**6. Acknowledgements**

This work has been carried out in collaboration with "Navarra de Infraestructuras Locales S.A. (NILSA)", in the research project "Regeneración de aguas depuradas mediante procesos de oxidación avanzada (CTM2008-01876/TECNO)" financed by "Secretaría de Estado de Universidad e Investigación del Ministerio de Ciencia e Innovación", "Diputación General de Aragón" and "Fundación Caixa Catalunya".

#### **7. References**





This work has been carried out in collaboration with "Navarra de Infraestructuras Locales S.A. (NILSA)", in the research project "Regeneración de aguas depuradas mediante procesos de oxidación avanzada (CTM2008-01876/TECNO)" financed by "Secretaría de Estado de Universidad e Investigación del Ministerio de Ciencia e Innovación", "Diputación General

Directive 80/68/EEC of the Council of 17 December of 1979, on groundwater protection

Directive 91/271/EEC of the Council of 21 May of 1991, concerning urban waste-water treatment. Diary Official of European Communities L 135, of 30 May of 1991. Directive 2000/60/EC of the European Parliament and Council, of 23 October of 2000, by

Directive 2006/118/EC of the European Parliament and Council of 23 October of 2006

Official of European Communities L 372, 27 December of 2006.

against pollution caused by dangerous substances. Diary Official of European

which a communitarian framework of actuation in the field of the water politics is established. Official Diary of European Communities L 327, 22 December of 2000. Directive 2006/11/EC of the European Parliament and Council of 15 February of 2006,

related to pollution caused by dangerous substances tipped in the aquatic environment of the Community. Official Diary of European Communities L 64, 4

relating to groundwater protection against pollution and deterioration. Diary

Regarding to the characteristic of the studied WWTPs effluents:

L-1.

4 and 56 mg L-1.

**6. Acknowledgements** 

March of 2006.

**7. References** 

With regard to the reuse of WWTPs effluents:

these pesticides exceed the established EQSs.

de Aragón" and "Fundación Caixa Catalunya".

Communities 020/L, of 26 January of 1980.


**26** 

 *Spain* 

*2Eurofins Analtico BV,* 

*University of Santiago de Compostela,* 

**Interactions Between Ionic Pesticides and** 

*1Department of Physical Chemistry, University of Santiago de Compostela,* 

The extensive use of herbicides in agriculture and their potentially toxic effects have promoted studies investigating the physical, chemical and biological processes that determine the mobility, bioavailability and degradation of these compounds in soils (Blasioli et al., 2011). Knowledge of these processes will enable prediction of the transport and fate of herbicides in soils and aquatic systems, and thus enable measures to be taken to limit their

Retention is considered the main cause of the deactivation of herbicides in soils, and is important from the point of view of inhibiting the toxic properties of herbicides and of restricting their transport into aquatic systems (Jones & Bryan, 1980). Although not unique, adsorption reactions (i.e. accumulation of chemical species at the solid-solution interface) are the main cause of the retention of organic contaminants in soils, and their extent will depend on the physicochemical properties of both the adsorbent (soil) and the adsorbate (herbicide). The chemical characteristics of organic compounds are largely responsible for their behaviour in soil, and the differences in adsorption of different herbicides in the same soil are attributed to their distinct chemical properties. Although herbicides are very diverse, two groups can be distinguished in order to interpret their interactions with soil components: those involving chemical forces and those involving physical forces. The first group comprises ionic or ionizable hydrophilic compounds, while the second group

Bipyridinium cations, such as paraquat (1,1'–dimethyl–4,4'–bipyridinium ion), are the best known members of the ionizable herbicides as they have been extensively used in agriculture and are consequently widely distributed in soils and waters. Paraquat (PQ) is applied as a dichloride or dibromide salt, which when dissolved in water releases the organic cation PQ2+, which can be adsorbed on the soil surface, either by replacing inorganic cations or by an ionic interaction mechanism with negatively charged sites on the soil surface, in which the electrostatic effect will be determinant (Narine & Guy, 1982). PQ adsorbs on humic substances and the degree of adsorption increases as the pH increases, as

**1. Introduction** 

environmental impact.

comprises non polar hydrophobic compounds.

**Model Systems for Soil Fractions** 

Florencio Arce1, Ana C. Iglesias2, Rocío López1, Dora Gondar1, Juan Antelo3 and Sarah Fiol1

*3Department of Soil Science and Agricultural Chemistry,* 

Santos J.L., Aparicio M., Callejón M., Alonso E. Occurrence of pharmaceutically active compounds during 1-year period in wastewaters from tour wastewater treatment plants in Seville (Spain). Journal of Hazardous Materials 164, 1509-1516 (2009).
