Characterization of spatial-temporal distribution and microenvironment source contribution of PM_2.5 concentrations using a low-cost sensor network with artificial neural network/kriging techniques

Low-cost sensors (LCS) network is widely used to improve the resolution of spatial-temporal distribution of air pollutant concentrations in urban areas. However, studies on air pollution sources contribution to the microenvironment, especially in industrial and mix-used housing areas, still need to be completed. This study investigated the spatial-temporal distribution and source contributions of PM_2.5 in the urban area based on 6-month of the LCS network datasets. The Artificial Neural Network (ANN) was used to calibrate the measured PM_2.5 by the LCS network. The calibrated PM_2.5 were shown to agree with reference PM_2.5 measured by the BAM-1020 with R² of 0.85, MNE of 30.91%, and RMSE of 3.73 μg/m³, which meet the criteria for hotspot identification and personal exposure study purposes. The Kriging method was further used to establish the spatial-temporal distribution of PM_2.5 concentrations in the urban area. Results showed that the highest average PM_2.5 concentration occurred during autumn and winter due to monsoon and topographic effects. From a diurnal perspective, the highest level of PM_2.5 concentration was observed during the daytime due to heavy traffic emissions and industrial production. Based on the present ANN-based microenvironment source contribution assessment model, temples, fried chicken shops, traffic emissions in shopping and residential zones, and industrial activities such as the mechanical manufacturing and precision metal machining were identified as the sources of PM_2.5. The numerical algorithm coupled with the LCS network presented in this study is a practical framework for PM_2.5 hotspots and source identification, aiding decision-makers in reducing atmospheric PM_2.5 concentrations and formulating regional air pollution control strategies.