Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors:Natural Fluctuations or Artefacts?

Jacobs, S.R. and Weeser, B. and Rufino, M.C. and Breuer, L. (2020) Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors:Natural Fluctuations or Artefacts? Sensors, 20 (3). ISSN 1424-8220

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Abstract

In situ spectrophotometers measuring in the UV-visible spectrum are increasingly used to collect high-resolution data on stream water quality. This provides the opportunity to investigate short-term solute dynamics, including diurnal cycling. This study reports unusual changes in diurnal patterns observed when such sensors were deployed in four tropical headwater streams in Kenya. The analysis of a 5-year dataset revealed sensor-specific diurnal patterns in nitrate and dissolved organic carbon concentrations and different patterns measured by different sensors when installed at the same site. To verify these patterns, a second mobile sensor was installed at three sites for more than 3 weeks. Agreement between the measurements performed by these sensors was higher for dissolved organic carbon (r > 0.98) than for nitrate (r = 0.43–0.81) at all sites. Higher concentrations and larger amplitudes generally led to higher agreement between patterns measured by the two sensors. However, changing the position or level of shading of the mobile sensor resulted in inconsistent changes in the patterns. The results of this study show that diurnal patterns measured with UV-Vis spectrophotometers should be interpreted with caution. Further work is required to understand how these measurements are influenced by environmental conditions and sensor-specific properties.

Item Type:
Journal Article
Journal or Publication Title:
Sensors
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2200/2208
Subjects:
ID Code:
141652
Deposited By:
Deposited On:
20 Feb 2020 15:20
Refereed?:
Yes
Published?:
Published
Last Modified:
29 Mar 2020 06:59