Large seasonal variation in microplastic concentration from the Truckee River, United States

Lukasik, Hannah1; Kozloski, Rachel1; Monteith, Marin1; Arienzo, Monica 1

Published Apr 16, 2026; Updated Jul 16, 2026 on Dryad. https://doi.org/10.5061/dryad.66t1g1kg4

Abstract

Using a field deployable peristaltic pump, we collected samples for MP concentration analysis along the Truckee River in the western United States. Samples were collected during the fall of 2022 and the spring of 2023 across 6 and 8 sites, respectively. The samples were processed and analyzed with microscope‑enabled Fourier Transform Infrared spectroscopy. This dataset includes the resulting FTIR results.

Dataset DOI: 10.5061/dryad.66t1g1kg4

Description of the data and file structure

Files and variables

File: Filter_info.csv

Description: Information for each filter analyzed.

Variables

Site Number: site number filter was collected at
Site Name: site name filter was collected at
Date Visited: Date filter was collected
Oxidation (10% Hydrogen Peroxide): Did the filter undergo oxidation with 10 % hydrogen peroxide? Yes or No
Density Separation (Sodium Bromide): Did the filter undergo density separation with sodium bromide? Yes or No
Percent of particles analyzed by FTIR (%): Percentage of particles analyzed by FTIR
Notes: Additional notes

File: Top_Matches_Truckee_9b_Mustang_Apr2423_100umSF_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 9 collected April 24 2023, filter #2

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures in corresponding manuscript:
Figures 4, 5, 6

File: Top_Matches_Truckee_10_Wadsworth_May0423_100umSFR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 10 collected May 04 2023

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst

Associated figures:
- Figures 4, 5, 6

File: TR_MDA_Blanks.csv

Description: Blanks were used to calculate Minimal Detectable Amounts

Variables

Blank_detect: Polymer Type
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
average count. this is the average count across the six blanks
MDA: Minimal Detectable Amount Value. This value was used to subtract from sample results.

Associated figures: Not applicable

File: Top_Matches_Truckee_4_Verdi_May0523_100umSFR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 4 collected May 5 2023

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_3_Glenshire_Nov0422_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 3 collected November 4 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

File: Top_Matches_Truckee_3_Glenshire_Apr1923_100umSFR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 3 collected April 19 2023

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_2_A1_Apr2623_100umS_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 2 collected April 26 2023

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_8_Lockwood_Apr2123_100umSFR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 8 collected April 21 2023

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_4_Verdi_Nov_100umS_101923_1to132_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 4 collected November 19 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

File: Top_Matches_Truckee_5_Mayberry_Oct2622_100umS_1to92_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 5 collected October 26 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

File: Top_Matches_Truckee_9a_Mustang_Apr2423_100umSR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 9 collected April 24 2023, filter #1

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_7_DownWWTP_Apr1823_100umSFR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 7 collected April 18 2023

Variables

IIndex: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_6b_RockPark_Apr1123_100umSF_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 6 collected April 11 2023, filter #1.

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_6a_RockPark_Apr1123_100umSR_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 6 collected April 11 2023, filter #2

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 4, 5, 6

File: Top_Matches_Truckee_9_Mustang_Nov1022_100um_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 9 collected November 10 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

File: Top_Matches_Truckee_6_RockPark_Dec0222_100um_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 6 collected Dec 2 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

File: Top_Matches_Truckee_7_WWTPDown_Nov1122_100umS_1to107_derivative_T0.7_results.csv

Description: FTIR results from Truckee river site 7 collected November 11 2022

Variables

Index: original file name of each row
size_W: width of particle in micrometers
size_L: length of particle in micrometers
morphology: Morphology of particle was limited to fragments, films, and fibers/filaments
color: color of particle
notes: any notes from the analyst
match_val: the pearson's correlation to the match spectra. Output from Open Specy.
SpectrumIdentity: Identity of the standard the spectrum matched too. Output from Open Specy.
polymer_class: Polymer class. Output from Open Specy.
plastic_or_not: plastic or not. Output from Open Specy.
match_category_corrected: match category of particle after assessment by analyst.

Associated figures:
- Figures 3, 4, 5

Code/software

.csv should be able to be opened by many software types

Field methods

Fourteen total samples (6 sites in fall, 8 sites in spring) were collected along the Truckee River and analyzed for MP concentration. Additional site descriptions are provided in the supplement. The fall of 2022 was the first sampling period and was characterized by low flows in the Truckee River. Sampling dates were selected based on weather and field conditions to allow for safe sampling, and samples were not collected at all sites for each season. Coordination with the Pyramid Lake Paiute Tribe allowed for sampling to be conducted on the Pyramid Lake Paiute Tribe Reservation.

Sample volumes ranged from 49 to 65 L of Truckee River water, using the method described by Harrold et al. (2022). The sample was taken from the top 3 cm of the water using a steel funnel (4 cm in diameter) connected to silicone tubing (5 m in length) powered by a battery-operated peristaltic pump (SERIES II Geopump, Geotech, Colorado, United States). Sample sites were chosen to be consistent across sites, with the goal of sampling an unobstructed part of the river. The funnel was positioned so that it faced upstream into the direction of flow. Samples were collected by pumping river water through the tubing and into a 25 mm diameter, 100 µm pore size, stainless steel mesh (TWP, United states) inline filter housed in a polypropylene filter housing (Millipore, United States). Although the minimum mesh size of the filter was 100 µm, the smallest particles collected measured < 50 µm by < 50 µm. The volume of water sampled was measured using a bucket with 5 L increments.

Before the filter housing was attached to the silicone tubing, the tubing was flushed with 5 L of river water. After 49 to 65 L of river water were filtered through the housing, 500 mL of 0.5 % micro90 filtered (0.7 µm glass fiber filter) soap solution was pumped to dislodge any particles that may have adhered to the tubing. Following the soap rinse, an additional 4 to 5 L of river water was pumped. Each sample took approximately 2.5 hours to complete.

Laboratory methods

The 100 µm filtered samples underwent wet oxidation to remove organic material. The filter housings were used as reaction vessels for the oxidation, and the filter was submerged in prefiltered (0.7 µm glass fiber filter) 10 % hydrogen peroxide (H₂O₂). This procedure was conducted twice for 24 hours each at room temperature (~23 °C). After the H₂O₂ treatments, the housings were drained and rinsed with purified water (Elga water purifier, US). The 100 µm filter was stored in a covered aluminum dish and dried overnight at 40 °C.

If sediment particles overwhelmed the filter, a density separation step was performed to remove the sediment. All filters from the spring of 2023, other than the sample from site 2, required density separation. Our density separation procedure consisted of two steps and was based on the methods of Cashman et al. (2022). Briefly, filters were rinsed into a small beaker using a prefiltered (0.7 µm glass fiber filter) 1.3 g/mL solution of sodium bromide (NaBr) with a pipette. The beaker of particles and NaBr was stirred. After at least 2 hours, the floating particles were collected using a pipette and filtered onto a 100 mm stainless steel filter. Next, a prefiltered (0.7 µm glass fiber filter) 1.5 g/mL solution of NaBr was added to the beaker of remaining particles, and the floating particles were immediately pipetted and filtered. The beaker was filled with additional 1.5 g/mL NaBr and allowed to rest overnight. The next day, the floating particles were filtered, the filter was stored in an aluminum dish and dried overnight at 40 ºC.

Spectroscopy

The particles on the filters were chemically identified using a ThermoFisher Nicolet™ iN10 MX microscope-enabled Fourier Transform Infrared spectroscopy (µFTIR) instrument in transmission mode. First, particles on the filters were counted using an optical microscope (Leica S9i) at 2X magnification to determine the method of µFTIR analysis. If < 400 particles were counted on the filters, the µFTIR spectra for each particle were collected. If 401 to 2,000 particles were counted, then 20 % of the particles on the filter were randomly selected for analysis using a random location approach, by generating random points in ArcMAP (V10.8.1). During µFTIR sample analysis, we navigated to the particle nearest the selected coordinate and collected the spectra. If > 2,000 particles were counted on the filter, 10 % of the particles were randomly sampled using the same random location approach.

Data collection was conducted using the µFTIR’s OMNIC software with a liquid-nitrogen-cooled MCT detector. The spectra were collected using spectral resolution of 8 cm ^-1 (from 4000 to 715 cm ^-1). The Norton-Beer strong apodization function was applied by the instrument software. Each particle was collected using an aperture of 100 µm x 100 µm. While collecting particle spectra, qualitative data such as length, width, color, and morphology were also collected by the analyst. Morphology was limited to fragments, films, and fibers/filaments. Spectra collected by the instrument’s software were exported and processed in the R package “OpenSpecy” (Cowger et al 2021). Spectra processing included region flattening to remove the CO₂ interference peak from 2200-2400 cm ^-1. To process the spectra, the absolute derivative transformation of the first order was conducted, and the data were smoothed using a polynomial order 3 and a moving window of 11 data points (88 cm ^-1). A signal-to-noise threshold of 4 was also applied, using the signal over noise technique (Cowger et al 2021). Spectra were compared to the OpenSpecy FTIR derivative library, and threshold correlation minimum value of 0.70. Matches were manually verified by the analyst. Particles identified as plastics were then summed for each site, scaled as necessary for the proportion of particles analyzed, and divided by the volume of water for each sample. This resulted in an MP count per liter (MP/L) of water.

Quality control

To minimize sample contamination, the filters were prepared in a HEPA-filtered laboratory facility. All reagents were also prepared in the HEPA-filtered laboratory facility and were filtered prior to use. Orange-dyed cotton lab coats were worn when in the laboratory and in the field so that any potential lab coat contamination was easily identifiable. In the field, researchers positioned themselves downstream and downwind of the funnel to minimize airborne MP contamination of the samples. Samples were always kept covered and upright when not in use. Four field blanks and two lab blanks were collected and processed with all the other samples. The blanks were processed in the same manner as sampled and analyzed with µFTIR.

Blank correction

Blank corrections were performed using a combination of methods suggested in Dawson et al. (2023) and Lao and Wong (2023) to calculate a minimum detectable amount (MDA) from the blanks. An MDA was calculated for each polymer type of each morphology type from the blanks. The MDA was then subtracted from the uncorrected MP/L.

References

Cashman, M.A., Langknecht, T., El Khatib, D., Burgess, R.M., Boving, T.B., Robinson, S. and Ho, K.T., 2022. Quantification of microplastics in sediments from Narragansett Bay, Rhode Island USA using a novel isolation and extraction method. Marine pollution bulletin, 174, p.113254.

Cowger, W., Steinmetz, Z., Gray, A., Munno, K., Lynch, J., Hapich, H., Primpke, S., De Frond, H., Rochman, C. and Herodotou, O., 2021. Microplastic spectral classification needs an open source community: open specy to the rescue!. Analytical chemistry, 93(21), pp.7543-7548.

Dawson, A.L., Santana, M.F., Nelis, J.L. and Motti, C.A., 2023. Taking control of microplastics data: a comparison of control and blank data correction methods. Journal of Hazardous Materials, 443, p.130218.

Harrold, Z., Arienzo, M.M., Collins, M., Davidson, J.M., Bai, X., Sukumaran, S. and Umek, J., 2022. A peristaltic pump and filter-based method for aqueous microplastic sampling and analysis. ACS ES&T Water, 2(2), pp.268-277.

Lao, W. and Wong, C.S., 2023. How to establish detection limits for environmental microplastics analysis. Chemosphere, 327, p.138456.

Large seasonal variation in microplastic concentration from the Truckee River, United States

Data files

Abstract

README: Large seasonal variation in microplastic concentration from the Truckee River, United States

Description of the data and file structure

Files and variables

File: Filter_info.csv

Variables

File: Top_Matches_Truckee_9b_Mustang_Apr2423_100umSF_derivative_T0.7_results.csv

Variables

Associated figures in corresponding manuscript:

File: Top_Matches_Truckee_10_Wadsworth_May0423_100umSFR_derivative_T0.7_results.csv

Variables

Associated figures:

File: TR_MDA_Blanks.csv

Variables

File: Top_Matches_Truckee_4_Verdi_May0523_100umSFR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_3_Glenshire_Nov0422_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_3_Glenshire_Apr1923_100umSFR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_2_A1_Apr2623_100umS_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_8_Lockwood_Apr2123_100umSFR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_4_Verdi_Nov_100umS_101923_1to132_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_5_Mayberry_Oct2622_100umS_1to92_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_9a_Mustang_Apr2423_100umSR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_7_DownWWTP_Apr1823_100umSFR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_6b_RockPark_Apr1123_100umSF_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_6a_RockPark_Apr1123_100umSR_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_9_Mustang_Nov1022_100um_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_6_RockPark_Dec0222_100um_derivative_T0.7_results.csv

Variables

Associated figures:

File: Top_Matches_Truckee_7_WWTPDown_Nov1122_100umS_1to107_derivative_T0.7_results.csv

Variables

Associated figures:

Code/software

Methods

Field methods

Laboratory methods

Spectroscopy

Blank correction

References

Change log