseous pollutants at the Dinghushan background station.

High-resolution imaging spectroscopy of planetary atmospheres

Imaging spectroscopy at high resolution, in the infrared range, is a powerful tool for monitoring the behavior of minor species in planetary atmospheres and their evolution with latitude and longitude, season or local hour. Using the TEXES imaging spectrometer at the Infrared Telescope Facility (IRTF), this method has been applied for detecting and monitoring hydrogen peroxide and water vapor (using its proxy HDO) on Mars, then for monitoring sulfur dioxide and water (again using HDO) above the H2SO4 cloud deck (z=65km on Venus). Observations of Mars have shown that its atmosphere and climate are well reproduced by the Global Climatic Models. In contrast, strong spatio-temporal variations of SO2, observed above the Venus clouds, are not understood by the models. As a support of the forthcoming Juno space mission, a similar program has started on Jupiter to monitor its dynamics through 3-D maps of ammonia and phosphine.

Trends of air pollution in the Western Mediterranean Basin from a 13-year database: A research considering regional, suburban and urban environments in Mallorca (Balearic Islands)

This study is focused in the evolution of NO, NO2, SO2, O3 and PM10 concentrations, from 2000 to 2012, at urban, suburban and regional observatories in the Balearic Islands (Spain), an insular region in the Western Mediterranean.At urban and suburban areas, daily patterns of most pollutants are strongly linked to land-traffic emissions, being the regional background less influenced. SO2 variations, however, are mostly driven by the impact of other sources different from road traffic, including shipping emissions and power generation. Urban NOx, SO2 and PM10 concentrations exhibit a common weekly pattern, with a very slight accumulation during the weekdays and sharp decreases (15–39%) on weekends.Our long-term database displays clear decreasing NO and NO2 concentrations from 2000 onwards, prominent in the urban environment (−1.1 μg/m3 year), and moderate in suburban and regional areas (up to −0.3μg/m3 year). At urban sites, O3 behaviour (+1.0μg/m3 year) is opposite to that of NO, one of its main depletion agents. A moderate O3 increasing trend (+0.5μg/m3 year) is detected at regional background areas, whereas a modest decreasing trend occurred at the suburban background (−0.4μg/m3 year), probably caused by enhanced vehicular emissions over these areas induced by urban planning and mobility policies. Finally, substantial PM10 drops are obvious, −0.7μg/m3 year at urban and suburban areas, and −0.5μg/m3 year in the regional background. Our results link the sharpest declines to air masses from western to northern sectors, pointing to effective pollution abatement strategies at a European scale. Some additional benefits are connected to the implementation of diverse local policies.The effect of the North Atlantic Oscillation (NAO) was investigated. Negative NAO phases were related to additional air quality benefits, while positive phases mostly contributed to air degradation.

Abstract LB-165: Early detection of the therapeutic effect in tumors treated with a thermosensitive liposome (TSL) using noninvasive ultrasound and photoacoustic imaging

Abstract The ability to assess treatment response on a case-by-case basis in a non-invasive and longitudinal manner has the potential to maximize treatment success. In this work temperature sensitive liposomes (TSLs) have been combined with non-invasive high frequency ultrasound (US) and photoacoustic (PA) imaging to assess structural (cell death) and functional (oxygenation) aspects of tumor response, indicative of therapeutic effect, within a few hours post-treatment in a preclinical model. A TSL is a drug delivery vehicle designed to release its payload at mild-hyperthermic temperatures (39-42°C). The TSL passes through the systemic circulation (37°C), until it reaches a tumor undergoing localized heating (42°C), where it releases its contents rapidly, creating a high local concentration of drug within the tumor vasculature. This leads to high tumoral drug uptake and a number of functional changes within the tumor, resulting in a therapeutic response. Conventional assessment of treatment success is measured by the change in tumor volume over time, but this may not be noticeable until several days post-treatment and no further insight into the biology of the tumor response kinetics is provided. By using US and PA imaging in a non-invasive co-registered manner, structural and functional imaging surrogates of tumor response can be visualized in 3D. These images allow the observation of changes in the first few hours post-treatment and provide both an early indication of overall therapeutic effect and insight into the kinetics of the drug-tumor interaction. Here we have used a simple 2 component TSL called HaT (Heat activated cytoToxic, DPPC/Brij78, 96:4 mol%), designed to deliver doxorubicin (DOX), which has been shown to rapidly release drug at mild-hyperthermic temperatures (100% in &amp;lt;40 s), but has good drug stability at 37°C [Tagami et al. J. Control. Release 2011, 152, 303]. A murine breast cancer model (EMT-6) implanted in the footpad of mice was imaged using the VisualSonics Vevo LAZR system at time points before and after treatment with TSL and localized heating. Co-registered, 3D US and PA images were acquired using a 40 MHz centre frequency transducer. Tumor boundaries were outlined in the US images and used to construct oxygen saturation (sO2) maps of the tumor from the PA data acquired at 750/850 nm to target the endogenous absorption of oxy/deoxy-hemoglobin. Significant changes in sO2 data (p&amp;lt;0.05) were measured within the tumor over the time course studied (0, 1, 2, 5, 24, 48, 168 h), with the greatest variation between HaT-DOX and control groups being observed between 0 and 5 h. The ability to longitudinally monitor the sO2 allows for rapid feedback on functional changes within an individual tumor on much shorter time scales (&amp;lt;5 h) than conventional tumor volume measurements. Mice tumors that received HaT-DOX treatments resulted in a &amp;gt;30% decrease in sO2 within the first 5 h post-treatment and showed &amp;gt;50% tumor regression after 14 days. Furthermore, the extent of tumor regression was observed to be proportional the magnitude of this early decrease in sO2. The observed longitudinal variations in sO2 represent the unique ability of US/PA imaging to monitor structural and functional changes within tumor vasculature and can be used as a rapid, non-invasive early indicator of HaT-DOX treatment efficacy. Citation Format: Jonathan P. May, Eno Hysi, Lauren Wirtzfeld, Elijus Undzys, Michael C. Kolios, Shyh-Dar Li. Early detection of the therapeutic effect in tumors treated with a thermosensitive liposome (TSL) using noninvasive ultrasound and photoacoustic imaging. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-165. doi:10.1158/1538-7445.AM2014-LB-165

A pilot study of a new spectrophotometry device to measure tissue oxygen saturation*

Tissue oxygen saturation (SO2) measurements have the potential for far wider use than at present but are limited by device availability and portability for many potential applications. A device based on a small, low-cost general-purpose spectrophotometer (the Harrison device) might facilitate wider use. The aim of this study was to compare the Harrison device with a commercial instrument, the LEA O2C.Measurements were carried out on the forearm and finger of 20 healthy volunteers, using a blood pressure cuff on the upper arm to induce different levels of oxygenation. Repeatability of both devices was assessed, and the Bland–Altman method was used to assess agreement between them.The devices showed agreement in overall tracking of changes in SO2. Test–retest agreement for the Harrison device was worse than for O2C, with SD repeatability of 10.6% (forearm) or 18.6% (finger). There was no overall bias between devices, but mean (SD) difference of 1.2 (11.8%) (forearm) or 4.4 (11.5%) (finger) were outside of a clinically acceptable range.Disagreements were attributed to the stability of the Harrison probe and the natural SO2 variations across the skin surface increasing the random error. Therefore, though not equivalent to the LEA O2C, a probe redesign and averaged measurements may help establish the Harrison device as a low cost alternative.

SU‐E‐T‐326: The Oxygen Saturation (SO2) and Breath‐Holding Time Variation Applied Active Breathing Control (ABC)

Purpose:To study the oxygen saturation (SO2) and breath‐holding time variation applied active breathing control (ABC) in radiotherapy of tumor.Methods:24 volunteers were involved in our trials, and they all did breath‐holding motion assisted by ELEKTA Active Breathing Coordinator 2.0 for 10 times respectively. And the patient monitor was used to observe the oxygen saturation (SO2) variation. The variation of SO2, and length of breath‐holding time and the time for recovering to the initial value of SO2 were recorded and analyzed.Results:(1) The volunteers were divided into two groups according to the SO2 variation in breath‐holding: A group, 14 cases whose SO2 reduction were more than 2% (initial value was 97% to 99%, while termination value was 91% to 96%); B group, 10 cases were less than 2% in breath‐holding without inhaling oxygen. (2) The interfraction breath holding time varied from 8 to 20s for A group compared to the first breath‐holding time, and for B group varied from 4 to 14s. (3) The breathing holding time of B group prolonged mean 8s, compared to A group. (4) The time for restoring to the initial value of SO2 was from 10s to 30s. And the breath‐holding time shortened obviously for patients whose SO2 did not recover to normal.Conclusion:It is very obvious that the SO2 reduction in breath‐holding associated with ABC for partial people. It is necessary to check the SO2 variation in breath training, and enough time should be given to recover SO2.

HDO and SO2thermal mapping on Venus

Sulfur dioxide and water vapor, two key species of Venus photochemistry, are known to exhibit significant spatial and temporal variations above the cloud top. In particular, ground-based thermal imaging spectroscopy at high spectral resolution, achieved on Venus in January 2012, has shown evidence for strong SO2 variations on timescales shorter than a day. We have continued our observing campaign using the TEXES high-resolution imaging spectrometer at the NASA InfraRed Telescope Facility to map sulfur dioxide over the disk of Venus at two different wavelengths, 7 μm (already used in the previous study) and 19 μm. The 7 μm radiation probes the top of the H2SO4 cloud, while the 19 μm radiation probes a few kilometers below within the cloud. Observations took place on October 4 and 5, 2012. Both HDO and SO2 lines are identified in our 7-μm spectra and SO2 is also easily identified at 19 μm. The CO2 lines at 7 and 19 μm are used to infer the thermal structure. An isothermal/inversion layer is present at high latitudes (above 60 N and S) in the polar collars, which was not detected in October 2012. The enhancement of the polar collar in October 2012 is probably due to the fact that the morning terminator is observed, while the January data probed the evening terminator. As observed in our previous run, the HDO map is relatively uniform over the disk of Venus, with a mean mixing ratio of about 1 ppm. In contrast, the SO2 maps at 19 μm show intensity variations by a factor of about 2 over the disk within the cloud, less patchy than observed at the cloud top at 7 μm. In addition, the SO2 maps seem to indicate significant temporal changes within an hour. There is evidence for a cutoff in the SO2 vertical distribution above the cloud top, also previously observed by SPICAV/SOIR aboard Venus Express and predicted by photochemical models.

Study of a high SO2 event observed over an urban site in western India

Continuous measurements of SO2, NOx and O3 along with sampling based measurements of CO, CH4, NMHCs and CO2 were carried out during May, 2010 at Ahmedabad. The diurnal variations of SO2 in ambient air exhibited elevated values during the night and lower levels during the sunlit hours. The mean concentration of SO2 during the study period was 0.95 ± 0.88 ppbv. However, the ambient SO2 exceeded 17 ppbv in the night of 20 May, 2010. On the same day, tropospheric columnar SO2 from OMI showed almost 350% increase corroborating the surface observations over an extended height regime. This was also the highest columnar value of SO2 during the summer of 2010. Columnar loadings were also found to be high for formaldehyde, precipitable water vapor and aerosol optical depth on 20 May. Elevated concentrations were also recorded for other trace gases like NO2 and O3. Analysis of related data of trace gases indicated characteristics of fresh emissions with dominant contributions from mobile sources during the study period. However, SO2/NO2 ratio of 0.36 during the event period on 20th May connotes non-local influences. Analyses of meteorological parameters suggest combined impacts of transport and inversion causing higher levels of SO2 and other pollutants during 20–21 May. Episodes of such enhancements may perturb chemical and radiative balance of the atmosphere.

Significant downward trend of SO2 observed from 2005 to 2010 at a background station in the Yangtze Delta region, China

SO2 is an important gas in atmosphere with great environmental and climate implications. SO2 emission in China has been receiving great attention as the economy grows and the amount of coal consumption has increased in the past few decades. SO2 has been observed from July 2005 to June 2010 at Linan WMO GAW regional station (30.3 °N, 119.73 °E, 138 m a.s.l.) located in the Yangtze Delta region in eastern China. These observation data are analyzed to understand the trend of regional SO2 background concentration. Strict quality controls are conducted to ensure the temporal comparability of the data. Significant downward trend with −2.4 ppb/yr (P < 0.0001) of surface SO2 is observed from 2005 to 2010, especially after 2008. The average concentration of SO2 from July 2005 to June 2008 is 14.2±3.1 ppb, which is slightly higher than the mean values of 13.5±5.1 ppb during 1999–2000 and is two folds of the average value (7.1±3.1 ppb) from July 2008 to June 2010. More than 50% of the SO2 has been cut down after 2008 in the Yangtze Delta region due to the implementation of stricter emission control measures. The peak SO2 concentration appears around 10 o’clock in the morning after 2009 while appears at night before 2009. These diurnal variations of SO2 might indicate that after 2009, more SO2 is from the vertical exchange process than from the local accumulation.

A photochemical model for the Venus atmosphere at 47–112 km

The model is intended to respond to the recent findings in the Venus atmosphere from the Venus Express and ground-based submillimeter and infrared observations. It extends down to 47km for comparison with the kinetic model for the lower atmosphere (Krasnopolsky, V.A. [2007]. Icarus 191, 25–37) and to use its results as the boundary conditions. The model numerical accuracy is significantly improved by reduction of the altitude step from 2km in the previous models to 0.5km. Effects of the NUV absorber are approximated using the detailed photometric observations at 365nm from Venera 14. The H2O profile is not fixed but calculated in the model. The model involves odd nitrogen and OCS chemistries based on the detected NO and OCS abundances. The number of the reactions is significantly reduced by removing of unimportant processes. Column rates for all reactions are given, and balances of production and loss may be analyzed in detail for each species.The calculated vertical profiles of CO, H2O, HCl, SO2, SO, OCS and of the O2 dayglow at 1.27μm generally agree with the existing observational data; some differences are briefly discussed. The OH dayglow is ∼30 kR, brighter than the OH nightglow by a factor of 4. The H+O3 process dominates in the nightglow excitation and O+HO2 in the dayglow, because of the reduction of ozone by photolysis. A key feature of Venus’ photochemistry is the formation of sulfuric acid in a narrow layer near the cloud tops that greatly reduces abundances of SO2 and H2O above the clouds. Delivery of SO2 and H2O through this bottleneck determines the chemistry and its variations above the clouds. Small variations of eddy diffusion near 60km result in variations of SO2, SO, and OCS at and above 70km within a factor of ∼30. Variations of the SO2/H2O ratio at the lower boundary have similar but weaker effect: the variations within a factor of ∼4 are induced by changes of SO2/H2O by±5%. Therefore the observed variations of the mesospheric composition originate from minor variations of the atmospheric dynamics near the cloud layer and do not require volcanism. NO cycles are responsible for production of a quarter of O2, SO2, and Cl2 in the atmosphere. A net effect of photochemistry in the middle atmosphere is the consumption of CO2, SO2, and HCl from and return of CO, H2SO4, and SO2Cl2 to the lower atmosphere. These processes may be balanced by thermochemistry in the lower atmosphere even without outgassing from the interior, though the latter is not ruled out by our models. Some differences between the model and observations and the previous models are briefly discussed.

Study of SO2 and NO2 behaviour during the ozone-hole event at Antarctica by Brewer Spectrophotometer

Vertical column density of sulphur dioxide has been measured at Maitri (70.7°S, 11.7°E), the Indian station in the Antarctica from September, 1999 to December, 2006 by a Brewer Spectrophotometer. Simultaneously, nitrogen dioxide, ozone and the maximum value of UV-B have also been measured, we found an increase in SO2 during spring. An increase in NO2 column was also found during this period but not identical with that of SO2. These variations in SO2 and NO2 are not in phase with the increase in UV-B flux at the ground due to the decrease of ozone column in the stratosphere. The variation of SO2 column is explained by the downward shift of penetration depth of UV-B radiation during the ozone-hole event.

Radiolysis of sulfuric acid, sulfuric acid monohydrate, and sulfuric acid tetrahydrate and its relevance to Europa

We report laboratory studies on the 0.8 MeV proton irradiation of ices composed of sulfuric acid (H 2SO 4), sulfuric acid monohydrate (H 2SO 4·H 2O), and sulfuric acid tetrahydrate (H 2SO 4·4H 2O) between 10 and 180 K. Using infrared spectroscopy, we identify the main radiation products as H 2O, SO 2, (S 2O 3) x , H 3O +, HSO 4 - , and SO 4 2 - . At high radiation doses, we find that H 2SO 4 molecules are destroyed completely and that H 2SO 4·H 2O is formed on subsequent warming. This hydrate is significantly more stable to radiolytic destruction than pure H 2SO 4, falling to an equilibrium relative abundance of 50% of its original value on prolonged irradiation. Unlike either pure H 2SO 4 or H 2SO 4·H 2O, the loss of H 2SO 4·4H 2O exhibits a strong temperature dependence, as the tetrahydrate is essentially unchanged at the highest irradiation temperatures and completely destroyed at the lowest ones, which we speculate is due to a combination of radiolytic destruction and amorphization. Furthermore, at the lower temperatures it is clear that irradiation causes the tetrahydrate spectrum to transition to one that closely resembles the monohydrate spectrum. Extrapolating our results to Europa’s surface, we speculate that the variations in SO 2 concentrations observed in the chaotic terrains are a result of radiation processing of lower hydration states of sulfuric acid and that the monohydrate will remain stable on the surface over geological times, while the tetrahydrate will remain stable in the warmer regions but be destroyed in the colder regions, unless it can be reformed by other processes, such as thermal reactions induced by diurnal cycling.

Remediation of coal-mine drainage by a sulfate-reducing bioreactor: A case study from the Illinois coal basin, USA

Abstract This study reports changes in coal-mine drainage constituent concentrations through an anaerobic SO4-reducing bioreactor monitored over a 3-a period. The purpose of the study was to identify and monitor over time the biogeochemical mechanisms that control the attenuation of toxic compounds in the mine drainage. This information is needed to investigate bioreactor performance and longevity. The water treated at the case example site, the Tab-Simco Mine, was highly acidic with an average pH of 2.9, a net acidity of 1674 mg/L CaCO3 equivalent-CCE, and high levels of dissolved SO 4 2 - , Al, Fe and Mn. The results of this study indicated that the treatment system increased the pH of the acid mine drainage (AMD) to 6.2 and decreased the median acidity to 22.7 mg/L CCE, SO 4 2 - from 2981 to 1750 mg/L, Fe from 450.6 to 1.76 mg/L, Al from 113 to 0.42 mg/L, and Mn from 36.4 to 23.3 mg/L. Geochemical modeling indicates that the bioreactor discharge is saturated with respect to the minerals alunite, gibbsite, siderite, rhodochrosite, jarosite, and Fe hydroxide precipitates. The observed trends also include seasonal variations in SO 4 2 - reduction and a general decline in the amount of alkalinity produced. The average δ34S value of the SO 4 2 - in the untreated AMD was +7.3‰. In the bioreactor, δ34S value of SO 4 2 - increased from an average of +6.9‰ to +9.2‰, suggesting the presence of bacterial SO4 reduction processes. Preliminary results of a bacterial community analysis show that DNA sequences corresponding to bacteria capable of SO4 reduction were present in the bioreactor outflow sample. However, these sequences were outnumbered by sequences similar to bacteria capable of reoxdizing reduced sulfur species. This study illustrates the dynamic nature of metal removal in SO4-reducing bioreactor-based treatment systems.

In vivo integrated photoacoustic and confocal microscopy of hemoglobin oxygen saturation and oxygen partial pressure

We developed dual-modality microscope integrating photoacoustic microscopy (PAM) and fluorescence confocal microscopy (FCM) to noninvasively image hemoglobin oxygen saturation (sO₂) and oxygen partial pressure (pO₂) in vivo in single blood vessels with high spatial resolution. While PAM measures sO₂ by imaging hemoglobin optical absorption at two wavelengths, FCM quantifies pO₂ using phosphorescence quenching. The variations of sO₂ and pO₂ values in multiple orders of vessel branches under hyperoxic (100% oxygen) and normoxic (21% oxygen) conditions correlate well with the oxygen-hemoglobin dissociation curve. In addition, the total concentration of hemoglobin is imaged by PAM at an isosbestic wavelength.

Ambient sulfur dioxide, nitrogen dioxide, and ammonia at ten background and rural sites in China during 2007–2008

We present two years (January 2007–December 2008) of atmospheric SO 2, NO 2 and NH 3 measurements from ten background or rural sites in nine provinces in China. The measurements were made on a monthly basis using passive samplers under careful quality control. The results show large geographical and seasonal variations in the concentrations of these gases. The mean SO 2 concentration varied from 0.7 ± 0.4 ppb at Waliguan on Qinghai Plateau to 67.3 ± 31.1 ppb at Kaili in Guizhou province. The mean NO 2 concentration ranged from 0.6 ± 0.4 ppb at Waliguan to 23.9 ± 6.9 ppb at Houma in southern Shanxi. The mean NH 3 concentration ranged from 2.8 ± 3.0 ppb at Shangdianzi in northeastern Beijing to 13.7 ± 8.4 ppb at Houma. At most sites, SO 2 and NO 2 peaked in winter and reached minima in summer, while NH 3 showed maximum values in summer and lower values in cold seasons. On the whole, the geographical distributions of the observed gas concentrations are consistent with those of emissions. The ground measurements of SO 2 and NO 2 are contrasted to the SCIAMACHY SO 2 and OMI NO 2 tropospheric columns, respectively. Although the satellite data can capture the main features of emissions and concentrations of SO 2, they do not reflect the variations of SO 2 in the surface layer. The situation is better for the case of NO 2. The OMI NO 2 columns capture the geographical differences in the ground NO 2 and correlate fairly well with the ground levels of NO 2 at six of the ten sites.

Variation of ambient SO2 over Delhi

The temporal variation of ambient SO2 and the chemical composition of particulate matters (PM2.5 and PM10) were studied at National Physical Laboratory (NPL), New Delhi (28°38′N, 77°10′E). Spatial variation of SO2 at seven air quality monitoring stations over Delhi was also studied simultaneously. Wide range of ambient SO2 was recorded during winter (2.55 to 17.43 ppb) compare to other seasons. SO2 mixing ratio was recorded significantly high at industrial sites during winter and summer; however, no significant spatial difference in SO2 mixing ratio was recorded during monsoon. SO42−/(SO2+SO42−) ratio was recorded high (0.74) during winter and low (0.69) during summer. Monthly variation of PSCF was analyzed using HYSPLIT seven days backward trajectories and daily average SO2 data. PSCF analysis suggests that, during winter (December, January, February) ambient SO2 at the study site might have contributed from long distance sources, located towards west and southwest directions; during monsoon (July, August, September) marine contribution was noticed; whereas, during summer (April, May and June) it was from regional sources (located within few 100 km of study site). During winter there was significant contribution from the long distance sources located in western Asia, northwestern Pakistan, Rajasthan and Punjab provinces of India. Coal used in thermal power plants at Panipat (in the northwestern side) and Faridabad (in the southeastern side), local industries, soil erosion and biomass burning may be major contributing factors for SO2 during summer. The study establishes that the transport sector may not be the major source of ambient SO2 in Delhi.

Pitting of zinc: Observations on atmospheric corrosion in tropical countries

A five-nation study has investigated the mechanisms and rates of the atmospheric corrosion of zinc and steel in tropical regions in Australia, Thailand, Indonesia, Vietnam and The Philippines. For the study, 18 exposure sites encompassing severe marine, marine, severe industrial, industrial, marine/industrial, urban and highland environments were established across the countries. At each location, zinc and steel plates were exposed for periods of three months and one year, and measurements were taken of a wide range of surface-response and climatic parameters, including gaseous SO x and NO x , airborne salinity, relative humidity (RH) and temperature, rainwater composition, surface temperature and time of wetness (TOW). Exposed plates were used to determine mass loss, the nature of corrosion products (using FTIR and SEM-EDS) and the morphologies of corrosion layers (via SEM-EDS). Regression analysis indicated that the prime factors controlling zinc corrosion rate were climate (temperature and rainfall) and surface-response (TOW), and surprisingly not pollutant levels, despite significant variation in SO x levels across the sites. SEM studies indicated the presence of pitting below the oxide layers on zinc, particularly those plates exposed at marine and other sites with relatively low SO x levels. In contrast, no pitting was observed (or pits had very low aspect ratios) in the specimens exposed at sites with high SO x levels. The possible processes leading to the observed damage patterns are discussed.