Trace Elements

a. Dissolved Reactive Phosphorous

The dissolved reactive phosphorous (DRP) concentrations (Figure 6.18) in Bore 401A were higher than those observed in the other shallow ground water bores.

The mean DRP concentration in Bore 401A was 2.2 g m^-3 compared to the other shallow ground water bores which ranged from a mean of 0.04 g m^-3 in Bore 402A to 0.02 g m^-3 in Bores 405A and 406A.

Dissolved Reactive Phosphorous

0 1 2 3

31/03/99 25/12/01 Date 20/09/04 17/06/07

DRP (g m-3)

Bore 401A (North of Landfill) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill) Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.18: Dissolved Reactive Phosphorous concentrations in the shallow ground water bores.

Brown & Elmsly (1987) reported phosphorous was generally present in low levels in the Te Hapara Sands aquifer typically ranging between 0.0-0.15 g m^-3 and slightly higher in the Awapuni area ranging from 0.16-0.20 g m^-3. Bore BG1 had a mean of 0.2 g m^-3 and Bore BG2 had a mean of 0.01 g m^-3 which was similar to the phosphate concentrations reported in the Paokahu shallow groundwater bores (with the exception of Bore 401A).

Bore 401A is located in farmland to the north of the landfill in the Shallow Estuarine Silts. The land surrounding the bore was under different management to the landfill and surrounding areas and was used for grazing cattle and sheep and cropping in the summer months. The high DRP concentrations can’t be the result of a leachate in the aquifer as the leachate DRP concentrations were lower than those found in Bore 401A. The high DRP concentrations in Bore 401A could be

caused by higher application rates of phosphate fertilizers leaching into the shallower Estuarine Silts.

b. Boron

The boron concentrations (Figure 6.19) in Bores 404B, 406A and 407A were very similar and all follow the same trend of minor fluctuations with concentration ranging between 1.8 and 2.68 g m^-3. The boron concentrations in Bores 401A, 403A and 405A were also similar and ranged from 0.069 – 0.5 g m^-3. The Boron concentrations in Bore 402A appear to be increasing over time.

Dissolved Boron

0 1 2 3 4

31/03/99 25/12/01 Date 20/09/04 17/06/07

Boron (g m-3)

Bore 401A (North of Landfil) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill)

Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.19: Dissolved boron concentrations in the shallow ground water bores.

There were no reported boron concentrations available for the Te Hapara Sands aquifer or the background bores to compare against the Paokahu shallow water bores. The boron concentrations in Bore 402A increased over time and with a mean of over 3 g m^-3 since September 2004, which is higher than the boron concentrations found in both leachate bores. Typical sea water has a boron concentration of 4.5 g m^-3 (Anderson; 2003) so the high concentration may be due to sea water infiltration as Bore 402A also had high EC, Na, K and Cl concentrations

c. Iron

The highest iron concentrations (Figure 6.20) were observed in Bore 401A which had a mean value of 0.78 g m^-3. Apart from the samples taken from Bore 405A between 2000-2001 all other recorded concentrations were below the detection limit of the test.

Dissolved Iron

0 1 2 3 4

31/03/99 25/12/01 Date 20/09/04 17/06/07

Iron (g m-3)

Bore 401A (North of Landfil) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill)

Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.20: Dissolved iron concentrations in the shallow ground water bores.

Brown & Elmsly (1987) reported iron concentrations in the Te Hapara Sands aquifer were variable but typically ranged from 0-7 g m^-3 and have been reported to increase to 8-16 g m^-3 in the Matawhero/Awapuni areas. The mean iron concentration in bore BG1 was 4.3 g m^-3 and 12.4 g m^-3 in bore BG2. The iron concentrations in the Paokahu shallow bores (typically below detection limits in most bores) were generally low compared to those typically reported for the Te Hapara Sands aquifer.

The only bore where iron was consistently detected was Bore 401A (north of the landfill) which is located in the Shallow Estuarine Silts.

d. Manganese

The lowest dissolved manganese concentrations (Figure 6.21) were observed in Bore 403A where the concentrations ranged from <0.0005 – 0.004 g m^-3. The highest concentrations were recorded in Bore 407A where the concentrations ranged from 1.03 – 1.35 g m^-3.

Dissolved Manganese

0.0 0.5 1.0 1.5

31/03/99 25/12/01 Date 20/09/04 17/06/07

Manganese (g m-3)

Bore 401A (North of Landfil) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill)

Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.21: Dissolved manganese concentrations in the shallow ground water bores.

There were no generic manganese concentrations available for the Te Hapara Sands aquifer but data is available for Bores BG1 (mean 0.04 g m^-3) and BG2 (mean 1.16 g m^-3). The manganese concentrations in the Paokahu shallow ground water bores were generally within the range shown in the two background bores.

The two bores not located in the Te Hapara Sands aquifer (Bores 401A and 403A), had the lowest manganese concentrations. The high manganese concentrations in the Te Hapara Sands aquifer were not likely to be the result of sea water infiltration as typical sea water has a manganese concentration of 0.004 g m^-3 (Anderson, 2003) which is lower than found in the Te Hapara Sands bores.

e. Copper

Dissolved copper concentrations (Figure 6.22) were below the detection limit of 0.005 g m^-3 in bores 402A, 403A, 404B, 405A and 407A. Bore 401A (Shallow Estuarine Silts) was the only bore where the copper concentrations were consistently above the detection limit of the test.

Dissolved Copper

0.000 0.001 0.002 0.003 0.004 0.005

31/03/99 25/12/01 Date 20/09/04 17/06/07

Copper (g m-3)

Bore 401A (North of Landfil) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill)

Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.22: Dissolved copper concentrations in the shallow ground water bores.

f. Zinc.

Dissolved zinc concentrations (Figure 6.23) above the detection limit were only observed in Bores 401A, 405A and 406A. Bore 401A (Shallow Estuarine Silts) was the only bore where zinc concentrations were consistently above the detection limits of the test.

Zinc has previously been detected in the Te Hapara Sands aquifer at concentrations of <0.02 – 0.12 g m^-3 (Brown & Elmsly, 1987). The zinc concentrations in the shallow ground water bores of the Te Hapara Sands aquifer were all lower than the zinc concentrations reported by Brown & Elmsly (1987).

Dissolved Zinc

0.00 0.01 0.02 0.03 0.04

31/03/99 25/12/01 Date 20/09/04 17/06/07

Zinc (g m-3)

Bore 401A (North of Landfill) Bore 402A (Southwest of Landfill) Bore 403A (South of Landfill) Bore 404B (Centre of Landfill) Bore 405A (East of Landfill) Bore 406A (Northwest Boundry of Landfill) Bore 407A (Northeast Boundry of Landfill)

Figure 6.23: Dissolved zinc concentrations in the shallow ground water bores.

g. Other Trace Elements

Dissolved cadmium, chromium, lead, mercury, nickel and selenium were also measured. Selenium (detection limit <0.001 g m^-3) and mercury (detection limit

<0.00008 g m^-3) concentrations were below the detection limit in all bores throughout the sampling period. Dissolved cadmium, chromium, lead and nickel were below the detection limit with a few exceptions (Figures 6.24, 6.25, & 6.26).

The lead detected in Bore 404B corresponds to the time when the leachate lead concentrations were greatest (1999/2000) and could indicate leachate entering the ground water under the landfill.

Lead

0.000 0.001 0.002 0.003 0.004 0.005 0.006

31/03/1999 25/12/2001 20/09/2004 17/06/2007

Date Lead (g m-3)

Bore 401A (North of landfill) Bore 404B (Centre of landfill) Bore 405A (East of landfill)

Figure 6.24: Dissolved lead concentrations in the shallow ground water bores.

Chromium

0.000 0.001 0.002 0.003 0.004 0.005 0.006

31/03/1999 25/12/2001 20/09/2004 17/06/2007

Date Chromium (g m-3)

Bore 401A (North of landfill)

Figure 6.25: Dissolved chromium concentrations in the shallow ground water bores.

Dissolved Nickel

0 0.002 0.004 0.006 0.008 0.01

31/03/99 25/12/01 20/09/04 17/06/07

Date Dissolved Nickel (g m-3)

Bore 404B (Centre of Landfill) Bore 405A (East of Landfill)

Bore 407A (Northeast Boundry of Landfill)

Figure 6.26: Dissolved nickel concentrations in the shallow ground water bores.

6.4.1.8 Semi Volatile Organic Compounds

No SVOCs were detected in any of the groundwater samples.

6.4.2 Deep Groundwater Bores