Quantifying the contribution of industrial zones to urban heat islands: Relevance and direct impact.

Industrial production activities are an important source of urban heat emissions. Quantifying the contribution of industrial zones to urban heat islands (UHIs) is crucial for urban planning and management. However, few studies have explored the quantitative relationship between land surface temperature (LST) and urban industrial zones (UIZs) at the urban scale, especially the direct impact of industrial expansion or contraction on LST. Linyi City, the largest city in Shandong Province, was selected as the study area. This study aims to analyze the spatial-temporal variation in the UIZs in Linyi City from 2013 to 2022, focusing on the quantitative relationship between LST and UIZs. Using remote sensing images, a novel spectral index (called the BCCSI) was constructed to identify factory buildings. The performance of the BCCSI was validated using five existing indices and Google Earth images. Over the past 10 years, the UIZ area of Linyi has increased by 137.16 km2. The UIZs in Linyi are mainly distributed in counties near the urban center, and counties with large UIZ areas are also hotspots for UIZ changes. Moreover, we found that the contraction or expansion of UIZs has obvious effects on LST. After the contraction (or expansion) of UIZs, the LST decreased (or increased) by 0.48 °C (0.39 °C). In addition, we found that there is an exponential relationship between LST and the industrial unit area (P value less than 0.01). This research is valuable for environmental assessment and fine management of industrial cities.