Analytical Techniques for the in situ Measurement and Speciation of Trace Compounds in Natural Waters

A major research component of the analytical activities of the Analytical and Biophysical Environmental Chemistry group of the University of Geneva (CABE) is focused on the development of chemical sensors and mini or microanalytical systems for in situ measurements of trace compounds in aquatic environmental systems, including surface waters, sediments or water treatment plants. In this field, new concepts are required in order to determine not only the total concentration of environmental analytes but also the concentrations and physicochemical properties of their environmentally relevant chemical forms (chemical speciation). New selective analytical systems integrating reliable and rugged sensors with simple separation principles must be imagined to perform in situ (at depth), real-time, automatic measurements. Microtechnology is a key factor in such developments. New analytical methods must also be developed to characterize the nature and properties of the major natural, often colloidal or polymeric, complexing agents. In this context, the scientific approach of CABE is explained

Rigorous Physicochemical Framework for Metal Ion Binding by Aqueous Nanoparticulate Humic Substances: Implications for Speciation Modeling by the NICA-Donnan and WHAM Codes

Latest knowledge on the reactivity of charged nanoparticulate complexants toward aqueous metal ions is discussed in mechanistic detail. We present a rigorous generic description of electrostatic and chemical contributions to metal ion binding by nanoparticulate complexants, and their dependence on particle size, particle type (i.e., reactive sites distributed within the particle body or confined to the surface), ionic strength of the aqueous medium, and the nature of the metal ion. For the example case of soft environmental particles such as fulvic and humic acids, practical strategies are delineated for determining intraparticulate metal ion speciation, and for evaluating intrinsic chemical binding affinities and heterogeneity. The results are compared with those obtained by popular codes for equilibrium speciation modeling (namely NICA-Donnan and WHAM). Physicochemical analysis of the discrepancies generated by these codes reveals the a priori hypotheses adopted therein and the inappropriateness of some of their key parameters. The significance of the characteristic time scales governing the formation and dissociation rates of metal−nanoparticle complexes in defining the relaxation properties and the complete equilibration of the metal− nanoparticulate complex dispersion is described. The dynamic features of nanoparticulate complexes are also discussed in the context of predictions of the labilities and bioavailabilities of the metal species

Electrochemical methods for speciation of trace elements in marine waters. Dynamic aspects

The contribution of electrochemical methods to the knowledge of dynamic speciation of toxic trace elements in marine waters is critically reviewed. Due to the importance of dynamic considerations in the interpretation of the electrochemical signal, the principles and recent developments of kinetic features in the interconversion of metal complex species will be presented. As dynamic electrochemical methods, only stripping techniques (anodic stripping voltammetry and stripping chronopotentiometry) will be used because they are the most important for the determination of trace elements. Competitive ligand ex- change-adsorptive cathodic stripping voltammetry, which should be considered an equilibrium technique rather than a dynamic method, will be also discussed because the complexing parameters may be affected by some kinetic limitations if equilibrium before analysis is not attained and/or the flux of the adsorbed complex is in fluenced by the lability of the natural complexes in the water sample. For a correct data interpretation and system characterization the comparison of results obtained from different techniques seems essential in the articulation of a serious discussion of their meaning

Cardiovascular MRI Compared to Echocardiography to Identify Cardioaortic Sources of Ischemic Stroke: A Systematic Review and Meta-Analysis

Background: To compare the diagnostic yield of echocardiography and cardiovascular MRI (CMR) to detect structural sources of embolism, in patients with ischemic stroke with a secondary analysis of non-stroke populations. Methods and Results: We searched MEDLINE/Embase (from 01.01.2000 to 24.04.2021) for studies including CMR to assess prespecified sources of embolism. Comparison included transthoracic and/or transesophageal echocardiography. Two authors independently screened studies, extracted data and assessed bias using the QUADAS-2 tool. Estimates of diagnostic yield were reported and pooled. Twenty-seven studies with 2,525 patients were included in a study-level analysis. Most studies had moderate to high risk of bias. Persistent foramen ovale, complex aortic plaques, left ventricular and left atrial thrombus were the most common pathologies. There was no difference in the yield of left ventricular thrombus detection between both modalities for stroke populations (4 studies), but an increased yield of CMR in non-stroke populations (28.1 vs. 16.0%, P < 0.001, 10 studies). The diagnostic yield in stroke patients for detection of persistent foramen ovale was lower in CMR compared to transoesophageal echocardiography (29.3 vs. 53.7%, P < 0.001, 5 studies). For both echocardiography and CMR the clinical impact of the management consequences derived from many of the diagnostic findings remained undetermined in the identified studies. Conclusions: Echocardiography and CMR seem to have similar diagnostic yield for most cardioaortic sources of embolism except persistent foramen ovale and left ventricular thrombus. Randomized controlled diagnostic trials are necessary to understand the impact on the management and potential clinical benefits of the assessment of structural cardioaortic stroke sources. Registration: PROSPERO: CRD42020158787

Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers

"This is the peer reviewed version of the following article: Gottselig, N., W. Amelung, J. W. Kirchner, R. Bol, W. Eugster, S. J. Granger, C. Hernández-Crespo, et al. 2017. Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles 31 (10). American Geophysical Union (AGU): 1592 1607. doi:10.1002/2017gb005657, which has been published in final form at https://doi.org/10.1002/2017GB005657. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (similar to 1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 +/- 5% (Si) and 53 +/- 21% (Fe; mean +/- SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe-to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.The authors gratefully acknowledge the assistance of the following people in locating suitable sampling sites, contacting site operators, performing the sampling, and providing data: A. Avila Castells (Autonomous University of Barcelona), R. Batalla (University of Lleida), P. Blomkvist (Swedish University of Agricultural Sciences), H. Bogena (Julich Research Center), A.K. Boulet (University of Aveiro), D. Estany (University of Lleida), F. Garnier (French National Institute of Agricultural Research), H.J. Hendricks-Franssen (Research Center Julich), L. JacksonBlake (James Hutton Institute, NIVA), T. Laurila (Finnish Meteorological Institute), A. Lindroth (Lund University), M.M. Monerris (Universitat Politecnica de Valencia), M. Ottosson Lofvenius (Swedish University of Agricultural Sciences), I. Taberman (Swedish University of Agricultural Sciences), F. Wendland (Research Center Julich), T. Zetterberg (Swedish University of Agricultural Sciences and The Swedish Environmental Research Institute, IVL) and further unnamed contributors. The Swedish Infrastructure for Ecosystem Science (SITES) and the Swedish Integrated Monitoring, the latter financed by the Swedish Environmental Protection Agency, and ICOS Sweden have supported sampling and provided data for the Swedish sites. J.J.K. gratefully acknowledges the support from CESAM (UID/AMB/50017/2013), funded by the FCT/MCTES (PIDDAC) with cofunding by FEDER through COMPETE. N.G. gratefully acknowledges all those who contributed to organizing and implementing the continental sampling. The raw data can be found at http://hdl.handle.net/2128/14937. This project was partly funded by the German Research Foundation (DFG KL2495/1-1).Gottselig, N.; Amelung, W.; Kirchner, J.; Bol, R.; Eugster, W.; Granger, S.; Hernández Crespo, C.... (2017). Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles. 31(10):1592-1607. https://doi.org/10.1002/2017GB005657S159216073110Baken, S., Moens, C., van der Grift, B., & Smolders, E. (2016). Phosphate binding by natural iron-rich colloids in streams. Water Research, 98, 326-333. doi:10.1016/j.watres.2016.04.032Baken, S., Regelink, I. C., Comans, R. N. J., Smolders, E., & Koopmans, G. F. (2016). Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study. Water Research, 99, 83-90. doi:10.1016/j.watres.2016.04.060Benedetti, M. F., Van Riemsdijk, W. H., Koopal, L. K., Kinniburgh, D. G., Gooddy, D. C., & Milne, C. J. (1996). Metal ion binding by natural organic matter: From the model to the field. Geochimica et Cosmochimica Acta, 60(14), 2503-2513. doi:10.1016/0016-7037(96)00113-5Binkley, D., Ice, G. G., Kaye, J., & Williams, C. A. (2004). NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES. Journal of the American Water Resources Association, 40(5), 1277-1291. doi:10.1111/j.1752-1688.2004.tb01586.xBishop, K., Buffam, I., Erlandsson, M., Fölster, J., Laudon, H., Seibert, J., & Temnerud, J. (2008). Aqua Incognita: the unknown headwaters. Hydrological Processes, 22(8), 1239-1242. doi:10.1002/hyp.7049Bol, R., Julich, D., Brödlin, D., Siemens, J., Kaiser, K., Dippold, M. A., … Hagedorn, F. (2016). Dissolved and colloidal phosphorus fluxes in forest ecosystems-an almost blind spot in ecosystem research. Journal of Plant Nutrition and Soil Science, 179(4), 425-438. doi:10.1002/jpln.201600079Buffle, J., & Leppard, G. G. (1995). Characterization of Aquatic Colloids and Macromolecules. 2. Key Role of Physical Structures on Analytical Results. Environmental Science & Technology, 29(9), 2176-2184. doi:10.1021/es00009a005Celi, L., & Barberis, E. (s. f.). Abiotic stabilization of organic phosphorus in the environment. Organic phosphorus in the environment, 113-132. doi:10.1079/9780851998220.0113Dahlqvist, R., Benedetti, M. F., Andersson, K., Turner, D., Larsson, T., Stolpe, B., & Ingri, J. (2004). Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers. Geochimica et Cosmochimica Acta, 68(20), 4059-4075. doi:10.1016/j.gca.2004.04.007Darch, T., Blackwell, M. S. A., Hawkins, J. M. B., Haygarth, P. M., & Chadwick, D. (2014). A Meta-Analysis of Organic and Inorganic Phosphorus in Organic Fertilizers, Soils, and Water: Implications for Water Quality. Critical Reviews in Environmental Science and Technology, 44(19), 2172-2202. doi:10.1080/10643389.2013.790752Dynesius, M., & Nilsson, C. (1994). Fragmentation and Flow Regulation of River Systems in the Northern Third of the World. Science, 266(5186), 753-762. doi:10.1126/science.266.5186.753Erickson, H. P. (2009). Size and Shape of Protein Molecules at the Nanometer Level Determined by Sedimentation, Gel Filtration, and Electron Microscopy. Biological Procedures Online, 11(1), 32-51. doi:10.1007/s12575-009-9008-xEspinosa, M., Turner, B. L., & Haygarth, P. M. (1999). Preconcentration and Separation of Trace Phosphorus Compounds in Soil Leachate. Journal of Environmental Quality, 28(5), 1497-1504. doi:10.2134/jeq1999.00472425002800050015xFernández-Martínez, M., Vicca, S., Janssens, I. A., Sardans, J., Luyssaert, S., Campioli, M., … Peñuelas, J. (2014). Nutrient availability as the key regulator of global forest carbon balance. Nature Climate Change, 4(6), 471-476. doi:10.1038/nclimate2177Giddings, J., Yang, F., & Myers, M. (1976). Flow-field-flow fractionation: a versatile new separation method. Science, 193(4259), 1244-1245. doi:10.1126/science.959835Gimbert, L. J., Andrew, K. N., Haygarth, P. M., & Worsfold, P. J. (2003). Environmental applications of flow field-flow fractionation (FIFFF). TrAC Trends in Analytical Chemistry, 22(9), 615-633. doi:10.1016/s0165-9936(03)01103-8Gottselig, N., Bol, R., Nischwitz, V., Vereecken, H., Amelung, W., & Klumpp, E. (2014). Distribution of Phosphorus-Containing Fine Colloids and Nanoparticles in Stream Water of a Forest Catchment. Vadose Zone Journal, 13(7), vzj2014.01.0005. doi:10.2136/vzj2014.01.0005Gottselig, N., Nischwitz, V., Meyn, T., Amelung, W., Bol, R., Halle, C., … Klumpp, E. (2017). Phosphorus Binding to Nanoparticles and Colloids in Forest Stream Waters. Vadose Zone Journal, 16(3), vzj2016.07.0064. doi:10.2136/vzj2016.07.0064Hagedorn , A. G. 2006 EG-Sicherheitsdatenblatt (Gemäß 2001/58/EG)Hart, B. T., Douglas, G. B., Beckett, R., Van Put, A., & Van Grieken, R. E. (1993). Characterization of colloidal and particulate matter transported by the magela creek system, Northern Australia. Hydrological Processes, 7(1), 105-118. doi:10.1002/hyp.3360070111Hassellöv, M., Lyvén, B., Haraldsson, C., & Sirinawin, W. (1999). Determination of Continuous Size and Trace Element Distribution of Colloidal Material in Natural Water by On-Line Coupling of Flow Field-Flow Fractionation with ICPMS. Analytical Chemistry, 71(16), 3497-3502. doi:10.1021/ac981455yHassellov, M., & von der Kammer, F. (2008). Iron Oxides as Geochemical Nanovectors for Metal Transport in Soil-River Systems. Elements, 4(6), 401-406. doi:10.2113/gselements.4.6.401Hens, M., & Merckx, R. (2001). Functional Characterization of Colloidal Phosphorus Species in the Soil Solution of Sandy Soils. Environmental Science & Technology, 35(3), 493-500. doi:10.1021/es0013576Hill, D. M., & Aplin, A. C. (2001). Role of colloids and fine particles in the transport of metals in rivers draining carbonate and silicate terrains. Limnology and Oceanography, 46(2), 331-344. doi:10.4319/lo.2001.46.2.0331Jarvie, H. P., Neal, C., Rowland, A. P., Neal, M., Morris, P. N., Lead, J. R., … Hockenhull, K. (2012). Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland–lowland land-use continuum, under low-flow conditions. Science of The Total Environment, 434, 171-185. doi:10.1016/j.scitotenv.2011.11.061Jiang, X., Bol, R., Nischwitz, V., Siebers, N., Willbold, S., Vereecken, H., … Klumpp, E. (2015). Phosphorus Containing Water Dispersible Nanoparticles in Arable Soil. Journal of Environmental Quality, 44(6), 1772-1781. doi:10.2134/jeq2015.02.0085Kögel-Knabner, I., & Amelung, W. (2014). Dynamics, Chemistry, and Preservation of Organic Matter in Soils. Treatise on Geochemistry, 157-215. doi:10.1016/b978-0-08-095975-7.01012-3Krám, P., Hruška, J., & Shanley, J. B. (2012). Streamwater chemistry in three contrasting monolithologic Czech catchments. Applied Geochemistry, 27(9), 1854-1863. doi:10.1016/j.apgeochem.2012.02.020Lyvén, B., Hassellöv, M., Turner, D. R., Haraldsson, C., & Andersson, K. (2003). Competition between iron- and carbon-based colloidal carriers for trace metals in a freshwater assessed using flow field-flow fractionation coupled to ICPMS. Geochimica et Cosmochimica Acta, 67(20), 3791-3802. doi:10.1016/s0016-7037(03)00087-5Marschner, B., & Kalbitz, K. (2003). Controls of bioavailability and biodegradability of dissolved organic matter in soils. Geoderma, 113(3-4), 211-235. doi:10.1016/s0016-7061(02)00362-2Martin, J.-M., Dai, M.-H., & Cauwet, G. (1995). Significance of colloids in the biogeochemical cycling of organic carbon and trace metals in the Venice Lagoon (Italy). Limnology and Oceanography, 40(1), 119-131. doi:10.4319/lo.1995.40.1.0119Mattsson, T., Kortelainen, P., Laubel, A., Evans, D., Pujo-Pay, M., Räike, A., & Conan, P. (2009). Export of dissolved organic matter in relation to land use along a European climatic gradient. Science of The Total Environment, 407(6), 1967-1976. doi:10.1016/j.scitotenv.2008.11.014Missong, A., Bol, R., Willbold, S., Siemens, J., & Klumpp, E. (2016). Phosphorus forms in forest soil colloids as revealed by liquid-state31P-NMR. Journal of Plant Nutrition and Soil Science, 179(2), 159-167. doi:10.1002/jpln.201500119Montalvo, D., Degryse, F., & McLaughlin, M. J. (2015). Natural Colloidal P and Its Contribution to Plant P Uptake. Environmental Science & Technology, 49(6), 3427-3434. doi:10.1021/es504643fNeubauer, E., Köhler, S. J., von der Kammer, F., Laudon, H., & Hofmann, T. (2013). Effect of pH and Stream Order on Iron and Arsenic Speciation in Boreal Catchments. Environmental Science & Technology, 47(13), 7120-7128. doi:10.1021/es401193jNeubauer, E., v.d. Kammer, F., & Hofmann, T. (2011). Influence of carrier solution ionic strength and injected sample load on retention and recovery of natural nanoparticles using Flow Field-Flow Fractionation. Journal of Chromatography A, 1218(38), 6763-6773. doi:10.1016/j.chroma.2011.07.010Nischwitz, V., & Goenaga-Infante, H. (2012). Improved sample preparation and quality control for the characterisation of titanium dioxide nanoparticles in sunscreens using flow field flow fractionation on-line with inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry, 27(7), 1084. doi:10.1039/c2ja10387gRan, Y., Fu, J. ., Sheng, G. ., Beckett, R., & Hart, B. . (2000). Fractionation and composition of colloidal and suspended particulate materials in rivers. Chemosphere, 41(1-2), 33-43. doi:10.1016/s0045-6535(99)00387-2Regelink, I. C., Koopmans, G. F., van der Salm, C., Weng, L., & van Riemsdijk, W. H. (2013). Characterization of Colloidal Phosphorus Species in Drainage Waters from a Clay Soil Using Asymmetric Flow Field-Flow Fractionation. Journal of Environmental Quality, 42(2), 464-473. doi:10.2134/jeq2012.0322Regelink, I. C., Voegelin, A., Weng, L., Koopmans, G. F., & Comans, R. N. J. (2014). Characterization of Colloidal Fe from Soils Using Field-Flow Fractionation and Fe K-Edge X-ray Absorption Spectroscopy. Environmental Science & Technology, 48(8), 4307-4316. doi:10.1021/es405330xRegelink, I. C., Weng, L., & van Riemsdijk, W. H. (2011). The contribution of organic and mineral colloidal nanoparticles to element transport in a podzol soil. Applied Geochemistry, 26, S241-S244. doi:10.1016/j.apgeochem.2011.03.114RICHARDSON, C. J. (1985). Mechanisms Controlling Phosphorus Retention Capacity in Freshwater Wetlands. Science, 228(4706), 1424-1427. doi:10.1126/science.228.4706.1424Roth , C. 2011 Sicherheitsdatenblatt Gemäß Verordnung (EG) Nr. 1907/2006 RepSchmitt, D., Taylor, H. E., Aiken, G. R., Roth, D. A., & Frimmel, F. H. (2002). Influence of Natural Organic Matter on the Adsorption of Metal Ions onto Clay Minerals. Environmental Science & Technology, 36(13), 2932-2938. doi:10.1021/es010271pSix, J., Elliott, E. T., & Paustian, K. (1999). Aggregate and Soil Organic Matter Dynamics under Conventional and No-Tillage Systems. Soil Science Society of America Journal, 63(5), 1350-1358. doi:10.2136/sssaj1999.6351350xStolpe, B., Guo, L., Shiller, A. M., & Hassellöv, M. (2010). Size and composition of colloidal organic matter and trace elements in the Mississippi River, Pearl River and the northern Gulf of Mexico, as characterized by flow field-flow fractionation. Marine Chemistry, 118(3-4), 119-128. doi:10.1016/j.marchem.2009.11.007Tipping, E., & Hurley, M. . (1992). A unifying model of cation binding by humic substances. Geochimica et Cosmochimica Acta, 56(10), 3627-3641. doi:10.1016/0016-7037(92)90158-fTombácz, E., Libor, Z., Illés, E., Majzik, A., & Klumpp, E. (2004). The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles. Organic Geochemistry, 35(3), 257-267. doi:10.1016/j.orggeochem.2003.11.002Trostle, K. D., Ray Runyon, J., Pohlmann, M. A., Redfield, S. E., Pelletier, J., McIntosh, J., & Chorover, J. (2016). Colloids and organic matter complexation control trace metal concentration-discharge relationships in Marshall Gulch stream waters. Water Resources Research, 52(10), 7931-7944. doi:10.1002/2016wr019072U.S. Department of Agriculture 1993 Soil survey manual, chapter 3. Selected chemical propertiesVitousek, P. (1982). Nutrient Cycling and Nutrient Use Efficiency. The American Naturalist, 119(4), 553-572. doi:10.1086/283931Wells, M. L., & Goldberg, E. D. (1991). Occurrence of small colloids in sea water. Nature, 353(6342), 342-344. doi:10.1038/353342a0Wen, L.-S., Santschi, P., Gill, G., & Paternostro, C. (1999). Estuarine trace metal distributions in Galveston Bay: importance of colloidal forms in the speciation of the dissolved phase. Marine Chemistry, 63(3-4), 185-212. doi:10.1016/s0304-4203(98)00062-0Zirkler, D., Lang, F., & Kaupenjohann, M. (2012). «Lost in filtration»—The separation of soil colloids from larger particles. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 399, 35-40. doi:10.1016/j.colsurfa.2012.02.02

In-situ trace metal (Cd, Pb, Cu) speciation along the Po River plume (Northern Adriatic Sea) using submersible systems

Highlights • In-situ trace metal speciation in the Adriatic Sea by submersible voltammetric sensors • Metal species distribution mainly affected by Po River outflow. • Metal dynamic concentrations below legal limits • Cu dynamic concentrations toxic to sensitive phytoplankton Abstract Information on the distribution and speciation of trace metals is of critical importance for our ability to interpret the links between the bioavailability and uptake of an element, and its biogeochemical cycle in coastal environments. Within the framework of the European Project “In-situ automated Monitoring of Trace metal speciation in Estuaries and Coastal zones in relation with the biogeochemical processes (IMTEC)”, the chemical speciation of Cd, Pb and Cu was carried out along the Po River plume in the period 27 October – 2 November 2002. During the cruise, five Voltammetric In-situ Profiling systems and one Multi Physical Chemical Profiler, as well as conventional voltammetric instruments, were successfully applied in order to evaluate the distribution of Cd, Pb and Cu between different fractions (free ion, dynamic, colloidal, dissolved and particulate fractions) and to assess the evolution of these fractions during estuarine mixing and in the water column. Dynamic concentrations were 0.05–0.2 nmol L−1 Cd, 0.02–0.2 nmol L−1 Pb, and 0.15–4.0 nmol L−1Cu. Cd was mainly present as dynamic fraction (40–100% of the dissolved Cd). High proportions of Pb (~70%) and Cu (~80%) were present as colloids probably of biogenic origin. Principal components analysis reveals a strong influence of the Po River discharge on the spatial and vertical distributions of metal species. Almost all the metal fractions globally decreased following the salinity gradient. Metal concentrations are far below (at least one order of magnitude lower) the Environmental Quality Standard established by the Italian law. However, the Cu dynamic fraction showed concentrations likely to be toxic to sensitive phytoplankton community and to have negative effects on larva development of coastal macroinvertebrate species (toxicity data extracted from literature)

Changes in the nanoparticle aggregation rate due to the additional effect of electrostatic and magnetic forces on mass transport coefficients

The need may arise to be able to simulate the migration of groundwater nanoparticles through the ground. Transportation velocities of nanoparticles are different from that of water and depend on many processes that occur during migration. Unstable nanoparticles, such as zero-valent iron nanoparticles, are especially slowed down by aggregation between them. The aggregation occurs when attracting forces outweigh repulsive forces between the particles. In the case of iron nanoparticles that are used for remediation, magnetic forces between particles contribute to attractive forces and nanoparticles aggregate rapidly. This paper describes the addition of attractive magnetic forces and repulsive electrostatic forces between particles (by 'particle', we mean both single nanoparticles and created aggregates) into a basic model of aggregation which is commonly used. This model is created on the basis of the flow of particles in the proximity of observed particles that gives the rate of aggregation of the observed particle. By using a limit distance that has been described in our previous work, the flow of particles around one particle is observed in larger spacing between the particles. Attractive magnetic forces between particles draw the particles into closer proximity and result in aggregation. This model fits more closely with rapid aggregation which occurs between magnetic nanoparticles.Ministry of Education of the Czech Republic of the Technical University in Liberec [7822]; Ministry of Education of the Czech Republic [FR-TI1/456]; Ministry of Industry and Trad

Metal release from contaminated estuarine sediment under pH changes in the marine environment

The contaminant release from estuarine sediment due to pH changes was investigated using a modified CEN/TS 14429 pH-dependence leaching test. The test is performed in the range of pH values of 0-14 using deionised water and seawater as leaching solutions. The experimental conditions mimic different circumstances of the marine environment due to the global acidification, carbon dioxide (CO2) leakages from carbon capture and sequestration technologies, and accidental chemical spills in seawater. Leaching test results using seawater as leaching solution show a better neutralisation capacity giving slightly lower metal leaching concentrations than when using deionised water. The contaminated sediment shows a low base-neutralisation capacity (BNCpH 12 = -0.44 eq/kg for deionised water and BNCpH 12 = -1.38 eq/kg for seawater) but a high acid-neutralisation capacity when using deionised water (ANCpH 4 = 3.58 eq/ kg) and seawater (ANCpH 4 = 3.97 eq/kg). Experimental results are modelled with the Visual MINTEQ geochemical software to predict metal release from sediment using both leaching liquids. Surface adsorption to iron- and aluminium- (hydr)oxides was applied for all studied elements. The consideration of the metal-organic matter binding through the NICA-Donnan model and Stockholm Humic Model for lead and copper, respectively, improves the former metal release prediction. Modelled curves can be useful for the environmental impact assessment of seawater acidification due to its match with the experimental values.This work was supported by the Spanish Ministry of Economy and Competitiveness, Project No. CTM 2011-28437-C02-01, ERDF included. M. C. Martı´n-Torre was funded by the Spanish Ministry of Economy and Competitiveness by means of FPI. Fellowship No. BES-2012-053816