Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic(As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines(Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples(= 15%), and was primarily associated with iron(Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron–arsenic minerals, whereas in other samples, they were more consistent with As-rich iron(oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14 nm. The pore water samples only contained one size fraction of As-bearing colloids(around 6 nm diameter), while larger As-bearing colloids were only encountered in soil extracts. 相似文献
Mountain forest areas are key for providing a wide range of ecosystem services and are hot spots for land use change processes, in particular, increase in forest cover at the expense of mountain pastures and meadows. Mountain forest systems in eastern and western Europe have likely similar future socio-economic situations but significantly different socio-economic history. Using a scenario-based land use modelling approach (Dyna-CLUE framework) we model three scenarios (trend, liberalisation and self-sufficiency) of future land use in the Polish Carpathians and the Swiss Alps, focussing on forest cover change. We find that forest cover increase can be expected to continue in European mountainous regions under all likely scenarios, limited only by relatively strict policy interventions. Biophysical factors, rather than socio-economic ones, are key for defining the suitability for, and therefore likely locations of future forest cover, but land use legacy plays a very important role in the spatial patterns of future forest cover, particularly in eastern Europe.
DNA barcoding—sequencing a standard region of the mitochondrial cytochrome c oxidase 1 gene (COI)—promises a rapid, accurate means of identifying animals to a species level. This study establishes that
sequence variability in the barcode region permits discrimination of 98% of 201 fish species from the Canadian Pacific. The
average sequence variation within species was 0.25%, while the average distance separating species within genera was 3.75%.
The latter value was considerably lower than values reported in other studies, reflecting the dominance of the Canadian fauna
by members of the young and highly diverse genus Sebastes. Although most sebastids possessed distinctive COI sequences, four species did not. As a partial offset to these cases, the
barcode records indicated the presence of a new, broadly distributed species of Paraliparis and the possibility that Paraliparis pectoralis is actually a species pair. The present study shows that most fish species in Pacific Canadian waters correspond to a single,
tightly cohesive array of barcode sequences that are distinct from those of any other species, but also highlights some taxonomic
issues that need further investigation. 相似文献
The only available data set on the catches of global fisheries are the official landings reported annually by the Food and
Agriculture Organization of the United Nations (FAO). Attempts to detect and interpret trends in these data have been criticized
as being both technically and conceptually flawed. Here, we explore and refute these claims. We show explicitly that trends
in catch data are not an artifact of the applied method and are consistent with trends in biomass data of fully assessed stocks.
We also show that, while comprehensive stock assessments are the preferred method for evaluating single stocks, they are a
biased subsample of the stocks in a given area, strongly underestimating the percentage of collapsed stocks. We concur with
a recent assessment-based analysis by FAO that the increasing trends in the percentage of overexploited, depleted, and recovering
stocks and the decreasing trends in underexploited and moderately exploited stocks give cause for concern. We show that these
trends are much more pronounced if all available data are considered. 相似文献
Seit Oktober 2003 liegt der Verordnungsentwurf zur Neuordnung der europ?ischen Chemikalienpolitik vor. Aus ihm ergeben sich
zahlreiche, zum Teil neuartige Aufgaben für Hersteller und Importeure von Chemikalien, Zubereitungen und Erzeugnissen, für
nachgeschaltete Anwender und für den Handel. Die Landesregierung Nordrhein-Westfalen hat in einem Pilotprojekt Schlüsselelemente
des REACH-Systems in der Praxis erprobt. In dieser Ver?ffentlichung werden Erfahrungen aus dem Projekt aufgezeigt, die speziell
für die Textilveredlung wichtig sind. 相似文献
The selective introduction of compressive residual stresses is gaining increasing importance as design tool in today's manufacturing process chains. Manufacturing processes such as shot peening or hydraulic autofrettage are used to improve the surface integrity, and hence the fatigue life of the components. However, measuring the corresponding residual stress depth profiles is a challenging task as the results will always include the manufacturing and preparation history of the components. In this paper, results of residual stress measurements with X-ray diffraction and optical hole-drilling after autofrettage and sample preparation are presented and compared to a finite element analysis for two representative geometries. The presented approach can be used to predict the influence of the mandatory sample preparation procedure. As a consequence, the effectiveness of the manufacturing process to improve the surface integrity can be predicted more precisely and wrong interpretations of the measured residual stress depth profiles can be avoided. 相似文献
We studied the relative roles of environmental species sorting and priority effects in the assembly of ecological communities on long time scales, by analyzing community turnover of water fleas (Daphnia) in response to strong and recurrent environmental change in a fluctuating tropical lake. During the past 1800 years, Lake Naivasha (Kenya) repeatedly fluctuated between a small saline pond habitat during lowstands and a large freshwater lake habitat during highstands. Starting from a paleoecological reconstruction, we estimated the role of priority effects in Daphnia community assembly across 16 of these habitat turnovers and compared this with the response of the community to reconstructed changes in three environmental variables important for species sorting. Our results indicate that the best predictor of Daphnia community composition during highstands was the community composition just prior to the transition from lowstands to highstands. This reflects a long-lasting priority effect of late lowstand communities on highstand communities, arising when remnant lowstand populations fill newly available ecological space in the rapidly expanding lake habitat. Species sorting and priority effects had a comparable but relatively small influence on community composition during the lowstands. Moreover, these priority effects decayed rapidly with time as Daphnia communities responded to environmental change, in contrast with the highstand communities where priority effects lasted for several decades. 相似文献