Estudo da variabilidade sazonal da concentração dos materiais particulados totais em suspensão no município de Humaitá, Amazonas, Brasil

Abstract

The Amazon rainforest is an essential ecosystem for climate regulation and the global carbon cycle. However, it has experienced significant vegetation loss due to extreme climatic events, severe droughts, deforestation, and forest fires, which emit large amounts of atmospheric pollutants, affecting the regional climate and, especially, public health. This study aimed to analyze the seasonal variability of fine particulate matter concentrations (PM2.5) and (PM10) in the urban area of the municipality of Humaitá, Amazonas (Brazil), from August 2022 to November 2024, relating these pollutants to meteorological variables and fire hotspots. The concentrations were obtained using an automatic EcoPM station equipped with a laser optical particle counter (OPC). The data were analyzed using daily and monthly averages, descriptive tables, multiple linear regression with time lags, Pearson correlation, and comparison with the standards established by CONAMA Resolution No. 506/2024. Throughout the time series, a marked seasonality was observed, with 2024 presenting the highest monthly maximum concentration values (135.31 μg/m³ for (PM2.5) and 141.25 μg/m³ for (PM10), followed by 2022 (70.01 μg/m³ for (PM2.5) and 81.41 μg/m³ for (PM10), while 2023 showed the lowest records (42.18 μg/m³ for (PM2.5) and 57.05 μg/m³ for (PM10). The application of multiple linear regression showed that fire hotspots occur ring 1 to 2 days earlier had the greatest influence on particulate matter peaks, with coefficients β = 0.2446 and β = 0.2772, respectively, and an R² value of 0.30. This suggests a cumulative effect of pollutants combined with low atmospheric dispersion. The correlation between (PM2.5) and fire occurrences was extremely high (r = 0.997; R² = 0.993), while meteorological variables showed moderate to strong correlations, such as temperature (r = 0.586), precipitation (r = – 0.996), and relative humidity (r = –0.993), reinforcing the influence of climatic conditions on pollutant concentrations, especially during the dry season. In 2024, concentrations up to nine times higher than the daily limit recommended by legislation (15 μg/m³) were recorded, indicating episodes of poor air quality with potential health risks, particularly for vulnerable groups such as the elderly, children, and individuals with pre-existing diseases. Finally, the monitoring of fine particulate matter (PM2.5) and inhalable particulate matter (PM10) concentrations in the urban area of Humaitá-AM revealed a well-defined and recurrent seasonal pattern throughout the analyzed period (2022–2024), characterized by increased concentrations during the dry season and a significant reduction during the rainy months. Although statistically significant associations were observed among the analyzed variables, it is emphasized that these relationships represent statistical associations rather than direct causality, reflecting the simultaneous influence of multiple atmospheric processes.