Study of the effect of pH, salinity and DOC on fluorescence of synthetic mixtures of freshwater and marine salts

In order to provide support for the discussion of the fate of organic matter in estuaries, a laboratory simulation was performed by changing freshwater ionic strength, pH and organic matter content. The change in spectroscopic characteristics caused by variations in salinity, pH and organic matter concentration in the filtered samples was observed by UV-Vis and fluorescence spectroscopy. The increase in emission fluorescence intensity of dissolved organic matter (DOM) due to increasing salinity (in the range 0 to 5 g l−1) is affected by the pH of the samples. The emission fluorescence intensity at the three maxima observed in the fluorescence spectra, is linearly correlated with dissolved organic carbon (DOC) concentration at several salinity values in the same sample. The increase in organic matter concentration caused a shift in the emission peak wavelength at 410 nm for several salinity values.We concluded that it is necessary to take into account the influence of salinity and pH on emission fluorescence of dissolved organic matter if it is to be used as a tracer in estuarine or near shore areas

Generalized finite element method for bridging fine-scale heterogeneity to the structural scale

Phenomena spanning multiple spatial scales and encompassing multiple physics disciplines of interest are prevalent in many modern engineering applications; structural or global failure is often caused by the onset of very local damage like cracks or shear bands. In the case of heterogeneous materials, damage evolution is governed by microstructural details that can be several orders of magnitude smaller than structural dimensions. The mathematical homogenization theory has been used extensively as a tool for analyzing multiscale response of heterogeneous materials. Available multiscale or homogenization-based schemes achieve coupling between scales of interest by the numerical solution of a macroscale boundary value problem using homogenized or upscaled properties from microscale problem solutions. However, a persistent limitation in these approaches is that the solution of the homogenized macroscale problem may misrepresent complex solution behavior in the vicinity of localized gradients or singularities due to structural loads or geometry. Understanding the true behavior of solution fields in these regions is necessary to quantify failure initiation and evolution, so the intrinsic coupling of material- and structural-level phenomena must be addressed. However, the fidelity required to capture physics at each scale is extraordinarily expensive under traditional analysis techniques. This study presents a Generalized Finite Element Method for the computational modeling of structures subjected to extremely localized thermo-structural loadings in the presence of material heterogeneity, a class of problems where homogenization-based approaches may be invalid. This method is based on the use of custom enrichment functions generated from the solution of fine-scale boundary value problems which can capture localized behavior due to material-scale effects on the coarse, structural scale via a partition of unity approach. This method experiences no restrictions on inter-compatibility and continuity among micro or local solutions, an issue which plagues many existing multiscale techniques. Furthermore, fine-scale problems are shown to be intrinsically and rapidly parallelizable. The method is demonstrated on several representative thermo-structural problems in order to examine its accuracy, efficiency, and flexibility

A generalized finite element method with global–local enrichments for the 3D simulation of propagating cohesive fractures

A novel numerical framework based on the generalized finite element method with global‑local enrichments (GFEMgl) is developed for the efficient 3D modeling of propagating fractures, in which a non-linear cohesive law is adopted to capture objectively the amount of dissipated energy during the process of material degradation without the need of adaptive remeshing at the macroscale or artificial regularization parameters. In the proposed scale-bridging strategy, the fine-scale solution provides the coarse-scale problem with information on localized damaged states as well as scale-bridging enrichment functions, thus enabling the accurate solution of the nonlinear global problem on coarse meshes. This is to be contrasted with the original GFEMgl approach based on linear elastic fracture mechanics in which the local solution field contributes to only the kinematic description of the global solution. The cohesive crack is capable of propagating through the interior of finite elements in virtue of the concept of partition of unity employed in the generalized finite element method (GFEM), and thus eliminating the need of interfacial surface elements to represent the geometry of discontinuities and the requirement of finite element meshes fitting the cohesive crack surface

Analytical methodologies for arsenic speciation in macroalgae: a critical review

Marine and estuarine macroalgae are increasingly used for direct consumption, due to its high content of essential nutrients. However, the toxicity of chemical forms of arsenic (As) present in macroalgae are becoming of great concern and an important research topic. This review will discuss the sophisticated analytical methodologies used for arsenic speciation, as well the investigation of cheaper and fit for purpose methods able to inform about the safety of macroalgae consumption. Furthermore, we will also discuss relevant speciation studies performed by various authors highlighting the methodologies and respective figures of merit for all components of As in macroalgae, not only inorganic As (iAs). Focusing on the steps prior to speciation, such as sample extraction and clean-up, it will be stressed the need to develop certified reference materials (CRMs) in order to assist in the validation of analytical methodologies for As speciation in macroalgae.publishe

Extractability and mobility of mercury from agricultural soils surrounding industrial and mining contaminated areas

This study focussed on a comparison of the extractability of mercury in soils with two different contamination sources (a chlor-alkali plant and mining activities) and on the evaluation of the influence of specific soil properties on the behaviour of the contaminant. The method applied here did not target the identification of individual species, but instead provided information concerning the mobility of mercury species in soil. Mercury fractions were classified as mobile, semi-mobile and non-mobile. The fractionation study revealed that in all samples mercury was mainly present in the semi-mobile phase (between 63 and 97%). The highest mercury mobility (2.7 mg kg-1) was found in soils from the industrial area. Mining soils exhibited higher percentage of non-mobile mercury, up to 35%, due to their elevated sulfur content. Results of factor analysis indicate that the presence of mercury in the mobile phase could be related to manganese and aluminum soil contents. A positive relation between mercury in the semi-mobile fraction and the aluminium content was also observed. By contrary, organic matter and sulfur contents contributed to mercury retention in the soil matrix reducing the mobility of the metal. Despite known limitations of sequential extraction procedures, the methodology applied in this study for the fractionation of mercury in contaminated soil samples provided relevant information on mercury's relative mobility

Comprehensive multidimensional liquid chromatography for advancing environmental and natural products research

Chromatography is the separation method of choice in most laboratories worldwide. Nonetheless, the increasing need to decode complex samples has created a demand for better separation skills. The addition of extra separation dimensions to a conventional liquid chromatography system was one of the ways to answer to this demand. Although very common in proteomics and polymer research, the use of Multidimensional Liquid Chromatography (MDLC) coupled to high-resolution detectors for separation and analysis of environmental and natural products samples has yet to receive the deserved attention. This article presents a critical review on the most prominent of these comprehensive MDLC methods for targeted and untargeted analysis of complex environmental and natural products samples. This article also discusses the practical aspects of applying peak capacity and orthogonality concepts in MDLC analysis of complex matrices. It also addresses the limitations and challenges ahead for advancing environmental and natural products research using comprehensive MDLC.Thanks are due to FCT/MCTES for the financial support to CESAM (UID/AMB/50017/2019) and project AMBIEnCE (PTDC/CTA-AMB/28582/2017), through national funds (OE). FCT/MEC and the European Social Fund are also acknowledged for a PhD grant (PD/BD/142931/2018) and an Investigator FCT Contract (IF/00798/2015).publishe

Biophysical and Biochemical Markers of Metal/Metalloid-Impacts in Salt Marsh Halophytes and Their Implications

As a major sink, estuarine/salt marsh ecosystem can receive discharges laden with myriads of contaminants including metals/metalloids from man-made activities. Two among the major consequences of metal/metalloid-exposure in estuarine/salt marsh ecosystem flora such as halophytic plants are: (a) the excessive accumulation of light energy that in turn leads to severe impairments in the photosystem II (PS II), and (b) metal/metalloids-accrued elevation in the cellular reactive oxygen species (ROS) that causes imbalance in the cellular redox homeostasis. On one hand, plants adopt several strategies to dissipate excessive energy hence eventually to avoid damage in the PS II and maintain optimum photosynthesis. On the other hand, components of the cellular redox system quickly respond to metal/metalloid-exposure, where plants try to maintain a fine-tuning among these components, and tightly control the level of ROS and its potential consequences. Herein, major insights into, and the significance and implications of important biophysical and biochemical markers in metal/metalloid-exposed halophytes are overviewed and also highlighted main aspects so far least explored in the present context. Discussion advocates to regularly monitor and integrate studies on the highlighted herein biophysical and biochemical markers taking into account the missing aspects such as essential and non-essential metal/metalloid-speciation, -availability, and -methylation, role of the obvious microbial activities, and a comparative account of the outcomes of the studies on mixture of metal/metalloid performed in laboratory and field conditions. Thus, consideration of these missing aspects in future studies on the subject can help us to: (a) unveil the status of the metal/metalloid-contamination and -impact; (b) understand adaptive responses of salt marsh halophyte to metals/metalloids, and also (c) to devise sustainable strategies for the environmental or ecosystem management and safety.info:eu-repo/semantics/publishedVersio

Influence of sex and age on PCBs accumulation in the commercial fish Chelon labrosus

Thicklip grey mullet, Chelon labrosus, is an important commercial fish species and has been studied worldwide. However, no recent studies have been made regarding polychlorinated biphenyls (PCBs) in wild C. labrosus. Due to that, the concentration of 13 PCBs congeners was measured in muscles and livers, of males and females, of C. labrosus of different ages, allowing the estimation of PCB bioaccumulation throughout the species lifespan, in the Mondego estuary, a southern European temperate estuary. Male muscle sample concentrations ranged from 32 to 96 ng g− 1 (lipid wt.) and in females from 32 to 62 ng g− 1 (lipid wt.). In male liver sample concentrations ranged from 106 to 158 ng g− 1 (lipid wt.), while female concentrations ranged from 88 to 129 ng g− 1 (lipid wt.). The most abundant congeners presenting higher percentages in all samples were CB 138, 153 and 180. No significant differences were found between the concentrations in both sexes, but muscle and liver PCB concentrations in males tended to increase with age whereas in females concentrations remained stable throughout the species lifespan. Significant differences were found between concentrations in muscle and liver

Exploring water-soluble organic aerosols structures in urban atmosphere using advanced solid-state 13C NMR spectroscopy

Water-soluble organic matter (WSOM) in air particles has profound effects on climate and human health. At the heart of this environmental significance of WSOM lies a complex set of compounds, of which a major fraction still often remains undeciphered. Yet, not all environmental problems require delving into the molecular-level identification of WSOM constituents. Understanding the contribution of different functional groups to whole aerosol WSOM composition offers a highly important structural dataset that enables a better representation of WSOM in climate studies. For the first time, advanced solid-state 13C nuclear magnetic resonance (NMR) techniques, including nearly quantitative 13C multiple cross polarization/magic angle spinning (multiCP/MAS), multiCP/MAS with dipolar dephasing, multiCP/MAS with 13C chemical shift anisotropy filter, and two-dimensional 1H−13C heteronuclear correlation (2D HETCOR), are applied to acquire an accurate quantitative structural description of whole aerosol WSOM collected in an urban atmosphere. Two urban aerosol WSOM samples collected in two short periods of time, under different wintry weather conditions, were investigated. NMR data successfully pinpointed the variability of whole aerosol WSOM composition, allowing to suggest source-specific structural characteristics for each sample in two short periods of time. A new structural model of urban aerosol WSOM was build based on this compositional data, showing the presence of three independent classes of compounds that vary both in content and molecular diversity within short periods of time: heteroatom-rich aliphatic (either chain or branched), carbohydrate-like moieties, and highly substituted aromatic units. These findings establish advanced solid-state NMR as a promising tool for probing the chemical structures of inhomogeneous aerosol WSOM in rapidly changing atmospheric conditions, allowing to resolve discrepancies between modeled and measured aerosol WSOM.Fulbright Scholar Program; NSF (Award No. 1726346).publishe

PCB bioaccumulationin three mullet species — A comparison study

Polychlorinatedbiphenyls(PCBs)arelipophiliccontaminantsthattendtoaccumulateinorganisms.PCBs weredetectedin Chelon labrosus, Liza aurata and Liza ramada, alongdifferentagegroups. L. ramada presentedthehighestconcentration,anditincreasedwithage,whereas C. labrosus and L. aurata concentration remainedconstant. L. ramada high concentrationcanbeattributedtoitsecologicalniche, since thisspeciesisabletoaccumulatePCBsalongitsdifferentagegroupseveninlowenvironmental contamination conditions.PCBs101,118,138,149,153,170and180werethecongenersthatmore contributed tothesespeciescontamination,beingPCB138and153thecongenerswithhigher concentration. Mulletsareedibleinmanycountries,beingimportantin fisheries andaquaculture. L. ramada is themostcommonmulletforcaptureandhumanconsumption.Allspeciespresented concentrations belowtheregulationlimitestablishbytheEuropeanUnion,andthereforesafeforhuman consumption.The authorswishtothankallthecolleaguesthathelpedinthe field and laboratorywork.ThisworkwassupportedbyFCT(Fundaçãopara a CiênciaeTecnologia)throughaPhDgrantattributedtoJ.Baptista (SFRH/BD/48262/2008),fundedbyProgramaOperacionalPotencial HumanoofQRENPortugalandbythe Portuguesebudgetthroughthe Ministry ofScienceTechnologyandEducation.P.Patoacknowledgesa postdoctoralfellowshipfromFCT(SFRH/BPD/35068/2007)