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Harvard Forest Data Archive

HF240

Water Chemistry and Well Levels at Upper Bigelow Brook, Harvard Forest 2009-2010

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Data

Overview

  • Lead: Henry Wilson, James Saiers, Peter Raymond, William Sobczak
  • Investigators: Na Xu
  • Contact: Henry Wilson
  • Start date: 2009
  • End date: 2010
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.543
  • Longitude: -72.177
  • Elevation: 355 meter
  • Taxa:
  • Release date: 2015
  • Revisions:
  • EML file: knb-lter-hfr.240.3
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: watershed ecology
  • LTER core area: organic matter, inorganic nutrients
  • Keywords: biogeochemistry, carbon, conductivity, groundwater, hydrology, nitrogen, storms, water temperature
  • Abstract:

    This dataset is the result of a full year of high-resolution monitoring of hydrologic event-driven export of stream dissolved organic matter from the Upper Pipe site on Bigelow Brook at Harvard Forest. In situ measurements of fluorescent dissolved organic matter (FDOM) and conductivity were collected from October of 2009 to December of 2010. Grab samples of water were collected during hydrological events and analyzed using standard methods for dissolved organic matter, nitrate, ammonium, and dissolved organic nitrogen. Water level measurements in wells at this study site were initiated in May of 2010.

  • Methods:

    High resolution measurement of fluorescent dissolved organic matter and conductivity

    FDOM measures were collected every 15 minutes (as a single reading) using a Turner Designs Cyclops-7 colored dissolved organic matter (CDOM) fluorimeter sensor connected to a Campbell CR-1000 data logger. This FDOM system uses an LED light source to excite DOM molecules with the peak intensity at 370nm and measures the intensity off fluorescence emission with peak transmissivity a 470 nm. The position of the FDOM sensor was shifted seasonally to maintain submergence with changing water levels. Conductivity and temperature measured at a 15 minute interval using a CS547A probe.

    Of the 365 days over which the instrument was installed, measurements issues were evident during the following time periods: 1) between December 9th, 2009 and January 22nd, 2010 where ice formation under low flow conditions impacted measurement, 2) 5 days between November 5th and 10th, 2009 when leaves became lodged over the probe face, 3) 7 days between May 11th and 18th, 2010 where a data logger programming error resulted in data loss, and 4) On July 10th, 2010 where a small event was sampled utilizing an autosampler and the rinsing routine of the autosampler prior to sample collection disturbed debris within the small pool where the FDOM probe was installed, causing attenuation of the FDOM signal. Beyond these 56 days the only other gaps in data collection occurred where no flow was present and water levels dropped below the probe level. The position of the FDOM probe was shifted slightly (less than 30cm) in January to reduce the potential impact of reduced mixing at the sensor location with dropping water level, but was moved 40m upstream in April as velocity patterns continued to change, and then slightly (less than 30cm) in late July to remain submerged after flow temporarily ceased.

    Water sample collection and chemical analysis

    Samples were collected into acid washed 1 Litre polyethylete or polycarbonate bottles either by ahdn or using an automated sampler (ISCO 3700). Samples were kept on ice and filtered within 36 hours of collection through pre-rinsed 0.22 µm pore size Millipore polycarbonate filters. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations were quantified by the combustion method using a Shimadzu TOC-VCSH analyzer. In each sample run, internal check standards were included at concentrations between 1 and 20 mg L-1 C as potassium hydrogen phthalate and between 0.1 and 1 mg L-1 N as NO3-. Maximum deviations from expected values were 0.1 mg L-1 for C and 0.06 mg L-1 for N. NH4+ and nitrate NO3- were determined by colormetric analysis on filtered samples run through a flow analyzer (Astoria-Pacific). The standard deviation of 50 ug L-1 check standards run ten times during a sample run was 5 ug L-1 for NO3- and 4 ug L-1 for NH4+. Considering two standard curves run at the start and end of each run (0, 5, 10, 50, 100, 300 ug L-1), the maximum deviation of any individual value at the end of run from the expected value was 2 ug L-1 for NO3- and 8 ug L-1 for NH4+. DON was calculated as the difference between TDN and NO3- plus NH4+. For each sample, FDOM measures were also made on a bench top fluorometer (Varian Cary Eclipse) as the intensity for the single wavelength combination of excitation 370nm, emission 470nm . This wavelength combination corresponds most closely with those used by the Turner Designs probe. Bench top fluorometer readings were converted to R.U. prior to analysis using the area under a Milli-Q blank scatter peak at excitation 350nm. A Beckman DU 520 spectrophotometer was used to measure absorbance spectra and these spectra were utilized to correct benchtop FDOM for minor inner filter effects (Walker and others 2009).

    Groundwater Wells

    Wells were constructed of 5cm (inner diameter) PVC pipe and installed within the watershed to measure water table elevation. One well is positioned at the toe slope approximately 13m from the stream and the other well in the upland approximately 26m from the stream. The toe slope well was installed to a depth of 3m and bottomed within the soil profile, while the upslope well was installed to a depth of 5.4m and penetrated roughly 3m into bedrock. Water levels were measured using Campbell Scientific pressure transducers connected to the CR1000 datalogger.

  • Use:

    This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.

  • Citation:

    Wilson H, Saiers J, Raymond P, Sobczak W. 2015. Water Chemistry and Well Levels at Upper Bigelow Brook, Harvard Forest 2009-2010. Harvard Forest Data Archive: HF240.

Detailed Metadata

hf240-01: water chemistry and well levels

  1. datetime: date and time of collection
  2. conductivity: conductivity (unit: millisiemensPerCentimeter / missing value: NA)
  3. water.temp: water temperature (unit: celsius / missing value: NA)
  4. cdom.se.volt: fluorescence of colored dissolved organic matter measured by Turner Cyclops probe. Fluorescence is measured in the range of 0-5000mV and calibrated against grab samples. (unit: millivolt / missing value: NA)
  5. spec.conductivity: conductivity normalized for 25 deg C (unit: microSiemen / missing value: NA)
  6. toe.water.depth: water level in toe slope well (unit: foot / missing value: NA)
  7. hill.water.depth: water level in hill slope well (unit: foot / missing value: NA)
  8. hill.water.temp: water temperature in the well (unit: celsius / missing value: NA)
  9. doc: dissolved organic matter measured using Shimadzu TOC analyzer. All samples were filtered at 0.22um. (unit: milligramsPerLiter / missing value: NA)
  10. tdn: total dissolved nitrogen measured using Shimadzu TOC analyzer. All samples were filtered at 0.22 um. (unit: milligramsPerLiter / missing value: NA)
  11. no3: nitrate (unit: microgramsPerLiter / missing value: NA)
  12. nh4: ammonium (unit: microgramsPerLiter / missing value: NA)
  13. fdom: fluorescence of dissolved organic matter measured by Cary Varian Eclipse. Samples were excited at 470 nm and their emissions at 370 nm recorded and converted to Raman units. (unit: waveNumber / missing value: NA)