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Aerosol particles are an important part of the Earth system, but their concentrations are spatially and temporally heterogeneous, as well as variable in size and composition. Aerosol particles can interact with incoming solar radiation and outgoing long wave radiation, change cloud properties, affect photochemistry, impact surface air quality, and when deposited impact surface albedo of snow and ice, and modulate carbon dioxide uptake by the land and ocean. High aerosol concentrations at the surface represent an important public health hazard. There are substantial datasets describing aerosol particles in the literature or in public health databases, but they have not been compiled for easy use by the climate and air quality modelling community. Here we present a new compilation of PM2.5 and PM10 aerosol observations including composition, a methodology for comparing the datasets to model output, and show the implications of these results using one model. Overall, most of the planet or even the land fraction does not have sufficient observations of surface concentrations, and especially particle composition to understand the current distribution of aerosol particles. Most climate models exclude 10-30% of the aerosol particles in both PM2.5 and PM10 size fractions across large swaths of the globe in their current configurations, with ammonium nitrate and agricultural dust aerosol being the most important omitted aerosol types. The dataset is available on Zenodo (https://zenodo.org/records/10459654, Mahowald et al., 2024). [ABSTRACT FROM AUTHOR]

This study aimed to characterize their Spatio-temporal distribution of hydrological variables and plankton during neap tides in Bahía Magdalena, a subtropical lagoon south of the California Current. We compare data from surface and bottom waters of stations located inside the lagoon with those near the bay's mouth and between surface and bottom. The availability of nutrients and the chlorophyll-a are associated primarily with the intense upwelling activity in spring. Due to direct marine influence, this relationship was more significant at the inlet than inside the lagoon, especially at the bottom. During the intense upwellings marine influence is maintained even during neap tides. The wind probably causes the homogeneous distribution in most variables within the bay's surface; this may also contribute to the re-suspension of nutrients due to vertical water column mixing. Abiotic variables were not linearly related with zooplankton biovolume and the density of diatoms and dinoflagellates. Phytoplankton was composed mainly by the micro fraction and diatoms during spring and nanoplankton in the warmest season of the year; however, the strong upwellings at the spring's end caused a HAB composed for diatoms. Chlorophyll-a concentration and diatoms were more abundant inside the lagoon and could explain the lower nutrient concentration of that zone. Zooplankton biovolume seasonality differed from other years, with higher values during winter and a significant decreasing trend throughout the year, resulting from the phytoplankton variability. Upwelling and wind variability explains the high biological productivity observed over most of the year. [ABSTRACT FROM AUTHOR]

On March 24-26, 2015, the Chilean city of Copiapó (27° 22′ S, 70° 20′ W), located in the hyperarid Atacama Desert, suffered an intense flooding brought by an extreme, unique rainfall event with a 35-year record of daily precipitation. A receptor model (positive matrix factorization, version 5) analysis, applied to ambient PM10 chemical speciation from three short-term sampling campaigns, resolved four sources: crustal/road dust, sea salt, secondary sulfates, and emissions from Paipote copper smelter located 8 km east of Copiapó. Wind trajectories computed with US NOAA’s Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) supported the above source identification and explained variability in source contributions. It was found that crustal/road dust increased 50 μg/m3, in April 8-10, 2015, as compared with values in November 2014 and October-November 2015, respectively. This was the dominant PM10 source after the flooding and before debris were cleaned up, being on order of magnitude higher that the other source contributions. The Paipote copper smelter contributed with primary PM10 emissions and secondary sulfates; this combined contribution averaged 11.8 μg/m3. Sea salt contributions contributed an average of 3.3 μg/m3. In normal conditions, crustal/road dust averaged 2.9 μg/m3, but the other resolved sources also contributed with crustal elements as their emissions are transported by winds to Copiapó. The positive matrix factorization solution included an unresolved concentration of 7.4 μg/m3. The small number of samples and the lack of measurements of nitrate, ammonia, and organic and elemental carbon may explain this result. Hence, sources such as secondary nitrates and combustion sources plus fugitive dust from sources surrounding Copiapó might be included in that unresolved concentration. [ABSTRACT FROM AUTHOR]

The inhabitants of Santiago, Chile have been exposed to harmful levels of air pollutants for decades. The city's poor air quality is a result of steady economic growth, and stable atmospheric conditions adverse to mixing and ventilation that favor the formation of oxidants and secondary aerosols. Identifying and quantifying the sources that contribute to the ambient levels of pollutants is key for designing adequate mitigation measures. Estimating the evolution of source contributions to ambient pollution levels is also paramount to evaluating the effectiveness of pollution reduction measures that have been implemented in recent decades. Here, we quantify the main sources that have contributed to fine particulate matter (PM2.5) between April 1998 and August 2012 in downtown Santiago by using two different source-receptor models (PMF 5.0 and UNMIX 6.0) that were applied to elemental measurements of 1243 24 h filter samples of ambient PM2.5. PMF resolved six sources that contributed to ambient PM2.5, with UNMIX producing similar results: motor vehicles (37.3±1.1 %), industrial sources (18.5±1.3 %), copper smelters (14.4±0.8 %), wood burning (12.3±1.0 %), coastal sources (9.5±0.7 %) and urban dust (3.0±1.2 %). Our results show that over the 15 years analyzed here, four of the resolved sources significantly decreased [95% confidence interval]: motor vehicles 21.3% [2.6, 36.5], industrial sources 39.3% [28.6, 48.4], copper smelters 81.5% [75.5, 85.9], and coastal sources 58.9% [38.5, 72.5], while wood burning did not significantly change and urban dust increased by 72%[48.9, 99.9]. These changes are consistent with emission reduction measures, such as improved vehicle emission standards, cleaner smelting technology, introduction of low-sulfur diesel for vehicles and natural gas for industrial processes, public transport improvements, etc. However, it is also apparent that the mitigation expected from the above regulations has been partially offset by the increasing amount of private vehicle use in the city, with motor vehicles becoming the dominant source of ambient PM2.5 in recent years. Consequently, Santiago still experiences ambient PM2.5 levels above the annual and 24 h Chilean and World Health Organization standards, and further regulations are required to reach ambient air quality standards. [ABSTRACT FROM AUTHOR]

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Wildfire causes multiple problems for people living in cities. One of them is the deterioration of air quality as a result of wildfire smoke. This smoke can consequently have effects on human health. The present study aims to characterize the relationship between the occurrence of wildfires in central Chile and the effects on children's respiratory health. Public databases provided the number of emergency care visits, wildfires, and concentration of air pollutants, demographics and meteorological variables for the regions of Santiago and Valparaiso from 2010 to 2013. Time series analysis was used monthly on health care visits to determine the relative health risk in children when in the presence of additional wildfires. Significant health risks were observed in Santiago for children younger than 1-year-old of bronchitis (RR 1.007, CI 95% 1.007–1.008; chronic lower respiratory diseases (RR 1.012, CI 95% 1.012–1.013); and pneumonia (RR 1.026 CI 95% 1.026–1.027) and in children aged one to four years old (RR 1.016 CI 95% 1.015–1.016). A dose-response relationship was also observed for pneumonia, showing that it affects younger children particularly when there is an increase in the number of wildfires. In the Region of Valparaíso, wildfires did not significantly change the risk of respiratory illness, this could be due to favorable ventilation. Currently, Santiago has an urgent need for monitoring and the evaluation of the damage to children's respiratory health, along with the development of comprehensive prevention strategies. [ABSTRACT FROM AUTHOR]