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| Dataset Title: | Experimental observations of radionuclide uptake by colloidal and particulate humic acids obtained from 14 soils collected worldwide 
|
| Institution: | BCO-DMO (Dataset ID: bcodmo_dataset_738833) |
| Information: | Summary
| License
| ISO 19115
| Metadata
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Attributes {
s {
No {
Byte _FillValue 127;
Byte actual_range 1, 14;
String bcodmo_name "Site_Desig";
String description "site number";
String long_name "No";
String units "unitless";
}
HA_ID {
String bcodmo_name "sample_descrip";
String description "Sample description";
String long_name "HA ID";
String units "unitless";
}
Site {
String bcodmo_name "site";
String description "Name of site.";
String long_name "Site";
String units "unitless";
}
Soil_Order {
String bcodmo_name "sample_descrip";
String description "Soil Order";
String long_name "Soil Order";
String units "unitless";
}
Land_use {
String bcodmo_name "site_descrip";
String description "Land use description";
String long_name "Land Use";
String units "unitless";
}
Sample_ID {
String bcodmo_name "sample";
String description "Identifier for the sample";
String long_name "Sample ID";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/ACYC/";
String units "unitless";
}
part_210Pb {
Byte _FillValue 127;
Byte actual_range 9, 99;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Lead 210";
String long_name "Part 210 Pb";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
part_234Th {
Byte _FillValue 127;
Byte actual_range 0, 92;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Thorium 234";
String long_name "Part 234 Th";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
part_7Be {
Byte _FillValue 127;
Byte actual_range 10, 100;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Beryllium 7";
String long_name "Part 7 Be";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
part_59Fe {
Byte _FillValue 127;
Byte actual_range 12, 99;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Iron 59";
String long_name "Part 59 Fe";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
part_237Np {
Byte _FillValue 127;
Byte actual_range 14, 80;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Neptunium 237";
String long_name "Part 237 Np";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
part_233Pa {
Byte _FillValue 127;
Byte actual_range 12, 94;
String bcodmo_name "radioactive_isotope_conc";
String description "Particulate activity percentage for Protactinium 233";
String long_name "Part 233 Pa";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_210Pb {
Byte _FillValue 127;
Byte actual_range 0, 79;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Lead 210";
String long_name "Col 210 Pb";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_234Th {
Byte _FillValue 127;
Byte actual_range 8, 100;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Thorium 234";
String long_name "Col 234 Th";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_7Be {
Byte _FillValue 127;
Byte actual_range 0, 69;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Beryllium 7";
String long_name "Col 7 Be";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_59Fe {
Byte _FillValue 127;
Byte actual_range 1, 79;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Iron 59";
String long_name "Col 59 Fe";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_237Np {
Byte _FillValue 127;
Byte actual_range 11, 78;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Neptunium 237";
String long_name "Col 237 Np";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
col_233Pa {
Byte _FillValue 127;
Byte actual_range 5, 49;
String bcodmo_name "radioactive_isotope_conc";
String description "Colloidal activity percentage for Protactinium 233";
String long_name "Col 233 Pa";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/WRAD/";
String units "unitless";
}
logKd_210Pb {
Float32 _FillValue NaN;
Float32 actual_range 0.88, 4.99;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Lead 210";
String long_name "Log Kd 210 Pb";
String units "unitless";
}
logKd_234Th {
Float32 _FillValue NaN;
Float32 actual_range 0.5, 3.99;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Thorium 234";
String long_name "Log Kd 234 Th";
String units "unitless";
}
logKd_7Be {
Float32 _FillValue NaN;
Float32 actual_range 0.98, 5.23;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Beryllium 7";
String long_name "Log Kd 7 Be";
String units "unitless";
}
logKd_59Fe {
Float32 _FillValue NaN;
Float32 actual_range 0.8, 5.03;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Iron 59";
String long_name "Log Kd 59 Fe";
String units "unitless";
}
logKd_237Np {
Float32 _FillValue NaN;
Float32 actual_range 0.39, 3.48;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Neptunium 237";
String long_name "Log Kd 237 Np";
String units "unitless";
}
logKd_233Pa {
Float32 _FillValue NaN;
Float32 actual_range 0.31, 4.11;
String bcodmo_name "unknown";
String description "partitioning coefficient (logKd) for Protactinium 233";
String long_name "Log Kd 233 Pa";
String units "unitless";
}
logKdc_210Pb {
Float32 _FillValue NaN;
Float32 actual_range 0.6, 5.81;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Lead 210";
String long_name "Log Kdc 210 Pb";
String units "unitless";
}
logKdc_234Th {
Float32 _FillValue NaN;
Float32 actual_range 0.55, 6.0;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Thorium 234";
String long_name "Log Kdc 234 Th";
String units "unitless";
}
logKdc_7Be {
Float32 _FillValue NaN;
Float32 actual_range 0.36, 5.82;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Beryllium 7";
String long_name "Log Kdc 7 Be";
String units "unitless";
}
logKdc_59Fe {
Float32 _FillValue NaN;
Float32 actual_range 0.65, 5.93;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Iron 59";
String long_name "Log Kdc 59 Fe";
String units "unitless";
}
logKdc_237Np {
Float32 _FillValue NaN;
Float32 actual_range 0.63, 5.5;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Neptunium 237";
String long_name "Log Kdc 237 Np";
String units "unitless";
}
logKdc_233Pa {
Float32 _FillValue NaN;
Float32 actual_range 0.74, 5.69;
String bcodmo_name "unknown";
String description "partitioning coefficient in colloidal fraction (logKdc) for Protactinium 233";
String long_name "Log Kdc 233 Pa";
String units "unitless";
}
POC {
Int16 _FillValue 32767;
Int16 actual_range 163, 743;
String bcodmo_name "POC";
String description "Concentration of Particulate Organic Carbon (POC) after one week HAs-groundwater resuspension";
String long_name "Particulate Organic Carbon";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P01/current/CORGCAP1/";
String units "miligrams per liter (mg/L)";
}
PN {
Byte _FillValue 127;
Byte actual_range 11, 78;
String bcodmo_name "Total Particulate Nitrogen";
String description "Concentration of Particulate Nitrogen (PN) after one week HAs-groundwater resuspension";
String long_name "PN";
String units "miligrams per liter (mg/L)";
}
COC {
Int16 _FillValue 32767;
Int16 actual_range 45, 532;
String bcodmo_name "unknown";
String description "Concentration of Colloidal Organic Carbon (COC) after one week HAs-groundwater resuspension";
String long_name "COC";
String units "miligrams per liter (mg/L)";
}
CON {
Byte _FillValue 127;
Byte actual_range 0, 54;
String bcodmo_name "unknown";
String description "Concentration of Colloidal Organic Nitrogen (CON) after one week HAs-groundwater resuspension";
String long_name "CON";
String units "miligrams per liter (mg/L)";
}
pcnt_POC {
Byte _FillValue 127;
Byte actual_range 23, 94;
String bcodmo_name "POC";
String description "Percentage of Particulate Organic Carbon (POC) after one week HAs-groundwater resuspension";
String long_name "Pcnt POC";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P01/current/CORGCAP1/";
String units "unitless";
}
pcnt_PN {
Byte _FillValue 127;
Byte actual_range 26, 100;
String bcodmo_name "Total Particulate Nitrogen";
String description "Percentage of Particulate Nitrogen (PN) after one week HAs-groundwater resuspension";
String long_name "PCNT PN";
String units "unitless";
}
pcnt_COC {
Byte _FillValue 127;
Byte actual_range 6, 77;
String bcodmo_name "unknown";
String description "Percentage of Colloidal Organic Carbon (COC) after one week HAs-groundwater resuspension";
String long_name "Pcnt COC";
String units "unitless";
}
pcnt_CON {
Byte _FillValue 127;
Byte actual_range 0, 74;
String bcodmo_name "unknown";
String description "Percentage of Colloidal Organic Nitrogen (CON) after one week HAs-groundwater resuspension";
String long_name "Pcnt CON";
String units "unitless";
}
}
NC_GLOBAL {
String access_formats ".htmlTable,.csv,.json,.mat,.nc,.tsv";
String acquisition_description
"Basically, the humic acids (HAs) from different soils were isolated and
further purified according to an alkaline extraction method from the
International Humic Substance Society (IHSS) (Xu et al., 2011). Briefly, the
dried soil was pre-treated with a 1 M HCl solution to separate the supernatant
(i.e., fulvic acid) from the soil, followed by the addition of 0.1 M KOH under
N2 purging and 0.3 M K+, as KCl. Then, the supernatant was acidified to pH of
1.0 using 6 M HCl to precipitate HAs, which were pelleted by centrifugation
and then suspended in a 0.1 M HCl/0.3 M HF solution overnight for five times
to minimize ash content. After HF digestion, Milli-Q water was used to wash HA
with the purpose of minimizing ions. HA characterization data were previously
reported elsewhere (Fujitake et al., 2012) and on IHSS website ([http://humic-
substances.org/13c-nmr-estimates-of-carbon-distribution-in-...](\\\\\"http
://humic-substances.org/13c-nmr-estimates-of-carbon-distribution-in-ihss-
samples/\\\\\")).\\u00a0
The HA-groundwater suspension batch experiments were conducted basically
similar to a previously reported procedure (Xu et al., 2014). In brief, 5-6 mg
of the purified HAs were pre-equilibrated in artificial groundwater in the
centrifuge tubes for 48 h at room temperature (20 \\u00baC) to reach the
dissolution equilibrium, since the HAs were extraceted under pH < 1 but the pH
of artificial groundwater is 5.5. Then, ~50 Bq of each gamma emitting
radionuclide, including 234Th, 237Np-233Pa, 210Pb, 7Be and 59Fe was added to
the HA-groundwater slurry to a final volume of 4 mL. The radiolabeled HA-
groundwater slurry was then mixed continuously for 7 days in the dark with an
end-over-end mixer to ensure that quasi-equilibrium was attained15. After one-
week period, particulate (>0.45 \\u00b5m), colloidal (3 kDa to 0.45 \\u00b5m),
and truly dissolved (<3 kDa) phases were size fractionationated by using 0.45
\\u00b5m centrifugal filter tubes followed by ultrafiltration with 3 kDa
Microsep centrifugal filter tubes (Millipore). Each fraction was collected for
the measurement of radionuclide activity and organic matter concentrations.
All the size fractions, including the particulate, colloidal and truly
dissolved phases were corrected to the same volume and geometry for the
counting of 234Th, 233Pa, 237Np, 210Pb, 7Be and 59Fe activity concentrations
by a Canberra ultrahigh purity germanium well gamma detector.
Concentrations of organic carbon and nitrogen in the colloidal and truly
dissolved fractions were determined using a Shimadzu TOC-L analyzer. The
organic carbon and nitrogen concentrations in the particulate phase of the HA-
groundwater suspension were calculated as the difference between the total
carbon/nitrogen contents of the added HAs and the sum of colloidal and truly
dissolved phases.\\u00a0";
String awards_0_award_nid "735995";
String awards_0_award_number "OCE-1356453";
String awards_0_data_url "http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=1356453";
String awards_0_funder_name "NSF Division of Ocean Sciences";
String awards_0_funding_acronym "NSF OCE";
String awards_0_funding_source_nid "355";
String awards_0_program_manager "Henrietta N Edmonds";
String awards_0_program_manager_nid "51517";
String cdm_data_type "Other";
String comment
"Radionuclide uptake by colloidal and particulate humic acids obtained from 14 soils collected worldwide
PI: Peter H. Santschi
Version: 2018-05-15
Notes: \"-\" denotes data not available due to the undetectable activity in particulate (>0.45 um) or truly dissolved phases (<3 kDa).
\"nd\" indicates AVG and STD were not computed for those observations
\"AVG\" = average
\"STD\" = standard deviation";
String Conventions "COARDS, CF-1.6, ACDD-1.3";
String creator_email "info@bco-dmo.org";
String creator_name "BCO-DMO";
String creator_type "institution";
String creator_url "https://www.bco-dmo.org/";
String data_source "extract_data_as_tsv version 2.3 19 Dec 2019";
String date_created "2018-06-19T14:30:06Z";
String date_modified "2019-04-01T16:23:56Z";
String defaultDataQuery "&time<now";
String doi "10.1575/1912/bco-dmo.738833.1";
String history
"2024-04-26T00:16:15Z (local files)
2024-04-26T00:16:15Z https://erddap.bco-dmo.org/erddap/tabledap/bcodmo_dataset_738833.html";
String infoUrl "https://www.bco-dmo.org/dataset/738833";
String institution "BCO-DMO";
String instruments_0_acronym "Shimadzu TOC-L";
String instruments_0_dataset_instrument_description "Concentrations of organic carbon and nitrogen in the colloidal and truly dissolved fractions were determined using a Shimadzu TOC-L analyzer.";
String instruments_0_dataset_instrument_nid "739032";
String instruments_0_description
"A Shimadzu TOC-L Analyzer measures DOC by high temperature combustion method.
Developed by Shimadzu, the 680 degree C combustion catalytic oxidation method is now used worldwide. One of its most important features is the capacity to efficiently oxidize hard-to-decompose organic compounds, including insoluble and macromolecular organic compounds. The 680 degree C combustion catalytic oxidation method has been adopted for the TOC-L series.
http://www.shimadzu.com/an/toc/lab/toc-l2.html";
String instruments_0_instrument_external_identifier "http://onto.nerc.ac.uk/CAST/124.html";
String instruments_0_instrument_name "Shimadzu TOC-L Analyzer";
String instruments_0_instrument_nid "527277";
String instruments_0_supplied_name "Shimadzu TOC-L analyzer";
String instruments_1_dataset_instrument_description "Beckman Coulter Allegra X-12 centrifuge";
String instruments_1_dataset_instrument_nid "738844";
String instruments_1_description "A machine with a rapidly rotating container that applies centrifugal force to its contents, typically to separate fluids of different densities (e.g., cream from milk) or liquids from solids.";
String instruments_1_instrument_name "Centrifuge";
String instruments_1_instrument_nid "629890";
String instruments_1_supplied_name "Beckman Coulter Allegra X-12 centrifuge";
String instruments_2_dataset_instrument_description "Canberra ultrahigh purity germanium well gamma detector Model GCW3024";
String instruments_2_dataset_instrument_nid "738841";
String instruments_2_description "Instruments measuring the relative levels of electromagnetic radiation of different wavelengths in the gamma-ray waveband.";
String instruments_2_instrument_name "Gamma Ray Spectrometer";
String instruments_2_instrument_nid "670659";
String instruments_2_supplied_name "Canberra ultrahigh purity germanium well gamma detector";
String keywords "bco, bco-dmo, biological, carbon, chemical, coc, col, col_210Pb, col_233Pa, col_234Th, col_237Np, col_59Fe, col_7Be, con, data, dataset, dmo, erddap, HA_ID, kdc, land, Land_use, log, logKd_210Pb, logKd_233Pa, logKd_234Th, logKd_237Np, logKd_59Fe, logKd_7Be, logKdc_210Pb, logKdc_233Pa, logKdc_234Th, logKdc_237Np, logKdc_59Fe, logKdc_7Be, management, oceanography, office, order, organic, part, part_210Pb, part_233Pa, part_234Th, part_237Np, part_59Fe, part_7Be, particulate, pcnt, pcnt_COC, pcnt_CON, pcnt_PN, pcnt_POC, poc, preliminary, sample, Sample_ID, site, soil, Soil_Order, use";
String license "https://www.bco-dmo.org/dataset/738833/license";
String metadata_source "https://www.bco-dmo.org/api/dataset/738833";
String param_mapping "{'738833': {}}";
String parameter_source "https://www.bco-dmo.org/mapserver/dataset/738833/parameters";
String people_0_affiliation "Texas A&M, Galveston";
String people_0_affiliation_acronym "TAMUG";
String people_0_person_name "Peter Santschi";
String people_0_person_nid "735998";
String people_0_role "Principal Investigator";
String people_0_role_type "originator";
String people_1_affiliation "Texas A&M, Galveston";
String people_1_affiliation_acronym "TAMUG";
String people_1_person_name "Antonietta Quigg";
String people_1_person_nid "736000";
String people_1_role "Co-Principal Investigator";
String people_1_role_type "originator";
String people_2_affiliation "Texas A&M, Galveston";
String people_2_affiliation_acronym "TAMUG";
String people_2_person_name "Kathleen Schwehr";
String people_2_person_nid "736002";
String people_2_role "Co-Principal Investigator";
String people_2_role_type "originator";
String people_3_affiliation "Texas A&M, Galveston";
String people_3_affiliation_acronym "TAMUG";
String people_3_person_name "Chen Xu";
String people_3_person_nid "736004";
String people_3_role "Co-Principal Investigator";
String people_3_role_type "originator";
String people_4_affiliation "Woods Hole Oceanographic Institution";
String people_4_affiliation_acronym "WHOI BCO-DMO";
String people_4_person_name "Mathew Biddle";
String people_4_person_nid "708682";
String people_4_role "BCO-DMO Data Manager";
String people_4_role_type "related";
String project "Biopolymers for radionuclides";
String projects_0_acronym "Biopolymers for radionuclides";
String projects_0_description
"NSF Award Abstract:
Particle-associated natural radioisotopes are transported to the ocean floor mostly via silica and carbonate ballasted particles, allowing their use as tracers for particle transport. Th(IV), Pa (IV,V), Po(IV), Pb(II) and Be(II) radionuclides are important proxies in oceanographic investigations, used for tracing particle and colloid cycling, estimating export fluxes of particulate organic carbon, tracing air-sea exchange, paleoproductivity, and/or ocean circulation in paleoceanographic studies. Even though tracer approaches are considered routine, there are cases where data interpretation or validity has become controversial, largely due to uncertainties about inorganic proxies and organic carrier molecules. Recent studies showed that cleaned diatom frustules and pure silica particles, sorb natural radionuclides to a much lower extent (by 1-2 orders of magnitude) than whole diatom cells (with or without shells). Phytoplankton that build siliceous or calcareous shells, such as the diatoms and coccolithophores, are assembled via bio-mineralization processes using biopolymers as nanoscale templates. These templates could serve as possible carriers for radionuclides and stable metals.
In this project, a research team at the Texas A & M University at Galveston hypothesize that radionuclide sorption is controlled by selective biopolymers that are associated with biogenic opal (diatoms), CaCO3 (coccolithophores) and the attached exopolymeric substances (EPS), rather than to pure mineral phase. To pursue this idea, the major objectives of their research will include separation, identification and molecular-level characterization of the individual biopolymers (e.g., polysaccharides, uronic acids, proteins, hydroquinones, hydroxamate siderophores, etc.) that are responsible for binding different radionuclides (Th, Pa, Pb, Po and Be) attached to cells or in the matrix of biogenic opal or CaCO3 as well as attached EPS mixture, in laboratory grown diatom and coccolithophore cultures. Laboratory-scale radiolabeling experiments will be conducted, and different separation techniques and characterization techniques will be applied.
Intellectual Merit : It is expected that this study will help elucidate the molecular basis of the templated growth of diatoms and coccoliths, EPS and their role in scavenging natural radionuclides in the ocean, and help resolve debates on the oceanographic tracer applications of different natural radioisotopes (230,234Th, 231Pa, 210Po, 210Pb and 7,10Be). The proposed interdisciplinary research project will require instrumental approaches for molecular-level characterization of these radionuclides associated carrier molecules.
Broader Impacts: The results of this study will be relevant for understanding biologically mediated ocean scavenging of radionuclides by diatoms and coccoliths which is important for carbon cycling in the ocean, and will contribute to improved interpretation of data obtained by field studies especially through the GEOTRACES program. This new program will enhance training programs at TAMUG for postdocs, graduate and undergraduate students. Lastly, results will be integrated in college courses and out-reach activities at Texas A&M University, including NSF-REU, Sea Camp, Elder Hostel and exhibits at the local science fair and interaction with its after-school program engaging Grade 9-12 students from groups traditionally underrepresented.";
String projects_0_end_date "2018-02";
String projects_0_name "Biopolymers as carrier phases for selected natural radionuclides (of Th, Pa, Pb, Po, Be) in diatoms and coccolithophores";
String projects_0_project_nid "735996";
String projects_0_start_date "2014-03";
String publisher_name "Biological and Chemical Oceanographic Data Management Office (BCO-DMO)";
String publisher_type "institution";
String sourceUrl "(local files)";
String standard_name_vocabulary "CF Standard Name Table v55";
String summary "The uptake and binding of six particle-reactive and/or redox-sensitive radionuclides (210Pb, 234Th, 7Be, 59Fe, 237Np and 233Pa) with different organic functionalities of three size fractions.";
String title "Experimental observations of radionuclide uptake by colloidal and particulate humic acids obtained from 14 soils collected worldwide";
String version "1";
String xml_source "osprey2erddap.update_xml() v1.3";
}
}
Data Access Protocol (DAP) and its
selection constraints.
The URL specifies what you want: the dataset, a description of the graph or the subset of the data, and the file type for the response.
Tabledap request URLs must be in the form
https://coastwatch.pfeg.noaa.gov/erddap/tabledap/datasetID.fileType{?query}
For example,
https://coastwatch.pfeg.noaa.gov/erddap/tabledap/pmelTaoDySst.htmlTable?longitude,latitude,time,station,wmo_platform_code,T_25&time>=2015-05-23T12:00:00Z&time<=2015-05-31T12:00:00Z
Thus, the query is often a comma-separated list of desired variable names,
followed by a collection of
constraints (e.g., variable<value),
each preceded by '&' (which is interpreted as "AND").
For details, see the tabledap Documentation.