Application of IoT technologies in a prototype sensor for air quality monitoring in the city of Cartagena with a focus on identifying improvement strategies

Abstract

This study presents the development and application of a low-cost IoT prototype for air quality monitoring in the city of Cartagena, Colombia. The system integrates an ESP32 microcontroller, an Arduino UNO, MQseries gas sensors, and a DHT temperature and humidity sensor for data acquisition, processing, and transmission to the ThingSpeak platform. Measurements were collected at four urban locations representing different environmental and mobility conditions: Mamonal, the Historic Center, the Transportation Terminal, and Crespo. The recorded data were analyzed using descriptive statistics and compared according to the airquality index estimated by the prototype. The results showed higher recorded air-quality index values in Mamonal and the Transportation Terminal, areas characterized by industrial activity and high vehicular flow, respectively, while lower and more stable values were observed in the Historic Center and Crespo. However, these results are interpreted as measurements generated by the developed prototype rather than as direct equivalents of measurements obtained from certified reference stations, considering the sensitivity of low-cost MQ sensors to environmental conditions and the need for more extensive calibration and validation. The study demonstrates the feasibility of using IoT technologies as a low-cost exploratory tool for obtaining spatially distributed air-quality information and provides a basis for future improvements involving sensor calibration, longer monitoring periods, and comparison with reference monitoring stations.