Geochemical features of hydrocarbons and fatty acids in sediments of the inland hydrothermal environments of Japan

Org. Geochem.Vol. 15, No. 2, pp. 199-208, 1990 Printed in Great Britain

0146-6380/90 $3.00 + 0.00 Pergamon Press plc

Geochemical features of hydrocarbons and fatty acids in sediments of the inland hydrothermal environments of Japan GENKI I. MATSUMOTOand KUNIHIKOWATANUKI The University of Tokyo, College of Arts and Sciences, Department of Chemistry, Komaba, Meguro-ku, Tokyo 153, Japan (Received 28 December 1988; accepted 6 October 1989)

Abstract--Hydrocarbons, n-alkanes, acyclic isoprenoid alkanes, steranes and triterpanes and fatty acids were studied for 6 sediment samples from inland acid hydrothermal environments (Mounts Yakeyama and Tateyama areas and Lake Katanuma) in Japan to clarify their features and to elucidate their source organisms. Normal alkanes carbon chain length ranging from n C~3 to n C35 and acyclic isoprenoid alkanes iCi6, iCIs, pristane, phytane and/or squalane were found, together with steranes and triterpanes. The major hydrocarbons were mainly odd-carbon numbered long-chain n-alkanes (> C20), such as nC29 and n C31. Normal alkanoic acids (n C~0~C34) were detected with the predominance of even-carbon numbers maximizing at nCi6 and nC24 , •C26 or r/C28, along with iso- and anteiso-branched (i, aC~2-i, aCi7 ) and n-alkenoic acids nCi6:l (carbon chain length:number of double bonds), nCls:,, nC20:, and nC22:,. These compounds can be attributed to various source organisms bacteria, cyanobacteria, microalgae and vascular plants in and around the hydrothermal environments. Low concentrations of hydrocarbons and fatty acids may reflect the low primary productivity of their harsh environments, but the abundances of n-alkenoic acids reflect that fresh organic matter is continuously supplied by microbial activity and vascular plants. The (22S/22R)- 17~t,2lfl (H)-30,3 l-bishomohopane ratios (0.85-1.5) and (20S/20R)-24ethyl-5ct(H),14ct(H),17ct(H)-cholestane ratios (0.254).80) revealed that the thermal alteration of biologically synthesized configuration has taken place to a large extent in the hydrothermal environments. Key words--hydrocarbons, n-alkanes, pristane, phytane, squalane, triterpanes, steranes, fatty acids, inland hydrothermal sediments, Japan

INTRODUCTION Hydrocarbons, including n-alkanes, acyclic isoprenoids, triterpanes, steranes and fatty acids are ubiquitous organic groups in various natural environments of the world. The features of these organic groups are widely used to determine sources of organic matter, to assess the sedimentary environments and/or thermal maturation studies (e.g. Matsuda and Koyama, 1977; Didyk et al., 1978; Matsumoto et al., 1979, 1987; Seifert and Moldowan, 1979; Mackenzie et al., 1982). The features of organic components in the hydrothermal environments can be expected to be much different from those in common inland aquatic and marine environments. Although hydrocarbons and fatty acids in marine hydrothermal vent samples at the East Pacific Rise, 13°N are studied by Brault et al. (1984, 1988), no one has reported hydrocarbons and fatty acids in inland hydrothermal environments. The large abundances of iso- and anteiso-alkanoic acids as well as n-alkenoic acids in the marine hydrothermal sediment indicate a high activity of microorganisms (Brault et al., 1984). The biomarker compounds from hot water near the hydrothermal vents are characteristic of thermally mature organic matter as indicated by

the 17~t(H)> 17fl(H)-hopane series, and the dominance of 5~t(H),14fl(H),17fl(H)-steranes over the 5ct(H),14~t(H),17a(H)-steranes (Brault et al., 1988). Here we first report hydrocarbons and fatty acids in sediment samples from inland acid hydrothermal environments of Japan to elucidate their features in relation to source materials. Also thermal alteration of organic matter will be discussed based on sterane and triterpane epimerization. MATERIALS AND METHODS

Sampling sites and samples

The geochemical characteristics of Hatimantai hydrothermal environments, involving Tamagawa Hot Spring, Mount Yakeyama and Gosyogake Hot Spring in Akita-ken, Japan have been extensively studied by Minami and his co-workers (e.g. Minami et al., 1958; Watanuki, 1961; Fig. 1). Many acid hot springs and active fumaroles are distributed in and around a volcano, Mount Yakeyama. Noguchi and Nishiido (1969) studied the chemical natures of Jigokudani hydrothermal areas at Mount Tateyama, Toyama-ken. There are a number of active fumaroles and acid hot springs in this area. Lake Katanuma (area, 0.14 km2; max depth, 20 m; pH c. 2) is strongly 199

200

GENKI I. MATSUMOTOand KUNIHIKOWATANUKI I

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138 °

.40°N : M/O-yunuma P,

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L. Katanuma

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Fig. 1. Map of northern part of Honshu Island showing sample locations. acid crater lake, has active fumaroles in the shore, located at Miyagi-ken. Limnological studies of the lake are undertaken by several researchers (e.g. Satake and Saijo, 1974, 1978). During 1986 and 1987, sediment samples were collected from boiling mud pools at Mount Yakeyama (Yakeyama) and at Tamagawa Hot Spring (Tamagawa), and O-yunuma Pond at Gosyogake Hot Spring, Lake Katanuma and hot water pools at Jigokudani of Mount Tateyama (Tateyamal and -2; Fig. l). The general features of sampling sites and sediment samples are given in Table 1. These samples were kept frozen at - 2 0 ° C until analyzed in December 1987.

Analyses The analytical methods of hydrocarbons and fatty acids were reported elsewhere (Matsumoto et al., 1979, 1987). Briefly, wet sediment samples (c. 50g)

were refluxed with 0.5N potassium hydroxide methanol (80°C, 2 h) and centrifuged. The supernatants and residues were acidified with concentrated hydrochloric acid and extracted with ethyl acetate. The ethyl acetate extracts were treated with active copper powder to remove elemental sulfur (Blumer, 1957) and chromatographed on a silica gel column. Hydrocarbons and fatty acids were eluted with hexane and benzene/ethyl acetate (95/5), respectively. Hydrocarbons and methyl esters of fatty acids were analyzed using a Shimadzu GCMS-QP1000 gas chromatograph-mass spectrometer equipped with a fused silica capillary column (DB-5, 30 m x 0.32 mm i.d., film thickness of 0.25 #m). Cooled on-column injector was used. Temperatures of injection block, molecular separator and ion source were maintained at 335, 320 and 250°C, respectively. The column oven temperatures were programmed from 70 to 120°C at 25°C/min, 120 to 310°C at 6°C/min and then maintained 310°C for 20 min except for triterpanes and steranes. Mass spectra (m/z 50-600) were taken at 70eV continuously with 1.3 s interval. For the mass fragmentography of triterpanes (m/z 191 and molecular ions) and steranes (m/z 217, 151,259 and molecular ions), the column oven temperatures were programmed from 70 to 230°C at 15°C/min and then from 230 to 310°C at 2°C/min. Identification of hydrocarbons and fatty acids was performed by the comparison of retention times and mass spectra with those of authentic compounds and/or published literature (e.g. Wardroper et al., 1977; Matsumoto et al., 1979, 1987; Seifert and Moldowan, 1979; Philp, 1986). Quantitation of each compound was made by the comparison of peak height with that of authentic compounds (tetracosane for n-alkanes, pristane and squalane for acyclic isoprenoids and hexadecanoic acid for fatty acids).

RESULTS

Normal alkanes and acyclic isoprenoid alkanes A suite of n-alkanes ranging in carbon chain length from nCi3 to nC35 were found with the predominance of long-chain components (>C20) in the mass chromatogram (m/z 71) of the hydrocarbon fraction

Table I, General features of sampling sites and sediment samples for inland hydrothermalenvironments Sampling site Boiling mud pool, Tamagawa Hot Spring (Tamagawa) Boiling mud pool, Mount Yakeyama (Yakeyama) (3-yunuma Pond, Gosyogake Hot Spring Hot water pool-l, Jigokudani~ Mount Tateyama (Tateyama-1) Hot water [0ool-2, Jigokudani, Mount Tateyama (Tateyama-2) Lake Katanuma

Etevation (above sea level, m)

Sampling date

Water temp. (*C)

pH

770

11 June ~87

96.0

1.9

1280

12 June t87

83.0

1,6

1010

12 June ~87

93.5

3.9

2310

13 Oct. '86

59.8

2.2

2310

13 Oct, '86

76.5

2.8

310

13 June '86

23.3

2.2

Nature of sample Silt, Greenish gray Silt, Greenish gray Clay, Bluish gray Silt~ Olive gray Fine sand, Light gray Silt, Greenish gray

Hydrocarbons and fatty acids in inland hydrothermal environments

201

29 28

13 14 15 .... i,,, ,l,, ,,i,,,,i,,,,i,,,,i,,

200

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1000

1200

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1400

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1600

Data number

Fig. 2. Mass chromatogram of the hydrocarbon fraction (m/z 71) from the sediment sample of O-yunuma Pond at Gosyogake Hot Spring, Akita-ken. Arabic figures on the peaks denote carbon chain length of n-alkanes. Pr = Pristane. Ph = Phytane. from the sediment sample of O-yunuma Pond at Gosyogake Hot Spring, together with acyclic isoprenoid alkanes iC16, r/C18, F/CI9 (pristane) and iC20 (phytane, Fig. 2). The analytical results of hydrocarbons in the acid hydrothermal sediment samples are summarized in Table 2. The major hydrocarbons were mainly long-chain odd-carbon numbered nalkanes nC29, nC31 and nC27, but nCl7 alkane was abundant in the Tateyama-1 and -2, and Lake Katanuma sediments. Acyclic isoprenoid alkanes iCj6 , iC18, pristane, phytane and/or squalane were found in the sediment samples. Unresolved complex mixture (UCM) hydrocarbons (hump) were found in all the sediment samples, but they were not quantified. The total concentrations of hydrocarbons (n-alkanes and acyclic isoprenoids) ranged from 0.0021 to 2.3#g/g of dry sample (Table 3).

Triterpanes and steranes Pentacyclic triterpanes and triterpenes having between C27 and C35 carbon numbers were detected in

the mass fragrnentogram (m/z 191) of the hydrocarbon fraction from the sediment sample of O-yunuma Pond (Fig. 3). Triterpanes, triterpenes and moretanes found in the hydrothermal sediment samples are given in Table 4. Their concentrations were much lower than those of n-alkanes. The major triterpanes (>= 10%) were 17ct(H),21fl(H)-30-norhopane, hop° 17(21)-ene, 17ct(H),21fl(H)-hopane, 17fl(H),21fl(H)30-norhopane, (22S)- 17~t(H),21 fl (H)-30-homohopane and/or C30:l hopene (unidentified), differing considerably among the samples. Mass fragmentogram of the steranes (m/z 217) from the sediment sample of O-yunama Pond is shown in Fig. 4. The major peaks were only C29 sterane epimers with the most prominent component of (20R)-24-ethyl-5~t (H), 14ct(H), 17~ (H)-cholestane. Steranes and diasteranes found in the sediment samples are shown in Table 5. Steranes between C27 and C29 carbon numbers were found in the sediment samples. The major steranes were (20R)5~t(H),14~(H),17~t(H)-cholestane, (20R)-24-ethyl5~t(H), 14fl(H), 17fl(H)-cholestane/(20R)-24-ethyl-

Table 2. Normal and acyclic isoprenoid alkanes found in sediment samples from inland hydrothermal environments

Composition (%) n-Alkane 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Isoprenoid 16 18 Pristane Phytane Squalane Long/Short* CPIH$

Tamagawa

Yakeyama

O-yunuma Pond

Tateyama-1

Tateyarna-2

1.1 1.1 1.1 1,3 0,9 1,3 1.0 0.7 0.7 0,8 1.5 0.7 6,5 1.1 23,7 1.8 35,2 1.4 11.4 0.6 1.2

1,8 1,7 1,5 1,7 1,3 1,1 1.0 0.8 1.0 1o0 1.2 1o4 6,5 3,1 17o3 3.1 39,5 1,3 7.6 0,7 0.7

O.1 0,2 0,3 0.2 0,2 0.3 0.7 0.7 1.2 1°4 3,3 4,4 11,8 16,2 22,6 15,7 14,9 2,8 2.2 0,3 0.2

1.4 2,1 2.6 1,4 1.5 1o2 1.7 1.6 3.4 2°6 4,2 2.6 10,2 3,8 17,9 3,7 22,4 3,0 7.1 1,0 1,7

3,6 3,2 8.2 4,2 4,1 3,5 4,6 3.5 5,2 4.0 6,0 3.7 8,2 3,0 11,6 1.5 7,3 0,9 1,9

7.0 5,5 9,4 5.7 6,3 4,5 5,8 4°4 5,7 3,2 6.0 2,4 8,2 1,8 6,2 0,8 2,5

0.7 1.5 0.9 1,8 16 8.2

0.8 2.2 1.1 0,6 11 5.2

0.6 0,9 2.8 1,8 5.7 2,8 2,2

2,8 1,8 4,4 3.7 0,7 1,6 2,0

0,2 0.1 76 1.4

*nC2o-nC35/nCis-nCi9 n-alkane ratio. SCarbon preference index for n-alkanes (nC~7-nC3~).

0.4 0,1 0,8 1.6 9,8 3.3

Lake Katanuma

1,2

202

GENKI I. MATSUMOTOand KUNIHIKO WATANUKI

Table 3. Hydrocarbon (n-alkanes and acyclic isoprenoids) and fatty acid concentrations for sediment samples from inland hydrothermal environments Concentration (ug/g of dry sample) Hydrocarbons (A) Fatty acids (B)

Sampling site Tamagawa Yakeyama ()-yunuma Pond Tateyama-1 Tateyama-2 Lake Katanuma

0.0021 0.020 0.34 0.0066 0.57 2.3

0.062 0.13 0.56 2.2 7.6 32

i, aCl7 (Fig. 4, Table 6). The major fatty acids were chiefly short-chain ( < C20) n-alkanoic acids n C l6 and nCts, and n-alkenoic acids nCt6:t and nCls:,, although long-chain n-alkanoic acids ( > nC20) were abundant in the O-yunuma Pond and Lake Katanuma samples. Carbon preference indices for short-chain (CPIFs, 3.5-28) and long-chain (CPIFL, 3.5--8.7) n-alkanoic acids revealed the great predominance of even-carbon numbers in all the samples (Table 6). The total concentrations of fatty acids ranged from 0.13 to 32 #g/g of dry sample (Table 3).

B/A 30 6.5 1.6 330 13 14

5fl(H),14~(H),17ct(H)-cholestane and/or (20R)-24ethyl-5~t (H), 14~ (H), 17~ (H)-cholestane.

DISCUSSION

Fatty acids

Concentration

Normal alkanoic acids ranging in carbon chain length from n C8 to n f3a were found, along with n-alkenoic acids n C i 6 : l , /'/CI8:n , and/or nC22:,, and iso- and anteiso-branched acids raning from i, aC~2 to

The concentrations of hydrocarbons and fatty acids in the sediment samples from the acid hydrothermal environments are quite low, as compared with those of common inland aquatic environments

10

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251 . . . .

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35f . . . .

26 27

401 . . . . . 4~. . .

5~)

Time/min.

Fig. 3. Mass fragmentogram of triterpanes (m/z 191) from the sediment sample of O-yunuma Pond at Gosyogake Hot Spring. Peak identifications are listed in Table 4. Table 4. Triterpanes, triterpenes and moretanes found in sediment samples from inland hydrothermal environments

Composition (%) 1 183(H)-22,29,30-Trisnorhopane (Ts) 2 C27,1 Hopene 3 17~(H)-22,29,30-Trisnorhopane (Tin) 4 1713(H)-22929t30-Trisnor hopane 5 Epimers 17~(Hl,2113(H)- and/or 171~(H),2113(H)-28,30-bisnorhopane 6 17~(H),2 I~(H )-30-Nor hopane 7 Hop-17(21)°erie 8 17!5(H),21~(H)-30-Nor mor etane 9 18~(H)-Oleanane 10 17~(H),2 ll3(H)-Hopane 11 1713(H),2 ll3(H)-30-Nor hopane 12 17B(Hl,21¢(H)-Moretane 13 (22S)- 17ct(H),21B(H)-30-Homohopane 14 (22R)-l?~(H),21B(H)-30-Homohopane 15 17B(H),2113(H)-Hopane 16 17i3(H),2l~(H)-30-Homomoretane

17 Ho~22(29~eoe 18 (22S)-17~(H),2113(H)-30,31-Bishomohopane 19 (22R)- 17¢(H),2113(H)-30,31-Bishomohopane 20 17B(H)121(~(H)-30,31-Bishomomoretane 21 17B(H)12l~(H)-30-Homohopane 22 (20S)- 17~(H),21B(H)-30,31.32-Tr ishomohopane 23 (2OR)-17ct(H),2I~(H )-30t31.32-Tr ishomohopane 24 (20S)°C34;=u~Homohopane 25 (20R)-C34=0 Homohopane 26 (20S)-C35=o Homohopane 27 (20R)-C35t0 Homohopane 17~(H)~21B(H)/17B(H),21B(H)-Hopane (22S/22R)- 17(z(H),2tB( H)-30,31 -Bishomohopane

Tamagawa

Yakeyama

1.7 6.0 2.7

0.8 3.9 * 3.9

7.0 4.9 2.6 0.7 10.4 6.7 + 5.4 4.0 5.0

6.5 6.7 2.9 1.9 9.8 13.6 + 4.4 4.4 8.8

O-yunuma Pond 0.2 2.6 1.4 1.5 10.0 1.3 5.5 8.8 14.6 + 6.0 8.0 7.7 3.3

17.2 3.5 3.9 0.7 3.5 3.0 3.0 2.2 1.9 2.1 1.9 2.1 0.90

Tateyama-1 3.1 * 3.0 2.6

2.8 0.8 2.9 4.2

2.0 3.3 2.9 4.4

13.9 11.8 1.9 0.3 13.4 3.6 + 10.5 6.1 1.8 1.8

14.1 11.7 2.7 0.7 13.4 3.2 2.3 8.8 5.7 2.6

0.3 10.1 14.0 2.1 5.3 12.4 10.7 + 5.8 5.0 3.4

~2

2.6

3.8

3.3 3.5

8.1 9.5 2.5 0.1 1.8 1.9 0.8 0.7 0.5 0.6 Large 0.85

4.3 3.1 0.6 0.9 3.5 2.3 2.4 1.3 2.3 1.7 7.4 1.4

3.8 2.5 2.4 2.0 1.6 1.9 2.2 1.1 0.94

Lake Tateyama-2 Katanuma

0.+8 5.0 3.3 0.6 1.8 3.1 2.4 2.0 1.4 2.1 1.6 5.2 1.5

3.'6

3.4 2.4 0.3 1.1 1.9 1.4 1.1 0.9 1.3 0.9 3.6 1.4

Hydrocarbons and fatty acids in inland hydrothermal environments

203

24

21+22 13

20~

I

~1o~ 1~17,o ~ II / 7.8/~12II I~ ~ '," 1111 / 115

. . . .

I

20

. . . .

i

25

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~

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I

30

. . . .

I

35

. . . .

I

40

Time/min.

Fig. 4. Mass fragmentogram of steranes (rn/z 217) from the sediment sample of t)-yunuma Pond at Gosyogake Hot Spring. Peak identifications are listed in Table 5.

(Cranwell, 1974; Wakeham and Carpenter, 1976; Matsumoto, 1980, 1983; Kawamura et al., 1987). These results may reflect the low primary productivity of these extremely harsh environments. The ratios of fatty acids/hydrocarbon concentrations varied largely from 1.6 to 330, suggesting the difference of source materials and/or different degree of degradation. For instance, the extremely low ratio for the O-yunuma Pond sample suggests that the major source of organic matter is the waxes of vascular plants, whereas the high ratio for the Tateyama-1 sample may be caused by the contribution of cyanobacteria and/or microalgae, as discussed below. Sources

Only long-chain n-alkanes maximizing at nC29 or nC3] were abundant in the Tamagawa, Yakeyama and O-yunuma Pond samples, whereas n-alkanes

showed a bimodal distribution maximizing at nCl7, and nC27, nC29 or nC31 in the Tateyama-1 and -2, and Lake Katanuma samples (Table 2). The long (nC2o-nC3~)/short (nCls-nC19) chain n-alkan¢ ratios for the sediment samples were all much higher than unity (1.6-76), although it is likely that volatile short-chain n-alkanes decreased if they were exposed to evaporation losses in the high temperature hydrothermal environments during a long period of time. The carbon preference indices (CPIH) for nalkanes are considerably higher than unity (1.4-8.2), suggesting that our n-alkanes are mainly come from recent biological sources. Long-chain n-alkanes with marked predominance of odd-carbon numbers are the major hydrocarbons in the waxes of vascular plants (Kolattukudy, 1970; Tulloch, 1976). Thus, the waxes of vascular plants in the surrounding of the sampling sites can be the major hydrocarbon sources of the acid hydrothermal sediment samples. Algal

Table 5. Steranes and diasteranes found in sediment samples from inland hydrothermal environments

Composition (%) 1 (20S)- 1313(H).17a(H )-D iacholestane 2 (20R)-138(H),lT~(H)-Diacholestane 3 (20S)- 13i3(H), 171~(H)-D iacholestane 4 (20R)- 13a(H ),17B(H)-D iacholestane 5 (20S)-24-Methyt-13B(H),l 7~(H)-diacholestane 6 (20R)-24-Methyl- 1313(H). 17~(H)-diacholestane 7 (20R)-513(H), 14a(H ), 17~(H)-Coprostane 8 (20S)-5~(H), 14~(H), 17~(H)-Cholestane 9 (20S)-24-Ethyl- 13B(H),17~(H)-diacholestane] 10 (20R)-5~(H), 14B(H). 17B(H)-Cholestane 11 (20S)-5¢(H), 1413(H),17B(H)-Cholestane 12 (20R)-5~(H), 14a(H), 17~(H )-Cholestane 13 (20R)-24-Ethyl- 1313(H), 17~(H )-diacholestane 14 (20S)-24-Ethyl- 13e(H),lT~(H}-diacholestane 15 (20S)-24-Methyl-5a(H), 14~(H),17~(H)-cholestane 16 (20R)-24-Met hyl-5B(H ), 14a(H ), 17~(H }-cholestane~ 17 (20R)-24-Methyl-5~(H), 14~}(H),17~(H)-cholestane j 18 (20S)-24- Methyl-5e(H), 1413(H),17B(H)-cholestane 19 (20R)-24-Methyl-5c~(H), 14c¢(H), 17c¢(H)-cholestane 20 (208)-24-Ethyl-5a(H), 14c{(H), 17(~(H)-cholestane 21 (20R)-24-Ethy 1-513(H), 14~.(H), 17~(H)-cholestane] 22 (20R)-24-Ethyl-5~(H), 14B(H), 17B(H)-cholestane 23 (20S)-24-Ethyl-5a(H), 14B(H), 17B(H)-cholestane 24 (20R)-24-Et hyl-5Q(H ),14e(H), 17~(H )-cholestane Relative abundances of (20R)-5c¢(H)04e(H),17a(H)sterane (%) C 27 C2S C 29 (20S/20R)-24-Et hyl-5a( H ), 14~(H), 17e(H)-cholestane

OG 15'2--F

Tateyama-1

Tateyama-2

Lake Katanuma

4.4 2.0 1.7 2.7 1.2 6.1 5.8

3.7 2.5 1.0 1.3 2.5 1.4 + 7.7

4.5 2.7 1.7 2.0 3.1 3.0 , 6.8

5.6 1.8 11.1 1.6 1.3 3.7

7.1 4.4 16.3 2.9 0.9 2.2

9.0 7.0 6.5 4.6 1.4 4.7

3.6 3.2 4.8 7.6

4.0 3.7 4.2 6.1

6.5 6.7 4.6 5.2

39.4

10.4 7.8 13.9

9.0 6.7 12.4

7.4 6.1 6.5

2.7 9.6 87.7 0.26

37.2 16.1 46.7 0.55

49.5 12.8 37.7 0.49

36.9 26.1 37.0 0.80

Tamagawa

Yakeyama

O-yunuma Pond

4.9 2.6 1.2 2.7 3.1 + 5.3

3.8 1.8 1.2 1.4 2.3 2.7 + 5.3

0.7 0.5 0.3 + 1.7 1.8 + 1.5

7.9 4.4 6.7 5.0 2.5 5.5

7.7 3.8 5.1 4.6 1.0 4.2

6.4

7.0 5.6 4.1 6.8

5.2 4.7 5.6 7.1

7.0 4.7 13.0

8.4 5.1 19.0

28.2 17.2 54.6 0.52

17.2 18.9 63.9 0.37

1.2 8.5 4.3 6.4 4.3 9.8 13.2

204

GENKI I. MATSUMOTOand KUNIHIKO WATANUKI Table 6, Fatty acids found in sediment samples from inland hydrothermal environments Tamagawa Composition (%) n-Alkanoic 8 0.38 9 1.10 10 0.76 11 0.26 12 4.00 13 0.57 14 6.72 15 3.81 16 24.51 17 3.76 18 11.82 19 0.52 20 1.52 21 0.31 22 2.00 23 0.67 24 3.57 25 0.71 26 2.34 27 0.39 28 2.10 29 0.24 30 0.70 31 0.08 32 0.28 33 34 n-Alkenoic 16:1 2.62 18:n 17.54 20:n 3.19 22:n Branched I s o 12 0.08 /'so 13 0.04 Anr e i s o 13 0.10 I s o 14 0.80 I s o 15 0.25 A n t e i s o 15 0.71 I s o 16 0.66 I s o 17 0.09 An~eiso 17 0.31 15" 0.21 17" 0.28 LongS/Short ¥ 0.27 CPIFs# 5.3 CPIFI-@ 4.8 16:1/16 0.11 18:n/18 1.5 Short, long and branched acids (%) Short ¥ 75.6 Long S 20.2 Branched 4.2

Yakeyama

(~-yunuma Pond

Tateyama-1

Tateyarna-2

Lake Katanuma

0.72 1.65 1.08 0.29 6.10 0.50 9.33 3.37 30.12 2.73 12.92 0.30 1.08 0.22 1.44 0.50 1.67 0.37 2.66 0.27 1.00 0.15 0.43 Trace O.14

0.05 0.08 0.20 0.04 1.22 0.08 1.60 0.95 13.59 0.56 4.65 0.09 0.67 0.10 1.96 1.11 9.18 2.87 10.15 3.94 11.71 3.43 8.19 1.18 2.19 0.24 0.44

0.07 0.06 1.66 0.12 5.87 0.11 8.14 1.41 18.56 0.92 6.86 0.09 1.47 0.08 0.97 0.14 1.17 O.17 0.50 0.08 0.39 0.03 0.13 Trace 0.05

0.09 0.02 0.36 0.03 1.62 0.07 3.24 0.77 19.15 0.43 13.50 0.06 1.12 0.05 0.77 0.12 1.06 0.23 0.72 0.09 0.52 0.05 O.14 Trace 0.03

0.21 0.08 0.19 0.11 2.17 0.49 9.62 7.01 15.61 1.02 3.73 0.10 1.69 0.25 6.37 1.34 11.98 0.83 2.55 0.99 0.48 O.11 0.49 0.03 0.50

0.70 10.84 3.52

1.88 14.33 2.35

15.35 17.85 10.99 1.42

5.12 43.94 4.15 0.57

12.33 14.96 0.67

0.09 0.09 Trace 0.92 1.16 1.21 1.06 0.14 0.88 0.t7 0.18 0.15 8.1 5.1 0.023 0.84

Trace

-0.03 0,03 0.14 0.46 0.34 0.54 0.20 0.24

Trace

0.09 0.34 0.12 0.21 0.14 0.07

Trace 0,04 0.12 1.16 0.47 0.52 0.45 0.50

2.5 13 3.5 0.14 3.1

0.08 0.12 11 8.7 0.83 2.0

0.13 28 7.7 0.27 3.3

80.8 12.3 6.9

28.0 70.8 1.2

83.9 9.9 6.2

85.0 10.7 4.3

0.04 0.13 1.34 0.45 0.51 0.21 1.34 0.09 0.09 0.69 3.5 6.6 0.79 4.0 55.8 38.6 5.6

*Unidentified. SLong-chain n-alkanoic acids (nC20-nC34). Short-chain n-alkanoic acids (nCu-nCt9). ¢'Carbon preference index for short-chain n-alkanoic acids (nCi4-nCis). ~°Carbon preference index for long-chain n-alkanoic acids (nC20-nCn).

and/or cyanobacterial n-alkanes should, however, contribute to the Tateyama-1 and -2, and Lake Katanuma samples, because short-chain n-alkanes, such as nCl7 are often predominant in certain microalgae and cyanobacteria (Gelpi et al., 1970; Weete, 1976). A diatom Pinnularia braunii var. amphicephala, a green alga Chlamydomonas acidophila and a red alga Cyanidium caldarium are primary producers in Lake Katanuma (Satake and Saijo, 1974, 1978), may be main sources of these short-chain n-alkanes. Also, relatively high concentration of n- and acyclic isoprenoid alkanes associated with the abundances of UCM hydrocarbon in the Lake Katanuma sample suggest the contamination by runoff from asphalted road and car parks in the shore of the lake. Although no visible microbial growth was observed at the

sampling sites of the Tateyama-I and -2 samples, certain thermoacidophilic algae, such as Cyanidium caldariurn which contains nCl7 as the prominent hydrocarbons (Nagashima et al., 1986) and cyanobacteria in and around the sampling sites may contribute to our n-alkane distribution. Acyclic isoprenoid alkanes, such as pristane and phytane are commonly found in lacustrine and marine environments, mainly come from phytyl side chain of chlorophylls. The accompanying iC15, iC~6 and iC18 isoprenoid alkanes are postulated to be derived from the phytyl side chain of chlorophylls by a complex sequence of reactions involving oxidation, decarboxylation, reduction and cracking (Didyk et al., 1978; Hahn and Haug, 1985; Volkman and Maxwell, 1986). Alternative possible sources of

205

Hydrocarbons and fatty acids in inland hydrothermal environments acyclic isoprenoid alkanes are thermoacidophilic bacteria, such as Sulfolobus sp. (Langworthy, 1985). Of special interest is the occurrence of squalane in our sediment samples (Table 2). Squalane is found in a Nigerian petroleum (Gardner and Whitehead, 1972), and some marine sediments (Brassell et al., 1980). Also, squalane is a major hydrocarbon in polluted urban aquatic environments of Tokyo, and is believed to be derived from artificial sources, except for fossil fuel products, rather than natural sources (Matsumoto and Hanya, 1980a, 1981). In this case, however, it is unlikely that squalane come from artificial sources, because of neither industry nor active human activity in the sampling sites. It is known that Sulfolobus sp. is widely distributed in the acid hydrothermal environments of Japan (Takayanagi and Sugimori, personal communcation), produces squalane and other acyclic isoprenoids. Thus, in our case, squalane may be derived from Sulfolobus sp. (Brassell et al., 1980; Langworthy, 1985). Hopane-type triterpanes are ubiquitous biological markers in fossil fuels, and their precursors are commonly distributed in bacteria and cyanobacteria. Also, they occur in certain lichens, mosses and vascular plants (Ourisson et al., 1979; Philp, 1985; Matsumoto and Kanda, 1985). 18~t(H)-Oleanane is believed to be a marker of vascular plants (Philp, 1985), and is detected in all the sediment samples. Hence, triterpanes found in our samples may be derived from various organisms in the sedimentary environments. Especially, the occurrence of C3~235 hopanes suggests that polyhydroxybacteriohopanes or other hopanoid compounds of biological origin are important sources of our triterpanes (Ourisson et aL, 1979). Steranes can be derived from sterols, reflecting the sterol composition of organic matter in the sedi-

mentary environments (Seifert and Moldowan, 1981; Mackenzie et al., 1982). C27 sterols, such as cholest-5en-3fl-ol are predominant in certain microalgae and cyanobacteria and C2s sterols (i.e. 24-methylcholest5-en-3fl-ol) are often abundant in some diatoms, dinoflagellates and Prymnesiophycean algae (Volkman, 1986). Although vascular plants are generally accepted as a major source of C29 sterols (i.e. 24-ethylcholest-5-en-3fl-ol) in lacustrine and coastal marine environments in the mid and lower latitudes (e.g. Huang and Meinschein, 1979), most of Antarctic lake sediments contain 24-ethylcholest-5-en-3fl-ol as the prominent sterol, which is derived from certain cyanobacteria and microalgae (Matsumoto et al., 1982, 1983; Volkman, 1986). Figure 6 shows the relative abundances of (20R)-5ct(H), 14ct(H), 17~(H)-sterane (C27 sterane), (20R)-24-methyl-5~t (H),14~(H)I 7~(H)-sterane (C28 sterane) and (20R)-24-ethyl-5~t(H),14ct(H),17~(H)sterane (C29 sterane) for the hydrothermal sediment samples. C29 sterane was abundant in the O-yunuma Pond and Yakeyama samples suggest the higher contribution of vascular plants, whereas C27 sterane was relatively high in the Tateyama-1 and -2 samples implying that the contribution of vascular plants are small. These results are generally consistent with those of the long/short n-alkane ratios (Table 2) and the relative abundances of longchain n-alkanoic acids (Table 6, discussed below). Hence, C:9 sterane in our samples appears to have originated primarily from vascular plants, rather than from microalgae and cyanobacteria. C28 sterane was abundant in the Lake Katanuma sample, reflecting probably the occurrence of dark brown diatom laminae composed of Pinnularia braunii var. amphicephala in the lake sediment (Satake and Saijo, 1978).

16

28 18:1

26 24

I 30

27

29

25 20:1 12

....

I I1¢ ']'"'1'"

'1'"'1''

200

i14

15 ii515\

'lr'''l''''l'''

'["

400

32

22

1

al"

''1' ''rl ''''1

''''

600

I''''l''''lr'''l

''''

800

[''''l'"'l''''l'

N'••'••1'••••••'••'••'•••`•i'r••r•r•••'•••••••'•''•''L••'•rt'''•p''•••''••••'i•'•••

1000

1200

1400

1600

1800

Data number

Fig. 5. Capillary gas chromatogram (TIC) of the fatty acid fraction from the sediment sample of

O-yunuma Pond at Gosyogake Hot Spring. Arabic figures on the peaks denote carbon chain length of n-alkanoic acids, i, a and b = iso-, anteiso- and branched (unidentified)-alkanoic acids, respectively. m :n = Carbon chain length:number of double bonds.

206

GENK!I. MATSUMOTOand KUNIHIKOWATANUKI

025

plants around the sedimentary environments. Thermal effects

Biologically synthesized hopane-type triterpanes generally have the 17#(H),21#(H) configuration which is thermodynamically less stable than the 17~(H),21#(H) configuration (Seifert and Moldowan, 1980). Also, formed are the moretanes having 50 50 a 17#(H),21~(H) configuration (Philp, 1986). The naturally occurring precursor compounds of pentacyclic triterpanes have only the 22R configuration, but with increasing maturation the 22R configuration epimerizes to 22S until an equilibrium ratio (22S/22R) of about 1.5 is attained (e.g. Mackenzie et al., 1982). This ratio has widely been used as an C27 C29 indicator of thermal maturation studies (thermal Fig. 6. Triangular diagram showing the relative abundances stress) of sedimentary organic molecules. of short-chain (nCi2-nCt9) and long-chain (nC20-nCs4) The naturally occurring precursor sterols generally n-alkanoic acids, and branched (iso and anteiso) acids (bCi2-bCD) for sediment samples from the hydrothermal possess the (20R)-5~t(H),14ct(H),I7~(H) configurenvironments, Japan. 1 = Tamagawa; 2 = Yakeyama; ation, but with increasing maturation the 20R 3 = t3-yunuma Pond; 4 = Tateyama-l; 5 = Tateyama-2; configuration epimerizes into 20S until an equi6 = Lake Katanuma. librium ratio (20S/20R) of approximately 1.2 is attained. Also, the 14~t(H), 17~t(H) configuration conLong-chain n-alkanoic acids having the predomi- verts to the more stable 14fl(H) 17# (H) configuration. nance of even-carbon numbers occur abundantly in Thus, the (20S/20R)-24-ethyl-5~(H),14~t(H),17ct(H)the waxes of vascular plants, whereas short-chain cholestane ((20S/20R)-C29 sterane) ratios are n-alkanoic acids present in all living organisms, lso- commonly used as thermal maturation studies and anteiso-alkanoic acids are abundant in certain (Mackenzie et al., 1982; Seifert and Moldowan, 1981; bacteria. Thus, their ratios can reflect the relative Philp, 1985). influences of vascular plants, microalgae and Triterpanes having 17ct(H),21#(H) configuration cyanobacteria, and bacteria (Matsuda and Koyama, were major components in all the sediment 1977; Matsumoto and Hanya, 1980b). samples, for example, as evidenced by the high Long-chain n-alkanoic acids were abundant in the 17ct(H),21 #(H)/17#(H),21# (H)-hopane ratios rang()-yunuma Pond and Lake Katanuma samples, but ing from 1.1 to 7.4 or more large (Table 4). Also, not abundant in the Tateyama-I and -2 samples steranes possesses 5~(H),14#(H),17#(H) configur(Table 6)---consistent other sterane results except ation were found in these samples except for the for the Lake Katanuma sample (Fig. 6). Branched O-yunuma Pond sample (Table 5). These results alkanoic acids were abundant in the Yakeyama indicate that the thermal alteration of biological and Tateyama-I samples, suggesting the higher configuration taken place largely, and similar to those contribution of bacterial lipids, while those of of the water column of the marine hydrothermal ()-yunuma Pond sample were extremely low (1.2%) vents at the East Pacific Rise, 13°N (Brault et al., reflecting small contribution of bacterial lipids. The 1988). contribution of vascular plants for the hydrothermal A suite of (22R)- and (22S)-C3:C35-hopanes were environments can be summarised as follows: found in all the sediment samples. Their (22S/22R)()-yunuma Pond > Tamagawa ~ Yakeyama ~ Lake hopane ratios were similar within the sample. Thus, Katanuma > Tateyama-1 ~ Tateyama-2. here we discussed (22S/22R)-17~t(H),21#(H)-30,31Normal alkenoic acids are less stable as compared bishomohopane ((22S/22R)-C32 hopane) ratios which with those of n-alkanoic acids, and thus the n- ranged from 0.85 to 1.5 (Table 4). The (20S/20R)-C29 alkenoic/n-alkanoic acid ratios may reflect the rela- sterane ratios ranged from 0.25 to 0.80 (Table 5). tive abundances of recently produced and degraded These results are similar to those of the calculated organic components. The F/fl6:l/F/Cl6 and nCls:,/nCi8 (22S/22R)-Cs2-hopane ratios (1.0-1.4) and acid ratios for the sediment samples from the hydro- (20S/20R)-C29 sterane ratios (1.0) for the water samthermal environments are relatively high, ranging ples in the marine hydrothermal environment disfrom 0.023 and 0.83 and from 0.84 to 4.0, respectively cussed above (Brault et al., 1988). The epimerizations (Table 6), which are similar to those for a of triterpanes and steranes suggest that the thermal marine hydrothermal sediment calculated from the influences on the maturity of organic matter increases East Pacific Rise, near 13°N ( n C l 6 : l / n C l 6 , 0.26; according to following orders: (3-yunuma Pond < nC~8:,/nCls, 0.86, Brault et al., 1984). These results Yakeyama ~ Tamagawa < Tateyama-I ~ Tateyamarevealed that fresh organic matter is supplied con- 2 < Lake Katanuma. However, large heat sources tinuously by in situ microbial activity and vascular are absent in Lake Katanuma. Hence, this result

Hydrocarbons and fatty acids in inland hydrothermal environments supports again that a part of hydrocarbons is due to the contamination of runoff of asphalted roads and car parks in the shore of the lake, The (22S/22R)-C~2 hopane ratios reached near thermal equilibrium value (1.5) in the Tateyama-1 and -2, and Lake K a t a n u m a samples, while the (20S/20R)-C29 sterane ratios did not. These results can be explained by the differences of activation energy for epimerization between triterpanes and steranes, because Suzuki (1984) reported that the activation energy for the epimerization of (22R)to (22S)-C32 hopane (98kJ/mol) is much smaller than that for the (20R)- to (205)-C29 sterane (147 kJ/mol). CONCLUSIONS The features of hydrocarbons and fatty acids in the sediment samples from the inland acid hydrothermal environments can be summarized as follows. (1) The features of normal and isoprenoidal alkanes, and fatty acids are generally similar to those in common inland aquatic sediments except for the occurrence of squalane. (2) Organic components are derived from mixed sources of archaebacteria, bacteria, cyanobacteria, microalgae and the waxes of vascular plants. The contribution of vascular plants for the O-yunuma Pond sediment was considerably high, whereas microbial contribution for the Tateyama hot water pool sediments were relatively high. (3) The concentrations of hydrocarbons and fatty acids were considerably low, suggesting the low primary productivity of acid hydrothermal environments. (4) Relatively high n-alkenoic/n-alkanoic acid ratios indicate that fresh organic matter is supplied continuously by in situ microbial activity and vascular plants around the sedimentary environments. (5) The epimerization of triterpanes and steranes showed that thermal alteration of organic matter increases with the following orders: O - y u n u m a Pond < Yakeyama ~ Tamagawa < Tateyama-I ~ Tateyama-2. REFERENCES

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