203 research outputs found
FluoRAS Sensor - Online organic matter for optimising recirculating aquaculture systems
FluorRAS will develop a sensor that can save recycled fish farms 30% per year in water and energy consumption for water treatment, as well as optimize nitrogen removal. The sensor will be developed in a partnership between engineers (KrĂźger A / S) and researchers (DTU), and the product will be made available to the entire sector through Danish Aquaculture. Global aquaculture production is expected to double within the next 15 years. Recycling technology has a great potential for supporting environmentally and economically sustainable production. However, the technology has some challenges in balancing both the maintenance of necessary water quality and water treatment costs. Loss of production due to poor water quality is expensive and can be avoided with correct sensor systems. Accumulation of dissolved organic matter and nutrients in the water reduce the effectiveness of UV treatment, is a source of nutrition for opportunistic pathogens, and reduces the effectiveness of the biofilter's removing ammonia. Modern recycling systems are therefore dependent on a network of online sensors that monitor and respond to changes in water quality, but currently there is a need for a sensor to monitor the accumulation of organic matter. FluoRAS aims to fill this gap in technology by developing an online fluorescence sensor. The sensor is based on non-destructive, online optical technology that does not require chemicals and can run continuously
Production and transformation of dissolved neutral sugars and amino acids by bacteria in seawater
Dissolved organic matter (DOM) in the ocean consists of a heterogeneous
mixture of molecules, most of which are of unknown origin. Neutral sugars and
amino acids are among the few recognizable biomolecules in DOM, and the
molecular composition of these biomolecules is shaped primarily by biological
production and degradation processes. This study provides insight into the
bioavailability of biomolecules as well as the chemical composition of DOM
produced by bacteria. The molecular compositions of combined neutral sugars
and amino acids were investigated in DOM produced by bacteria and in DOM
remaining after 32 days of bacterial degradation. Results from bioassay
incubations with natural seawater (sampled from water masses originating from
the surface waters of the Arctic Ocean and the North Atlantic Ocean) and
artificial seawater indicate that the molecular compositions following
bacterial degradation are not strongly influenced by the initial substrate or
bacterial community. The molecular composition of neutral sugars released by
bacteria was characterized by a high glucose content (47 mol %) and
heterogeneous contributions from other neutral sugars (3â14 mol %). DOM
remaining after bacterial degradation was characterized by a high galactose
content (33 mol %), followed by glucose (22 mol %) and the
remaining neutral sugars (7â11 mol %). The ratio of D-amino acids to
L-amino acids increased during the experiments as a response to bacterial
degradation, and after 32 days, the D/L ratios of aspartic
acid, glutamic acid, serine and alanine reached around 0.79, 0.32, 0.30 and
0.51 in all treatments, respectively. The striking similarity in neutral
sugar and amino acid compositions between natural (representing marine
semi-labile and refractory DOM) and artificial (representing bacterially
produced DOM) seawater samples, suggests that microbes transform bioavailable
neutral sugars and amino acids into a common, more persistent form
Controls of dissolved organic matter quality: Evidence from a large-scale boreal lake survey
Inland waters transport large amounts of dissolved organic matter (DOM) from terrestrial environments to the oceans, but DOM also reacts en route, with substantial water column losses by mineralization and sedimentation. For DOM transformations along the aquatic continuum, lakes play an important role as they retain waters in the landscape allowing for more time to alter DOM. We know DOM losses are significant at the global scale, yet little is known about how the reactivity of DOM varies across landscapes and climates. DOM reactivity is inherently linked to its chemical composition. We used fluorescence spectroscopy to explore DOM quality from 560 lakes distributed across Sweden and encompassed a wide climatic gradient typical of the boreal ecozone. Six fluorescence components were identified using parallel factor analysis (PARAFAC). The intensity and relative abundance of these components were analyzed in relation to lake chemistry, catchment, and climate characteristics. Land cover, particularly the percentage of water in the catchment, was a primary factor explaining variability in PARAFAC components. Likewise, lake water retention time influenced DOM quality. These results suggest that processes occurring in upstream water bodies, in addition to the lake itself, have a dominant influence on DOM quality. PARAFAC components with longer emission wavelengths, or red-shifted components, were most reactive. In contrast, protein-like components were most persistent within lakes. Generalized characteristics of PARAFAC components based on emission wavelength could ease future interpretation of fluorescence spectra. An important secondary influence on DOM quality was mean annual temperature, which ranged between â6.2 and +7.5 °C. These results suggest that DOM reactivity depends more heavily on the duration of time taken to pass through the landscape, rather than temperature. Projected increases in runoff in the boreal region may force lake DOM toward a higher overall amount and proportion of humic-like substances
Fluorescence spectroscopy and multi-way techniques. PARAFAC
PARAllel FACtor analysis (PARAFAC) is increasingly used to decompose fluorescence excitation emission matrices (EEMs) into their underlying chemical components. In the ideal case where fluorescence conforms to Beers Law, this process can lead to the mathematical identification and quantification of independently varying fluorophores. However, many practical and analytical hurdles stand between EEM datasets and their chemical interpretation. This article provides a tutorial in the practical application of PARAFAC to fluorescence datasets, demonstrated using a dissolved organic matter (DOM) fluorescence dataset. A new toolbox for MATLAB is presented to support improved visualisation and sensitivity analyses of PARAFAC models in fluorescence spectroscopy. Š 2013 The Royal Society of Chemistry
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