Methane Background Levels in Groundwaters of Lower Saxony

Country / Region: Germany / Lower Saxony

Begin of project: July 1, 2014

End of project: June 30, 2018

Status of project: June 20, 2016

Spatial distribution of methane concentrations compiled from the first sampling campaign in 2014. Concentrations’ distribution varies according to local geological conditions and covers a broad span (nano- to milliliter gas per liter groundwater) Source: Schloemer et al., 2016

Many concerns arose within the general public and government/political institutions over potential groundwater contamination with hydrocarbon gases from hydrocarbon exploration, potential carbon capture and storage projects as well as wells drilled for geothermal energy exploitation. The project “Methane Background Levels in Groundwaters of Lower Saxony” is a joint research project of BGR’s Sub-Department “Resource Geochemistry” department with the Lower Saxony State Authority for Mining, Energy and Geology (LBEG) in close collaboration with the Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN). The scientific aim is the assessment of background levels for hydrocarbon concentrations (methane, ethane and propane) dissolved in Lower Saxony’s groundwater.

Possible environmental and health impacts are more and more in the focus of the public. Essential parts of the preventive environmental and groundwater protection are therefore regional baseline values for soils, rocks and groundwater.
In Lower Saxony the responsibility of controlling the groundwater quality rests with LBEG and NLWKN. Within their regular examinations concentrations of dissolved organic and inorganic substances are determined, but dissolved hydrocarbon gases, like methane, ethane or propane, have not been monitored in Lower Saxony, yet. In comparison to Great Britain, to some federal states in the US, or Canadian provinces only small scaled studies of spatially very limited areas have been conducted in Germany so far.
Sampling for this project is realised by NLWKN and LBEG within their annual regular sampling programs. This enables BGR to determine the concentrations of dissolved methane, ethane and propane of up to ~1300 wells per sampling campaign. Additionally the stable carbon and hydrogen isotopic compositions of methane are analyzed.

Based on the resulting datasets natural background levels will be determined, further the spatial distribution and the provenance of the dissolved gases should be elucidated. Through repeated sampling of identical wells temporal variations of naturally occurring concentrations will be estimated.

Results of this research project will be made accessible to the public through peer-reviewed papers in scientific journals (see below), the BGR report and in the near future through the NIBIS map server by LBEG. First results demonstrate strong regional differences of dissolved methane concentrations in Lower Saxony, covering seven orders of magnitude. Methane levels in coastal and polder areas were observed to be significantly enhanced. Initial stable carbon isotope analytic for these samples point towards microbial sources causing the elevated abundances.

Outlook:

• Repeated sampling leads towards a better understanding of temporal variations, especially for methane concentrations
• Measuring the stable hydrogen isotopic concentrations should improve the understanding of the gases provenances
• Preparation of a standardized protocol for sampling and analyzing of hydrocarbon gases dissolved in groundwater shall be achieved

• To improve the understanding and significance of regional variations small scale sampling campaigns including soil gas monitoring for selected locations are planned

  
  
  

Literature:

Schloemer S, Elbracht J, Blumenberg M and Illing CJ (2016) Distribution and origin of dissolved methane, ethane and propane in shallow groundwater of Lower Saxony, Germany. Applied Geochemistry 67, 118-132.

Partner:

Lower Saxony State Authority for Mining, Energy and Geology (LBEG)
Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN)