Table 1 Overview on DOC and LMWOA concentrations, and DOC composition in water samples from different geothermal regions of the world

South African Mines Kieft et al. (2018)

 Beatrix

34–38***

1339

Witwatersrand quartzite

0.2–1.5

0.04–0.44

Aliphatics, carboxyls, aromatics

 Driefonteine

26.8***

1046

Transvaal dolomite

0.3–1.02

0.01–0.55

 Kloof

54.5***

3276

Ventersdorp metavolcanics

4.92

0.68–0.77

 Tau Tona

49–51***

3048

Witwatersrand quartzite

0.22–0.73

0.01–0.19

 Star Diamonds

31***

640

Karoo sandstone

0.25

0.02–0.07

 Joel

39.9***

1300

Witwatersrand quartzite

0.18

0.04–0.07

 Masimong

40.7***

1900

Witwatersrand quartzite

0.54

0.02–0.07

 Koffie-fontein

28.9***

578

Archean gneiss

n.d

\(<0.11\)

 Finsch

28.9***

1056

Transvaal dolomite

n.d

0.3–0.31

Pannonian Basin

 Kovacs et al. (2012)

41–83**

1000–2100

Late Miocene and Pliocene sandstones

8.5–139\(^{\mathrm{a}}\)

Carboxyls, aromatics aliphatics humic content: 2.9–9.5 mg/L

 Varsányi et al. (2002)

38–111*

490–2200

Quarternary–Upper Miocene sediments

2.5–28\(^{\mathrm{a}}\)

n.d–38.5

Humic content: 0.1–15.7 mg/L aromatics: 0.11–24.94 \(\upmu\)g/L phenols

 Varsányi et al. (2002)

17–56*

240–816

Quarternary–Pleistocene sediments

6.8–84\(^{\mathrm{a}}\)

Humic content: 9.71–30.52 mg/L aromatics: n.d–20 \(\upmu\)g/L phenols

 Varsányi et al. (2002)

50–132*

701–2181

Pleistocene–Upper Miocene sediments

4.8–550\(^{\mathrm{a}}\)

n.d–923

Humic content: 1.2–50.1 mg/L aromatics: n.d–17.29 \(\upmu\)g/L

 Kárpáti et al. (1999)

12–99*

30–2500

Quarternary–Upper Miocene sediments

n.d–46

Humic content: n.d–12.5 aromatics, phenols, fatty acids n-alkanes

North German Basin

 NG1 Leins et al. (2022)

34***

850

Upper Keuper sandstone

4.9

n.d

 NG2 Leins et al. (2022)

64***

1620

Lower Dogger sandstone

2.5-7.7

1.8-2

 NG3 Leins et al. (2022)

98**

2450

Upper Keuper sandstone

19.5-25.9

44.8-49.3

 Groß Schönebeck (NG4) Feldbusch (2015)

150*

4400

Permo-Carboniferous sediments and volcanic rocks

25

29.77

Molasse Basin Vetter (2012); Leins et al. (2022)

 M2-M8

65–135\(^{*{/}**}\)

2250–4083

Jurassic carbonate (Malmian)

0.35–30.1

n.d–16.9

Styrian Basin Westphal et al. (2019)

 Bad Blumau (S1), Austria

107**

2800

Palaeozoic carbonate

14.5

Vienna Basin Leins et al. (2022)

 V1

53*

900

Middle Miocene conglomerate

0.22-1.51

n.d

Baltic Sea Basin Brehme et al. (2019)

 Klaipeda (B1), Lithuania

38*

1100

Devonian sandstone

1.6–2.4

Russian geothermal fields

 Mutnovskii Kompanichenko et al. (2016)

175**

1600–1800

Quarternary–Oligocene sediments and volcanic rocks

Aromatics, O-bearing, Cl-bearing, S-bearing hydrocarbons

 Annenskii Poturay (2017)

99**

44–202

Cretacerous volcanic and tuff sedimentary rocks

n-Alkanes, esters, alcohols, carboxylic acids, terpenes, steroids

Los Humeros geothermal field, Mexico

 Sánchez-Avila et al. (2021)

292–348**

1800–2800

Neogene–Quarternary volcanic rocks

n-Alkanes, aromatics, S-bearing, O-bearing hydrocarbons

Upper Rhine Valley Sanjuan et al. (2016)

 RV1-RV5

66–200*

1547–5000

Triassic–Carboniferous sediments and granite

0.7–35.2

Canadian Shield Sherwood Lollar et al. (2021)

 Kidd Creek

23–27***

2400

Precambrian metasedimentary, metavolcanic rocks

29–60

64–94

 Thompson

21.9–22.7***

1200

Precambrian metasedimentary, metavolcanic, ultramafic rocks

0.61–8.7

0.1–8

Lost City Hydrothermal Fields (Mid-Atlantic Ridge)

 Lang et al. (2010)

31–91*

Seafloor

Mantle rocks

0.7–1.2

n.d–6.9

Alkanes, cycloalkanes, aromatics, carboxyls

East African Rift Valley Hot Springs Butturini et al. (2020)

 Ol Njorowa

>50**

–

Pleistocene basalts, trachyites, pyroclastics

1.67

Aromatics, carboxyls aliphatics

 Lake Elementaita

36.6**

–

Pleistocene basalts, trachyites, pyroclastics

0.97

Aromatics, carboxyls aliphatics

Thermal Water Springs

 Ourense, Spain González-Barreiro et al. (2009)

45.6–66.3**

–

Granitic rock

amines/amides, esters, acids, alcohols, aliphatic/alicyclic/aromatics, Phenols

 Calabria, Italy Di Gioia et al. (2006)

-

–

Phenols, fatty acids, long-chain saturated and unsaturated alcohols, long-chain carboxylic acids and alcohols, n-alkanes