The use of sulfur and strontium isotopes as tracers for the source/s of
water contaminants have been applied to the water of the Llobregat River
system (NE Spain). Surface water samples from June 1997 were collected
from the Llobregat River and its main tributaries and creeks. The
chemistry of most stream waters are controlled mainly by the weathering
of Tertiary chemical sediments within the drainage basin. The largest
variation in delta(34)S values were found in the small creeks with
values ranging from -9.9 to 15parts per thousand, whilst in the main
river channels values ranged from 6.3 to 12.4parts per thousand. The
Sr-87/Sr-86 ratio for dissolved strontium ranged from 0.70795 for a
non-polluted site to 0.70882 for a polluted one. Most of the waters with
high NO3 and low Ca/Na ratio converge to the same Sr-87/Sr-86 value,
pointing to dominant pollutant end member contribution or a mixing of
pollutants with an isotopic composition around 0.7083-0.7085. Although
the concentration of the natural inputs in the river for sulfate and
strontium are high, as a result of the sulfate outcrops within the
geology of the basin, their isotopic characteristics suggest that they
can be used as a discriminating device in water pollution problems.
However to establish the detailed characteristics of the isotopes as
geochemical tools, specific high-resolution case studies are necessary
in small areas, where the inputs are well known.