Pilot Survey of Pesticide Residues in Streams Draining a Horticultural Catchment, Piccadilly Valley, South Australia.

K Thoma. Department of Agriculture South Australia Technical Paper No. 131 June 1988

Summary

Residue concentrations from selected pesticides in waters draining the Piccadilly Valley, a horticultural catchment, were monitored from July 1984 until January 1987.

Water samples were collected fortnightly from several locations within the study catchment to assess the effects of specific land uses on water quality. Two run-off events were intensively  sampled for their full duration. Samples were also taken further downstream to assess the effects of dilution and degradation upon stream water quality. Sediment samples were collected irregularly in the study catchment and further downstream.

Pesticide residues were detected in 83.5% of all water samples and in 100% of the sediment samples. Highest concentrations were detected during the growing season and particularly during run-off events occurring shortly after  pesticide applications.

Residue concentrations of DDT and Chlorpyrifos exceeded Maximum Residue Level Recommendations from the National Health and Medical Research Council on two occasions in streams in the Piccadilly Valley...

Conclusions

The highest residue concentrations were detected from the herbicides Dachtal and Propyzamide, followed by the organochlorines Endosulfan, DDT and Lindane. These findings are in agreement with studies conducted in the United States where powder formulations of herbicides and the persistent organochlorine insecticides were found to contribute the highest pesticide residue concentrations in run-off from intensive agricultural watersheds.

Increasing residue concentrations and detection frequencies of Dachtal and Endosulfan, particularly in the 1986/87 growing season, point to an increased use in the study catchment. Erratic fluctuations of residue concentrations and detection frequencies of Chlorpyrifos, Propyzamide and Chlorothalonil made the identification of a trend in pesticide use impossible...

DDT and Chlorpyrifos residues exceeded NH&MRC Maximum Residue Level recommendations during a run-off event and once during the routine monitoring program...Higher residue concentrations, particularly for the persistent organochlorines, could accumulate in bottom sediment of Mt Bold reservoir, which acts as a sink for sediment and sediment-bound pesticides.

The organochlorine insecticides DDT, Lindane, Endosulfan and to a lesser extent the organophosphorus insecticide Chlorpyrifos were detected in sufficiently high concentrations to adversely affect aquatic environments for extended periods of time according to water quality criteria recommended by the Victorian Environment Protection Authority. Bottom feeding organisms would be exposed to high concentrations of DDT in finely textured sediment. High concentrations of a multitude of pesticides during run-off events would affect a wide range of organisms.

Cox Creek

1984/5

Chlorpyrifos: 60.87% (frequency of detection), 0.52ug/L (highest detection)

DDT and Metabolites: 69.57% (frequency of detection), 1.4ug/L (highest detection)

Lindane: 86.61% (frequency of detection), 0.32ug/L (highest detection)

Endosulfan: 8.7% (frequency of detection), 0.08ug/L (highest detection)

Parathion: 12.04% (frequency of detection), 0.48ug/L (highest detection)

Dachtal: 100% (frequency of detection), 12.5ug/L (highest detection)

Propyzamil: 52.17% (frequency of detection), 3.6ug/L (highest detection)

Chlorothalonil: 13.04% (frequency of detection), 0.09ug/L (highest detection)

1985/6

Chlorpyrifos: 33.33% (frequency of detection), 0.07ug/L (highest detection)

DDT and Metabolites: 40.74% (frequency of detection), 1.35ug/L (highest detection)

Lindane: 26.63% (frequency of detection), 0.06ug/L (highest detection)

Endosulfan: 14.81% (frequency of detection), 0.05ug/L (highest detection)

Dachtal: 92.59% (frequency of detection), 17ug/L (highest detection)

Propyzamil: 66.67% (frequency of detection), 28ug/L (highest detection)

Chlorothalonil: 3.7% (frequency of detection), 0.01ug/L (highest detection)

Vinclozolin: 72.72% (frequency of detection), 0.33ug/L (highest detection)

1986/7

Chlorpyrifos: 52.38% (frequency of detection), 0.13ug/L (highest detection)

DDT and Metabolites: 76.19% (frequency of detection), 0.55ug/L (highest detection)

Lindane: 28.57% (frequency of detection), 0.2ug/L (highest detection)

Endosulfan: 38.1% (frequency of detection), 1.01ug/L (highest detection)

Dachtal: 10% (frequency of detection), 39ug/L (highest detection)

Propyzamil: 57.14% (frequency of detection), 6.7ug/L (highest detection)

Chlorothalonil: 4.76% (frequency of detection), 6.07ug/L (highest detection)

Vinclozolin: 47.61% (frequency of detection), 0.3ug/L (highest detection)

Run Off Events

15-17/4/86

Chlorpyrifos 0.13ug/L

DDT and Metabolites: 0.37ug/L

Lindane: 0.05ug/L

Endosulfan 0.12ug/L

Dachtal 9.7ug/L

Propyzamide: 0,1ug/L

Run Off Events

5-7/12/86

Chlorpyrifos 5.2ug/L

DDT and Metabolites: 7.26ug/L

Lindane: 0.16ug/L

Endosulfan 17.4ug/L

Dachtal 88ug/L

Propyzamide: 36ug/L

Sediment

Dachtal 100-300ug/kg (3700ug/kg high)

DDT 300-1400ug/kg (Swingler Bridge 1838 ug/kg 18/3/87)