<div><p><strong>Sample Collection</strong><br />
Aerosol samples were collected on acid-washed Whatman 41 (W41) cellulose ester filter papers deployed in one of two high-volume aerosol samplers (model 5170-VBL, Tisch Environmental) deployed simultaneously operating at approximately 1.2 cubic meters air per minute. The aerosol samplers were deployed on the ship’s flying bridge (14 m above sea level) as high off the water as possible. Contamination from the ship’s stack exhaust was avoided by controlling aerosol sampling with respect to wind sector and wind speed using an anemometer interfaced with a Campbell Scientific CR800 datalogger and PC. The samplers were allowed to run when the wind was +/- 60 degrees from the bow and > 0.5 m/s. When the wind failed to meet these two criteria, the motors were shut off automatically and not allowed to restart until the wind met both the speed and direction criteria for 5 continuous minutes. The anemometer was deployed nearby on a separate pole in 'free air' where turbulence from the wind crossing the bow did not cause the wind vane to wobble excessively.</p>
<p><strong>Trace Metal Determination</strong><br />
For determinations of total aerosol trace metal composition, the W41 filter discs were digested in tightly capped Teflon vials using sequential additions of concentrated acid solutions [nitric acid (Optima) and hydrofluoric acid (Optima)] at 150 degrees C (Morton et al., 2013, accepted). Any solution remaining after each digestion step was heated to dryness. After the final digestion and dry down, the samples were re-dissolved with 0.32 M nitric acid for analysis using inductively-coupled plasma mass spectrometry (ICP-MS; Agilent 7500CS and Thermo Element 2). All filter digestions were performed under a Class 100 laminar flow hood at the National High Magnetic Field Laboratory at Florida State University (FSU).</p>
<p>Filters for both the total and soluble aerosol concentration measurements were stored frozen prior to processing.</p>
<p>Blank solutions for the acid digestions were prepared by digesting W41 discs that had been deployed in the aerosol samplers for 1 h while not in operation. For example, blanks accounted for 65.6 ± 0.52 ng m-3 air Fe (representing an average of 0.09 ± 0.001% of the Fe sample concentrations). Trace metal concentrations in the blanks were subtracted from all acid-digested filter samples. Leachate blanks were prepared by passing 100 mL of deionized water through W41 filters that had also been deployed in the same way as the acid digestion blanks. Blank leachates averaged 0.004 ± 0.001 ng m-3 air dissolved Fe (representing an average of 1.6 ± 0.38% of the Fe sample concentrations) and were subsequently subtracted from all leachate sample concentrations. Relative standard deviations of replicate analyses averaged 7% for total Fe concentrations. Replicate analyses of soluble Fe produced relative standard deviations of 10%.</p>
<p><strong>References:</strong><br /><strong>Buck</strong>, C.S., et al. 2010. The solubility and deposition of aerosol Fe and other trace elements in the North Atlantic Ocean: observations from the A16N CLIVAR/CO2 repeat hydrography section. Marine Chemistry 120, 57-70. doi: <a href="https://dx.doi.org/10.1016/j.marchem.2008.08.003" target="_blank">10.1016/j.marchem.2008.08.003</a>.<br /><strong>Buck</strong>, C. S., Landing, W.M., Resing, J. A., Lebon, G. T. 2006. Aerosol iron and aluminum solubility in the northwest Pacific Ocean: Results from the 2002 IOC cruise. Geochemistry, Geophysics, Geosystems. 7. doi: <a href="http://dx.doi.org/10.1029/2005GC000977" target="_blank">10.1029/2005GC000977</a>.<br /><strong>Morton</strong>, P.L. et al. 2013. Methods for the sampling and analysis of marine aerosols: results from the 2008 GEOTRACES aerosol intercalibration experiment. Limnology and Oceanography Methods 11:62-78. doi: <a href="https://dx.doi.org/10.4319/lom.2013.11.62" target="_blank">10.4319/lom.2013.11.62</a>.</p></div>
North African mineral dust composition from the 2010 and 2011 U.S. GEOTRACES cruises.
<div><p>Mineral dust composition (aerosol trace metals) (Li, Na, Mg, Al, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Cd, Sn, Sb, Cs, Ba, La, Ce, Nd, Pb, Th, U) from the Northern Africa region. Collected on the 2010 and 2011 U.S. GEOTRACES North Atlantic Transect cruises.</p>
<p>Related Dataset: <a href="http://osprey.bco-dmo.org/dataset.cfm?id=14263&flag=view" target="_blank">GT10-11 - Trace Metals Aerosol</a></p>
<p>Please note that some US GEOTRACES data may not be final, pending intercalibration results and further analysis. If you are interested in following changes to US GEOTRACES NAT data, there is an RSS feed available via the BCO-DMO <a href="http://www.bco-dmo.org/project/2066">US GEOTRACES project page</a> (scroll down and expand the "Datasets" section).</p>
<p># Current version: 17 Sept 2014 Removed Ga69 columns from display<br />
# 6 May 2014: Un-restricted the dataset<br />
# Original version: 23 Oct 2013</p></div>
GT10-11 - N African Mineral Dust Composition
<div><p>Concentrations below the detection limit are flagged as "below_DL" (originally " <_DL") in the data columns. Representative detection limits were calculated using an air volume of 1200 cubic meters. See <a href="/objectserver/48097f7b98e25288f9b9d42ff3b82a43/Aerosol_Detection_Limits.PDF?url=http%3A%2F%2Fbcodata.whoi.edu%2FUS_GEOTRACES%2FAtlanticSection%2FLanding%2FAerosol_Detection_Limits.PDF&f=6636666634393030373561303736346233343264643537646336333864626565687474703a2f2f62636f646174612e77686f692e6564752f55535f47454f5452414345532f41746c616e74696353656374696f6e2f4c616e64696e672f4165726f736f6c5f446574656374696f6e5f4c696d6974732e504446" target="_blank">PDF of detection limits for this dataset</a>.</p>
<p><strong>Data quality flag definitions:</strong><br />
BDL = below detection limit.<br />
0 = No QC performed.<br />
1 = Good data.<br />
2 = Probably good data.<br />
3 = Probably bad data that is potentially correctable.<br />
4 = Bad data.<br />
5 = Value changed.<br />
6 = Sample < blank.<br />
8 = Interpolated value.<br />
9 = Missing value.</p>
<p>BCO-DMO made the following modifications:<br />
- Changed PI-supplied cruise IDs of KN204-5 to KN204-01B. Added 'cruise_part' column to distingush between parts A and B of cruise KN204-01.<br />
- Modified parameter names to conform with BCO-DMO naming conventions.</p>
<p><strong>Additional GEOTRACES Processing:</strong> After the data were submitted to the International Data Management Office, BODC, the office noticed that important identifying information was missing in many datasets. With the agreement of BODC and the US GEOTRACES lead PIs, BCO-DMO added standard US GEOTRACES information, such as the US GEOTRACES event number, to each submitted dataset lacking this information. To accomplish this, BCO-DMO compiled a 'master' dataset composed of the following parameters: station_GEOTRC, cast_GEOTRC (bottle and pump data only), event_GEOTRC, sample_GEOTRC, sample_bottle_GEOTRC (bottle data only), bottle_GEOTRC (bottle data only), depth_GEOTRC_CTD (bottle data only), depth_GEOTRC_CTD_rounded (bottle data only), BTL_ISO_DateTime_UTC (bottle data only), and GeoFish_id (GeoFish data only). This added information will facilitate subsequent analysis and inter comparison of the datasets.</p>
<p>Bottle parameters in the master file were taken from the GT-C_Bottle_GT10, GT-C_Bottle_GT11, ODF_Bottle_GT10, and ODF_Bottle_GT11 datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the Event_Log_GT10 and Event_Log_GT11 datasets. McLane pump cast numbers missing in event logs were taken from the Particulate Th-234 dataset submitted by Ken Buesseler.</p>
<p>A standardized BCO-DMO method (called “join”) was then used to merge the missing parameters to each US GEOTRACES dataset, most often by matching on sample_GEOTRC or on some unique combination of other parameters.</p>
<p>If the master parameters were included in the original data file and the values did not differ from the master file, the original data columns were retained and the name of the parameters were changed from the PI-submitted names to the standardized master names. If there were differences between the PI-supplied parameter values and those in the master file, both columns were retained. If the original data submission included all of the master parameters, no additional columns were added, but parameter names were modified to match the naming conventions of the master file.</p>
<p>See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.</p></div>
4063
GT10-11 - N African Mineral Dust Composition
2013-10-23T16:27:11-04:00
2013-10-23T16:27:11-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:4063
North African mineral dust composition from R/V Knorr cruises KN199-04, KN204-01 in the Subtropical northern Atlantic Ocean from 2010-2011 (U.S. GEOTRACES NAT project)
false
Landing, W. M. (2014) North African mineral dust composition from R/V Knorr cruises KN199-04, KN204-01 in the Subtropical northern Atlantic Ocean from 2010-2011 (U.S. GEOTRACES NAT project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 2014-09-17) Version Date 2014-09-17 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/4063 [access date]
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