Magazine article Ecos

Water Quality at Risk, Scientist Warn

Magazine article Ecos

Water Quality at Risk, Scientist Warn

Article excerpt

Since the early 1980s, Australia has experienced an almost exponential growth in the use of insecticides, herbicides, fungicides and defoliants for crop protection. Much of this chemical use is concentrated in the Murray-Darling Basin, where the growing needs of intensive agriculture are further served with reservoirs, weirs and river diversions.

Increased research into the effects of these practices is vital to the safety and security of Australia's inland water supplies, and consequently to agricultural sustainability in the region, according to a report presented in September 1996 to the Prime Minister's Science and Engineering Council.

The report, Agricultural Chemicals and Algal Toxins -- Emerging Water Quality Issues, was prepared by Bruce Cooper from the NSW Department of Land and Water Conservation, Dr Gary Jones and Dr Richard Davis from CSIRO's Division of Water Resources, and Dr Michael Burch from the CRC for Water Quality and Treatment in Adelaide. It warns that Australia's surface and groundwater resources increasingly are at risk from agricultural chemical residues and toxins produced by blue-green algae, and that many of the processes leading to this contamination are poorly understood.

Research is needed on the core problems of how agricultural chemicals and algal toxins persist in the environment, to what extent they can be passed through the food chain, and how they affect human health, the report says. Cost-effective technologies to help manage the emerging problems, and improved guidelines and best-management practices aimed at preventing contamination also are needed.

The report warns that while the effects of individual pesticides are generally well known, the `synergistic' combinations may alter or multiply the effects of the original chemicals many times. For example, the pesticides dieldrin and endosulfan are individually weak environmental oestrogens, but in combination can be up to 1000 times more potent. Combinations of other commonly used chemicals may have similar synergistic effects, but the mechanics leading to these synergies, and which combinations are most potent, are not understood.

Another subject requiring investigation is the impact on in-stream ecology of the accumulation of pesticides in sediments, the report says. Adsorption to suspended particulates followed by deposition to river sediments is a process that concentrates some pesticides in the environment. The effects of this process on the biota living in the sediments are little known, except where gross incidents of contamination have occurred. While sedimentation can concentrate some pesticides, the actual binding of pesticides to sediments may reduce their bioavailability in the short term. …

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