A Review of the Hydrochemistry of a Deep Sedimentary Aquifer and Its Consequences for Geothermal Operation: Klaipeda, Lithuania

Table 3

Chemical composition of groundwater from Klaipeda Geothermal Demonstration Plant, showing analysis on a sample collected 5/10/2012 [17], three samples collected and analysed by GFZ-Potsdam in March-July 2016 from well 2P, and a sample collected on 5/4/17, from bulk water storage, and analysed by Glasgow University/SUERC. The final column shows standard sea water as reported by [18, 19]. An analysis of water from 2P in 2010 [9] reported concentrations of 3.2 μg/L As and 0.06 μg/L U. Additional analyses are available in GTN reports [16].

		Gerber et al.	2P wellhead	2P filter	2P	Glasgow 2P stored water	Seawater
Sample date		5/10/12	31/3/16	1/4/16	19/7/2016	5/4/17
Field parameters
pH			6.55	6.39	6.11
EC	μS/cm		125,300	123,300	112,300
Temperature	°C	36.4	36.4	37.2	33.6
ORP	mV	-110	-133	-106	-88
Dissolved O2	mg/L		0.85	0.90	0.45
Laboratory analysis
Total dissolved solids	mg/L	88,523					34,483
Total organic carbon	mg/L	12
Major cations
Na^2+	mg/L	23,400	24,299	24,349	24,700	27,755	10,556
K^+	mg/L	557	616	617	656	820	380
Ca^2+	mg/L	6366	7558	7522	7635	7990	400
Mg^2+	mg/L	2175	2375	2364	2399	2450	1262
NH4^+	mg/L	<10					0.05
Major anions
HCO3^-	mg/L	84	85.4	79.3	97.6	48.8	140
Cl^-	mg/L	53,907	56,498	56,835	65,686	80,915	18,980
NO3^-	mg/L (as NO3^-)	<1.6	<0.6	<0.6
SO4^2-	mg/L	1606	1733	1778	2106	1555	2649
Minor elements
F^-	mg/L		0.38	0.36	0.36		1.4
Br^-	mg/L	346	356	333	452	260	65
Fe^2+	mg/L		17	17	21
Mn^2+	mg/L	0.86	1.0	1.0	1.1
Li^+	mg/L	3.3	3.4	3.2	3.6		0.17
B^3+	mg/L	11.0	9.3	8.7	10		4.6
Si^4+	mg/L	6.6	4.7	4.4	4.9		4
Sr^2+	mg/L	143	165	166	169		13
Ba^2+	mg/L	0.16	0.19	0.18	0.19		0.05
Cl/Br mass ratio		156	159	171	145	311	292
Li/Cl mass ratio		6.14-05	6.02-05	5.63-05	5.48-05		8.96-06
Mg/Sr mass ratio		15	14	14	14		97
B/Cl mass ratio		0.00020	0.00016	0.00015	0.00015		0.00024
δ^18O	‰ SMOW	-4.46				-4.5
δ^2H	‰ SMOW	-34.7				-26
^14C	pmc	<0.5
^39Ar	% modern	<14
δ^34SO4	‰					+18.9

Based on a cited total inorganic carbon (TIC) of 16.6 mg/L [17]. As some of the TIC may be carbonic acid, the figure of 84 mg/L may be somewhat overestimated.