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This indicator measures nutrients in
groundwater expressed as the concentration of nitrates and nitrites
(NOx-N) and is measured in milligrams / litre (mg/l). NOx-N
concentrations below 6 mg/l are said to have negligible health risk,
concentrations between 6 and 10 mg/l present no significant risk to
human health when ingested, while concentrations above 10mg/l can
induce both chronic and acute risk to human health (WRC, 1998).
Acceptable concentrations of NOx-N in groundwater are therefore
levels
less than
6mg/l.
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| Assessment of
Data |
Groundwater resources around the Elands River
and Rhenosterkop Dam in the middle Olifants Water Management Area
(WMA) contained NOx-N concentrations in excess of 24 mg/l in 2001,
making groundwater in the Springbok Flats Groundwater Region
unsuitable for domestic purposes. There has however, been a decrease
in concentration since 1996 and a similar decrease in
concentrations is evident in the Northern Lebombo Groundwater Region
in the east of the Sabie WMA. It should be noted that elevated
nitrate concentrations in the Springbok Flats area are typically
natural and not attributed to human influences. Evidence of
increases in groundwater nutrient concentrations can be seen in the
other 6 groundwater regions in Mpumalanga, namely the Eastern
Bushveld, Eastern Bankenveld, Lowveld, North East Middelveld,
Central Highveld and Eastern Highveld Groundwater Regions. The 2001
concentrations are still within acceptable levels for domestic
purposes (i.e. below 10 mg/l) and do not pose a threat to human
health if ingested. The following map (figure 9.10) shows the
various concentrations of
groundwater nutrients in
Mpumalanga for 1996 and 2001.
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