Spectroscopic Mapping & Monitoring �Coastal Wastewater Pollution �in the Tijuana River Estuary �and San Diego Coastal Ocean
Dan Sousa
+ a big team at SDSU and beyond
San Diego State University
14 May 2025
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Overview
Problem Background
Approach
Results
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Problem Background
San Diego / Tijuana beaches are impacted by untreated wastewater
5 million inhabitants, 35 million annual visitors (San Diego Chamber of Commerce, 2021)
Substantial impact to local economy (tourism, small business traffic) and public health (contaminants, disease)
Also a global issue (>1.8 billion people worldwide, largely in low-resource countries, impacted by untreated wastewater & associated diseases (Ryder, 2017)
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Wastewater Discharge in the Tijuana River
One major source of this pollution in the San Diego / Tijuana metro is the Tijuana River
Billions of liters of wastewater are expelled annually – directly into the river channel
Carries harmful pollutants through two major cities (> 3 million residents) and a protected estuary.
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Wastewater Discharge in the Tijuana River
One major source of this pollution in the San Diego / Tijuana metro is the Tijuana River
Billions of liters of wastewater are expelled annually – directly into the river channel
Carries harmful pollutants through two major cities (> 3 million residents) and a protected estuary.
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Wastewater Discharge in the Tijuana River
A key source of pollution: Overloaded, unmaintained, or inoperable treatment plants, Tijuana
Multidimensional issue:
Funding
Skilled workforce
Engineering challenges
International relations
Actively changing
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Many Partners in the Work
EPA
County of San Diego
City of San Diego
City of Imperial Beach
City of Coronado
SD Coastkeeper
Community groups
Partners in Mexico
International Boundary and Water Commission (IBWC)
More…
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PIs at Agua a Través de las Fronteras / Water Across Borders meeting, Tijuana MX.
Mendoza, L. M., Mladenov, N., Kinoshita, A. M., Pinongcos, F., Verbyla, M. E., & Gersberg, R. (2020). Fluorescence-based monitoring of anthropogenic pollutant inputs to an urban stream in Southern California, USA. Science of the Total Environment, 718, 137206.
Fig. 1. Representative EEMs from one replicate experiment with a) 0%, b) 5%, c) 20%, and d) 33% synthetic WW addition to creek water. Representative EEMs also shown for field samples previously collected from Alvarado Creek during a storm event on 6 March 2016 at 2-h increments, as shown in e–f (source: Parsons, 2018. Peak T and Peak C regions are indicated with letters T and C, respectively, in panel a). Discharge values and times shown in bottom right corner. Note the lower maximum intensity value (shown in colorbar) at the start of the storm (e) compared to later times (f–h). Colorbar intensities are in Raman units (RU). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 2. Comparison of synthetic wastewater (WW) in tap water (a, d, g), synthetic WW in creek water (b, e, h), and raw WW in creek water (c, f, i) with TRP fluorescence (top panels), humic-like and chl a fluorescence intensities (middle panels), and TRP:humic ratios (bottom panels). Error bars represent standard deviations of three independent experiments. P values correspond to the curve fitting. All relationships, with the exception of Chl a intensity vs. % synthetic WW in (e), are significant at the p < 0.05 level. All relationships are linear with the exception of TRP:CDOM fluorescence (g), where the fit is a second order polynomial to the equation y = −0.001x2 + 0.059x + 0.3676.
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Water Grabs
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Linking Chemical Composition of Untreated Wastewater with Laboratory, In Situ, and EMIT Spaceborne Spectroscopy
Eva Scrivner1,2
Natalie Mladenov3, Trent Biggs1, Alexandra Grant3, Elise Piazza1, Stephany Garcia4, Christine M. Lee5, Christiana Ade5, Nick Tufillaro6, Philipp Grötsch6, Omar Zurita6, Benjamin Holt5, Daniel Sousa1
1Department of Geography, San Diego State University, San Diego, CA, USA
2Now at: Department of Marine Sciences, University of Connecticut, Groton, CT
3Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, CA, USA
4Tijuana River National Estuarine Research Reserve and Southwest Wetlands Interpretive Association, USA
5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
We would like to thank all undergraduate collaborators who make our field and laboratory sampling efforts possible, including but not limited to: Callie Summerlin, David Penn, Mia Pollasky, Julian Gutierrez, Scotty Dingwall, Blanca Heredia, Trinity Weary, Tate Mckay, and Yzatis Silva.
We gratefully acknowledge primary funding from the NASA Remote Sensing of Water Quality Program (Grant #80NSSC22K0907) and the NASA Applications-Oriented Augmentations for Research and Analysis Program (Grant #80NSSC23K1460).
DS also acknowledges funding from the USDA NIFA Sustainable Agroecosystems Program (Grant #2022-67019-36397), the USDA AFRI Rapid Response to Extreme Weather Events Across Food and Agricultural Systems Program (Grant #2023-68016-40683), the NASA Land-Cover/Land Use Change Program (Grant #NNH21ZDA001N-LCLUC), the NASA EMIT Science and Applications Team (Grant #80NSSC24K0861), the NASA Commercial Smallsat Data Analysis Program (Grant #80NSSC24K0052), the NASA FireSense Airborne Science Program (Grant #80NSSC24K0145), the California Climate Action Seed Award Program, and the NSF Signals in the Soil Program (Award #2226649).
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WASI Inverse Simulations
Presentation Title
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620 nm absorption is robust to noise in hyperspectral, not multispectral resolution
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765 and 985 nm absorption
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765 nm absorption consistent with liquid water.
985 nm highly absorbed by atmospheric water vapor and not easily detectable by satellite.
Absorption spectra of pure seawater.
Figure credit: Pegau and Zaneveld, 1993, Mobley e.d., 2022
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References
Paswan, M.B., Chudasama, M.M., Mitra, M. et al. Fluorescence Quenching Property of C-Phycocyanin from Spirulina platensis and its Binding Efficacy with Viable Cell Components. J Fluoresc26, 577–583 (2016). https://doi.org/10.1007/s10895-015-1742-7
Pegau, W. S., & Zaneveld, J. V. (1993). Temperature-dependent absorption of water in the red and near-infrared portions of the spectrum [Electronic version]. Limnology and Oceanography, 38(1), 188-192.
Mobley, C. D. (ed.) (2022) The Oceanic Optics Book. Dartmouth, NS, Canada, International Ocean Colour Coordinating Group (IOCCG), 924pp. DOI: http://dx.doi.org/10.25607/OBP-1710
* References cited in presentation; full reference list in speaker notes.