| en |
Assessing nitrate origin in a volcanic aquifer using a dual isotope approach
Mongelli, G.; Paternoster, M. & Sinisi, R.
Abstract
Identifying the origin of nitrate is important for
the control and management of groundwater quality in
aquifer systems. In the southern Apennines (Italy), the
Mount Vulture volcanic aquifer is a large and valuable
resource of potable and mineral water supply. Unfortu-
nately, signs of anthropogenic impact, especially nitrogen
contamination, have recently become evident. In this study,
and for the first time, stable isotope ratios (
δ
15
N and
δ
18
O)
of NO
3
-
were determined in groundwater to identify their
origins and evaluate the presence of transformation pro-
cesses. The Mount Vulture groundwaters are meteoric in
origin, as demonstrated by measurements of
δ
D and
δ
18
O,
and can be divided into two distinct areas based on their
NO
3
-
content. In the southeastern area, characterized by
active agricultural land use, the high NO
3
-
content and the
δ
15
N-NO
3
isotopic values are due to anthropogenic con-
tamination (inorganic fertilizer). In groundwaters from the
western area, the NO
3
-
contents below 4 mg/L and the
δ
15
N-NO
3
values can be associated at organic soil N.
Evidence for local denitrification may be assumed in a few
groundwater samples of the western area showing rela-
tively heavy
δ
15
N values and low concentrations of nitrate.
Finally, the low measured
δ
18
O values indicate that nitri-
fication occurred in both investigated areas.
Keywords
Anthropogenic contamination; Groundwater; Nitrification; Nitrogen and oxygen isotopes
|
