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Table 10.1: National medians and ranges for minerals, chemicals, and metals in monitored groundwater, 1995–2006

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  Sodium Chloride Sulphate Dissolved iron Dissolved manganese Arsenic Total dissolved solids

Median

15

15.3

6.5

0.03

0.01

0

149

Range
(5th–95th percentile)

4.6–117

2.8–142

0.1–44

0–5.5

0–3.6

0–0.24

64–950

Guideline level
(maximum recommended level)

200

250

250

0.2

0.04

0.4*

0.01*

1,000

Percentage of sites exceeding guideline (%)

1.9%

2.5%

0%

26.5%

33%

15%*

10.2%

4.3%

Notes:

(1) Units are in milligrams per litre.

(2) Guideline levels are for aesthetic quality defined by the drinking water standards for New Zealand unless otherwise stated (Ministry of Health, 2005).

(3) Numbers with asterisks (*) relate to health guidelines (drinking water standards for New Zealand maximum acceptable value (Ministry of Health, 2005)) not aesthetic quality.

Source: Adapted from Ministry for the Environment, in press b.