Finland comparing different sampling techniques to ensure cost efficiency

iFLUX passive sampler

Highlights

  • Validation of different sampling techniques 
  • Cost efficiency
  • Investigating groundwater contamination

Situation

Chlorinated Hydrocarbons (PCE, TCE)

Source: Metal Industry

Customer: Finnish government

Location: Finland

Finland has over 25,000 registered and potentially contaminated sites. The Finnish government aims to investigate and manage these pollutions. In order to achieve their ambitious goal, they need extra insights and additional information. Approximately 15,000 of these sites still need to be investigated regarding pollution and potential interventions. It is estimated that around 35% of them could present a potential hazard.

Analyzing and managing these sites  by means of traditional methods? The cost of this is estimated at 4 billion euros. A huge cost for the Finnish government.

An alternative solution is therefore needed! That’s why the Finnish Ministry of  Environment started the PASSIIVI project. The aim of the project is to investigate the groundwater contamination. 

Environment:

•    20% of these sites are located on, or near classified groundwater areas

•    12% of them are located on, or near a shoreline area

•    3% are near a protected habitat area


Sampling

To measure chlorinated hydrocarbon fluxes at two different sites in Finland, we installed 12 iFLUX samplers in 6 different monitoring wells at the field sites. The project entailed 3 measuring phases.  Every monitoring well was equipped with 2 iFLUX samplers. Both contaminant flux cartridges and water flux cartridges were used in the samplers. iFLUX samplers assessed the speed and direction of contaminant spreading. By doing this, reliable data was provided and the spreading risk from the soil contamination was determined more accurately.

The insights obtained during the one-year investigation were summarized into one report. This report desribes all possibilities and characteristics of iFLUX compared to the different employed technologies.

finland

"iFLUX provides essential information about the underground dynamics where alternatives rely on assumptions"

iFLUX sampler in Finland

Challenges

How to determine accurate soil contamination data more cost efficiently:

  • Validate passive sampling techniques
  • Risk determination
  • Prioritizing of remediation projects
  • Cost efficiency

Solutions

iFLUX provides more accurate insights in contamination and its underground dynamics:

  • Possibility to compare water fluxes with measured data
  • Determine spreading risk of contaminants in groundwater by measuring their movement
  • Most agile pollution towards risk areas can be prioritized for remediation
  • Impact on cost efficiency through insights in more targeted remediation actions

Results

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The thickness of the polluted groundwater layer was between 15 and 25 m. The plume length was between 50 and 100 m.  During the first phase, measured groundwater fluxes varied between 6 and > 29 cm/day. Mass flux distributions could be nicely measured and were mainly confirmed in all 3 measurement campaigns. The highest mass fluxes were measured in the shallow part of RHP20 and the deep part of RHP11 for tetrachloroethene. During the second phase, the highest mass fluxes were measured in the deep part of RHP16 for tetrachloroethene while the shallow fluxes seem to have increased in all wells, except RHP20. The third phase showed a comparable pattern except a higher flux was also measured in the shallow part of RHP2. Measured trichloroethene fluxes were about 100x lower in the 3 phases suggesting non-optimal biodegradation conditions.


In the comparative study , carried out by the Finnish authorities, the mass fluxes were directly compared with the results of groundwater samples analyses taken just before and after the exposure of the iFLUX samplers. Other passive sampling devices were tested at other locations. It should be emphased that, as shown in the figures extracted from the study, these data are not comparable since the concentrations provide static information at a given moment while the fluxes provide information on the dynamics for a much longer measurement period. Furthermore, concentrations are generally contribution-weighted averages of each horizon intercepted by the well screen, whereas the flux results are higher-resolution measurements of specific horizons at discrete depths in the well.


Figures: tetrachloroethene flux values (mg/m²/d) measured in the deep (pohja) and shallow (pinta) part of each well in the 3 phases compared to the concentration (µg/l) measurements in blue, green and purple. The right part shows the lithology and position of the sampled depths..

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