Preclinical multi-physiologic monitoring of immediate-early responses to diverse treatment strategies in breast cancer by optoacoustic imaging.

Optoacoustic imaging enables the measurement of tissue oxygen saturation (sO2) and blood perfusion while being utilized for detecting tumor microenvironments. Our aim was to employ multispectral optoacoustic tomography (MSOT) to assess immediate-early changes of hemoglobin level and sO2 within breast tumors during diverse treatments. Mouse breast cancer models were allocated into four groups: control, everolimus (EVE), paclitaxel (PTX), and photodynamic therapy (PDT). Hemoglobin was quantified daily, as well as sO2 and blood perfusion were verified by immunohistochemical (IHC) staining. MSOT showed a temporal window of enhanced oxygenation and improved perfusion in EVE and PTX groups, while sO2 consistently remained below baseline in PDT. The same results were obtained for the IHC. Therefore, MSOT can monitor tumor hypoxia and indirectly reflect blood perfusion in a non-invasive and non-labeled way, which has the potential to monitor breast cancer progression early and enable individualized treatment in clinical practice.

Correction: Pu et al. Exosome miRNA Expression in Umbilical Cord Blood of High-Parity Sows Regulates Their Reproductive Potential. Animals 2022, 12, 2456.

In the original publication [...].

Glutamate Chemical Exchange Saturation Transfer (GluCEST) MRI to Evaluate the Rapid Antidepressant Effects of Ketamine in the Hippocampus of Rat Depression Model.

BACKGROUND: Ketamine is a quick acting antidepressant drug, and an accurate detection method is lacking. Ketamine's effects in a rat depression model have not previously been well explored using glutamate chemical exchange saturation transfer (GluCEST). PURPOSE: To investigate the GluCEST changes of chronic unpredictable mild stress (CUMS) rats after receiving either ketamine or saline injection. STUDY TYPE: Randomized animal model trial. ANIMAL MODEL: 12 CUMS and 6 Sprague-Dawley rats. Divided into three groups: ketamine (N = 6), saline (N = 6), and control (N = 6). FIELD STRENGTH/SEQUENCE: 7.0 T/the sequence is GluCEST and 1 H MR spectroscopy (MRS). ASSESSMENT: The CUMS rats were exposed to different stress factors for 8 weeks. The glutamate concentration in the hippocampus was assessed by the GluCEST,1 H MRS, and the high-performance liquid chromatography (HPLC). STATISTICAL TESTS: The t-test, Mann-Whitney U test, and Pearson's correlation. RESULTS: In depression conditions, GluCEST signals were lower in the bilateral hippocampus than in control group. Thirty minutes after ketamine injection, the GluCEST signals in the bilateral hippocampus were higher compared with the saline group (left: 2.99 ± 0.34 [Control] vs. 2.44 ± 0.20 [Saline] vs. 2.85 ± 0.11 [Ketamine]; right: 2.97 ± 0.28 [Control] vs. 2.49 ± 0.25 [Saline] vs. 2.86 ± 0.19 [Ketamine]). In 1 H MRS, significant changes were only observed in the left hippocampus (2.00 ± 0.16 [Control] vs. 1.81 ± 0.09 [Saline] vs. 2.04 ± 0.14 [Ketamine]). Furthermore, HPLC results showed similar trends to those observed in the GluCEST results (left: 2.32 ± 0.22 [Control] vs. 1.96 ± 0.11 [Saline] vs. 2.18 ± 0.11 [Ketamine]; right: 2.35 ± 0.18 [Control] vs. 1.87 ± 0.16 [Saline] vs. 2.09 ± 0.08 [Ketamine]). DATA CONCLUSION: GluCEST can sensitively evaluate the ketamine's antidepressant effects by detecting the fast increase in glutamate concentration. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 1.

Type I MADS-box transcription factor TaMADS-GS regulates grain size by stabilizing cytokinin signalling during endosperm cellularization in wheat.

Grain size is one of the important traits in wheat breeding programs aimed at improving yield, and cytokinins, mainly involved in cell division, have a positive impact on grain size. Here, we identified a novel wheat gene TaMADS-GS encoding type I MADS-box transcription factor, which regulates the cytokinins signalling pathway during early stages of grain development to modulate grain size and weight in wheat. TaMADS-GS is exclusively expressed in grains at early stage of seed development and its knockout leads to delayed endosperm cellularization, smaller grain size and lower grain weight. TaMADS-GS protein interacts with the Polycomb Repressive Complex 2 (PRC2) and leads to repression of genes encoding cytokinin oxidase/dehydrogenases (CKXs) stimulating cytokinins inactivation by mediating accumulation of the histone H3 trimethylation at lysine 27 (H3K27me3). Through the screening of a large wheat germplasm collection, an elite allele of the TaMADS-GS exhibits higher ability to repress expression of genes inactivating cytokinins and a positive correlation with grain size and weight, thus representing a novel marker for breeding programs in wheat. Overall, these findings support the relevance of TaMADS-GS as a key regulator of wheat grain size and weight.

Using drone soundings to study the impacts and compositions of plumes from a gigantic coal-fired power plant.

The immense impacts of coal-fired power plant plumes on the atmospheric environment have caused great concern linked to climate and health issues. However, studies on the field observations of aerial plumes are relatively limited, mainly due to the lack of suitable plume observation tools and techniques. In this study, we use a multicopter unmanned aerial vehicle (UAV) sounding technique to study the influences of the aerial plumes of the world's fourth-largest coal-fired power plant on the atmospheric physical/chemical conditions and air quality. A set of species, including 106 volatile organic compounds (VOCs), CO, CO2, CH4, PM2.5, and O3, and meteorological variables of temperature (T), specific humidity (SH), and wind data, are collected by the UAV sounding technique. The results reveal that the large-scale plumes of the coal-fired power plant cause local temperature inversion and humidity changes, and even affect the dispersion of pollutants below. The chemical compositions of coal-fired power plant plumes are significantly different from those of another ubiquitous vehicular source. High fractions of ethane, ethene, and benzene and low fractions of n-butane and isopentane found in plumes could serve as the key features to help distinguish the influences of coal-fired power plant plumes from other pollution sources in a particular area. By taking the ratios of pollutants (e.g., PM2.5, CO, CH4, and VOCs) to CO2 in plumes and the CO2 emission amounts of the power plant into calculation, we enable the easy quantification of the specific pollutant emissions released from power plant plumes to the atmosphere. In summary, observation by using drone soundings dissecting the aerial plumes provides a new methodology that allows aerial plumes to be readily detected and characterized. Furthermore, the influences of the plumes on the atmospheric physical/chemical conditions and air quality can be assessed rather straightforwardly, which was not easily achievable in the past.

Integrated ground and vertical measurement techniques to characterize overhead atmosphere: Case studies of local versus transboundary pollution.

Much attention has been found to the long-range transport (LRT) of air pollutants and their adverse effects on downwind air qualities resulting from the Chinese haze, which frequently occurs in association with winter monsoon. This study integrates ground-based measurements, unmanned aerial vehicles (UAVs), and model simulations to characterize the meteorological, chemical, and particulate matter (PM) properties comprehensively for the events that were LRT or local pollution (LP) dominated in northern Taiwan during the wintertime of 2017. During the two types of episodes, various approaches were made to investigate the vertical mixing conditions and PM properties with UAV flights. A confined and PM accumulated feature near ground level with a temperature inversion was found during the LP event. In contrast, a vertically homogeneous atmospheric structure with strong winds was suggested during the LRT event. Independent measurements of criteria air pollutants, meteorological variables, volatile organic compounds (VOCs), and micropulse lidar (MPL) made at the ground level were closely supported by the vertical measurements. When synchronizing all these observational and numerical tools in a three-dimensional manner, the characterization of air masses and possible origins of pollution, such as LP vs. LRT, has now become more versatile and capable of gaining a complete picture of atmospheric conditions that define air quality.

Infusing satellite data into aerosol forecast for near real-time episode detection and diagnosis in East Asia.

A near-real-time (NRT) aerosol forecast and diagnostic approach is developed based on the system of Infusing satellite Data into Environmental Applications for East Asia, herein denoted as IDEA-EA. The design incorporates a 0.5-degree Global Forecast System (GFS) and Visible Infrared Imaging Radiometer Suite (VIIRS) aerosol and cloud retrievals for meteorological and remote sensing inputs. The primary output of IDEA-EA includes aerosol forward and backward air mass trajectory forecasts, migration visualization, and data synthesis purposed for NRT aerosol detection, monitoring, and source tracing in East Asia. Two aerosol episodes of Southeast Asia (SEA) biomass burning and Chinese haze infusion with Gobi dust are illustrated by IDEA-EA to demonstrate its forecast and source tracing capabilities. In the case of SEA biomass burning (late March 2021), forward trajectories of IDEA-EA forecasted air masses with high aerosol optical depth (AOD) from SEA affecting Taiwan. The IDEA-EA forecasts were verified by increased AOD and surface PM2.5 observations at a mountain site. In the case of the Chinese haze (October 30, 2019), backward trajectories from the northern tip of Taiwan traced air masses back to the east coast of mainland China and possibly further to the Gobi Desert. Compared with conventional numerical model simulations, the combination of the state-of-the-art aerosol remote sensing and trajectory modeling in IDEA-EA provides a cost-effective alternative for air quality management.

Multifunctional Nanosnowflakes for T1-T2 Double-Contrast Enhanced MRI and PAI Guided Oxygen Self-Supplementing Effective Anti-Tumor Therapy.

Introduction: Accurate tumor diagnosis is essential to achieve the ideal therapeutic effect. However, it is difficult to accurately diagnose cancer using a single imaging method because of the technical limitations. Multimodal imaging plays an increasingly important role in tumor treatment. Photodynamic therapy (PDT) has received widespread attention in tumor treatment due to its high specificity and controllable photocytotoxicity. Nevertheless, PDT is susceptible to tumor microenvironment (TME) hypoxia, which greatly reduces the therapeutic effect of tumor treatment. Methods: In this study, a novel multifunctional nano-snowflake probe (USPIO@MnO2@Ce6, UMC) for oxygen-enhanced photodynamic therapy was developed. We have fabricated the honeycomb-like MnO2 to co-load chlorin e6 (Ce6, a photosensitizer) and ultrasmall superparamagnetic iron oxide (USPIO, T1-T2 double contrast agent). Under the high H2O2 level of tumor cells, UMC efficiently degraded and triggered the exposure of photosensitizers to the generated oxygen, accelerating the production of reactive oxygen species (ROS) during PDT. Moreover, the resulting USPIO and Mn2+ allow for MR T1-T2 imaging and transformable PAI for multimodal imaging-guided tumor therapy. Results: TEM and UV-vis spectroscopy results showed that nano-snowflake probe (UMC) was successfully synthesized, and the degradation of UMC was due to the pH/ H2O2 responsive properties. In vitro results indicated good uptake of UMC in 4T-1 cells, with maximal accumulation at 4 h. In vitro and in vivo experimental results showed their imaging capability for both T1-T2 MR and PA imaging, providing the potential for multimodal imaging-guided tumor therapy. Compared to the free Ce6, UMC exhibited enhanced treatment efficiency due to the production of O2 with the assistance of 660 nm laser irradiation. In vivo experiments confirmed that UMC achieved oxygenated PDT under MR/PA imaging guidance in tumor-bearing mice and significantly inhibited tumor growth in tumor-bearing mice, exhibiting good biocompatibility and minimal side effects. Conclusion: The multimodal imaging contrast agent (UMC) not only can be used for MR and PA imaging but also has oxygen-enhanced PDT capabilities. These results suggest that UMC may have a good potential for further clinical application in the future.

Exosome miRNA Expression in Umbilical Cord Blood of High-Parity Sows Regulates Their Reproductive Potential.

The objective of modern pig breeding is to improve the genetic reproduction performance potential of sows, including the litter size and weight of piglets. During the gestation period, the umbilical cord facilitates placenta−fetal communication; thus, it plays an indispensable role in intrauterine embryonic development and fitness. Herein, we analyzed the molecular mechanism in declining reproductive potential in high-parity sows by assessing the changes in the umbilical cord blood. Firstly, we analyzed the reproductive characteristics data of sows, followed by histological analysis of the umbilical cord phenotype. Next, we evaluated the effect of umbilical cord blood exosomes (UCB-EXO) on angiogenesis. Finally, the miRNA expression in UCB-EXO from high-parity sows with poor reproductive performance (OS) and multiparous sows with excellent reproductive performance (MS) was assessed. Overall, the best reproductive performance was at parity 3−7, gradually decreasing after parity 8 and angiogenesis was repressed in OS. However, exosomes derived from MS (Exo-MS) exhibited pro-angiogenesis properties but were diminished in exosomes derived from OS (Exo-OS). Additionally, the angiogenesis of sows was significantly decreased, increasing the risk of disease with the increase in parity, greatly limiting the reproductive potential of the sows. At the same time, miR-188-5p expression in Exo-OS was significantly higher than in Exo-MS (p < 0.01), implying that it may play an important role in regulating the lifespan and reproductive potential of sows. These findings demonstrated that miRNAs in UCB-EXO play a central role in intrauterine development. Further, the findings suggest novel insights on reproductive potential, which provide a reference for increasing the sow reproductive efficiency.

Unprocessed wheat γ-gliadin reduces gluten accumulation associated with the endoplasmic reticulum stress and elevated cell death.

Along with increasing demands for high yield, elite processing quality and improved nutrient value in wheat, concerns have emerged around the effects of gluten in wheat-based foods on human health. However, knowledge of the mechanisms regulating gluten accumulation remains largely unexplored. Here we report the identification and characterization of a wheat low gluten protein 1 (lgp1) mutant that shows extremely low levels of gliadins and glutenins. The lgp1 mutation in a single γ-gliadin gene causes defective signal peptide cleavage, resulting in the accumulation of an excessive amount of unprocessed γ-gliadin and a reduced level of gluten, which alters the endoplasmic reticulum (ER) structure, forms the autophagosome-like structures, leads to the delivery of seed storage proteins to the extracellular space and causes a reduction in starch biosynthesis. Physiologically, these effects trigger ER stress and cell death. This study unravels a unique mechanism that unprocessed γ-gliadin reduces gluten accumulation associated with ER stress and elevated cell death in wheat. Moreover, the reduced gluten level in the lgp1 mutant makes it a good candidate for specific diets for patients with diabetes or kidney diease.

Distinct transport mechanisms of East Asian dust and the impact on downwind marine and atmospheric environments.

East Asian dust episodes have a multitude of impacts, including on human health, environment, and climate over near-source and receptor regions. However, the mechanistic understanding of the synoptic conditions of these outbreaks at different altitude layers, and their eventual environmental impacts are less studied. The present study analyzed the synoptic transport patterns of East Asian dust during multiple dust generation episodes that occurred over only a few days apart in northern China, and which eventually delivered high PM10 concentrations to surface level and high-altitude locations in Taiwan. Whether the dust plume was uplifted ahead of or behind the 700 hPa trough over East Asia determined its trajectory and eventual impact on the environment downwind. The total dust (iron) deposition over the ocean surface preceding arrival to Taiwan was 2.4 mg m-2 (0.95 µg m-2) for the episode impacting the surface level and 5.0 mg m-2 (4.6 µg m-2) for the episode impacting high-altitude Taiwan. Dust deposition in marine areas east of China was more intense for the higher altitude transport event that was uplifted behind the 700 hPa trough and resulted in twice higher marine Chl-a concentrations. Furthermore, we estimated a dust-induced direct radiative effect over a high mountainous region in Taiwan of -6.2 to -8.2 W m-2 at the surface, -1.9 to -2.9 W m-2 at the top of the atmosphere and +3.9 to +5.3 W m-2 in the atmosphere. This dust-induced atmospheric warming and surface cooling are non-negligible influences on the atmospheric thermal structure and biogeochemical cycle over the western North Pacific. Overall, this study highlights the significant impacts of dust particles on the marine ecosystem and atmospheric radiation budget over the downwind region, thus lays the foundation for linking these impacts to the initial synoptic conditions in the source area.

Investigation of East Asian Emissions of CFC-11 Using Atmospheric Observations in Taiwan.

Recent findings of an unexpected slowdown in the decline of CFC-11 mixing ratios in the atmosphere have led to the conclusion that global CFC-11 emissions have increased over the past decade and have been attributed in part to eastern China. This study independently assesses these findings by evaluating enhancements of CFC-11 mixing ratios in air samples collected in Taiwan between 2014 and 2018. Using the NAME (Numerical Atmospheric Modeling Environment) particle dispersion model, we find the likely source of the enhanced CFC-11 observed in Taiwan to be East China. Other halogenated trace gases were also measured, and there were positive interspecies correlations between CFC-11 and CHCl3, CCl4, HCFC-141b, HCFC-142b, CH2Cl2, and HCFC-22, indicating co-location of the emissions of these compounds. These correlations in combination with published emission estimates of CH2Cl2 and HCFC-22 from China, and of CHCl3 and CCl4 from eastern China, are used to estimate CFC-11 emissions. Within the uncertainties, these estimates do not differ for eastern China and the whole of China, so we combine them to derive a mean estimate that we term as being from "(eastern) China". For 2014-2018, we estimate an emission of 19 ± 5 Gg year-1 (gigagrams per year) of CFC-11 from (eastern) China, approximately one-quarter of global emissions. Comparing this to previously reported CFC-11 emissions estimated for earlier years, we estimate CFC-11 emissions from (eastern) China to have increased by 7 ± 5 Gg year-1 from the 2008-2011 average to the 2014-2018 average, which is 50 ± 40% of the estimated increase in global CFC-11 emissions and is consistent with the emission increases attributed to this region in an earlier study.

Characterization of industrial plumes of volatile organic compounds by guided sampling.

Instead of manual sampling in a random way near a source area, this study used trigger sampling guided by an analyzer at a fixed site near a refinery plant to obtain the chemical composition of volatile organic compounds (VOCs) representative of the source. The analyzer was built in-house to measure total VOC (TVOC) levels by subtracting methane from total combustible organic compounds (TOC) with flame ionization detection. The analyzer with minute resolution provided instantaneous measurements of TVOCs to trigger canister sampling at the moments of VOC plumes in a source area. The chemical composition of the 13 trigger samples were compared with the other non-trigger samples randomly collected either within the refinery or on an urban street. All samples were analyzed by gas chromatography-mass spectrometry/flame ionization detection (GC-MS/FID) for detailed speciation. High agreement in total VOC abundance between the analyzer and GC-MS/FID indicates internal consistency of the two techniques and the robustness of the TVOC analyzer to guide sampling of VOC plumes. The trigger samples showing very high consistency in the overall composition imply that sampling at the right moments of plume arrivals can facilitate characterization of the source profiles, which can hardly be achieved by random sampling. The coupling of the fast-and-slow analytical techniques to guide sampling is proven to be an effective means to probe source characteristics.

High Molecular Weight Glutenin Subunits 1Bx7 and 1By9 Encoded by Glu-B1 Locus Affect Wheat Dough Properties and Sponge Cake Quality.

High molecular weight glutenin subunits (HMW-GSs) are important components of wheat (Triticum aestivum L.) gluten proteins that affect the processing quality of wheat dough. However, the contributions of individual HMW-GS to sponge cake quality still remain unclear. To investigate the effects of 1Bx7 and 1By9 at Glu-B1 on wheat gluten properties and sponge cake quality, we screened an ethylmethanesulfonate (EMS)-mutagenized wheat population and obtained two independent mutants that lack 1Bx7 and another two mutants that lack 1By9. The absence of 1Bx7 or 1By9 significantly affects the accumulation levels of gluten proteins and the formation of a gluten network. Quality testing indicated that the lack of 1Bx7 or 1By9 leads to weaker dough strength and inferior sponge cake performance. These results demonstrate that 1Bx7 and 1By9 make important contributions to gluten functionality and sponge cake quality.

Long-term monitoring of atmospheric PCDD/Fs at Mount Lulin during spring season: PCDD/F source apportionment through a simultaneous measurement in Southeast Asia.

A long term assessment of atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) at Mt. Lulin, located in center of Taiwan was carried out from 2008 to 2013 (n = 81) assuming Mt. Lulin to be background area. During monitoring processes, PCDD/F samples collected in the field occasionally reached high concentration. To investigate this situation, simultaneous sample collection was carried out in Southeast Asia countries (i.e., Vietnam and Thailand) and Taiwan in 2013. The average concentration of atmospheric PCDD/Fs in biomass-burning source regions, namely Son La and Doi Ang Khang were 19.8 ± 12.1 fg I-TEQ m-3 (n = 19) and 17.8 ± 12.4 fg I-TEQ m-3 (n = 20), respectively. In the downwind area of Mt. Lulin, the average concentration of PCDD/Fs was found to be 4.64 ± 3.77 fg I-TEQ m-3 (n = 18). PCDD/F concentration in the source region was much higher than that in the downwind region. On March 19, 2013, the atmospheric PCDD/F concentrations increased dramatically from 7.71 to 484 fg I-TEQ m-3 at Mt. Lulin, which many times exceeded that of assumed source region in Southeast Asia. Moreover, mainland Southeast Asia and the southeast coast of China was suspected to be the main contributors of atmospheric PCDD/Fs and biomass markers, such as nonsea-salt K+ and NH4+, during the spring. WRF-Chem and Potential Source Contribution Function (PSCF) simulations have confirmed this correlation. It can be concluded that atmospheric PCDD/Fs observed at Mt. Lulin during spring mostly derived from the air mass transport not only from Southeast Asia but also the southeast coast of China.

Two-dimensional gas chromatography with electron capture detection for the analysis of atmospheric ozone depleting halocarbons.

This study is to develop a GC×GC method with electron capture detection (ECD) to analyze atmospheric halocarbons in the concentration range of parts per trillion by volume (pptv). To enrich atmospheric halocarbons a home-built thermal desorption (TD) device was coupled to the GC×GC-ECD. The technique of flow modulation was adopted using a Deans switch for GC×GC. Several column combinations of first and second dimensions were tested and the column set of DB-5×TG-1301 was found to show the best orthogonality for halocarbons. A series of modulation parameters were tested for their optimal settings. The modulation period (PM) was found to have minimal wrap-around when set at 3s. The modulation ratio (MR) was determined to be 7.82 to ensure reproducible results and maximum sensitivity. The modulation duty cycle (DC) was calculated to be approximately 0.17. Nine halocarbons were separated successfully and seven were calibrated with the use of a certified standard gas mixture. The correlation coefficients (R2) were greater than 0.9972. The reproducibility was better than 1.90% as expressed in relative standard deviation (RSD; N=30) and the detection limits were in the range of pptv for the target halocarbons. A field test by continuous analyzing ambient air with hourly resolution was performed to show the stability of the method as suggested by the homogeneity of certain halocarbons, while also reflecting concentration variation for others when emissions did arise.

Characterization of thermal desorption with the Deans-switch technique in gas chromatographic analysis of volatile organic compounds.

This study presents a novel application based on the Deans-switch cutting technique to characterize the thermal-desorption (TD) properties for gas chromatographic (GC) analysis of ambient volatile organic compounds (VOCs). Flash-heating of the sorbent bed at high temperatures to desorb trapped VOCs to GC may easily produce severe asymmetric or tailing GC peaks affecting resolution and sensitivity if care is not taken to optimize the TD conditions. The TD peak without GC separation was first examined for the quality of the TD peak by analyzing a standard gas mixture from C2 to C12 at ppb level. The Deans switch was later applied in two different stages. First, it was used to cut the trailing tail of the TD peak, which, although significantly improved the GC peak symmetry, led to more loss of the higher boiling compounds than the low boiling ones, thus suggesting compound discrimination. Subsequently, the Deans switch was used to dissect the TD peak into six 30s slices in series, and an uneven distribution in composition between the slices were found. A progressive decrease in low boiling compounds and increase in higher boiling ones across the slices indicated severe inhomogeneity in the TD profile. This finding provided a clear evidence to answer the discrimination problem found with the tail cutting approach to improve peak symmetry. Through the use of the innovated slicing method based on the Deans-switch cutting technique, optimization of TD injection for highly resolved, symmetric and non-discriminated GC peaks can now be more quantitatively assessed and guided.

Construction of a cryogen-free thermal desorption gas chromatographic system with off-the-shelf components for monitoring ambient volatile organic compounds.

An automated gas chromatographic system aimed at performing unattended measurements of ambient volatile organic compounds was configured and tested. By exploiting various off-the-shelf components, the thermal desorption unit was easily assembled and can be connected with any existing commercial gas chromatograph in the laboratory to minimize cost. The performance of the complete thermal desorption gas chromatographic system was assessed by analyzing a standard mixture containing 56 target nonmethane hydrocarbons from C2 -C12 at sub-ppb levels. Particular attention was given to the enrichment efficiency of the C2 compounds, such as ethane (b.p. = -88.6°C) and ethylene (b.p. = -104.2°C), due to their extremely high volatilities. Quality assurance was performed in terms of the linearity, precision and limits of detection of the target compounds. To further validate the system, field measurements of target compounds in ambient air were compared with those of a commercial total hydrocarbon analyzer and a carbon monoxide analyzer. Highly coherent results from the three instruments were observed during a two-month period of synchronized measurements. Moreover, the phenomenon of opposite diurnal variations between the biogenic isoprene and anthropogenic species was exploited to help support the field applicability of the thermal desorption gas chromatographic method.

Changes in the levels and variability of halocarbons and the compliance with the Montreal Protocol from an urban view.

Ambient levels and variability of major atmospheric halocarbons, i.e. CFC-12, CFC-11, CFC-113, CCl4, CH3CCl3, C2HCl3, and C2Cl4 in a major metropolis (Taipei, Taiwan) were re-investigated after fourteen years by flask sampling in 2012. Our data indicates that the variability expressed as standard deviations (SD) of CFC-113 and CCl4 remained small (2.0 ppt and 1.9 ppt, respectively) for the 10th-90th percentile range in both sampling periods; whereas the variability of CFC-12, CFC-11, C2HCl3, and C2Cl4 measured in 2012 became noticeably smaller than observed in 1998, suggesting their emissions were reduced over time. By comparing with the background data of a global network (NOAA/ESRL/GMD baseline observatories), the ambient levels and distribution of these major halocarbons in Taipei approximated those at a background site (Mauna Loa) in 2012, suggesting that the fingerprint of the major halocarbons in a used-to-be prominent source area has gradually approached to that of the background atmosphere.