A. Vengosh et al., Geochemical and boron, strontium, and oxygen isotopic constraints on the origin of the salinity in groundwater from the Mediterranean coast of Israel, WATER RES R, 35(6), 1999, pp. 1877-1894
In order to identify the origin of the salinity and formation of saline plu
mes in the central part of the Mediterranean coastal aquifer of Israel, we
determined the elemental and boron, strontium, and oxygen isotopic composit
ions of fresh and brackish groundwater (Cl up to 1500 mg/L). We distinguish
between two key anthropogenic sources: (1) sewage effluents used for irrig
ation with high Na/Cl, SO4/Cl, and B/Cl ratios and low Br/Cl ratios relativ
e to seawater ratios, low delta(11)B values (0-10 parts per thousand) and h
igh delta(18)O values (>-4 parts per thousand); and (2) imported water from
the Sea of Galilee that is artificially recharged to the aquifer with high
Br/Cl (3 x 10(-3)) and delta(18)O values (-1 parts per thousand) and a low
Sr-87/Sr-86 ratio of 0.70753. The brackish groundwater from the saline plu
mes have relatively low Na/Cl ratios (0.5-0.8) and high Ca/Mg, Mg/Cl, and C
a/(SO4 + HCO3) (>1) ratios relative to seawater ratios; marine SO4/Cl and B
r/Cl ratios; delta(11)B values of 24.8-49.9 parts per thousand; delta(18)O
Of -2.95 parts per thousand to -4.73 parts per thousand; and Sr-87/Sr-86 ra
tios of 0.708275-0.708532, The composition of most of the investigated grou
ndwater from the saline plumes differs from those of the anthropogenic sour
ces, imported water, fresh uncontaminated groundwater (Sr-87/Sr-86 of 0.708
66, delta(11)B of 20-30 parts per thousand), and saline water from the adja
cent Eocene aquitard. Only in areas of artificial recharge does local groun
dwater have high Br/Cl and delta(18)O values that are typical to the Sea of
Galilee. The linear relationships between chloride and most of the ions, i
ncluding B and Sr, the relatively high delta(11)B (>30 parts per thousand)
and low delta(18)O (<-4 parts per thousand) values, and the chemical signat
ure of the saline plumes (e.g., marine Br/Cl and SO4/Cl ratios), suggest th
at (1) mixing processes control the chemical composition of the brackish wa
ter within the aquifer, and (2) the saline postulated end-member has a chem
ical composition that resembles modified seawater with a marine and higher
delta(11)B values, and a Sr-87/Sr-86 ratio of <0.7083. We propose that most
of the salinization phenomena and the formation of saline plumes in the in
ner parts of the coastal aquifer are derived from upconing of underlying na
tural saline water bodies and enhanced by overexploitation and draw-down of
the overlying fresh groundwater.