Hyporheic exchange in recirculating flumes under heterogeneous bacterial and morphological conditions

Betterle, A; Jaeger, A; Posselt, M; Coll, C; Benskin, JP; Schirmer, M
2021 | Environ. Earth Sci. | 80 (6)
biodegradation , hyporheic exchange , hyporheic zone , modelling , pollutants , surface water porewater interaction
Hyporheic exchange (HE) contributes to the biogeochemical turnover of macro- and micro-pollutants in rivers. However, the spatiotemporal complexity and variability of HE hinder understanding of its role in the overall functioning of riverine ecosystems. The present study focuses on investigating the role of bacterial diversity and sediment morphology on HE using a multi-flume experiment. A fully coupled surface-subsurface numerical model was used to highlight complex exchange patterns between surface water and the underlying flow field in the sediments. Under the experimental conditions, the surface water flow induced by bedforms has a prominent effect on both local trajectories and residence time distributions of hyporheic flow paths, whereas mean hyporheic retention times are mainly modulated by average surface flowrates. In case of complex bedform morphologies, the numerical model successfully reproduces the HE estimated by means of salt dilution tests. However, the 2D numerical representation of the system falls short in predicting HE in absence of bedforms, highlighting the intrinsic complexity of water circulation patterns in real scenarios. Finally, results show that higher bacterial diversities in the stream sediments can significantly reduce hyporheic fluxes. This work provides a framework to interpret micropollutants turnover in light of the underlying physical transport processes in the hyporheic zone. The study emphasizes the importance of better understanding the tradeoff between physically driven transport processes and bacterial dynamics in the hyporheic zone to quantify the fate of pollutants in streams and rivers.

Inconsistencies in How Environmental Risk Is Evaluated in Sweden for Dumping Dredged Sediment at Sea

Bruce, P; Bradshaw, C; Ohlsson, Y; Sobek, A; Christiernsson, A
2021 | Front. Mar. Sci. | 8
aromatic-hydrocarbons , bioavailability , contaminant , contaminated sediments , ecosystem , fish , impact , regulation , resuspension , risk assessment , risk evaluation , risk management , sea dumping , sediment , site , toxicity , water
Millions of tons of dredged sediment are dumped at sea annually. International conventions limit dumping when there is a risk of adverse ecological effects, for example if the sediment is contaminated. However, the perception of risk differs substantially among stakeholders and in Sweden there is a lack of guidelines for how to address such risk. In the current study, we examined exemptions to the Swedish ban on dumping at sea, to explore the extent of dumping and how ecological aspects were considered in the evaluation of risks. We analyzed data from all cases granted exemption by county administrative boards and all court cases considering exemption to the ban from the beginning of 2015 to June 2020. We found that while dumping is the least common alternative management method for dredged sediment in total number of cases (98/792), dumping is the main method in terms of volume (30.8/38.2 million m(3)). When considering exemptions, the courts mainly evaluated the risk of exposure to contaminants and resuspended sediment for the environment adjacent to the dumpsite. The risks from contaminants were characterized based on various lines of reasoning, mainly relying on reference values not based on a scientific correlation to environmental risk. We argue that the evaluations were not in line with current regulations and international conventions as they insufficiently accounted for the ecotoxicological risk of the dumped sediment. These issues are potentially similar in other Baltic Sea countries, where there is a similar dependency on binary chemical limit values.

When science and politics come together: From depletion to recovery of the stratospheric ozone hole This article belongs to Ambio’s 50th Anniversary Collection. Theme: Ozone Layer

2021 | Ambio | 50 (1) (31-34)

Adult female European perch (Perca fluviatilis) from the Baltic Sea show no evidence of thiamine deficiency

Gustafsson, J; Strom, K; Arvstrand, L; Forlin, L; Asplund, L; Balk, L
2021 | J. Sea Res. | 174
apoenzyme , fish , fluviatilis , health , polybrominated diphenyl ethers , seasonal variation , transketolase , vitamin b-1
Deficiency of thiamine (vitamin B1) has been demonstrated in several species in the northern hemisphere and is suggested as a cause for declining populations. European perch from the Baltic Sea show negative temporal trends for several health biomarkers and poor recruitment of unknown cause. In this study, thiamine status of perch liver from the Baltic Sea was studied with emphasis on seasonal variation. During spring the thiamine concentration increased, reached a higher level during the summer and then decreased again during autumn. Despite this variation the thiamine concentration was always sufficient in the perch liver. These results indicate that direct thiamine deficiency is an unlikely explanation for the health effects observed in adult female perch from the Baltic Sea.

Risk-based prioritization of suspects detected in riverine water using complementary chromatographic techniques

Been, F; Kruve, A; Vughs, D; Meekel, N; Reus, A; Zwartsen, A; Wessel, A; Fischer, A; Ter Laak, T; Brunner, AM
2021 | Water Res. | 204
chemical water quality , chemicals , chromatography , data science , drinking water , hrms , ionization efficiency , non-target screening , organic micropollutants , surface water
Surface waters are widely used as drinking water sources and hence their quality needs to be continuously monitored. However, current routine monitoring programs are not comprehensive as they generally cover only a limited number of known pollutants and emerging contaminants. This study presents a risk-based approach combining suspect and non-target screening (NTS) to help extend the coverage of current monitoring schemes. In particular, the coverage of NTS was widened by combining three complementary separations modes: Reverse phase (RP), Hydrophilic interaction liquid chromatography (HILIC) and Mixed-mode chromatography (MMC). Suspect lists used were compiled from databases of relevant substances of very high concern (e.g., SVHCs) and the concentration of detected suspects was evaluated based on ionization efficiency prediction. Results show that suspect candidates can be prioritized based on their potential risk (i.e., hazard and exposure) by combining ionization efficiency-based concentration estimation, in vitro toxicity data or, if not available, structural alerts and QSAR.based toxicity predictions. The acquired information shows that NTS analyses have the potential to complement target analyses, allowing to update and adapt current monitoring programs, ultimately leading to improved monitoring of drinking water sources.

A review of how we assess denitrification in oyster habitats and proposed guidelines for future studies

Ray, NE; Hancock, B; Brush, MJ; Colden, A; Cornwell, J; Labrie, MS; Maguire, TJ; Maxwell, T; Rogers, D; Stevick, RJ; Unruh, A; Kellogg, ML; Smyth, AR; Fulweiler, RW
2021 | Limnol. Oceanogr. Meth. | 19 (10) (714-731)
carrying-capacity , chesapeake bay , crassostrea-virginica , eastern oysters , marine sediment , measuring sediment-denitrification , nitrate reduction , nitrogen dynamics , reef restoration , shellfish aquaculture
Excess nitrogen (N) loading and resulting eutrophication plague coastal ecosystems globally. Much work is being done to remove N before it enters coastal receiving waters, yet these efforts are not enough. Novel techniques to remove N from within the coastal ecosystem are now being explored. One of these techniques involves using oysters and their habitats to remove N via denitrification. There is substantial interest in incorporating oyster-mediated enhancement of benthic denitrification into N management plans and trading schemes. Measuring denitrification, however, is expensive and time consuming. For large-scale adoption of oyster-mediated denitrification into nutrient management plans, we need an accurate model that can be applied across ecosystems. Despite significant effort to measure and report rates of denitrification in oyster habitats, we are unable to create such a model, due to methodological differences between studies, incomplete data reporting, and inconsistent measurements of environmental variables that may be used to predict denitrification. To make a model that can predict denitrification in oyster habitats a reality, a common sampling and reporting scheme is needed across studies. Here, we provide relevant background on how oysters may stimulate denitrification, and the importance of oyster-mediated denitrification in remediating excess N loading to coastal systems. We then summarize methods commonly used to measure denitrification in oyster habitats, discuss the importance of various environmental variables that may be useful for predicting denitrification, and present a set of guidelines for measuring denitrification in oyster habitats, allowing development of models to support incorporation of oyster-mediated denitrification into future policy decisions.

Novel 4-Hydroxybenzyl Adducts in Human Hemoglobin: Structures and Mechanisms of Formation

Rajczewski, AT; Ndreu, L; Pujari, SS; Griffin, TJ; Tornqvist, MA; Karlsson, I; Tretyakova, NY
2021 | Chem. Res. Toxicol. | 34 (7) (1769-1781)
cysteine residues , dna adducts , identification , liver , n-terminal valine , p-cresol , protein cross-linking , quinone methide , serum-albumin , strategy
Humans are exposed to large numbers of electrophiles from their diet, the environment, and endogenous physiological processes. Adducts formed at the N-terminal valine of hemoglobin are often used as biomarkers of human exposure to electrophilic compounds. We previously reported the formation of hemoglobin N-terminal valine adducts (added mass, 106.042 Da) in the blood of human smokers and nonsmokers and identified their structure as 4-hydroxybenzyl-Val. In the present work, mass spectrometry-based proteomics was utilized to identify additional sites for 4-hydroxybenzyl adduct formation at internal nucleophilic amino acid side chains within hemoglobin. Hemoglobin isolated from human blood was treated with para-quinone methide (para-QM) followed by global nanoLC-MS/MS and targeted nanoLC-MS/MS to identify amino acid residues containing the 4-hydroxybenzyl modification. Our experiments revealed the formation of 4-hydroxybenzyl adducts at the alpha His20, alpha Tyr24, alpha Tyr42, alpha His45, beta Ser72, beta Thr84, beta Thr87, beta Ser89, beta His92, beta Cys93, beta Cys112, beta Thr123, and beta His143 residues (in addition to N-terminal valine) through characteristic MS/MS spectra. These amino acid side chains had variable reactivity toward para-QM with alpha His45, alpha Tyr42, beta Cys93, beta His92, and beta Ser72 forming the largest numbers of adducts upon exposure to para-QM. Two additional mechanisms for formation of 4-hydroxybenzyl adducts in humans were investigated: exposure to 4-hydroxybenzaldehyde (4-HBA) followed by reduction and UV-mediated reactions of hemoglobin with tyrosine. Exposure of hemoglobin to a 5-fold molar excess of 4-HBA followed by reduction with sodium cyanoborohydride produced 4-hydroxybenzyl adducts at several amino acid side chains of which alpha His20, alpha Tyr24, alpha Tyr42, alpha His45, beta Ser44, beta Thr84, and beta His92 were verified in targeted mass spectrometry experiments. Similarly, exposure of human blood to ultraviolet radiation produced 4-hydroxybenzyl adducts at alpha His20, alpha Tyr24, alpha Tyr42, alpha His45, beta Ser44, beta Thr84, and beta Ser89. Overall, our results reveal that 4-hydroxybenzyl adducts form at multiple nucleophilic sites of hemoglobin and that para-QM is the most likely source of these adducts in humans.

Finding essentiality feasible: common questions and misinterpretations concerning the “essential-use” concept

Cousins, IT; De Witt, JC; Gluge, J; Goldenman, G; Herzke, D; Lohmann, R; Miller, M; Ng, CA; Patton, S; Scheringer, M; Trier, X; Wang, ZY
2021 | Environ. Sci.-Process Impacts | 23 (8) (1079-1087)
alternatives , chemicals
The essential-use concept is a tool that can guide the phase-out of per- and polyfluoroalkyl substances (PFAS) and potentially other substances of concern. This concept is a novel approach to chemicals management that determines whether using substances of concern, such as PFAS, is truly essential for a given functionality. To assess the essentiality of a particular use case, three considerations need to be addressed: (1) the function (chemical, end use and service) that the chemical provides in the use case, (2) whether the function is necessary for health and safety and critical for the functioning of society and (3) if the function is necessary, whether there are viable alternatives for the chemical for this particular use. A few illustrative examples of the three-step process are provided for use cases of PFAS. The essential-use concept takes chemicals management away from a substance-by-substance approach to a group approach. For PFAS and other substances of concern, it offers a more rapid pathway toward effective management or phase-out. Parts of the concept of essential use have already been widely applied in global treaties and international regulations and it has also been recently used by product manufacturers and retailers to phase out substances of concern from supply chains. Herein some of the common questions and misinterpretations regarding the practical application of the essential-use concept are reviewed, and answers and further clarifications are provided.

Bioaccumulation of Per- and polyfluoroalkyl substances (PFASs) in a tropical estuarine food web

Miranda, DA; Benskin, JP; Awad, R; Lepoint, G; Leonel, J; Hatje, V
2021 | Sci. Total Environ. | 754
biomagnification , brazil , os-santos bay , perfluorinated compounds , perfluoroalkyl acids pfaas , perfluorooctane sulfonate , persistent organic pollutants , pfos precursors , pops , sulfluramid use , tissue distribution , todos os santos bay , trace-metal contamination , trophic magnification factors , tropical food web
The biomagnification of per- and polyfluoroalkyl substances (PFASs) was investigated in a tropical mangrove food web from an estuary in Bahia, Brazil. Samples of 44 organisms (21 taxa), along with biofilm, leaves, sediment and suspended particulate matter were analyzed. Sum (Sigma) PFAS concentrations in biota samples were dominated by perfluorooctane sulfonate (PFOS, 93% detection frequency in tissues; 0.05 to 1.97 ng g(-1) ww whole-body (wb)), followed by perfluorotridecanoate (PFTrDA, 57%; 0.01 to 0.28 ng g(-1) ww wb). PFOS precursors such as perfluorooctane sulfonamide (FOSA, 54%; 0.01 to 0.32 ng g(-1) ww wb) and N-ethyl perfluorooctane sulfonamide (EtFOSA; 30%; 0.01 to 0.21 ng g(-1) ww wb) were also detected. PFAS accumulation profiles revealed different routes of exposure among bivalve, crustacean and fish groups. Statistics for left-censored data were used in order to minimize bias on trophic magnification factors (TMFs) calculations. TMFs >1 were observed for PFOS (linear + branched isomers), EtFOSA (linear + branched isomers), and perfluorononanoate (PFNA), and in all cases, dissimilar accumulation patterns were observed among different trophic positions. The apparent biodilution of some long-chain PFCAs through the food chain (TMF < 1) may be due to exposure from multiple PFAS sources. This is the first study investigating bioaccumulation of PFASs in a tropical food web and provides new insight on the behavior of this ubiquitous class of contaminants. (C) 2020 The Authors. Published by Elsevier B.V.

Understanding Biofilm Formation in Ecotoxicological Assays With Natural and Anthropogenic Particulates

Gorokhova, E; Motiei, A; El-Shehawy, R
2021 | Front. Microbiol. | 12
actinobacteria , bacteria , bacterial assemblages on microplastic , balos , daphnia , daphnia-magna , diverse , ecotoxicological testing , microbiome , nov. , particle aggregation , plastic debris , predation , resistance , sediments , size distribution , suspended clay , zooplankton
Fossil-made polymers harbor unique bacterial assemblages, and concerns have been raised that ingested microplastic may affect the consumer gut microbiota and spread pathogens in animal populations. We hypothesized that in an ecotoxicity assay with a mixture of polystyrene (PS) and clay: (1) microbiome of the test animals inoculates the system with bacteria; (2) relative contribution of PS and the total amount of suspended solids (SS) select for specific bacterial communities; and (3) particle aggregation is affected by biofilm community composition, with concomitant effects on the animal survival. Mixtures of PS and clay at different concentrations of SS (10, 100, and 1000 mg/L) with a varying microplastics contribution (%PS; 0-80%) were incubated with Daphnia magna, whose microbiome served as an inoculum for the biofilms during the exposure. After 4-days of exposure, we examined the biofilm communities by 16S rRNA gene sequencing, particle size distribution, and animal survival. The biofilm communities were significantly different from the Daphnia microbiota used to inoculate the system, with an overrepresentation of predatory, rare, and potentially pathogenic taxa in the biofilms. The biofilm diversity was stimulated by %PS and decreased by predatory bacteria. Particle aggregate size and the biofilm composition were the primary drivers of animal survival, with small particles and predatory bacteria associated with a higher death rate. Thus, in effect studies with solid waste materials, ecological interactions in the biofilm can affect particle aggregation and support potentially harmful microorganisms with concomitant effects on the test animals.

Evaluating reliability and risk of bias of in vivo animal data for risk assessment of chemicals – Exploring the use of the SciRAP tool in a systematic review context

Waspe, J; Bui, T; Dishaw, L; Kraft, A; Luke, A; Beronius, A
2021 | Environ Int | 146
environmental-health science , guidance , iris , methodology , ohat , randomized controlled-trials , reliability , reporting quality , risk of bias , scales , scirap , systematic review , toxrtool , weight
Within the field of health risk assessment, it is essential that evaluations of reliability or validity of toxicity data are conducted with structure and transparency. To this end, different tools for evaluating toxicity studies have been developed by different groups and organizations, for different specific purposes. The Science in Risk Assessment and Policy (SciRAP) tool was developed for use in the regulatory health risk assessment of chemicals and to promote structured and transparent evaluation of study reliability within European regulatory frameworks. As such, the SciRAP tool is not specifically tailored for use in a systematic review context. However, in light of the current movement towards applying systematic review in the field of environmental health and chemical assessments and European chemicals regulation, we were interested in exploring how SciRAP could be applied in such a context. To achieve this, the scope of the SciRAP tool was first compared to two tools developed based on systematic review principles at the US Environmental Protection Agency's IRIS program and the National Toxicology Program's Office of Health Assessment and Translation (OHAT). Next, the SciRAP and IRIS tools were both applied in a case study to evaluate the same nine in vivo animal studies and the resulting evaluations were compared. The SciRAP tool was found to address the majority of the elements included for study evaluation in the OHAT and IRIS tools. In the case study, no major differences were found in the conclusions drawn when using SciRAP or IRIS tools. However, future developments to bring the SciRAP tool more in line with systematic review principles were identified and are discussed. Overall, this work illustrates the advantages of applying structured and pre-defined methods for study evaluation and provides a unique case study comparing the impact of using different tools for evaluating animal toxicity studies.

Weathering Plastics as a Planetary Boundary Threat: Exposure, Fate, and Hazards

Arp, HPH; Kuhnel, D; Rummel, C; MacLeod, M; Potthoff, A; Reichelt, S; Rojo-Nieto, E; Schmitt-Jansen, M; Sonnenberg, J; Toorman, E; Jahnke, A
2021 | Environ. Sci. Technol. | 55 (11) (7246-7255)
debris , degradation , density polyethylene , environmental plastics , environments , exposure , fate , fragmentation , hazards , marine , microplastic particles , planetary boundary threat , polystyrene , transport , water , weathering
We described in 2017 how weathering plastic litter in the marine environment fulfils two of three criteria to impose a planetary boundary threat related to "chemical pollution and the release of novel entities": (1) planetary-scale exposure, which (2) is not readily reversible. Whether marine plastics meet the third criterion, (3) eliciting a disruptive impact on vital earth system processes, was uncertain. Since then, several important discoveries have been made to motivate a re-evaluation. A key issue is if weathering macroplastics, microplastics, nanoplastics, and their leachates have an inherently higher potential to elicit adverse effects than natural particles of the same size. We summarize novel findings related to weathering plastic in the context of the planetary boundary threat criteria that demonstrate (1) increasing exposure, (2) fate processes leading to poorly reversible pollution, and (3) (eco)toxicological hazards and their thresholds. We provide evidence that the third criterion could be fulfilled for weathering plastics in sensitive environments and therefore conclude that weathering plastics pose a planetary boundary threat. We suggest future research priorities to better understand (eco)toxicological hazards modulated by increasing exposure and continuous weathering processes, to better parametrize the planetary boundary threshold for plastic pollution.

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