An application of fluorescent tracer to groundwater tracking-EXPLAINED

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V. Cidzinkiene, V. Maseliene, R. Girgzdiene, R. Goranina  (2014)

(Open Chemistry)

 

About the study

Location of the study:  Lithuania

Problem statement:      To track the groundwater using Sodium Fluorescein.

Procedure adopted:      Sodium fluorescein is used as a tracer for 2 systems to determine                                                   the groundwater flow direction.  

Methodology

 Sodium fluorescein (C20H10Na2O5) is used.

•      The monitoring well network consists of two subsystems.

•      System I in the north-western part of the site consists of 8 wells: 7 observation (S1-1, S1-2, S1-3, S1-4, S1-5, S1-6, S1-7), and one injection.

•      This well set examines the semi-confined aquifer 10 to 19 m deep.

•      Sandy clay occurs at 4.7–6.7 m.

•     The aquifer of medium-grained sand is below. Borehole S1-7 is installed 4 m deep in an aquifer of technogenic soil (sandy clay dust, sand, traces of organic, etc.).

•      The top layer consists of technogenic soil from 2.3 to 2.7 m, then peat (4.2–4.3 m).

•      A sandy layer pad was detected at 8.7 min wells S2-5 and S2-10. The pad was not reached by the other wells.

•    System II ( S2-1, S2-2, S2-3, S2-4, S2-5, S2-6, S2-7, S2-8, S2-9, and S2-10) is placed in the unconfined aquifer at4.5–9 m.

•      The tracer mass required (M) was estimated:

M=10.CB.VW

•      Where Vw is the water volume and CB is the apparent background fluorescein concentration

CB=0.01.a

•     Sodium fluorescein (500 mg) was dissolved in pure water and injected in the injection well.

 

Results

System 1:

•     Appearance was expected 8 hours after injection but no fluorescence was then detected.

•     However, the maximum intensity occurred after 10 hours, the groundwater velocity is higher than expected.

•      The highest intensity was in well S1-1 showing flow is towards the northwest.

System 2:

•      The highest fluorescence was detected in S2-1 and S2-3, suggesting water flow is toward the northwest.

•      The same direction was found in the first system confirming the main flow across the site.

•      The maximum fluorescence was observed after 350 hours in all wells, the highest in S2-6.

•      Which confirmed the direction of water flow in the NW direction towards Lake Druksiai.

Conclusions

•     The results indicate a great hydraulic connection between injection and observation wells.

•      Higher fluorescence intensity was detected in the wells that sampled closest to the surface.

•      The average groundwater migration velocity in the deep aquifers is 10 m per day and 6 m per day in the shallow one.

Reference                                                 

•      Cidzikienė, V., Jakimavičiūtė-Maselienė, V., Girgždienė, R., & Ivanec-Goranina, R. (2014). An application of fluorescent tracer to groundwater tracking. Open Chemistry, 13(1), 497-501.

 


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