Project

African Dust and Biomass Burning over Yucatan (ADABBOY)

Goal: This project aims to identify the main sources of aerosol particles in the Yucatan Peninsula with a special focus on biomass burning and African dust particles. The first intensive sampling period will focus on the characterization of the BB plumes, whereas at the end of the campaign the Saharan dust plumes are more likely to be observed in the region. Marine aerosol particles and biological particles (both continental and maritime) are expected to be present during the whole sampling period.

Objectives:
1. Characterize the chemical composition of the aerosol particles arriving to Merida to infer their main sources.
2. Quantify the influence of BB particles in the air quality of Merida.
3. Determine the toxicity and the health risk of the aerosol particles in Merida.
4. Quantify the main sources of CCN and INPs around Merida.
5. Examine the influence of BB particles on the local hydrological cycle.
6. Estimate if mineral dust particles from the Saharan desert can reach Merida.
7. Identify the biological microorganism present in the Saharan dust and biomass burning plumes.
8. Contribute to the understanding of the impact of African Dust as part of the Caribbean Aerosol and Heath Network (CAHN): http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00142.1

Date: 17 March 2017 - 12 August 2017

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Project log

Luis A. Ladino
added a research item
Biomass burning (BB) emissions and African dust (AD) are often associated with poor regional air quality, particularly in the tropics. The Yucatan Peninsula is a fairly pristine site due to predominant trade winds, but occasionally BB and AD plumes severely degrade its air quality. The African Dust And Biomass Burning Over Yucatan (ADABBOY) project (Jan 2017- Aug 2018) was conducted in the Yucatan Peninsula to characterize physical and biological properties of particulate pollution at remote seaside and urban sites. The 18-month long project quantified the large interannual variability in frequency and spatial extent of BB and AD plumes. Remote and urban sites experienced air quality degradation under the influence of these plumes, with up to 200 and 300% increases in coarse particle mass under BB and AD influence, respectively. ADABBOY is the first project to systematically characterize elemental composition of airborne particles as a function of these sources and identify bioaerosol over Yucatan. Bacteria, actinobacteria (both continental and marine) and fungi propagules vary seasonally and interannually and revealed the presence of very different species and genera associated with different sources. A novel contribution of ADABBOY was the determination of the ice-nucleating abilities of particles emitted by different sources within an under-sampled region of the world. BB particles were found to be inefficient ice nucleating particles at temperatures warmer than -20°C, whereas both AD and background marine aerosol activated ice nucleating particles below -10°C.
Luis A. Ladino
added a research item
Most precipitation from deep clouds over the continents and in the intertropical convergence zone is strongly influenced by the presence of ice crystals whose formation requires the presence of ice nucleating particles (INPs). Although there are a large number of INP sources, the ice nucleating abilities of aerosol particles originating from oceans, deserts, and wildfires are poorly described at tropical latitudes. To fill this gap in knowledge, the National Autonomous University of Mexico micro-orifice uniform deposit impactor droplet freezing technique (UNAM-MOUDIDFT) was constructed to measure the ice nucleating activity of aerosol samples that were collected in Sisal and Mérida, Yucatán (Mexico) under the influence of cold fronts, biomass burning (BB), and African dust (AD) intrusions during five short-term field campaigns between January 2017 and July 2018. The three different aerosol types were distinguished by their physicochemical properties. Marine aerosol (MA), BB, and AD air masses were found to contain INPs; the highest concentrations were in AD (from 0.071 to 36.07 L−1 at temperatures between −18 and −27 ◦C), followed by MA (from 0.068 to 18.90 L−1 at temperatures between −15 and −28 ◦C) and BB (from 0.063 to 10.21 L−1 at temperatures between −20 and −27 ◦C). However, MA had the highest surface active site densities (ns) between −15 and −30 ◦C. Additionally, supermicron particles contributed more than 72 % of the total INP concentration independent of aerosol type.
Luis A. Ladino
added a research item
On a global scale, African dust is known to be one of the major sources of mineral dust particles, as these particles can be efficiently transported to different parts of the planet. Several studies have suggested that the Yucatán Peninsula could be influenced by such particles, especially in July, associated with the strengthening of the Caribbean low-level jet. Although these particles have the potential to significantly impact the local air quality, as shown elsewhere (especially with respect to particulate matter, PM), the arrival and impact of African dust in Mexican territory has not been quantitatively reported to date. Two short-term field campaigns were conducted to confirm the arrival of African dust on the Yucatán Peninsula in July 2017 and July 2018 at the Mérida atmospheric observatory (20.98∘ N, 89.64∘ W). Aerosol particles were monitored at ground level using different online and off-line sensors. Several PM2.5 and PM10 peaks were observed during both sampling periods, with a relative increase in the PM levels ranging between 200 % and 500 % with respect to the normal background conditions. Given that these peaks were found to be highly correlated with supermicron particles and chemical elements typically found in mineral dust particles, such as Al, Fe, Si, and K, they are linked with African dust. This conclusion is supported by combining back trajectories with vertical profiles from radiosondes, reanalysis, and satellite images to show that the origin of the air masses arriving at Mérida was the Saharan Air Layer (SAL). The good agreement found between the measured PM10 concentrations and the estimated dust mixing ratio content from MERRA-2 (Version 2 of the Modern-Era Retrospective analysis for Research and Applications) corroborates the conclusion that the degradation of the local (and likely regional) air quality in Mérida is a result of the arrival of African dust.
Luis A. Ladino
added a research item
Biomass burning from grassland, forests, and agricultural waste results in large amounts of gases and particles emitted to the atmosphere, which affect air quality, population health, crop development, and natural vegetation. Regional atmospheric circulations can transport those plumes of pollutants over hundreds of kilometers, affecting vulnerable environments such as those considered protected natural areas (PNAs). This study evaluates the spatiotemporal distribution of active fires detected, and associated emissions, in central and southern Mexico from satellite data between March and June 2017, to assess the impact of the smoke plumes on protected ecosystems. The arrival of smoke plumes to selected PNAs (both near large urban centers and in remote areas) is assessed using airmass forward trajectories from selected emission sources. The spatial distribution of the remotely derived aerosol optical depth confirms the regional impact of particle emissions from the observed fires on PNAs, particularly in central Mexico. The identified areas of high fire density are also associated with large coarse particle concentrations at the surface. Moreover, there is a significant contribution of organic carbon to the total coarse particle mass, 60% on average. Finally, while most of the impact in ambient pollution is observed in PNAs located close to the regions with active fires in southern Mexico and Central America, the long-range transport of smoke plumes reaching the USA was also confirmed.
Luis A. Ladino
added a research item
This study focuses on the air quality evaluation of Merida, a medium-size city located in the Yucatan Peninsula with a significant population growth in recent years. Particle-bound Polycyclic Aromatic Hydrocarbons (pPAHs) were quantified with a real time sensor during a six-month period during the dry season (October 2017 to March 2018). The pPAHs diurnal and monthly characteristics, as well as their potential sources were determined. The total pPAHs concentrations ranged from 7 ng m-3 to 170 ng m-3, with an average value of 19 ± 11 ng m-3. A seasonal trend was observed, albeit not complete, indicating that pPAHs concentrations were higher during the colder months (October through January) than in February and March. The diurnal cycle showed a bimodal behavior similar to those found for carbon monoxide (CO), nitrogen oxides (NOx) and black carbon (BC) (estimated from absorption coefficient), indicating that burning of fossil fuels from vehicular traffic is the likely source of the pPAHs emitted in Merida. Moreover, atypical nocturnal values were observed, where the high pPAHs concentration could be associated with burning of solid waste. The average pPAHs concentration obtained in this study (19 ± 11 ng m-3) were found to be lower than the values measured in two other sites in Mexico City (32 ng m-3 and 50 ng m-3), Boston (29 ng m-3), Los Angeles (88.3 ng m-3) and Quito (220 ng m-3).
Luis A. Ladino
added a research item
Most precipitation from deep clouds over the continents and in the intertropical convergence zone is strongly influenced by the presence of ice crystals, whose formation requires the presence of ice nucleating particles (INP). Although there are a large number of INP sources, the ice nucleating abilities of aerosol particles emitted from oceans, deserts, and wildfires are poorly described at tropical latitudes. To fill this gap in knowledge, the UNAM-MicroOrifice Uniform Deposit Impactor-Droplet Freezing Technique (UNAM-MOUDI-DFT) was built. Aerosol samples were collected in Sisal and Merida, Yucatan (Mexico) under the influence of cold fronts, biomass burning (BB), and African dust (AD), during five short-term field campaigns between January 2017 and July 2018. The three different aerosol types were distinguished by characterizing their physicochemical properties. Marine aerosol (MA), BB, and AD air masses were found to contain INP; the highest concentrations were found for AD (from 0.071 L−1 to 36.07 L−1), followed by MA (from 0.068 L−1 to 18.90 L−1), and BB (from 0.063 L−1 to 10.21 L−1). However, MA had the highest surface active site density (ns) between −15 °C and −30 °C. Additionally, supermicron particles contributed more than 72 % of the total INP concentration independent of aerosol type; MA had the largest contribution from supermicron particles.
Luis A. Ladino
added a research item
Aerosol particles have been shown to trigger cardiovascular and respiratory diseases in populations living in polluted regions, depending on their size and composition. Although fine aerosol particles have been found to reach the lungs and the blood stream, their acute effects are related to the fraction of ultrafine aerosol particles (i.e., UFPs, d < 0.1 μm). In the present study, the concentration of UFPs (d = 0.02–0.1 μm) was monitored in Merida (Yucatan) between April 2017 and July 2018. Additionally, the total aerosol particle concentration (d > 0.03 μm), PM10, PM2.5, criteria gases, and meteorological variables, were also monitored. The average UFPs concentration over the full sampling period was found to be 2070 ± 1831 cm-3, with events of peak concentrations as high as 55,117 cm⁻³. The average daily UFP profile is bimodal, with peak concentrations observed around 07:00 and 20:00 h LT. The correlation of the UFP with other measured variables suggests that the UFPs peaks observed in the morning and at night are likely caused by primary vehicular combustion particles. In contrast, atypical high concentrations of UFPs were occasionally observed around noon LT, which are likely of secondary origin and the result of new particle formation promoted by photochemistry. Overall, UFPs are the major contributor to the total particle number concentration, and they are likely an important contributor to PM2.5 in Merida during the morning hours, with clear anthropogenic sources.
Luis A. Ladino
added a research item
On a global scale, African dust is known as one of the major sources of mineral dust particles as they can be efficiently transported to different parts of the planet. Several studies have suggested that the Yucatan Peninsula could be influenced by such particles, especially in July, associated with the strengthening of the Caribbean low level jet. Although these particles have the potential to impact the local air quality significantly, as shown elsewhere (especially particulate matter, PM), the arrival and the impact of African dust into Mexican territory has not been quantitatively reported to date. Two short-term field campaigns were conducted to confirm the arrival of African dust onto the Yucatan Peninsula in July 2017 and July 2018 at the city of Merida atmospheric observatory (20.98° N 89.64° W). Aerosol particles were monitored at the ground level by different on-line and off-line sensors. Several PM2.5 and PM10 peaks were observed during both sampling periods, with a relative increase in the PM levels ranging between 200 % and 500 % with respect to the normal background. Given that these peaks were found to highly correlate with super micron particles and chemical elements typically found in mineral dust particles, such as Al, Fe, Si, and K, they are linked with African dust. This conclusion is supported by combining back trajectories with vertical profiles from radiosondes, reanalysis, and satellite images to show that the origin of the air masses arriving at Merida was the Saharan Air Layer (SAL). The good agreement found between the measured PM>sub>10 concentrations and the estimated dust mixing ratio content from MERRA-2 (Version 2 of the Modern-Era Retrospective analysis for Research and Applications) corroborates the conclusion that the degradation of the local (and likely regional) air quality in Merida is a result of the arrival of African dust.
Luis A. Ladino
added 2 research items
The concentration of biological particles in the atmosphere is widely variable because it depends on several meteorological and geographical factors. Meteorological conditions in tropical coastal cities are unique due to both marine and terrestrial influences that can strongly modify the concentration and diversity of airborne microorganisms. Nevertheless, very few studies have been conducted in tropical coastal cities. This study presents the comparative results from four field campaigns carried out between 2017 and 2018 in two tropical cities located in the Yucatan Peninsula (Mexico): Sisal (a village right on the coast) and Merida (the State capital, 48 km from the coastline). The concentration of bacteria and fungal propagules, in colony-forming units or CFU per m3, sampled in Merida and Sisal are not comparable despite their proximity (i.e., 48 km away); however, both show similar seasonality and inter-annual trends. The results indicate that terrestrial microbiota dominates over that of marine origin, and show that fungal propagules are the dominant microorganism present at both sites. Also, these results indicate that meteorological conditions in the rainy season are more favorable for the growth of microorganisms than dry cold conditions. The predominant culturable bacterial phylum sampled during the four field campaigns carried out in 2017 and 2018 in the Yucatan Peninsula were Actinobacteria, Firmicutes, and Proteobacteria. The fraction of bacteria that reacted to a Gram positive stain was 62% and to Gram negative 38%. The fungal propagules genera relative concentration varied between both sampling sites, with Cladosporium and Penicillium being the most common at the coast in Sisal and Aspergillus in Merida.
Luis A. Ladino
added an update
Preliminary results showing the arrival of the Saharan dust particles to Merida (Yucatan).Top) Time series of PM10 (blue) y PM2.5 (orange) for july/august 2018 showing the increase in PM at the arrival of the Saharan dust plumes to Merida. Bottom) Aerosol particle elemental analysis using X-Ray fluorescence showing the difference between the background and Saharan dust particle´s composition (Ramírez et al., 2018).
 
Luis A. Ladino
added an update
The arrival of biomass burning plumes from Central America and the south of Mexico were detected in Merida by the ADABBOY instrumentation during the March-May period. These plumes have shown to affect PM10 and likely the local air quality as shown in the attached Figure.
 
Luis A. Ladino
added an update
Luis A. Ladino
added a project goal
This project aims to identify the main sources of aerosol particles in the Yucatan Peninsula with a special focus on biomass burning and African dust particles. The first intensive sampling period will focus on the characterization of the BB plumes, whereas at the end of the campaign the Saharan dust plumes are more likely to be observed in the region. Marine aerosol particles and biological particles (both continental and maritime) are expected to be present during the whole sampling period.
Objectives:
1. Characterize the chemical composition of the aerosol particles arriving to Merida to infer their main sources.
2. Quantify the influence of BB particles in the air quality of Merida.
3. Determine the toxicity and the health risk of the aerosol particles in Merida.
4. Quantify the main sources of CCN and INPs around Merida.
5. Examine the influence of BB particles on the local hydrological cycle.
6. Estimate if mineral dust particles from the Saharan desert can reach Merida.
7. Identify the biological microorganism present in the Saharan dust and biomass burning plumes.
8. Contribute to the understanding of the impact of African Dust as part of the Caribbean Aerosol and Heath Network (CAHN): http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00142.1