Tritium age dating groundwater Reallifecams xxx
The source of elevated PONitrate versus mean residence time (MRT) and corresponding calendar year.
Green circles indicate oxic waters, red squares indicate anoxic waters, and black crosses indicate unknown.
In young groundwater that was recharged after the intensification of agriculture, nitrate, sulphate, CFC-11 and CFC-12, and pesticides are the most representative indicators for the impact of land-use intensification on groundwater quality, with 66% of the sites showing such an impact.
Elevated concentrations of nitrate in oxic groundwater allowed us to reconstruct the timing and magnitude of the impact of land-use intensification on groundwater which in New Zealand occurred in two stages.
The change in groundwater quality from pristine baseline to low–intensity impact around 1880 coincides with the start of the meat export industry.
A transition to slightly elevated concentration due to low-intensity land-use was observed in groundwater recharged since around 1880.
A sharp increase in nitrate and other agrochemicals due to high-intensity agriculture was observed in groundwater recharged since 1955.