1,721,076 research outputs found
Identifying temporal and spatial variations in the binding properties of transition metal-organic ligand complexes in cave waters using organic inclusions in speleothem calcite: Implications for paleoclimate research.
No full textSpeleothems such as stalagmites, stalactites and flowstones, contain paleoclimate information encoded in their geochemical properties. One of these properties, transition metal abundance in speleothem calcite, is tightly controlled by complexation reactions in cave water with dissolved organic matter (DOM). Organic compounds are also preserved in speleothem deposits. DOM structure varies from cave system to cave system and over time, but whether these structural variations meaningfully alter the way DOM controls trace metal incorporation into calcite is unclear. This is relevant to the development of speleothem transition metal content as a paleoclimate proxy, particularly over large spatial and temporal scales where DOM structure variations are likely. This study identifies variations in the binding properties of DOM preserved in speleothem calcite over time and space by extracting organic compounds of known age and origin from speleothems collected from New Zealand, Niuean, British, and Australian cave systems. The kinetic properties of DOM complexes from these extracts were measured using small volume diffusive gradients in thin films (SV-DGT) and the variation in the binding strength of complexes with Cu, Co, and Ni was compared across time and space. DOM binding of Cu and Co were found to vary significantly depending on the cave system from which the DOM originated. Whether this variation was linked to climate changes represented in the age of the DOM or to changes in system characteristics related to geographical setting was unclear. Despite this, it is apparent that there are factors related to the origin of DOM in cave systems that influence the kinetic restrictions applied to transition metals in cave water. This variability should be considered when linking trace element contents in cave precipitates to paleoclimate change
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
In situ measurement of metal-ligand complex dissociation rates in cave dripwaters
Get PDFThe purpose of this study was to develop a new method for determining the trace metal binding properties of natural organic matter (NOM) in cave dripwaters. The methodology is based on the diffusive gradients in the thin-films (DGT) technique, but differs from DGT by using advective gradients along hydrogel to resolve temporal trends in dissociation. For this reason, it is referred to as advective gradients in thin-films (AGT).
NOM is a ubiquitous component in natural waters. The complexation capacities of NOM ligands for metal ions in cave waters has a great impact on the transport of trace metals to, and their incorporation in, calcium carbonate cave deposits (speleothems). The relationship between the kinetics of metal-NOM complexes and the concentration of the metal-carbonate solid solution in actively forming cave precipitates, is the major focus in this study. The primary goal of this research is the determination of the mean kinetics of compositionally-unknown metal-NOM complexes in situ with the application of AGT.
The first part of this study was to calibrate the self-assembled AGT device containing a resin gel (for the binding of metal ions). A range of drip rates was tested to establish the relationship between drip rates and flow velocity within the gel with the aim of establishing a calibration function between drip discharge and flow rate within the gel. The second part of this study was to validate the method using metal-ligand complexes of known character. Synthetic solutions containing organic ligands at known concentrations were measured. The experimental data showed acceptable reproducibility, and the modelling results agreed well with the literature.
After the laboratory-based study of the AGT method, the device was deployed in Aranui Cave, which is a natural cave located in the Waitomo District, New Zealand. Four transition metals were found in both resin gel samples and the water sample. The accumulation behaviour of the metals in the Chelex-100 resin gel demonstrated the capability of the AGT method to measure trace metals bound to unknown NOM ligands in cave dripwaters. The dynamics of the dissociation of metal-NOM complexes can be reflected by the distinct dissociation patterns of the metals.
This newly developed method can semi-qualitatively determine the dissociation rates of labile and partially labile metal-NOM complexes in natural waters. However, further optimisation of the method will be required to improve the precision and accuracy of measurements. In summary, this study provides the basic framework for further research of a new palaeoclimate proxy utilising trace meta-content in speleothems
The terrestrial carbon cycle in transition: tracking changes using novel tracers on multiple timescales
Get PDFSoils store more carbon than the atmosphere and terrestrial vegetation combined, therefore, changes in soil carbon storage can affect the global carbon budget. One of the forms in which carbon is exported from soil is as dissolved organic carbon (DOC). Upon release from soil, components of DOC can be oxidised to CO₂, thus potentially contributing to the global climate crisis. In freshwater systems, DOC is considered a pollutant because of its detrimental impact on freshwater ecology and biodiversity (by blocking light and reducing photosynthesis and altering thermal-mixing regimes in lakes), increasing freshwater acidity, transporting nutrients (particularly N and P) and trace metal pollutants. Further, during the water treatment process (for human consumption), DOC can form toxic by-products.
This project aimed to shed new light on terrestrial carbon dynamics by testing the hypothesis that climate can drive increases in soil DOC export. This research focused on past soil DOC exports in New Zealand, an archipelago located in the mid-latitudes of the Southern Hemisphere. New Zealand’s palaeo-environmental archives (e.g. speleothems and lake sediments) provide a unique opportunity to reconstruct the concentrations and characteristics of DOC under changing climate conditions over centennial/millennial timescales. New Zealand was uninhabited by humans until the 13th century. Palaeo-environmental records that extend beyond the 13th century, therefore, exclude interference from anthropogenic factors, thus enabling the climate hypothesis to be assessed.
Using lake sediment archives to reconstruct DOC concentrations and characteristics through the past 14,000 years
This study explored the use of 3D EEM (excitation-emission matrix spectroscopy) fluorescence of water extractable dissolved organic matter (WEDOM) from lake sediments in reconstructing both past soil export of DOM and past trophic status. DOM and water quality are linked because DOM can contain nutrients (N, and P), provide an energy source to heterotrophs and algae, can reduce light penetration, and lead to reduced dissolved oxygen concentrations.
Mean trophic level index (TLI) monitoring data of the lake water columns were compared against protein-like fluorescence from contemporary sedimentary WEDOM from ten lakes, producing strong positive correlations with total phosphorous (R²= 0.81), and TLI scores (R²= 0.74 ), and weak positive correlations with total nitrogen (R²= 0.5) and chlorophyll a (R²= 0.44). The equation produced from the correlation between TLI scores and protein-like fluorescence of WEDOM was used to reconstruct TLI scores through the past 13,700 years at Adelaide Tarn (a climatically sensitive, sub-alpine lake located in the north west of the South Island), indicating predominantly oligotrophic conditions throughout the record.
Humic-like DOM fluxes in Adelaide Tarn responded to known climate shifts over the course of the Holocene, indicating a climatic control on soil DOM production and/or export. The results indicate that WEDOM fluorescence can be used as a reliable indicator of past soil export of DOM as well as past trophic status.
To examine total organic carbon concentration; a partial-least square regression (PLSR) model was produced using Fourier transform infrared spectroscopy (FTIRS) data vs conventionally measured TOC of 141 sediment samples from 13 lakes, resulting in strong positive correlation (R² =0.88). The equation from this correlation was then used to reconstruct past TOC concentrations from sediments in Adelaide Tarn. The FTIRS-TOC and humic-like DOM records showed a clear relationship with known temperature changes over the past ~14,000 years BP.
Testing the reliability of calcite to record DOC concentrations from its parent solution
Natural carbonates (such as speleothems) are known to contain DOM. Speleothems accumulate for hundreds of thousands of years, thus potentially containing long-term records of DOM export from their overlying soil. However, the ability of carbonates to reliably record DOM concentrations from their parent solutions is unknown. A calcite precipitation experiment was undertaken in growth solutions (diluted peat water) of differing [DOC]aq (0, 5, 10, 15 ppm) with the aim of testing the reliability of calcite to record [DOC]aq, and the potential of 3D excitation emission (EEM) analysis to assess the DOC concentration in dissolved calcite samples. A case study of flowstones and dripwaters from three New Zealand caves was also conducted. In the case study, 3D EEM fluorescence-inferred DOC concentrations were measured in the dripwaters and speleothems, thus enabling calculation of DOC partition coefficients between dripwaters and their associated flowstones. Overall, the study demonstrated that calcite [DOC] is controlled by aqueous [DOC] from the parent solution, in natural and experimental environments.
Further, [DOC]aq within the experimental range did not alter the calcium carbonate polymorph (calcite), yet heavily influenced calcite crystal structure; smooth-faced, rhombohedral crystals formed in growth solutions with low [DOC]aq (0–5 ppm), whereas prismatic, ‘impure’ crystals were produced at high [DOC]aq (10 and 15 ppm).
Using speleothem archives to test the impact of climate on aquatic DOC concentrations in a pre-human continent
3D EEM fluorescence was used to measure humic-like DOC concentrations in modern dripwaters and within three flowstones (secondary carbonate deposits) from three caves distributed along a 7° latitudinal gradient. Calculated DOC concentrations from recently deposited flowstone calcite and dripwater monitoring were used to calculate empirical distribution coefficient (Kd) values, enabling an estimate of dripwater DOC concentrations through the past ~14,000 years BP.
Correspondence between heightened aquatic DOC concentrations during periods of known temperature increases (especially the Holocene climatic optimum) was observed at Hodges Creek (north-west South Island) and Dave’s Cave (south-west South Island), whilst climatic cooling (during the mid-Holocene) yielded lower DOC values. This occurrence was not clear at Waipuna Cave (western North Island), perhaps owing to its relatively low altitude and lack of climatic sensitivity compared to the other sites.
Ratios of Mg to Ca in the flowstone showed a strong correspondence between periods of drier climate and increases in DOC dripwater concentration at each site. The findings of this study show that DOC concentrations have been higher in the past at the high-altitude sites, and that climate (in the absence of anthropogenic impacts) plays a pivotal role in soil DOC export in sub-alpine and alpine environments.
Summary
The thesis produced several outcomes. Chapter 3 demonstrated that protein-like fluorescence of sedimentary WEDOM is associated with trophic level index score and can be used as an indicator of past trophic level (i.e. productivity). Further, the Adelaide Tarn palaeo-environmental reconstruction demonstrated that humic-like fluorescence responded to climate shifts through the Holocene, indicating a temperature control on soil C production and/or export. At large, the DOC concentration over the ~10 kyr period approximately halved with a decrease in temperature of 1.2 °C.
The project also demonstrated (in Chapter 4) that speleothems can reliably record DOC from their parent solutions, showing a linear response between dissolved and solid phase organic concentration. This finding formed the foundation of Chapter 5, which demonstrated that high humic-like DOC concentrations in flowstones were associated with drier conditions at Waipuna Cave (lower-altitude North Island site), however there was no clear correspondence between temperature and [DOC] in the Waipuna record.
At the high altitude, South Island sites (Hodges Creek cave, Adelaide Tarn and Dave’s Cave), DOC concentrations were higher during periods with relatively low precipitation and high temperature. Hodges Creek Cave (940 m a.s.l.) is situated at a similar altitude to Adelaide Tarn (1,250 m a.s.l.) the two sites being only 32 km apart. Adelaide Tarn’s WEDOM and FTIR-TOC records show strikingly similar patterns of humic-like fluorescence and TOC concentrations to the Hodge’s Creek fluorescence record, providing support for a regionally coherent signal. The relationship between climate and soil DOC export was most clear during the Holocene climatic optimum. At this time, temperatures were approximately 1.5-2.5 °C warmer than present, whilst humic-like DOC values (relative to modern) were 57 % higher at Hodge’s Creek, 36 % higher at Adelaide Tarn and 40 % higher at Dave’s Cave. The HCO was also drier than most of the Holocene at these sites. Following the HCO, temperature declined, and wetness increased, corresponding with a notable decline in DOC concentrations at these sites.
These findings imply that in the absence of human interference, higher temperatures and aridity were important drivers of elevated soil DOC export through the past 14,000 years BP was controlled by temperature and wetness at the high-altitude sites, whilst only wetness was important at low altitude
Effects of organic matter complexation on partitioning of first-row transition metals into calcite: cave-analogue crystal growth studies
Get PDFSpeleothems are important archives of terrestrial paleoclimate due to their wide geographical coverage and the ability to date their growth layers using U-Th and U-Pb radiometric dating. Extensive research into various speleothem-based geochemical proxies has been undertaken in the last half century, and a significant number of proxies are now used routinely for reconstructions of paleoclimate including stable oxygen and carbon isotopes (known to respond to variations in rainfall and temperature), fluorescence (indicative of the quality and quantity of organic matter present in cave dripwaters) and speleothem minerology (e.g. fabric defects and nano-crystal aggregation). Trace element proxies in speleothems have also garnered attention, but the suite of trace elements used to date has primarily been limited to the alkali earth metals as they exhibit simple partitioning and are characterised by partition coefficients (Kd values) less than 1. Their role in karst systems is thus comparatively well constrained.
In contrast, the first-row transition metals have been the focus of only a few speleothem-based studies, despite recent evidence suggesting some of these metals (namely Co, Ni and Cu) may be useful additions to the current suite of trace element proxies already utilised. Thus, although theoretical distribution coefficient data are available for these metals, their partitioning behaviour into speleothem calcite is not well understood. Theoretical distribution coefficients are useful in understanding partitioning behaviour under certain conditions, but the non-thermodynamic nature of partition coefficients during calcite precipitation in most natural contexts requires partitioning behaviour under speleothem-specific conditions to be established. For instance, despite theoretical distribution coefficients being greater than 1 for Co, Ni and Cu, apparent partition coefficients (Kd app) calculated for these metals in actual speleothem samples are frequently less than 1 due to the dependence of Kd app on a number of factors including calcite precipitation rate, crystal morphology, and complexation reactions between natural organic matter (NOM) and trace ions. Indeed, complexation of first-row transition metals in speleothem-forming dripwaters has been shown to significantly alter the availability of these metals for incorporation into speleothem calcite. This study therefore aimed to investigate the partitioning behaviour of Co, Ni and Cu into calcite precipitated under karst-analogue conditions and in the presence of organic ligands to help establish these metals as viable speleothem-based paleoclimate proxies.
In order to do this, a suitable method for growing calcite under karst-analogue conditions was first established. All experiments were undertaken inside a purpose-built chamber that ensured precise control of temperature, humidity and pCO2, and calcite was grown in a manner analogous to that observed for natural speleothems, with calcite precipitation occurring as a result of CO2 degassing from a thin solution film. Observed growth rates and structural characterisation of the precipitated CaCO3 indicated the method developed was suitable for the desired purpose, and the partitioning data obtained subsequently was considered to be applicable to ‘real-world’ speleothem and cave dripwater samples.
The partitioning behaviour of Co, Ni and Cu into calcite grown under speleothem-like conditions was assessed, and speleothem-specific Kd values of ~ 4, 1 and 44, respectively, were determined. The relatively high inorganic Kd values determined for Co and Cu illustrate the reason why these divalent metals have frequently been overlooked as paleoclimate proxies in speleothems: metals with high partition coefficients are thought to exhibit complex partitioning behaviour and are significantly affected by PCP. However, further experiments carried out with organic ligands present in solution illustrated that the complexation of Co, Ni and Cu by nitrilotriacetic acid (NTA) and Suwanee River fulvic acid (SRFA) significantly altered their partitioning behaviour, with apparent partition coefficients reduced below 1 for all three metals. It was shown that partitioning of Co, Ni and Cu into calcite was controlled not only by their affinity for the calcite lattice (i.e. inorganic Kd values) but also by the dissociation of the metal-ligand complexes, and that the amount of ‘free’ metal available for incorporation into calcite was dependent on residence time and the dissociation constants of the complexes.
The results found in this study highlight the fact that the incorporation of the divalent first-row transition metals into speleothem calcite cannot be considered in terms of simple inorganic partitioning, as the widespread presence of NOM in karst systems will alter their partitioning behaviour significantly. Thus, although the use of these metals as speleothem-based proxies has previously been overlooked in favour of elements such as the alkali earth metals which exhibit simple partitioning (i.e. Kd << 1), in reality the NOM present in karst systems will reduce the effects of PCP on these divalent first-row metals, and they should in fact be considered as useful additions to the current range of paleo-proxies used
Biogeochemistry of denitrifying bioreactors to enhance phosphorus removal from agricultural subsurface drainage
No full textDegradation of water quality due to nutrient over-enrichment has become a global environmental concern. In Aotearoa, agricultural pollution of freshwaters by nutrients is increasing. Therefore, strategies need to be implemented to minimize nutrient pollution in surface waters. Denitrifying bioreactors (DBRs) are a prominent edge-of-field treatment technology to mitigate surface water nitrate loadings from agricultural subsurface drainage. Recent studies have identified that subsurface drainage can also contribute to the loss of phosphorus from agricultural soil. Therefore, this thesis investigates the potential of DBRs to incorporate iron-based materials to sequester phosphorus and reduce pollution of waterways.
There is some evidence suggesting low-level phosphorus removal by woodchip bioreactors alone. However, it is inevitable that woodchips alone do not abiotically remove phosphorus due to the incompatibility between the surface charge of wood at neutral-to-acidic pH values. In this study, raw pinus radiata, and, thermally modified pyrolyzed woodchips were employed for surface modification, with view to enhancing P binding in DBRs.
We were mindful in the design of material functionalization to avoid complicated preparation steps, exotic or harmful reagents, and impractical particle sizes to ensure compatibility for large-scale applications in the agricultural landscape. Results indicated that the functionalization of wood media successfully inversed the surface charge, leading to a net positive charge within the favorable range for phosphorus adsorption under reactor-specific conditions (pH 5.5 − 6). The maximum adsorption capacity of functionalized wood and functionalized biochar corresponded to 65.8 mg g-1 and 31.4 mg g-1, respectively, comparing well to values reported in the literature.
DBRs operate under varying hydraulic conditions, which results in variable flow rates, nutrient concentrations, redox status, pH, and many other variables that affect the operation of the bioreactor. The stability of iron hydr(oxide) composites is expected to be sensitive to some of these conditions, especially acidic and anaerobic conditions, which favor dissolution of iron hydr(oxide)s and therefore could adversely affect P removal. Furthermore, there are other likely products of reduced Fe2+ and orthophosphate (HPO42-) that could form under the conditions anticipated. Therefore, the biogeochemical environment in the DBR was characterized to understand the stability of iron hydr(oxide)s and their ability to subsequently remove of phosphorus.
To date, there have been only limited investigations into the stability of iron hydr(oxide)s under real-world bioreactor conditions, and functionalisation studies often neglect the impact of oscillating redox conditions on the stability of Fe-based adsorbents. In light of this, bench-scale woodchip bioreactors were established, both with and without MnO2, to evaluate the redox buffering capacity of MnO2 with view to mitigating the reductive dissolution of iron oxide. This approach aimed to improve the retention of dissolved reactive phosphorus (DRP) on the introduced iron oxide surfaces. It was concluded that iron oxides effectively remove DRP and MnO2 enhances nitrogen (N) removal, with slightly better performance observed in the treatment incorporating Fe oxides and MnO2. Hence, it can be inferred that the addition of manganese and iron oxides proves advantageous as an amendment to the conventional woodchip substrate in DBRs to enhance nutrient removal.
This thesis has demonstrated that Fe-functionalized media can effectively remove DRP in agricultural drainage water. In addition, by incorporating MnO2, Fe oxides can be stabilised under oscillating redox conditions, and therefore the combination of MnO2 and Fe oxides could serve as a practical solution for DBRs to mitigate diffuse pollution in New Zealand. These findings offer insights for redesigning DBRs, providing a clearer understanding of the dynamics of P removal in DBRs, and how functionalized media can be employed in the long term to remove phosphorus from agricultural drainage water, meeting water quality objectives while minimizing P releases
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Passive in-situ estrogenic potency sampling with DGT-YES
Get PDFThe purpose of this research was to investigate the presence of bisphenolic plastics and synthetic estrogens in municipal water systems, as well as along the Waikato River. The concentration of these compounds was assessed using a novel combination of methods that allowed the actual levels of endocrine disruption to be ascertained. This was based on diffusive gradients in thin films (DGTs) coupled with high-performance liquid chromatography/mass spectrometry analysis (HPLC/MS) and the Yeast Estrogen Screen (YES).
DGT estimated time-integrated concentrations while HPLC/MS ensured a robust, automated and sensitive routine analysis. Most significantly, YES, a biomarker-based assay, was deployed to quantify the total estrogenic potency of the compounds adsorbed to the DGT matrix. The unique dimension of this research was to extend the application of DGTs to estrogen sampling and to combine the DGT and YES technique to provide in situ quantification of the estrogenic potency of water bodies through time.
DGTs were developed specifically for the sampling of BPA, BPAF, E2 and EE2. Several physical-chemical and chemical analyses were conducted to attest the suitability of the agarose (1.5%) and agarose (1.5%) – activated charcoal (1%) chosen respectively as diffusive gel and binding gel. They were found to be suitable for the detection of organic molecules with a bigger steric hindrance and agarose (1.5%) – AC (1%) appeared suitable for long deployments thanks to its high thermal resistance. An HPLC-MS method was optimised to quantify the compounds of interest. A methanol (MeOH, NH4OH 0.06 M)/water (H2O, NH4OH 0.06 M) fast gradient elution program of 15 min was chosen to elute the analytes, MS parameters were optimized for each compound and the negative mode was selected to perform the fragmentation. LODs and LOQs of all targets resulted in the nanomolar range assuming 24 h as deployment time at 25°C with a 0.54 mm thick diffusive gel. The sensitivity of the method was increased in the sub-nanomolar range by adopting long deployment times (18 days) thus enhancing the accumulation of the targets.The YES was successfully developed to quantify the total estrogenic potency of the DGTs eluted. The dose-response calibration curve of E2, employed as a control, demonstrated LOD and experimental EC50 values in the sub-nanomolar range. EE2, BPA and BPAF demonstrated agonistic endocrine activity, in particular EE2 being more potent than E2, while BPAF and BPA were less potent.
The environmental monitoring assessed the efficiency of removal of the selected ECs during the water treatment processes from river-to-tap and effluent-to-treated wastewater in Hamilton as well the water quality from source-to-outfall of the Waikato River. The HPLC-MS and YES results highlighted that primary treatments were not suitable for the removal of bisphenolic plastics and estrogens both at drinkable and wastewater treatment plants in Hamilton where they appear to worsen the water quality making these pollutants more available. At both treatment plants, the concentration and the estrogenic activity of the targets appeared to fluctuate around the same value, pointing out the inefficiency of removal of these compounds with the actual treatments. EE2 contributed the most to the estrogenic activity due to its higher concentration and higher potency at all sites.
The concentration and the estrogenic potency of all targets were found to be higher downstream at all sites monitored along the Waikato River. EE2 was the compound with the highest concentration at all sites. A moderate worsening of water quality was apparent moving from Taupo to Tuakau. The most polluted sites were Hamilton and Huntley after the outlets of wastewater treatment plants that serve the main conurbations in the area. The EDC concentrations recorded in November 2017 and February 2018 during the monitoring of the Waikato River at Hamilton upstream and downstream sites showed a significant dilution due to the weather conditions.
The data from a previous monitoring of the Waikato River adopting an SPE-HRGC/MS method were compared with those of the DGT-HPLC/MS investigation. The water quality appeared slightly worsened at all sites from 2013 to 2018 due to increased concentrations of BPA and EE2. The DGT-HPLC/MS quantification with the YES assay proved that not only active samplings but passive samplings as well can be coupled with a bioassay. This combined approach had the excellent potential to provide a reliable total estrogenic potency evaluation with time integrated concentrations. The use of the assay allowed estimation of the total estrogenic potency of the eluted DGT. The eluate appeared enriched by other compounds with estrogenic activity, suggesting this type of DGT could be suitable for the sampling and accumulation of other analytes that could be further investigated via HPLC/MS analysis. Compared to the traditional active approaches, DGT ensured sampling and concentration in one step, was easy to prepare and to use, required a very simple sample preparation step prior to analysis, and provided sensitivity in the sub-nanomolar range comparable to active sampling analyses. The YES assay was responsive, robust and easy to use compared to other assays that require laborious procedures and longer times for estrogenic potency evaluation and high sensitivity in the sub-nanomolar range comparable to other assays
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