Weekly rain samples were collected in coastal areas of the Shihwa Basin (Korea) from June 2000 to November 2007. The study region includes industrial, rural, and agricultural areas. Wet precipitation was analyzed for conductivity, pH, Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, K⁺, Mg²⁺, NH₄⁺, and Ca²⁺. The major components of precipitation in the Shihwa Basin were NH₄⁺, volume-weighted mean (VWM) of 44.6 µeq∙L⁻¹, representing 43% of all cations, and SO₄²⁻, with the highest concentration among the anions (55%) at all stations. The pH ranged from 3.4 to 7.7 with a VMM of 4.84. H⁺ was weakly but positively correlated with SO₄²⁻ (r = 0.39, p < 0.001) and NO₃⁻ (r = 0.38, p < 0.001). About 66% of the acidity was neutralized by NH₄⁺ and Ca²⁺. The Cl⁻/Na⁺ ratio of the precipitation was 37% higher than seawater Cl⁻/Na⁺. The high SO₄²⁻/NO₃⁻ ratio of 2.3 is attributed to the influence of the surrounding industrial sources. Results from positive matrix factorization showed that the precipitation chemistry in Shihwa Basin was influenced by secondary nitrate and sulfate (41% ± 1.1%), followed by sea salt and Asian dust, contributing 23% ± 3.9% and 17% ± 0.2%, respectively. In this study, the annual trends of SO₄²⁻ and NO₃⁻ (p < 0.05) increased, different from the trends in some locations, due to the influence of the expanding power generating facilities located in the upwind area. The increasing trends of SO₄²⁻ and NO₃⁻ in the study region have important implications for reducing air pollution in accordance with national energy policy.

Our study analyzed PM_2.5 concentrations in Porto Velho, Rondônia, during the April 2020 and October 2022 wildfire seasons. This study aimed to evaluate the temporal characteristics of PM_2.5 and the influence of long-distance pollution sources. Using PurpleAir data, we found that the average PM_2.5 concentration was 17.7 ± 24.0 µg m⁻³, with significant spikes in August. PM_2.5 concentrations decreased during the day but rose from nighttime to morning. The PM_2.5 concentration was observed to be distributed at a high level of 36.3 ± 31.1 µg m⁻³ in slow westerly winds. Moreover, even in the dominant northerly wind conditions, a similarly high concentration of PM_2.5 was detected, measuring at 33.2 ± 28.3 µg m⁻³. Air masses mainly originated from northeastern, southeastern, and southern regions, passing through Paraguay and Bolivia. Furthermore, PM_2.5 in Porto Velho was influenced by Brazil’s northern and Central-West areas. To meet the Sustainable Development Goal (SDG) Indicator 11.6.2 for clean air, it is recommended that wildfires in Porto Velho’s northern and western regions be reduced, and more robust deforestation policies are needed in areas with long-distance pollution sources.

We performed continuous long-term measurements of PM_2.5 mass, comprehensive chemical composition, and optical properties, including scattering and absorption coefficients, from March 2011 to December 2020 at the Metropolitan Air Quality Research Center in Seoul, South Korea. PM_2.5 peaked at 38 μg/m³ in 2013 and has been declining steadily since then, reaching 22 μg/m³ in 2020. The extinction coefficients also decreased with the decline in PM_2.5, but the correlation between the two factors was not as pronounced. This deviation was mainly attributed to the rapid changes in the chemical composition of PM_2.5 over the same period. The mass contribution of sulphate to PM_2.5 decreased from 33.9 to 24.1%, but the fraction of nitrate and organic carbon increased from 23.4 and 20.0 to 34.1 and 32.2%, respectively, indicating that sulphate has been replaced by nitrate and organic carbon over the past decade. To assess the effect of changing aerosol chemical compositions on light extinction, we compared the measured extinction coefficients with those estimated via the various existing light extinction approaches, including the revised IMPROVE algorithm. We found that the simplified linear regression model provided the best fit to our data, with a slope of 1.03 and R² of 0.87, and that all non-linear methods, such as the IMPROVE algorithms, overestimated the observed long-term light extinction by 23 to 48%. This suggests that the simple linear regression scheme may be more appropriate for reflecting the varying aerosol conditions over long periods of time, especially for urban air. However, for conditions where the chemical composition does not change much, non-linear methods such as the IMPROVE scheme are likely to be more appropriate for reproducing light extinction.

브라질은 기후변화 완화를 위한 노력으로 기후변화에 관한 국가정책(PNMC)과 자발적 감축방안(NDC) 그리고 국가에너지계획 2050을 시행하고 있다. 브라질의 주요 온실가스 배출원은 토지이용과 농업 분야로서 전체 배출량의 72%를 기여하고 있다. 브라질 정부는 토지전용과 농업분야에서 삼림황폐화를 방지함으로써 온실가스 저감을 위한 정책들을 포함하고 있다. PNMC 정책의 일환으로 농업분야에서 저탄소 농업개발계획(ABC Plan)을 통해 온실가스를 1억7천톤을 저감하였지만, 여전히 화석연료에서 배출되는 온실가스보다 1.5배 많은 양을 배출하고 있다. NDC 정책의 경우 토지 전용으로 인한 온실가스는 2005년보다 40~65% 감축하였으나, 화석연료 사용으로 인한 온실가스는 오히려 증가한 것으로 평가되었다. 브라질 정부의 ‘에너지계획 2050’의 경우 비재생에너지 분야의 투자가 여전히 높은 점이 브라질 온실가스 저감과 상충되고 있으며, 바이오 연료를 교통분야와 수소 생산 분야에 확대하려는 정책 또한 삼림황폐화 방지 정책과 상충될 수 있다. 지속적인 삼림황폐화로 인한 스트레스 증가는 아마존 열대우림의 온실가스가 배출원으로서 역할을 하여 지구온난화를 가속화하는 양의 피드백을 형성할 수 있다. 따라서 2008년부터 2018년까지 아마존 열대우림의 삼림황폐화 방지에 기여해 온 아마존 기금의 정상화를 통한 국제협력이 필요하다.

Sustainable urban air quality in tropical cities is threatened by interactions between climate change, extreme drought, and long-range wildfire smoke transport. This study investigated the causes of PM_2.5 pollution in Manaus, Brazil, under El Niño conditions during the 2023 drought, focusing on long-range wildfire smoke transport. The links among hydroclimatic drying, wildfire activity, and urban air quality were examined using hourly PM_2.5 observations, meteorological data, long-term climate records, MODIS hotspot and fire radiative power (FRP) data, and air-mass trajectory analyses. Significant long-term warming, decreasing precipitation, and a declining standardized precipitation evapotranspiration index were observed around Manaus during 1981–2024, indicating persistent drying. In 2023, severe drought and increased wildfire activity caused an annual mean PM_2.5 concentration of 15.09 µg m⁻³. Directional analyses, upwind FRP, potential source contribution function, and backward trajectories consistently highlighted the eastern and southeastern source regions approximately 500–2200 km from Manaus. These results indicated that PM_2.5 levels were more sensitive to spatial alignment between upwind fires and prevailing winds than to total fire activity alone. In conclusion, the 2023 PM_2.5 surge was driven by long-range wildfire smoke transport under intensified drying and drought, with implications for urban sustainability, public health, and climate-resilient early warning systems.