This document discusses the pre-processing of groundwater data from monitoring points over eight years to measure nitrate levels. Specific water samples are selected based on nitrate, iron, and oxygen concentrations to minimize uncertainty and enable nitrate sampling years to be converted to groundwater recharge years. This allows for comparison of long-term changes in nitrogen surplus from agriculture to changes in groundwater nitrate levels. Agricultural nitrogen balances of inputs and outputs are also calculated as an indicator of nitrogen lost to the environment. Nitrate pollution levels in groundwater are then evaluated against economic growth rates to examine an environmental curve.

1. PRE-PROCESSINGOF GROUNDWATER
DATA

2. Groundwater Monitoring
Points
• toxic groundwater
• age-dated groundwater
• more than eight years of
nitrate measurements

3. • from intensive
farming
• leaching from the
root zone
• losses of N from
agricultural
practices
Due to its stability, nitrate
in toxic groundwater is
used as an indicator of
nitrate

4. SELECTION
water samples
from
toxic groundwater
based on specific
concentrations of
the redox -
sensitive
parameters
• nitrate (>1 mg l−1)
• iron(<0.2 mg l−1)
• oxygen(>1 mg l−1)
minimizes the
uncertainty in
the
determination of
the groundwater

5. enables nitrate
sampling years to be
converted to
groundwater recharge
years becomes possible to
compare long-term
changes in N surplus
in agriculture with
changes in

6. N use efficiency (NUE)
relation between the
accounted agricultural N
outputs and N inputs

7. Agricultural N balances
N inputs – N outputs = N-surplus
synthetic fertilizer, import
of animal feed, organic
waste products, net
atmospheric deposition
plant and animal products
an overall environmental indicator of the
changes and represents the amount of N not
being used by the production system and
therefore at risk of being lost to the
environment

8. Socio-economic drivers of
environmental quality
Nitrate pollution levels of
the groundwater were
evaluated against an
economic growth indicator,
national Gross Domestic
Product (GDP), to test the
evidence of an
environmental curve