The sampling of 41 hydrologically diverse rivers that are monitored through the National Water Quality Network (NWQN) by the U.S. Geological Survey (USGS) took place during the water years of 2008 through 2018. Water samples were collected and filtered in the field (unless otherwise noted) using 0.45 micrometer pre-rinsed capsule filters (Versapor membrane), silicon tubing, and a peristaltic pump. Water samples were then shipped on ice to the USGS in Boulder, Colorado and chilled to approximately 4 to 6 degrees Celsius until analysis. Dissolved organic carbon (DOC) was measured on an OI700 Analytical total organic carbon analyzer by wet-oxidation; each sample was measured in replicate and the average was reported. Ultraviolet (UV) absorbance at the wavelength of 254 nanometers was measured with an Agilent HP8453 UV-visible spectrophotometer. Specific UV Absorbance (SUVA) at 254 nanometers is a calculated parameter defined as the UV absorbance at a wavelength of 254 nanometers in absorbance units per centimeter divided by the DOC concentration in milligram per liter and then multiplied by 100. SUVA at 254 nanometers is reported in units of liter per milligram carbon per meter and correlates with the percent aromatic carbon of the dissolved organic matter (DOM). Iron(III) absorbs light in the UV spectrum and, if present at appreciable concentration, can influence UV absorbance values at 254 nanometers and calculated SUVA values. For sites believed to exhibit iron(III) concentrations sufficient for the UV absorbance at 254 nanometers of the DOM to be influenced, the filter-passing total iron concentrations of whole water samples were determined using a Hach spectrophotometer and FerroVer method. SUVA values were calculated using iron(III)-corrected UV absorbance at 254 nanometers for samples that were determined to have filter-passing total iron concentrations greater than 0.02 milligram per liter. Utilizing the UV-visible absorbance spectral scans, spectral slopes at wavelengths 275 to 295 nanometers and at wavelengths 350 to 400 nanometers were determined. The spectral slope ratio is a calculated parameter defined as the spectral slope at wavelengths 275 to 295 nanometers divided by the spectral slope at wavelengths 350 to 400 nanometers. Fluorescence measurements were made on a Jobin-Yvon Horiba Fluoromax-3 fluorometer. Fluorescence measurements included the wavelength of peak emission intensity at 370 nanometers excitation and the fluorescence index (FI). FI is defined as the ratio of fluorescence emission at 470 nanometers divided by 520 nanometers at excitation 370 nanometers. Additional fluorescence indices determined included the humification index (HIX) and the freshness index (β:α). Humification index values increase with the proportion of humic substances. The humification index is defined as the area under the emission spectrum from 435 to 480 nanometers divided by the summation of areas under the emission spectrum at 300 to 345 nanometers and 435 to 480 nanometers, at an excitation of 254 nanometers. The freshness index increases with the proportion of recently produced DOM and is defined as the intensity of fluorescence emission at 380 nanometers divided by the maximum fluorescence emission intensity between 420 and 435 nanometers at excitation 310 nanometers. DOM was separated into fractions by an isolation method that passes aqueous sample at pH < 2 sequentially through Amberlite XAD8 and XAD4 resins using low pressure liquid chromatography. The hydrophobic organic acid (HPOA) fraction is the eluate from the XAD8 fractionation column, and the transphilic organic acid (TPIA) fraction is the eluate from the XAD4 fractionation column. The hydrophilic organic (HPI) fraction is the effluent of the sample passed sequentially through the XAD8 and XAD4 fractionation columns. The hydrophobic organic neutral (HPON) fraction is that retained on the XAD8 column after passing the sample through at pH < 2 and back eluting with

The sampling of the riverine-to-marine transect (Penobscot River, Penobscot Bay, and the Gulf of Maine) took place in 2008. Water samples were collected and filtered in the field using 0.45 micrometer capsule filters (Versapor membrane), silicon tubing, and a peristaltic pump. Water samples were then shipped on ice to the U.S. Geological Survey in Boulder, Colorado and chilled to approximately 4 degrees Celsius until analysis. Dissolved organic matter (DOM) was separated into fractions by an isolation method that passes aqueous sample through Amberlite XAD8 and XAD4 resins using low pressure liquid chromatography. The hydrophobic organic acid (HPOA) fraction is the eluate from the XAD8 fractionation column and the transphilic organic acid (TPIA) fraction is the eluate from the XAD4 fractionation column. Dissolved organic carbon (DOC) was either analyzed on a Shimadzu TOC-Vcph total organic carbon analyzer by combustion-infrared or an OI700 Analytical total organic carbon analyzer by wet-oxidation; each sample was measured in replicate and the average was reported. Ultraviolet (UV) absorbance at the wavelength of 254 nm was measured with an Agilent HP8453 UV-Vis spectrophotometer. Specific UV Absorbance (SUVA) at 254 nm is a calculated parameter defined as the UV absorbance at a wavelength of 254 nm in absorbance units per centimeter divided by the DOC concentration in milligrams per liter and then multiplied by 100. SUVA 254 nm is reported in units of liters per milligram carbon per meter and correlates with the percent aromatic carbon of the DOM. Associated laboratory quality assurance and quality control measures have been taken to produce final data.

This dataset provides measurements of particulate organic carbon (POC) concentrations made on water samples collected during 2021 in surface waters of the Atchafalaya River and Terrebonne Basins, portions of the Mississippi River Delta in coastal Louisiana. Water samples were collected at ~0.5 m depth from surface during the spring (2021-03-25 to 2021-04-22) and fall (2021-08-14 to 2021-09-24) field efforts. Field sampling was paused on August 25 and resumed on September 13 due to the landfall of Hurricane Ida on 2021-08-26 approximately 70 km east of the study sites. Water quality changes in this dataset caused by the hurricane are expected to be minimal. Samples were collected in multiple channels of varying width (from a few meters to >100 m) near Delta-X intensive study sites, in open bays and lakes, and a few locations in the nearshore Gulf of Mexico. For each sample, the water sample volume was filtered (in triplicate) through 25-mm glass microfiber (GF/F) filters to retain the suspended particles. The amount of organic carbon retained on each filter was measured using an elemental carbon, hydrogen and nitrogen (CHN) analyzer and normalized by the volume of sample water filtered. The reported values in this dataset include the mean and standard deviation of POC measurements from three replicate samples collected at each site.

This dataset contains historical data on concentrations of total and dissolved organic carbon in Massachusetts streams from the U.S. Geological Survey National Water Information System (NWIS) database. The data were compiled from NWIS using site and sample selection criteria to retrieve all publicly available data from surface-water samples that contained analysis of both total and dissolved organic carbon. The data set was screened, as much as possible from the site and sample description information in NWIS, to retain only routine environmental samples from stream sites. The final data set consists of 223 samples from 52 sites and were collected from 1978 to 2007.

This dataset contains historical data on concentrations of total and dissolved organic carbon in Massachusetts streams from the U.S. Geological Survey National Water Information System (NWIS) database. The data were compiled from NWIS using site and sample selection criteria to retrieve all publicly available data from surface-water samples that contained analysis of both total and dissolved organic carbon. The data set was screened, as much as possible from the site and sample description information in NWIS, to retain only routine environmental samples from stream sites. The final data set consists of 223 samples from 52 sites and were collected from 1978 to 2007.

This dataset contains measurements of water quality parameters (temperature, salinity, specific conductance, dissolved oxygen, and pH) and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) in canals of Jean Lafitte National Historical Park and Preserve (hereafter, the Park) during wet and dry seasons in 2022 and 2023. Four field campaigns were conducted on April 26, 2022, October 27, 2022, March 1, 2023, and August 3, 2023, covering pre-, during, and post-canal backfilling construction in the Park. Data can also be found at USGS National Water Information System (NWIS, https://waterdata.usgs.gov/nwis/sw).

This dataset contains measurements of water quality parameters (temperature, salinity, specific conductance, dissolved oxygen, and pH) and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) in canals of Jean Lafitte National Historical Park and Preserve (hereafter, the Park) during wet and dry seasons in 2022 and 2023. Four field campaigns were conducted on April 26, 2022, October 27, 2022, March 1, 2023, and August 3, 2023, covering pre-, during, and post-canal backfilling construction in the Park. Data can also be found at USGS National Water Information System (NWIS, https://waterdata.usgs.gov/nwis/sw).

This dataset provides measurements of particulate organic carbon (POC) concentrations made on water samples collected during 2021 in surface waters of the Atchafalaya River and Terrebonne Basins, portions of the Mississippi River Delta in coastal Louisiana. Water samples were collected at ~0.5 m depth from surface during the spring (2021-03-25 to 2021-04-22) and fall (2021-08-14 to 2021-09-24) field efforts. Field sampling was paused on August 25 and resumed on September 13 due to the landfall of Hurricane Ida on 2021-08-26 approximately 70 km east of the study sites. Water quality changes in this dataset caused by the hurricane are expected to be minimal. Samples were collected in multiple channels of varying width (from a few meters to >100 m) near Delta-X intensive study sites, in open bays and lakes, and a few locations in the nearshore Gulf of Mexico. For each sample, the water sample volume was filtered (in triplicate) through 25-mm glass microfiber (GF/F) filters to retain the suspended particles. The amount of organic carbon retained on each filter was measured using an elemental carbon, hydrogen and nitrogen (CHN) analyzer and normalized by the volume of sample water filtered. The reported values in this dataset include the mean and standard deviation of POC measurements from three replicate samples collected at each site.

This product consists of one tabular dataset and associated metadata of water quality information related to rivers, streams, and reservoirs in the Upper Mississippi River watershed between 2012 and 2016. This data release is apart of a national assessment of freshwater aquatic carbon fluxes. Data consist of organic and inorganic carbon related species, carbon dioxide and methane gas fluxes calculated from manual chamber measurements, nitrogen species, carbon isotopes, oxygen isotopes, cations, anions, trace metals, and various in situ measurements including: pH, water temperature, air temperature, barometric pressure, dissolved oxygen, turbidity, fluorescent dissolved organic matter, and specific conductance. Sampling frequency varied across locations, with individual sites being sampled either once or on a quarterly basis.