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The colloidal transport of trace (Fe, Al, Ba, Pb, Sr, U) and ultra-trace ( 226 Ra) elements was studied in a mining environment. An original approach combining 0.45 μm filtered water sampling, the Diffusive Gradient in Thin films (DGT) technique, mineralogical characterization, and geochemical modelling was developed and tested at 17 sampling points. DGT was used for the truly dissolved fraction of the elements of interest, while the 0.45 μm filtration includes both colloidal and truly dissolved fractions (together referred to as total dissolved fraction). Results indicated a colloidal fraction for Al (up to 50%), Ba (up to 86%), and Fe (up to 99%) explained by the presence of submicrometric grains of kaolinite, barite, and ferrihydrite, respectively. Furthermore, the total dissolved 226 Ra concentration in the water samples reached up to 10-25 Bq/L (1.2-3.0 10 -12  mol/L) at 3 sampling points, while the truly dissolved aqueous 226 Ra concentrations were in the mBq/L range. Such high total dissolved concentrations are explained by retention on colloidal barite, accounting for 95% of the total dissolved 226 Ra concentration. The distribution of 226 Ra between the truly dissolved and colloidal fractions was accurately reproduced using a (Ra x ,Ba 1-x )SO 4 solid solution, with values of the Guggenheim parameter a 0 close to ideality. 226 Ra sorption on ferrihydrite and kaolinite, other minerals well known for their retention properties, could not explain the measured colloidal fractions despite their predominance. This illustrates the key role of barite in such environments. The measured concentrations of total dissolved U were very low at all the sampling points (<4.5 10 -10  mol/L) and the colloidal fraction of U accounted for less than 65%. U sorption on ferrihydrite could account for the colloidal fraction. This original approach can be applied to other trace and ultra-trace elements to complement when necessary classical environmental surveys usually performed by filtration on 0.45 μm., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Digestate treatment techniques have recently been proposed as a strategy to increase the ultimate biogas yield from dairy manure and to improve the digestate quality as an organic fertilizer. These studies however rarely take the trace elements (TE) and nutrient partitioning into account. This study focusses on ozone treatment (5-40 g O 3 kg -1 Total Solids (TS)) as a digestate treatment technique to control the concentration of TE and nutrients in the liquid phase of the digestate. Controlling the TE and nutrient concentrations in the liquid and solid digestate can improve the agronomic value of dairy manure digestate. The ozone concentration of the gas stream entering reactor was 48.53 g O 3 /Nm³ or 3.4% w/w O 3 in O 2 -gas. The experiments were repeated using pure oxygen gas to investigate its influence. The results from ozonation and oxygenation of the dairy manure digestates revealed that O 3 treatment up to 40 g O 3 kg -1 TS did not have a more pronounced effect on the biochemical parameters compared to supplementation of pure O 2 . Ozonation of the digestate and the supernatant showed that the TE concentration in the liquid phase followed a parabolic profile. The observed initial increase in this parabolic profile was explained by the release of TE from the organic matter to the supernatant causing an increase in TE concentration, followed by a decrease due to precipitation of TE as hydroxides and sulfides, due to the increasing pH and sulphur concentrations., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Knowledge on the bioavailability of trace elements is essential in developing environmental quality standards. The purpose of this study was to explore the relationships between trace elements (in particular Uranium (U)) in sediments, porewater and their bioaccumulation by Chironomus riparius on a uranium mining site and river sediments upstream of the mine. The mobility and speciation of U in sediments was investigated using DGT. Geochemical modelling using CHESS provided insight on sorption behavior of U on ironoxyhydrite (HFO) and aqueous speciation of U. In the upstream site U concentrations found were 0.05 μmol g -1 in surface sediment, 0.84 nmol L -1 in porewater and 2.4 nmol g -1 in Chironomus riparius whereas in the ferrihydrite deposits on the mining sites the concentrations found were up to 9.4 μmol g -1 in surface sediment, 0.37 μmol L -1 in porewater and 0.684 μmol g -1 in in Chironomus riparius. Despite the large differences in concentrations of U between the two sites, sediment to dissolved partitioning coefficients, bioconcentration factor (BCF) and biota sediment accumulation factors (BSAF) were very comparable. In the upstream sediment binding of U to organic matter controls sorption and aqueous speciation of U, whereas in the HFO rich sediments, sorption on HFO and the formation of HFO colloids are the determining factors. The low BSAF factors and high BCF factors indicate that the bioaccumulation is due to uptake from the dissolved phase. The DGT probes with different binding resins provide information on the colloidal nature and lability of the dissolved U species., (Copyright © 2019. Published by Elsevier Ltd.)

The genetic diversity of giant tiger prawns in relation to trace metals (TMs) pollution was analysed using 159 individuals from eight sites at the Tanzanian coast. The seven microsatellites analysed showed high degree of polymorphism (4-44 alleles). The measured genetic diversity (H o =0.592±0.047) was comparable to that of populations in the Western Indian Ocean. Apart from that, correlation analysis revealed significant negative associations between genetic diversity and TMs pollution (p<0.05), supporting the genetic erosion hypothesis. Limited gene flow was indicated by a significant genetic differentiation (F ST =0.059, p<0.05). The Mantel test rejected the isolation-by-distance hypothesis, but revealed that gene flow along the Tanzanian coast is limited by TMs pollution. This suggests that TMs affect larvae settlement and it may account for the measured deficiency of heterozygosity. This calls for strengthened pollution control measures in order to conserve this commercially important species., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The Diffusive Gradients in Thin films (DGT) technique was used to analyse U, (226)Ra and other trace metals in stream water and soil porewater in a wetland in France impacted by uranium mining. High resolution profiles of metals in soil porewater obtained by DGT could be measured for the first time up to a depth of 75 cm by the construction of a novel DGT holder. In stream water, the DGT technique was compared to speciation carried out by filtration (0.45 μm) and ultrafiltration (UF) (500 kDa/100 kDa/10 kDa) and DGT porewater profiles were compared with piezometer data obtained in a parallel study. An increase in the trace concentrations of dissolved (0.45 μm) and particulate U, (226)Ra, and elements such as Al, Fe, Mn and Ba was observed in the stream water as it passes through the bog as a results of mobilization from the wetland. The porewater results indicate DGT labile metals species to be present in porewater and mobilization of uranium and other elements linked to the presence of enriched clays. In stream water, colloids and particles govern the behavior of U, Al and Fe, whereas Mn, Ba and Ra are essentially transported as truly dissolved metal species with DGT labile concentrations accounting for 100% of the dissolved fraction. The combined approaches of DGT and UF allow us to obtain a better understanding on the biogeochemical processes involved in the retention and mobility of U and (226)Ra in the wetland., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The Flemish Centre for Environment and Health started with human biomonitoring in 2002 (FLEHS I: 2002-2006). The main goal of the second human biomonitoring cycle (FLEHS II: 2007-2011), was to determine mean values for a large number of pollutants in a representative sample of the general Flemish population. Values for Cd and Pb were updated, and a group of previously undetermined metals and metalloids (As, Mn, Cu and Tl) were included in some of the age groups. In this human biomonitoring program, three different age groups of the general Flemish population were monitored: 255 newborns and their mothers, 210 adolescents aged 14-15, and 204 adults between 20 and 40 years old. Trace elements were determined in cord blood and maternal blood of the mothers, in blood and urine of adolescents and in urine of adults. Determinants of life-style and personal factors were taken into account. The levels of trace elements in cord blood and maternal blood were for most elements at the lower end of the range found in literature. For Pb, As and Tl, a strong correlation (respectively r=0.43, 0.55 and 0.33; p<0.05) was found between levels in cord blood (respectively 8.6, 0.54 and 0.017 μg/L) and maternal blood (11.1, 0.64 and 0.028 μg/L), indicating that they are transported via the placenta from mother to fetus. The levels found in the adolescents and adults were compared with results from international biomonitoring studies, and were found to be in the same ranges. With the exception of Pb, all trace elements increased with increasing age group population. Finally, the results also showed that the levels of Cd and Pb in blood for this campaign (e.g. for Pb 8.6 and 14.8 μg/L in neonates and adolescents respectively) were lower compared to the first campaign (e.g. for Pb 14.7 and 21.7 μg/L in neonates and adolescents respectively), indicating a decrease over time. However, differences in sampling strategies might partially explain this observed trend., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

The accumulation of trace elements (Mg, Mn, Sr, Ba) in Unio pictorum L. mussel shells from Lake Balaton has been assessed using a Laser Ablation (LA) system coupled to either a quadrupole-based or a sector-field inductively coupled plasma-mass spectrometer (ICP - MS), as well as by a combination of micro-drill sampling and solution ICP-MS. The LA-ICP-MS measurements were carried out in the holes made by the micro-drilling system. The longitudinal concentration profiles obtained with the different methods show similar patterns. However, the absolute concentrations determined at individual spots (holes) can be quite different. Especially Ba shows erratic peaks at a very small spatial scale. A paired, two-sample t-test between LA-ICP-MS longitudinal profiles and between LA-ICP-MS and micro-drill/solution ICP-MS profiles indicates that, in most cases, there is no significant difference between the concentration profiles of Ba, Mg, Mn and Sr. Average shell concentrations of Mg, Mn, Sr and Ba, as obtained by LA-ICP-MS and micro-drill/solution ICP-MS, compare well with bulk shell concentrations as obtained by acid digestion/ICP-MS of larger shell pieces. Next to the four elements mentioned above, also the concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn could be determined by bulk shell analysis. The element concentrations in 11 shells, all sampled at the same site, show a relative standard deviation (RSD) between 2% (Ni) and 46% (Zn). LA-ICP-MS and micro-drill solution ICP-MS are not sensitive enough for the determination of ultra-trace elements in Lake Balaton's mussel shells. We estimated the amount of shell material necessary to determine Ni, Pb, Cr and Cu by micro-drilling ICP-MS (for a concentration that equals 3 times their limit of detection) at, respectively, 0.04, 0.82, 2.7 and 0.4 mg, while the amount sampled by micro-drilling is about 0.06 mg., (© 2013 Elsevier B.V. All rights reserved.)

Abstract Sequential extraction schemes (SES) were evaluated to investigate the fractionation of Al, As, Cd, Cs, Cr, Co, Cu, Fe, Mn, Mo, Pb, Sr, U and Zn between the different mineral phases in iron oxide rich deposits of a former uranium mining site. Ineffective dissolution of iron oxide was observed when applying the BCR sequential extraction scheme. The hydroxylamine hydrochloride reagent in nitric acid could not effectively dissolve the iron oxide phase, even after several consecutive extractions. The use of sodium pyrophosphate to remove organic matter prior to the dissolution of the iron oxides and the use of oxalic acid buffer and dithionite citrate buffer to dissolve the amorphous and crystalline iron oxides was evaluated. An alternative six step SES for iron oxide rich sediments is proposed consisting of F1) Exchangeable-Carbonate fraction using acetic acid/ sodium acetate buffer (pH 5) F2) Labile organic fraction using sodium pyrophosphate, F3) Easily reducible amorphous oxides using an oxalic acid buffer, F4) Organic and Sulfide fraction using hydrogen peroxide, followed by ammonium acetate extraction, F5) Poorly reducible crystalline oxides using sodium dithionite and F6) residual fraction using a microwave digestion step with hydrofluoric acid, nitric acid and hydrochloride acid mixture. A good correspondence between the sum of the sequential extraction steps and total metal concentrations was found. Both the BCR method and new method were also applied to the CRM BCR 701 providing indicative values for non-certified elements with the BCR method and indicative values for the method presented. Graphical abstract fx1 Highlights • Hydroxylamine reagent does not extract iron-oxides rich sediments efficiently. • Organic matter also influences extraction efficiency of hydroxylamine. • Novel six step sequential extraction scheme for iron-oxide rich sediments was developed. • New method was applied on a uranium mining site. • New method was also applied on BCR-701 reference material. [ABSTRACT FROM AUTHOR]

Abstract: In the Flemish human biomonitoring programme FLEHS II (2007–2011) trace metals (Cd, Pb, Cr, Ni, Cu, Mn, Tl, Sb, As and toxic relevant arsenic) were analysed in the blood and urine of adolescents (14–15 years old) in the reference population in Flanders and in areas of important industrial activities: Genk-Zuid and Menen. After adjustment of the results for confounding factors, the adolescents living in Genk-Zuid had higher levels of Cr, Cu and Tl in blood, higher levels of Cd and toxic relevant arsenic (TRA) in urine, but lower levels of Ni in blood and Sb in urine compared to the reference population. In Menen higher levels of Cd and Cu in urine, higher concentrations of Tl in blood but lower concentrations of Pb in blood and lower Ni, Sb and As in urine were found compared to the reference population. For both the reference population and the hot spots the concentrations are within the ranges found in other countries. Compared to the previous biomonitoring programme FLEHS I (2002–2006) a decrease in the concentrations of Cd and especially of Pb in blood was observed. However, it cannot be excluded that differences between the two campaigns are partially due to different sampling strategies. [Copyright &y& Elsevier]

Iron, manganese, and trace elements play an important role in the marine carbon cycle as they are limiting nutrients for marine primary productivity. Water column concentrations of these bio-essential elements are controlled by the balance between input and removal, with burial in marine sediments being the main sink. The efficiency of this burial sink is dependent on the redox state of the water column, with sediments underlying a sulphidic (euxinic) water column being the most efficient sinks for Fe, but also Mn and trace elements (Co, Cd, Ni, Mo, As, W, V, and U). Transient changes in ocean redox state can hence affect trace element burial, and correspondingly, the ocean's trace element inventory, but the impact of transient oxygenation events on trace element cycling is currently not well understood. Here, we investigate the impact of a natural oxygenation event on trace element release and burial in sediments of the Eastern Gotland Basin (EGB), a sub-basin of the Baltic Sea. After being anoxic (<0.5 µM O 2) for ∼10 years, the deep waters of the EGB experienced a natural oxygenation event (Major Baltic Inflow, MBI) in 2015. Following this oxygenation event, we deployed benthic chamber landers along a depth transect in the EGB in April 2016, 2017 and 2018. We complemented these in situ flux measurements with analyses of water column, solid phase and pore water chemistry. Overall, the event increased the benthic effluxes of dissolved trace elements, though particular responses were element-specific and were caused by different mechanisms. Enhanced fluxes of Cd and U were caused by oxidative remobilisation, while Ni showed little response to the inflow of oxygen. In contrast, enhanced release of Co, Mo, As, W, and V was caused by the enhanced transient input of Mn oxides into the sediment, whereas Fe oxides were of minor importance. Following the dissolution of the oxides in the sediment, Mn and W were nearly completely recycled back to the water column, while fractions of Fe, Co, Mo, As, and V were retained in the sediment. Our results suggest that transient oxygenation events in euxinic basins may decrease the water column inventory of certain trace elements (Fe, Co, Mo, As, and V), thus potentially affecting global marine primary productivity on longer timescales. [ABSTRACT FROM AUTHOR]

Abstract: High resolution profiles of trace elements (Fe, Mn, Co, As, Cu, Cr, Ni and Pb) were assessed using the DET (Diffusive Equilibrium in Thin films) and DGT (Diffusive Gradients in Thin films) techniques in silty, organically enriched, sub-tidal sediments of the Belgian coast during late winter and spring 2008. The general chemical properties of the sediments such as dissolved oxygen, pH, Eh and sulfide profiles, controlling precipitation/mobilization reactions, were determined with electrodes (pH and Eh) and microelectrodes (oxygen) and AgI-DGT probes (sulfide). Most trace elements show subsurface maxima and low concentrations beneath 8 cm of depth. The main physicochemical parameters controlling the vertical concentration profiles are dissolved oxygen and redox potential in the surface sediment and sulfide in the deeper sediment layers. Thermodynamic equilibrium calculations have been carried out verifying which solid phases can explain the dissolved trace metal concentrations. Seasonal variations of trace elements have been observed during the sampling period and sedimentation of fresh particulate organic matter (POM) derived from phytoplankton blooms appear to be the main cause of this temporal variability. Flux calculations based on DGT profiles (these fluxes are minimum ones) show that exchange fluxes of trace metals in February are slightly higher than in April. In addition, “DGT pistons” were deployed at the sediment water interface (SWI) to accumulate labile ions from below. This way all labile ions, binding onto the DGT Chelex resin, are pumped out of the pore waters and the solid sediment phase (only the mobile fraction). These results are a direct estimation of the amount of trace elements that can be released from the upper sediment to the water column (in the range of 4.4·10−5 to 0.10 mmol·m−2·d−1 for Co, Pb, Cr, As, Cu, Ni, Fe and Mn). [Copyright &y& Elsevier]

Freshly erupted volcanic ash contains a range of soluble elements, some of which can generate harmful effects in living cells and are considered potentially toxic elements (PTEs). This work investigates the leaching dynamics of ash-associated PTEs in order to optimize a method for volcanic ash respiratory hazard assessment. Using three pristine (unaffected by precipitation) ash samples, we quantify the release of PTEs (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn) and major cations typical of ash leachates (Mg, Na, Ca, K) in multiple simulated lung fluid (SLF) preparations and under varying experimental parameters (contact time and solid to liquid ratio). Data are compared to a standard water leach (WL) to ascertain whether the WL can be used as a simple proxy for SLF leaching. The main findings are: PTE concentrations reach steady-state dissolution by 24 h, and a relatively short contact time (10 min) approximates maximum dissolution; PTE dissolution is comparatively stable at low solid to liquid ratios (1:100 to 1:1000); inclusion of commonly used macromolecules has element-specific effects, and addition of a lung surfactant has little impact on extraction efficiency. These observations indicate that a WL can be used to approximate lung bioaccessible PTEs in an eruption response situation. This is a useful step towards standardizing in vitro methods to determine the soluble-element hazard from inhaled ash. [Display omitted] • Investigation of a lung fluid leachate method to assess inhalation hazards of ash. • Element release in leachates is both method-parameter and sample dependent. • Inclusion of lung surfactant is not necessary when assessing ash leachates. • Optimal method parameters are extraction up to 24 h at 1:100 ratio. • Water leach can be used as a conservative estimate of lung bioaccessible elements. [ABSTRACT FROM AUTHOR]