Component-specific information is crucial for identifying sources of PM2.5 in indoor environments. However, profiles of PM2.5 at various locations, including subway tunnels are limited. This study aimed to evaluate the relationships between PM2.5 and its component across tunnels, platforms, and outdoor environments at underground subway stations in Incheon. The study was conducted at six underground subway stations in Incheon. PM2.5 concentrations were measured twice at each station, simultaneously covering the tunnel, platform, and outdoor areas. Carbon (two types), ion (eight types), and metal components (20 types) were analyzed using each analytical instruments. The mean PM2.5 concentration in the tunnel was 33.0±15.7 μg/ m3, significantly higher than the concentrations observed on the platform (12.9±4.6 μg/m3) and outdoors (13.1±7.6 μg/m3). The proportion of total metal concentrations in PM2.5 was highest in the tunnel (57.8%), followed by the platform (22.2%) and outdoor areas (11.3%). Significant correlations between the platform and tunnel were observed for organic carbon, SO4 2–, NO3 –, NH4 +, Ba, Mn, Fe, and Se. Significant correlations between the platform and outdoor were observed for SO4 2–, NO3 –, NH4 +, and Ti, while the tunnel and outdoor showed correlations for SO4 2– and NH4 +. PM2.5 concentrations and total metal concentrations were highest in the tunnel. While PM2.5 concentrations on the platform and outdoors were similar, total metal concentrations were higher on the platform than outdoors. From the platform’s perspective, the concentrations of Ba, Mn, Fe, and Se were only associated with the tunnel, while SO4 2–, NO3 –, and NH4 + had tendency of correlations between both the tunnel and outdoors. The findings suggest that for platform PM2.5 concentrations, Ba, Mn, Fe, and Se may serve as indicators of tunnel-originating PM2.5, while SO4 2–, NO3 –, and NH4 + may serve as indicators for outdoor sources.

Previous task-based focus on form studies have shown that second language (L2) learners are strongly interested in lexis, which allows minimal attention for morphosyntax. A possible reason may be a lack of sufficient lexical knowledge crucial for completing a meaning-oriented task. In other words, from an L2 information processing perspective, learners may have limited attentional capacity to focus on the multiple aspects of a language, so they choose to focus on words as they express their meaning. But this leaves little attention for less salient and meaningful grammatical forms. Thus, this study investigated if providing learners with lexical assistance during a synchronous text-based computer-mediated communication (CMC) task would reduce their attention to lexis and divert that attention to morphosyntax. Twenty Korean learners of English performed a picture-based narrative task in dyads through online text chatting. While engaging in this task, one group of learners (n=10) was able to refer to a list of English words for the task, while the other group (n=10) was not. The findings showed no statistically significant differences between and within the groups. Possible explanations are discussed with suggestions for teaching and future research.