The effects of electrochemical pretreatment and curing environment on strength and leaching of stabilized/solidified contaminated sediment.

Stabilization and solidification (S/S) is known to improve the structural properties of sediment and reduce contaminant mobility, enabling the utilization of dredged contaminated sediment. Further reduction of contaminants (e.g., tributyltin (TBT) and metals) can be done using electrochemical treatment prior to S/S and could potentially minimize contaminant leaching. This is the first study on how electrochemical pretreatment affects the strength and leaching properties of stabilized sediments. It also investigates how salinity and organic carbon in the curing liquid affect the stabilized sediment.The results showed that the electrolysis reduced the content of TBT by 22% and zinc by 44% in the sediment. The electrolyzed stabilized samples met the requirements for compression strength and had a reduced surface leaching of zinc. Curing in saline water was beneficial for strength development and reduced the leaching of TBT compared to curing in fresh water. The results indicate that pretreatment prior to stabilization could be beneficial in reducing contaminant leaching and recovering metals from the sediment. The conclusion is that a better understanding of the changes in the sediment caused by electrochemical treatment and how these changes interact with stabilization reactions is needed. In addition, it is recommended to investigate the strength and leaching behavior in environments similar to the intended in situ conditions.

Identification of novel arsenic resistance genes in yeast.

Arsenic is a toxic metalloid that affects human health by causing numerous diseases and by being used in the treatment of acute promyelocytic leukemia. Saccharomyces cerevisiae (budding yeast) has been extensively utilized to elucidate the molecular mechanisms underlying arsenic toxicity and resistance in eukaryotes. In this study, we applied a genomic DNA overexpression strategy to identify yeast genes that provide arsenic resistance in wild-type and arsenic-sensitive S. cerevisiae cells. In addition to known arsenic-related genes, our genetic screen revealed novel genes, including PHO86, VBA3, UGP1, and TUL1, whose overexpression conferred resistance. To gain insights into possible resistance mechanisms, we addressed the contribution of these genes to cell growth, intracellular arsenic, and protein aggregation during arsenate exposure. Overexpression of PHO86 resulted in higher cellular arsenic levels but no additional effect on protein aggregation, indicating that these cells efficiently protect their intracellular environment. VBA3 overexpression caused resistance despite higher intracellular arsenic and protein aggregation levels. Overexpression of UGP1 led to lower intracellular arsenic and protein aggregation levels while TUL1 overexpression had no impact on intracellular arsenic or protein aggregation levels. Thus, the identified genes appear to confer arsenic resistance through distinct mechanisms but the molecular details remain to be elucidated.

Removal of organotin compounds and metals from Swedish marine sediment using Fenton's reagent and electrochemical treatment.

Metal and tributyltin (TBT) contaminated sediments are problematic for sediment managers and the environment. This study is the first to compare Fenton's reagent and electrochemical treatment as remediation methods for the removal of TBT and metals using laboratory-scale experiments on contaminated dredged sediment. The costs and the applicability of the developed methods were also compared and discussed. Both methods removed > 98% TBT from TBT-spiked sediment samples, while Fenton's reagent removed 64% of the TBT and electrolysis 58% of the TBT from non-spiked samples. TBT in water phase was effectively degraded in both experiments on spiked water and in leachates during the treatment of the sediment. Positive correlations were observed between TBT removal and the added amount of hydrogen peroxide and current density. Both methods removed metals from the sediment, but Fenton's reagent was identified as the most potent option for effective removal of both metals and TBT, especially from highly metal-contaminated sediment. However, due to risks associated with the required chemicals and low pH level in the sediment residue following the Fenton treatment, electrochemical treatment could be a more sustainable option for treating larger quantities of contaminated sediment.

Integrated cost and environmental impact assessment of management options for dredged sediment.

Large quantities of sediment must be dredged regularly to enable marine transport and trade. The sediments are often polluted, with e.g. metals, which limits the management options. The aim of this study has been to assess costs and environmental impacts (impact on climate, marine organisms, etc.) of different management options for polluted dredged sediment, by combining life-cycle assessment (LCA) of the climate impact, scoring of other environmental aspects and a cost evaluation. This approach has been used to study both traditional and new management alternatives for a real port case. The studied options include landfilling, deep-sea disposal, construction of a port area using a stabilization and solidification (S/S) method, and a combination of the aforementioned methods with the innovative option of metal recovery through sediment electrolysis. The LCA showed that deep-sea disposal had the lowest climate impact. The assessment of the other environmental impacts showed that the result varied depending on the pollution level and the time perspective used (short or long-term). Using sediment for construction had the highest climate impact, although other environmental impacts were comparably low. Electrolysis was found to be suitable for highly polluted sediments, as it left the sediment cleaner and enabled recovery of precious metals, however the costs were high. The results highlight the complexity of comparing different environmental impacts and the benefits of using integrated assessments to provide clarity, and to evaluate both the synergetic and counteracting effects associated with the investigated scenarios and may aid early-stage decision making.

Genome-wide imaging screen uncovers molecular determinants of arsenite-induced protein aggregation and toxicity.

The toxic metalloid arsenic causes widespread misfolding and aggregation of cellular proteins. How these protein aggregates are formed in vivo, the mechanisms by which they affect cells and how cells prevent their accumulation is not fully understood. To find components involved in these processes, we performed a genome-wide imaging screen and identified Saccharomyces cerevisiae deletion mutants with either enhanced or reduced protein aggregation levels during arsenite exposure. We show that many of the identified factors are crucial to safeguard protein homeostasis (proteostasis) and to protect cells against arsenite toxicity. The hits were enriched for various functions including protein biosynthesis and transcription, and dedicated follow-up experiments highlight the importance of accurate transcriptional and translational control for mitigating protein aggregation and toxicity during arsenite stress. Some of the hits are associated with pathological conditions, suggesting that arsenite-induced protein aggregation may affect disease processes. The broad network of cellular systems that impinge on proteostasis during arsenic stress identified in this current study provides a valuable resource and a framework for further elucidation of the mechanistic details of metalloid toxicity and pathogenesis. This article has an associated First Person interview with the first authors of the paper.

Low impact leaching agents as remediation media for organotin and metal contaminated sediments.

All over the world, elevated levels of metals and the toxic compound tributyltin (TBT) and its degradation products are found in sediments, especially close to areas associated with shipping and anthropogenic activities. Ports require regular removal of sediments. As a result, large volumes of often contaminated sediments must be managed. The aim of this study was to investigate enhanced leaching as a treatment method for organotin (TBT) and metal (Cu and Zn) contaminated marine sediments. Thus, enabling the possibility to reuse these cleaner masses e.g. in construction. In addition to using acid and alkaline leaching agents that extract the OTs and metals but reduce the management options post treatment, innovative alternatives such as EDDS, hydroxypropyl cellulose, humic acid, iron colloids, ultra-pure Milli-Q water, saponified tall oil ("soap"), and NaCl were tested. Organotin removal ranged from 36 to 75%, where the most efficient leaching agent was Milli-Q water, which was also the leaching agent achieving the highest removal rate for TBT (46%), followed by soap (34%). The TBT reduction accomplished by Milli-Q water and soap leaching enabled a change in Swedish sediment classification from the highest class to the second highest class. The highest reduction of Zn was in HPC leached samples (39% removal) and Cu in EDDS leached samples (33% removal). Although high metal and OT leaching were achieved, none of the investigated leaching agents are sufficiently effective for the removal of both metals and OTs. The results of this study indicate that leaching with ultra-clean water, such as Milli-Q water, may be sufficient to treat TBT contaminated sediments and potentially allow mass reuse.

Physical, genetic and functional interactions between the eisosome protein Pil1 and the MBOAT O-acyltransferase Gup1.

The Saccharomyces cerevisiae MBOAT O-acyltransferase Gup1 is involved in many processes, including cell wall and membrane composition and integrity, and acetic acid-induced cell death. Gup1 was previously shown to interact physically with the mitochondrial membrane VDAC (Voltage-Dependent Anion Channel) protein Por1 and the ammonium transceptor Mep2. By co-immunoprecipitation, the eisosome core component Pil1 was identified as a novel physical interaction partner of Gup1. The expression of PIL1 and Pil1 protein levels were found to be unaffected by GUP1 deletion. In ∆gup1 cells, Pil1 was distributed in dots (likely representing eisosomes) in the membrane, identically to wt cells. However, ∆gup1 cells presented 50% less Pil1-GFP dots/eisosomes, suggesting that Gup1 is important for eisosome formation. The two proteins also interact genetically in the maintenance of cell wall integrity, and during arsenite and acetic acid exposure. We show that Δgup1 Δpil1 cells take up more arsenite than wt and are extremely sensitive to arsenite and to acetic acid treatments. The latter causes a severe apoptotic wt-like cell death phenotype, epistatically reverting the ∆gup1 necrotic type of death. Gup1 and Pil1 are thus physically, genetically and functionally connected.

A comparative study of macroinvertebrate biodiversity in highway stormwater ponds and natural ponds.

The use of stormwater ponds along the highways is shown to be an effective alternative to conventional systems, which are usually sewers. These ponds have the potential to combine their primary function of pollution and peak flow control with the promotion of biodiversity. The present study focuses on comparing natural and highway stormwater ponds in terms of environmental conditions and biodiversity of macroinvertebrate communities. Twelve highway stormwater ponds and nineteen natural ponds (located within or in the vicinity of cultivated landscape) were explored for the number of taxa, community composition, and selected environmental variables: pH, conductivity, pond surface area, the number of ponds within 1 km radius, and the distance to nearest neighboring pond. Highway stormwater ponds showed much higher conductivity, which is a good proxy for chloride concentration and highway pollutants. In addition, the surface area of stormwater ponds was almost twice as big as that of natural ponds. The biological community composition was very different between the two types of ponds, and the number of taxa was slightly higher in the highway stormwater ponds. The most important variables responsible for the variation in the biological community composition were conductivity, pond surface area, and the number of ponds within 1 km radius. This study supports that, in addition to their role in pollution and peak flow control, stormwater ponds have the potential to provide a habitat that may otherwise be unavailable along the highway.

Integrated assessment of management strategies for metal-contaminated dredged sediments - What are the best approaches for ports, marinas and waterways?

Sediments in ports, marinas and waterways around the world are often contaminated with metals arising from anthropogenic activities. Regular dredging is needed to achieve an appropriate water depth and reduce the environmental impact of pollutants. The aim of this study was to develop an integrated assessment method for comparing various management strategies for dredged sediments at six case study sites in Sweden. Short- and long-term environmental impacts were investigated for different management approaches, including landfilling, deep-sea disposal, metal extraction in combination with the two aforementioned, and natural recovery (no dredging). The potential value of metals in the sediments was estimated using sediment metal contents and current metal prices. Additionally, an assessment of how metal extraction could result in lower management costs was carried out. The cost of the different management approaches was calculated and evaluated together with the corresponding environmental impacts. This study shows that there is a monetary value in dredged materials, in terms of metal content, and that the materials can potentially be used for metal extraction. Metal extraction may also help to reduce the management costs, as cleaner materials are cheaper to handle. The choice of metal recovery method is important in both monetary and environmental terms, potentially contributing to a circular economy. In the future, metal recovery may become more profitable, as technologies are improved, and due to probable increases in metal prices and landfill costs.

DNA metabarcoding adds valuable information for management of biodiversity in roadside stormwater ponds.

ABSTRACT: Stormwater ponds are used to compensate for the adverse effects that road runoff might have on the natural environment. Depending on their design and placement, stormwater ponds can act as both refugia and traps for local biodiversity. To evaluate the impact of stormwater ponds on biodiversity, it is critical to use effective and precise methods for identification of life associated with the water body. DNA metabarcoding has recently become a promising tool for identification and assessment of freshwater biodiversity.Using both morphology and DNA metabarcoding, we analyze species richness and biological composition of samples from 12 stormwater ponds and investigate the impact of pond size and pollution levels in the sediments and water column on the macroinvertebrate community structure.DNA metabarcoding captured and identified more than twice the number of taxa compared to morphological identification. The (dis)similarity of macroinvertebrate community composition in different ponds showed that the ponds appear better separated in the results obtained by DNA metabarcoding, but that the explained variation is higher for the results obtained by morphologically identification, since it provides abundance data.The reliance on morphological methods has limited our perception of the aquatic biodiversity in response to anthropogenic stressors, thereby providing inaccurate information for appropriate design and management of stormwater ponds; these drawbacks can be overcome by DNA metabarcoding. Synthesis and applications. The results indicate that DNA metabarcoding is a useful tool in identifying species, especially Diptera, which are difficult to determine. Application of DNA metabarcoding greatly increases the number of species identified at each sampling site, thereby providing a more accurate information regarding the way the ponds function and how they are affected by management. OPEN PRACTICES: This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://www.ebi.ac.uk/ena/data/view/PRJEB30841.

Impact of environmental factors on aquatic biodiversity in roadside stormwater ponds.

Constructed stormwater ponds mitigate runoff volumes and pollution, and provide other ecosystem services, such as supporting biodiversity, but these services attracted relatively less attention. The impacts of the pollution levels in the water column and sediments, the physical characteristics of ponds, and the presence of amphibians on the macroinvertebrate community composition and biodiversity were explored in twelve stormwater ponds in Norway. Also, the similarities between macroinvertebrate, zooplankton and plant communities were explored. Most of the taxa displayed in the ordination diagram were positively correlated with the pond size and the number of neighbouring ponds, and negatively correlated with the pollution levels in the water column and sediments. However, no statistically significant impacts on the number of taxa and Shannon index were observed. There were low similarities between the macroinvertebrate and zooplankton community compositions as well as between the plant and macroinvertebrate community compositions in the stormwater ponds. We observed a significant positive correlation between the number of plant and of zooplankton taxa, and a weak non-significant positive correlation between the number of plant and of macroinvertebrate taxa. Overall, the explanatory variables had a significant impact on the community composition, but not on the number of taxa nor Shannon index.

Mineral dust as a driver of carbon accumulation in northern latitudes.

Peatlands in northern latitudes sequester one third of the world's soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the "Great Bog") in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m-2 yr-1 - more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

Importance of triggers and veto-barriers for the implementation of sanitation in informal peri-urban settlements - The case of Cochabamba, Bolivia.

An estimated 2.4 billion people lack access to improved sanitation which has devastating consequences for human health and the environment. Understanding what constitute sanitation demand is crucial for accelerating the spread of improved sanitation. This study aims to understand the adoption mechanisms for improved sanitation. An informal peri-urban settlement in Cochabamba, Bolivia was selected as a case study to understand adoption patterns. Various qualitative methods of data collection and analysis were employed. The findings showed that pour-flush toilets was the only preferred sanitation alternative at the study site. An adoption framework for waterborne toilets was developed based on diffusion of innovation theory. Factors that influence adoption were identified. Some functioned as triggers and initiated adoption, whereas some factors blocked adoption and constituted veto-barriers. Most factors were connected to the individual household situation and its members, but neighborhood development also affected pour-flush adoption. Based on adoption time the residents were divided into the following adoption groups: first adopters, early majority, late majority, laggards and non-adopters. Each adoption group followed its own adoption route with specific characteristics and respective triggers or veto-barriers. We argue that the strong demand for waterborne toilets in peri-urban areas need to be recognized and the developed framework could be used for customizing sanitation improvement programs for certain target groups.

Wastewater management in small towns - understanding the failure of small treatment plants in Bolivia.

Wastewater management in developing countries is a challenge, especially in small towns with rapid population growth. This study aims at assessing the performance and management of five treatment plants (TPs) in rural areas of Cochabamba, Bolivia. Pollutants' concentrations, wastewater flows, hydraulic and organic loads and hydraulic retention times were determined in three small treatment plants (2000-10,000 population equivalent [p.e.]; flow > 432 m3/d) and two very small treatment plants (<2000 p.e.; flow < 432 m3/d). The performance assessment was based on operational parameters, treatment efficiency and effluent quality. Management data were collected through semi-structured interviews with managers of local water associations. The results support that the poor performance of the TPs is due to lack of operational expertise and financial resources for adequate operation and maintenance (O&M). Additionally, effective treatment was affected by the type of technology used and whether the plant design included plans for O&M with available resources. This study contributes to a better understanding of actual operating conditions of wastewater TPs in small towns, thus providing needed information regarding technology selection, design, implementation and operation.

Aquatic biodiversity in sedimentation ponds receiving road runoff - What are the key drivers?

Recently, increased attention has been paid to biodiversity conservation provided by blue-green solutions such as engineered ponds that are primarily established for water treatment and flood control. However, little research has been done to analyse the factors that affect biodiversity in such ponds. The purpose of this study was to evaluate the influence of environmental factors on aquatic biodiversity, mainly macroinvertebrate communities, in road sedimentation ponds in order to provide a foundation for recommendations on aquatic biodiversity conservation. Multivariate statistical methods, including unconstrained and constrained analysis, were applied to examine the relationships between organisms and the water quality as well as physical factors (including plant cover). Stepwise multiple regressions indicated that the most important variables governing the variation in the biological community composition were pond size, average annual daily traffic, metals, chloride, distance to the closest pond from study pond, dissolved oxygen, hydrocarbons, and phosphorus. The presence of most taxa was positively correlated with pond size and negatively correlated with metals. Small ponds with high pollutant loadings were associated with a low diversity and dominated by a few pollution tolerant taxa such as oligochaetes. A comprehensive understanding of impacts of various environmental factors on aquatic biodiversity is important to effectively promote and conserve aquatic biodiversity in such sedimentation ponds. Our results indicate that road sedimentation ponds should be designed large enough, because large ponds are likely to provide a more heterogeneous habitat and thus contain a species rich fauna. In addition, larger ponds seem to be less contaminated due to dilution compared to smaller ponds, thereby maintaining a higher biodiversity. Finally, creating some additional ponds in the vicinity of the sedimentation ponds in areas with few water bodies would increase the connectivity that facilitates the movement of invertebrates between ponds.

Identification of platinum nanoparticles in road dust leachate by single particle inductively coupled plasma-mass spectrometry.

Elevated platinum (Pt) concentrations are found in road dust as a result of emissions from catalytic converters in vehicles. This study investigates the occurrence of Pt in road dust collected in Ghent (Belgium) and Gothenburg (Sweden). Total Pt contents, determined by tandem ICP-mass spectrometry (ICP-MS/MS), were in the range of 5 to 79ngg-1, comparable to the Pt content in road dust of other medium-sized cities. Further sample characterization was performed by single particle (sp) ICP-MS following an ultrasonic extraction procedure using stormwater runoff for leaching. The method was found to be suitable for the characterization of Pt nanoparticles in road dust leachates. The extraction was optimized using road dust reference material BCR-723, for which an extraction efficiency of 2.7% was obtained by applying 144kJ of ultrasonic energy. Using this method, between 0.2% and 18% of the Pt present was extracted from road dust samples. spICP-MS analysis revealed that Pt in the leachate is entirely present as nanoparticles of sizes between 9 and 21nm. Although representing only a minor fraction of the total content in road dust, the nanoparticulate Pt leachate is most susceptible to biological uptake and hence most relevant in terms of bioavailability.

Assessment of drinking water quality at the tap using fluorescence spectroscopy.

Treated drinking water may become contaminated while travelling in the distribution system on the way to consumers. Elevated dissolved organic matter (DOM) at the tap relative to the water leaving the treatment plant is a potential indicator of contamination, and can be measured sensitively, inexpensively and potentially on-line via fluorescence and absorbance spectroscopy. Detecting elevated DOM requires potential contamination events to be distinguished from natural fluctuations in the system, but how much natural variation to expect in a stable distribution system is unknown. In this study, relationships between DOM optical properties, microbial indicator organisms and trace elements were investigated for households connected to a biologically-stable drinking water distribution system. Across the network, humic-like fluorescence intensities showed limited variation (RSD = 3.5-4.4%), with half of measured variation explained by interactions with copper. After accounting for quenching by copper, fluorescence provided a very stable background signal (RSD < 2.2%) against which a ∼2% infiltration of soil water would be detectable. Smaller infiltrations would be detectable in the case of contamination by sewage with a strong tryptophan-like fluorescence signal. These findings indicate that DOM fluorescence is a sensitive indicator of water quality changes in drinking water networks, as long as potential interferents are taken into account.

Cadmium Causes Misfolding and Aggregation of Cytosolic Proteins in Yeast.

Cadmium is a highly poisonous metal and is classified as a human carcinogen. While its toxicity is undisputed, the underlying in vivo molecular mechanisms are not fully understood. Here, we demonstrate that cadmium induces aggregation of cytosolic proteins in living Saccharomyces cerevisiae cells. Cadmium primarily targets proteins in the process of synthesis or folding, probably by interacting with exposed thiol groups in not-yet-folded proteins. On the basis of in vitro and in vivo data, we show that cadmium-aggregated proteins form seeds that increase the misfolding of other proteins. Cells that cannot efficiently protect the proteome from cadmium-induced aggregation or clear the cytosol of protein aggregates are sensitized to cadmium. Thus, protein aggregation may contribute to cadmium toxicity. This is the first report on how cadmium causes misfolding and aggregation of cytosolic proteins in vivo The proposed mechanism might explain not only the molecular basis of the toxic effects of cadmium but also the suggested role of this poisonous metal in the pathogenesis of certain protein-folding disorders.

Drift correction of the dissolved signal in single particle ICPMS.

A method is presented where drift, the random fluctuation of the signal intensity, is compensated for based on the estimation of the drift function by a moving average. It was shown using single particle ICPMS (spICPMS) measurements of 10 and 60 nm Au NPs that drift reduces accuracy of spICPMS analysis at the calibration stage and during calculations of the particle size distribution (PSD), but that the present method can again correct the average signal intensity as well as the signal distribution of particle-containing samples skewed by drift. Moreover, deconvolution, a method that models signal distributions of dissolved signals, fails in some cases when using standards and samples affected by drift, but the present method was shown to improve accuracy again. Relatively high particle signals have to be removed prior to drift correction in this procedure, which was done using a 3 × sigma method, and the signals are treated separately and added again. The method can also correct for flicker noise that increases when signal intensity is increased because of drift. The accuracy was improved in many cases when flicker correction was used, but when accurate results were obtained despite drift, the correction procedures did not reduce accuracy. The procedure may be useful to extract results from experimental runs that would otherwise have to be run again. Graphical Abstract A method is presented where a spICP-MS signal affected by drift (left) is corrected (right) by adjusting the local (moving) averages (green) and standard deviations (purple) to the respective values at a reference time (red). In combination with removing particle events (blue) in the case of calibration standards, this method is shown to obtain particle size distributions where that would otherwise be impossible, even when the deconvolution method is used to discriminate dissolved and particle signals.