Assessment of the Relationship between Land Surface Temperature and Air Pollutants in Visakhapatnam Urban Area, India: A Geospatial Approach

Abstract

Urbanization requires human comfort that leads to industrial growth that alters existing physical and atmospheric conditions and pollutes the environment. This study area covers 200 km2 located in the northeast of the Greater Visakhapatnam Municipal Corporation (GVMC). The study area is famous for industries as well as tourism due to its bowl-shape topography and rich wild flora and fauna. Study was carried out using Landsat-8 and Landsat-9 satellite data for the years 2018, 2021, and 2022 to assess land surface temperature (LST) and the impact of air pollutants to identify human health hotspots. Industrial and vehicular emissions release harmful gases such as CO2, CO, oxides of nitrogen, sulphur, and suspended particulate matter (SPM) into the atmosphere. The LST for 2018 and 2021 results are nearly the same while the LST for 2022 decreased relatively by 3°C. Data from the monitoring stations located at the Police Barracks, Gnanapuram, and Visakhapatnam Port-Trust show that the ambient air quality with its corresponding LST in the industrial area has been identified with high LST with a 0.67°C increase from 2018 to 2021. There is a decrease of nearly 2°C from 2021 to 2022 at the monitoring stations of the Police Barracks and Gnanapuram located in urban areas, whereas Visakhapatnam Port-Trust is located in the vicinity of industries. The poor Air Quality Index (AQI) is creating discomfort and reduction of visibility in the vicinity. The relative humidity for 2018 is 72%, for 2021 is 64%, and for 2022 is 76%, which causes feelings of stickiness and sweat, and in rare cases skin irritation was reported. The regression analysis of AQI with LST shows a negative correlation in April 2018 and a positive correlation in March 2021 and April 2022. This indicates that the prominent parameter PM10 in AQI contains both cooling and warming properties. The study was carried out on land surface temperature (LST) and the influence of air pollution and its impact on human health. Practical applications of LST are to identify the urban heat island (UHI) in order to predict micro- to macroclimate zones for urban human comfort and assessment of energy demand, and so on. The impact of air pollutants on LST affects human health. The research focuses on identifying human health hotspots. The LST and air pollutants are the major driving factors. The LST for 2018 and 2021 were comparatively same, while 2022 shows a decrease of LST 3°C. The ambient air quality data when overlaid on the resultant LST shows that Gnanapuram and the Police Barracks areas identified as human health hotspots. The wind speed levels are low, supporting heat retention on the surface. The relative humidity results in feelings of stickiness and sweat and some rare cases of skin irritation. In general, in 2021, the poor Air Quality Index (AQI) was creating discomfort and reduction of visibility in the vicinity. The relative humidity for 2018 was 72%, and for 2021 AQI values were high, thus creating discomfort. The prominent parameter in AQI, PM10, contains both cooling properties of sulphates and the warming nature of black carbon. Therefore, the LST with AQI shows a negative correlation in April 2018 and positive correlation in March 2021 and April 2022.