Hugo Ribeiro
Environmental Sciences Researcher
* Petroleum Hydrocarbons Rhizoremediation in Salt Marshes
In the last decades, levels of petrochemical products in the environment, particularly in estuaries and coastal areas have increased.
Beside huge oil spills, salt marshes may become contaminated by petroleum hydrocarbons (PHC) in a number of ways; from municipal and industrial wastewater discharges, chronically by frequent small leakages and spills from commercial and recreational boating, urban runoff from land-based traffic accidents, major shipping accidents, and from offshore production facilities.
Rhizoremediation is a root plant-assisted bioremediation. In order to understand the PHC rhizodegradation potential by salt marsh plants, research has been performed in Lima River Estuary (Figures) and published (e.g. Ribeiro et al. 2011, 2013, 2014, 2015).
* Effect of Petroleum Hydrocarbons in the Nitrogen Cycle Processes
Anthropogenic dissolved N compounds entering estuarine and coastal waters from land, rivers, and atmosphere has increased dramatically across the globe in the past few decades. Additionally, PHC may affect critical processes of N-cycle in the environment, fundamental for optimal functioning of the ecosystems. Therefore, understanding the link between C and N cycling processes in oil spill incidents is extremely important.
Evaluation of oil spills and their interrelationships with N-Cycle processes in coastal and estuarine sediments is an important environmental concern and represents a new perspective of N cycle investigations.
The effect of crude oil in denitrification and anammox processes, which are important natural N removal processes that reduce external N loads delivered to coastal ecosystems, was assessed in previous studies (Figure - Adapted graphical abstract from Ribeiro et al. 2016).
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* Anaerobic Biodegradation of Polycyclic Aromatic Hydrocarbon
Polycyclic aromatic hydrocarbons (PAHs) are formed during incomplete combustion or pyrolysis of organic compounds like those found in coal, oil, and wood. The US EPA identified 16 PAHs of most concern based on their ecotoxicity and potential carcinogenicity.
There is still a lack of knowledge about the anaerobic metabolism of PAHs degradation, including the pathways and microbial communities involved and the significance of those metabolic pathways in natural ecosystems.
In order to understand the PAHs degradation potential under nitrate-reducing conditions, research has been performed (e.g. Ribeiro et al. 2018) to assess several PAHs considered priority to US EPA (figures).
* Genomic Shifts, and Metabolic and Functional Features of Prokaryotic.
Microbial changes can be investigated at the genomic level using a combination of qualitative and quantitative analysis targeting key genes involved in N-cycle pathways and also key genes involved in hydrocarbons degradation.
Several molecular biology techniques, including next-generation sequencing (NGS), combined with powerful bioinformatics analysis, provide an opportunity to study functional content, and therefore an understanding of the microbial hydrocarbon degradation processes and effects and changes on
N-cycle processes (e.g. Ribeiro et al. 2018).
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* Nitritation-Anammox Bioreactors at Ambient Temperature
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The application of anammox pathway in N-removal bioreactors working at ambient temperature has not been properly explored and could represent an advantage by improving the energy efficiency in WWTPs.
The microbial community composition, dynamics, and biogeochemistry during the start-up of a partial nitritation-anammox pathway in a laboratory upflow reactor (Figure) working at ambient temperature was studied by Ribeiro et al. (2022). The findings of this study provide a better understanding of the N-removal by key microbial groups that may be useful to optimize systems working at ambient temperature.
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* Nitrifying Biofilters in Recirculating Aquaculture Systems
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In Aquaculture facilities using water recycling, there is a build-up of ammonia and nitrite, which are harmful to fish health.
The elimination of these "pollutants" is achieved by autotrophic bacteria (usually in the form of a biofilm) that carry on the process of nitrification, which involves the conversion of ammonia to nitrite and nitrite to nitrate.
One type of aerobic biofilter used in RAS is the Moving Bed Biofilm Reactor (MBBR), which utilizes vigorous aeration and moving free carriers.
The video shows an attempt to simulate a MBBR, and study the potential of carriers collected from a real aquaculture biofilter to assess nitrification potential rates and understand nitrifying biofilm performance (Ribeiro 2008, MSc dissertation).
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* Biogeochemical Cycles Interactions
The interplay between the major biogeochemical (C, N, S, and P) cycles (which have been altered by human activity) have been poorly characterized and can outweigh their individual greenhouse gas (GHG) emissions, such as the CO2, N2O, CH4.
The interaction of denitrification (N cycle process) with high load organic carbon, such as PHC, was studied by Ribeiro et al. (2016). The lower N2O emission with PHC shows that potential biogeochemical interactions might have importance in global climate change.
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* Degradation of Biodiesels and Blends with BTEX
Biodiesel is typically a mixture of several fatty acid methyl esters (FAME) that can be produced from several sources including sugarcane, sugar beet, waste vegetables oils and animal fats.
Furthermore, biodiesel can be blended with a variety of hydrocarbons, including toxic mono-aromatics such as BTEX (benzene, toluene, ethylbenzene, xylene). Biodegradation of these mixtures have received little attention, and contradictory results were reported under aerobic conditions
Studies, particularly under methanogenic (Portugal et al. 2017) and nitrate-reducing conditions (Ribeiro et al. 2018) were performed to examine biodiesels and blends anaerobic biodegradation.
* Microbial Ecology in Polar Regions
The study of interrelationships between microorganisms and the living and non-living aspects of the Polar environments, Arctic and Antartida, provide a unique perspective of the processes driving biogeochemical cycles in extremely cold temperatures and "pristine" environments.
In this scope, the study of Sousa et al. (2019) provides comprehensive new knowledge about the microbiota in a thin Arctic sea ice regime, north of Svalbard. Surprisingly, this study found a high relative abundance of hydrocarbonoclastic bacteria.
On the other side, in Antarctica, the study of Rego et al. (2019) focused on the Actinobacteria and Cyanobacteria diversity along with different soil, particularly with different water availability, and endolithic microenvironments collected in the hyper-arid desert of Victoria Valley, McMurdo Dry Valleys. Also in Antarctica, the study of Santos et al. (manuscript in preparation) focused on the bacterial community structure in Antarctica Fildes Peninsula soils with different levels of metal and organic compounds.
* Development and Validation of Biological Monitoring Systems
Life in marine, coastal and estuarine environments is dominated by a vast diversity and abundance of microorganisms, including bacteria, archaea, unicellular eukaryotes.
In the scope of the project "MarinEye", a prototype (video) for multitrophic oceanic monitoring was developed (Martins et al. 2016). This prototype encloses an automatic bio-sampler system, which was developed and validated (Ribeiro et al. 2019b) by analyzing the reproducibility, comparing to standardized methods, of the prokaryotic and
the eukaryotic communities results obtained by next-generation sequencing.