Diffusive Gradients In Thin Films Research Articles

Use of diffusive gradients in thin-film technique to predict the mobility and transfer of nutrients and toxic elements from agricultural soil to crops-an overview of recent studies.

The purpose of this review was to survey the recent applications of the diffusive gradients in thin films (DGT) technique in the assessment of mobility and bioavailability of nutrients and potentially toxic elements (PTEs) in agricultural soil. Many studies compared the capabilities of the DGT technique with those of classical soil chemical extractants used in single or sequential procedures to predict nutrients and PTE bioavailability to crops. In most of the published works, the DGT technique was reported to be superior to the conventional chemical extraction and fractionation methods in obtaining significant correlations with the metals and metalloids accumulated in crops. In the domain of nutrient bioavailability assessment, DGT-based studies focused mainly on phosphorous and selenium labile fraction measurement, but potassium, manganese, and nitrogen were also studied using the DGT tool. Different DGT configurations are reported, using binding and diffusive layers specific for certain analytes (Hg, P, and Se) or gels with wider applicability, such as Chelex-based binding gels for metal cations and ferrihydrite-based hydrogels for oxyanions. Overall, the literature demonstrates that the DGT technique is relevant for the evaluation of metal and nutrient bioavailability to crops, due to its capacity to mimic the plant root uptake process, which justifies future improvement efforts.

Recycled Iron Phosphates: A New Phosphorus Fertilizer for Paddy Rice.

The potential of recycled iron phosphates (FePs), e.g., vivianites (Fe3(PO4)2·8H2O) and Fe(III)-rich phosphorus (P) adsorbent materials, as phosphorus fertilizer is limited by the strong interaction between Fe and P. In this study, the efficiency of FePs as P fertilizer was explored by applying them as granules or powder in flooded strongly P-fixing soils (acid and calcareous), thereby taking advantage of increased P release induced by reductive dissolution of P-bearing Fe(III) minerals. First, no P diffusion from granular FeP fertilizers into flooded soils was detectable by the diffusive gradient in thin films (DGT) technique and microfocused X-ray fluorescence (μ-XRF) analysis of thin soil sections, in contrast to detectable P diffusion away from granules of soluble triple superphosphate (TSP) fertilizer. On the contrary, powdered FePs demonstrated an excellent increase in extractable P (1 mM CaCl2) in a 120-day incubation experiment in flooded soils. Second, a pot experiment was performed with rice (Oryza sativa) grown in flooded acid and calcareous soils. The fertilizer value of FePs was remarkable when dosed as powder, as it was even up to 3-fold higher than TSP in the acid soil and similar to TSP in the calcareous soil. The beneficial effect of FeP over TSP in the acid soil is attributed to the slow release of P from FePs, which allows to partly overcome P fixation. The promising results of FePs as P fertilizer applied as powders in flooded soils debunk the generally accepted idea that FePs are poor sources of P while demonstrating the importance of the timing of FeP fertilizer application.

Comparison of mercury (Hg) bioaccumulation with mono- and mixed Lemna minor and Spirodela polyrhiza cultures.

Mercury (Hg) is a prevalent and harmful contaminant that persists in the environment. For phytoremediation, it is important to discover which plants can bioaccumulate meaningful amounts of Hg while also tolerating its toxicity. Additionally, increasing biodiversity could create a more resilient and self-sustaining system for remediation. This study explores whether mixed populations of Lemna minor and Spirodela polyrhiza can better bioaccumulate and tolerate Hg than monocultures. Mono- and mixed cultures of L. minor and S. polyrhiza were grown in mesocosms of 0.5µg/L or 100µg/L Hg (HgCl2) spiked water for 96h. Change in weight of duckweed was used to assess Hg tolerance. Diffusive gradients in thin-films (DGTs) were used as surrogate monitoring devices for bioavailable levels of Hg. For biomass growth, the mixed culture of the L. minor was greater than the monoculture at the high dose. The L. minor accumulated more Hg in the mixed culture at the low dose while the S. polyrhiza was higher in the mixed at the high dose. Hg speciation in water was modeled using Windermere Humic Aqueous Model 7 (WHAM7) to compare the bioavailable species indicated by the DGTs. Potentially due to the controlled conditions, the WHAM7 output of bioavailable Hg was almost 1:1 to that estimated by the DGTs, indicating good predictive capability of geochemical modeling and passive sampler DGT on metal bioavailability. Overall, the mixed cultures statistically performed as well as or better than the monocultures when tolerating and bioaccumulating Hg. However, there needs to be further work to see if the significant differences translate into practical differences worth the extra resources to maintain multiple species.

Impact on sulfadiazine bio-accessibility in soils through organic diffusive gradients in thin films (o-DGT): Differentiation based on microplastic polymers, aging, and soil properties

Due to the similar sources of swage irrigation, organic fertilizer, and sludge application, microplastics (MPs) and antibiotics coexist inevitably in the agriculture soils. However, the impacts of MPs with different polymer types and aging status on the bio-accessibility of co-existing antibiotics in soils remained unclear. Therefore, we using the diffusive gradients films for organic compounds devices (o-DGT) to evaluated the distribution of sulfadiazine (SDZ) in both paddy soil and saline soil amended with 0.5 % (w/w) MPs. Four polymer types (polyethylene: PE, polypropylene: PP, polyamide: PA, and polyethylene terephthalate: PET) and two aging statuses (aged PE and aged PP) of MPs were used in this study. Results showed that soil properties significantly influence the partition of SDZ in soil and soil solution, and SDZ gained a lower degradation rate but higher mobility in saline soil. MPs pose different impacts on partition of SDZ between paddy soil and saline soil. Notably, PP reduced the labile solid phase-solution phase partition coefficient (Kdl) by 17.7 % in paddy soil, while PE, PP, and aPE increased the Kdl value by 2.00, 1.62, and 2.81 times in saline soil. Besides, in saline soil, all the MPs reduced the SDZ concentration in the soil solution, while significantly increased the SDZ in o-DGT phase. Conversely, MPs did not impact the SDZ's o-DGT concentration in paddy soil. Additionally, MPs increased the R value of SDZ in two soils, especially in saline soil. It suggested that MPs could potentially enhance the resupply of SDZ from soil to plants, particularly under saline conditions. Furthermore, aged MPs had a more pronounced effect on these indicators compared to virgin MPs in saline soil. Therefore, MPs in soil poses a potential risk for biota's uptake of SDZ, particularly in fragile environment. Moreover, the risk intensifies with aged MPs.

Development of diffusive gradients in thin-films technique for monitoring polycyclic aromatic hydrocarbons in coastal waters

Addressing the challenge of accurately monitoring polycyclic aromatic hydrocarbons (PAHs) in aquatic systems, this study employed diffusive gradients in thin-films (DGT) technique to achieve methods detection limits as low as 0.02 ng L−1 to 0.05 ng L−1 through in situ preconcentration and determination of time-integrated concentrations. The efficacy of the developed DGT samplers was validated under diverse environmental conditions, demonstrating independence from factors such as pH (5.03–9.01), dissolved organic matter (0–20 mg L−1), and ionic strength (0.0001–0.6 M). Notably, the introduction of a novel theoretical approach to calculate diffusion coefficients based on solvent-accessible volume tailored for PAHs significantly enhanced the method’s applicability, particularly for organic pollutants with low solubility. Field deployments in coastal zones validated the DGT method against traditional grab sampling, with findings advocating a 4 to 7-day optimal deployment duration for balancing sensitivity and mitigating lag time effects. These results provide a sophisticated, efficient solution to the persistent challenge of monitoring hydrophobic organic pollutants in aquatic environments, broadening the scope and applicability of DGT in environmental science and providing a robust tool for researchers.

Mapping elemental solutes at sub-picogram levels during aqueous corrosion of Al alloys using diffusive gradients in thin films (DGT) with LA-ICP-MS.

A novel approach using diffusive gradients in thinfilms (DGT) with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for two-dimensional mapping of elemental solute release at sub-picogram levels during aqueous corrosion of Al alloys is presented. Evaluation of different DGT gels with mixed micro-sized binding phases (polyacrylamide-Chelex-Metsorb, polyurethane (PU)-Chelex-Metsorb, PU-Chelex-Zr(OH)4) demonstrated the superior performance of PU gels due to their tear-proof handling, low shrinkage, and compliance with green chemistry. DGT devices containing PU-Chelex-Zr(OH)4 gels, which have not been characterized for Al sampling before, showed quantitative uptake of Al, Zn, and Cu solutes over time (t = 4-48h) with higher Al capacity (ΓDGT = 6.25µgcm-2) than different gels. Application of PU-Chelex-Zr(OH)4 gels on a high-strength Al-Cu alloy (Al2219) exposed to NaCl (w = 1.5%, pH = 4.5, T = 21°C) for 15min in a novel piston-type configuration revealed reproducible patterns of Al and Zn co-solubilization with a spatial expansion ranging between 50 and 1000µm. This observation, together with complementary solid-state data from secondary electron microscopy with energy-dispersive X-ray spectroscopy, showed the presence of localized pitting corrosion at the material surface. Detection limits for total solute masses of Al, Zn, and Cu were ≤0.72pg, ≤8.38pg, and ≤0.12pg, respectively, for an area of 0.01 mm2, demonstrating the method's unique capability to localize and quantify corrosion processes at ultra-trace levels and high resolution. Our study advances the assessment of Al alloy degradation in aqueous environments, supporting the design of corrosion-resistant materials for fostering technological safety and sustainability.

Efficient reclamation of phosphorus from wetland plant via CaCl2/NaOH-mediated hydrothermal carbonization: insights from the evolution of phosphorus

Hydrothermal carbonization (HTC) of wetland plant could achieve the recovery of phosphorus (P) via the production of P-enriched hydrochar to alleviate the crisis of phosphate resources, while the migration and transformation of P should be determined. In this study, Canna indica was derived into hydrochar through HTC at different temperatures (200°C-260°C) and liquid mediums (H2O, CaCl2, and NaOH). The P forms were systematically characterized using P K-edge X-ray absorption near edge structure (XANES), 31P liquid nuclear magnetic resonance (NMR), and sequential extraction. The total P content in hydrochar was up to 23 mg g−1 with mainly inorganic P (> 97.8%), and the recovery rate was almost 100% during NaOH-mediated HTC. The P species, monoester-P and soluble orthophosphate (ortho-P), in biomass were transformed to more stable ortho-P in hydrochars, which was highly dependent on temperature and liquid medium. With increasing temperature, Al/Mg-P was gradually replaced by Ca/Fe-P. The CaCl2 solution facilitated the transformation of Ca(H2PO4)2 into CaHPO4 by elevating the Ca/P ratio. While for the NaOH-mediated HTC, the CaHPO4 and Ca(H2PO4)2 were transformed to hydroxyapatite (74.3%-81.5%), and the proportion of MgHPO4 elevated with increasing temperature. The diffusive gradients in thin films (DGT) results implied that the addition of hydrochar greatly elevated the soil available P content, which was further promoted by high temperature and NaOH medium. These results indicate that the species and availability of P in hydrochar could be adjusted through varying liquid medium and reaction temperature, which provide guidance for the target design of P-enriched hydrochar and P reclamation.Graphical

Arsenic mobilization across the sediment-water interface of the Three Gorges Reservoir as a function of water depth using DGT and HR-Peepers, a preliminary study

The artificial regulation of the Three Gorges Reservoir (TGR) creates large water level fluctuation zones (WLFZ) that may change the behavior of metals and metalloid in sediment, particularly redox sensitive elements. Mobilization of As, Fe and Mn across the sediment-water interface (SWI) in the TGR as a function of different water depth (periodically and permanently submerged sediments, respectively) was in situ determined by diffusive gradients in thin films (DGT) and high-resolution dialysis technique (HR-Peeper), respectively. The results showed that the mobilization of As was significantly affected by Fe/Mn especially Mn, across the SWI. Duo to the oxic-anoxic transitional state in near bottom water, the reduced Fe and Mn in sediment pore water could be oxidized and precipitated again, leading to the co-precipitation of As with Fe/Mn oxides (hydroxides). Consequently, concentrations of As, Fe and Mn in labile phases and pore water were generally low across the SWI, then they sharply increased at a few centimeters below the SWI. Considering different water depth, various trends were found in labile phase, whereas concentrations of As, Fe and Mn in pore water in permanently submerged sediments were significantly higher than those in periodically submerged sediments. The dry-re-wetting alternation processes in the WLFZ may play vital roles in the resupply capacity of sediments as it was found that periodically submerged sediments with longer re-wetting time had higher Fe/Mn resupply capacity than those with shorter re-wetting times and permanently submerged sediments.

Application of diffusive gradient in thin films probes to monitor trace levels of labile methylmercury in freshwaters.

This study aimed to optimize the methods for sampling and analyzing methylmercury (MeHg) concentrated within diffusive gradients in thin films (DGT) and its application to different water bodies. We explored the elution solution for MeHg, comprised of 1.13 mM thiourea and 0.1M HCl, optimizing its volume to 50 mL. In addition, we found that it is necessary to analyze the entire extraction solution after adjusting its pH, to ensure completion of the ethylation reaction. The DGT samplers were deployed in two distinct aquatic environments (i.e., Okjeong Lake and Nakdong River) for up to 6 weeks, and this study demonstrated to predict the time-weighted average concentration with a diffusion coefficient of 7.65 × 10-6 cm2 s-1 for MeHg in the diffusive gel. To assess the diffusive boundary layer (DBL) effects, the DGT samplers with different agarose diffusive gel thickness were deployed. The mass of MeHg accumulated in the DGT resin at a given time decreased with increasing diffusive gel thickness, because of creating longer diffusion pathways within thicker gels. The labile MeHg concentration estimated by the DGT in Okjeong Lake and Nakdong River are found in the range of 61-111 and 55-105 pg L-1, respectively, which were found to be similar to the grab sampling data. Additionally, this study evaluated depth-dependent MeHg in Okjeong Lake. The vertical profile results showed that the concentration of MeHg at the depth of 2.3 and 15.7 m are about 1.5 and 4.6 times of the DGT installed at 0.3 m of the surface layer, respectively, suggesting potential mercury methylation in deep waters. These findings have practical implications for predicting bioavailability, assessing risks, and formulating strategies for water body management and contamination remediation.

Release risk of soil phosphorus under different farming systems: Indoor experiments and in-situ measurement

Agricultural phosphorus (P) application leads to the accumulation and release of soil P, which pose ecosystem risks. Different farming systems carry substantial risks of soil P release. This study evaluated the risk of soil P release in three representative systems of paddy fields in China (rice fields (RF), integrated crayfish-rice fields (CRF), and crayfish fields (CF)) using indoor adsorption and desorption experiments and the diffusive gradient in thin films (DGT) technique, and compared the obtained results. The soils of RF and CRF showed higher levels of redox potential (Eh), free Fe–Al oxides (DCB-Fe, DCB-Al), and amorphous Fe–Al oxides (Ox-Fe, Ox-Al) compared to CF. Additionally, the soils of CRF and CF exhibited higher total organic carbon (TOC) content. The indoor experiments revealed a positive correlation between the contents of Ox-Fe, Ox-Al, bioavailable P (BAP), clay, and soil P adsorption characteristics. Desorption characteristics were primarily influenced by total P, TOC, and Ox-Fe content. Furthermore, the order of soil P release risk followed CRF > RF > CF. According to the in situ DGT measurements, the soil P release fluxes were 0.266 mg·m−2·d−1 for CRF, 0.548 mg·m−2·d−1 for RF, and 0.583 mg·m−2·d−1 for CF. Accordingly, the risk of soil P release followed the order CRF < RF < CF. The contrasting results from these two methods are attributable to the indoor experiments indicating the potential for soil P adsorption under specific experimental conditions and the in situ DGT reflecting natural soil P release in a more effective and suitable manner for evaluating soil P release. The findings improve our understanding of the risk of soil P loss in CRF and provides valuable insights into the two methods.

Assessing the bioaccessibility of aluminum in an acidic soil with the diffusive gradients in thin films (DGT) and DIFS

Assessing the bioaccessibility of aluminum in an acidic soil with the diffusive gradients in thin films (DGT) and DIFS

Influence and Mechanism Study of Soil Moisture on the Stability of Arsenic-Bearing Ferrihydrite in Surface Soil Vertical Profiles

Ferrihydrite is usually used as a remedy for arsenic (As)-contaminated soil due to its strong affinity and large specific surface area. However, its noncrystalline phase makes it unstable in long-term applications in the soil. In this study, a soil incubation experiment was designed using the diffusive gradient in thin film (DGT) technique and spectral techniques to investigate the fate of As-bearing ferrihydrite [As(V)-Fh] after long-term incubation at different soil water holding capacities (SWHCs). After As(V)-Fh (0.05 and 0.005 As/Fe molar ratio) was incubated in soil for 360 days, both DGT-derived labile As and Fe were released at 70% SWHC and 120% SWHC into the soil (at a vertical depth of 12 cm). The concentrations of DGT-As and DGT-Fe increased with incubation time and were greater at 120% SWHC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that As(V)-Fh gradually transformed into hematite and goethite after 360 days of incubation. Goethite was mainly found in the 120% SWHC treatment after 180 days. Hematite and goethite formation rates were greater in the 120% SWHC treatment and in the bottom soil layer. Mechanistic analysis based on X-ray photoelectron spectroscopy (XPS) revealed that the variation in soil pH and the formation of Fe(II) (under flooded water conditions) are the two key factors promoting the formation of hematite (dehydrogenation and dehydration) and goethite (As(V)-Fh dissociation and reorganization). The As release mainly occurred due to the loss of adsorption sites. Thus, it is recommended that ferrihydrite be applied in paddy–dry rotations or dry-field patterns to effectively avoid the loss of As(V)-Fh in long-term-saturated soil.

Long-term biochar application influences phosphorus and associated iron and sulfur transformations in the rhizosphere

The effects of long-term biochar application on soil phosphorus (P) flux across the root-soil interface and its availability in the rhizosphere of rice (Oryza sativa L) remain unclear. We used diffusive gradients in thin films (DGT), laser ablation-inductively coupled plasma mass spectrometry, and planar optode sensor techniques to characterize, in-situ, the 2D heterogeneity and dynamics of rhizosphere soil P, iron (Fe), sulfur (S) and trace element fluxes, dissolved oxygen and pH in paddy soil, after 10 years of biochar application. Compared to the control (no biochar applied), biochar applied at 4.5, 22.5 and 45.0 Mg ha−1 yr−1 decreased rhizospheric P fluxes by 11.6%, 63.4% and 79.0%, respectively. This decrease under biochar treatments was attributed to changed redox status of Fe and S caused by the lower dissolved oxygen in rhizosphere soil and increased soil pH induced precipitating of soluble inorganic P into insoluble P forms, such as calcium-bound and residual P that are unavailable for crop uptake. Higher application rate of biochar resulted in lower As and Pb fluxes in rice rhizosphere and their availabilities for crop uptake. The in-situ observation results in rice rhizosphere at μm-scale after 10 years of biochar addition directly showed the complex effects of long-term biochar and rhizosphere heterogeneity on P transformation process.Graphical

Influence of microplastics on the availability of antibiotics in soils

Microplastics (MPs) and antibiotics, as two major types of emerging pollutants, inevitably coexist in the soil environment due to agricultural film residue, sewage irrigation and sludge application. However, the impact of MPs on antibiotic availability in soils with varying characteristics has not been extensively studied. Therefore, in this study, an interference experiment was conducted using three types of MPs (polyethylene (PE), polyvinyl chloride (PVC) and polypropylene (PP)) in red soil, paddy soil and cinnamon soil. The available antibiotics in soils were evaluated using diffusive gradients in thin-films (DGT). Results showed that MPs had a significant impact on the amount of antibiotics adsorbed on soil solid (Cs) by providing additional binding sites or altering soil characteristics (e.g., pH and dissolved organic carbon). The most significant effects on Cs were observed in cinnamon soil, and the Cs values were dependent on concentration of MPs. The available antibiotics, as measured by DGT significantly decreased after the addition of MPs. This decrease was influenced by the soil characteristics. However, the concentration of antibiotics in soil solutions (Cd) was only slightly impacted by MPs. Therefore, the influence of MPs on the migration of antibiotics was reflected by their impact on the soil/water partition coefficient (Kd), while the resupply ability (R) from the soil solid phase was less influential. Moreover, the dosage of MPs had a significant effect on the availability of antibiotics in CS by promoting the adsorption of antibiotics on the solid phase, while in RS and PS, the soil properties played a dominate role in the changes in antibiotic availability after MP addition. These results indicate that the impact of MPs on available antibiotics mainly depends on soil properties. In addition, DGT measurement is more sensitive than soil solution to investigate the effects of coexisting pollutants on the behavior of antibiotics in soil.

Examining the Impact of Long-Term Industrialization on the Trace Metal Contaminants Distribution in Seawater of the Pula Bay, Croatia

In this study, we examined for the first time the spatio-temporal distribution of trace metal (TM) contaminants (Zn, Cd, Pb, Cu, Ni and Co) in the seawater column of Pula Bay. The bay has been known for decades as one of the most industrialized regions on the Croatian side of the Adriatic. Water samples were collected at 20 sites (at two depths) in four different seasons. The main physico-chemical parameters and DOC were measured along the TMs. The spatial distribution clearly showed that areas with industrial and nautical activities are sources of Zn, Pb and Cu, while no increase was observed for Cd, Ni and Co. Compared to the reference area outside the bay, the increase in dissolved concentrations ranged from a factor of 1.1 for Ni and Co to 8.5 for Pb. A clear difference in TM concentrations was observed between seasons, with concentrations being higher in warmer periods than in colder periods. The potential bioavailability/toxicity of TMs was examined using a passive sampling technique: diffusive gradients in thin films (DGT). In addition, a single-factor pollution index based on the available EQSs was used for both the dissolved TMs and DGT to assess the potential risk to the environment.

Technical development for in situ measurement of labile silicate in waters and soils

Silicon is an essential component of various environmental processes and biogeochemical cycles with silicate (H4SiO4) representing the bioavailable form of silicon in waters and soils. This study aimed to develop a method for accurately measuring labile silicate levels in waters and soils using diffusive gradients in thin-films (DGT) with a hydrogel diffusive gel and a modified precipitated zirconia (mPZ) binding gel. The diffusion coefficient of silicate in the diffusive gel, measured using an independent diffusion cell, was 6.77 × 10−6 cm2 s−1 at 25 °C. The mPZ gels were found to be effective at quickly and efficiently binding silicate, and a mixed solution of 0.5 mol L−1 NaOH and 0.5 mol L−1 H2O2 was determined to effectively elute silicate from mPZ gels, with an elution factor of 1.0. Furthermore, mPZ-DGT was found to be able to measure silicate at various pH levels (4.03–7.93) and ionic strengths (0.1–1000 mmol L−1 NaNO3). Field application of mPZ-DGT devices in an urban river revealed a decrease in silicate concentration downstream compared to upstream, likely due to increased human activity. Finally, mPZ-DGT was used in four sandy or loam soils to measure silicate concentration, and the results showed relatively small variations compared to those measured by CaCl2 and ammonium oxalate extractions. The findings suggest that mPZ-DGT is a useful tool for monitoring labile silicate concentrations and assessing its bioavailability in waters and soils.

Risk and mechanisms of phosphorus release at the sediment-water interface of lakes in cold and arid regions during non-frozen seasons.

In recent years, the eutrophication of lakes has accelerated in cold arid regions; the release of nutrients from sediments is an important contributor. The sequential extraction method, high-resolution peeper (HR-Peeper), and diffusive gradients in thin films (DGT) techniques were used to study the occurrence characteristics, release risk, and release mechanism of phosphorus (P) at the sediment-water interface (SWI) of Ulanor Wetland in the Hulun Lake Basin, Inner Mongolia, China. The mean total P concentration in overlying water was lower in August than that in May. Dissolved organic P (DOP) or particulate P (PP) was the main form of P in the overlying water. PP dominates in May and DOP in August. Refractory P was the main form of P in sediments. The concentrations of soluble reactive P and DGT-active P in the pore water of the sediment column were higher than those in the overlying water, and the concentrations were higher in August than those in May. Release of P in the wetland sediments occurred during the non-frozen seasons, with a higher risk in August than in May. The good linear correlation between dissolved P, Fe, and Mn in the DGT profiles verified their co-release due to the anaerobic reduction of Fe/Mn oxides. Moreover, alkaline sediments are also conducive to the release of sediment P. This study can provide data and theoretical support for eutrophication control in Ulanor Wetland and other similar water bodies in cold and arid regions.

Development and Field Application of a Diffusive Gradients in Thin-Films Passive Sampler for Monitoring Three Polycyclic Aromatic Hydrocarbon Derivatives and One Polycyclic Aromatic Hydrocarbon in Waters

Polycyclic aromatic hydrocarbon (PAH) derivatives are widely present in the environment, and some are more hazardous than their parent PAHs. However, compared to PAHs, PAH derivatives are less studied due to challenges in monitoring as a result of their low concentrations in environmental matrixes. Here, we developed a new passive sampler based on diffusive gradients in thin films (DGT) to monitor PAH derivatives and PAHs in waters. In the laboratory study, the XAD18-DGT device exhibited high adsorption rates and was demonstrated to be suitable for deployment in environmental waters on the timescale of months. The diffusion coefficients, D, were 5.30 × 10−6 cm2 s−1, 4.51 × 10−6 cm2 s−1, 4.03 × 10−6 cm2 s−1 and 3.34 × 10−6 cm2 s−1 for 9-fluorenone (9-FL), 1-chloroanthraquinone (1-CLAQ), 9-nitroanthracene (9-NA) and phenanthrene (Phe), respectively, at 25 °C. The DGT device’s performance was independent of pH, ionic strength, deployment time and storage time, indicating it can be widely used in natural waters. In the field study, the target pollutant concentrations measured by the DGT are in good accordance with those determined via grab sampling. Then, the DGT devices were utilized to quantify PAH derivatives and PAHs in several rivers in Hefei, China. This work demonstrates the feasibility of using the DGT technique to detect trace PAH derivatives and PAHs in waters.

Spatial Distribution, Ecological Risk Assessment, and Source Identification of Metals in Sediments of the Krka River Estuary (Croatia)

To evaluate the level of contamination and predict the potential toxicity risk, selected metal concentrations (Cd, Pb, Cr, Mn, Co, Ni, Cu, Zn, and As) were determined in 40 surface sediment samples from the stratified karstic Krka River estuary (Croatia). In addition, diffusive gradients in thin films (DGT) probes were deployed in situ to understand the mobilization mechanisms and bioavailability of metals in the sediment. The results show significant spatial differences between the upper and lower estuary, with the latter being more affected by anthropogenic pollution. The pollution assessment using the enrichment factor (EF), the geoaccumulation index (Igeo), and the pollution load index (PLI) showed a strong enrichment of metals in the lower part of the estuary, especially of Mn, Cu, Zn, Pb, and As. The statistical analysis (PCA) revealed the former ferromanganese factory and the port as major sources of pollution in the area. Nickel, Co, and Cr, although slightly elevated, may be attributed to the natural origin. The metal mobility in the estuarine sediment was primarily governed by early diagenetic processes (aerobic organic matter mineralization, Fe and Mn oxyhydroxide reduction), which caused the release of metals from the sediment into the pore water and subsequently into the overlying water column.

Diffusive Gradients in Thin-films as passive sampling tool for the measurement of labile species in fractionation analysis of metals (Fe, Mn, Cu, Zn and Pb) in beer

Fractionation analysis of Fe, Mn, Cu, Zn and Pb in beer is of high interest since their labile forms affect its stability and have implications for toxicity. In this study, we used the Diffusive Gradient in Thin-film (DGT) technique for the first time as a tool for passive sampling of labile species of Fe, Mn, Cu, Zn and Pb from beer. The validity of methodologies for total, total-dissolved and DGT-labile concentrations of Fe, Cu, Mn, Zn and Pb in beer was checked and then were applied to measure metals concentrations in two beer sorts: filtered and unfiltered (craft) beer. Commercial beer spiked with target analytes was used to check the linear accumulation of metals by DGT for 72 h DGT deployment period. The obtained determination coefficients were in the range of 0.986–0.998. The total concentrations of metals in beers determined by GFAAS were in the range of 60.4–957 µg/L (Fe), 58.0–206 µg/L (Mn), 45.6–314 µg/L (Cu), 70.0–313 µg/L (Zn) and 0.75–4.22 µg/L (Pb). Of these, the DGT-labile fractions of Fe, Cu, Mn, Zn and Pb were 5.0 – 7.8 µg/L Fe, 4.5 – 15.0 µg/L Cu, 23.1 – 37.0 µg/L Mn, 17.7 – 41.5 µg/L Zn and 0.15 – 0.35 µg/L Pb. This study provides a simple and reliable methodology for the fractionation of metals in beer.