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A new system minimizes pesticide pollution of aquifers
06 March 2009
CSIC - Consejo Superior de Investigaciones Cientificas
One of the effects of the application of pesticides and herbicides in agriculture is the pollution of aquifers, because the pesticide is carried by irrigation water or rain along the soil profile (leaching). Minimizing such contamination is possible adjusting the maximum dose of herbicide. Nevertheless, it is difficult to totally avoid it because sooner or later the chemical will be dragged by the water.
Another problem is that when applying pesticides by spray part of their molecules are
volatilized. Failure to comply with strict security measures implies risk for people who repeatedly apply the compounds as they are exposed to the neurotoxic effects of some of these substances.
Scientists in the Institute of Natural Resources and Agrobiology of the Spanish National Research Council (CSIC) have developed a method to encapsulate and slowly release pesticides so that prevents the leaching as well as the volatilization of their molecules.
Tomas Undabeytia, principal investigator of this project, explains that the new method encapsulates the pesticide in lecithin liposomes or vesicles, which in turn are fixed on the surface (adsorption) of clay. The final product is a complex that combines liposomes, pesticide and clay and, at a first glance, looks like clay powder. This complex, which is dispersed in water, allows the chemical compound to be slowly released, as it is fixed to the clay. This also prevents the compound to be washed away by irrigation water or rainfall to subsurface layers and aquifers.
Although the formulation has been designed for agricultural products, it could be applied to other areas, such as mosquito lotions. The components of this formulation, the lipid to form liposome and the clay mineral, are classified by the Environmental Protection Agency of USA (USEPA) as substances of minimal toxicological concern.
Fewer doses, more time, less cost
The new development allows a safer pesticide formulation, thus avoiding repetitive applications or the need for higher doses and reducing the risk of contamination of water and soil while maintaining the desired effect of the pesticide on the target.
One of the major advantages of this system, as the authors explains, is that this formulation can be applied to molecules of pesticides of any kind, either hydrophobic, or acidic or basic. This greatly reduces complications. Experts know that when talking about pesticides, the interaction between chemicals and different soil types must be taken into account. For example, in Mediterranean agricultural areas predominates the calcareous soils. These kind of soils do not retain the anionic herbicide, which means that once there is an excess of water, then all the pesticide is leached to lower layers of soil. On the other hand, there are some new herbicides developed to minimize the required dose and reduce these pollution problems. But they are precisely anionic herbicides, which leach easily into calcareous soils. So, depending on the physico-chemical properties of the soil, the potential benefits of these last generation of herbicides can be lost. This is just one example that demonstrates why it is so important to obtain a slow release system, as these researchers have developed, able to be applied to any molecule of pesticide.
Safety problems with pesticides are not trivial. The EU has recently adopted new rules to restrict the use of chemical compounds that pose a risk to health and the environment. The new regulations forbid, among other things, production of pesticides that may be carcinogens or affect human health. Some of the compounds that are used at the farm level are very neurotoxic and, although they degrade after a few days, humans and wildlife exposed while the molecules are still active can be affected.
Suppression at once of the current substances is not possible, so the EU strategy aims at reducing or replacing existing products by less harmful formulations.