AMT14 atmospheric ammonia sampling
Originator's Protocol for Data Acquisition and Analysis
Atmospheric sampling was conducted on the vessel's monkey island when wind conditions permitted, i.e. apparent wind direction was forward of the monkey island to ensure no contamination from the ship's stacks. A low volume air sampling system (approx. 0.05 m 3 min -1 ) was connected to a filter pack system (Johnson et al. 2008).
Ammonia was collected on pairs of oxalic acid impregnated filters (47 mm diameter, Whatmann 40) and background filter packs were deployed and treated in the same way but subject to zero airflow (Johnson et al. 2008). Filters were changed in a glove box under positive pressure of ammonia-free air and frozen at -20 o C. Ammonia was extracted from sample and blank filters into milli-Q ultrapure water and analysed using the manual OPA method (Holmes et al. 1999).
References Cited
Holmes R.M., Aminot A., Kérouel R., Hooker B.A. and Peterson B.J. 1999. A simple and precise method for measuring ammonium in marine and freshwater ecosystems. Canadian Journal of Fisheries and Aquatic Sciences, 56, 1801-1808.
Johnson M.T., Liss P.S., Bell T.G., Lesworth T.J., Baker A.R., Hind A.J., Jickells T.D., Biswas K.F., Woodward E.M.S. and Gibb S.W., 2008. Field observations of the ocean-atmosphere exchange of ammonia: Fundamental importance of temperature as revealed by a comparison of high and low latitudes. Global Biogeochemical Cycles, 22, GB1019, doi:10.1029/2007GB003039.
Instrumentation Description
Not relevant to this data set.
BODC Data Processing Procedures
Data were submitted via email in an Excel spreadsheet archived under BODC's accession number UEA090198. The file contained the following metadata columns: Start and end Date, time (ship's time), latitude and longitude for each sample.
The aerosol ammonia data were provided in nanomoles m -3 . These units were converted to picomoles m -3 to be consistent with the BODC parameter code units and a x1000 conversions was applied.
The data were reformatted and loaded in BODC's samples database under Oracle Relational Database Management System with the supplied metadata. Times were converted from ship's time to UT and the positional data confirmed against the navigational data from the underway records. Data were marked up with BODC parameter codes and loaded into the database.
A parameter mapping table is provided below;
| Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| NH 3 Conc. | nmol m -3 | Concentration of ammonia {NH3} per unit volume of the atmosphere [gaseous phase] by filtration with acid impregnated filter and nanomolar ammonium system after Holmes et al (1999) | ATNH3C97 | pmol m -3 | Unit conversion factor x1000 applied. |
Data Quality Report
A number of values supplied to BODC have been flagged '<' in the database to indicate the concentrations were lower than the analytical detection limit. In these cases the values provided by the data originator were the detection limit and no standard deviation values were supplied.
The data from samples collected on 14-15/05/2004, 19-20/05/2004, 22-23/05/2004, 23-24/05/2004, 24-25/05/2004 and 26-27/05/2004 were based on only one filter pack as the other filter pack result was suspect.
The error quoted for the data collected during this cruise was 2.59 nmol m -3 .
Problem Report
Not relevant to this data set.
