66,693 research outputs found
Fluvial contributions of nutrient salts, dissolved trace elements and organic carbon to the sea by pristine temperate rivers (SW Europe).
No full textBernárdez, P., Ospina-Alvarez, N., Caetano, M., & Prego, R. (2013). Fluvial contributions of nutrient salts, dissolved trace elements and organic carbon to the sea by pristine temperate rivers (SW Europe). Environmental Chemistry, 10(1), 42–53. doi:http://dx.doi.org/10.1071/EN1212
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Channel adjustments in Iranian rivers: A review
No full textChannel adjustments in Iranian rivers have been intense over the last decades due to
natural and human factors. Iran has six major basins, all with dierent climates, from very humid
to very arid. This work is a review of the available studies and data about channel adjustments in
Iranian rivers, and aims to reconstruct a first outline, at a national scale, of types, magnitude, and
causes of adjustments. The results show that most of the rivers have undergone incision (1 to 2 m
and, in some cases, up to 6 to 7 m) and narrowing (from 19% to 73%), although widening (from 22%
to 349%) has occurred in some rivers. Narrowing is due to dams and sediment mining; widening
is due to climate change and sediment mining. Incision is due to gravel and sand mining, dams,
channelization, with in-channel mining being the main cause of incision. Channel adjustments have
occurred in basins with dierent climates, but it seems that widening has been more intense in arid
and semi-arid climates. Such adjustments have several negative eects (e.g., damage to bridges,
degradation of river ecosystems, and instability of banks). The comparison between Iran and other
countries shows that narrowing and incision have been the dominant processes in most of the rivers,
while damming and in-channel mining have been used as the main controlling factors. Data about
adjustments in Iranian rivers are neither homogeneous nor complete for all the rivers. This lack
of completeness implies that our understanding of channel changes, and their causes, should be
improved by further investigation
Nutrients Export by Rivers to the Coastal Waters of Africa: Past and Future trends
No full textWe analyze past and future trends in nitrogen (N), phosphorus (P), and carbon (C) export by rivers to the coastal waters of Africa as calculated by the Global Nutrient Export to WaterShed (NEWS) models for the period 1970–2050. Between 1970 and 2000 the total nutrient export by African rivers increased by 10–80%. For future years (2000–2050) we calculate an increase in the total loads of dissolved forms of N and P, but decreasing trends for dissolved organic C and particulate forms of N and P. There are large regions that deviate from these pan-African trends. We explore the regional patterns and the underlying processes, in particular for the Nile, Zaire, Niger, and Zambezi. In the future, anthropogenic sources may, in large parts of Africa, become larger contributors to riverine nutrient loads than natural source
Organic carbon transport and C/N ratio variations in a large tropical river: Godavari as a case study, India
No full textThis study gives an insight into the source of organic carbon and nitrogen in the Godavari river and its tributaries, the yield of organic carbon from the catchment, seasonal variability in their concentration and the ultimate flux of organic and inorganic carbon into the Bay of Bengal. Particulate organic carbon/particulate organic nitrogen (POC/PON or C/N) ratios revealed that the dominant source of organic matter in the high season is from the soil (C/N = 8–14), while in the rest of the seasons, the river-derived (in situ) phytoplankton is the major source (C/N = l–8). Amount of organic materials carried from the lower catchment and flood plains to the oceans during the high season are 3 to 91 times higher than in the moderate and low seasons. Large-scale erosion and deforestation in the catchment has led to higher net yield of organic carbon in the Godavari catchment when compared to other major world rivers. The total flux of POC, and dissolved inorganic carbon (DIC) from the Godavari river to the Bay of Bengal is estimated as 756 · 109 and 2520 · 109 g yr1, respectively. About 22% of POC is lost in the main channel because of oxidation of labile organic matter, entrapment of organic material behind dams/sedimentation along flood plains and river channel; the DIC fluxes as a function of alkalinity are conservative throughout the river channel. Finally, the C/N ratios (12) of the ultimate fluxes of particulate organic carbon suggest the dominance of refractory/ stable soil organic matter that could eventually get buried in the coastal sediments on a geological time scale
Phytoplankton dynamics of the feeder rivers of the Humber estuary
No full textThe effect of environmental conditions upon the growth, production and development of river phytoplankton was investigated for the feeder rivers to the Humber Estuary. The study was part of the Land Ocean Interaction Study LOIS) and focused upon the Rivers Trent and Yorkshire Ouse. The influence of physical, chemical and biological factors upon phytoplankton development were measured through routine fieldwork and laboratory analyses. During fieldwork measurements were collected which complemented measurements collected by LOIS colleagues. Data collected in this study included phytoplankton species composition, density and biomass and is situ rates of growth and production. In situ rates of loss through grazing and respiration were also measured. Laboratory investigations concentrated upon the effects of Ught and temperature upon dominant phytoplankton species and were developed to complement fieldwork. The project focused around four main aims. These were basically to assess the size and composition of phytoplankton maxima in the Trent and Ouse, measure in situ rates of growth and production, estimate losses from grazing and to develop models, using the data collected to assess the effect of environmental conditions upon phytoplankton development and autochthonous carbon in the Humber Estuary. The results showed that phytoplankton dynamics in the Trent and Ouse were controlled primarily by discharge, light and temperature. During spring, when conditions were favourable for growth, rapid phytoplankton growth and maximum rates of production were observed. However, spring floods often interrupted die large phytoplankton populations which developed. Other factors such as grazing and sedimentation were also considered as potentially important in the loss of phytoplankton. The turbid nature of the rivers resulted in a fine balance between photosynflietic gain and respirational loss. This temporal change in environmental conditions resulted in a temporal waxing and waning of the phytoplankton. This in turn had an impact upon the seasonality of the flux of autochthonous carbon to the Humber Estuary. Laboratory investigations and development of a photosynthetic model confirmed the importance of light and temperature upon phytoplankton development in these rivers. In terms of phytoplankton growth and production and the flux of autochthonous carbon, the Trent and Ouse were found to be typical of many other European rivers. The study highlighted the importance of the Trent as a source of autochthonous carbon to the Humber Estuary
Summer CO2 evasion from streams and rivers in the Kolyma River basin, north-east Siberia
No full textInland water systems are generally supersaturated in carbon dioxide (CO2) and are increasingly recognized as playing an important role in the global carbon cycle. The Arctic may be particularly important in this respect, given the abundance of inland waters and carbon contained in Arctic soils; however, a lack of trace gas measurements from small streams in the Arctic currently limits this understanding.We investigated the spatial variability of CO2 evasion during the summer low-flow period from streams and rivers in the northern portion of the Kolyma River basin in north-eastern Siberia. To this end, partial pressure of carbon dioxide (pCO2) and gas exchange velocities (k) were measured at a diverse set of streams and rivers to calculate CO2 evasion fluxes.
We combined these CO2 evasion estimates with satellite remote sensing and geographic information system techniques to calculate total areal CO2 emissions. Our results show that small streams are substantial sources of atmospheric CO2 owing to high pCO2 and k, despite being a small portion of total inland water surface area. In contrast, large rivers were generally near equilibrium with atmospheric CO2. Extrapolating our findings across the Panteleikha-Ambolikha sub-watersheds demonstrated that small streams play a major role in CO2 evasion, accounting for 86% of the total summer CO2 emissions from inland waters within these two sub-watersheds. Further expansion of these regional CO2 emission estimates across time and space will be critical to accurately quantify and understand the role of Arctic streams and rivers in the global carbon budget
W. H. R. Rivers: On the Apparent Size of Objects. Mind. N. S. V. S. 71 bis 80. 1896
No full textW. H. R. RIVERS: ON THE APPARENT SIZE OF OBJECTS. MIND. N. S. V. S. 71 BIS 80. 1896
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (-)
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (12) (a0003)
W. H. R. Rivers: On the Apparent Size of Objects. Mind. N. S. V. S. 71 bis 80. 1896 (12) (p0077
A geomorphological framework for providing ecosystem services in lowland rivers
No full textThe publication of the Millennium Ecosystem Assessment (MA, 2005) has generated widespread scientific debate regarding the importance of linkages between ecosystems and human well-being. An ecosystem services approach has presented many challenges during its early stages of development; fundamentally the ability to classify and value an ecosystem and its services. By its complex nature, ecosystem service research requires an interdisciplinary approach.The thesis focuses on the role of geomorphology as a means to providing a framework for delivering ecosystem services in lowland rivers. The framework introduces a reach-scale analysis of how geomorphological functions (GF) help provide a platform for bio-physical interactions that deliver multiple ecosystem services in lowland rivers. The analysis will assess the influence of geomorphological functions (GF) in providing ecosystem services.Understanding the links between „ecosystem services? and the functioning of ecosystems to human welfare is critical for a wide range of decision-making contexts (Fisher et al., 2008). River restoration provides a useful and practical technique for placing monetary costs to the functions that characterise geomorphologically diverse rivers, whilst allowing for a spatial understanding on how physical characteristics impact the delivery of multiple ecosystem services. Case studies help reveal other direct and indirect benefits associated with riverine environments
Bankfull discharge and recurrence intervals in Irish rivers
No full textDifferent definitions of the bankfull condition in rivers are based on morphological characteristics, boundary conditions and geometrical properties. Consequently, the magnitude and associated return period of the bankfull discharge can be ambiguous. Knowledge of this discharge is important in index flood estimation and subsequent regional flood frequency analysis. This study investigates bankfull discharges and recurrence intervals at 88 locations in the Irish river network using a combination of surveyed bankfull levels, rating curves and equations and photographic records at the sites in question. Catchments ranged in area from approximately 23 km2 to 2778 km2. Recurrence intervals were determined by fitting generalised extreme value (GEV) distributions to the annual maximum flow series at the sites investigated. These intervals were found to be less than 2 years (the median annual flood) at 42 stations (48%) and less than 2·33 years (the mean annual flood assuming a GEV type 1 distribution) at 47 stations (53%). Higher return periods of between 2·33 and 10 years and 10 and 25 years were observed at a further 20% and 6% of locations respectively. Using multivariate regression analysis, the computed bankfull discharges are correlated with catchment descriptors and three expressions are presented for estimating bankfull flows.Deposited by bulk importPermission granted to archive the final PDF (the version used for publication that subscribers gain access to) but this not available yet. On the webpage that the file is hosted on, please reference the journal homepage (www.geotechnicaljournal.com) and including the text “Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.”TS 01.03.1
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