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.

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

This dataset contains dissolved inorganic carbon, Total alkalinity, pH on Total Scale, nutrients and other variables measured from profile discrete measurement in the Northeast coast of the US. Increasing amounts of atmospheric carbon dioxide from human industrial activities are causing changes in global ocean carbon chemistry resulting in a reduction in pH, a process termed ocean acidification. Studies have demonstrated adverse effects on calcifying organisms, particularly some invertebrates, corals, sea urchins, pteropods, and coccolithophores. This effort is in support of the coastal monitoring and research objectives of the NOAA Ocean Acidification Program (OAP).

This metadata record contains 6 tables used to assess sources of Polychlorinated Biphenyls (PCB) in the Back River watershed, Baltimore City, Maryland. Included in the dataset are PCB concentrations of surface water and porewater passive samplers from Herring Run, Moores Run, tidal Back River, and Back River Wastewater Treatment Plant; PCB concentrations of bed sediments and other solids, Fat, Oil, and Grease (FOG) samples, and road sediments; dissolved organic carbon (DOC), total suspended solids (TSS), and particulate organic carbon (POC) concentrations of grab samples; and PCB concentrations of passive samplers from pump stations collected in 2018-2020.

Continuous water quality sensor data were collected at USGS 292939089544400 Wilkinson Bayou cutoff north of Wilkinson Bay, LA gage. Field water quality measurements were collected using a YSI EXO2 water quality sonde equipped with a data logger to capture hourly data using sensors for measuring water temperature, specific conductance, salinity, pH, oxidation and reduction potential (ORP), fluorescent dissolved organic matter (fDOM), turbidity, and dissolved oxygen (DO). The monitor was housed in an 8-inch diameter polyvinyl chloride (PVC) pipe attached to a temporary wooden structure near the gage. Measurements were collected from a fixed mid-depth point in the water column. All data were collected using U.S. Geological Survey (USGS) protocols and data are stored in the National Water Information System (NWIS) database. Records processing of measurement results for fouling and drift corrections of the data followed the USGS Techniques and Methods for continuous water-quality monitors (Wagner et al., 2006), except for ORP and drift corrections for fDOM. ORP were uncorrected and were reported from the sonde directly. fDOM was evaluated for drift using periodic side-by-side comparisons with a new factory-calibrated sensor to check for lamp degradation in the sensor, and calibration checks were performed using on-site prepared fDOM standard. fDOM data have not been corrected for temperature, turbidity, or inner-filter effects (Booth et al., 2023). Turbidity drift corrections were applied using Wagner et al. (2006) except in some cases where it was determined not helpful to apply the correction based on unstable site conditions during the site visit. Sample results from June of 2022 to October 2023 are reported in this data release. References: Booth, A., Fleck, J., Pellerin, B.A., Hansen, A., Etheridge, A., Foster, G.M., Graham, J.L., Bergamaschi, B.A., Carpenter, K.D., Downing, B.D., Rounds, S.A., and Saraceno, J., 2023, Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting: U.S. Geological Survey Techniques and Methods, book 1, chap. D11, 41 p., https://doi.org/10.3133/tm1D11. Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1–D3, 51 p. + 8 attachments; accessed August 3, 2022, at https://pubs.usgs.gov/tm/2006/tm1D3/pdf/TM1D3.pdf.

Continuous water quality sensor data were collected at USGS 292939089544400 Wilkinson Bayou cutoff north of Wilkinson Bay, LA gage. Field water-quality measurements were collected using a YSI EXO2 water-quality sonde equipped with a data logger to capture hourly data using sensors for measuring water temperature, specific conductance, salinity, pH, oxidation and reduction potential (ORP), fluorescent dissolved organic matter (fDOM), and turbidity. The monitor was housed in an 8-inch diameter polyvinyl chloride (PVC) pipe attached to a temporary wooden structure near the gage. Measurements were collected from a fixed mid-depth point in the water column. All data were collected using U.S. Geological Survey (USGS) protocols and data are stored in the National Water Information System (NWIS) database. Records processing of measurement results for fouling and drift corrections of the data followed the USGS Techniques and Methods for continuous water-quality monitors (Wagner, et al., 2006), except for ORP and drift corrections for fDOM. ORP were uncorrected and were reported from the sonde directly. fDOM was evaluated for drift using periodic side by side comparisons with a new factory calibrated sensor to check for lamp degradation in the sensor and calibration checks were performed using onsite prepared fDOM standard. fDOM data have not been corrected for temperature, turbidity, or inner-filter effects (Booth et al., 2023). Turbidity drift corrections were applied using Wagner et al. (2006) except in some cases where it was determined not helpful to apply the correction based on unstable site conditions during the site visit. Sample results from July of 2019 to May 2022 are reported in this data release. Booth, A., Fleck, J., Pellerin, B.A., Hansen, A., Etheridge, A., Foster, G.M., Graham, J.L., Bergamaschi, B.A., Carpenter, K.D., Downing, B.D., Rounds, S.A., and Saraceno, J., 2023, Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting: U.S. Geological Survey Techniques and Methods, book 1, chap. D11, 41 p., https://doi.org/10.3133/tm1D11. Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1–D3, 51 p. + 8 attachments; accessed August 3, 2022, at https://pubs.usgs.gov/tm/2006/tm1D3/pdf/TM1D3.pdf.

Continuous water quality sensor data were collected at USGS 292939089544400 Wilkinson Bayou cutoff north of Wilkinson Bay, LA gage. Field water-quality measurements were collected using a YSI EXO2 water-quality sonde equipped with a data logger to capture hourly data using sensors for measuring water temperature, specific conductance, salinity, pH, oxidation and reduction potential (ORP), fluorescent dissolved organic matter (fDOM), and turbidity. The monitor was housed in an 8-inch diameter polyvinyl chloride (PVC) pipe attached to a temporary wooden structure near the gage. Measurements were collected from a fixed mid-depth point in the water column. All data were collected using U.S. Geological Survey (USGS) protocols and data are stored in the National Water Information System (NWIS) database. Records processing of measurement results for fouling and drift corrections of the data followed the USGS Techniques and Methods for continuous water-quality monitors (Wagner, et al., 2006), except for ORP and drift corrections for fDOM. ORP were uncorrected and were reported from the sonde directly. fDOM was evaluated for drift using periodic side by side comparisons with a new factory calibrated sensor to check for lamp degradation in the sensor and calibration checks were performed using onsite prepared fDOM standard. fDOM data have not been corrected for temperature, turbidity, or inner-filter effects (Booth et al., 2023). Turbidity drift corrections were applied using Wagner et al. (2006) except in some cases where it was determined not helpful to apply the correction based on unstable site conditions during the site visit. Sample results from July of 2019 to May 2022 are reported in this data release. Booth, A., Fleck, J., Pellerin, B.A., Hansen, A., Etheridge, A., Foster, G.M., Graham, J.L., Bergamaschi, B.A., Carpenter, K.D., Downing, B.D., Rounds, S.A., and Saraceno, J., 2023, Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting: U.S. Geological Survey Techniques and Methods, book 1, chap. D11, 41 p., https://doi.org/10.3133/tm1D11. Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1–D3, 51 p. + 8 attachments; accessed August 3, 2022, at https://pubs.usgs.gov/tm/2006/tm1D3/pdf/TM1D3.pdf.

Continuous water quality sensor data were collected at USGS 292939089544400 Wilkinson Bayou cutoff north of Wilkinson Bay, LA gage. Field water-quality measurements were collected using a YSI EXO2 water-quality sonde equipped with a data logger to capture hourly data using sensors for measuring water temperature, specific conductance, salinity, pH, oxidation and reduction potential (ORP), fluorescent dissolved organic matter (fDOM), and turbidity. The monitor was housed in an 8-inch diameter polyvinyl chloride (PVC) pipe attached to a temporary wooden structure near the gage. Measurements were collected from a fixed mid-depth point in the water column. All data were collected using U.S. Geological Survey (USGS) protocols and data are stored in the National Water Information System (NWIS) database. Records processing of measurement results for fouling and drift corrections of the data followed the USGS Techniques and Methods for continuous water-quality monitors (Wagner, et al., 2006), except for ORP and drift corrections for fDOM. ORP were uncorrected and were reported from the sonde directly. fDOM was evaluated for drift using periodic side by side comparisons with a new factory calibrated sensor to check for lamp degradation in the sensor and calibration checks were performed using onsite prepared fDOM standard. fDOM data have not been corrected for temperature, turbidity, or inner-filter effects (Booth et al., 2023). Turbidity drift corrections were applied using Wagner et al. (2006) except in some cases where it was determined not helpful to apply the correction based on unstable site conditions during the site visit. Sample results from July of 2019 to May 2022 are reported in this data release. Booth, A., Fleck, J., Pellerin, B.A., Hansen, A., Etheridge, A., Foster, G.M., Graham, J.L., Bergamaschi, B.A., Carpenter, K.D., Downing, B.D., Rounds, S.A., and Saraceno, J., 2023, Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting: U.S. Geological Survey Techniques and Methods, book 1, chap. D11, 41 p., https://doi.org/10.3133/tm1D11. Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1–D3, 51 p. + 8 attachments; accessed August 3, 2022, at https://pubs.usgs.gov/tm/2006/tm1D3/pdf/TM1D3.pdf.

Seawater samples were collected in Chesapeake Bay for dissolved inorganic carbon (DIC) and total alkalinity (TA) from June 2016 to July 2018. They were collected in the lower half of the Bay aboard the R/V Fay Slover in collaboration with Old Dominion University's Chesapeake Bay Program Water Quality Laboratory and the VA Dept. of Environmental Quality. In the upper half of the Bay, samples were collected aboard the R/V Kerhin in collaboration with the Maryland Department of Natural Resources' Chesapeake Bay Water Quality Monitoring Program. Additional water quality parameters from the cruises were downloaded from the Chesapeake Bay program website. Additional carbonate system parameters were then computed from DIC and TA

Seawater samples were collected in Chesapeake Bay for dissolved inorganic carbon (DIC) and total alkalinity (TA) from June 2016 to July 2018. They were collected in the lower half of the Bay aboard the R/V Fay Slover in collaboration with Old Dominion University's Chesapeake Bay Program Water Quality Laboratory and the VA Dept. of Environmental Quality. In the upper half of the Bay, samples were collected aboard the R/V Kerhin in collaboration with the Maryland Department of Natural Resources' Chesapeake Bay Water Quality Monitoring Program. Additional water quality parameters from the cruises were downloaded from the Chesapeake Bay program website. Additional carbonate system parameters were then computed from DIC and TA