An application of fluorescent tracer to groundwater tracking-EXPLAINED

                                                            
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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