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Organic matter composition in coastal marine sediments from different depositional areas, Italy
The Science of the Total Environment, Elsevier
Science
Publishers
B.V.,
62 (1987) 477-479
Amsterdam
- Printed
ORGANIC MATTER COMPOSITIONIN DEPOSITIONALAREAS, ITALY.*
477
in The Netherlands
COASTAL MARINE SEDIMENTSFROMDIFFEREW
S. GUERZONIand G. ROVATTI Istituto per la Geologia Marina, C.N.R., via Zamboni n.65, 40127 BOLOGNA (Italy)
SUMMARY New data on degradation products of organic matter in marine and stream sediments of two areas of the Mediterranean Sea are presented. Alkaline extractable humic substances (THS) comprise from 10 to 55 % of the total organic carbon. The different values of THS and of the "degree of humification" (THWTOM) indicate the importance of grain-size, sedimentation rate and C/N ratios in the studied processes. INTRODUCTION ANDSTUDYAREA Bottom samples from two distinct areas were studied: (a) the Northern Adriatic Sea , around the PO River delta and (b) the Tyrrhenian Sea, in front of Tiber River (Fig. 1). One transect (from inside the river, offshore to the shelf) ineachareaand some depthhorizonsofacore (79-05) from the prodeltaic area of the PO River were choosen to compare the effect of different sedimentation environments on the humification processes The areas have different bottom morphology, hydrological conditions, inputs of organic matter and pollutants. The sedimentation rates differ, as well, being l-3 cm/y and several mm/y for Adriatic and Qrrhenian Sea, respectively (ref.1 and 2).
Fig.
1.
Location map of the areas studied (@;o= surface samples;A= site). The dashed lines indicate the bathymetry (in meters).
*Publication 004%9697/87/$03.50
n.
603
of
0 1987
the
Istituto
Elsevier
per Science
la
Publishers
Wlogia B.V.
Marina,
C.N.R.,
Bologna.
core
478 TABLE1 Total amount of humic substances (THS), total organic matter (TOM = total nic carbon x 1.8) and other analyzed parameters. SAMPLE N.Adriatic Sea P 64 (O-3 a
Pp 2 P26
II ”
"
P 24 Prodelta'Po o-3 15-19 30-33 40-43 147-150
cm " It It It
THS
TOM THWTCM C/N
w/g
w/g
4.9 6.2 ::; 4.6
12.2 15.1 25 17:8 15.7
0.40 0.41 0.48 0.42 0.29
3.1 3.3 2.9 2.5 1.4
14.9 31.1 15.5 14.2 8.5
0.21 0.11 0.19 0.18 0.16
5.4 0.6 19.2
21.6 11.7 34.6 14.0 12.2 13.0
0.25 0.05 0.55 0.04 0.46 0.46
5.8 t::: 2::
TON sand % 1.17 1.25 0.29 1.34 1.29
79-05
Thyrr&ian Sea T 42 (O-3 5 T 23 U T 24 " T 44 n T 45 11 T2U "
;:i.
2; 5:3
1.35 2.13 1.19 1.26 0.88
8.3 32.5 12.9 78.0 10 6 8 8
1.44 0.20 2.11 0.10 0.64 0.82
2
orga-
23
8;
1
20 1
0 2 : 10 62 13 65 8 36
METHODS Humic substances were isolated from the sediments using alkaline extraction, following the procedures described in ref. 3, excluding the fractionation step. 'Ihe carbon and nitrogen content was determinated on freeze-dried samples using a GIN-Analyzer (Carlo Erba, mod.1106, ref.4). RESULTS All the sediments studied have an organic C content between 0.1 and 2.7 %. According to Giordani (ref. 51, most of the sedimented organic matter in the Adriatic Sea is mainly of autochtonous origin ( C/N values range between 4.7 and 8.1; avg.= 7.1). Some of the nearshore Tyrrhenian sediments, on the other hand, show a combination of high org C concentration and high org C relative to organic N (TON), whilst the offshore samples have C/N values of 8. Relatively low amounts of total humic substances (THS) were observed, compared to sediments from other areas (ref. 6); but our data are consistent with the Mediterranean Sea data published by Poutanen in the same work. The THS values show more significant diversities inside the same area than between the Adriatic and Tyrrhenian areas. For the surface sediments, an inverse correlation with the sand content is evident . On the other hand, the proportion of alkaline extractable humic substances to the total organic matter (THS/TOM= "degree of humificationl') better distinguish the two sedimentation areas and the core site. Low values ofTHS/TOM are found in the core (all horizons) and in the near-
479 shore samples of the Tyrrhenian Sea. The core data are partially in contrast with findings of Poutanen (ref. 6), who observed a slight increase of the proportion as a function of depth. The homogeneity of the values in our core is probably due to the very high sedimentation rate (2-4 cm/year; ref.71, which reduces the degradation processes. Low values are also found in samples with high C/N ratios and a sand content 3 60 f6 (T23, T44). In contrast, another nearshore sample (T 24) with C/N =13 shows a combination of high THS content with high proportion of THS to TOM, showing the difference in the rapidity of formation and incorporation of the degradation products. In the N.Adriatic and offshore Tyrrhenian surficial sediments the THS comprise 30-45 % of the TOM, with low variability. CONCLUSIONS Alkaline extractable humic substances (THS) in the studied areas are mainly related to TOMcontent and the grain-size of the sediments. The degree of humification (THS/TOM)enables to distinguish between Adriatic and Tyrrhenian sedimentation areas and gives information, together with C/N ratios, on the origin of the organic matter. To better explain the composition and the structure of the organic matter in the marine sediments, studies on the ratio of fulvic acids to humic acids and with nuclear magnetic resonance spectroscopy are underway. REFERENCES S. Albertazzi, R.F. Bopp, M. Frignani, 0. Hieke Merlin, L. Menegazzo Vitturi, M. Ravaioli, H.J. Simpson, L. Tassi Pelati and C. Triulzi, Cs-137 as a tracer for processes of marine sedimentation in the vicinity of the PO River delta (Northern Adriatic Sea), Mem. Sot. Geol. It.. 27 (1984) 447-459. G. Bortoluzzi, F. Frascari, S. Guerzoni, N: Incremona, M. ~Ravaioli and G. Rovatti, Some sedimentological and chemical features of the seafloor in front of the Tiber River, Geogr. Fis. Dinam. Quat., 5 (1982) 120-128. E.L. Poutanen and R.J. Morris, The occurence of high molecular weight humic compounds in the organic-rich sediments of the Peru continental shelf, Gceanol. Acta, 6 (1983) 21-28. P.N. Froelich, Analysis of organic carbon in marine sediments, Limnol. Gceanear., 25(3) (1980) 564-572. P. %iordsni and L. .A&iolini, Chemical parameters characterizing the sedimentary environment in a NWAdriatic coastal area (Italy), Estuar. Coast. Shelf Sci., 17 (1983) 159-167. E.L. Poutanen, Humic and fulvic acids in marine sediments, Finnish Marine Research, No. 251, 1985, pp.l-45. S. Guerzoni, M. Ravaioli, G. Rovatti and D.O. Suman, Comparison of 210 Pb trace metals profiles and river discharge in a core off the PO della Pila river mouth (Italy), Proc. VIIth Workshop on Mar. Poll., Lucerne 11-13 october 1984, ICSEM(1985) 303-307.
Science
Publishers
B.V.,
62 (1987) 477-479
Amsterdam
- Printed
ORGANIC MATTER COMPOSITIONIN DEPOSITIONALAREAS, ITALY.*
477
in The Netherlands
COASTAL MARINE SEDIMENTSFROMDIFFEREW
S. GUERZONIand G. ROVATTI Istituto per la Geologia Marina, C.N.R., via Zamboni n.65, 40127 BOLOGNA (Italy)
SUMMARY New data on degradation products of organic matter in marine and stream sediments of two areas of the Mediterranean Sea are presented. Alkaline extractable humic substances (THS) comprise from 10 to 55 % of the total organic carbon. The different values of THS and of the "degree of humification" (THWTOM) indicate the importance of grain-size, sedimentation rate and C/N ratios in the studied processes. INTRODUCTION ANDSTUDYAREA Bottom samples from two distinct areas were studied: (a) the Northern Adriatic Sea , around the PO River delta and (b) the Tyrrhenian Sea, in front of Tiber River (Fig. 1). One transect (from inside the river, offshore to the shelf) ineachareaand some depthhorizonsofacore (79-05) from the prodeltaic area of the PO River were choosen to compare the effect of different sedimentation environments on the humification processes The areas have different bottom morphology, hydrological conditions, inputs of organic matter and pollutants. The sedimentation rates differ, as well, being l-3 cm/y and several mm/y for Adriatic and Qrrhenian Sea, respectively (ref.1 and 2).
Fig.
1.
Location map of the areas studied (@;o= surface samples;A= site). The dashed lines indicate the bathymetry (in meters).
*Publication 004%9697/87/$03.50
n.
603
of
0 1987
the
Istituto
Elsevier
per Science
la
Publishers
Wlogia B.V.
Marina,
C.N.R.,
Bologna.
core
478 TABLE1 Total amount of humic substances (THS), total organic matter (TOM = total nic carbon x 1.8) and other analyzed parameters. SAMPLE N.Adriatic Sea P 64 (O-3 a
Pp 2 P26
II ”
"
P 24 Prodelta'Po o-3 15-19 30-33 40-43 147-150
cm " It It It
THS
TOM THWTCM C/N
w/g
w/g
4.9 6.2 ::; 4.6
12.2 15.1 25 17:8 15.7
0.40 0.41 0.48 0.42 0.29
3.1 3.3 2.9 2.5 1.4
14.9 31.1 15.5 14.2 8.5
0.21 0.11 0.19 0.18 0.16
5.4 0.6 19.2
21.6 11.7 34.6 14.0 12.2 13.0
0.25 0.05 0.55 0.04 0.46 0.46
5.8 t::: 2::
TON sand % 1.17 1.25 0.29 1.34 1.29
79-05
Thyrr&ian Sea T 42 (O-3 5 T 23 U T 24 " T 44 n T 45 11 T2U "
;:i.
2; 5:3
1.35 2.13 1.19 1.26 0.88
8.3 32.5 12.9 78.0 10 6 8 8
1.44 0.20 2.11 0.10 0.64 0.82
2
orga-
23
8;
1
20 1
0 2 : 10 62 13 65 8 36
METHODS Humic substances were isolated from the sediments using alkaline extraction, following the procedures described in ref. 3, excluding the fractionation step. 'Ihe carbon and nitrogen content was determinated on freeze-dried samples using a GIN-Analyzer (Carlo Erba, mod.1106, ref.4). RESULTS All the sediments studied have an organic C content between 0.1 and 2.7 %. According to Giordani (ref. 51, most of the sedimented organic matter in the Adriatic Sea is mainly of autochtonous origin ( C/N values range between 4.7 and 8.1; avg.= 7.1). Some of the nearshore Tyrrhenian sediments, on the other hand, show a combination of high org C concentration and high org C relative to organic N (TON), whilst the offshore samples have C/N values of 8. Relatively low amounts of total humic substances (THS) were observed, compared to sediments from other areas (ref. 6); but our data are consistent with the Mediterranean Sea data published by Poutanen in the same work. The THS values show more significant diversities inside the same area than between the Adriatic and Tyrrhenian areas. For the surface sediments, an inverse correlation with the sand content is evident . On the other hand, the proportion of alkaline extractable humic substances to the total organic matter (THS/TOM= "degree of humificationl') better distinguish the two sedimentation areas and the core site. Low values ofTHS/TOM are found in the core (all horizons) and in the near-
479 shore samples of the Tyrrhenian Sea. The core data are partially in contrast with findings of Poutanen (ref. 6), who observed a slight increase of the proportion as a function of depth. The homogeneity of the values in our core is probably due to the very high sedimentation rate (2-4 cm/year; ref.71, which reduces the degradation processes. Low values are also found in samples with high C/N ratios and a sand content 3 60 f6 (T23, T44). In contrast, another nearshore sample (T 24) with C/N =13 shows a combination of high THS content with high proportion of THS to TOM, showing the difference in the rapidity of formation and incorporation of the degradation products. In the N.Adriatic and offshore Tyrrhenian surficial sediments the THS comprise 30-45 % of the TOM, with low variability. CONCLUSIONS Alkaline extractable humic substances (THS) in the studied areas are mainly related to TOMcontent and the grain-size of the sediments. The degree of humification (THS/TOM)enables to distinguish between Adriatic and Tyrrhenian sedimentation areas and gives information, together with C/N ratios, on the origin of the organic matter. To better explain the composition and the structure of the organic matter in the marine sediments, studies on the ratio of fulvic acids to humic acids and with nuclear magnetic resonance spectroscopy are underway. REFERENCES S. Albertazzi, R.F. Bopp, M. Frignani, 0. Hieke Merlin, L. Menegazzo Vitturi, M. Ravaioli, H.J. Simpson, L. Tassi Pelati and C. Triulzi, Cs-137 as a tracer for processes of marine sedimentation in the vicinity of the PO River delta (Northern Adriatic Sea), Mem. Sot. Geol. It.. 27 (1984) 447-459. G. Bortoluzzi, F. Frascari, S. Guerzoni, N: Incremona, M. ~Ravaioli and G. Rovatti, Some sedimentological and chemical features of the seafloor in front of the Tiber River, Geogr. Fis. Dinam. Quat., 5 (1982) 120-128. E.L. Poutanen and R.J. Morris, The occurence of high molecular weight humic compounds in the organic-rich sediments of the Peru continental shelf, Gceanol. Acta, 6 (1983) 21-28. P.N. Froelich, Analysis of organic carbon in marine sediments, Limnol. Gceanear., 25(3) (1980) 564-572. P. %iordsni and L. .A&iolini, Chemical parameters characterizing the sedimentary environment in a NWAdriatic coastal area (Italy), Estuar. Coast. Shelf Sci., 17 (1983) 159-167. E.L. Poutanen, Humic and fulvic acids in marine sediments, Finnish Marine Research, No. 251, 1985, pp.l-45. S. Guerzoni, M. Ravaioli, G. Rovatti and D.O. Suman, Comparison of 210 Pb trace metals profiles and river discharge in a core off the PO della Pila river mouth (Italy), Proc. VIIth Workshop on Mar. Poll., Lucerne 11-13 october 1984, ICSEM(1985) 303-307.