Uncertainties in selected river water quality data

International audienceMonitoring of surface waters is primarily done to detect the status and trends in water quality and to identify whether observed trends arise from natural or anthropogenic causes. Empirical quality of river water quality data is rarely certain and knowledge of their uncertainties is essential to assess the reliability of water quality models and their predictions. The objective of this paper is to assess the uncertainties in selected river water quality data, i.e. suspended sediment, nitrogen fraction, phosphorus fraction, heavy metals and biological compounds. The methodology used to structure the uncertainty is based on the empirical quality of data and the sources of uncertainty in data (van Loon et al., 2005). A literature review was carried out including additional experimental data of the Elbe river. All data of compounds associated with suspended particulate matter have considerable higher sampling uncertainties than soluble concentrations. This is due to high variability within the cross section of a given river. This variability is positively correlated with total suspended particulate matter concentrations. Sampling location has also considerable effect on the representativeness of a water sample. These sampling uncertainties are highly site specific. The estimation of uncertainty in sampling can only be achieved by taking at least a proportion of samples in duplicates. Compared to sampling uncertainties, measurement and analytical uncertainties are much lower. Instrument quality can be stated well suited for field and laboratory situations for all considered constituents. Analytical errors can contribute considerably to the overall uncertainty of river water quality data. Temporal autocorrelation of river water quality data is present but literature on general behaviour of water quality compounds is rare. For meso scale river catchments (500?3000 km2) reasonable yearly dissolved load calculations can be achieved using biweekly sample frequencies. For suspended sediments none of the methods investigated produced very reliable load estimates when weekly concentrations data were used. Uncertainties associated with loads estimates based on infrequent samples will decrease with increasing size of rivers

Uncertainties in selected surface water quality data

International audienceMonitoring of surface waters is primarily done to detect the status and trends in water quality and to identify whether observed trends arise form natural or anthropogenic causes. Empirical quality of surface water quality data is rarely certain and knowledge of their uncertainties is essential to assess the reliability of water quality models and their predictions. The objective of this paper is to assess the uncertainties in selected surface water quality data, i.e. suspended sediment, nitrogen fraction, phosphorus fraction, heavy metals and biological compounds. The methodology used to structure the uncertainty is based on the empirical quality of data and the sources of uncertainty in data (van Loon et al., 2006). A literature review was carried out including additional experimental data of the Elbe river. All data of compounds associated with suspended particulate matter have considerable higher sampling uncertainties than soluble concentrations. This is due to high variability's within the cross section of a given river. This variability is positively correlated with total suspended particulate matter concentrations. Sampling location has also considerable effect on the representativeness of a water sample. These sampling uncertainties are highly site specific. The estimation of uncertainty in sampling can only be achieved by taking at least a proportion of samples in duplicates. Compared to sampling uncertainties measurement and analytical uncertainties are much lower. Instrument quality can be stated well suited for field and laboratory situations for all considered constituents. Analytical errors can contribute considerable to the overall uncertainty of surface water quality data. Temporal autocorrelation of surface water quality data is present but literature on general behaviour of water quality compounds is rare. For meso scale river catchments reasonable yearly dissolved load calculations can be achieved using biweekly sample frequencies. For suspended sediments none of the methods investigated produced very reliable load estimates when weekly concentrations data were used. Uncertainties associated with loads estimates based on infrequent samples will decrease with increasing size of rivers

The steering gaits of sperm

Sperm are highly specialized cells, which have been subject to substantial evolutionary pressure. Whereas some sperm features are highly conserved, others have undergone major modifications. Some of these variations are driven by adaptation to mating behaviours or fitness at the organismic level. Others represent alternative solutions to the same task. Sperm must find the egg for fertilization. During this task, sperm rely on long slender appendages termed flagella that serve as sensory antennas, propellers and steering rudders. The beat of the flagellum is periodic. The resulting travelling wave generates the necessary thrust for propulsion in the fluid. Recent studies reveal that, for steering, different species rely on different fundamental features of the beat wave. Here, we discuss some examples of unity and diversity across sperm from different species with a particular emphasis on the steering mechanisms. This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’

Ensuring metrological control of the means of thermal control

В настоящее время все большее применение набирают приборы бесконтактного и быстродейственного контроля температуры приборами, регистрирующими излучения в световом и инфракрасном диапазонах.At present, more and more devices are being used to collect non-contact and high-speed temperature control instruments that register radiation in the light and infrared ranges

Diurnal versus spatial variability of greenhouse gas emissions from an anthropogenically modified lowland river in Germany

Greenhouse gas (GHG) emissions from rivers are globally relevant, but quantification of these emissions comes with considerable uncertainty. Quantification of ecosystem-scale emissions is challenged by both spatial and short-term temporal variability. We measured spatio-temporal variability of CO2 and CH4 fluxes from a 1 km long reach of the lowland river Elbe in Germany over 3 d to establish which factor is more relevant to be taken into consideration: small-scale spatial variability or short-term temporal variability of CO2 and CH4 fluxes. GHG emissions from the river reach studied were dominated by CO2, and 90 % of total emissions were from the water surface, while 10 % of emissions were from dry fallen sediment at the side of the river. Aquatic CO2 fluxes were similar at different habitats, while aquatic CH4 fluxes were higher at the side of the river. Artificial structures to improve navigability (groynes) created still water areas with elevated CH4 fluxes and lower CO2 fluxes. CO2 fluxes exhibited a clear diurnal pattern, but the exact shape and timing of this pattern differed between habitats. By contrast, CH4 fluxes did not change diurnally. Our data confirm our hypothesis that spatial variability is especially important for CH4, while diurnal variability is more relevant for CO2 emissions from our study reach of the Elbe in summer. Continuous measurements or at least sampling at different times of the day is most likely necessary for reliable quantification of river GHG emissions.</p

Effect of Body Mass Index on pregnancy outcomes in nulliparous women delivering singleton babies

Peer reviewedPublisher PD

Горизонтальные классификаторы. Основы теории и расчета: моногр.

Приведены технологические схемы получения строительных песков при гидромеханизированной добыче, основные конструктивные схемы классификаторов, используемых при получении строительных песков. Особое внимание уделено изучению процесса взаимодействия проточной части горизонтального классификатора с совокупностью твердых частиц, расположенных в горизонтальном ускоренном потоке несущей среды. Выполнено математическое моделирование ускоренного движения горизонтального потока и твердых частиц в пределах разнонаклонных поверхностей горизонтального классификатора. Экспериментально изучено гравитационное осаждение твердых частиц, рассмотренное в виде вертикальной и горизонтальной составляющих, а также влияние стесненности движения и перемещения твердых частиц относительно несущего горизонтального потока. Приведена методика расчета и выбора параметров классификаторов, информация об опыте проектирования и внедрения горизонтальных классификаторов в составе добычных комплексов при освоении обводненных месторождений песков. Монография может быть полезна студентам, инженерно-техническим работникам, сотрудникам высших учебных заведений, научно-исследовательских институтов и проектных организаций горной промышленности