A carregar...
Projeto de investigação
Center for Environmental and Sustainability Research
Financiador
Autores
Publicações
Electrokinetic Remediation of PPCPs in Soil: Effect of operating parameters
Publication . Lopes, Vanda Varela; Guedes, Paula; Ribeiro, Alexandra
Reclaimed wastewater is an important source of water that complements the fragile and limited natural water sources, being widely used for irrigation of agricultural land, particularly in arid and semi-arid regions. Considerable levels of pharmaceuticals and personal care products (PPCPs), are found in effluents and in land fields irrigated with these “recycled waters”. Once in the soil, plants have the capacity to uptake, translocate and accumulate these compounds of emerging concern (CECs) in the edible parts of food crops. These can subsequently enter the food chain. This is of concern as some of these compounds act as endocrine disruptors.
The main objective of the present dissertation was to study and develop the electrokinetic process to promote CECs degradation using an agricultural soil as matrix. The developed technology was evaluated in terms of remediation efficiency and sustainability. For that, the soil was spiked with a 16 mg/kg solution containing five CECs. The selected compounds were: sulfamethoxazole (SMX), ibuprofen (IBU), triclosan (TCS), caffeine (CAF) and atenolol (ATN).
The feasibility of the electrokinetic (EK) process was evaluated by testing different operating modes, using graphite rods as electrodes. The main tested operating modes were: current intensity (CI); ON/OFF switch intervals (Sw); and reversed electro-polarization intervals (RP). For CI mode, 100, 50 and 10 mA were tested, for 24h ON in the case of CI-10 and 24h ON/OFF for CI-100 and CI-50. For Sw and RP systems (performed at 10 mA), periods of 6, 12 and 24h were tested. All experiments were carried out for a 7 day period, in a lab scale microcosms. Additionally, two complementary reference testes were done: initial control and control after 7 days, both without direct current (DC) electric field.
Experiment CI-50 showed high degrading percentages for some compounds (97 ± 8% of SMX and 61 ± 5% of IBU), but the electrodes were unstable and presented high signs of corrosion after 24h of 50 mA application. Experiment CI-10 presented the highest degrading percentage of TCS (56 ± 0%), but a significant soil pH gradient was observed (6.8-11.2). The results with periodic current application of 12h (Sw system) showed to be the most viable option for achieving the CECs degradation without submitting the soil to extreme physico-chemical changes. Removal efficiencies in experiment Sw-12h ranged between 36 and 72% (with RSD from 0 to 10%). Although. In this system, the electrolysis of water produced a subtle pH gradient. The slight physico-chemical changes promoted in the soil, may have enabled, to some extent, the solubilization and/or mobilization of contaminants under study. This may have enhanced the degradation of contaminants by two remediation mechanisms: (i) electrochemical degradation and (ii) bioremediation. The EK process shows to be a sustainable option for the remediation of CECs in clay soils, thus decreasing the environmental and humans associated risks.
Beyond width and density
Publication . Costa, Augusta; Cherubini, Paolo; Graça, José; Spiecker, Heinrich; Barbosa, Inês; Máguas, Cristina; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; PeerJ Inc.
As climate change increasingly affects forest ecosystems, detailed understanding of major effects is important to anticipate their consequences under future climate scenarios. The Mediterranean region is a prominent climate change hotspot, and evergreen cork oak (Quercus suber L.) woodlands are particularly climatically sensitive due to cork (bark) harvesting. Cork oak's drought avoidance strategy is well-known and includes structural and physiological adaptations that maximise soil water uptake and transport and limit water use, potentially leading to reduced stem and cork growth. Trees' responses to cope with water-limited conditions have been extensively described based on cork-rings width and, more recently, on cork-rings density, in dendroecological studies. However, so far, tree functional attributes and physiological strategies, namely photosynthetic metabolism adjustments affecting cork formation, have never been addressed and/or integrated on these previous cork-rings-based studies. In this study, we address the relation between carbon and oxygen stable isotopes of cork rings and precipitation and temperature, in two distinct locations of southwestern Portugal-the (wetter) Tagus basin peneplain and the (drier) Grândola mountains. We aimed at assessing whether the two climatic factors affect cork-ring isotopic composition under contrasting conditions of water availability, and, therefore, if carbon and oxygen signatures in cork can reflect tree functional (physiological and structural) responses to stressful conditions, which might be aggravated by climate change. Our results indicate differences between the study areas. At the drier site, the stronger statistically significant negative cork δ13C correlations were found with mean temperature, whereas strong positive cork δ18O correlations were fewer and found only with precipitation. Moreover, at the wetter site, cork rings are enriched in 18O and depleted in 13C, indicating, respectively, shallow groundwater as the water source for physiological processes related with biosynthesis of non-photosynthetic secondary tissues, such as suberin, and a weak stomatal regulation under high water availability, consistent with non-existent water availability constrains. In contrast, at the drier site, trees use water from deeper ground layers, depleted in 18O, and strongly regulate stomatal conductance under water stress, thus reducing photosynthetic carbon uptake and probably relying on stored carbon reserves for cork ring formation. These results suggest that although stable isotopes signatures in cork rings are not proxies for net growth, they may be (fairly) robust indicators of trees' physiological and structural adjustments to climate and environmental changes in Mediterranean environments.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/AMB/04085/2013