Nitrate mass balance in agricultural areas of intensive fertilizer application: the North Maresme aquifer system case study (Spain)

Resumen

Nitrate pollution is a
worldwide problem in groundwater, as it may limit water supply and
increase health risk when high concentrations are present. The North
Maresme coastal alluvial groundwater-dependent agrosystem, one of
the most heavily nitrate polluted aquifers in Spain, is located 70
km northeast from Barcelona. Field monitoring campaigns performed in
this aquifer yielded nitrate concentrations up to ten times the
permitted limit for drinking water suggested by the World Health
Organization (50 mg/l), with a maximum concentration of 567 mg/l and
a mean of 137.5 mg/l. Nitrate contamination was quantified by means
of a mass balance, taking into account the main hydrogeological and
anthropogenic processes that control the behavior of this ion in the
aquifer, such as recharge, groundwater extraction, irrigation and
fertilizer application to crops. Nitrate balance is an integrative
approach for assessing nitrate loading based on linking different
sources of nitrates to a groundwater balance. This methodology
considers nitrate as a conservative ion because the
geological-geochemical medium behaves under oxidant conditions.
Results show that the studied aquifer system receives, yields and
retains approximately 935, 844 and 91 tons of NO3 - /year,
respectively. This methodology can be applied to other
nitrate-contaminated aquifers with similar conditions to improve
management of fertilizers practices in areas of intensive
agriculture.