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• Most dramatic decreases in LST are found in inner-city infill/redevelopment sites. • Most drastic increases in LST are related to suburban residential and industrial growth. • Positive relationship between low-rise compact housing, manufacturing, and LST changes. • Negative relationship between high-rise apartment, parks, service activities and LST changes. This study investigates the effects of urban development and expansion on Land Surface Temperature (LST) changes from 2000 to 2018, using the Seoul Metropolitan area (SMA) as a case study area. Along with descriptive analysis, this study uses a spatial first-order difference model to statistically analyze the longitudinal relationship between land use features and LST, including impervious surface (IS), enhanced vegetation index (EVI), anthropogenic factors, and urban spatial and topographical factors as well as urban development types as influential factors on LST variations. Our findings support prior research indicating the cooling effects of vegetation and warming effects of imperviousness. We also found a positive association between detached housing units, manufacturing activities and LST changes and a negative relationship between apartment units, urban parks, service activities and LST changes. More importantly, substantial LST reduction was found in the large-scale high-rise apartment complexes redeveloped from the low-rise, detached housing sites in inner-city infill areas, contrasting with significant LST rise in the suburban new town development. We suggest redevelopment of inner-city low-rise compact areas into high-rise but greener blocks as a LST mitigation strategy, equipped with cooling strategies such as green infrastructure and climate-sensitive design considering local microclimate and natural ventilation. [ABSTRACT FROM AUTHOR]

• Diurnal patterns of pollutant concentrations were analyzed. • Different urban form factors contribute to the emission and dispersion of pollutants. • Our results showed that mixed land use areas had adverse impacts on air quality. • Highly polluted areas tended to have a consistent pollution level during the day. • Particulate concentrations alleviated in the evening and overnight. Despite the aggressive emission control efforts in Korea over the past decades, surface-level particulate matter (PM) concentrations have increased in Seoul since 2012. What remains unknown are the influences of urban form and their interactions with seasonal and cyclic changes. This study investigates the diurnal pattern of PM concentrations (PM2.5 and PM10) and their clustering patterns related to urban form factors in Seoul, Korea. Using data obtained from 802 environmental sensors distributed across the city from April 2020 to March 2021, we found the highest PM concentrations in high traffic–concentrated areas with high-rise buildings as well as areas characterized by high proximity to highways and high mixed land uses. Furthermore, diurnal differences in pollutant concentrations were more pronounced in high traffic–concentrated areas with high-rise buildings as opposed to the areas characterized by a larger fraction of residential apartment complexes. This study demonstrates that high-resolution environmental sensor data can provide more granular information regarding spatial distribution and diurnal patterns of PM, which can help inform more targeted intervention strategies. The findings also suggest that bundling of urban design strategies aimed at reducing traffic emissions while diluting traffic pollutants through dispersion could be effective in managing urban air quality problems in high-density cities. [ABSTRACT FROM AUTHOR]

• Ultrafine particles and black carbon concentrations were measured at different greenway designs. • Pedestrian exposure to air pollution was lower on greenway than on sidewalk. • Urban microenvironmental features, such as vegetation, could play a role. • Vertical separation might be important for reducing air pollution exposure. This study investigates whether different urban greenway designs can influence personal exposure to air pollutants in highly urbanized environments in Seoul, Korea. Mobile and in-situ measurements of ultrafine particles (UFP) and black carbon (BC) concentrations were conducted on three different types of urban greenway designs: 1) an at-grade greenway next to traffic; 2) an elevated greenway above (10−14 m) traffic; and 3) a sunken greenway below (2.5−3 m) traffic. Results from the mobile measurements showed that the UFP and BC concentrations were up to 30 % lower on all types of greenway than on sidewalks. This result was further confirmed by the in-situ measurement, which showed 47 % lower UFP concentrations in the sunken greenway and 80 % lower BC concentrations in the elevated greenway compared to the sidewalk. Pollutant concentrations also varied according to microenvironmental factors, such as land uses, height of surrounding buildings, nearby traffic, and vegetation. Our findings highlight the importance of considering air pollution exposure when designing urban greenways in highly urbanized environments. In particular, greenway designs that promote vertical separation from traffic sources might be crucial in mitigating air pollution exposure. The results of this study are based on data gathered over a six-day field measurement, and further studies over a longer time period are warranted to confirm our findings. [ABSTRACT FROM AUTHOR]