Soluble iron nutrients in Saharan dust over the central Amazon rainforest

The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m−3), Fe(II) (16 ng m−3), Na (470 ng m−3), Ca (194 ng m−3), K (65 ng m−3), and Mg (89 ng m−3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the main source of soluble mineral nutrients

BTEX profile and health risk at the largest bulk port in Latin America, Paranaguá Port

Port-related activities have a detrimental impact on the air quality both at the point of source and for considerable distances beyond. These activities include, but are not limited to, heavy cargo traffic, onboard, and at-berth emissions. Due to differences in construction, operation, location, and policies at ports, the site-specific air pollution cocktail could result in different human health risks. Thus, monitoring and evaluating such emissions are essential to predict the risk to the community. Environmental agencies often monitor key pollutants (PM2.5, PM10, NO2, SO2), but the volatile organic carbons (VOCs) most often are not, due to its analytical challenging. This study intends to fill that gap and evaluate the VOC emissions caused by activities related to the port of Paranaguá — one of the largest bulk ports in Latin America — by characterizing BTEX concentrations at the port and its surroundings. At seven different sites, passive samplers were used to measure the dispersion of BTEX concentrations throughout the port and around the city at weekly intervals from November 2018 to January 2019. The average and uncertainty of BTEX concentrations (µg m−3) were 0.60 ± 0.43, 5.58 ± 3.80, 3.30 ± 2.41, 4.66 ± 3.67, and 2.82 ± 1.95 for benzene, toluene, ethylbenzene, m- and p-xylene, and o-xylene, respectively. Relationships between toluene and benzene and health risk analysis were used to establish the potential effects of BTEX emissions on the population of the city of Paranaguá. Ratio analysis (T/B, B/T, m,p X/Et, and m,p X/B) indicate that the BTEX levels are mainly from fresh emission sources and that photochemical ageing was at minimum. The cancer risk varied across the sampling trajectory, whereas ethylbenzene represented a moderate cancer risk development for the exposed population in some of the locations. This study provided the necessary baseline data to support policymakers on how to change the circumstances of those currently at risk, putting in place a sustainable operation

Observations of atmospheric monoaromatic hydrocarbons at urban, semi-urban and forest environments in the Amazon region

The Amazon region is one of the most significant natural ecosystems on the planet. Of special interest as a major study area is the interface between the forest and Manaus city, a state capital in Brazil embedded in the heart of the Amazon forest. In view of the interactions between natural and anthropogenic processes, an integrated experiment was conducted measuring the concentrations of the volatile organic compounds (VOCs) benzene, toluene, ethylbenzene and meta, ortho, para-xylene (known as BTEX), all of them regarded as pollutants with harmful effects on human health and vegetation and acting also as important precursors of tropospheric ozone. Furthermore, these compounds also take part in the formation of secondary organic aerosols, which can influence the pattern of cloud formation, and thus the regional water cycle and climate. The samples were collected in 2012/2013 at three different sites: (i) The Amazon Tall Tower Observatory (ATTO), a pristine rain forest region in the central Amazon Basin; (ii) Manacapuru, a semi-urban site located southwest and downwind of Manaus as a preview of the Green Ocean Amazon Experiment (GoAmazon 2014/15); and (iii) the city of Manaus (distributed over three sites). Results indicate that there is an increase in pollutant concentrations with increasing proximity to urban areas. For instance, the benzene concentration ranges were 0.237-19.6 (Manaus), 0.036-0.948 (Manacapuru) and 0.018-0.313 μg m-3 (ATTO). Toluene ranges were 0.700-832 (Manaus), 0.091-2.75 μg m-3 (Manacapuru) and 0.011-4.93 (ATTO). For ethylbenzene, they were 0.165-447 (Manaus), 0.018-1.20 μg m-3 (Manacapuru) and 0.047-0.401 (ATTO). Some indication was found for toluene to be released from the forest. No significant difference was found between the BTEX levels measured in the dry season and the wet seasons. Furthermore, it was observed that, in general, the city of Manaus seems to be less impacted by these pollutants than other cities in Brazil and in other countries, near the coastline or on the continent. A risk analysis for the health of Manaus' population was performed and indicated that the measured concentrations posed a risk for development of chronic diseases and cancer for the population of Manaus. © 2015 Elsevier Ltd

Observations of particulate matter, NO2, SO2, O3, H2S and selected VOCs at a semi-urban environment in the Amazon region

This research aims to assess air quality in a transitional location between city and forest in the Amazon region. Located downwind of the Manaus metropolitan region, this study is part of the large-scale experiment GoAmazon2014/5. Based on their pollutant potential, inhalable particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), hydrogen sulfide (H2S), benzene, toluene, ethylbenzene and meta-, orto-, para-xylene (BTEX) were selected for analysis. Sampling took place during the wet season (March–April 2014) and dry season (August–October 2014). The number of forest fires in the surroundings was higher during the dry wet season. Results show significant increase during the dry season in mass concentration (wet: <0.01–10 μg m−3; dry: 9.8–69 μg m−3), NH4 + soluble content (wet: 13–125 μg m−3; dry: 86–323 μg m−3) and K+ soluble content (wet: 11–168 μg m−3; dry 60–356 μg m−3) of the PM2.5, and O3 levels (wet: 1.4–14 μg m−3; dry: 1.0–40 μg m−3), indicating influence of biomass burning emissions. BTEX concentrations were low in both periods, but also increased during the dry season. A weak correlation in the time series of the organic and inorganic gaseous pollutants indicates a combination of different sources in both seasons and NO2 results suggest a spatial heterogeneity in gaseous pollutants levels beyond initial expectations. © 201