Uxafores

In March, Cristina Álvarez Esmorís from the University of Vigo defended her PhD thesis, entitled “Processes of degradation, adsorption and desorption of three antibiotics in crop soils of Galicia”. This doctoral research was conducted under the guidance of Manuel Arias Estévez (UVigo) and Esperanza Álvarez Rodríguez, coordinator of the UXAFORES research group.

The research reported in the thesis aimed to improve knowledge about the problems related to the use of antibiotics. Although antibiotics have contributed to reducing mortality and morbidity rates in humans and animals, their massive use has led to them being present in different environmental compartments. Antibiotics are currently considered emergent pollutants because they can cause significant risks to human and environmental health, such as the emergence of antibiotic resistant bacteria, ecotoxicity-related problems and entry in the food chain. Doxicicline, sulfametoxipiridazine and enrofloxacin are three of the antibiotics most commonly used to treat and prevent infections in humans, animals and plants. These medicines are scarcely absorbed by human and animal intestines, which is why a high percentage of the compounds -up to 80%- is excreted as the original substance through faeces and urine. The use of sludges and slurry as fertilizers is therefore a possible route of entry of antibiotics to the soil. Once in the soil, the antibiotics can undergo degradation and adsorption/desorption processes. These processes, which depend on the antibiotic characteristics and the soil properties, determine the persistence of the antibiotics in the environment, their bioavailability and their transfer to water, to crops and, consequently, to the trophic chain. Therefore, knowledge about the factors responsible for degradation and adsorption/desorption processes in the soil is essential to determine the soil vulnerability. The objective of this PhD research was to determine the dynamics of the above-mentioned antibiotics in crop soils, by studying the degradation process under conditions of simulated light and with different pH values and adsorption/desorption capacities, focusing on the role of pH and soil organic matter. The research findings contribute further knowledge about the behaviour of these three antibiotics in soil, specifically under different acid-basic conditions and different organic matter contents. This knowledge can be used to help control migration of antibiotics to water and the trophic chain, with important repercussions in public health and the environment.

In April, Aurora Romar Gasalla from the USC defended her PhD thesis, entitled “Adsorption and desorption of phosphorus and trace elements in soils and bioadsorbents”, under the guidance of Esperanza Álvarez Rodríguez and María J. Fernández Sanjurjo, both members of UXAFORES.

In this case, the objective of the research was to study the presence in the soil of high quantities of elements such as phosphorus (P) and certain heavy metals/metalloids (Cd, Pb, Ni, Cr, As, F) that can have toxic effects in soil and water. The study of decontamination methods, including the adsorption of P and trace elements in soils and different industrial residues/by-products (mussel shells, biomass ash, pine bark, pine sawdust, slate waste, hemp, wheat straw) that could work as bioadsorbents. The results depend on the pollutant, the bioadsorbent and the pH. Addition of bioadsorbents improves the edaphic retention capacity of the soil. The results depend on the pollutant, the bioadsorbent and the soil pH. The research findings are useful for the management of degraded areas and recycling waste/by-products, contributing to environmental and human health.