Assessing the Need for Groundwater Quality Guidelines for Pesticides Using the Species Sensitivity Distribution Approach

ABSTRACT

The water quality needs of groundwater ecosystems are rarely considered. It is currently assumed that water quality guidelines for surface waters will also protect groundwater ecosystems and their fauna, but this assumption has not been tested. The aim of this study is to determine whether water quality guidelines specifically for groundwater ecosystems are needed and to provide a preliminary risk assessment for groundwater ecosystems in Australia. In the absence of sufficient toxicity data for true groundwater fauna, 48–96 h LC50 data for groundwater-dwelling invertebrate orders (e.g., Crustacea, Rotifera) are used as a surrogate and were compared, using Species Sensitivity Distribution (SSD) curves, to a full suite of surface taxa (including fish, insects, and algae). SSD curves were derived for a range of pesticides previously detected in Australian groundwaters and were fitted using the Burr Type III distribution. Significant differences in the sensitivities of surface and groundwater taxa to Atrazine and Chlorpyrifos were detected, indicating surface water quality guidelines are not always suitable to protect or best manage groundwater ecosystems. Water quality guideline values derived from the SSDs highlighted a significant threat of contamination to groundwater ecosystems from agricultural chemicals. Clearly water quality guidelines specifically for groundwater ecosystems are needed.

Key words:

• species sensitivity distribution
• groundwater contamination
• pesticides
• protective concentration
• hazardous concentration.

ACKNOWLEDGEMENTS

Thanks go to Paul Van den Brink (Alterra) and Stephen Blockwell (SKM) for comments on the manuscript. Thanks also go to Phil Gorey (SA EPA) and Karina Budd (Bureau of Rural Sciences) for assistance with collation of groundwater contamination data. This article was improved by the insightful comments of three anonymous reviewers. This work was supported by a UTS early career research grant.

Notes

^a Hargreaves and Osborne unpub. data cited in Keating et al. (1996)

^b Budd et al. (2002)

^c Timms and Cooper (1998)

^d Gerritse et al. (1990)

^e Wenig and Lawrence (1998)

^f Appleyard et al. (1997)

^g Brodie et al. (1984)

^h Schmidt et al. (1996).