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| Titel |
Origin and geochemical evolution of porewater in clay aquitards in North Jiangsu coastal plain, China |
| VerfasserIn |
Qin Ge, Xing Liang, Jing Li, Bin Ma |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103923
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| Publikation (Nr.) |
 EGU/EGU2015-3344.pdf |
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| Zusammenfassung |
| Decline of groundwater levels, resulting in water pressure decreasing, skeleton pressure
increasing and porewater releasing from clay aquitards under these conditions, may cause the
change of groundwater quality. This study provides insights into the origins and
geochemical interactions of porewater in unoxidized and nonfractured aquitards under
the influence of groundwater declining. Field investigations were conducted and a
borehole was drilled with a depth of 250m in North Jiangsu coastal plain, China. 138
porewater samples were collected for isotope analysis, and 44 water samples were
extracted from the clay for major ion analysis. Porewater, changing with the TDS
tested, showed large variations with depth through the aquitards from 0.3g/l to
26.0g/l. The water type could be classified into fresh water (3.0g/l, Cl-Na; 3-35m). The changing trend of salt-porewater was mostly
accordant with the mixing line between fresh porewater and seawater end-members.
Nevertheless molar Br/Cl ratios (3.7-6.5*10-3) were larger than those of seawater
(1.5*10-3), and δ2H and δ18O values showed depleted isotopic signatures (between
-1.0‰ and -3.5‰ and -19.1‰ and -29.3o respectively) compared to modern seawater,
indicating that salt-porewater evolved from paleo-seawater that was more saline and
subsequently diluted with fresher water over the long-term. However, fresh and
brackish porewater did not coincide with the mixing line; δ2H and δ18O values were
much lower than salt-porewater and below the global meteoric water line. Also,
molar Br/Cl ratios (0-7.3) and the trend of δ18O with chloride contents manifested
evapotranspiration might be the dominate mechanism of brackish formation. The deltas
values of Na+ (0), and molar Na/Cl ratios ( |
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