Detection of Microplastics in Water and Wastewater Streams Using Fluorescence Spectroscopy

Introduction

Cari Campbell*, Amy Bigelow*, Loren Miller, Kyle Nelson, Federick Pinongcos, Alexa Zapata, Natalie MladenovDepartment of Civil, Construction, and Environmental Engineering, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182

*Lead authors: carimay05@yahoo.com, amybigelow@hotmail.com

Results Preliminary Results

References

Conclusions

• Plastic fluorophores peaked at different excitation/emission wavelengths

• Detection of polyethylene and polystyrene is possible in wastewater

• Leaching from polyethylene, polystyrene and a generic plastic container can beseen in ultrapure water

• Highest fluorescence yield from polystyrene and polyethylene whereaspolypropylene and PVC leached very little organic matter

Browne, M. A. Accumulation of Microplastic on Shorelines Worldwide: Sources and Sinks. Environmental Science and Technology, 2011, Vol. 45, No21, pp 9175–9179

Coble, P. G. Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy. Elsevier, 1996, Vol. 52, pp.325–346.

Fellman, J. B., et al. Fluorescence spectroscopy opens new windows into dissolved organic matter dynamics in freshwater ecosystems: A review.Limnology and Oceonography, Inc, 2010, Vol. 55, No 6, pp. 2452–2462.

McKnight, D., et al. Spectrofluorometric Characterization of Dissolved Organic Matter for Indication of Precursor Organic Material and Aromaticity. Limnology and Oceanography, 2001, Vol. 46, No. 1, pp. 38-48.

Acknowledgements

Future Work

The SDSU student chapter of AWWA would like to thank Dr. Natalie Mladenov for supervising us with this researchand Professor Tom Zink for reviewing it. Harshad Kulkarni for assisting with the use of Mathlab and the aqualog andDr. Julio Valdes for allowing our group to use the high definition microscope camera.

• PARAFAC analysis needed to more accurately “fingerprint” microplastic peaks.

• Testing for plastic leaching in other water streams including stormwater and riverwater.

• Additional testing on same plastic types to verify results.

• Study the effect of irradiation on rates of leaching and fluorescence from plastics.

Buoyant: YesCircumference: 1.77 mmDensity: 1.38 g/cm3

Diameter: 0.64 mmSurface Area: 0.99 mm2

Fluorescence Intensity: 1.1 RUFluorescence yield: 0.51 RU/g

Buoyant: Yes

Density: 1.05 g/cm3

Diameter: 3 mmSurface Area: 28.27 mm2

Fluorescence Intensity: 0.82 RUFluorescence yield: 5.54 RU/g

Buoyant: Yes

Density: 0.95 g/cm3

Surface Area: 50.27 mm2

Fluorescence Intensity: 0.035 RUFluorescence yield: 0.012 RU/g

Buoyant: Yes

Density: 1.2 g/cm3

Surface Area: 20.27 mm2

Fluorescence Intensity: 0.06 RUFluorescence yield: 0.047 RU/g

Figure 7: Two of the four plastics showed an increase in dissolution over time in ultrapure water

y = 0.0221x + 0.354R² = 0.7752

y = 0.0494x + 0.1041R² = 0.9999

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Time (days)

PE

PP

PS

PVC

Linear (PE)

Linear (PS)

Figure 5: Fluorescence peak locations from four plastics leached in ultrapure water

PVC peak 273nm ex/298nm em

Polypropylene peak 255nm ex/335nm em

Polyethylene peak270nm ex/296nm em

Polystyrene peak 246nm ex/303nm em

Polystyrene PeakPolystyrene in Wastewater Wastewater Blank

Figure 6: The polystyrene peak can be detected in the wastewater stream by subtracting the wastewater blank peak from the peaks in a polystyrene plus wastewater sample

Motivation: As plastics are used in various everyday products, how they react indifferent environments is of great concern. The main goal of our research is to acquirefluorescence signatures of plastics in order to track the presence of microplastics’compounds in various aquatic environments. This could include in wastewatertreatment plants, groundwater, and oceans – among others.Research Question: Is it possible to detect plastic leaching in water and wastewaterusing fluorescence spectroscopy?

Methods

Procedure: Fluorescence measuredimmediately, after 1 week, and after 2 weeksParticle Analysis: Weight and linearmeasurements taken of microplastic particlesFluorescence Spectroscopy:Fluorescence 3-D excitation emission matrix(EEM) used to “fingerprint” what compoundsmay be in the sample and their capacity toleach into solutionInstrument:Horiba Aqualog Spectrofluorometer

Jablonski Diagram

Sample EEM

Samples: Plastics Polyethylene (PE),Polystyrene (PS), Polyvinyl Chloride(PVC), and Polypropylene (PP)added to ultrapure water as well asprimary treated wastewater

Figure 1: Example Schematics of Primary Wastewater Treatment. Source: civil.engr.siu.edu

Figure 2: Plastic samples with Ultra Pure and Waste Water.

Figure 3: Sample EEM showing typical peaks in surface water.

Microplasticsfloat and remain

in stream

Figure 4: Jablonski diagram illustrating the concept of Fluorescence. Source: web.uvic.ca

• EEMs corrected for Rayleighscattering, Raman normalized, anda blank subtraction done usingMatlab

• Peaks:

• A, C and M Humic Like

• B and TMicrobial

Possible Implications

• Plastics that leach more can be tracked more easily with fluorescence

• Lower leaching rates could correspond to slower degradation rates, which could lead to environmental problems

• Plastics found in landfill leachate could potentially contaminate groundwater

• Plastics leach estrogen-like compounds that have adverse health effects