Using Cdom Spectral Shape Information to Improve the Estimation of Doc Concentration in Inland Waters: A Case Study of Andean Patagonian Lakes

2021 ◽  
Author(s):  
L. G. De Stefano ◽  
A. Sánchez Valdivia ◽  
D. Gianello ◽  
M. Gerea ◽  
M. Reissig ◽  
...  
Keyword(s):  
Spectral Shape ◽  
Inland Waters ◽  
Shape Information ◽  
Patagonian Lakes ◽  
Doc Concentration

Remote sensing retrieval of chlorophyll-α in inland waters based on ensemble modeling: a case study on Panjiakou and Daheiting reservoirs

2020 ◽  
Vol 14 (02) ◽  
pp. 1
Author(s):  
Yin Cao ◽  
Yuntao Ye ◽  
Lili Liang ◽  
Hongli Zhao ◽  
Yunzhong Jiang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Inland Waters ◽  
Ensemble Modeling

scholarly journals Impact of changing DOC concentrations on the potential distribution of acid sensitive biota in a boreal stream network

2007 ◽  
Vol 4 (5) ◽  
pp. 3145-3173 ◽  
Author(s):  
H. Laudon ◽  
I. Buffam
Keyword(s):  
Stream Water ◽  
Base Flow ◽  
Spring Flood ◽  
Stream Network ◽  
Stream Length ◽  
Marginal Change ◽  
Sampling Locations ◽  
Doc Concentration ◽  
Aquatic Landscape

Abstract. DOC concentrations have increased in many surface waters in Europe and North America over the past few decades. As DOC exerts a strong influence on pH this DOC increase could have detrimental effects on acid sensitive biota in many streams and lakes. To investigate the potential implications of changes in the DOC concentration on stream water biota, we have used a mesoscale boreal stream network in northern Sweden as a case study. The network was sampled for stream water chemistry at 60 locations during both winter base flow and spring flood periods, representing the extremes experienced annually in these streams both in terms of discharge and acidity. The effect of changing DOC on pH was modeled for all sampling locations using an organic acid model, with input DOC concentrations for different scenarios adjusted by between –30% and +50% from measured present concentrations. The resulting effect on pH was then used to quantify the proportion of stream length in the catchment with pH below the acid thresholds of pH 5.5 and pH 5.0. The results suggest that a change in stream water DOC during base flow would have only a limited effect on pH and hence on the stream length with pH below the acid thresholds. During the spring flood on the other hand a change in DOC would strongly influence pH and the stream length with pH below the acid thresholds. For example an increase in DOC concentration of 30% at all sites would increase the proportion of stream length with pH below 5.5 from 37% to 65%, and the proportion of stream length with pH below 5.0 would increase from 18% to 27%. The results suggest that in poorly-buffered high DOC waters, even a marginal change in the DOC concentration could impact acid sensitive biota in a large portion of the aquatic landscape.

Accurate Short Period Corrosion Growth Rates From Combined MFL-UT Inline Inspection: A Case Study

2012 ◽  
Author(s):  
Johannes Palmer ◽  
Thomas Hennig
Keyword(s):  
Hot Spots ◽  
Systematic Errors ◽  
Shape Information ◽  
Monetary Benefit ◽  
Average Maximum ◽  
Short Period ◽  
Corrosion Mechanisms ◽  
Challenging Question ◽  
Flux Leakage

Inline inspection (ILI) identifies most significant anomalies - at the time of inspection. To recognize those individual features, which have the highest potential to enter these ranks, perhaps soon, is a challenging question, which is not necessarily covered with established ILI approaches. Whether the circumstances permit the identification and reliable description of individual corrosion hot spots depend on the ILI quality, the specific feature shape-dependent sizing, the comparability of the data and the time-dependent development of the anomaly. This case study demonstrates the enormous benefits of the combination of two technologies. The robust, indirect Magnetic Flux Leakage (MFL) methodology and the direct Ultrasonic Testing (UT) ILI tool. The intelligent interpretative combination of the two ILI information sources exceeds significantly the straight forward statistical combination benefit. The presented approach demonstrates how to: • identify features not suitable to UT stand alone sizing. • compensate systematic errors from MFL sizing models and calibration assumptions. • introduce UT shape information as major improvement to MFL sizing. • apply MFL amplitude based depth sizing. • reduce the subsequent sizing tolerance to values, which allow corrosion prediction based on even short term repeated ILI intervals. Applied to the identified group of pinholes and embedded pinholes with an average maximum depth of more than 50% the method delivered a depth sizing accuracy of ±6.0% wall thickness at 80% certainty. The fact, that even smaller corrosion growth rate values become resolvable, allows for the equivalent shortening of the re-inspection intervals and for the prolongation of the validity of prediction, whatever may be advisable in specific cases. Also it is shown, that this approach does not require to rerun similar tools, because systematic errors can be compensated absolutely with this approach. The optimization of inspection strategies and methods with regard to specific pipeline problems can have monetary benefit even at higher inspection costs. More sophisticated ILI systems requiring specialist data analysis become justified for equivalent pipeline use cases. The presented combination of the two independent ILI methodologies bears significant useful potential to approach aggressive corrosion mechanisms, e.g. microbial corrosion or CP shielding.

scholarly journals Reactivity, fate and functional roles of dissolved organic matter in anoxic inland waters

2020 ◽  
Vol 16 (2) ◽  
pp. 20190694 ◽  
Author(s):  
Maximilian P. Lau ◽  
Paul del Giorgio
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Inland Waters ◽  
Aquatic Environments ◽  
Anoxic Conditions ◽  
Functional Roles ◽  
Network Scale ◽  
Aquatic Compartment ◽  
Global Cycle

The transit of organic matter (OM) through the aquatic compartment of its global cycle has been intensively studied, traditionally with a focus on the processing and degradation of its dissolved fraction (dissolved organic matter, DOM). Because this is so intimately related to oxidation, the notion tenaciously persists that where oxygen is absent, DOM turnover is markedly slowed. In this Opinion Piece, we outline how diverse processes shape, transform and degrade DOM also in anoxic aquatic environments, and we focus here on inland waters as a particular case study. A suite of biogeochemical DOM functions that have received comparatively little attention may only be expressed in anoxic conditions and may result in enhanced biogeochemical roles of these deoxygenated habitats on a network scale.

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