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AMT16 major ions and trace metals in aerosol samples

Originator's Protocol for Data Acquisition and Analysis

Atmospheric sampling was conducted on the JCR's monkey island when wind conditions permitted, i.e. apparent wind direction was forward of the monkey island ensuring no contamination from the ship's stacks. Samplers were in general turned off while on station unless the bridge were confident of remaining head to wind throughout all manoeuvring. Sampling throughout passage allowed 16-20 hours sampling per day. Two high volume aerosol samplers (approx. 1 m ³ min ^-1 ) were deployed. One was for major ions and used conventional Whatman 41 filter substrates. One for trace metals and used conventional Whatman 41 filter substrates after rigorous acid pre-cleaning. Filters were changed in a laminar flow cabinet and subsequently frozen.

Analyses were carried out once the samples were returned to the laboratory at the University of East Anglia (UEA) as detailed in Baker et al. (2006) and the main analytical technique for each parameter is listed in the table below.

References Cited

Baker A.R., Jickells T.D., Biswas K.F. and French M., (2006). Nutrients in atmospheric aerosol particles along the Atlantic Meridional Transect. Deep Sea Research: Part II, 53, 1706-1719.

Instrumentation Description

Not relevant to this data set.

BODC Data Processing Procedures

Data were submitted to BODC on three occasions, when the data from each successive file superseded the previous data with additional parameters included in the latest submission. The most recent submission was received on 10/11/2008 and contained the data from AMT cruises 12-17 and was loaded to the archive with BODC accession number UEA060021. Data were submitted in an Excel spreadsheet with the following metadata; Sampling start and end date, latitude and longitude. Sample metadata were checked against information held in the database - there were no metadata in the database, so the data for the sampling events were loaded from the originator's file. Start and end times were taken from the cruise report appendix containing details of the aerosol sampling. The times were confirmed as UT by comparison of the time and position given in the appendix and the time/positon combination in the ship's navigation data. Parameter codes defined in BODC parameter dictionary were assigned to the variables; most of the parameters were provided in nmol m ^-3 and were converted to pmol m ^-3 to be consistent with parameters in the BODC parameter database. Data were loaded into BODC's database using established BODC data banking procedures.

A parameter mapping table is provided below;

Data Quality Report

BODC were not advised of specific quality checks carried out by the data originator. A number of the samples had concentrations lower than the detection limit. This detection limit was calculated assuming a sample volume of 1400m ³ , but since there was variation in the volumes sampled the concentrations quoted in conjunction with the 'below detection limit' flag (<) are reported as 75% of the concentration with a 1400m ³ volume.

Problem Report

Not relevant to this data set.