1987: Denmark River. Pesticide detected: Dieldrin, Chlordane

Preliminary study of pesticide residues in rivers and estuaries of WA (unpublished report)

Water and sediment samples were collected over two sampling periods from several estuaries and their associated rivers in mid-1987. The samples were analysed for all organochlorine and organophosphate insecticides and selected herbicides.

The sediments did not contain detectable quantities of pesticides, with the exception of the Denmark River containing 0.1 mg/kg chlordane and the Sleeman River which contained 0.04 mg/kg dieldrin. Unfortunately, the limit of detection in sediments (0.01 mg/kg) was four orders of magnitude higher than the limit in water (0.001 ug/L).

In the estuarine and river waters, no herbicides or organophosphorus residues were detected. Organochlorine residues were found in all samples. Levels which exceeded the EPA criteria predominated at the first sampling time (after the first river flows for the season). The highest level of each chemical found is shown in Table 7, with the source of the sample.

Table 7. Highest levels of OC Pesticides found in SW river sources.

Pesticide                Level ug/L                Source

DDT                        0.026                        mouth, Blackwood River

Heptachlor             0.007                        upper, Blackwood River

Chlordane              0.021                         upper, Blackwood River

Dieldrin                  0.009                         mouth, Denmark River

On the basis of the number of samples which exceeded the EPA criteria for at least one of the above pesticides, the most contaminated river systems were the Blackwood, Denmark and Hay. The Harvey, Carbunup, Sleeman, Austin, Serpentine, King, Robinson and Scott were much less contaminated. No samples exceeding the EPA criteria were found in the Murray and Kalgan river systems.

P43 Monitoring Pesticides – A Review. A Report to the Environmental Protection Authority by Peter A Rutherford. December 1989