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| Titel |
High frequency turbidity as a proxy for total phosphorus: application in a
mixed land use catchment in Sweden |
| VerfasserIn |
Emma Lannergård, José L. J. Ledesma, Jens Fölster, Martyn N. Futter |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140669
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| Publikation (Nr.) |
 EGU/EGU2017-4089.pdf |
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| Zusammenfassung |
| Surface water eutrophication resulting from excessive phosphorus (P) input is one of the
most challenging water issues of today. Total phosphorus (TP) concentrations have
high temporal variability, which makes the parameter hard to monitor adequately.
We explored the possibility of using high frequency turbidity as a proxy for TP in
Sävjaån, a stream in a mixed land use catchment in Sweden. An in situ sensor
(YSI 600OMS VS) monitoring turbidity every 10th minute, was situated close
to the outlet of Sävjaån during 2014 and 2015. In situ and grab sample turbidity
measurements were highly correlated (linear regression, r2=0.90). The maximum
turbidity concentration measured by the sensor was at most 13 times higher than the
highest concentration from the grab samples. The average turbidity concentration
from the two methods was close to similar, as well as the Ecological Quality Ratios
(EQR) calculated from the two data sets. The correlation between TP and high
frequency turbidity was very high (r2=0.79) and between TSS and turbidity high
(r2=0.67). When comparing load estimations from the high frequency data with monthly
grab sampling and linear interpolation, the high frequency load was 7 % smaller in
2014 and 17 % larger in 2015. In 2014 the monthly grab sampling caught peaks
in TP concentration, which with linear interpolation affected the nearby months
and furthermore the yearly load. However, in 2015 peaks in concentration were
overlooked when using grab sampling, which gave a larger yearly load when using the
high frequency data. Season and flow intensity may affect the relationship between
turbidity and TP, however this could not be statistically proven in this study. The proxy
relationship could also result in uncertainties tied to unexplained diurnal variations of
turbidity, proportion particulate bound P or hysteresis. Uncertainties arising from
the use of sensors (e.g. sensor calibration and spatial representation) must as well
be recognized. To successfully understand the site specific relationships between
turbidity and TP we need to investigate these uncertainties. The results from the study
will be used for further exploring potential of sensor technology in environmental
monitoring. Specifically, we are exploring the use of sensors to support long term water
quality monitoring and better estimate phosphorus load for regulatory water quality
assessment.
Keywords: High frequency monitoring, in situ sensor, surrogate measurements, total
phosphorus, turbidity, load estimations |
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