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Crucian carp (Carassius auratus) is an omni-benthivorous fish common in many shallow lakes in China. The presence of crucian carp can contribute to the nutrient cycles in lakes and thus affect water quality. In this work, a two-by-two factorial mesocosm experiment was performed with crucian carp of different sizes and densities, to investigate their effects on the cycle of phosphorus (P). Results showed that nutrients in particulate form increased in overlying water due to crucian carp disturbance, especially for treatments with higher fish densities and larger individuals. Smaller individuals at high density have a greater ability to promote P release from sediment, due to a stronger combined effects of physical disturbance and excretion. Accumulation of feces led to sediment anaerobiosis and the reductive dissolution of iron oxide-hydroxide, which were the main factors affecting the desorption of P. Our results quantify the endogenous P diffusion fluxes across the sediment-water interface attributed to different densities and sizes of crucian carp disturbance, and suggest controlling crucian carp at low density and small size to minimize their impact on sediment P flux., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Chenxi Wu reports was provided by China Academy of Engineering. If there are other authors, they 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 © 2024 Elsevier B.V. All rights reserved.)

Extensive use of per- and polyfluoroalkyl substances (PFASs) has resulted in their widespread presence in natural waters. Concern for public health requires reliable measurement methods for determining their distribution and risks. Here, a sampling method based on diffusive gradients in thin films (DGT) was developed for measuring PFASs in drinking water sources. Fluorinated graphite (FG) particles were used to prepare the DGT binding gel for selective enrichment of trace PFASs in an aqueous environment. The FG-DGT method did not show sensitivity to relevant environmental parameters including pH (5.0-9.0), ionic strength (0.001-0.5 M), or DOM concentration (0-30 mg/L). The FG-DGT had enough capacity for deployment of up to four months. Six traditional and emerging PFASs including PFOS, PFOA, PFHpA, PFHxS, PFNA, and 6:2 FTSA at the ng/L level were detected in two major reservoirs serving as public drinking water sources by FG-DGT method coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). PFOA appeared at the highest observed concentrations in the drinking water sources. The research demonstrates that FG-DGT is an effective and efficient tool for monitoring PFASs in drinking water., 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 B.V. All rights reserved.)

In this work, several binding gels were successfully prepared in Diffusive Gradient in Thin-film (DGT) that targeted the inclusion of novel biomass-derived materials for the determination of the labile fraction of mercury (Hg) in water. First, five biomass-derived materials were tested and the descending order as a function of the average percentage of Hg removal in solution was feathers > biochar > cork > canola meal > rice husk. The best two materials were treated and pulverized into powder to be embedded in a hydrogel; and so, feathers were pyrolyzed preserving the sulfur contained in their keratin structure (FBC), and biochar (BC) was modified and pyrolyzed with sublimated sulfur (SBC) to increase the Hg sorption sites in its structure. Analysis by Energy Dispersive X-ray fluorescence (EDXRF) spectrometry confirmed that the different pyrolysis procedures increased sulfur absorption successfully. The efficiency of the new gels (BC, SBC and FBC) in agarose was evaluated by comparative Hg uptake tests, showing a larger efficacy in the following order: SBC > BC > FBC. To assess the suitability of their application in freshwater environments, novel DGT devices were also evaluated to determine their diffusion coefficients (D). This test was conducted under controlled laboratory conditions, with particular focus on the potential competence of trace elements (Mn, Cu, Zn, Ni, Pb, Cd and As), which are commonly present in natural waters affected by mining. A stronger linear relationship between the Hg uptake by binding layers and the deployment time were obtained for the DGT devices with SBC (R 2  = 0.948) vs. BC (R 2  = 0.885). Therefore, the D obtained for Hg were 8.94 × 10 -6  cm 2  s -1 for DGT-SBC and 5.12 × 10 -6  cm 2  s -1 for DGT-BC devices at 25 °C, both within the same order of magnitude reported by previous studies. The good performance obtained by DGT-SBC devices is a promising result and indicates the potential for valorization of waste materials in the DGT technique., 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 The Authors. Published by Elsevier B.V. All rights reserved.)

The mobilization of trace metals in the rhizosphere can be affected by the redox potential, which is closely related to the O 2 dynamics. This study examined the distributions of O 2 and trace metals in the rhizosphere of the subaquatic hyperaccumulator Leersia hexandra Swartz under chromium (Cr) stress using planar optodes and the diffusive gradients in thin films technique coupled with laser ablation inductively coupled plasma mass spectrometry. The O 2 concentrations and oxidized areas in the rhizosphere significantly increased with increases in the light intensity, air humidity, and atmospheric CO 2 concentrations (p < 0.05). The O 2 concentration first increased with increasing ambient temperatures, then decreased when the temperature increased from 25 to 32 ℃. The O 2 concentration in the rhizosphere was significantly decreased under Cr stress (p < 0.05), with a prolonged response time to the altered ambient temperature. Cr stress led to decreased mobilities of As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sb, V, W, and Zn in the rhizosphere, which were negatively correlated with the concentrations of O 2 . These results provide new insights into the role of changes in the O 2 concentration induced by the roots of hyperaccumulator plants in controlling the mobility of trace metals in soils., 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 B.V. All rights reserved.)

Recently, rare-earth elements (REEs) have attracted great interest due to their importance in several fields, such as the high-technology and medicine industries. Due to the recent intensification of the use of REEs in the world and the resulting potential impact on the environment, new analytical approaches for their determination, fractionation and speciation are needed. Diffusive gradients in thin films are a passive technique already used for sampling labile REEs, providing in situ analyte concentration, fractionation and, consequently, remarkable information on REE geochemistry. However, data based on DGT measurements until now have been based exclusively on the use of a single binding phase (Chelex-100, immobilized in APA gel). The present work proposes a new method for the determination of rare earth elements using an inductively coupled plasma‒mass spectrometry technique and a diffusive gradients in thin films (DGT) technique for application in aquatic environments. New binding gels were tested for DGT using carminic acid as the binding agent. It was concluded that acid dispersion directly in agarose gel presented the best performance, offering a simpler, faster, and greener method for measuring labile REEs compared to the existing DGT binding phase. Deployment curves obtained by immersion tests in the laboratory show that 13 REEs had linearity in their retention by the developed binding agent (retention x time), confirming the main premise of the DGT technique obeying the first Fick's diffusion law. For the first time, the diffusion coefficients were obtained in agarose gels (diffusion medium) and carminic acid immobilized in agarose as the binding phase for La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, which were 3.94 × 10 -6 , 3.87 × 10 -6 , 3.90 × 10 -6, 3.79 × 10 -6 , 3.71 × 10 -6 , 4.13 × 10 -6 , 3.75 × 10 -6 , 3.94 × 10 -6 , 3.45 × 10 -6 , 3.97 × 10 -6 , 3.25 × 10 -6 , 4.06 × 10 -6 , and 3.50 × 10 -6  cm 2  s -1 , respectively. Furthermore, the proposed DGT devices were tested in solutions with different pH values (3.5, 5.0, 6.5 and 8) and ionic strengths (I = 0.005 mol L -1 , 0.01 mol L -1 , 0.05 mol L -1 and 0.1 mol L -1 - NaNO 3 ). The results of these studies showed an average variation in the analyte retention for all elements at a maximum of approximately 20% in the pH tests. This variation is considerably lower than those previously reported when using Chelex resin as a binding agent, particularly for lower pH values. For the ionic strength, the maximum average variation was approximately 20% for all elements (except for I = 0.005 mol L -1 ). These results indicate the possibility of a wide range of the proposed approach to be used for in situ deployment without the use of correction based on apparent diffusion coefficients (as required for using the conventional approach). In laboratory deployments using acid mine drainage water samples (treated and untreated), it was shown that the proposed approach presents excellent accuracy compared with data obtained from Chelex resin as a binding agent., 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 B.V. All rights reserved.)

It is imperative to solve the problem of endogenous phosphorus (P) release from sediments in the governance of natural water bodies. Deciphering P migration and transformation patterns that are coupled to iron (Fe) and sulfur (S) cycling at the sediment-water interface (SWI) is the key to understanding the mechanisms underlying endogenous P release. In the present study, we deployed diffusive gradients in thin films (DGT) probes in situ at the SWI in Fuyang River, Hebei Province, China. When the probes were retrieved, the surrounding sediments were synchronously sampled. We analyzed the longitudinal spatiotemporal distribution of Fe, S, and P at the SWI. We also explored how functional bacterial community diversity was associated with the coupling reactions of Fe, S, and P as well as endogenous P release from sediments at the functional gene level. The results showed that labile Fe, S, and P occurred at low concentrations in sediments 0-2 cm below the SWI, while they were enriched in sediments at depths of 4-8 cm. The longitudinal distribution of different labile elements exhibited greater differences between October and February than regional differences, with higher concentrations at downstream locations than upstream locations. In February, Fe/Al-bound P and sulfide (S 2- ) concentrations increased in sediments compared with those in October owing to an increase in the relative abundances of dominant genera among P-mineralizing bacteria and sulfate-reducing bacteria. As a result, Fe in Fe-bound P precipitated as FeS 2 , which induced P remobilization and release into the overlying water. The spatiotemporal distribution patterns of functional genes related to P (phoD and ppk) and S (aprA) transformation were consistent with those of labile P and S, which strongly suggests that microorganisms played a role in driving and regulating the coupled cycling of P and S at the SWI., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Consumption of maize contaminated with heavy metals such as cadmium, nickel, and zinc threaten human health. For situ measuring the bioavailability of heavy metals, the diffusive gradients in thin films (DGT) is superior to other traditional methods. It is also important to find a method for predicting heavy metal enrichment in maize based on the DGT method. In this study, field surveys were conducted in the main maize producing areas of Tianjin, China. Heavy metal concentrations in maize grains were predicted by coupling DGT with traditional extraction methods. The results show that coupling DGT with soil solution can significantly improve prediction accuracy (Cd-R 2 = 0.908, Ni-R 2 = 0.903, and Zn-R 2 = 0.904). This indicated that DGT and soil solution were feasible predictors of heavy metal concentration in maize. The DGT induced fluxes in soil/sediment (DIFS) model was used to simulate the uptake process of heavy metals by DGT, and better reveal the desorption processes of heavy metals in soils. DIFS-based desorption processes were employed to characterize the resupply ability of heavy metals in soils. The coupling of DGT and DIFS parameters provided the best prediction accuracy in this study (Cd-R 2 = 0.920, Ni-R 2 = 0.928, and Zn-R 2 = 0.908). Predictions are slightly weaker for Zn than for Cd and Ni (Cd-P < 0.01, Ni-P < 0.01, and Zn-P < 0.05). The reason is that the average resupply type of Cd and Ni in soil is partially sustained while Zn is resupplied via diffusion only. The desorption rate k - 1 can excellently improve the prediction accuracy of DGT, which avoids the disadvantage that soil solution does not consider desorption. The coupling of DGT and DIFS parameters provides an accurate and reliable method for predicting heavy metal enrichment in maize., 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 © 2022 Elsevier B.V. All rights reserved.)

Potentially toxic elements (PTEs) in urban soil environments pose a noticeable risk to both ecosystem and human health; however, only a fraction of the elemental content is available for biota. To better know the potential risk of PTEs in the urban soil environment, geochemical fractionation, bioaccessibility, and potential bioavailability of four PTEs (Cd, Cu, Pb, and Zn) were investigated by the combined use of different methods. The results showed that a high non-residual chemical fraction is related to a high bioavailability of the selected elements. The ranges of labile concentration of Cu, Zn, Cd and Pb in all sampling sites measured by diffusive gradients in thin films (DGT) were 3.5-18.0, 14.2-26.5, 0.09-1.0, and 1.8-15.7 μg/L, respectively. The high non-residual contents pointed out a serious hazard to the urban environment. The bioaccessible concentrations in gastric and lung phases were closely positively correlated with DGT-measured content (r = 0.63-0.99, p < 0.05), suggesting the potential use of DGT for the prediction of PTEs risk to human health. Moreover, the correlation of DGT results with the soluble and reducible fractions of PTEs may allow DGT use for quick screenings of the PTEs fraction potentially mobilizable during flooding events in urban soil environments. Our study suggests that combing DGT, bioaccessibility and biogeochemical fractionation could provide a more accurate assessment of the urban environmental quality and be helpful for pollution control and urban planning., 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 © 2022 Elsevier B.V. All rights reserved.)

Most pharmaceuticals are found at trace concentrations in aquatic systems, but their continuous release and potential accumulation can lead to adverse health effects in exposed organisms. Concentrations can vary temporally, driven by variations in discharges of receiving waters, sorption to sediments, and other biotic and abiotic exchange processes. The principal aim of this research was to better understand the occurrence, trends, and dynamics of pharmaceuticals in a cold-climate, riverine environment. To this end, a suite of seven representative antipsychotic pharmaceuticals was measured upstream and downstream of two wastewater treatment plants (WWTPs) in Saskatchewan, Canada, located in the South Saskatchewan River and Wascana Creek, respectively, across three seasons. Concentrations of analytes were in the ng/L range and generally greater downstream of both WWTPs compared to upstream. Some compounds, including the tricyclic antidepressant amitriptyline, which was the most abundant analyte in water and sediment from both sites and across seasons, reached low μg/L concentrations. Data collected from this research effort indicate contamination with antipsychotic pharmaceuticals, with the potential to adversely impact exposed organisms., 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 © 2022 Elsevier B.V. All rights reserved.)

Geochemical behaviors of trace metals in the sediment profiles are crucial for predicting the associated environmental risks in aquatic ecosystems. However, the comprehensive transport of trace metals under both equilibrium and dynamic conditions is still unclear under the changing hydrological regime. Here, the equilibrium partitioning behaviors and remobilization of five trace metals (Ni, Cu, Zn, As, and Pb) in sedimentary profiles within the tributaries of the Three Gorges Reservoir were explored by the partitioning coefficient (K d ), diffusive gradients in thin films (DGT), and DGT induced flux in sediments (DIFS) model. According to the K d values, As posed the highest migration ability among the trace metals in the sediment profiles under equilibrium circumstances. Similarly, the dynamic processes of trace metals simulated by the DIFS model also suggested that As displayed the highest desorption rate despite having the lowest labile pool size. Moreover, all trace metals were classified as the "partially sustained" case, while the supply abilities of As and other trace metals were limited by the diffusion and the desorption kinetics, respectively. In addition, DGT-labile trace metals showed a diffusion trend from the sediment to the water column (except for Zn) at the sediment-water interface, indicating potential risks to water quality. Specifically, the equilibrium partitioning behaviors revealed the potential labile pool of trace metals in the solid phase, and the dynamic resupply process between the solid phase and porewater remained undetermined. In comparison, although DGT simulated the kinetic process of trace metals in the sediments, the labile pool of the trace metals could not be obtained. This study provided a holistic insight into the complementary trace metal behaviors under both equilibrium and dynamic conditions in the sediment and was beneficial to the water quality protection and internal pollution remediation in the aquatic environment., 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 © 2022 Elsevier B.V. All rights reserved.)

The release of trace metals caused by industrial effluents and anthropogenic activities has been recorded in the Xixi River estuary, southern China. However, a thorough understanding of the behavior of trace heavy metals in Xixi River sediments is lacking. A total of 12 sediment cores were collected in June and December in the upper estuary section and mouth of the estuary. Here, an in situ high-resolution sampling technique, namely, diffusive gradients in thin films (DGT), was employed to acquire profiles of trace element concentrations and the release of bioavailable metals from sediments in different seasons. A three-step Community Bureau of Reference (BCR) sequential extraction method was used to explore the chemical speciation of trace metals in different seasons and to thereby assess the release potential of trace elements in sediments. The BCR sequential extraction results showed that the trace metals Fe, Mn, Co and Pb were mainly in the residual fraction, which rarely influences living organisms. The total mobile fractions (F1 + F2 + F3) of all trace metals were higher in winter than in summer, suggesting that accumulation occurred from summer to winter. DGT measurements showed that the intensity of sulfate reduction was higher in summer than in winter because of the high temperatures and high organic matter in summer. The intensity of sulfate and Mn(III/IV) reduction increased from the upper estuary section to the lower estuary. Fe(III) reduction decreased in summer but increased slowly in winter. The Pearson correlation results showed that the release of DGT-labile Co in pore water was related to Mn(III/IV) reduction, while the release of DGT-labile Pb was basically not controlled by the Fe-Mn-S redox transition. Abnormally high DGT-labile Pb concentrations were observed at the sampling station (XR3) closest to the estuary in winter, which might have been caused by the high Pb content in the local micro-sediments., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A new diffusive gradients in thin films technique (HR-MPTS DGT) with mercapto-functionalized attapulgite in a binding gel was developed for simultaneous two-dimensional (2-D) chemical imaging of As III , Cr III and Sb III selectively at the submillimeter scale, combined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. The HR-MPTS DGT exhibited selective accumulation of As III , Sb III and Cr III (> 97%), yet negligible accumulation of As V , Sb V and Cr VI (< 2%). Accumulation of As III , Cr III and Sb III on the binding gel had a linear relationship (R 2 > 0.99) with the corresponding standardized laser ablation signals, proving the feasibility of LA-ICP-MS analysis. Analysis for As III , Cr III and Sb III was provided with favorable analytical precision (relative standard deviation <10%). With the purpose of evaluating the dynamics of As III , Cr III , Sb III and O 2 in the rooting zone, a hybrid sensor, which comprises the HR-MPTS gel overlying an O 2 planar optode, was deployed in rhizosphere sediments. Results showed that the consumption of both As III and Sb III due to the oxidation extended ~4.48 mm into the sediments, which was consistent with the extension length of the oxidized sediment layers around the roots created by O 2 leakage., 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 © 2022 Elsevier B.V. All rights reserved.)

Wetland type plays an important role in controlling the phosphorus (P) biogeochemical cycle, while its effect on labile P dynamics and coupling with iron (Fe) and sulfur (S) in coastal wetlands remains unclear. In this study, chemical sequential extraction and high-resolution diffusive gradients in thin-film (DGT) techniques were employed to investigate P forms, mobilization, and labile Fe-S-P coupling in several coastal wetland types [i.e., natural wetland (NW), aquaculture pond (AP), artificial (ARW) and natural restored wetlands (NRW)]. Compared with NW, AP decreased the total P by 40.6%. The concentrations of soil organic P and inorganic P (including NaOH-extractable P and HCl-extractable P) were significantly increased in ARW, but decreased in AP and NRW. DGT-labile P, Fe, and S concentrations changed significantly in different wetland types, and the labile P concentrations in AP were significantly higher than those in the others. Similar spatial distribution dynamics and significant positive relationships between labile P, Fe, and S concentrations in NW and AP confirmed that intense reduction in iron and sulfate are the key mechanisms regulating P mobilization. However, these relationships were decoupled in restored wetlands, suggesting that the Fe redox-coupled P mobilization and sulfate reduction were sensitive to wetland changes. The diffusion fluxes of P across the soil-water interface were positive in AP (0.619 pg·cm -2 ·s -1 ), indicating that P was released from soil to the overlying-water. We concluded that coastal wetland types altered soil P forms, availability, and labile Fe-S-P coupling, and the natural restored wetland could help stabilize the soil P pool and eventually controlled the mobilization and release of P., 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 © 2022 Elsevier B.V. All rights reserved.)

Microplastics are widespread in estuarine, coastal, and deep sea sediments. The influence of microplastics on mercury (Hg) methylation in paddy soils with different characteristics, however, has not been well reported. In this research, we conducted a microcosmic experiment using red soil and alkaline soil with 2%, 7% and 10% polyvinyl chloride microplastics (PVC-MPs). Diffusive gradients in thin film (DGT) were used to test bioavailable Hg 2+ and bioavailable methylmercury (MeHg) in soils. Results showed that PVC-MPs could decrease bioavailable MeHg concentrations both in red soil and alkaline soil. We demonstrated that these decreases could be due to three possible mechanisms: (1) PVC-MPs affected DOM composition, which resulted in a difference in combining capacity for bioavailable Hg 2+ ; (2) PVC-MPs decreased MeHg via changing soil properties (including sulfate and dissolved Fe); (3) PVC-MPs affected the abundance of Proteobacteria, Firmicutes, and hgcA gene in soils. Our results emphasized the significance of investigating effects of microplastics on specific contaminants to implement effective environmental remediation strategies in polluted paddy soils., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Chlorophenols (CPs) have been listed as priority control pollutants because of their high toxicity and wide range. An In-situ monitoring technique using diffusive gradients in thin films based on porous β-cyclodextrin polymers as binding materials (CDP-DGT), was established to monitor four typical CPs, namely, 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP), 2,4,5-Trichlorophenol (2,4,5-TCP), 2,4,6-Trichlorophenol (2,4,6-TCP) in water and soils. The performance of CDP-DGT are stable under the conditions of pH 3.5-9.3, ionic strength 0.001-0.500 mol L -1 and dissolved organic matter concentration 0-20 mol L -1 . The adsorption capacities of CDP-DGT for 4-CP, 2,4-DCP, 2,4,5-TCP, 2,4,6-TCP were 57.80 μg cm -2 , 98.82 μg cm -2 , 95.69 μg cm -2 and 98.91 μg cm -2 , respectively. The time-average weighted concentrations of four CPs determined by CDP-DGT at Sanjiangkou wharf (Yangtze river, China) were consistent with the results of grab sampling, indicating the feasibility of CDP-DGT application in actual water. In addition, the distribution of CPs in the red soil of Kunming and paddy soil of Yixing were also studied by CDP-DGT, and the desorption kinetics in the two soils were analyzed with the DIFS model. The higher the soil organic matter content is, the more CPs are distributed in the soil solid phase. CPs in both soils can be partially resupplied to soil solution from the soil solid phase and the higher the partition coefficient for labile CPs is, the stronger the supplement capacity is., 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 © 2021 Elsevier B.V. All rights reserved.)

Arsenic (As) is a naturally occurring element in the Earth's crust, exhibiting toxicity towards a wide range of living organisms. Its properties and environmental dynamics are strongly regulated by its speciation, and the species As(III) and As(V) are the most commonly found in environmental systems. Recently, high concentrations of As were found in saline-alkaline lakes of the Pantanal (Brazil), which is the largest wetland area in the world. Therefore, we evaluated As contamination and its redox speciation (As(III) and As(V)) at the soil/water interface of biogeochemically distinct saline-alkaline lakes of Pantanal wetlands (Brazil). Both conventional sampling and in situ diffusive gradients in thin films (DGT) technique were employed. Zirconium oxide and 3-mercaptopropyl were used as ligand phases in DGT to selectively bind As species. High concentrations of total dissolved As in a shallow water table were found (<2337.5 μg L -1 ), whereas levels in soils were up to 2.4 μg g -1 . Distinct scenarios were observed when comparing speciation analysis through spot sampling and DGT. Considering spot sampling, As(V) was the main species detected, whereas As(III) was only detected in only a few samples (<4.2 μg L -1 ). Conversely, results obtained by DGT showed that labile As(III) dominated arsenic speciation at the soil/water interface with levels up to 203.0 μg L -1 . Coupling DGT data and DGT induced fluxes in sediments and soils model allowed obtaining kinetic data, showing that the soil barely participated in the arsenic dynamics on the shore of the lakes, and that this participation depends on the evapoconcentration process occurring in the region. Therefore, soil acts like a nonreactive matrix depending on the natural concentration process. In addition, our results reinforced the different geochemical characteristics of the studied saline-alkaline lakes and highlights the importance of robust passive sampling techniques in the context of metal/metalloid speciation in environmental analysis., 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 © 2021 Elsevier B.V. All rights reserved.)

A new diffusive gradients in thin films technique (HR-ZCA DGT) was developed for simultaneous two-dimensional (2-D) chemical imaging of sulfides, metallic cations and oxyanions (S, Cd, Co, Fe, Cu, Mn, Ni, Pb, Zn, As, Cr, Mo, Sb, Se, V, P and W) at the submillimeter scale, combined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. A novel binding gel was prepared using a double precipitation method with AgI and zirconium oxide (Zr-oxide) deposited sequentially on a preformed Chelex-100 resin gel. A good linear relationship was observed (R 2 >0.99) between mass accumulation of the 17 assessed elements on the binding gel and the corresponding standardized laser ablation signals (signals of elements divided by signals of internal standard 13 C), proving the feasibility of LA-ICP-MS analysis. Good analytical precision (RSD<12 %) was achieved for all 17 elements. A hybrid sensor comprising the novel DGT binding gel overlying an O 2 planar optrode was then tested in sediments to evaluate the dynamics of O 2 and multiple elements. Results showed that the mobility of As, P and W were controlled by precipitation/dissolution processes with Fe/Mn oxides. V, Co, Ni, Zn, Mo, Cd and Sb were released at the sediment surface with the oxidation of iron sulfides., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Platinum group elements (PGEs) are among the least abundant in the continental crust. They have become excellent tracers of anthropogenic activities, particularly due to their use in catalytic converters or in the medical industry. However, their quantification in environmental matrices is still problematic because of their low concentrations combined with the presence of interfering elements. Preconcentration methods are therefore necessary to measure accurate concentrations. In this study, the quantification of Ir, Rh, Ru, Pd and Pt was studied in depth by focusing on two resins: AG MP-1 (anion exchange) and Purolite® S-920 (chelating) with the aim of developing passive Diffusive Gradients in Thin films (DGT) samplers as in-situ pre-concentration tools. The characteristics of both resins (e.g. adsorption, elution, selectivity, etc.) were studied and the diffusion coefficients of PGEs in different matrices were determined. For the first time, carcinostatic platinum-based drugs were also studied. Better rates and percentages of adsorption were observed for S-920 while AG MP-1 was more selective with regard to spectral interferents and easier to elute. The diffusion coefficients of PGEs were resin-dependent, particularly for carcinostatic platinum-based drugs. For the first time, the applicability of these DGT samplers dedicated to PGEs was demonstrated in the field after their deployment in two wastewater treatment plants in Northern France for which concentrations were found to range from few pg L -1 (Ir, Ru) to few ng L -1 (Pt)., (Copyright © 2020 Elsevier B.V. All rights reserved.)

As a trace heavy metal, lead (Pb) has many anthropogenic applications but also produces many environmental pollution problems because of its high toxicity. In this study, we combined two in situ high-resolution sampling techniques - high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) - with the DGT-induced fluxes in sediment (DIFS) model to explore the mechanism of Pb release and resupply between sediments and pore water in the lower reaches and estuary of the Jiuxi River and the adjacent coast. An analysis of the chemical forms of Pb in the sediments showed that the content of the acid-extractable fraction (F1) was higher at the coastal site than at the other sampling sites, which indicates that Pb in the coastal sediments had greater activity and was more likely to cause Pb pollution. The apparent diffusion fluxes of Pb across the sediment-water interface (SWI) in the lower reaches, estuary and coastal zone are negative, and the absolute value of Pb flux in the estuary is several times higher than that in the other two stations, indicating a strong downward Pb diffusion trend, which may be due to water pollution caused by the nearby sewage outlet. As an insensitive element to redox, Pb did not exhibit an obvious correlation with Fe. In particular, the high Pb concentration and strong downward diffusion trend of the overlying water in the estuary caused the significant negative correlation between Pb and Fe. The calculated results of the DIFS model show that the reduced layer in the intertidal zone along the coast has the highest R value, the highest desorption rate (k - 1 ) and the shortest response time (T c ), indicating that sediment particles in the coastal intertidal zone supply Pb to the pore water at the fastest rate; consequently, Pb pollution in the coastal zone is worthy of further attention., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Trivalent chromium has historically been considered as an environmentally benign micronutrient due to its low mobility; however, its kinetic process in soil remains poorly understood. Here, the labile fraction and kinetics of Cr(III) in contaminated soils were explored using diffusive gradients in thin films (DGT) and the DGT-induced fluxes model. In contrast to the low mobility of Cr(III) in soils reported by the classic equilibrium partitioning method, we observed steady resupply from the solid phase through a dynamic process, wherein Cr(III) in the soils were maintained by an intermediate resupply rate with the R values at their maximum (R max ). The resupply of Cr(III) was influenced by the kinetic parameters and soil properties: (i) the resupply ability (R-R diff ) was influenced by pH and response time (T c ); (ii) R max , was controlled by pH, T c , and the desorption rate (k - 1 ); (iii) k - 1 was influenced by pH and soil texture. This study presents the new information regarding the kinetics of Cr(III) in soils and demonstrates that Cr(III) is steadily resupplied by soil, which is not captured by equilibrium-based methods, furthering our insight of the geochemical behavior of Cr(III). This information was essential for understanding the toxicity of Cr and improving remediation., 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 © 2020 Elsevier B.V. All rights reserved.)

To determine the bioavailability and translocation of metal oxide nanoparticles (MONPs) in the soil-rice plant system, we examined the accumulation and micro-distribution of ZnO nanoparticles (NPs), CuO NPs and CeO 2 NPs (50, 100 and 500 mg/kg) in the paddy soil and rice plants under flooded condition for 30 days using single-step chemical extraction and diffusive gradients in thin films (DGT) technique combined with micro X-ray fluorescence spectroscopy (μ-XRF). The results show that various MONPs changed the soil properties, especially the redox potential was enhanced to -165.33 to -75.33 mV compared to the control. The extraction efficiency of Zn, Cu and Ce in the paddy soil from high to low was EDTA, DTPA, CaCl 2 and DGT. Moreover, exposure to 500 mg/kg CuO NPs and CeO 2 NPs induced the primary accumulation of Cu and Ce elements in rice roots as high as 235.48 mg Cu/kg and 164.84 mg Ce/kg, respectively, while the Zn concentration in shoots was up to 313.18 mg/kg under highest ZnO NPs with a 1.5 of translocation factor. The effect of MONPs on the plant growth was mainly related to the chemical species and solubility of MONPs. Micro-XRF analysis shows that Zn was mostly located in the root cortex while Cu was primarily accumulated in the root exodermis and few Ce distributed in the root. Pearson correlation coefficients indicate that only DTPA-extracted metals in soil were significantly and well correlated to the Zn, Cu and Ce accumulation in rice seedlings exposed to MONPs. This work is of great significance for evaluating the environmental risks of MONPs in soil and ensuring the safety of agricultural products., 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 © 2020 Elsevier B.V. All rights reserved.)

Water, sediment, and biota from two streams on the Savannah River Site were sampled to study mercury (Hg) biogeochemistry. Total and methyl- Hg (MHg) concentrations were measured for all samples, speciation models were used to explore Hg speciation in the water, and Diffusive gradients in thin films (DGT) were applied to indicate the vertical profiles of labile Hg (DGT-Hg). Trophic position (δ 15 N) was estimated for biota and used to establish MHg biomagnification model. The speciation model indicated Hg methylation in the water occurred on settling particles and the most bioavailable Hg species to bacteria were complexes of inorganic Hg and labile organic ligands. Correspondingly, dissolved organic carbon concentrations were positively related to MHg concentrations in the water. In the sediment, the sharp increase of DGT-Hg around the sediment water interface underscores the importance of this interface, which determines the differences in the accumulation and generation of labile Hg among different waterbodies. The positive correlation between sediment MHg and sulfate concentrations suggested possible methylation reaction by dissimilatory sulfate reducing bacteria in the sediment. The food web magnification factors of MHg were 9.6 (95% CI: 4.0-23.4) and 4.4 (95% CI: 2.5-7.7) for the two streams established with trophic data of biofilm, invertebrates, and fish. Meanwhile, DGT-Hg concentrations in the water were positively correlated to biofilm Hg concentrations, which can be combined with the MHg biomagnification model to generate a modified biomagnification model that estimate MHg bioaccumulation with only labile Hg concentrations in the water. With this approach, Hg accumulation in abiotic and biotic environmental compartments was connected and the different bioaccumulation patterns of Hg in different waterbodies were explained with both geochemical and biological factors., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Due to the limited aeration capacity of current aeration techniques at the sediment-water interface (SWI), we developed a specialized aeration material aimed at the SWI, known as oxygen nano-bubble-modified minerals (ONBMMs). Furthermore, we simulated its aeration efficiency at the SWI and the control effects of internal phosphorous (P) release under anaerobic conditions during 20 days. High resolution diffusive gradients in thin films (DGT) and Planar luminescent optode (PO) technologies were used to measure the temporal variation of reactive P, reactive Fe (II) and dissolved oxygen (DO) of the SWI. These results show that ONBMMs can effectively increase the content of DO at the SWI and decrease the release flux of internal P from sediments. The use of ONBMMs reduced 97.9% of the soluble reactive P concentration of the overlaying water and reduced the release flux of DGT-P from sediments by 78.9%. Inhibition of reductive dissolution of FeP from sediments was the primary principle that effectively inhibited the input of internal P by ONBMMs. Therefore, ONBMMs are potentially promising technology for the treatment of internal P pollution in eutrophic lakes., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A diffusive gradients in thin films (DGT) method using a new high-capacity cerium oxide (CeO 2 ) binding gel, for the first time, was developed for measuring dissolved inorganic arsenic in freshwater and seawater. The capacities of the new CeO 2 binding gel were 682 μg and 375 μg for As III and As V , respectively. The masses of As III and As V accumulated by CeO 2 -DGT device increased linearly with time and agreed well with the theoretical value calculated by DGT equation. The arsenic accumulation by CeO 2 -DGT was independent of pH (4.05-9.04) and ionic strength (0.1-750 mM), and common anions including CO 3 2- , SO 4 2- , Cl - and PO 4 3- had no obvious interference. CeO 2 -DGT showed excellent long-term deployment performance in freshwater and synthetic seawater. Field trials with CeO 2 -DGT achieved successfully the time-weighted-average concentrations of total inorganic arsenic in reservoir water (1.38 ± 0.09 μg/L) and coastal seawater (0.45 ± 0.06 μg/L). The results were comparable to those measured by grab sampling. The proposed method was reliable and robust for in-situ measurements of dissolved inorganic arsenic in environmental waters., (Copyright © 2018 Elsevier B.V. All rights reserved.)

There is a requirement for simultaneous measurements of diverse analytes to reveal their biogeochemical couplings in the environment. In this study, we first realized simultaneous measurements of three types of analytes, including sulfide [S(-II)], metallic cations, and oxyanions by diffusive gradients in thin films (DGT) using a new mixed ZrO-CA binding gel. The ZrO-CA gel exhibited faster absorption rates for oxyanions than previously reported ZrO-Chelex gel, and faster absorption rates for cations when the gel was saturated with S(-II). It implies that there were synergistic effects among the three binding agents which should facilitate the DGT uptake. The technique's performance was validated under laboratory conditions in mixtures of dissolved compounds. It was shown to be independent of the solution's pH (5-9) and ionic strength (from 1 to 3 mM to 750 mM). The capacities of the ZrO-CA DGTs without or with [S(-II)] saturation to measure As(III), As(V), Cd(II), Fe(II), and P(V) individually were significantly greater than those of other DGTs except for Zr-oxide based DGTs. The measurements in sediment revealed similar distributions of three types of analytes in the vertical profile and confirmed the feasibility and advantage of the ZrO-CA DGT. This study provides a new perspective to enhance the DGT capability in measurement of multiple analytes through utilizing the synergistic effects among different binding agents., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The pollution of antibiotics, including tetracyclines (TCs), in aquatic environments has become an issue of concern in recent years. Herein, an in situ sampling of TCs in pig breeding wastewater that utilizes the technique of diffusive gradients in thin films (DGT), based on commercial nanosized ZnO (nanoZnO) particles as the potential effective binding agent and a polyethersulfone (PES) membrane as the diffusion layer, was developed. The diffusion coefficients of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in a PES membrane at 25 °C were (1.37 ± 0.06) × 10 -6  cm 2  s -1 , (1.29 ± 0.05) × 10 -6  cm 2  s -1 and (1.94 ± 0.07) × 10 -6  cm 2  s -1 , respectively. The results showed that the adsorption capacities of a gel disc containing 2.5 g L -1 of nanoZnO particles were as high as 3.93 ± 0.20 mg disc -1 for TC, 3.21 ± 0.20 mg disc -1 for OTC and 4.62 ± 0.22 mg disc -1 for CTC. Both a solution pH in the range of 5-9 and an ionic strength (as pNaCl) in the range of 1-3 had an insignificant influence on the TCs uptake by nanoZnO-DGT samplers. There was no significant influence of fulvic acid or tannic acid on the TC uptake by nanoZnO-DGT samplers at the tested mass ratios. For all spiked freshwater samples, there was no notable interference of matrices on the performance of the nanoZnO-DGT samplers, suggesting that the nanoZnO-DGT samplers yielded satisfactory results for the uptake of TCs at concentrations existing in the spiked freshwater samples. Field deployment of the nanoZnO-DGT samplers in pig breeding wastewater also exhibited excellent precision and accuracy, indicating that the nanoZnO-DGT samplers could be used as a promising method for the in situ sampling of TC antibiotics in aquatic environments., (Copyright © 2018. Published by Elsevier B.V.)

As the sole drinking water source for Beijing City, Cd has been previously assessed as the major contaminant in Miyun Reservoir (MYR) riparian soils. However, the potential release risk of Cd in such soils, and the labile-Cd release-resupply process from the soil solid phase to solution after water impoundment remain poorly understood. We established a geochemical baseline concentration (GBC) of Cd in MYR riparian soils, combined with the diffusive gradient in thin films (DGT) technique and DGT-induced fluxes in soil (DIFS) model, to reveal a dynamic release-resupply process and influencing factors of labile Cd in riparian soils. The results showed that Cd GBC in riparian soils was 0.12 mg/kg, which was higher than the Cd background value (BV) for Beijing. Using Cd GBC as BV to assess the Cd contaminant level, the geo-accumulation index showed that Cd in riparian soils was at the uncontaminated level. In addition, Cd in the soils belonged to the non-residual fraction using the Community Bureau of Reference method. Cd mobility coefficients (F1/C Total -Cd) of soils at low elevation had relatively high values, implying that Cd may be released during the initial impoundment of the MYR. Moreover, correlation analysis was used to found the major influencing factors between DGT-labile Cd and several parameters. The results showed that the DGT-labile Cd was positively correlated to the reducible and oxidizable fraction, C DGT -Fe, and total organic carbon, illustrating that the release of Cd from soils was controlled by Fe oxides and organic matter. The resupply ability (R values) and DIFS model parameters revealed that Cd in MYR soils belonged to the partially sustained case, and the slow desorption rate suggested that the release risk of Cd was low in the MYR riparian soils., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new theoretical method was established for the combinatorial calculation of the dissociation rate constant (K -1 ) of the metal-organic complexes (MLs), the concentration of free ionic soil metals (C M ), the labile concentration of soil metal-organic complexes (C ML ) based on diffusive gradients in thin-films (DGT) technique with a range of diffusive layer thicknesses (0.053-0.173 mm) in soils. The fitting results agreed well with the determined values. The values of K -1 , C ML and C M were calculated without other morphological analysis software and the fitting results agreed well with the determined values with some advantages such as the use of fewer hypothetical parameters, ease of calculation, the full embodiment of the contribution of MLs to the labile content. According to the results of model fitting, cation exchange capacity and soil organic matter were found to be the key environmental factors for K -1 values of Cd and Ni, respectively. The labile contents of Cd and Ni in soil were closely related with pH, soil organic matter and the total contents of heavy metals., (Copyright © 2018. Published by Elsevier Inc.)

Diffusive gradients in thin films (DGT) can achieve the time-weighted-average (TWA) concentrations of analytes in the period of deployment. Here we developed an approach based on DGT with a novel binding gel using porous carbon material (PCM) derived from metal-organic framework (MOF) for in-situ measurement of antibiotics in water samples. The diffusion coefficients of 20 antibiotics (nine sulfonamides, ten fluoroquinolones, and trimethoprim) in agarose diffusive gel were 1.41 × 10 -6  cm 2 /s to 4.75 × 10 -6  cm 2 /s at 25 °C. The capacity of PCM binding gel toward the antibiotics was ~100 μg per gel disc. The masses of the antibiotics accumulated by PCM-based DGT increased linearly with time, and they were almost independent of pH (4.2-8.4) and ionic strength (1-500 mM). The performance of the novel DGT was evaluated using freshwater and synthetic seawater spiked with the antibiotics in laboratory. The results showed good agreement with the theoretical predications except sulfacetamide. The detection limits achieved by the DGT with three devices together for deploying up to seven days were 1.0-18.0 ng/L. Field deployment in municipal wastewater treatment plant effluent and seawater showed that the TWA concentrations of antibiotics were 3.8-1342.5 ng/L and 5.6-43.3 ng/L, respectively, which were comparable to those measured by grab sampling. The proposed DGT was an efficient tool for the measurement of antibiotics in environmental waters., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Four analytical techniques are compared: AGNES (Absence of Gradients and Nernstian Equilibrium Stripping), LASV (Anodic Stripping Voltammetry with Linear stripping), DGT (Diffusive Gradients in Thin films) and PIM (Polymer Inclusion Membranes). These techniques have been designed to provide the free ion concentration or a labile fraction, complementarily contributing to an integrated description of speciation and availability. Their simultaneous application to the determination of free Zn concentrations or labile fluxes in seven solutions of a hydroponic medium reveals characteristics of each technique and correlations between their results. All dynamic results can be interpreted in terms of a general theoretical framework on fluxes. Indeed, in techniques under diffusion-limited conditions in the sample, the flux can be split into the free contribution (linearly proportional to the free fraction), plus the contribution of the complexes (where mobility, lability and abundance of complexation are intertwined). A methodology to compute lability degrees is developed. Measurements with PIM devices confirm that diffusion in the sample solution is not rate limiting, so its flux is proportional to the free metal in the donor solution. A proportionality between the responses of any given two techniques is observed, which suggests that, for the low ligand-to-metal concentration ratios used in the present work, any of these techniques would correlate similarly with uptake, toxic or nutritional measurements., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new method for simultaneous measurement of fifteen rare earth elements (REEs) [La (Ⅲ), Ce (Ⅲ), Pr (Ⅲ), Nd (Ⅲ), Sm (Ⅲ), Eu (Ⅲ), Gd (Ⅲ), Tb (Ⅲ), Dy (Ⅲ), Ho (Ⅲ), Er (Ⅲ), Tm (Ⅲ), Yb (Ⅲ), Lu (Ⅲ), and Y (Ⅲ)] was established in this study using the diffusive gradients in thin films (DGT) technique with Chelex ® 100 binding gel. Five different types of ion exchange resins (Chelex ® 100, D418, D001-cc, 001 × 7, and HSTY ® -SS) were selected for the initial investigation of their adsorption performance for REEs. The Chelex ® 100 binding gel had the greatest uptake efficiencies of >95% for the fifteen REE ions, which was used for all subsequent experiments. The binding gel exhibited rapid binding dynamics to REEs in mixed solution of the fifteen REE ions. Elution efficiencies ranging from 86.5% to 93.8% for these REEs were obtained based on extraction using 2.0 M HCl. The Chelex ® 100 DGT uptake of the fifteen REE ions increased linearly with the deployment time and found to be independent of pH (3-9) and ionic strength (3 mM-100 mM). The capacities of Chelex ® 100 DGT for measurement of the mixed elements were determined at a range of 5.39-6.75 μg cm -2 . Application of the DGT for soil analysis showed that Chelex ® 100 DGT was a useful tool in simultaneous measurement of the fifteen REE ions, even in a soil with high concentrations of REEs. This study demonstrated the advantage of Chelex ® 100 DGT in simultaneous measurement of the fifteen REE ions due to high uptake efficiencies and a wide tolerance to environmental interference., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The mobility and transfer of trace metals in sediments are vital to understanding trace metals environmental behavior in water environment. However, as a predominant aquatic carcinogen, an effective method for assessing the release and deposition for Cr at the sediment-water interface (SWI) is still not clearly understood. Here we established a comprehensive methodology to evaluate the release risk of Cr at the SWI combining regional geochemical baseline (RGB) and diffusive gradients in thin films (DGT). Sediment cores and water samples were collected in the two tributaries and mainstream of the Three Gorges Reservoir, which is the world's largest man-made hydroelectric station. Results showed that the calculated Cr carcinogenic risks in surface water did not exceed US EPA maximum recommended level. The RGB of Cr (85.53 ± 14.44 mg/kg) were calculated and the differentials between Cr concentration and RGB in surface sediments showed the average anthropogenic contribution rate was 6.03% and the upstream of Meixi River (MX-S) and mainstream were influenced by anthropogenic activities. The net diffusive flux using DGT showed that Cr in the midstream of Caotang River and MX had the potential to move upwards into the overlying water. Furthermore, combining the results of differential (Cr concentration vs. RGB) and the net flux, MX-S was the only site with a risk of Cr release. To the best of our knowledge, this study is the first attempt to combine RGB and DGT to scientifically assess metal release at SWI and provided a new perspective to comprehensively assess metal pollution in water environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

DGT (diffusive gradients in thin films) technique and DIFS (DGT induced fluxes in sediment) model are firstly designed for macrophyte-rhizobox system and in-situ macrophytes in Lake Erhai. Dynamics of phosphorus (P) transfer in Zizania latifolia (ZL) and Myriophyllum verticiilatur (MV) rhizosphere is revealed and phytoremediation performance for P in sediment is evaluated. Dynamic transfer process of P at DGT/sediment interface includes (i) diffusion flux and concentration gradients at DGT(root)/porewater interface leading to porewater concentration (C 0 ) depletion and (ii) P desorption from labile P pool in sediment solid to resupply C 0 depletion. Fe-redox controlled P release from Fe-bound P (BD-P2) and then NH 4 Cl-P1 in rhizosphere sediment resupplies porewater depletion due to DGT (root) sink. K d (labile P pool size in solid phase), r (resupply ratio) and kinetic exchange (Tc and k -1 ) lead to change characters of DIFS curves of (1) r against deployment time and (2) C solu (dissolved concentration) against distance at 24 h. They include two opposite types of "fast" and "slow" rate of resupplies. Sediment properties and DIFS parameters control P diffusion and resupply in rhizosphere sediment. Phytoremoval ability for sediment P in lake is estimated to be 23.4 (ZL) or 15.0 t a -1 (MV) by "DGT-flux" method., (Copyright © 2018 Elsevier B.V. All rights reserved.)

As coastal waters in many regions of the world have been polluted by organic micro-pollutants such as antibiotics that can promote the development of resistance genes, it is of importance to monitor the levels of antibiotics in coastal waters. For this purpose, a reliable and robust sampling approach based on diffusive gradients in thin films (DGT) was developed in this study. The DGT measurement can provide a time weighted average concentration of pollutants. A binding material (resin XDA-1) with a high adsorption capacity for antibiotics, which can resist the pH and ionic strength of seawaters, was selected. The DGT sampler exhibited linear accumulation for 20 antibiotics during a 12h deployment. The antibiotic measurement by the sampler was not affected by pH in the range of 7.3 to 8.9 and ionic strength in the range of 0.5 to 0.8M. After an 8-hour in situ DGT sampling, 10 antibiotics were detected in Dalian coastal seawaters with the concentrations ranging from 2.6 to 44.8ngL -1 , which was comparable to the results measured by an active sampling method. This study can be a first attempt to construct DGT sampler for determining antibiotics in seawaters., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The effectiveness of sediment dredging for the control of internal phosphorus (P) loading, was investigated seasonally in the eutrophic Lake Taihu. The high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were used to measure the concentrations of soluble Fe(II) and soluble reactive P (SRP) as well as DGT-labile Fe/P in the non-dredging and post-dredging sediments. The P resupply kinetics from sediment solids were interpreted using DGT Induced Fluxes in Sediments (DIFS) modeling. The results showed no obvious improvement in water and sediment quality after dredging for 6years, due to their geographical proximity (a line distance of approximately 9km). However, dredging significantly decreased the concentrations of soluble Fe(II)/SRP and DGT-labile Fe/P in sediments, with effects varying at different depths below the sediment-water interface; More pronounced effects appeared in January and April. The diffusive flux of pore water SRP from sediments decreased from 0.746, 4.08 and 0.353mg/m 2 /d to 0.174, 1.58 and 0.048mg/m 2 /d in April, July and January, respectively. DIFS modeling indicated that the P retention capability of sediment solids was improved in April in post-dredging site. Positive correlations between pore water soluble Fe(II) and SRP as well as between DGT-labile Fe and P, reflect the key role of Fe redox cycling in regulating dredging effectiveness. This effect is especially important in winter and spring, while in summer and autumn, the decomposition of algae promoted the release of P from sediments and suppressed dredging effectiveness. Overall, the high-resolution HR-Peeper and DGT measurements indicated a successful control of internal P loading by dredging, and the post-dredging effectiveness was suppressed by algal bloom., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The diffusive gradients in thin films (DGT) technique is a useful tool for assessing metal bioavailability in sediments. However, the DGT technique has not been used to predict metal bioaccumulation in plants grown in sediments in river systems. In this study, the DGT technique was evaluated for predicting metal bioaccumulation in Phragmites australis growing in contaminated sediments. In sediments with high levels of contamination, release of DGT-labile Cr, Zn, Cu, and Cd occurred, which resulted in high bioaccumulation of these metals in P. australis. Bioaccumulation of Cr, Cu, Zn, and Cd was strongly correlated with the metal concentrations in the sediments measured by the DGT technique. By contrast, the correlation between sediment content and bioaccumulation for As was weak. There were significant negative correlations between the content of Ni in the plant tissues and the contents of the other metals. Overall, the DGT technique provided predictions of metal bioaccumulation similar to those obtained using total metal measurements in multiple polluted sediment samples. Therefore, DGT analysis could be used for assessing heavy metal bioavailability, and metal bioaccumulation in P. australis was not all significantly correlated with the bioavailability concentrations of metals in river sediments., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Fertilizers produced from heterogeneous, phosphorus-rich biowastes are becoming increasingly relevant. Treatment and processing (combustion, pyrolysis, anaerobic digestion, etc.) increase the diversity of their physico-chemical composition even further. We investigated several approaches to characterize P availability from a set of 13 contrasting fertilizers. We tested them directly using standard fertilizer extractions, as well as a continuous, sink-based P extraction (iron bag) method. We also performed Olsen, CAL and diffusive gradients in thin films (DGT) tests on fertilized soil. Standard extractions correlated only weakly, whereas the iron bag method correlated highly (0.732 <0.85) with plant P uptake. Among the tests conducted on fertilized soils, DGT was equivalent or slightly better than Olsen, showing R 2 s of about 0.90 for P uptake and plant growth. Our results suggest that the validity of standard P fertilizer tests needs to be reassessed in the context of increasingly diverse recycling fertilizers., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A modified diffusive gradients in thin films (DGT) technique uses both a mixed binding layer (PrCH and A520E resins for NH 4 -N and NO 3 -N, respectively) and multiple binding layers (Metsorb binding layer for PO 4 -P overlying the mixed binding layer) for the simultaneous measurement of dissolved inorganic nitrogen (nitrate and ammonium) and phosphate in freshwater (INP-DGT). High uptake and elution efficiencies were determined for a mixed (PrCH/A520E) binding gel for dissolved inorganic nitrogen and an agarose-based Metsorb binding layer for PO 4 -P. Diffusion coefficients (D) obtained from DGT time-series experiments (conductivity 180 μS cm -1 ) for NH 4 -N, NO 3 -N and PO 4 -P agreed well with those measured using individual DGT techniques in previous studies, but were characterised over a wider range of ionic strengths here. D for NO 3 -N and PO 4 -P were constant over a range of ionic strengths (between 100 and 800 μS cm -1 ) while the diffusion coefficient for NH 4 -N decreased with increasing ionic strength, as reported previously. The measurement of NH 4 -N, NO 3 -N and PO 4 -P using the INP-DGT was independent of pH (3.5-8.5) and quantitative over varying ionic strength ranges (up to 0.004 mol L -1 NaCl for NH 4 -N, up to 0.014 mol L -1 NaCl for NO 3 -N and over 0.1 mol L -1 NaCl for PO 4 -P) for a 24 h deployment time. Performance of INP-DGT in synthetic freshwaters with differing conductivity indicated the three nutrients were affected differently, with NH 4 -N measurements being most sensitive. Representative performance was determined for NO 3 -N (90-330 μS cm -1 ) and PO 4 -P (all tested conductivities) over a 72 h deployment period and for NH 4 -N (<330 μS cm -1 ) over a 24 h deployment period. Field validations showed that the ratios of INP-DGT concentrations to the average concentrations from grab samples were generally between 0.80 and 1.13 over 24 and 48 h deployment periods. To ensure the representative performance of INP-DGT for all three nutrients, the conductivity should not exceed 400 μS cm -1 and deployment times should be no longer than 24 h. The results of this study have demonstrated that INP-DGT could provide a cost-effective monitoring technique for measuring time-weighted average concentrations of dissolved inorganic nutrients in many freshwaters., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A new method for the simultaneous measurements of eight cations [Fe(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II)] and eight oxyanions [P(V), V(V), Cr(VI), As(III)/As(V), Se(VI), Mo(VI), Sb(V), and W(VI)] was established in this study using the diffusive gradients in thin films (DGT) technique with an improved ZrO-Chelex binding gel. The binding kinetics of each analyte in a mixed solution indicated a rapid uptake on the ZrO-Chelex gel. The anions exhibited slower absorption rates compared to the cations, which did not affect the DGT uptake. Stable elution efficiencies for these cations and anions were obtained based on a two-step extraction procedure using 1.0 M HNO 3 for elution of the cations followed by a mixed solution containing 0.2 M NaOH and 0.5 M H 2 O 2 for elution of the anions. Simultaneous measurements of the cations and anions with the ZrO-Chelex DGT were validated in mixed solutions and found to be independent of solution pH (5-9) and ionic strength (2-3 mM to 750 mM). The capacities of the ZrO-Chelex DGT for single measurements of Fe(II), P(V), Cd(II), As(III), and As(V) were determined at 99.5, 127.6, 301.2, 33.3, and 87.4 μg cm -2 . Except for Se(VI) in seawater, accurate measurements of all of these cations and anions in natural freshwater and seawater were obtained using the ZrO-Chelex DGT. The performance of this technique for simultaneous measurements of 16 elements was also tested in sediments., (Copyright © 2017. Published by Elsevier B.V.)

Diffusive gradients in thin films (DGT) technique has been newly designed for the identification of formation mechanisms of "internal phosphorus (P)-loading" and the numerical simulation of P exchange at DGT/sediment interface in Lake Dianchi. The primary mechanism was Fe-redox controlled P release from Fe-bound P in sediments, which was revealed by C DGT (P and Fe), total P (Fe) and P (Fe) fractions in NH 4 Cl and BD phases in sediments and their relationships at sites (N-T). The breakdown of algae biomass in the top layer of sediments at sites (O-T) and the coupled P/Fe/sulfur reactions at two depths at site N played a minor role in P release. The "internal P-loading" was calculated to be 19.23ta -1 , which was 3.0% of the "entering P-loading". At sites (1-9), DGT induced flux in sediments (DIFS) model for P was used to derive curves (i) the resupply parameter (R) against deployment time and (ii) the dissolved/sorbed concentrations against the distance at DGT/sediment interface, the variation characters of which were controlled by kinetics and sediment-P pool. Sulfide microniches in sediments related to P release were evaluated by computer imaging densitometry (CID). DGT-DIFS-CID should be a reliable method to reveal P mobilization in lake sediments., (Copyright © 2017 Elsevier B.V. All rights reserved.)