Purpose This paper analyses Rwandan farmers’ perceptions of historical drivers of landscape vulnerability (past), current livelihood assets (present) and existing or potential capacities (future) to increase resilience to drought. The specific focus is on linking experiences from the past and present with ideas for a drought-resilient future. It explores how farmers' perceptions of past droughts and future visioning can contribute to rural development policy and multi-level collaborations. Design/methodology/approach This study was conducted in Bugesera, a drought-prone district in south-eastern Rwanda. Empirical data was collected through participatory observation, semi-structured interviews and focus groups. The analytical points of departure are based on sustainable landscapes and livelihood approaches, combining spatial and temporal perspectives on challenges and opportunities identified by farmers’ communities in addressing droughts. Findings All respondents had a high awareness of the impact of droughts. Perceived drivers of landscape change include historical climate events, such as droughts and floods, immigration and agricultural expansion, which have led to demographic pressure on land, deforestation and infringement on natural resources. Factors enhancing resilience capacities include access to diversified sources of livelihood, knowledge of appropriate irrigation techniques and availability of safety nets and credits. Furthermore, farmers identified collaborative opportunities as important for resilience capacity, including peer learning, and sharing best practices through knowledge exchange and on-field training. In addition, farmers brought up the need for innovative institutions that can facilitate access to markets and enable collaboration between different agricultural sectors. Originality/value This study analyses farmers’ perceptions of resilience capacities to droughts through a spatiotemporal lens of past droughts, present capital and future challenges by linking scales, knowledge and human–environment nexus. This paper contributes to the knowledge of climate adaptation in Rwanda and to discussions about smallholder farming in the literature on climate change adaptation.

The Ganga River exhibits elevated concentrations of dissolved strontium (Sr) and a higher radiogenic Sr (Sr-87/Sr-86) among global rivers, which impacts oceanic Sr composition. This has implications for understanding weathering and sediment flux into open oceans. The Nepal Himalayan section is a significant part of the upstream Ganga River catchment. We analyzed Sr and Nd isotopes and major element concentrations in water and sediments to trace compositional and seasonal variability in dissolved and particulate matter. The Sr and Nd isotopes, in particular, are crucial in this study as they provide unique signatures that can be used to trace the origin and composition of the dissolved and particulate matter. Representative rivers draining monolithological terrains were selected to investigate the isotopic and elemental provenance and weathering intensity. The elemental ratios (Ca/Na, Mg/Na) indicate the watersheds are carbonate-rich terrains. The Lesser Himalaya (LH) rivers transport radiogenic Sr with high values compared to rivers draining the Tethyan Sedimentary Series (TSS), Higher Himalayan Crystalline (HHC), Mahabharat, and Siwalik Hills. The dry season records a higher Sr-87/Sr-86 ratio than the monsoon. Due to the faster dissolution of carbonates compared to silicates, monsoon waters transport less radiogenic Sr. The significant correlation of Sr-87/Sr-86 in dissolved and particulate phases signifies that short-term interactions between sediment and water may alter the Sr-87/Sr-86 composition. Notably, sediments originating from continental rocks exhibit an inverse correlation between Sr-87/Sr-86 and epsilon(Nd). In conclusion, the Sr and Nd isotopic records in this study categorize the fluvial catchments into geological clusters aligned with the TSS, LH, and Siwaliks, which advance our understanding regarding the provenance besides providing crucial insights into geological processes, weathering, landscape evolution, and sediment flux.

This article analyses the success and failure factors underlying smallholder farmers' resilience to drought in Sub-Saharan Africa based on a literature review of the period 2007-19. The analysis is guided by transformation theory, which states that transformation requires adequate preconditions in three spheres: practical, political and personal. While significant progress has occurred in the practical sphere, only moderate change characterizes the political sphere, and the most limited progress is within the personal sphere. We argue that increasing drought resilience requires innovative solutions, including components from all transformation spheres. Interactions with local stakeholders and the empowerment of smallholder farmers are essential.

Understanding fluid rheology is important for optimal design and operation of continuous stirred-tank biogas reactors (CSTBRs) and is the basis for power requirement estimates. Conflicting results have been reported regarding the applicability of total solid (TS) and/or total volatile solid (TVS) contents of CSTBR fluids as proxies for rheological properties. Thus, the present study investigates relationships between rheological properties of 12 full-scale CSTBR fluids, their substrate profiles, and major operational conditions, including pH, TS and TVS contents, organic loading rate, hydraulic retention time, and temperature. Rheology-driven power requirements based on various fluid characteristics were evaluated for a general biogas reactor setup. The results revealed a significant correlation only between the rheological fluid properties and TS or TVS contents for sewage sludge digesters and thermophilic co-digesters (CD), but not for mesophilic CD. Furthermore, the calculated power requirements for pumping and mixing, based on the various fluid characteristics of the studied CSTBRs, varied broadly irrespective of TS and TVS contents. Thus, this study shows that the TS and/or TVS contents of digester fluid are not reliable estimators of the rheological properties in CSTBRs digesting substrates other than sewage sludge.

Sediments underlying hypoxic or anoxic water bodies constitute a net source of phosphorus to the bottom water. This source has the potential to enhance eutrophication. Benthic fluxes of dissolved p ...

In the present study, we investigated how sediment fluxes of dissolved silica (DSi) and dissolved inorganic phosphorus (DIP) were affected by dissolved oxygen (DO) availability in bottom waters. Sediments from two sites in the Baltic proper were incubated under changing oxygen conditions. Our results show that when DO availability decreased from oxic to hypoxic level, the average DSi fluxes decreased significantly at the two sites from 2.12 +/- 0.04 to 0.87 +/- 0.18 and from 2.37 +/- 0.09 to 1.91 +/- 0.55 mmol Si m(-2) d(-1), respectively. Average DIP fluxes increased significantly at one site from 0.06 +/- 0.01 to 0.14 +/- 0.02 mmol P m(-2) d(-1), but not at the other (from 0.06 +/- 0.01 to 0.07 +/- 0.01 mmol P m(-2) d(-1)). These results indicate that a change from highly oxic to hypoxic conditions in bottom waters may decrease DSi fluxes and increase DIP fluxes. However, sediment characteristics can lead to spatial differences in the response of DSi and DI Pfluxes to oxygen availabilit.

This article deals with the interrelationship between overall chemical speciation of S, Fe, Co, and Ni in relation to metals bio-uptake processes in continuous stirred tank biogas reactors (CSTBR). To address this topic, laboratory CSTBRs digesting sulfur(S)-rich stillage, as well as full-scale CSTBRs treating sewage sludge and various combinations of organic wastes, termed co-digestion, were targeted. Sulfur speciation was evaluated using acid volatile sulfide extraction and X-ray absorption spectroscopy. Metal speciation was evaluated by chemical fractionation, kinetic and thermodynamic analyses. Relative Fe to S content is identified as a critical factor for chemical speciation and bio-uptake of metals. In reactors treating sewage sludge, quantity of Fe exceeds that of S, inducing Fe-dominated conditions, while sulfide dominates in laboratory and co-digestion reactors due to an excess of S over Fe. Under sulfide-dominated conditions, metals availability for microorganisms is restricted due to formation of metal-sulfide precipitates. However, aqueous concentrations of different Co and Ni species were shown to be sufficient to support metal acquisition by microorganisms under sulfidic conditions. Concentrations of free metal ions and labile metal complexes in aqueous phase, which directly participate in bio-uptake processes, are higher under Fe-dominated conditions. This in turn enhances metal adsorption on cell surfaces and bio-uptake rates.

Natural chlorination of organic matter is common in soils. The abundance of chlorinated organic compounds frequently exceeds chloride in surface soils, and the ability to chlorinate soil organic matter (SOM) appears widespread among microorganisms. Yet, the environmental control of chlorination is unclear. Laboratory incubations with 36Cl as a Cl tracer were performed to test how combinations of environmental factors, including levels of soil moisture, nitrate, chloride, and labile organic carbon, influenced chlorination of SOM from a boreal forest. Total chlorination was hampered by addition of nitrate or by nitrate in combination with water but enhanced by addition of chloride or most additions including labile organic matter (glucose and maltose). The greatest chlorination was observed after 15 days when nitrate and water were added together with labile organic matter. The effect that labile organic matter strongly stimulated the chlorination rates was confirmed by a second independent experiment showing higher stimulation at increased availability of labile organic matter. Our results highlight cause-effect links between chlorination and the studied environmental variables in podsol soil-with consistent stimulation by labile organic matter that did overrule the negative effects of nitrate.

Students’ problems with learning science in school are well documented. Earlier studies report on differences in students’ interest in and attitudes towards science due to gender and age. However, fewer studies have focused on relations with experience and recruitment on a detailed content level. Present paper presents a statistical analysis of student interest in specific content areas and combines this with student experience of science and science-related activities outside school. The result shows that patterns of interest and experience can be identified. These patterns showed differences in gender and also relate to student preferences of upper secondary education. The results are presented on both a detailed content and an experience level. The results are discussed in relation to the purpose of compulsory science education. The study contributes to the discussion about a more relevant science education by presenting concrete content and experience dimensions from a student perspective.

Lakes are major sources of methane (CH 4 ) to the atmosphere that contribute significantly to the global budget. Recent studies have shown that diffusive fluxes, ebullition and surface water CH 4 concentrations can differ significantly within lakes—spatially and temporally. CH 4 fluxes may be affected at longer scales in response to seasons, temperature, lake mixing events, short term weather events like pressure variations, shifting winds and diel cycles. Frequent measurements of fluxes in the same system and integrated assessments of the impacts of the spatio‐temporal variability are rare. Thereby, large scale assessments frequently lack information on this variability which can potentially lead to biased estimates. In this study, we analysed the variability of CH 4 fluxes and surface water CH 4 concentrations across open water areas of lakes in a small catchment in southwest Sweden over two annual cycles. Significant patterns in CH 4 concentrations, diffusive fluxes, ebullition and total fluxes were observed in space (between and within lakes) and in time (over diel cycles to years). Differences observed among the lakes can be associated with lake characteristics. The spatial variability within lakes was linked to depth or distance to stream inlets. Temporal variability was observed at diel to seasonal scales and was influenced by weather events. The fluxes increased exponentially with temperature in all three lakes, with stronger temperature dependence with decreasing depth. By comparing subsets of our data with estimates using all data we show that considering the spatio‐temporal variability in CH 4 fluxes is critical when making whole lake or annual budgets.

Ombrotrophic raised bogs are nutrient poor acidic peatlands accumulating organic matter. They are widely spread on northern latitudes and are substantial sources of methane emissions to the atmosphere being of great concern from a climate change perspective. We investigated the methanogen community composition along microtopographic gradients within three bogs in Scandinavia, receiving different amounts of nitrogen precipitation. Methanogenic community analyses by terminal restriction fragment length polymorphism of the mcrA gene showed different profiles among the three sites, while no influence of the rnicrotopographic gradients was observed. Peat temperature and dissolved organic carbon were the major edaphic variables explaining 38% of the variation of the methanogenic community diversity among the bogs. The family Methanoregulaceae (hydrogenotrophic methanogens) showed the largest relative proportion and highest activity in all three sites. Quantitative PCR of the mcrA gene and transcripts showed that the most northern site, receiving the lowest atmospheric nitrogen load, had significantly lower abundance and activity of methanogens (4.7 x 10(6) and 2.4 x 10(4) mcrA copies per gram of soil, respectively), compared to the most southern site (8.2 x 10(7) and 4.6 x 10(5) mcrA copies per gram of soil, respectively), receiving the highest nitrogen load. No patterns of the mcrA gene and transcript abundances were observed along the microtopography. The results indicated that the difference in occurrence of methanogens is mainly due to geoclirnatological conditions rather than site intrinsic microtopographic variation. The study further suggests that environmental changes on the site intrinsic topography will not affect the methanogenic activity, while increasing average temperatures in Scandinavian ombrotrophic raised bogs might contribute to an increase of the methanogenic archaeal activity resulting in an increase of methane production. (C) 2014 Elsevier Ltd. All rights reserved.

This paper reports on Swedish results from a worldwide research project concerned with the Interest and Recruitment in Science Education (the IRIS-International study) together with results from a longitudinal national study on girl's views on out of school experience in science and technology in upper secondary education. The studies are framed in the structural situation of the Swedish educational system. The results show that there are reform and policy effects to consider in the discussion of recruiting more students in STEM. Interest in the subject, earlier school experience, achievement and teacher feedback is found to be important for educational choice in STEM. Specifically girls point out societal relevance as important. In addition there are elements outside the school setting with importance for educational choice. Moreover, girls point out visits to a museum and watching films and boys popularized forms of science and computer games. All students consider TV and activities outside school as important for their educational choice in STEM. When trying to implement outside school experience with girls in a longitudinal study in upper secondary education the interplay with school subject teaching is identified as missing. The friction between subject teaching in schools and connections with the surrounding world is proposed as important for future studies.

A common way of quantifying and communicating climate vulnerability is to calculate composite indices from indicators, visualizing these as maps. Inherent methodological uncertainties in vulnerability assessments, however, require greater attention. This study examines Swedish agricultural vulnerability to climate change, the aim being to review various indicator approaches for assessing agricultural vulnerability to climate change and to evaluate differences in climate vulnerability depending on the weighting and summarizing methods. The reviewed methods are evaluated by being tested at the municipal level. Three weighting and summarizing methods, representative of climate vulnerability indices in general, are analysed. The results indicate that 34 of 36 method combinations differ significantly from each other. We argue that representing agricultural vulnerability in a single composite index might be insufficient to guide climate adaptation. We emphasize the need for further research into how to measure and visualize agricultural vulnerability and into how to communicate uncertainties in both data and methods.

The effects of sulfide removal by addition of Fe on chemical speciation of Co and Ni and how it may affect the microbial metal uptake processes in biogas reactors were assessed. The influent Fe con ...

Silica (Si) is a key nutrient for diatoms. Over the last century, Si concentrations within the Baltic Sea decreased significantly. This is mainly attributed to ongoing eutrophication, increased production and subsequent deposition and accumulation of organic matter including biogenic silica. As a consequence of the eutrophication, hypoxic and anoxic bottom waters have spread affecting nutrient cycling. This paper looks at the potential impact of oxygen on dissolved silica (DSi). It presents a statistical analysis of the relationship between DSi concentrations and oxygen conditions (O-2) in the deep water of the Baltic Proper. The idea is not new, but this is the first time it is studied in more detail in this area. Regression analysis shows that DSi concentrations decrease significantly with O-2 concentrations, and that the major intrusion of saline water in 1993 strengthened this relationship. Increased hypoxia will significantly affect the cycling of Si in the Baltic Sea.