In Situ Water Quality Monitoring Using an Optical Multiparameter Sensor Probe
Abstract
:1. Introduction
Parameter | Wavelength | Proxy For | Calibrant | Ref. |
---|---|---|---|---|
Fluorescence Spectroscopy | ||||
Tryptophan-like fluorescence (TLF) | λex = 280 nm λem = 365 nm | biological activity, microbial contamination with | L-Tryptophan | [21] |
Humic-like fluorescence (HLF) | λex = 280 nm λem = 450 nm | autochthonous (within stream algal and microbial activity) and allochthonous (soil-derived organic matter) generation of small colloidal and dissolved organic matter | Quinine sulfate | [22] |
Fluorescent DOM (FDOM) | λex = 325 nm λem = 470 nm | total DOC concentration | Quinine sulfate | [23] |
Chlorophyll a (f-Chl a) | λex = 430 (470) nm λem = 675–750 nm | biomass of algae | Dyes, pure or extracted Chlorophyll a | [24] |
Phycocyanin (f-PC) | λex = 590 nm λem = 640–690 nm | biomass of cyanobacteria | Phycocyanin | [25] |
Fluorescence index (FI) | λex = 370 nm λem = 470 and 520 nm | microbial (high FI~1.8) or terrestrial (low FI~1.2) source of DOM | [26] | |
Scattered light measurement | ||||
Turbidity | portion of light scattered at angle 90° from the incident beam (λ > 800 nm) | loss of clarity in water | Formazin turbidity standard | [27] |
UV/Vis spectroscopy | ||||
Nitrate | A217–240 nm | eutrophication of freshwater ecosystems | NO3-N | [7] |
Spectral absorption coefficient (SAC254) | A254 nm | organic loads of water | [9,28] | |
Colored dissolved organic matter (CDOM) | A254 nm or A370 nm | colored and photoactive fraction of DOM | [29,30] | |
Chemical oxygen demand (COD) | A225–260 nm | pollution of water by reducing substances’ | [31] | |
Phycocyanin (PC) | A615 nm and A652 nm | cyanobacterial components | [32] | |
Turbidity | A>800 nm | loss of clarity in water | Formazin turbidity standard | [27] |
- Synchronous data acquisition: UV/Vis and fluorescence measurements can be an-alyzed in one step. The absorbance measurement is made in a 180° configuration while fluorescence emission is measured in 90° geometry. The path length of the measurement cell is 10 mm. The water sample is pumped through the measuring cell. Due to its position inside the sensor probe, external interfering influences were minimized. The spectrometer permits detection over the entire wavelength range.
- Adaptable hardware configuration: To adapt the sensor probe to different aquatic conditions, the sensor configuration can be easily changed. This includes the replacement of light sources and the adjustment of their intensities. The operational conditions of the spectrometer and the integration parameters can also be easily changed.
- Open data processing platform: The integrated processing platform facilitates the further handling and fusion of the spectral data (quantification, turbidity compensation, qualitative and quantitative assessment of water quality information). All data are available and adjustable for users at each level of processing.
- Open Data Model: Processed data, measurement methods and metainformation are stored in a holistic structure. All these data can be transferred by the user.
- Data visualization: The data are displayed in real time on a dashboard for analysis and pattern identification.
- Remote control: A specially programmed app enables access to the sensor probe. It allows the monitoring of operating status, the definition of measurement intervals and times, as well as the execution of functional tests on the light sources. Furthermore, the app shows quantitative results of predefined analytes.
2. Materials and Methods
2.1. Design and Development of the UV/Vis–Fluorescence Submersible Sensor Probe
2.1.1. Hardware Development
2.1.2. Software Development
2.1.3. Field Application Setup
2.2. Lab Validation
2.2.1. Preparation of Water Samples
2.2.2. LED Array Configuration
2.2.3. Data Collection and Data Processing
3. Results
3.1. Lab Validation
3.2. Results from Field Tests
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Module | Component | Software |
---|---|---|
View | Data Fusion Dashboard | Grafana |
Model | HAL Storage | Python-FastAPI InfluxDB 2.0 |
Control | DPM | Node-Red |
LED | Excitation Wavelength [nm] | Current [mA] | Parameter |
---|---|---|---|
DUV-HL5N, Roithner LaserTechnik GmbH | 340 | 40 (pulsed) | DOM |
VL440-5-15 | 440 | 100 (pulsed) | Chlorophyll a |
CY5111A-WY, Roithner | 590 | 100 (pulsed) | Phycocyanin |
OP265FAB, TT Electronics | 850 | 120 (constant) | Turbidity |
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Goblirsch, T.; Mayer, T.; Penzel, S.; Rudolph, M.; Borsdorf, H. In Situ Water Quality Monitoring Using an Optical Multiparameter Sensor Probe. Sensors 2023, 23, 9545. https://doi.org/10.3390/s23239545
Goblirsch T, Mayer T, Penzel S, Rudolph M, Borsdorf H. In Situ Water Quality Monitoring Using an Optical Multiparameter Sensor Probe. Sensors. 2023; 23(23):9545. https://doi.org/10.3390/s23239545
Chicago/Turabian StyleGoblirsch, Tobias, Thomas Mayer, Stefanie Penzel, Mathias Rudolph, and Helko Borsdorf. 2023. "In Situ Water Quality Monitoring Using an Optical Multiparameter Sensor Probe" Sensors 23, no. 23: 9545. https://doi.org/10.3390/s23239545