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General information
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Author: Rickard, P.C., Uher, G., Upstill-Goddard, R.C.
Contact: philippa.rickard@ncl.ac.uk
DOI: 10.25405/data.ncl.17006176
License: CC BY 4.0
Last updated: 08-February-2022
Related article: 10.1029/2021GL095469

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Introductory information
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Files included in the data deposit (include a short description of what data are contained): 
1) Surfactant and CDOM photoreactivity, Tyne estuary.xlsx

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Methodological information
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A brief method description – what the data is, how and why it was collected or created, and how it was processed:
Data for total surfactant activity (SA) and chromophoric dissolved organic matter (CDOM) during laboratory controlled 24-hour irradiation experiments of 13 estuarine samples, using natural surface microlayer (SML) and subsurface water (SSW) from the Tyne estuary (UK).
Three sample treatments were used: irradiated samples (IS), dark controls (DC) and temperature controls (TC).
SML samples were collected using a Garrett Screen (mesh: 16, wire diameter: 0.36 um; effective surface area: 2025 cm2).
SSW sampling (~20 cm depth) used a clean 12-L steel bucket (Research Vessel Princess Royal; TE2-4) or 1-L polypropylene sample bottle (TE1).
Surface-active substances (surfactants) are ubiquitous in seawater and freshwater.
They accumulate in the uppermost < 1000 um (SML) where they slow the rate of gas exchange between water and air.
Improved knowledge of surfactant distributions and behaviour will improve global gas flux estimates (e.g. for CO2) used to inform climate models. 

Instruments, hardware and software used: 
Solar simultor light source was 300 W Xenon-arc lamp (LOT Oriel; 300 nm transmission cut off).
SA was measured using phase sensitive alternating-current voltammetry (797VA Computrace, Metrohm, Switzerland) with hanging mercury drop electrode.
CDOM was measured using a UV-Visible double beam spectrophotometer (M550: Spectronic Camspec Ltd., UK; (250-800 nm, 1 nm increments).
Data was processed in Microsoft Excel.
All statistical procedures used SPSS.

Date(s) of data collection: 
27-June-2016, 18-July-2016, 29-August-2016, 14-October-2016, 25-November-2016, 02-December-2016, 30-January-2017.

Geographic coverage of data:
The Tyne estuary (UK); Newburn, Millennium Bridge, Walker and Herd Sands (Tynemouth).

Data validation (how was the data checked, proofed and cleaned):
Data manually checked and proofed.

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Data-specific information
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Definitions of names, labels, acronyms or specialist terminology uses for variables, records and their values: 
Site IDs: TE (Tyne Estuary) 1-4.
SML: Sea-surface microlayer.
SSW: Subsurface water.
Incubation: Hours.
Sample treatments: In situ, Irradiated sample (IS), Dark Control (DC), Temperature Control (TC).
UF: Unfiltered.
F: 0.2 um filtered.
SA: Total surfactant activity; expressed in mg/L equivalents of model surfactant T-X-100.
CDOM: Chromophoric Dissolved Organic Matter.
a300: CDOM absorbance at 300 nm.
S275-295: CDOM spectral slope between 275-295 nm.
S350-400: CDOM spectral slope between 350-400 nm.
SR: Slope ratio = S275-295/S350-400.

Outline any missing data:
CDOM data were not produced for samples collected on 27-June-2016 due to instrument malfunction.
CDOM samples were lost for: 29-August-2016_Newburn_TE1_SSW_6_IS_UF, 14-October-2016_MillenniumBridge_TE2_SML_4_TC_UF, 25-November-2016_Walker_TE3_SML_24_IS_UF, 25-November-2016_Walker_TE3_SML_2_DC_UF, 02-December-2016_HerdSands(Tynemouth)_TE4_SML_2_TC_UF.
SA samples were lost for: 18-July-2016_Newburn_TE1_SSW_4_DC_UF, 29-August-2016_Newburn_TE1_SSW_6_IS_UF, 25-November-2016_Walker_TE3_SML_24_IS_UF.
Temperature data were not produced for samples collected on 27-June-2016 and 29-August-2016 due to intrument malfunction.
Temperature sample was lost for: 25-November-2016_Walker_TE3_SML_24_IS_UF.