uid=HFR,o=lter,dc=ecoinformatics,dc=org
all
public
read
doi:10.6073/pasta/8edcfbf4d9ee31d4a9090e82dc2a3c83
EMS - Automated High-Frequency Methane Data
Patrick
Crill
2023
English
Automated high-frequency methane (CH4) in ambient air measurements were made at the Harvard Forest (HF) research site since 1992. The proximity and the relative location of the site to numerous industrial/urban areas presents the opportunity to sample air flows that have been influenced by known CH4 sources on a regular and repeatable basis and to characterize the atmospheric chemical signature of the sampling location and assess its sensitivity to both local and regional sources at different time scales.
gas flux
methane
LTER controlled vocabulary
inorganic nutrients
LTER core area
Harvard Forest
HFR
LTER
USA
HFR default
This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.
Creative Commons Zero v1.0 Universal
https://spdx.org/licenses/CC0-1.0.html
CC0-1.0
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf060
Prospect Hill Tract (Harvard Forest). Coordinates based on WGS84 datum.
-72.17
-72.17
+42.54
+42.54
340
340
meter
1991
1994
complete
Information Manager
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
hf-im@lists.fas.harvard.edu
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
(978) 724-3595
https://harvardforest.fas.harvard.edu
The automated CH4 analysis system was designed and maintained by Patrick M. Crill then at the University of New Hampshire, Durham (now at Dept of Geological Sciences, Stockholm University).
The system is built around a Shimadzu Mini-2 gas chromatograph equipped with a flame ionization detector. Ambien air was continuously drawn through an inlet 20 m above the ground surface (a few meters above the forest canopy) through 1/4" OD plastic-coated aluminum tubing (Dekoron 041943-1 tubing) with an electric diaphragm pump at a rate of 25 L/min. This flow was sampled every 8-11 min by diverting flow with a 1/4” Valco stream select valve and dried across a 1m Perma Pure nation drier to rinse and fill a 1ml sample loop on a second 1/8” Valco 6- port injection valve. After five second pause to allow time for sample loop to relax to atmospheric pressure 1 mL of sample was is injected into the carrier gas stream of the chromatograph. The procedure was repeated with a standard gas after sufficient time (3 min) for the sample to elute through the detector. Every sample was followed by a standard in order to compensate for ambient pressure and temperature changes as well as instrument variation. The sampling procedure yielded an independent measurement of ambient CH4 every 8-11min.
CH4 was separated from ambient air on a 2 m by 3.2 mm OD stainless steel column packed with HayeSepQ at 40o C. Detector temperature was 125o C. Valve timing, analog to digital conversion of the detector output and signal integration were controlled by a Hewlett- Packard HP 3395A series II integrator with an HP19405A event controller. Raw data and integration reports were transferred and logged on a personal computer until the data were transferred to the University of New Hampshire via modem every3 days.
During operation a field calibration sample was analyzed with each ambient air sample. The field standards were cylinders of hospital grade breathing air containing near ambient mixing ratios of CH4. The field standards were calibrated by comparing them to Niwot Ridge air standards prepared by NOAA/CMDL in Boulder, Colorado before and after deployment to Harvard Forest. Over the course of a day, the standard response of the gas chromatograph varied about 1% due to diel heating and cooling. The standards were kept in an unheated pump room next to the instrument room in order to mimic the temperature of the outside air sample. Therefore, to evaluate the precision of the CH4 measurements, the responses of an individual analysis of the standards are compared to the 24-min running average of the standard response. The coefficient of variation (CV) (the standard deviation/mean) expressed as the percent variation from the 24-minute running mean ranged annually from 0.18 to 0.29%. If this CV represents the sum of errors in the system measurement (an assumption not entirely true since the standards do not f low through the sampling pump), then the precision of the analysis is considered to be 3.6 ± 0.4 ppbv CH4 . Additionally, all data points were filtered for instrument response by calculating the difference between each standard response and its average with the two points on either side. This difference was then divided by the sample standard deviation for these same five points. The resulting number was then compared with the mixing ratios obtained by the Grubbs test for outliers at a significance level of 95% [Sokal and Rohlf, 1981] and removed as an outlier if it exceeded that value. No data were removed in 1992 and 1993, 1.4% were removed in 1994, and 1.55% were removed in 1995.
Harvard Forest Long-Term Ecological Research
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
(978) 724-3595
https://harvardforest.fas.harvard.edu
https://ror.org/059cpzx98
pointOfContact
The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts.
National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.
hf060-01-methane-hourly.csv
methane data hourly
hf060-01-methane-hourly.csv
963286
7f12887ea4c8c180db2d3db3107b83c6
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p06/hf060/hf060-01-methane-hourly.csv
datetime
date and time
YYYY-MM-DDThh:mm
year
year
YYYY
doy
Julian day
nominalDay
0.0001
real
methane
hourly averaged methane value (ppmv)
dimensionless
0.0001
real
NA
missing value
26328
hf060-02-methane.csv
methane data
hf060-02-methane.csv
4437597
f9a6370d50cf5b3205cf67b3e29449c5
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p06/hf060/hf060-02-methane.csv
datetime
date and time
YYYY-MM-DDThh:mm
month
month
month
year
year
YYYY
time
time
hh:mm
doy
Julian day
nominalDay
0.0000001
real
ch4
methane value (ppm)
dimensionless
0.001
real
NA
missing value
91088
atmosphere
short-term measurement
1
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf004