TY - JOUR
T1 - Origin of dissolved salts in a large, semi-arid groundwater system
T2 - Murray Basin, Australia
AU - Herczeg, A. L.
AU - Dogramaci, S. S.
AU - Leaney, F. W.J.
PY - 2001
Y1 - 2001
N2 - Hypotheses to explain the source of the 1011 tons of salt in groundwaters of the Murray Basin, southeastern Australia, are evaluated; these are (a) mixing with original sea water, (b) dissolution of salt deposits, (c) weathering of aquifer minerals and (d) acquisition of solutes via rainfall. The total salinity and chemistry of many groundwater samples are similar to sea-water composition. However, their stable isotopic compositions (δ18O= -6.5‰; δ2H = -35) are typical of mean winter rainfall, indicating that all the original sea water has been flushed out of the aquifer. Br/Cl mass ratios are approximately the same as sea water (3.57 × 10-3) indicating that NaCl evaporites (which have Br/Cl<10-4) are not a significant contributor to Cl in the groundwater. Similarly, very low abundances of Cl in aquifer minerals preclude rock weathering as a significant source of Cl. About 1.5 million tons of new salt is deposited in the Murray-Darling Basin each year by rainfall. The groundwater chemistry has evolved by a combination of atmospheric fallout of marine and continentally derived solutes and removal of water by evapo-transpiration over tens of thousands of years of relative aridity. Carbonate dissolution/precipitation, cation exchange and reconstitution of secondary clay minerals in the acquifers results in a groundwater chemistry that retains a 'sea-water-like' character.
AB - Hypotheses to explain the source of the 1011 tons of salt in groundwaters of the Murray Basin, southeastern Australia, are evaluated; these are (a) mixing with original sea water, (b) dissolution of salt deposits, (c) weathering of aquifer minerals and (d) acquisition of solutes via rainfall. The total salinity and chemistry of many groundwater samples are similar to sea-water composition. However, their stable isotopic compositions (δ18O= -6.5‰; δ2H = -35) are typical of mean winter rainfall, indicating that all the original sea water has been flushed out of the aquifer. Br/Cl mass ratios are approximately the same as sea water (3.57 × 10-3) indicating that NaCl evaporites (which have Br/Cl<10-4) are not a significant contributor to Cl in the groundwater. Similarly, very low abundances of Cl in aquifer minerals preclude rock weathering as a significant source of Cl. About 1.5 million tons of new salt is deposited in the Murray-Darling Basin each year by rainfall. The groundwater chemistry has evolved by a combination of atmospheric fallout of marine and continentally derived solutes and removal of water by evapo-transpiration over tens of thousands of years of relative aridity. Carbonate dissolution/precipitation, cation exchange and reconstitution of secondary clay minerals in the acquifers results in a groundwater chemistry that retains a 'sea-water-like' character.
UR - http://www.scopus.com/inward/record.url?scp=0035142669&partnerID=8YFLogxK
U2 - 10.1071/MF00040
DO - 10.1071/MF00040
M3 - Article
AN - SCOPUS:0035142669
SN - 1323-1650
VL - 52
SP - 41
EP - 52
JO - Marine and Freshwater Research
JF - Marine and Freshwater Research
IS - 1
ER -