<div><p><strong>Methodology:</strong> Details of the methods for the cruise are given in DiMento et al. (2019). Details of the overall method and approach for dissolved gaseous mercury and atmospheric mercury methods are given in Andersson et al. (2008), Mason et al. (2017), Soerensen et al. (2014), and Soerensen et al. (2013). Analytical methods are detailed in DiMento et al. (2019) with additional information in the papers listed above and in Munson et al. (2014), Morton et al. (2013), and Gichuki & Mason (2014). See "Related Publications" below for complete citations.</p>
<p><strong>Sampling Procedures:</strong> Surface water samples were obtained using water collected at 5-10 m depth from the ship's underway sampling system. The water is continuously sparged with low elemental Hg (Hg⁰) air in a water-gas separation device (gas equilibrator) with a reverse flow configuration where the water is added to an inner chamber at the top and air at the bottom of the chamber. The water then flows through an outer jacket of the device to maintain the water temperature in the inner chamber at that of the incoming sweater. The device is based on the equilibrator described in detail in Andersson et al. (2008). For the best performance the water flow should be high relative to that of the air, and in this study the air flow was maintained around 1.5 L min⁻¹, somewhat higher than that required by the Tekran 2537B instrument that was used for Hg detection (1 L min⁻¹). The water flow was somewhat variable but typically was 6-10 times that of the air. The incoming air is passed through spargers that create small gas bubbles to enhance equilibration and this is also enhanced by the mixing induced by the incoming water. Based on the relative flow rates, the response time of the instrument to changes in water concentration is <5 min (Andersson et al., 2008) so changes between a set of measurements could reflect changes in the water on the same timescale. Depending on the ship's speed, this represents a spatial sampling resolution of 1-2 km for a 5 minute sample. Based on our experience, measurements while the ship is stationary are often higher and more variable, and so these measurements are not considered reliable and are not included in the database. The air is dried using a Teflon filter and a soda lime trap prior to the passing to the detector – a Tekran 2537B mercury analyzer.</p>
<p>The detection of Hg as elemental Hg in the air after sparging relied on a Tekran 2537B instrument with a sampling resolution of 10 min. As described above, the instrument is calibrated in two ways. Air is sampled continuously as there are two sampling gold traps lines within the instrument and while one sample is being analyzed, the other is being trapped, with the timing controlled by the instrument's software. Air was sampled from the outside at a location sufficiently above the water level to prevent entrainment of water, and in a position to prevent contamination for the ships' exhaust while underway. The air is dried using a Teflon filter and a soda lime trap prior to the detector. The sampled air was passed over trapping devices to remove particulate Hg and gaseous ionic Hg prior to the measurement of elemental Hg. The device was used as prescribed by the Tekran methods and was calibrated as detailed above.</p></div>
The data include measurements of total dissolved gaseous mercury in surface waters
<div><p>The data include measurements of total dissolved gaseous mercury in surface waters during the GEOTRACES Arctic Ocean cruise in 2015 (HLY1502, GN01).</p></div>
GN01 Dissolved Gaseous Mercury Underway
<div><p><strong>QA/QC:</strong> Measurements of elemental mercury in surface seawater and in the atmosphere relied on the use of a Tekran air measurement instrument, which has a built-in calibration unit (Hg⁰ permeation tube) for calibration, which was done daily. External injections of Hg⁰ were also used to check the accuracy of the permeation device. The instruments had a detection limit of <0.2 ng m⁻³ for air sampling and <2 fM for water sampling during the cruise (water concentration calculated from the measured value in the equilibrated air). The detection limit for the equilibrator is evaluated based on the sparging of water without water flow. As the DGHg is removed by sparging and not replenished without flow, long-term sparging results in values that reflect the background blank and the variability in this value is used to estimate the detection limit. For the air sampling, the instrument periodically flushes the system with Hg-free air and makes blank measurements. Again, these values and their variability can be used to determine the detection limit for air sampling. Prior studies have compared concentrations measured using the continuous sampler to those with manual methods and verified consistency over a range of seawater temperatures (Andersson et al., 2008; Soerensen et al., 2014). Our data was also compared with measurements by the Hammerschmidt and Lamborg research group made on board for both underway samples and for samples collected from the Go-Flo bottles. Results were comparable.</p>
<p>Performance of the continuous sampler was also verified in the laboratory prior to the cruise by injection and recovery of external standards. Data presented in the table represent the average hourly value for each set of measurements, which were made at 10 minute resolution, and which are only presented for when the ship was underway, and not for times when the ship was on station. Typical variability was 3% and 10% for 1 hr of observations in air and water, respectively; n = 6 for 10-min samples (per hour).</p>
<p>BCO-DMO Processing:<br />
- modified parameter names to conform with BCO-DMO and GEOTRACES naming conventions;<br />
- formatted dates to yyyy-mm-dd;<br />
- filled blanks with "nd" (no data);<br />
- 2021-01-25: renamed fields with the GEOTRACES DOoR barcodes;<br />
- 2021-02-19: removed columns Hg_0_G_CONC_LOWVOL & Hg_0_Flux. </p></div>
779135
GN01 Dissolved Gaseous Mercury Underway
2019-10-14T15:49:02-04:00
2019-10-14T15:49:02-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:779135
Measurements of total dissolved gaseous mercury in surface waters from the US GEOTRACES Arctic cruise (HLY1502, GN01) from August to October 2015
The data include measurements of total dissolved gaseous mercury in surface waters during the GEOTRACES Arctic Ocean cruise in 2015 (HLY1502, GN01).
false
Mason, R. (2021) Measurements of total dissolved gaseous mercury in surface waters from the US GEOTRACES Arctic cruise (HLY1502, GN01) from August to October 2015. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 2) Version Date 2021-01-25 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.779135.2 [access date]
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10.26008/1912/bco-dmo.779135.2
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2021-01-25
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