Background
The International Maritime Organization (IMO) has set limits on sulphur content in fuels for marine transport. However, vessels continue to use these residual high-sulphur fuels in ...combination with exhaust gas cleaning systems (EGCS or scrubbers). Next to high sulphur, combustion of these fuels also results in higher emissions of contaminants including metals and PAHs. In scrubbers, exhaust gases are sprayed with water in order to remove SOx, resulting in acidic washwater with elevated contaminant concentrations discharged in the aquatic ecosystem. The number of vessels with scrubbers is increasing rapidly, but knowledge on washwater quality and impact are limited.
Results
The scrubber washwater is found to be acidic with elevated concentrations of, e.g. zinc, vanadium, copper, nickel, phenanthrene, naphthalene, fluorene and fluoranthene. Model calculations on the effects of scrubber discharge under scenario HIGH (20% of vessels, 90th percentile concentrations) on the water quality in harbour docks showed a decrease in pH of 0.015 units and an increase in surface water concentrations for e.g. naphthalene (189% increase) and vanadium (46% increase).
Conclusions
The IMO established sulphur regulations to mitigate the impact of high sulphur emissions of the maritime sector. However, the use of open-loop scrubbers as an abatement technology will not reduce their contribution to ocean acidification. In addition, different types of scrubbers discharge washwater that is acutely toxic for aquatic organisms. However, washwater is diluted and the compounds for which a large increase in surface water concentrations was calculated in the Antwerp (Belgium) harbour docks (naphthalene > phenanthrene > fluorene > acenaphthene > vanadium) were not the compounds that already exceed their respective Water Quality Standards (WQS). Nevertheless, the WQS of several ‘priority hazardous substances’ (Water Framework Directive) are already exceeded in the docks and the Scheldt estuary. Since these hazardous substances are also identified in the washwater, scrubber washwater discharge should be discouraged in coastal waters and estuaries with large ecological value.
A systematic review of the available evidence examining the cost of work-related stress (WRS) would yield important insights into the magnitude of this social phenomenon. The objective of this review ...was to collate, extract, and synthesize economic evaluations of the cost of WRS to society. A research protocol was developed. Included cost-of-illness (COI) studies estimated the cost of WRS at a societal level, and were published in English, French or German. Searches were carried out in ingentaconnect, EBSCO, JSTOR, Science Direct, Web of Knowledge, Google, and Google scholar. Included studies were assessed against 10 COI quality assessment criteria. Fifteen studies met the inclusion criteria and were reviewed. These originated from Australia, Canada, Denmark, France, Sweden, Switzerland, the United Kingdom, and the EU-15. The total estimated cost of WRS was observed to be considerable and ranged substantially from US$221.13 million to $187 billion. Productivity related losses were observed to proportionally contribute the majority of the total cost of WRS (between 70 to 90%), with health care and medical costs constituting the remaining 10 to 30%. The evidence reviewed here suggests a sizable financial burden imposed by WRS on society. The observed range of cost estimates was understood to be attributable to variations in definitions of WRS; the number and type of costs estimated; and, in how production loss was estimated. It is postulated that the cost estimates identified by this review are likely conservative because of narrow definitions of WRS and the exclusion of diverse range of cost components.
Flux calculations demonstrate that many estuaries are natural filters for trace metals. Yet, the underlying processes are poorly investigated. In the present study, it was hypothesized that ...intertidal marshes contribute significantly to the contaminant filter function of estuaries. Trace metal concentrations and sediment characteristics were measured along a transect from the subtidal, over an intertidal flat and marsh to a restored marsh with controlled reduced tide. Metal concentrations in the intertidal and restored marsh were found to be a factor two to five higher than values in the subtidal and intertidal flat sediments. High metal concentrations and high accretion rates indicate a high metal accumulation capacity of the intertidal marshes. Overbank sedimentation in the tidal marshes of the entire estuary was calculated to remove 25% to 50% of the riverine metal influx, even though marshes comprise less than 8% of the total surface of the estuary. In addition, the large-scale implementation of planned tidal marsh restoration projects was estimated to almost double the trace metal storage capacity of the present natural tidal marshes in the estuary.
Cold-water coral reefs and adjacent sponge grounds are distributed widely in the deep ocean, where only a small fraction of the surface productivity reaches the seafloor as detritus. It remains ...elusive how these hotspots of biodiversity can thrive in such a food-limited environment, as data on energy flow and organic carbon utilization are critically lacking. Here we report in situ community respiration rates for cold-water coral and sponge ecosystems obtained by the non-invasive aquatic Eddy Correlation technique. Oxygen uptake rates over coral reefs and adjacent sponge grounds in the Træna Coral Field (Norway) were 9-20 times higher than those of the surrounding soft sediments. These high respiration rates indicate strong organic matter consumption, and hence suggest a local focusing onto these ecosystems of the downward flux of organic matter that is exported from the surface ocean. Overall, our results show that coral reefs and adjacent sponge grounds are hotspots of carbon processing in the food-limited deep ocean, and that these deep-sea ecosystems play a more prominent role in marine biogeochemical cycles than previously recognized.
Due to an increasing appreciation of the highly valuable ecosystem services of tidal marshes, an increasing number of projects are being implemented to re-introduce tides on formerly embanked land ...using a variety of ‘soft’ engineering techniques. However, the ecological development of the recreated tidal marshes largely depends on the design of the project, as this determines the hydro-geomorphological evolution. In this study we compare the hydro-geomorphological development in two marsh restoration projects in the Scheldt estuary (Belgium), one with a controlled reduced tidal exchange (CRT) and one with a full tidal exchange (FTE) between the marsh and adjacent estuary, based on ten years (CRT) and five years (FTE) of data on sedimentation/erosion rates, sediment properties and tidal characteristics. The results clearly show that the CRT technique strongly reduces the input of sediments, whereas larger water depths in the FTE led to extremely high sedimentation rates of 60–400 cm yr−1 in the first 2.5 months. The rapidly accreting sediments in the FTE consolidated much less than in the CRT and this poor sediment consolidation may have contributed to slower vegetation and benthos colonization in the FTE.
This comparison of two different tidal systems can serve as an example to show the effect of different techniques to re-introduce tides on the creation of tidal marshes on low-lying areas. Depending on the tidal marsh development goals, different hydrologic regimes and thereby different sedimentation rates may be desired. For example, when the objective is to contribute to estuarine flood risk mitigation by creating and maintaining a high water buffering capacity in restored tidal marshes, a CRT system with low sedimentation rates is preferred. However, when the objective is to build up soil elevation, for example as an adaptation to sea level rise, the FTE technique as studied here could be a good way to trap sediments.
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•Tidal re-introduction using controlled reduced tide strongly reduces input of sediments.•Full tidal exchange in low-lying areas results in high sedimentation rates.•Controlled reduced tide is defined by extended flooding and reduced tidal amplitude.•Full tidal exchange results in exact copy of natural tide in restoration area.
Tidal marsh (re)creation on formerly embanked land is increasingly executed along estuaries and coasts in Europe and the USA, either by restoring complete or by reduced tidal exchange. Ecosystem ...functioning and services are largely affected by the hydro-geomorphologic development of these areas. For natural marshes, the latter is known to be steered by feedbacks between tidal inundation and sediment accretion, allowing marshes to reach and maintain an equilibrium elevation relative to the mean sea level. However, for marsh restoration sites, these feedbacks may be disturbed depending on the restoration design. This was investigated by comparing the inundation-elevation change feedbacks in a natural versus restoration site with reduced tidal exchange in the Scheldt estuary (Belgium). This study analyzes long-term (9 years) datasets on elevation change and tidal inundation properties to disentangle the different mechanisms behind this elevation-inundation feedback. Moreover, subsequent changes in sediment properties that may affect this feedback were explored. In the restoration area with reduced tidal exchange, we found a different elevation-inundation feedback than on natural marshes, which is a positive feedback on initially high sites (i.e., sediment accretion leads to increasing inundation, hence causing accelerating sediment accretion rates) and a gradual silting up of the whole area. Furthermore, there is evidence for the presence of a relict consolidated sediment layer. Consequently, shallow subsidence is less likely to occur. Although short-term ecological development of the tidal marsh was not impeded, long-term habitat development may be affected by the differences in hydro-geomorphological interactions. An increase of inundation frequency on the initially high sites may cause inhibition of habitat succession or even reversed succession. Over time, the climax state of the restoration area may be different compared to natural marshes. Moreover, sediment-related ecosystem services, such as nutrient and carbon burial, may be positively influenced because of continuing sedimentation, although flood water storage potential will decrease with increasing elevation. Depending on the restoration goals, ecosystem trajectories and delivery of ecosystem services can be controlled by adaptive management of the tidal volume entering the restoration area.
Abstract
Sediment transport in estuaries and the formation of estuarine turbidity maxima (ETM) highly depend on the ability of suspended particulate matter (SPM) to flocculate into larger aggregates. ...While most literature focuses on the small-scale impact of biological flocculants on the formation of larger aggregates, the influence of the flocculation process on large-scale estuarine SPM profiles is still largely unknown. In this paper, we study the impact of flocculation of SPM on the formation of ETM. For this, a semianalytical width-integrated model called iFlow is utilized and extended by a flocculation model. Starting from a complex one-class flocculation model, we show that flocculation may be described as a linear relation between settling velocity and suspended sediment concentration to capture its leading-order effect on the ETM formation. The model is applied to a winter case in the Scheldt estuary (Belgium, Netherlands) and calibrated to a unique, long-term, two-dimensional set of turbidity (cf. SPM) observations. First, model results with and without the effect of flocculation are compared, showing that the spatial and temporal variations of the settling velocity due to flocculation are essential to reproduce the observed magnitude of the suspended sediment concentrations and its dependence on river discharge. Second, flocculation results in tidally averaged land-inward sediment transport. Third, we conduct a sensitivity analysis of the freshwater discharge and floc breakup parameter, which shows that flocculation can cause additional estuarine turbidity maxima and can prevent flushing of the ETM for high freshwater inflow.
Organizational-level interventions often fail to bring about the desired results, but the reasons for this are still unclear. This introductory paper to a special issue of Work & Stress on ...organizational interventions discusses three issues to be considered in future intervention research if our understanding of the effectiveness of interventions is to be increased. First, there is a need to understand how and why interventions work. This calls for an examination of the processes connecting interventions to the desired outcomes. Second, attention should be paid to the appropriateness of interventions. Problems may be difficult to address, for example when they constitute inherent conditions of the job. Third, the use of a quasi-experimental study design does not guarantee a valid picture of the effectiveness of an intervention. For example, control groups may not be comparable to the experimental group, or participants may not be reached by the intervention. Based on these considerations, we conclude that mixed methods designs are needed to integrate process and outcome evaluation and increase the generalizability of interventions. Whereas concurrent changes such as mergers and downsizing may hinder the effectiveness of an intervention, they are part of today's organizations and should therefore be integrated into intervention designs.
Research investigating the effects of attitude‐focused interventions on doctors' and medical students' attitudes toward older adults has produced mixed results. The objective of this systematic ...review was to determine whether factors pertaining to study design and quality might provide some explanation of this inconclusive picture. Articles were judged of interest if they reported doctors' or medicals students' attitude scores before and after a geriatric‐focused intervention. Articles that did not report the measure used, mean scores, or inferential statistics were excluded. Twenty‐seven databases, including Medline, PsychInfo, and Embase, were searched through April 2011 using a systematic search strategy. After assessment and extraction, 27 studies met the eligibility criteria for this review. These studies demonstrated inconsistent results; 14 appeared successful in effecting positive attitude change toward older adults after an intervention, and 13 appeared unsuccessful. Attitude change results differed in line with the content of the intervention. Of the 27 studies, 11 interventions contained solely knowledge‐building content. Three of these studies demonstrated positive changes in doctors' or medical students' attitudes toward older adults after the intervention. The remaining 16 interventions incorporated an empathy‐building component, such as an aging simulation exercise or contact with a healthy older adult. Of these, 11 successfully demonstrated positive attitude change after the intervention. The inclusion of an empathy‐building task in an intervention appears to be associated with positive attitude change in medical students' and doctors' attitudes toward older adults.
•The impact of temporal variability in different parameters shows opposing trends.•These trends highly depend on the season and system characteristics.•Temporal fluctuations in light-climate ...significantly limit phytoplankton growth.•Temporal variations in light-climate delay the onset of an algal bloom by two weeks.
Phytoplankton primary production (PP) in turbid estuaries is often limited by light-availability. Two important factors altering light-climate are solar irradiance at the water surface and exponential light-extinction coefficient within the water column. Additionally, the depth of the water body changes the light-climate and corresponding PP by altering the ratio of the euphotic and mixing depth in a well-mixed estuary. These three parameters are highly variable yet are often assumed to be constant by both experimental scientists and modelers because of a lack of data or to reduce complexity. Because assuming constant parameters introduces an error, we utilize an idealized model of depth-integrated primary production to analyze the (individual) impact of temporal variability in these three parameters. We only consider the main tidal and solar constituents in temporal variability of the forcings and apply a second-order moment approximation to analyze the bias introduced to time-averaged PP estimates by neglecting temporal fluctuations. We demonstrate that the sign and magnitude of this bias are system-specific and depend on two non-dimensional parameters that characterize the system. The first is equivalent to the ratio of mixing and photic depth. The second accounts for typical incident irradiance and the photosynthetic parameters of the phytoplankton population present. To demonstrate the applicability of our approach, we apply the model to two cases in the Scheldt estuary (Belgium) in the brackish and freshwater part. In the first application, we study the impact of fluctuations on phytoplankton in dynamic equilibrium, where biomass is assumed to be constant. We show that variability in solar irradiance has the largest impact on time-averaged PP in dynamic equilibrium, resulting in a 30 percent decrease compared to time-invariant forcing. By comparing with a numerical integrator, we show that a second-order moment approximation correctly predicts the order of magnitude of the impact of temporal variability of the individual parameters. In the second application, we study the impact of fluctuations on unbounded exponential phytoplankton growth. Also here, fluctuations in solar irradiance have the largest impact and lead to a significant decrease in exponential growth. In this case study, we show that temporal fluctuations delay the onset of the biomass by two weeks and decrease the biomass by a factor 14 after two weeks compared to time invariant forcing. Additionally, we show that the temporal fluctuations induce low-frequency variability in phytoplankton biomass with similar periodicity as the spring-neap cycle, making it difficult to observe these phenomena in real-world time series.
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