Methane concentrations from Askö shallow inshore areas in the Baltic Sea, June to October 2019

Maysoon Lundevall-Zara, Erik Lundevall-Zara, Volker Brüchert

This dataset provides concentration measurements of dissolved methane (CH₄) from water samples and air samples collected from floating chambers. Samples were collected from shallow inshore areas in different coastal habitats around the island of Askö in the Trosa archipelago in the Baltic Sea.

Water and air samples were collected from June to October 2019 during 3⁠ – ⁠6 days each month from different sampling stations representing different coastal habitats around the island of Askö. Water samples were collected from surface water, while air samples were collected from floating chambers on the water surface using the headspace method. Gas concentrations were measured on a Shimadzu gas chromatograph. Paired measurements of surface water and air temperature, salinity, and wind velocity are also provided.

The data was collected in order to determine methane flux in different habitats using two approaches in calculations, the gas transfer model, and the chamber method. The measurements have been used to assess the contribution of different environmental forcing factors to methane flux in different coastal habitats. That will be the first step in upscaling methane emissions for the whole coastline of the Trosa archipelago.

Citation

Maysoon Lundevall-Zara, Erik Lundevall-Zara, Volker Brüchert (2021) Methane concentrations from Askö shallow inshore areas in the Baltic Sea, June to October 2019. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/lundevall-zara-2021-asko-methane-1

References

Lundevall-Zara M, Lundevall-Zara E, Brüchert V (2021) Sea-air exchange of methane in shallow inshore areas of the Baltic Sea. Frontiers in Marine Science. https://doi.org/10.3389/fmars.2021.657459

Data description

This dataset consists of two comma-separated values (csv) files (UTF-8 encoding, the first line contains headers).

Sample data

File lundevall-zara-2021-asko-methane-1-sample-data.csv consists of 17 columns:

1. Sample name
2. Sampling station name
3. Sample type (air or water sample)
4. latitude for the sampling station location
5. Longitude for the sampling station location
6. Water temperature (°C)
7. Air temperature (°C) - obtained from SMHI
8. Salinity (‰)
9. Wind velocity at 1.5 m height (m/s) - obtained from SMHI
10. Methane concentration (nmol/L)
11. Methane concentration from GC analysis (ppm)
12. Sampling timestamp (date and time)
13. Shimadzu GC analysis date
14. Chamber interval qualifier, for grouping of multiple time series intervals at the same station and sampling month. Only for air samples.
15. Chamber volume (L). Only for air samples
16. Chamber diameter at the water surface (m). Only for air samples
17. Comment field

Reference data

File lundevall-zara-2021-asko-methane-1-reference-data.csv consists of 7 columns:

1. Sample type (always standard)
2. Area value from Shimadzu GC analysis of the standard sample
3. Standard deviation for all area values for the standard samples from the same analysis session (same date)
4. Mean value for all area values for the standard samples from the same analysis session (same date)
5. Coefficient of variation (%) for all area values for the standard samples from the same analysis session (same date)
6. Shimadzu GC analysis date
7. Comment field

The file with reference data refers to the standard methane gas measured during the sample analysis with GC-Shimadzu. This standard data had been used to perform linear regression in order to calculate sample concentrations from GC-area. For each analysis session, we calculated the average of standard areas and used that value to perform the linear regression along with a point in origo. Each analysis session had a different analysis date. The average, standard deviation, and coefficient of variation were calculated for each session and included in this data.

See article by Lundevall-Zara et al. (2021) for a description of the area where the data measurements were obtained from, as well as calculation examples for flux based on this data.

Comments

The principal investigators (Maysoon Lundevall-Zara (see Contact information) and [javascript protected email address]) would welcome to receive a notification when the data are used in any publication or derivative work.