Dissolved organic matter, water quality, water isotopes, and discharge measurements of the Tapajós River, Brazil from 2016-2023
Project
| Contributors | Affiliation | Role |
|---|---|---|
| Kurek, Martin | Florida State University (FSU) | Co-Principal Investigator |
| Spencer, Robert | Florida State University (FSU) | Co-Principal Investigator |
| Holmes, Robert Max | Woodwell Climate Research Center | Scientist |
| McKenna, Amy | Florida State University - National High Magnetic Field Lab (FSU - NHMFL) | Scientist |
| Moura, José Mauro | Federal University of Western Pará (UFOPA) | Scientist |
| Muniz, Rafael | Federal University of Western Pará (UFOPA) | Scientist |
| Peucker-Ehrenbrink, Bernhard | Woods Hole Oceanographic Institution (WHOI) | Scientist |
| York, Amber D. | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
Abstract
Water samples were collected near‐monthly from the Tapajós River upstream of Itaituba Brazil (-4.3375,-56.06953). Three water samples (1 L) were collected at 0.5 m depth from the river across the channel in equal spacing and combined into a 4 L acid‐washed carboy to make a composite sample. The water was filtered through a 0.45 μm capsule filter with a peristaltic pump into acid‐rinsed high‐density polyethylene (HDPE) bottles. Filtered samples were kept cold during transport and immediately frozen upon transfer to the laboratory and kept in the dark until analysis. Samples for water isotope analysis were collected in 30 mL HDPE bottles that were filled to capacity, free of air, and stored in a dark, cool place prior to analysis.
EEMs were corrected for lamp intensity, inner filter effects, and normalized to Raman units. Parallel factor analysis
(PARAFAC) was modeled in MATLAB with the drEEM toolbox for 81 individual EEMs and validated using core consistency diagnostics and splithalf validation , yielding a 5‐component model that explained 99.93% of the variance.
Mass spectral peaks (>6σ root‐mean‐square (RMS) baseline noise) were exported to a peak list and processed using PetroOrg. Molecular formulae were assigned to ions constrained by C4‐75H4‐150O1‐30N0‐4S0‐2 not exceeding 300 ppb error.
Water isotope data post‐processing included amount‐linearity correction for OA‐ICOS data, memory correction and normalization to the VSMOW‐SLAP scale using LIMS for Lasers 2015.
* Sheet 1 of submitted file "Tapajos_ds1_02-12-25.xlsx" was imported into the BCO-DMO data system for this dataset. Table will appear as Data File: 986798_v1_tapajos_dom.csv (along with other download format options).
* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores. Can not start with a number]. Column name dH changed to d2H for clarity as that was how it was described, as d2H (delta2H).
* Date converted to ISO 8601 format
* Location field contained both latitude and longitude in degrees minutes and seconds (e.g. '"4°20'15.0"S 56°04'10.3"W"') which was converted to separate lat_dd lon_dd columns (also converted to decimal degrees)
Relationship Description: Related datasets from the same study published in Kurek et al. (2025, doi: 10.1029/2025GB008545).
Relationship Description: Related datasets from the same study published in Kurek et al. (2025, doi: 10.1029/2025GB008545).
| Parameter | Description | Units |
| Sample_Name | Discrete sample name | unitless |
| Date | Sampling date | unitless |
| Date_ISO | Sampling date in ISO 8601 format | unitless |
| lat_dd | Sampling site latitude | decimal degrees |
| lon_dd | Sampling site longitude | decimal degrees |
| Discharge_on_sampling_day | River discharge on sampling day | cubic meters per second (m3 s-1) |
| Mean_monthly_discharge | Mean monthly river discharge | cubic meters per second (m3 s-1) |
| Mean_daily_air_temp | Mean daily air temperature | degrees Celsius (degC) |
| Daily_precipitation | Daily precipitation | millimeters (mm) |
| Mean_monthly_air_temp | Mean monthly air temperature | degrees Celsius (degC) |
| Monthly_precipitation | Monthly total precipitation | millimeters (mm) |
| DOC | Dissolved Organic Carbon concentration | milligrams per liter (mg L-1) |
| FI | Fluorescence Index | unitless |
| a350 | Naperian absorbance at 350 nm (m-1, Naperian) | per meter (m-1) |
| S275_to_295 | Spectral slope from 275-295 nm | per nanometer (nm-1) |
| S350_to_400 | Spectral slope from 350-400 nm | per nanometer (nm-1) |
| SUVA254 | Specific UV absorbance at 254 nm (L mg C-1 m-1) | liters per milligram carbon per meter (L mg C-1 m-1) |
| perc_CHO | Percent CHO-containing molecular formulae (% relative abundance) | percent (%) |
| perc_CHON | Percent CHOn-containing molecular formulae (% relative abundance) | percent (%) |
| perc_CHOS | Percent CHOS-containing molecular formulae (% relative abundance) | percent (%) |
| perc_CHONS | Percent CHONS-containing molecular formulae (% relative abundance) | percent (%) |
| perc_CA | Percent condensed aromatic molecular formulae (% relative abundance) | percent (%) |
| perc_PPh | Percent polyphenolic molecular formulae (% relative abundance) | percent (%) |
| low_OC_HUP_perc | Percent highly unsaturated and phenolic (low O/C) molecular formulae (% relative abundance) | percent (%) |
| high_OC_HUP_perc | Percent highly unsaturated and phenolic (high O/C) molecular formulae (% relative abundance) | percent (%) |
| high_OC_Ali_perc | Percent aliphatic (high O/C) molecular formulae (% relative abundance) | percent (%) |
| low_OC_Ali_perc | Percent aliphatic (low O/C) molecular formulae (% relative abundance) | percent (%) |
| Assigned_formulae | Number of assigned molecular formulae | unitless |
| RMS_Error | Root mean squared error or assigned molecular formulae | unitless |
| Mass | Measured mass | daltons (Da) |
| H_to_C | H atoms/C atoms (abundance weighted average) | unitless |
| O_to_C | O atoms/C atoms (abundance weighted average) | unitless |
| N_to_C_x1000 | N atoms/C atoms (abundance weighted average x1000) | unitless |
| S_to_C_x1000 | S atoms/C atoms (abundance weighted average x1000) | unitless |
| AImod | Modified aromaticity index (abundance weighted average) | unitless |
| DBE | Double bond equivalents (abundance weighted average) | unitless |
| DBE_C | Double bond equivalents/C atoms (abundance weighted average) | unitless |
| NOSC | Nominal oxidation state of C (abundance weighted average) | unitless |
| perc_IOS | Percent of Island of Stability formulae (% relative abundance) | percent (%) |
| Water_temp | Water temperature | degrees Celsius (degC) |
| SpC | Specific Conductivity | microSiemens per centimeter (uS cm-1) |
| O2sat | Dissolved oxygen (% saturation) | percent (%) |
| O2 | Dissolved oxygen concentration (mg L-1) | milligrams per liter (mg L-1) |
| pH | pH | pH scale |
| FDOM | Total fluorescence of identified peak maxima (Relative Fluorescence Units) | relative fluorescence units (RFU) |
| C1 | Percentage of fluorescence component 1 from the PARAFAC model | percent (%) |
| C2 | Percentage of fluorescence component 2 from the PARAFAC model | percent (%) |
| C3 | Percentage of fluorescence component 3 from the PARAFAC model | percent (%) |
| C4 | Percentage of fluorescence component 4 from the PARAFAC model | percent (%) |
| C5 | Percentage of fluorescence component 5 from the PARAFAC model | percent (%) |
| d2H | d2H (delta2H) of River water | per mil (0/00) |
| d18O | d18O (delta18O) of River water | per mil (0/00) |
| D_excess | Deuterium excess of River water | per mil (0/00) |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | Fourier Transform Ion Cyclotron Resonance Mass Spectrometer |
| Dataset-specific Description | Solid phase extracted water samples were analyzed on a custom‐built hybrid linear ion trap ultra‐high resolution FT‐ICR mass spectrometer equipped with a 21T superconducting solenoid magnet at the National High Magnetic Field Laboratory (Tallahassee, FL). Negatively charged ions from DOM were produced via electrospray ionization (ESI) at a flow rate of 500 nL min-1 via a syringe pump. Typical conditions for ion formation included: emitter voltage, -2.8–3.2 kV; S‐lens RF level, 40%; and heated metal capillary temperature, 350 degrees C. |
| Generic Instrument Description | In Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, the mass-to-charge ratio (m/z) of an ion is experimentally determined by measuring the frequency at which the ion processes in a magnetic field. These frequencies, which are typically in the 100 KHz to MHz regime, can be measured with modern electronics making it possible to determine the mass of an ion to within +/- 0.000005 amu or 5 ppm. |
| Dataset-specific Instrument Name | Horiba Scientific Aqualog (Horiba Ltd., Kyoto, Japan) |
| Generic Instrument Name | Horiba Aqualog spectrofluorometer |
| Dataset-specific Description | UV‐visible absorbance spectra were measured at room temperature in a 1‐cm quartz cuvette with a Horiba Scientific Aqualog (Horiba Ltd., Kyoto, Japan) at wavelengths of 230–800 nm.
Excitation‐Emission matrices (EEMs) from fluorescence spectra were measured at room temperature in a 1‐cm quartz cuvette using a Horiba Scientific Aqualog (Horiba Ltd., Kyoto, Japan). EEMs were collected at 250– 500 nm excitation wavelengths and 300–600 nm emission wavelengths with 5 and 2 nm intervals, respectively, at integration times ranging from 3 to 6s. |
| Generic Instrument Description | A benchtop optical spectrometer suitable for measuring coloured dissolved organic matter (CDOM). Outputs include absorbance spectra, fluorescence emission spectra, and fluorescence excitation-emission matrices. This instrument simultaneously measures absorbance spectra and fluorescence Excitation-Emission Matrices. It employs the Absorbance-Transmission Excitation Emission Matrix (A-TEEM) technique to acquire an Excitation Emission Matrix. |
| Dataset-specific Instrument Name | dual‐isotope Cavity Ringdown Spectroscopy (CRDS, 2130i/2140i, Picarro Inc., USA) |
| Generic Instrument Name | Picarro L2130-I deltaD/delta18O Isotopic Water Analyzer |
| Dataset-specific Description | For water samples up to sampling dates of August 2017, analyses were conducted in replicate by Off‐Axis Integrated Cavity Output Spectroscopy (OA‐ICOS, TLWIA 45EP, Los Gatos Inc., USA) with nine injections per sample vial of which five were accepted. The later batch was analyzed, again in replicate, via dual‐isotope Cavity Ringdown Spectroscopy (CRDS, 2130i/2140i, Picarro Inc., USA) with six injections per vial (three accepted). |
| Generic Instrument Description | A portable analyser designed for laboratories or field based isotope analysis. It uses Cavity Ring-Down Spectroscopy (CRDS) to measure the spectral signature of the molecule of interest. The instrument includes a closed-loop temperature and pressure control. The L2130-i can be used in all aspects of the water cycle: water vapor, liquid water, or water trapped in solids. It has a typical precision of 0.25 per mil for d18O and 1.20 per mil for dD in solid samples. Corresponding typical values for liquid samples are 0.011 per mil for d18O and 0.038 per mil for dD. |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | Shimadzu TOC-L Analyzer |
| Dataset-specific Description | Filtered water samples were acidified (HCl, pH 2) and DOC concentrations were measured with a Shimadzu TOC‐L CPH high temperature catalytic oxidation total organic carbon analyzer (Shimadzu Corp., Kyoto, Japan). |
| Generic Instrument Description | A Shimadzu TOC-L Analyzer measures DOC by high temperature combustion method.
Developed by Shimadzu, the 680 degree C combustion catalytic oxidation method is now used worldwide. One of its most important features is the capacity to efficiently oxidize hard-to-decompose organic compounds, including insoluble and macromolecular organic compounds. The 680 degree C combustion catalytic oxidation method has been adopted for the TOC-L series.
http://www.shimadzu.com/an/toc/lab/toc-l2.html |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | YSI Professional Plus Multi-Parameter Probe |
| Dataset-specific Description | In situ water temperature, dissolved oxygen (DO), specific conductivity (SpC), and pH were measured in the center of the river channel at 0.5 m depth with a calibrated YSI Professional Plus multimeter. |
| Generic Instrument Description | The YSI Professional Plus handheld multiparameter meter provides for the measurement of a variety of combinations for dissolved oxygen, conductivity, specific conductance, salinity, resistivity, total dissolved solids (TDS), pH, ORP, pH/ORP combination, ammonium (ammonia), nitrate, chloride and temperature. More information from the manufacturer. |
RAPID: El Nino Event Impacts on Organic Matter Export and Composition in the Amazon River (ENSO impact on Amazon River DOC and DOM)
NSF Award Abstract:
The Amazon River is one of the largest sources of freshwater and carbon to the ocean. Thus, understanding the factors that influence freshwater delivery from the Amazon River is important for understanding the carbon cycle of the Amazon River and the receiving Atlantic Ocean. El Niño–Southern Oscillation (ENSO) is a periodic event that causes changes in winds and sea surface temperature over the tropical eastern Pacific Ocean and affects climate in the tropics and subtropics. The National Weather Service predicts that El Niño conditions are likely to form across the Pacific during Summer 2023. These conditions are expected to last through February 2024. This event is expected to impact precipitation and air temperatures in the Amazon Basin and freshwater delivery from the Amazon River. This project aims to study the amount and chemical composition of dissolved organic carbon delivered from the Amazon River to the Atlantic Ocean during the 2023-2024 El Niño event. Scientists involved in this project plan to collect samples from late Summer 2023 through late Summer 2024. The study will identify conditions before, during and after this event. This unique set of samples will enable the team of scientists to study how ENSO influences the delivery of organic carbon to the coastal ocean.
This project provides support for an early career researcher and promotes international cooperation and inclusivity between researchers from the United States of America and researchers in Brazil who are directly impacted by the changing Amazon River.
This project examines how El Niño Southern Oscillation (ENSO) anomalies impact the export of dissolved organic carbon (DOC) and composition of dissolved organic matter (DOM) from the Amazon River to the Atlantic Ocean. Based on recent studies, it has been hypothesized that the upcoming 2023 El Niño event will reduce the annual DOC flux and proportion of exported terrestrial DOM from the Amazon River compared to non-ENSO and La Niña years. This hypothesis will be examined by linking established state-of-the-art optical and molecular-level characterization techniques (e.g., Fourier-transform ion cyclotron resonance mass spectrometry; FT-ICR MS) with DOC flux calculations over the course of an El Niño year. Analyzing both bulk DOC fluxes and the molecular-level composition will reveal how the quantity and quality of DOM export will change monthly in response to reduced precipitation and higher temperature across the Amazon Basin and headwaters. DOC fluxes as well as detailed characterizations (FT-ICR MS, optical, fluorescence analysis) of DOM sampled from the furthest downstream Amazon River gauging station at Óbidos (Brazil) will be directly compared to results obtained from the 2011-2012 La Niña year and the following 2012-2013 hydrologically normal year to determine how global climate anomalies impact the DOC export to marine systems and to create a framework for future predictions. Data obtained from this proposed study will lay the foundations for larger studies investigating how ENSO cycles impact discharge and carbon export from other major tropical-subtropical rivers and ultimately, how ENSO cycles impact global land-ocean carbon export.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
| Funding Source | Award |
|---|---|
| NSF Division of Ocean Sciences (NSF OCE) |
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