Dataset: Atmospheric & gaseous mercury from aerosol samples collected using high volume and low volume sampling systems on Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES PMT cruise (GP15, RR1815) on R/V Roger Revelle from Oct-Nov 2018

This dataset reports atmospheric mercury associated with aerosols collected using a high volume sampling system and from a low volume sampling system (a Tekran speciation unit). The Tekran low volume sampling system was also used to measure total gaseous elemental mercury and gaseous ionic ("reactive") mercury, which are also reported in this dataset.

High Volume Atmospheric Mercury:
Atmospheric mercury associated with aerosols collected using a high volume sampling system. The samplers were deployed and monitored by the GEOTRACES atmospheric group (operated by Bill Landing/Cliff Buck). The sampling duration was based on the volume of air filtered, which was not consistent as the sample system was sectored, based on wind direction and speed, so that air was only sampled under conditions where there was no potential for contamination from the ship's stack and other potential sources. Filter samples were provided post-cruise for analysis. Samples are identified by an event ID and a sample ID. Samples were digested prior to analysis for total Hg using standard techniques as detailed in various publications (Mason et al., 2017; DiMento et al., 2019).

Total atmospheric Hg from the high volume sampler is reported in units of picograms per cubic meter (pg/m³).
Detection limit = 0.02
Spike recovery (%) = 99.6±6.3

Low Volume Atmospheric Mercury:
Atmospheric mercury associated with aerosols collected using a low volume sampling system (using a Tekran speciation unit). The Tekran sampler was deployed continuously but after the cruise data was removed that was compromised due to potential contamination by the ship, based on the high volume collection sampling times, and also when the sampling was compromised while the ship was on station. As the instrument blanks itself after every measurement, this post-cruise analysis was possible. As these samples were collected continuously with 1-hour sampling resolution, there are no identifying GEOTRACES ID's associated with them. The automated instrument collects a sample for a pre-determined period and then the collected particulate material is heated to high temperature to release the Hg as elemental Hg, which is detected and quantified by a Tekran 2537X analyzer. The analyzer is calibrated by an in situ calibration (permeation) system and via external spike injections. Reported concentrations are daily average values and their standard deviation.

Total atmospheric Hg from the low volume Tekran sampler is reported in units of picograms per cubic meter (pg/m³).
Detection limit = <6
Spike recovery (%) = 95-107

Total Gaseous Elemental Mercury:
Total gaseous elemental mercury concentration in the atmosphere, measured using the Tekran speciation with 5-minute resolution. This is an automated sampling system. The Tekran sampler was deployed continuously but after the cruise data was removed that was compromised due to potential contamination by the ship, based on the high volume collection sampling times, and also when the sampling was compromised while the ship was on station. As the instrument blanks itself after every measurement this post-cruise analysis was possible. There are no identifying GEOTRACES IDs' associated with these samples. Reported concentrations are daily average values and their standard deviation. The method of analysis is detailed in Mason et al. (2017) and DiMento et al. (2019). Parameter is named based on the format developed by the GEOTRACES committee as: Hg_G_0_CONC_LOWVOL, with the designation of G for a gaseous sample. In the scientific literature, the measurements are reported with the following acronyms: TGM, TGHg, GEM.

Total gaseous elemental mercury from the Tekran system is reported in units of nanograms per cubic meter (ng/m³)
Detection limit = 0.02
Spike recovery (%) = 95-107

Gaseous Reactive Mercury:
Gaseous ionic (so-called "reactive") mercury concentration in the atmosphere, measured using the Tekran speciation with 1-hour resolution. This is an automated sampling system. The gaseous ionic fraction is removed by the Tekran instrument using a potassium chloride-coated denuder which collects an integrated sample. After heating the denuder, the Hg is released as elemental Hg and quantified using a Tekran 2537X instrument, which is calibrated as detailed above. Analytical details can be found in He and Mason (2021). The Tekran sampler was deployed continuously but after the cruise data was removed that was compromised due to potential contamination by the ship, based on the high volume collection sampling times, and also when the sampling was compromised while the ship was on station. As the instrument blanks itself after every measurement this post-cruise analysis was possible. There are no identifying GEOTRACES ID's associated with these samples. Reported concentrations are daily average values and their standard deviation. Parameter is named based on the format developed by the GEOTRACES committee as: Hg_G_R_CONC_LOWVOL. In the scientific literature, the measurements are reported with the following acronyms: RGM, RGHg, GOM.

Gaseous reactive mercury from the Tekran system is reported in units of picograms per cubic meter (pg/m³).
Detection limit = <6
Spike recovery (%) = 95-107