Herbicide runoff reduced to Great Barrier Reef

By October 16th, 2013

An innovative new approach to sugarcane plantation weed management trialled in select Great Barrier Reef (GBR) catchments has shown a 90 per cent reduction in runoff of highly soluble herbicides into waterways.

In the lower Burdekin region of northern Australia, scientists from CSIRO’s Water for a Healthy Country Flagship trialled a new technique for applying herbicides to raised beds of furrow irrigated sugar cane by using a specially adapted shielded sprayer. The technique minimises the likelihood of herbicides such as diuron, atrazine, ametryn and hexazinone coming into contact with irrigation water.

Many of the herbicides used in the region are PSII herbicides that are known to negatively impact reef ecosystems. These waters discharge into the internationally recognised Great Barrier Reef World Heritage Area and subsequently into the Great Barrier Reef Marine Park. Improved farming techniques such as the shielded sprayer help keep herbicides on-farm have potential to have a significant and positive impact on water quality in the GBR.

“The conventional application of herbicides in furrow-irrigated sugarcane production is to broadcast spray across the whole field using boom sprayers, which applies herbicides to both beds and furrows. Irrigation water then carries the herbicides with the tail water into the drainage channels, into nearby creeks and rivers and potentially into the GBR lagoon,” CSIRO research leader, Dr Rai Kookana said.

Improved farming techniques such as the shielded sprayer help keep herbicides on-farm have potential to have a significant and positive impact on water quality in the Great Barrier Reef.

“Given the importance of improving GBR water quality additional testing and demonstration of these technologies across different soil types, farming systems – and possibly with different combinations of chemicals – would provide valuable additional testing of the approach from an industry perspective.”

“These trial results are extremely encouraging, and clearly demonstrate that the use of precision herbicide application technologies by the industry, including using shielded sprayers for furrow-irrigated sugarcane cultivation, can be highly effective in reducing herbicide run-off.”

CSIRO scientist Danni Oliver said the geography of the region meant  that almost the entire flow from the Burdekin River Irrigation Area in the dry season (from July to January) was made up exclusively of irrigation water from sugarcane and other cropping.

“The trials show that while there will certainly be some herbicide loss following the first irrigation or rainfall event, the marked decreases in losses documented in this study – a reduction of to 90 per cent – could lead to significant improvements in off-site water quality, particularly during the dry season,” Ms Oliver said.

According to Jon Brodie of James Cook University the amount of some herbicides in creek and estuarine waters during this period regularly exceeds Australian water quality guidelines and could potentially affect, for example, coastal seagrass.

The results of the study have been published in the international journal Science of the Total Environment.

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Dr Rai Kookana discusses micropollutants
Dr Rai Kookana discusses why micropollutants including endocrine disrupting chemicals are an emerging threat to our water ways and native fish. (6:37)


Interviewer: We’re talking to Dr Rai Kookana, who is an environmental chemist and Principal Research Scientist at CSIRO Land and Water.

The subject of today’s podcast is micropollutants, chemicals such as endocrine disrupting chemicals, pharmaceuticals and personal care products in the Australian environment. So Dr Kookana, could you tell us what you mean by the term micro pollutants?

Dr Kookana: Yes. Micropollutants is a term which is commonly used for contaminants that tend to occur in the environment at very, very low concentrations. Here we are talking about micrograms per litre or even nanograms per litre, so parts per billion, parts per trillion level.

But the interesting thing is that even at these low concentrations they have the potential to have impact on health and wellbeing of the exposed organisms. So it’s a term which is used to cover a very broad range of chemicals.

Interviewer: And what are some of the main groups of micropollutants?

Dr Kookana: In broader terms we are talking about endocrine disrupting chemicals, pharmaceuticals, and constituents or personal care products.

Interviewer: So the story of micro pollutants, I guess, really began with DDT and organochlorin pesticides, but what are some of the agents that are causing concern today?

Dr Kookana: I think in the last ten or 15 years it has been more the identification of very potent pharmaceutical compounds such as synthetic hormone used in the contraceptive pill called ethinyl estradiol, and I think now there is development of water quality guidelines on those, and there is probably some response in Europe coming to what to do with this compound ethinyl estradiol.

In the same sort of period there is another group of compounds called anti-microbial agents used in soaps and shampoos and some of the other detergents and other products, such as triclosan and triclocarban. We in Australia have done a lot of work and found these in the environment, and there is some policy response expected in near… well in a few years to come probably, in Australia, and globally.

Interviewer: And what do we know about the effects that micropollutants have in the environment?

Dr Kookana: I think broadly speaking there are several effects that have emerged from some of these compounds mimicking hormones, or eliciting a response of the receptors for the hormones.

These effects could then lead to reproductive type or behavioural type effect, and sometimes altered sex of the organisms. And one of the earliest examples of the micropollutants in wastewater, and effluent coming from urban sewerage systems were in the U.K., where fish sex ratios were affected fairly broadly in the wild fish. This was the work by Dr Susan Jobling at the Brunel University.

So you basically have male fish with a protein which only should occur in the female, the egg yolk protein called vitellogenin. So that usually is an indication of exposure to these estrogenic compounds which are feminising, and hence a male fish could have a protein which should only occur in females. Sometimes the male fish could have female organs, like what is called inter-sex.

So there are a whole range of effects, and these are kind of very obvious effects. But then there are subtle effects in terms of behaviour where they are not able to participate in reproductive activities, copulation, or even protect their nests and those sorts of things. So there’s also a very subtle range of effects.

But then there are some compounds which could be sort of eliciting the conventional toxicity if the concentrations are high enough. Because, for example, pharmaceuticals are by design biologically active compounds.

Interviewer: So where are we at in terms of dealing with micropollutants in Australia?

Dr Kookana: Locally I guess we are still trying to establish the true extent of exposure and effect in the Australian environment.

Interviewer: Now you’ve recently held a large symposium looking at the issue of micro pollutants in Australia, which was titled “What’s in our water?” Could you tell us about some of the science and the issues that were discussed at that?

Dr Kookana: During this symposium there’s a whole range of aspects which were covered. For example, because we are dealing with very low concentrations, the latest development on the analytical methods and techniques was shared, how we actually monitor our environment.

There were reports on detection and monitoring of micro pollutants in fresh water, estuarine and marine environments from Australia and New Zealand.

There was some science shared in relation to the breakdown of some of these compounds in to transformation products, how do we establish them, how do we identify them? And more importantly, the effect on the organisms, the toxicity to aquatic or terrestrial ecosystems, or in water or in sediments for the organisms in water in water and sediments, and in particular, how do we deal with the mixtures?

That’s been a challenge. And these are like tiny, tiny amounts of several chemicals occurring together – while one might not elicit any response, but you put them together and then, because they have a similar mode of action, they could have an effect.

So how do we deal with the mixtures?

Interviewer: We were speaking to Dr Rai Kookana. To find out more about CSIRO’s research in to micropollutants visit www.csiro.au/whatsinourwater

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