A model study of dickite intercalated with formamide and N-methylformamide

Local geometry and orientation of intercalated molecules of formamide (FA) and N-methylformamide (NMFA) in the clay mineral dickite (D) was studied by means of Density Functional Theory (DFT) calculations. Ten configurations with different orientation of the intercalated molecule were investigated for both D_FA and D_NMFA intercalates. Four groups of relaxed structures sorted by the calculated total electronic energy were found in both cases. The experimental geometry of the D_FA intercalate was denoted as the most stable structure from the investigated models. The differences in the total electronic energy of all D_FA configurations are within the interval of ∼92 kJ/mol. On one hand FA forms intercalates specifically and a close relation between the orientation of the FA molecules in the interlayer space and the stability of a particular configuration has been observed. On the other hand, N-methylformamide forms intercalated structures non-specifically. Small differences in the total energy, not larger than 18 kJ/mol, are observed for different orientations of the NMFA molecules The reorientation of the intercalated molecules has only a small effect on the stabilization of the D_NMFA intercalate what is in contrast with the D_FA intercalate. It was also observed that the experimental D_NMFA configuration is not the most stable. A small variation of the total electronic energy of different configurations correlates with small changes of the orientation of the dipole moment of the intercalated NMFA molecule.     

An incentive mechanism for reducing emissions from conversion of intact and non-intact forests

This paper presents a new accounting mechanism in the context of the UNFCCC issue on reducing emissions from deforestation in developing countries, including technical options for determining baselines of forest conversions. This proposal builds on the recent scientific achievements related to the estimation of tropical deforestation rates and to the assessment of ‘intact’ forest areas. The distinction between ‘intact’ and ‘non intact’ forests used here arises from experience with satellite-based deforestation measurements and allows accounting for carbon losses from forest degradation. The proposed accounting system would use forest area conversion rates as input data. An optimal technical solution to set baselines would be to use historical average figures during the time period from 1990 to 2005. The system introduces two different schemes to account for preserved carbon: one for countries with high forest conversion rates where the desired outcome would be a reduction in their rates, and another for countries with low rates. A ‘global’ baseline rate would be used to discriminate between these two country categories (high and low rates). For the hypothetical accounting period 2013–2017 and considering 72% of the total tropical forest domain for which data are available, the scenario of a 10% reduction of the high rates and of the preservation of low rates would result in approximately 1.6 billion tCO₂ of avoided emissions. The resulting benefits of this reduction would be shared between those high-rate countries which reduced deforestation and those low-rate countries which did not increase their deforestation over an agreed threshold (e.g., half of “global” baseline rate).     

Influence of surface/groundwater interaction on pollution by pesticides in farmlands of the Fucino Plain,central Italy

This paper analyses flow and transport of pesticides from the unsaturated zone to groundwater so as to predict concentration of those contaminants in the Fucino Plain’s groundwater, by site investigations and numerical simulations. Pesticides were detected in surface water (peaks of 13 μg L⁻¹) and groundwater (peaks of 0.37 μg L⁻¹). Modelling tools made it possible to identify that pattern of precipitation, organic matter content, and root thickness are the key factors involved in vertical seepage of pesticides. Numerical simulations indicated that a significant fraction of contaminants is leached from the most surficial soil layers through runoff, while only a secondary fraction is mobilised towards groundwater. Likelihood of contaminating deep groundwater is fairly low, whereas surface waters show higher susceptibility. Results of the proposed conceptual hydrogeological model show that pesticides are more likely to be entrained by mixing of stream water with shallow groundwater in periods of high water exploitation from shallow wells.     

Experiments on the morphological controls of velocity inversions in bedrock canyons

A better understanding of bedrock incision mechanisms and processes is essential to the study of long‐term landscape evolution. Yet, little is known about flow dynamics in bedrock rivers, limiting our ability to make realistic predictions of local bedrock incision rates. A recent investigation of flow through bedrock canyons of the Fraser River revealed that plunging flows, defined by the downward‐directed movement of near surface flow toward the channel bed, occur in channels that have low width‐to‐depth ratios. Plunging flows occur into deep scour pools, which are often coincident with lateral constrictions and channel spanning submerged ridges (sills). A phenomenological investigation was undertaken to reproduce the flow fields observed in the Fraser canyons and to explore morphological controls on the occurrence and relative strength of plunging flow in bedrock canyons. Our observations show that the plunging flow structure can be produced along a scour pool entrance slope by accelerating the flow at the canyon entrance either over submerged sills or through lateral constrictions. Plunging flow appears to be a function of convective deceleration into a scour pool which can be enhanced by sill height, the amount of the channel width that is constricted, pool entrance slope, discharge, and a reduction in channel width‐to‐depth ratio. Plunging flow greatly enhances the potential for incision to occur along the channel bed and is an extreme departure from the assumptions of steady, uniform flow in bedrock incision models, highlighting the need for improved formulations that account for fluid flow. Copyright © 2017 John Wiley & Sons, Ltd.     

The border as an engine for mobility and spatial integration: A study of commuting in a Swedish–Norwegian context

The purpose of the study was to analyse how cross-border commuting differed from intranational commuting in Sweden, and how cross-border mobilities affected spatial integration. The authors analysed patterns and spatial flows of cross-border commuting by comparing them with characteristics of intranational commuting. In the article, they explore the assumption that the border constitutes an ‘engine’ for work-related mobility, which affects processes of spatial integration in cross-border areas. The empirical material comprised data from surveys of commuting from the Swedish county of Värmland to Norway and commuting within Värmland. The findings showed that cross-border commuting shared common features with intranational commuting, including how the frequency of commuting was dependent on distance. The motives for commuting differed, and the reasons for working in Norway were economic rather than professional. In terms of spatial integration, cross-border commuting was mainly one-directional, from Sweden to Norway, while leisure mobility and migration tended to be in the opposite direction. The authors conclude that the border region is characterised by integration through specialisation, which involves a permanent state of ‘transient’ mobility. Thus, a win-win situation can be distinguished, in which the border serves as a resource and an ‘engine’ for cross-border integration, mobility and economic activities.     

Monitoring 25 years of land cover change dynamics in Africa: A sample based remote sensing approach

The study examines the changes in sub-Saharan's natural land cover resources for a 25 year period. We assess these changes in four broad land cover classes – forests, natural non-forest vegetation, agriculture and barren – by using high spatial resolution Earth observing satellites. Two sets of sample images, one ‘historical’ targeted at 1975 and a second ‘recent’ targeted at the year 2000, have been selected through a stratified random sampling technique over the study area, targeting a sampling rate of 1% in each of the strata. The results, presented at eco-region level and aggregated at sub-Saharan level, show a 57% increase in agriculture area at the expense of natural vegetation which has itself decreased by 21% over the period, with nearly 5 million hectares forest and non-forest natural vegetation lost per year. The impacts of these changes on the environment on one site and on the socio-economy on the other site are discussed and possible pressures on human well being are highlighted.     

Interaction of wind and cold-season hydrologic processes on erosion from complex topography following wildfire in sagebrush steppe

Wildfire is a natural component of sagebrush (Artemisia spp.) steppe rangelands that induces temporal shifts in plant community physiognomy, ground surface conditions, and erosion rates. Fire alteration of the vegetation structure and ground cover in these ecosystems commonly amplifies soil losses by wind- and water-driven erosion. Much of the fire-related erosion research for sagebrush steppe has focused on either erosion by wind over gentle terrain or water-driven erosion under high-intensity rainfall on complex topography. However, many sagebrush rangelands are geographically positioned in snow-dominated uplands with complex terrain in which runoff and sediment delivery occur primarily in winter months associated with cold-season hydrology. Current understanding is limited regarding fire effects on the interaction of wind- and cold-season hydrologic-driven erosion processes for these ecosystems. In this study, we evaluated fire impacts on vegetation, ground cover, soils, and erosion across spatial scales at a snow-dominated mountainous sagebrush site over a 2-year period post-fire. Vegetation, ground cover, and soil conditions were assessed at various plot scales (8 m² to 3.42 ha) through standard field measures. Erosion was quantified through a network of silt fences (n = 24) spanning hillslope and side channel or swale areas, ranging from 0.003 to 3.42 ha in size. Sediment delivery at the watershed scale (129 ha) was assessed by suspended sediment samples of streamflow through a drop-box v-notch weir. Wildfire consumed nearly all above-ground live vegetation at the site and resulted in more than 60% bare ground (bare soil, ash, and rock) in the immediate post-fire period. Widespread wind-driven sediment loading of swales was observed over the first month post-fire and extensive snow drifts were formed in these swales each winter season during the study. In the first year, sediment yields from north- and south-facing aspects averaged 0.99–8.62 t ha⁻¹ at the short-hillslope scale (~0.004 ha), 0.02–1.65 t ha⁻¹ at the long-hillslope scale (0.02–0.46 ha), and 0.24–0.71 t ha⁻¹ at the swale scale (0.65–3.42 ha), and watershed scale sediment yield was 2.47 t ha⁻¹. By the second year post fire, foliar cover exceeded 120% across the site, but bare ground remained more than 60%. Sediment yield in the second year was greatly reduced across short- to long-hillslope scales (0.02–0.04 t ha⁻¹), but was similar to first-year measures for swale plots (0.24–0.61 t ha⁻¹) and at the watershed scale (3.05 t ha⁻¹). Nearly all the sediment collected across all spatial scales was delivered during runoff events associated with cold-season hydrologic processes, including rain-on-snow, rain-on-frozen soils, and snowmelt runoff. Approximately 85–99% of annual sediment collected across all silt fence plots each year was from swales. The high levels of sediment delivered across hillslope to watershed scales in this study are attributed to observed preferential loading of fine sediments into swale channels by aeolian processes in the immediate post-fire period and subsequent flushing of these sediments by runoff from cold-season hydrologic processes. Our results suggest that the interaction of aeolian and cold-season hydrologic-driven erosion processes is an important component for consideration in post-fire erosion assessment and prediction and can have profound implications for soil loss from these ecosystems. © 2019 John Wiley & Sons, Ltd.     

Declining impacts of hot spells on mortality in the Czech Republic, 1986–2009: adaptation to climate change?

The study examines temporal changes in mortality associated with spells of large positive temperature anomalies (hot spells) in extended summer season in the population of the Czech Republic (Central Europe) during 1986?C2009. Declining trends in the mortality impacts are found in spite of rising temperature trends. The finding remains unchanged if possible confounding effects of within-season acclimatization to heat and the mortality displacement effect are taken into account. Recent positive socioeconomic development, following the collapse of communism in Central and Eastern Europe in 1989, and better public awareness of heat-related risks are likely the primary causes of the declining vulnerability. The results suggest that climate change may have relatively little influence on heat-related deaths, since changes in other factors that affect vulnerability of the population are dominant instead of temperature trends. It is essential to better understand the observed nonstationarity of the temperature-mortality relationship and the role of adaptation and its limits, both physiological and technological, and to address associated uncertainties in studies dealing with climate change projections of temperature-related mortality.     

Radial distribution of lead and lead isotopes in stem wood of Norway spruce: A reliable archive of pollution trends in Central Europe

Annual growth rings of a common hardwood species, Picea abies L., were investigated as a potential archive of past atmospheric Pb pollution. Wide distribution of trees in terrestrial settings and straightforward chronology are two advantages of this potential geochemical archive, but several processes described in the literature may obscure the trends in past Pb deposition. These confounding factors include, e.g., radial post-depositional mobility of Pb in xylem, and ecosystem acidification leading to higher bioavailability of Pb. One- to five-year annual wood increments were analyzed for Pb concentrations and ²⁰⁶Pb/²⁰⁷Pb ratios at Jezeri (JEZ), Uhlirska (UHL) and Na Lizu (LIZ), three sites in the Czech Republic, differing in atmospheric Pb loads. Three to four trees per site were included in the study. Distinct Pb concentration maxima between 1960 and 1990 at the two heavily polluted sites (JEZ and UHL) coincided with historical Pb emissions known from inventories of industrial production. No Pb concentration maxima were found at one site, LIZ, situated in a national park 150 km from major pollution sources. Spruce tree rings from JEZ, located just 5 km from coal-burning power stations, contained a large proportion of coal-derived Pb (a high-²⁰⁶Pb/²⁰⁷Pb ratio of 1.19). A coal-related maximum in ²⁰⁶Pb/²⁰⁷Pb in JEZ tree rings was found using two different analytical techniques, laser-ablation multi-collector ICP MS, and single-collector sector-field ICP MS. In a three-isotope graph (²⁰⁶Pb/²⁰⁷Pb vs. ²⁰⁸Pb/²⁰⁷Pb), tree-ring data plotted into the field of ombrotrophic (i.e., rain-fed) peat bogs, suggesting negligible contribution of bedrock-derived Pb in the xylem. We concluded that none of the potential confounding factors played a major role at our sites. Annual growth rings of P. abies in Central Europe faithfully recorded historical changes in atmospheric Pb depositions.