Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

© 2017 Elsevier Ltd Rapid compression machines (RCMs) are widely used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by low- to intermediate-temperatures (600–1200 K) and moderate to high pressures (5–80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challenges for studying this regime include that experimental observations can be more sensitive to coupled physical-chemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physical-chemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady imp rovement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. Emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics

Twelve recommendations for advancing marine conservation in European and contiguous seas

Like most ocean regions today, the European and contiguous seas experience cumulative impacts from local human activities and global pressures. They are largely in poor environmental condition with deteriorating trends. Despite several success stories, European policies for marine conservation fall short of being effective. Acknowledging the challenges for marine conservation, a 4-year multi-national network, MarCons, supported collaborative marine conservation efforts to bridge the gap between science, management and policy, aiming to contribute in reversing present negative trends. By consolidating a large network of more than 100 scientists from 26 countries, and conducting a series of workshops over 4 years (2016–2020), MarCons analyzed challenges, opportunities and obstacles for advancing marine conservation in the European and contiguous seas. Here, we synthesize the major issues that emerged from this analysis and make 12 key recommendations for policy makers, marine managers, and researchers. To increase the effectiveness of marine conservation planning, we recommend (1) designing coherent networks of marine protected areas (MPAs) in the framework of marine spatial planning (MSP) and applying systematic conservation planning principles, including re-evaluation of existing management zones, (2) designing MPA networks within a broader transboundary planning framework, and (3) implementing integrated land-freshwater-sea approaches. To address inadequate or poorly informed management, we recommend (4) developing and implementing adaptive management plans in all sites of the Natura 2000 European conservation network and revising the Natura 2000 framework, (5) embedding and implementing cumulative effects assessments into a risk management process and making them operational, and (6) promoting actions to reach ‘good environmental status’ in all European waters. To account for global change in conservation planning and management, we further recommend (7) developing conservation strategies to address the impacts of global change, for example identifying climate-change refugia as high priority conservation areas, and (8) incorporating biological invasions in conservation plans and prioritizing management actions to control invasive species. Finally, to improve current practices that may compromise the effectiveness of conservation actions, we recommend (9) reinforcing the collection of high-quality open-access data, (10) improving mechanisms for public participation in MPA planning and management, (11) prioritizing conservation goals in full collaboration with stakeholders, and (12) addressing gender inequality in marine sciences and conservation

Algal mats transport diaspores and carpological remains in shallow lakes

Algal mats in lakes and reservoirs can transport diaspores and carpological remains of plants, and thus may influence the creation of taphocoenoses. In 2012, I quantified carpological remains in two types of algal mats from a small reservoir in southern Poland. Mats formed by filamentous algae participate primarily in the original transport of diaspores, and can influence their concentration and facilitate their migration, mainly between the shores of the reservoir. Diatom mats partake primarily in diaspore redeposition, but can also cause their dispersal between the shore zone and the central part of the reservoir. This research demonstrates that mats built by diatoms contain far more remains and are more biologically diverse than filamentous algal mats. Movement of carpological remains observed in both types of algal mats points to their role in the formation of taphocoenoses and suggests that algal mats must be considered when interpreting macrofossil records

Nitrogen Transformation and Fate in Prairie Wetlands

Agricultural applications of fertilizers and pesticides have increased dramatically in the prairie pothole region since the middle 1960s, and agrochemical contamination of surface and groundwater has become a serious environmental concern. There is growing interest in the potential of prairie wetlands as sinks for excess nutrients in this agricultural landscape. As much as 50% of the fertilizer nitrogen applied to cultivated crops may be lost as nitrate in agricultural drainage water, and prairie wetlands may be especially effective as nitrate sinks. The effectiveness of prairie wetlands as sinks for nonpoint source nitrogen loads is likely to depend on the magnitude of nitrate loads and the capacity of the wetlands to remove nitrate by dissimilatory processes. Performance forecast models are needed to evaluate the effectiveness of prairie wetlands as nitrogen sinks from a watershed scale framework. This will be made significantly more difficult by the spatial and temporal complexity of prairie pothole wetlands and by their hydrologic diversity. Future research should focus on identifying the principal factors controlling nitrogen transformation in prairie wetlands and on developing general predictive tools for modeling nitrogen fate in these systems

Distribution and Environmental Fate of Pesticides in Prairie Wetlands

There is abundant, albeit fragmentary, evidence that prairie wetlands are being contaminated extensively by agricultural pesticides (primarily herbicides and insecticides) and other anthropogenic contaminants. Such inputs can affect fundamental ecosystem properties such as primary production which, in turn, affects habitat and resource supply for wetland fauna. We review data on the use of pesticides, off-site transport of residues from treated land, and the frequency with which these residues are subsequently detected in receiving streams and wetlands on the prairies. As the environmental distribution of a pesticide is affected by its chemical and physical properties, and the abiotic and biotic characteristics of the receiving wetland, greater insight into its ecological impacts will be obtained from considering the underlying partitioning and degradative processes that determine distribution rather than from case-by-case studies of persistence. Future research on chemical contamination of prairie wetlands should include the development and testing of dissipation and fate models under conditions typical of prairie wetlands using a process-oriented approach, emphasizing the roles of adsorption and photolysis in a shallow, high area to volume environment. Output from a computer model based on the fugacity concept (QWASFI: Quantitative Water, Air, Soil, Film Interactions) indicates the potential to predict the environmental behavior of specific chemicals in wetlands