Assessing the impacts of nonindigenous marine macroalgae: an update of current knowledge

Nonindigenous marine species continue to be one of the foremost threats to marine biodiversity. As an update to a 2007 review of the impacts of introduced macroalgae, we assessed 142 additional publications to describe species’ impacts as well as to appraise information on the mechanisms of impact. Only 10% of the currently known nonindigenous macroalgal species were subjects of ecological impact studies, with changed community composition as the most commonly reported effect. Economic impacts were rarely published. Recent research has focused on the impacts of introduced macroalgal assemblages: red algal introductions to the Hawaiian Islands and turf algae in the Mediterranean. Several general issues were apparent. First, many publications included nonsignificant results of statistical analyses but did not report associated power. As many of the studies also had low effect and sample size, the potential for type II errors is considerable. Second, there was no widely accepted framework to categorize and compare impacts between studies. Information in this updated review was still too sparse to identify general patterns and mechanisms of impact. This is a critical knowledge gap as rates of introductions and hence impacts of nonindigenous macroalgae are expected to accelerate with climate change and increasing global trade connectivity

The application of quasi-elastic neutron scattering to investigate hydrogen diffusion in an iron-based Fischer-Tropsch synthesis catalyst

Sasol Ltd., (PGRS-3) the University of Glasgow and the Engineering and Physical Sciences Research Council (EP/P505534/1) are thanked for the provision of postgraduate studentship (ALD). The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities (RB1720188) [26]. The Royal Society are thanked for the provision of an Industrial Fellowship (PBW).Iron-based Fischer–Tropsch synthesis (FTS) catalysts evolve in situ on exposure to synthesis gas (CO & H2) forming a mixture of iron oxides, iron carbides and carbonaceous deposits. Recently, the application of inelastic neutron scattering has shown the progressive formation of a hydrocarbonaceous overlayer during this catalyst conditioning period. The evolving nature of the catalyst alters the proportion of phases present within the catalyst, which may influence the transport of hydrogen within the reaction system. Preliminary quasi-elastic neutron scattering (QENS) measurements are used to investigate hydrogen diffusion within an un-promoted iron FTS catalyst that has experienced varying levels of time-on-stream (0, 12 and 24 h) of ambient pressure CO hydrogenation at 623 K. Measurements on the catalyst samples in the absence of hydrogen show the unreacted sample (t = 0 h) to exhibit little increase in motion over the temperature range studied, whereas the t = 12 and 24 h samples exhibit a pronounced change in motion with temperature. The contrast is attributed to the presence of the afore-mentioned hydrocarbonaceous overlayer. Measurements on the samples in the presence of liquid hydrogen show hydrogen diffusional characteristics to be modified as a function of the catalyst conditioning process but, due to the complexity of the evolving catalyst matrix, the hydrogen motion cannot be attributed to a particular phase or component of the catalyst. Problems in the use of hydrogen as a probe molecule in this instance are briefly considered. Coincident neutron diffraction studies undertaken alongside the QENS measurements confirm the transition from hematite pre-catalyst to that of Hägg carbide during the course of extended times-on-stream.Publisher PDFPeer reviewe

Hydrogen partitioning as a function of time-on-stream for an unpromoted iron-based Fischer-Tropsch synthesis catalyst applied to CO hydrogenation

Sasol Ltd., the EPSRC (award reference EP/P505534/1), and the University of Glasgow are thanked for the provision of a postgraduate studentship (ALD). The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities. The Royal Society is thanked for the provision of an Industry Fellowship (PBW).Inelastic neutron scattering (INS) is employed to examine the evolution of a promoter-free iron-based Fischer-Tropsch synthesis catalyst (∼10 g catalyst charge) that is exposed to ambient pressure CO hydrogenation at 623 K for up to 10 days time-on-stream (T-o-S). The longer reaction time is selected to better understand how the formation of a previously described hydrocarbonaceous overlayer corresponds to the catalyst conditioning process. Although the onset of pseudo steady-state reactor performance is observed at approximately 9 h T-o-S, INS establishes that the intensity of the C-H stretching mode of the sp3-hybridized component of the hydrocarbonaceous overlayer saturates at about 24 h T-o-S, while the corresponding intensity of the C-H stretching mode of the sp2-hybridized component requires 100-200 h T-o-S to achieve saturation. This novel series of measurements reveal different aspects of the complex catalyst evolutionary process to be indirectly connected with catalytic turnover.Publisher PDFPeer reviewe

Development of a risk assessment framework to predict invasive species establishment for multiple taxonomic groups and vectors of introduction

A thorough assessment of aquatic nonindigenous species’ risk facilitates successful monitoring and prevention activities. However, species- and vector-specific information is often limited and difficult to synthesize across a single risk framework. To address this need, we developed an assessment framework capable of estimating the potential for introduction, establishment, and impact by aquatic nonindigenous species from diverse spatial origins and taxonomic classification, in novel environments. Our model builds on previous approaches, while taking on a new perspective for evaluation across species, vectors and stages to overcome the limitations imposed by single species and single vector assessments. We applied this globally-relevant framework to the Laurentian Great Lakes to determine its ability to evaluate risk across multiple taxa and vectors. This case study included 67 aquatic species, identified as “watchlist species” in NOAA’s Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS). Vectors included shipping, hitchhiking/fouling, unauthorized intentional release, escape from recreational or commercial culture, and natural dispersal. We identified potential invaders from every continent but Africa and Antarctica. Of the 67 species, more than a fifth (21%) had a high potential for introduction and greater than 60% had a moderate potential for introduction. Shipping (72%) was the most common potential vector of introduction, followed by unauthorized intentional release (25%), hitchhiking/fouling (21%), dispersal (19%), stocking/planting/escape from recreational culture (13%), and escape from commercial culture. The ability to assess a variety of aquatic nonindigenous species from an array of potential vectors using a consistent methodology is essential for comparing likelihoods of introduction, establishment, and impact. The straightforward design of this framework will allow its application and modification according to policy priorities by natural resource managers. The ability to use a variety of information sources facilitates completion of assessments despite the paucity of data that often plagues aquatic nonindigenous species management

Understanding acceptable level of risk: Incorporating the economic cost of under-managing invasive species

Management of nonindigenous species includes prevention, early detection and rapid response and control. Early detection and rapid response depend on prioritizing and monitoring sites at risk for arrival or secondary spread of nonindigenous species. Such monitoring efforts require sufficient biosecurity budgets to be effective and meet management or policy directives for reduced risk of introduction. Such consideration of risk reduction is rarely considered, however. Here, we review the concepts of acceptable level of risk (ALOR) and associated costs with respect to nonindigenous species and present a framework for aligning risk reduction priorities with available biosecurity resources. We conclude that available biosecurity resources may be insufficient to attain stated and desired risk reduction. This outcome highlights the need to consider policy and management directives when beginning a biosecurity program to determine the feasibility of risk reduction goals, given available resources

The application of inelastic neutron scattering to investigate iron-based Fischer-Tropsch to olefins catalysis

Sasol Ltd., the University of Glasgow and EPSRC [award reference EP/P505534/1.] are thanked for the provision of postgraduate studentship (ALD). The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities [RB 1520269/1610413]. Diamond Light Source is thanked for time on B18 beamline through the Catalysis Hub BAG application (SP15151 and rapid access beamtime SP18431). The Royal Society is thanked for the provision of an Industry Fellowship (PBW).The technique of inelastic neutron scattering (INS) is used to investigate how hydrogen is partitioned within a series of Na and S promoted iron-based Fischer-Tropsch-to-olefin catalysts. Two reaction test regimes are examined. First, reaction testing at elevated temperature and pressure demonstrate how Na/S additions enhance short chain olefin selectivity and reduce methane formation under industrially relevant reaction conditions. For a fixed level of Na incorporation (2000 ppm), sulfur concentrations of ≤ 100 ppm result in only a modest improvement in olefin selectivity. However, for sulfur values of ≥ 100 ppm there is a noticeable and systematic increase in C2-C4 olefin selectivity; rising from ∼30.0 % to 35.2% at 250 ppm. Second, using ambient pressure CO hydrogenation as a test reaction in INS and micro-reactor configurations, catalyst samples are further analysed by TPR, TPO, XRD and S K-edge XANES. INS shows the formation of a hydrocarbonaceous overlayer to be significantly attenuated by the presence of the promoters, with increasing S levels significantly reducing the intensity of the sp2 and sp3 hybridised ν(C-H) modes of the overlayer, albeit to differing degrees. A probable role for how this combination of promoters is perturbing the form of the hydrocarbonaceous overlayer to subsequently moderate the product distribution is considered.Publisher PDFPeer reviewe

Classification of non-indigenous species based on their impacts: Considerations for application in marine management

Assessment of the ecological and economic/societal impacts of the introduction of non-indigenous species (NIS) is one of the primary focus areas of bioinvasion science in terrestrial and aquatic environments, and is considered essential to management. A classification system of NIS, based on the magnitude of their environmental impacts, was recently proposed to assist management. Here, we consider the potential application of this classification scheme to the marine environment, and offer a complementary framework focussing on value sets in order to explicitly address marine management concerns. Since existing data on marine NIS impacts are scarce and successful marine removals are rare, we propose that management of marine NIS adopt a precautionary approach, which not only would emphasise preventing new incursions through pre-border and at-border controls but also should influence the categorisation of impacts. The study of marine invasion impacts requires urgent attention and significant investment, since we lack the luxury of waiting for the knowledge base to be acquired before the window of opportunity closes for feasible management

The characterisation of hydrogen on nickel and cobalt catalysts

We have investigated a series of supported and unsupported nickel and cobalt catalysts, principally using neutron vibrational spectroscopy (inelastic neutron scattering, INS). For an alumina supported Ni catalyst we are able to detect hydrogen on the metal for the first time, all previous work has used Raney Ni. For an unsupported Ni foam catalyst, which has similar behaviour to Raney Ni but with a much lower density, the spectra show that there are approximately equal numbers of (100) and (111) sites, in contrast to Raney Ni that shows largely (111) sites. The observation of hydrogen on cobalt catalysts proved to be extremely challenging. In order to generate a cobalt metal surface, reduction in hydrogen at 250–300 °C is required. Lower temperatures result in a largely hydroxylated surface. The spectra show that on Raney Co (and probably also on a Co foam catalyst), hydrogen occupies a threefold hollow site, similar to that found on Co(101¯0). The reduced surface is highly reactive: transfers between cells in a high quality glovebox were sufficient to re-hydroxylate the surface.Publisher PDFPeer reviewe

LJETOPIS KULTURNIH ZBIVANJA U SPLITU

Fischer-Tropsch synthesis (FTS) is commonly viewed as an alternative approach to the production of diesel fuels via sources independent of crude oil. The adaptability of the FTS process allows for the selective production of shorter chain C2 to C6 hydrocarbons and has the potential to be a legitimate source of useable chemical feedstocks with high value to the chemical manufacturing industry. Interestingly, although recognised as a poison in most catalytic systems, small amounts of sulfur in iron-based FTS catalysts has been demonstrated to promote catalyst reducibility and activity towards shorter chain hydrocarbons. However, it is not known what impact sulfur has on the formation of hydrocarbonaceous surface species that have been proposed to play a pivotal role in the mediation of reactants during iron FTS. Here we apply ambient pressure CO hydrogenation at 623 K on a selection of sulfur promoted iron FTS catalysts to investigate the effect of sulfur content on hydrocarbonaceous species formation. For the first time, we report the application of inelastic neutron scattering to quantify the presence of hydrocarbonaceous species under the presence of sulfur promotion. In combination with temperature programmed oxidation, X-ray diffraction, and Raman spectroscopy, we observe how low sulfur loadings (<700 ppm) perturb carbon and hydrogen retention levels. The results indicate that the presence and nature of the hydrocarbonaceous overlayer is sensitive to sulfur loading, with the reported loss in catalytic activity at high loadings correlating with the attenuation of hydrocarbonaceous surface species

Studio Recital

Studio recital presenting the students of Charlotte Petersen. Featuring cellists and string ensembles.https://digitalcommons.usu.edu/music_programs/1124/thumbnail.jp