Neutralization/prevention of acid rock drainage using mixtures of alkaline by-products and sulfidic mine wastes

Backfilling of open pit with sulfidic waste rock followed by inundation is a common method for reducing sulfide oxidation after mine closure. This approach can be complemented by mixing the waste rock with alkaline materials from pulp and steel mills to increase the system’s neutralization potential. Leachates from 1 m³ tanks containing sulfide-rich (ca.30 wt %) waste rock formed under dry and water saturated conditions under laboratory conditions were characterized and compared to those formed from mixtures. The waste rock leachate produced an acidic leachate (pH?<?2) with high concentrations of As (65 mg/L), Cu (6 mg/L), and Zn (150 mg/L) after 258 days. The leachate from water-saturated waste rock had lower concentrations of As and Cu (<2 μg/L), Pb and Zn (20 μg/L and 5 mg/L), respectively, and its pH was around 6. Crushed (<6 mm) waste rock mixed with different fractions (1–5 wt %) of green liquid dregs, fly ash, mesa lime, and argon oxygen decarburization (AOD) slag was leached on a small scale for 65 day, and showed near-neutral pH values, except for mixtures of waste rock with AOD slag and fly ash (5 % w/w) which were more basic (pH?>?9). The decrease of elemental concentration in the leachate was most pronounced for Pb and Zn, while Al and S were relatively high. Overall, the results obtained were promising and suggest that alkaline by-products could be useful additives for minimizing ARD formation.     

Background levels of some major,trace, and rare earth elements in indigenous plant species growing in Norway and the influence of soil acidification,soil parent material,and seasonal variation on these levels

Baseline levels of 43 elements, including major, trace, and rare earth elements (REEs) in several native plant species growing in boreal and alpine areas, are presented. Focus is placed on species metal levels at different soil conditions, temporal variations in plant tissue metal concentrations, and interspecies variation in metal concentrations. Vegetation samples were collected at Sogndal, a pristine site in western Norway, and at Risdalsheia, an acidified site in southernmost Norway. Metal concentrations in the different species sampled in western Norway are compared with relevant literature data from Norway, Finland, and northwest Russia, assumed to represent natural conditions. Except for aluminium (Al) and macronutrients, the levels of metals were generally lower in western Norway than in southern Norway and may be considered close to natural background levels. In southern Norway, the levels of cadmium (Cd) and lead (Pb) in particular appear to be affected by air pollution, either by direct atmospheric supply or through soil acidification. Levels of some elements show considerable variability between as well as within plant species. Calcium (Ca), magnesium (Mg), and potassium (K) are higher in most species at Sogndal compared to Risdalsheia, despite increased extractable concentrations in surface soil in the south, probably attributed to different buffer mechanisms in surface soil. Antagonism on plant uptake is suggested between Ca, Mg, and K on one hand and Al on the other. Tolerance among calcifuges to acid conditions and a particular ability to detoxify or avoid uptake of Al ions are noticeable for Vaccinium vitis-idaea.     

Complications with using ratios for environmental data: comparing enantiomeric ratios (ERs) and enantiomer fractions (EFs)

Complications arise when ratios are used to present environmental data because ratios are an unbounded, multiplicative scale that can lead to asymmetrical (skewed) data distributions. Enantiomeric ratios (ERs), historically used in discussions of chiral signatures, often are published as mean ER+/-single-value standard deviation. Application of statistical summaries, such as the widely used sample mean and standard deviation, to skewed ratio data is misleading and often inappropriate. Comparison of statistically summarized ER and enantiomer fraction (EF) data (which are based on a bounded, additive scale) for a range of hypothetical values reveals substantial discrepancies when conversion between ER and EF formats is used. These discrepancies are largest when the ratio data are greater than one and have large variability, because the data are more skewed. In many cases, the use of fractions instead of ratios can help to minimize misrepresentation of environmental data, including chiral data. The use of nonparametric statistical summaries, e.g., median and percentiles, provides a more robust indicator of the typical value and spread for both ER and EF data.     

Territory and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?

According to current theories of territoriality, an animal is expected to defend the smallest area that can provide resources for maximisation of reproduction, known as the economically defendable area. In group territorial species however, the strategies behind resource defence are likely to be more complex with corporate territoriality, cooperative breeding, delayed dispersal and intra-group competition all potentially playing a role. Here we examined group territoriality in a social herbivorous rodent, the Eurasian beaver Castor fiber. Beavers in our study do not inhabit economically defendable territories. Instead the sequence of arrival of pairs into unoccupied areas seems to play a more important role in determining the size of the territory, whereas group size is determined by past reproductive success. We argue that the settlement pattern and reproductive history have a lasting impact in the territorial system of beavers due to a combination of the low adult mortality, high dispersal costs, and avoidance of resource depletion.R.D. Campbell and F. Rosell contributed equally to this work     

Entrepreneurship in climate governance at the local and regional levels: concepts,methods, patterns,and effects

This editorial sets the scene for a special issue on climate governance entrepreneurship at the local and regional levels. To make climate governance work, much policy activity is needed at the local and regional levels. Entrepreneurs are actors who aim to affect change by using their agency. They target policy decisions at the local and regional levels, which might subsequently turn to other governance levels to expand their influence. The scientific discussion about governance entrepreneurs is characterized by a lack of conceptual clarity, by methodological challenges, and by several research gaps. Regarding the latter, at present, it is especially unclear when and why entrepreneurs become active, which factors they take into account when they select their strategies, and what explains the effects of entrepreneurial activity on the emergence of innovations in climate governance. All contributions to this special issue engage with one or several of these conceptual, methodological, and empirical challenges, thus advancing the state of art in the field. Highlights from the special issue include the development of a simple conceptual frame that connects actors, contexts, strategies, and outcomes in a systematic way. Some promising methodological avenues are described, since the special issue contains not only some qualitative case studies but also some studies that take a long-term perspective by following policy development for decades, and a study that proposes a census approach. Empirically, the contributions in this special issue shed light on a range of factors explaining levels of entrepreneurial activity, and they carefully trace impacts over time. We conclude by sketching an agenda for further work in this realm.

     

Non-consumptive effects of predator presence on copepod reproduction: insights from a mesocosm experiment

Reproduction in planktonic animals depends on numerous biotic and abiotic factors. One of them is predation pressure, which can have both direct consumptive effects on population density and sex ratio, and non-consumptive effects, for example on mating and migration behaviour. In copepods, predator vulnerability depends on their sex, motility pattern and mating behaviour. Therefore, copepods can be affected at multiple stages during the mating process. We investigated the reproductive dynamics of the estuarine copepod Eurytemora affinis in the presence and absence of its predator the mysid Neomysis integer in a mesocosm experiment. We found that the proportion of ovigerous females decreased in the presence of predators. This shift was not caused by differential predation as the absolute number of females was unaffected by mysid presence. Presence of predators reduced the ratio of males to non-ovigerous females, but not by predation of males. Our combined results suggest that the shift from ovigerous to non-ovigerous females under the presence of predators was caused by either actively delayed egg production or by shedding of egg sacs. Nauplii production was initially suppressed in the predation treatment, but increased towards the end of the experiment. The proportion of fertilized females was similar in both treatments, but constantly fell behind model predictions using a random mating model. Our results highlight the importance of non-consumptive effects of predators on copepod reproduction and hence on population dynamics.     

Kinetics of the extraction of pyrene using carbon dioxide in dense phase

Bath extraction experiments of pyrene from two spiked soils with different textural composition (sandy, sandy-clay) were performed with near-critical and supercritical CO(2) at different pressures (7.5, 15, 20, 25 MPa) and temperatures (40, 50, 60 degrees C) in order to obtain mass transfer rate data. An empirical equation whose parameters depend on type of soil but are independent of pressure and temperature is proposed. The comparison between individual mass transfer coefficients shows that the extraction is controlled by the resistance within the particle. Effective diffusivities between 0.4 and 6.0 x 10(-10) m(2)/s are deduced.     

Protein futures for Western Europe: potential land use and climate impacts in 2050

Multiple production and demand side measures are needed to improve food system sustainability. This study quantified the theoretical minimum agricultural land requirements to supply Western Europe with food in 2050 from its own land base, together with GHG emissions arising. Assuming that crop yield gaps in agriculture are closed, livestock production efficiencies increased and waste at all stages reduced, a range of food consumption scenarios were modelled each based on different ‘protein futures’. The scenarios were as follows: intensive and efficient livestock production using today’s species mix; intensive efficient poultry–dairy production; intensive efficient aquaculture–dairy; artificial meat and dairy; livestock on ‘ecological leftovers’ (livestock reared only on land unsuited to cropping, agricultural residues and food waste, with consumption capped at that level of availability); and a ‘plant-based eating’ scenario. For each scenario, ‘projected diet’ and ‘healthy diet’ variants were modelled. Finally, we quantified the theoretical maximum carbon sequestration potential from afforestation of spared agricultural land. Results indicate that land use could be cut by 14–86 % and GHG emissions reduced by up to approximately 90 %. The yearly carbon storage potential arising from spared agricultural land ranged from 90 to 700 Mt CO₂ in 2050. The artificial meat and plant-based scenarios achieved the greatest land use and GHG reductions and the greatest carbon sequestration potential. The ‘ecological leftover’ scenario required the least cropland as compared with the other meat-containing scenarios, but all available pasture was used, and GHG emissions were higher if meat consumption was not capped at healthy levels.