Table 1. Mean concentrations (mg · kg⁻¹ dry weight) of trace metals in sediment samples.

	Arsenic	Cadmium	Copper	Lead	Zinc
ANZECC ISQG-Low	20	1.5	65	50	200
ANZECC ISQG-High	70	10	270	220	410
Humber Drain	4.7	0.32	16.7	32	310*
Humber Estuary	3.7	0.018	4.7	9.9	57
Old Tutaekuri Riverbed	4.7	0.127	13.9	16.1	280*
Old Tutaekuri Estuary	3	0.024	4.4	7.3	47
Waitangi Estuary	6.4	0.079	11.9	15.3	61

Notes:

Analyses from the four sites of the Ahuriri Estuary, and from the reference site, Waitangi Estuary. The ANZEEC Interim Sediment Quality Guidelines (ISQG) represent levels above which there is a low probability of biological effects (ISQG-Low) and high probability of biological effect (ISQG High). Analyses above thresholds values are indicated as * for ISQG-low.