Wen-Tzu Liu

Metal–organic frameworks (MOFs) are promising sorbents for gas-phase volatile organic compounds (VOCs), yet rapid, application-oriented analytical workflows to benchmark their performance under repeated thermal desorption remain limited. In this study, we used a thermal desorption–gas chromatography/flame ionization detection (TD–GC/FID) system as a benchmarking platform for interchangeable packed sorbents. UiO-66, Heat-resistant UiO-66, and UiO-67 were evaluated as single-bed traps against a conventional multi-bed carbon reference using a 54-component mixture spanning C2–C11 VOCs under identical trapping, desorption, transfer, and chromatographic conditions.,A trapping temperature of -30 ℃ and a thermal desorption temperature of 250 ℃ yielded the most consistent analytical performance. Over sampled volumes of 200–600 mL, most C3–C11 chromatographic targets exhibited R2 values of 0.995–1.000 with precision of 0.1–4.4% RSD. In contrast, performance was substantially poorer for highly volatile C2 compounds. A per-carbon response (PCRC) metric, calculated from the integrated FID peak area normalized to molecular carbon number, was used to compare sorbent-dependent responses. Excluding C2, the relative carbon-normalized responses of the UiO-type sorbents ranged from approximately 72% to 119% of the multi-bed carbon reference. Tailing-factor and signal-to-noise analyses further differentiated sorbent-dependent chromatographic behavior, with Heat-resistant UiO-66 showing overall analytical performance most comparable to the carbon reference.,During four days of automated boundary-air monitoring, all three MOF traps maintained standard-check recoveries within the adopted 75–125% acceptance range during repeated TD operation. PXRD and SEM analyses after repeated TD operation showed greater structural and morphological stability of Heat-resistant UiO-66 than conventional UiO-66 and UiO-67, while N₂ adsorption–desorption measurements further showed that the surface area of Heat-resistant UiO-66 remained nearly unchanged relative to conventional UiO-66. These results demonstrate that the TD–GC/FID analytical platform provides a practical analytical workflow for benchmarking the multicomponent preconcentration and cyclic performance of packable porous sorbents, while Heat-resistant UiO-66 shows promise for TD-based analysis of C3–C11 VOCs.

This study examines high‐ozone episodes in an urban area of northern Taiwan influenced by local photochemical processes and transboundary pollution from the Asian continent. Long‐term data sets from Photochemical Assessment Monitoring Stations and Air Quality Monitoring Stations were used to develop a photochemical metric based on volatile organic compounds ratios. We analyzed the ratio of ln(n‐butane/ethane) versus ln(n‐pentane/ethane) based on which we derived the δ value to assess the degree of regional air mass aging from a chemical reactivity perspective. In summer, extreme ozone events with low δ values are primarily driven by local photochemical activity. However, in fall and spring, the slightly higher δ values in some episodes signify the involvement of long‐range transport (LRT) bringing in continental ozone and cooler air masses while local photochemistry remains active. The interaction between transported and locally produced ozone is pronounced during milder ozone episodes (100–120 ppbv). We further examined the m,p‐xylene/ethylbenzene ratio as a complementary chemical indicator for characterizing ozone events with mild LRT. Slightly lower temperatures (below 28.8°C) are often accompanied by elevated nocturnal ozone levels (40–80 ppbv) and a less defined m,p‐xylene/ethylbenzene ratio. Overall, high‐ozone episodes (≥100 ppbv) are primarily driven by local photochemical processes. However, LRT can elevate the ozone baseline, particularly during spring and fall, when aged air masses bring in residual ozone leading to increased daytime ozone levels. These findings highlight how local photochemistry and regional transport shape high‐ozone episodes emphasizing the value of chemical indicators for understanding air mass aging and ozone formation.

Carbon dioxide (CO ₂ ) and methane (CH ₄ ) are major contributors to climate change, increasing radiative forcing and global warming. This study investigates temporal variations of CO ₂ and CH ₄ levels, along with CO ₂ isotopic ratios, at two western Pacific background sites: Lulin Atmospheric Background Station (LLN, 2,862 m ASL) in central Taiwan since August 2006, representing the free troposphere, and Dongsha Island (DSI, 8 m ASL) in the South China Sea since March 2010, representing sea‐level conditions. Mean growth rates of CO ₂ , CH ₄ , and δ ¹³ C‐CO ₂ at LLN, DSI, and Mauna Loa (MLO) were found similar over the monitoring period until March 2019, whereas δ ¹⁸ O‐CO ₂ showed unclear trend. Seasonal patterns at LLN and DSI reflect distinct influences from different regions. At LLN, daytime photosynthesis reduced CO ₂ , whereas CH ₄ rose in the afternoon caused by the influences associated with upslope valley breezes. We also observed an enlarging diurnal amplitude of CH ₄ with a significant large growth rate of 9.2 ppb yr ⁻¹ in the afternoon, which was plausibly owing to the intensified upslope winds at LLN. Based on the measurements associated with backward trajectories during nighttime, Southeast Asian biomass burning enhanced 1.5 ppm (+0.4%) of CO ₂ and 15.4 ppb (+0.8%) of CH ₄ at LLN in spring. Concentration weighted trajectory identifies potential source areas along the westerlies passing through southern China and Thailand, with reduced contributions from southern Southeast Asia as a result of mixing with the air in the South China Sea.

This study aimed to develop a technique to chemically characterize odor issues in neighborhoods of designated industrial zones with pronounced emissions of volatile organic compounds (VOCs). Due to the elusive nature of odor plumes, speedy detection with sufficient sensitivity is required to capture the plumes. In this demonstration, proton-transfer-reaction quadrupole mass spectrometry (PTR-QMS) was used as the front-line detection tool in an industrial zone to guide sampling canisters for in-laboratory analysis of 106 VOC species by gas chromatography-mass spectrometry (GC-MS). A 10-day PTR field screening period was conducted to determine suitable trigger VOC species with exceedingly high mixing ratios that were also likely the culprits of foul odors. Twenty canister samples were then collected, triggered by m/z 43, 61 (ethyl acetate fragments), m/z 73 (methyl ethyl ketone), or m/z 88 (morpholine) in all cases. Internal consistency was confirmed by the high correlation of key species in the PTR and trigger samples. Several long-lived halocarbons were exploited as the intrinsic internal reference for quality assurance. Oxygenated VOCs (OVOCs) accounted for 15% - 75% of the total VOC mixing ratios in the triggered samples. However, EA and MEK, the most prominent OVOC species, did not appear to have common sources with morpholine, which presented with PTR peaks incoherent with the other OVOCs. Nevertheless, these distinctive OVOC plumes were consistent with the more than one type of odor reported by local residents. To contrast with the triggered sampling, random samples in the same industrial zone and roadside samples in a major metropolitan area were collected. The pronounced OVOC content in the triggered samples highlighted the advantage over random grab sampling to address odor issues. This study demonstrates that the combination of fast mass spectrometry and slow GC-MS can achieve sensitivity, speed, and chemical identification to tackle elusive odor issues.