Diffusive Gradients in Thin Films Reveals Differences in Antimony and Arsenic Mobility in a Contaminated Wetland Sediment during an Oxic-Anoxic Transition.

Antimony (Sb) and arsenic (As) are priority environmental contaminants that often co-occur at mining-impacted sites. Despite their chemical similarities, Sb mobility in waterlogged sediments is poorly understood in comparison to As, particularly across the sediment-water interface (SWI) where changes can occur at the millimeter scale. Combined diffusive gradients in thin films (DGT) and diffusive equilibration in thin films (DET) techniques provided a high resolution, in situ comparison between Sb, As, and iron (Fe) speciation and mobility across the SWI in contaminated freshwater wetland sediment mesocosms under an oxic-anoxic-oxic transition. The shift to anoxic conditions released Fe(II), As(III), and As(V) from the sediment to the water column, consistent with As release being coupled to the reductive dissolution of iron(III) (hydr)oxides. Conversely, Sb(III) and Sb(V) effluxed to the water column under oxic conditions and fluxed into the sediment under anoxic conditions. Porewater DGT-DET depth profiles showed apparent decoupling between Fe(II) and Sb release, as Sb was primarily mobilized across the SWI under oxic conditions. Solid-phase X-ray absorption spectroscopy (XAS) revealed the presence of an Sb(III)-S phase in the sediment that increased in proportion with depth and the transition from oxic to anoxic conditions. The results of this study showed that Sb mobilization was decoupled from the Fe cycle and was, therefore, more likely linked to sulfur and/or organic carbon (e.g., most likely authigenic antimony sulfide formation or Sb(III) complexation by reduced organic sulfur functional groups).

Removing ammonium from water and wastewater using cost-effective adsorbents: A review.

Ammonium is an important nutrient in primary production; however, high ammonium loads can cause eutrophication of natural waterways, contributing to undesirable changes in water quality and ecosystem structure. While ammonium pollution comes from diffuse agricultural sources, making control difficult, industrial or municipal point sources such as wastewater treatment plants also contribute significantly to overall ammonium pollution. These latter sources can be targeted more readily to control ammonium release into water systems. To assist policy makers and researchers in understanding the diversity of treatment options and the best option for their circumstance, this paper produces a comprehensive review of existing treatment options for ammonium removal with a particular focus on those technologies which offer the highest rates of removal and cost-effectiveness. Ion exchange and adsorption material methods are simple to apply, cost-effective, environmentally friendly technologies which are quite efficient at removing ammonium from treated water. The review presents a list of adsorbents from the literature, their adsorption capacities and other parameters needed for ammonium removal. Further, the preparation of adsorbents with high ammonium removal capacities and new adsorbents is discussed in the context of their relative cost, removal efficiencies, and limitations. Efficient, cost-effective, and environmental friendly adsorbents for the removal of ammonium on a large scale for commercial or water treatment plants are provided. In addition, future perspectives on removing ammonium using adsorbents are presented.

Symbiodinium mitigate the combined effects of hypoxia and acidification on a noncalcifying cnidarian.

Anthropogenic nutrient inputs enhance microbial respiration within many coastal ecosystems, driving concurrent hypoxia and acidification. During photosynthesis, Symbiodinium spp., the microalgal endosymbionts of cnidarians and other marine phyla, produce O2 and assimilate CO2 and thus potentially mitigate the exposure of the host to these stresses. However, such a role for Symbiodinium remains untested for noncalcifying cnidarians. We therefore contrasted the fitness of symbiotic and aposymbiotic polyps of a model host jellyfish (Cassiopea sp.) under reduced O2 (~2.09 mg/L) and pH (~ 7.63) scenarios in a full-factorial experiment. Host fitness was characterized as asexual reproduction and their ability to regulate internal pH and Symbiodinium performance characterized by maximum photochemical efficiency, chla content and cell density. Acidification alone resulted in 58% more asexual reproduction of symbiotic polyps than aposymbiotic polyps (and enhanced Symbiodinium cell density) suggesting Cassiopea sp. fitness was enhanced by CO2 -stimulated Symbiodinium photosynthetic activity. Indeed, greater CO2 drawdown (elevated pH) was observed within host tissues of symbiotic polyps under acidification regardless of O2 conditions. Hypoxia alone produced 22% fewer polyps than ambient conditions regardless of acidification and symbiont status, suggesting Symbiodinium photosynthetic activity did not mitigate its effects. Combined hypoxia and acidification, however, produced similar numbers of symbiotic polyps compared with aposymbiotic kept under ambient conditions, demonstrating that the presence of Symbiodinium was key for mitigating the combined effects of hypoxia and acidification on asexual reproduction. We hypothesize that this mitigation occurred because of reduced photorespiration under elevated CO2 conditions where increased net O2 production ameliorates oxygen debt. We show that Symbiodinium play an important role in facilitating enhanced fitness of Cassiopea sp. polyps, and perhaps also other noncalcifying cnidarian hosts, to the ubiquitous effects of ocean acidification. Importantly we highlight that symbiotic, noncalcifying cnidarians may be particularly advantaged in productive coastal waters that are subject to simultaneous hypoxia and acidification.

"Diffusive Gradients in Thin Films" Techniques Provide Representative Time-Weighted Average Measurements of Inorganic Nutrients in Dynamic Freshwater Systems.

Nutrient concentrations in freshwater are highly variable over time, with changes driven by weather events, anthropogenic sources, modifications to catchment hydrology or habitats, and internal biogeochemical processes. Measuring infrequently collected grab samples is unlikely to adequately represent nutrient concentrations in such dynamic systems. In contrast, in situ passive sampling techniques, such as the "diffusive gradients in thin films" (DGT) technique, provide time-weighted average analyte concentrations over the entire deployment time. A pair of recently developed DGT techniques for nitrate (A520E-DGT) and ammonium (PrCH-DGT), as well as the Metsorb-DGT technique for phosphate, were used to monitor inorganic nutrients in different freshwater systems (i.e., streams and wetlands) with a range of environmental values and that were affected by different catchment types. Measurements of grab samples collected frequently (1-2 times daily, 8-10 a.m. and 2-4 p.m.) showed that concentrations of NH4-N and NO3-N changed dramatically in most of the studied freshwater systems over short time scales, while there were only relatively small fluctuations in PO4-P. The DGT measurements were highly representative in comparison with the average nutrient concentrations obtained from daily grab samples over short-term (24 h) and long-term (72 h) deployments. The ratios of DGT-labile concentrations to the average concentrations from grab samples were between 1.00 and 1.12 over the studied deployment periods. The results of this study confirmed that DGT measurements provided a reliable and robust method for monitoring NH4-N, NO3-N, and PO4-P in a diverse range of dynamic freshwater systems.

Lipid Biomarker and Isotopic Study of Community Distribution and Biomarker Preservation in a Laminated Microbial Mat from Shark Bay, Western Australia.

Modern microbial mats from Shark Bay present some structural similarities with ancient stromatolites; thus, the functionality of microbial communities and processes of diagenetic preservation of modern mats may provide an insight into ancient microbial assemblages and preservation. In this study, the vertical distribution of microbial communities was investigated in a well-laminated smooth mat from Shark Bay. Biolipid and compound-specific isotopic analyses were performed to investigate the distribution of microbial communities in four distinct layers of the mat. Biomarkers indicative of cyanobacteria were more abundant in the uppermost oxic layer. Diatom markers (e.g. C25 HBI alkene, C20:4ω6 and C20:5ω3 polar lipid fatty acids (PLFAs)) were also detected in high abundance in the uppermost layer, but also in the deepest layer under conditions of permanent darkness and anoxia, where they probably used NO3 (-) for respiration. CycC19:0, an abundant PLFA of purple sulfur bacteria (PSB), was detected in all layers and presented the most (13)C-depleted values of all PLFAs, consistent with photoautotrophic PSB. Sulfur-bound aliphatic and aromatic biomarkers were detected in all layers, highlighting the occurrence of early sulfurisation which may be an important mechanism in the sedimentary preservation of functional biolipids in living and, thus, also ancient mats.

Characterizing microbial communities and processes in a modern stromatolite (Shark Bay) using lipid biomarkers and two-dimensional distributions of porewater solutes.

Modern microbial mats are highly complex and dynamic ecosystems. Diffusive equilibration in thin films (DET) and diffusive gradients in thin films (DGT) samplers were deployed in a modern smooth microbial mat from Shark Bay in order to observe, for the first time, two-dimensional distributions of porewater solutes during day and night time. Two-dimensional sulfide and alkalinity distributions revealed a strong spatial heterogeneity and a minor contribution of sulfide to alkalinity. Phosphate distributions were also very heterogeneous, while iron(II) distributions were quite similar during day and night with a few hotspots of mobilization. Lipid biomarkers from the three successive layers of the mat were also analysed in order to characterize the microbial communities regulating analyte distributions. The major hydrocarbon products detected in all layers included n-alkanes and isoprenoids, whilst other important biomarkers included hopanoids. Phospholipid fatty acid profiles revealed a decrease in cyanobacterial markers with depth, whereas sulfate-reducing bacteria markers increased in abundance in accordance with rising sulfide concentrations with depth. Despite the general depth trends in community structure and physiochemical conditions within the mat, two-dimensional solute distributions showed considerable small-scale lateral variability, indicating that the distributions and activities of the microbial communities regulating these solute distributions were equally heterogeneous and complex.

Simultaneous measurement of trace metal and oxyanion concentrations in water using diffusive gradients in thin films with a Chelex-Metsorb mixed binding layer.

A new diffusive gradients in thin films (DGT) technique with a mixed binding layer (Chelex-100 and the titanium dioxide based adsorbent Metsorb) is described for the simultaneous measurement of labile trace metal (Mn, Co, Ni, Cu, Cd, and Pb) and oxyanion (V, As, Mo, Sb, W, and P) concentrations in freshwater and seawater. The mixed binding layer (MBL) DGT technique was evaluated against the Chelex-DGT and Metsorb-DGT techniques, and all elution efficiencies and diffusion coefficients have been remeasured for the above analytes. Diffusion coefficients (D) measured using MBL-DGT generally agreed well with those measured by Chelex-DGT (DMBL/DChelex = 0.97-1.05), Metsorb-DGT (DMBL/DMetsorb = 0.97-1.01), and diffusion cell experiments. The measurement of trace metals and oxyanions by MBL-DGT was independent of pH (5.03-8.05) and ionic strength (I = 0.001-0.7 mol L(-1)). MBL-DGT accurately measured the concentration of trace metals and oxyanions in synthetic freshwater (CMBL/CSol = 0.82-1.18) over the 4 day deployment and also agreed well with Metsorb-DGT (CMBL/CMetsorb = 0.84-0.94) and Chelex-DGT (CMBL/CChelex = 0.88-1.11) measurements. In synthetic seawater, MBL-DGT accurately measured the concentration of metals and oxyanions (CMBL/CSol = 0.85-1.12) over 4 days, with the exception of Mo-none of the DGT techniques were capable of measuring Mo in seawater. MBL-DGT measured the Mn concentration accurately over the entire 4 day period, whereas Chelex-DGT only measured Mn accurately up to 2 days. The MBL-DGT method described in this study offers significant advantages over the ferrihydrite-Chelex-DGT method reported previously. These advantages include the commercial availability of both Metsorb and Chelex-100, the higher accuracy of Metsorb for measuring some oxyanions in freshwater and seawater, and the possibility of measuring Fe, which would not be possible using the Chelex-ferrihydrite binding layer.

Above the law? How motivated moral reasoning shapes evaluations of high performer unethicality.

Recent revelations have brought to light the misconduct of high performers across various fields and occupations who were promoted up the organizational ladder rather than punished for their unethical behavior. Drawing on principles of motivated moral reasoning, we investigate how employee performance biases supervisors' moral judgment of employee unethical behavior and how supervisors' performance-focus shapes how they account for moral judgments in promotion recommendations. We test our model in three studies: a field study of 587 employees and their 124 supervisors at a Fortune 500 telecom company, an experiment with two samples of working adults, and an experiment that directly varied explanatory mechanisms. Evidence revealed a moral double standard such that supervisors rendered less punitive judgment of the unethical acts of higher performing employees. In turn, supervisors' bottom-line mentality (i.e., fixation on achieving results) influenced the degree to which they incorporated their punitive judgments into promotability considerations. By revealing the moral leniency afforded to higher performers and the uneven consequences meted out by supervisors, our results carry implications for behavioral ethics research and for organizations seeking to retain and promote their higher performers while also maintaining ethical standards that are applied fairly across employees. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

DGT measurement of dissolved aluminum species in waters: comparing Chelex-100 and titanium dioxide-based adsorbents.

Aluminum is acutely toxic, and elevated concentrations of dissolved Al can have detrimental effects on both terrestrial and aquatic ecosystems. Robust analytical methods that can determine environmentally relevant Al fractions accurately and efficiently are required by the environmental monitoring community. A simple, robust passive sampling method, the diffusive gradients in thin films (DGT) technique, was evaluated for the measurement of dissolved Al species in freshwater and marine water using either Chelex-100 or Metsorb (a titanium dioxide-based binding agent) as the adsorbent. Mass vs time DGT deployments at pH 5.05 (Al(3+) and Al(OH)(2+) dominate) and 8.35 (Al(OH)(4)(-) dominates) demonstrated linear uptake of Al (R(2) = 0.989 and 0.988, respectively) for Metsorb. Similar deployments of Chelex-DGT showed linear uptake at pH 5.05 (R(2) = 0.994); however, at pH 8.35 the mass of Al accumulated was 40-70% lower than predicted, suggesting that Chelex-100 is not suitable for Al measurements at high pH. The Metsorb-DGT measurement was independent of pH (5.0-8.5) and ionic strength (0.001-0.7 mol L(-1) NaNO(3)), whereas the Chelex-DGT measurement was only independent of ionic strength at pH 5.0. At pH 8.4, increasing ionic strength led to considerable underestimation (up to 67%) of Al concentration. Deployments of Metsorb-DGT (up to 4 days) in synthetic freshwater (pH range 5.4-8.1) and synthetic seawater (pH 8.15) resulted in linear mass uptakes, and the concentration measured by DGT agreed well with solution concentrations. Conversely, deployment of Chelex-DGT in synthetic seawater and freshwater (pH ≥7.7 Al(OH)(4)(-) dominant species) resulted in a decrease in accumulated mass with increasing deployment time. In situ field evaluations in fresh, estuarine, and marine waters confirmed that Metsorb-DGT was more accurate than Chelex-DGT for the measurement of dissolved Al in typical environmental waters.

Investigating arsenic speciation and mobilization in sediments with DGT and DET: a mesocosm evaluation of oxic-anoxic transitions.

Mobilization of arsenic from freshwater and estuarine sediments during the transition from oxic to anoxic conditions was investigated using recently developed diffusive sampling techniques. Arsenic speciation and Fe(II) concentrations were measured at high resolution (1-3 mm) with in situ diffusive gradients in thin films (DGT) and diffusive equilibration in thin films (DET) techniques. Water column anoxia induced Fe(II) and As(III) fluxes from the sediment. A correlation between water column Fe(II) and As(III) concentrations was observed in both freshwater (r(s) = 0.896, p < 0.001) and estuarine (r(s) = 0.557, p < 0.001) mesocosms. Porewater sampling by DGT and DET techniques confirmed that arsenic mobilization was associated with the reductive dissolution of Fe(III) (hydr)oxides in the suboxic zone of the sediment; a relationship that was visible because of the ability to measure the coincident profiles of these species using combined DGT and DET samplers. The selective measurement of As(III) and total inorganic arsenic by separate DGT samplers indicated that As(III) was the primary species mobilized from the solid phase to the porewater. This measurement approach effectively ruled out substantial As(V) mobilization from the freshwater and estuarine sediments in this experiment. This study demonstrates the capabilities of the DGT and DET techniques for investigating arsenic speciation and mobilization over a range of sediment conditions.

From zero to hero and back to zero: The consequences of status inconsistency between the work roles of multiple jobholders.

The surge of opportunities available through the gig economy has increased the sizeable population of people who hold multiple jobs. Many of these multiple jobholders are full-time employees who have adopted side-hustles-income-generating work performed alongside full-time work. A core and ubiquitous feature of both full-time work and side-hustles is status, or membership in a social hierarchy. Although status has traditionally been investigated as an employee's enduring position in the social hierarchy at their full-time job, employees with side-hustles hold two distinct work-related statuses: status in their full-time job and status in their side-hustle. Having two statuses necessarily creates a situation in which employees' status is either consistent or inconsistent across roles. We investigate the implications of status inconsistency between side-hustles and full-time work for employees' stress, well-being, and performance. We assert that status inconsistency between side-hustles and full-time work requires employees to navigate stress-inducing tensions, such as incongruent role expectations and confusion regarding their sense of self. By extension, we propose that status inconsistency between side-hustles and full-time work promotes more role stress than occupying consistently low-status roles. In a four-wave field study of full-time employees with side-hustles, and their supervisors, we use polynomial regression analysis to test our predictions. We find that status inconsistency diminishes performance in full-time work via role stress and emotional exhaustion. Given the burgeoning gig economy and associated changes to how work is organized, our research has important and timely implications for multiple jobholders and their full-time work organizations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Motivated to "roll the dice" on trust: The relationships between employees' daily motives, risk propensity, and trust.

Models of trust have focused on the notion that an employee's trust in a coworker is based on that coworker's trustworthiness and the employee's trust propensity-a generalized tendency to believe others are trustworthy. Although these models capture the general assessment of risk associated with trusting a particular coworker, they provide insufficient insight into why an employee might take the risk associated with trust on a particular day. Bringing the concept of risk propensity-the tendency to accept or avoid risk-from the decision-making literature into the trust literature, we build a model of trust that suggests employees' trusting behaviors stem from both their calculated assessment of risk (encapsulated in trustworthiness and trust propensity) and their tendency to take those risks. We draw on motivated reasoning theory (Kunda, 1990) and the decision-making literature to suggest that employees' daily strivings for achievement, affiliation, stimulation, and security induce a biased reasoning process that influences employees' risk propensity that day. Our test of this theoretical model demonstrates that generalized work motives have an indirect effect on employees' trust in their coworkers, through risk propensity, that goes above and beyond established bases of trust. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Loss of benthic macrofauna functional traits correlates with changes in sediment biogeochemistry along an extreme salinity gradient in the Coorong lagoon, Australia.

Estuarine ecosystems are considered hotspots for productivity, biogeochemical cycling and biodiversity, however, their functions and services are threatened by several anthropogenic pressures. We investigated how abundance and diversity of benthic macrofauna, and their functional traits, correlate to sediment biogeochemistry and nutrient concentrations throughout an estuarine-to-hypersaline lagoon. Benthic communities and functional traits were significantly different across the sites analysed, with higher abundance and more traits expressed in the estuarine region. The results revealed that the benthic trait differences correlated with sediment biogeochemistry and nutrient concentrations in the system. The estuarine regions were dominated by high abundance of large burrowing and bioturbating macrofauna, promoting nutrient cycling and organic matter mineralisation, while these organisms were absent in the hypersaline lagoon, favouring accumulation of organic matter and nutrients in the sediment. The results highlight the importance of preserving healthy benthic communities to maintain ecosystem functioning and mitigate the potential impacts of eutrophication in estuarine ecosystems.

Restoration of benthic macrofauna promotes biogeochemical remediation of hostile sediments; An in situ transplantation experiment in a eutrophic estuarine-hypersaline lagoon system.

Estuarine ecosystems have very high ecological and economic value, and also act as a buffer for coastal oceans by processing nutrient inputs from terrestrial sources. However, ongoing pressures from increased urbanisation and agriculture, overlaid by climate change, has reduced inflows and increased nutrient loads that challenge the health and buffering capacity of these ecosystems. This study aimed to investigate whether restoring the bioturbating activity of Simplisetia aequisetis (Polychaeta: Nereididae) and other macrofauna could improve biogeochemical conditions in 'hostile' (i.e. hypersaline, sulfide-rich) sediments. To achieve this aim, we conducted an in situ experiment in the Coorong estuarine-lagoon ecosystem, translocating hostile hypersaline sediments, devoid of bioturbating macrofauna, to a 'healthy' (lower salinity) location where macrobenthic fauna naturally occur, and manipulating the S. aequisetis density in the sediments. Porewater, solid-phase, and diffusive equilibrium and diffusive gradient in thin-films (DET/DGT) measurements showed that bioturbation by macrobenthic fauna significantly influenced sediment biogeochemistry and remediated hostile conditions in sediment within a short time (four weeks) irrespective of S. aequisetis density. Bioturbation promoted sediment oxygenation, while salinity and the concentrations of total organic carbon and porewater sulfide, ammonium, and phosphate all decreased over time at all sediment depths. This research highlights the importance of macrobenthic communities and their functional traits for improving sediment conditions, promoting resilience to eutrophication, providing a nature-based remediation option, and in general ensuring healthy functioning of estuarine ecosystems.

Baseline water quality of the Gold Coast Broadwater, southern Moreton Bay (Australia).

This study establishes baseline water quality characteristics for the Gold Coast Broadwater, southern Moreton Bay (Australia) utilising routinely monitored parameters between 2016 and 2021, across 18 sites. Combined site mean concentrations of NOx-N, NH3-N and total nitrogen were 11.4 ± 33.4 µg/L, 12.7 ± 27.2 µg/L, and 169 ± 109 µg/L, respectively, whilst PO4-P and total phosphorous were 7.30 ± 5.10 µg/L and 21.7 ± 14.1 µg/L. Additionally, total suspended solids and turbidity combined site means were 6.6 ± 6.0 mg/L and 3.4 ± 2.9 NTU, respectively. During high rainfall periods nutrient concentrations increased by up to >200-, >150-, 15-, 12- and >12-fold for NOx-N, NH3-N, TN, PO4-P and TP, respectively, compared to quiescent conditions. Furthermore, TSS and NTU values increased by up to 15- and 40-fold during periods of measured rainfall compared to quiescent conditions.

Speciation of dissolved inorganic arsenic by diffusive gradients in thin films: selective binding of AsIII by 3-mercaptopropyl-functionalized silica gel.

A diffusive gradients in thin films (DGT) technique for selectively measuring As(III) utilizes commercially available 3-mercaptopropyl-functionalized silica gel. Deployment of the new technique alongside the Metsorb-DGT for total inorganic arsenic allows the calculation of As(III) directly and As(V) by difference. Uptake of As(III) by mercapto-silica was quantitative and elution with a mixture of 1 mol L(-1) HNO(3) and 0.01 mol L(-1) KIO(3) gave a recovery of 85.6 ± 1.7%. DGT validation experiments showed linear accumulation of As(III) over time (R(2) > 0.998). Accumulation was unaffected by varying ionic strength (0.0001-0.75 mol L(-1) NaNO(3)) and pH (3.5-8.5). Deployment of mercapto-silica DGT and Metsorb DGT in seawater spiked with As(III) and As(V) demonstrated the ability of the combined approach to accurately quantify both species in the presence of potential competing ions. Ferrihydrite DGT, which has been previously reported for the measurement of total inorganic arsenic, was evaluated in seawater and shown to underestimate both As(III) and As(V) at longer deployment times (72 h). Reproducibility of the new mercapto-silica DGT technique was good (relative standard deviations < 9%), and the average method detection limit was sufficiently low to allow quantification of ultratrace concentrations of As(III) (0.03 µg L(-1); 72 h deployment).

Assessment of microplastics in discharged treated wastewater and the utility of Chrysaora pentastoma medusae as bioindicators of microplastics.

Microplastics are ubiquitous pollutants in aquatic environments globally. Wastewater treatment plants are considered to be a major source of microplastics and jellyfish have been proposed as potential bioindicators of microplastic pollution. We tested whether treated wastewater influenced the concentration and/or composition of microplastics in the receiving water by comparing the concentration and composition of microplastics in seawater collected in the wastewater plume and at sites distant from treated wastewater releases in the Gold Coast Broadwater, Australia, and at sites within the nearby Tweed River estuaries, which receives >10 times less wastewater discharge. In addition, tiger sea nettle Chrysaora cf. pentostoma medusae were collected to determine whether more microplastics occurred in the guts of the medusae nearby diffusers and whether the microplastics ingested by medusae were representative of those present in the water column. The concentration and composition of microplastics at the wastewater release sites did not significantly differ from sites that were distant from them. Eighty three percent of medusae contained microplastics in their guts and the composition of the ingested microplastics differed significantly from that in the surrounding water. We concluded that discharged treated wastewater had no detectable effect on levels or composition of microplastics in the receiving water and that C. pentostoma are unsuitable bioindicators because the microplastics they ingested did not represent those available in their environment.

Trophic transfer of microbeads to jellyfish and the importance of aging microbeads for microplastic experiments.

Concepts in microplastics studies are not well established due to the emerging nature of microplastic research, especially in jellyfish. We conducted experiments to test whether ephyrae would ingest more microbeads via trophic transfer than direct ingestion and whether medusae would ingest more aged microbeads than virgin microbeads. We exposed ephyrae of Aurelia coerulea to two treatments, aged microbeads and Artemia nauplii that had ingested microbeads. We found that the ephyrae ingested 35 times more microbeads via trophic transfer than by direct ingestion. In the second experiment, medusae of A. coerulea were exposed to virgin microbeads and microbeads in seawater under a 12/12 light/dark cycle or constant darkness. Ingestion rates of microbeads from the light incubation were greater than those from the dark incubation or virgin microbeads, suggesting the likely presence of photosynthetic organisms in biofilms from the light incubation increased the palatability of the microbeads and promoted their ingestion.

Evaluation of the Chelex-DGT technique for the measurement of rare earth elements in the porewater of estuarine and arine sediments.

This study describes the validation of a diffusive gradients in thin film (DGT) technique for determining lanthanide rare earth elements (REEs) and in situ measurements of REEs in sediment pore waters. Laboratory experiments demonstrated that Chelex-100 binding layers had uptake efficiencies ranging from 78.0% to 92.3% for all REEs. An eluent of 1 mol L-1 HNO3 was optimal with elution efficiencies >80% for all REEs. Mass versus time experiments confirmed that DGT uptake was linear for all REEs at pH 8.1, 6.6 and 3.9 over a period of 3-4 days. Diffusion coefficients (D) for all REEs were derived from these experiments using the slopes of the linear regressions. D values varied with pH but were generally similar to values reported previously. The Chelex-100 DGT technique from this study is highly sensitive for the measurement of REE concentrations with detection limits ranging from 1.8 to 45 ng L-1 based on 72 h deployments allowing measurements of natural trace REE levels. Chelex-100 DGT devices were deployed in estuarine and marine sediments over a period of 72 h and most REE porewater concentrations (50-10,410 ng L-1) were successfully measured. Individual depth profiles of REEs showed a complex response, with many peaks and troughs suggesting a high degree of sediment heterogeneity. Depth-averaged REE concentrations showed a typical zig-zag distribution, although patterns varied between sediment types, after the REEs were normalised using the Queensland Mud Composite shale reference. The Chelex-100 DGT technique therefore shows promise for REE measurements in sediments.

New diffusive gradients in a thin film technique for measuring inorganic arsenic and selenium(IV) using a titanium dioxide based adsorbent.

A new diffusive gradients in a thin film (DGT) technique, using a titanium dioxide based adsorbent (Metsorb), has been developed and evaluated for the determination of dissolved inorganic arsenic and selenium. As(III), As(V), and Se(IV) were found to be quantitatively accumulated by the adsorbent (uptake efficiencies of 96.5-100%) and eluted in 1 M NaOH (elution efficiencies of 81.2%, 75.2%, and 88.7%). Se(VI) was not quantitatively accumulated by the adsorbent (<20%). Laboratory DGT validation experiments gave linear mass uptake over time (R(2) >or= 0.998) for As(III), As(V), and Se(IV). Consistent uptake occurred over pH (3.5-8.5) and ionic strength (0.0001-0.75 mol L(-1) NaNO(3)) ranges typical of natural waters, including seawater. Field deployments of DGT probes with various diffusive layer thicknesses confirmed the use of the technique in situ, allowing calculation of the diffusive boundary layers and an accurate measurement of inorganic arsenic. Reproducibility of the technique in field deployments was good (relative standard deviation <8%). Limits of detection (4 day deployments) were 0.01 microg L(-1) for inorganic arsenic and 0.05 microg L(-1) for Se(IV). The results of this study confirmed that DGT with Metsorb was a reliable and robust method for the measurement of inorganic arsenic and the selective measurement of Se(IV) within useful limits of accuracy.