the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Oct 2025
A low-maintenance optoacoustic sensor for black carbon monitoring
Abstract. Regulation of black carbon (BC) emissions is necessary due to their negative impact to climate and human health. We present a low-cost optoacoustic sensor for Black Carbon (BC) emissions, which can provide continuous measurements that are suitable for long-term BC monitoring in highly contaminative environments with low need for frequent maintenance. Insensitivity to contamination is based on a sensor design that integrates protective flows of clean air around the sample measured, which minimizes BC deposition on the detector and optical windows of the sensor. A quantitative analysis shows that the negative effect of BC contamination on sensor performance is reduced by a factor of greater than 300 000 in comparison to an unprotected control sensor. We discuss how the reduced maintenance requirements make the design presented a promising candidate for continuous and long-term BC monitoring of high emitters, enabling disseminated monitoring necessary for regulatory and mitigation measures of BC emissions in the future.
Competing interests: V.N. is a founder and equity owner of Maurus OY, sThesis GmbH, iThera Medical GmbH, Spear UG, and I3 Inc. Authors L.N., V.N., U.S., L.H., N.K. and I.R. are inventors on a pending patent application (Application No. GR20250100576) related to the sensor described in this work.
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Status: open (until 31 Dec 2025)
- RC1: 'Comment on egusphere-2025-4532', Anonymous Referee #1, 25 Nov 2025 reply
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A low-maintenance optoacoustic sensor for black carbon monitoring Linda Haedrich and Nikolaos Kousias https://zenodo.org/records/17190856
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This manuscript presents an optimization of a previously published low-cost optoacoustic black carbon (BC) sensor designed for long-term BC measurements in highly polluted environments. The sensor is based on an ellipsoidal chamber that separates the quartz tuning fork transducer from the aerosol flow path. The optimization consists of a protective clean-air sheath flow that prevents BC from depositing on sensitive components while minimizing acoustic noise from the sheath flow. This results in a reduction in contamination by orders of magnitude, as demonstrated by an experimental study and statistical evaluation. The authors claim a significant reduction in maintenance requirements, enabling the deployment, monitoring, and regulation of BC emissions in harsh environments.
In my opinion, the paper is well organized, fits the scope of the journal, and should be published, subject to minor revisions as detailed below:
Methodology:
Results section:
It would be interesting to see a performance comparison of the sensor with and without sheath flow regarding:
How is the baseline correction performed in more detail? Is a lock-in technique used? If yes, is the phase of the signal considered for the background subtraction?
Fig 3: the colors of the data points are hard to distinguish
Fig. 3a: What does the rising line represent?
Fig. 3b: Where are the spikes in the control and IDSS coming from?
Discussion: