**6. Conclusions**

In order to summarize the findings presented in this chapter on the photoinitiated degradation of triazine and phenylurea herbicides we can conclude:


of light energy to enable purification of higher columns of solutions. With heterogenous photocatalysis the three-dimensionality has one more aspect: the photocatalytic reaction on a semiconductor is a surface process, thus the reactant must be captured by the photocatalyst surface.


Nevertheless, environmental pollution including water and soil pollution with herbicides is an increasingly grave problem, and with herbicides resistent to biodegradation and persisting for a long time in the environment the possibilities of photochemical degradation will not cease to attract attention. The possibilities for further development are open especially in the area of heterogeneous photocatalysis. An important key to success will be the utilisation of nano-sized photocatalyst powders dispersed on substrates with extremely large surface areas. Another approach is the modification of TiO2 to make it sensitive to visible light. So far the researchers investigating in this field are struggling with the issue of low reproducibility and chemical stability, nonetheless heterogeneous photocatalysis represents a promising prospect for 21 century.

#### **7. Acknowledgement**

I would like to thank my son David Klement for his help with formulas and schemes drawing.

### **8. References**

310 Herbicides – Properties, Synthesis and Control of Weeds

Fig. 9. Chloride ion release and hydroxyderivative formation in chlorotoluron

degradation of triazine and phenylurea herbicides we can conclude:

molecules under the thin surface layer.

conversion of the substrates.

In order to summarize the findings presented in this chapter on the photoinitiated




photodecomposition.

**6. Conclusions** 


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**17** 

*Argentina* 

**Oxidative Stress as a Possible Mechanism** 

*2Departamento de Química Analítica, Facultad de Ciencias Bioquímicas y Farmacéuticas,* 

Chlorophenoxy herbicides are widely used in agriculture and forestry, for the control of broad-leaved weeds in pastures, cereal crops, as well as along public rights of way. Structurally, these herbicides consist of a simple aliphatic carboxylic acid moiety attached to a chlorine-substituted aromatic ring via an ether linkage. One of the most commonly used herbicides of this type is 2,4-dichlorophenoxyacetic acid (2,4-D) (Fig. 1). In congruence with the similitude between its molecular structure and that of the plant hormone indole-acetic acid, 2,4-D acts as a plant growth regulator that can interfere with normal hormonal action

2.4-D was synthesized for the first time in 1941 and commercially marketed in the United States (U.S.) in 1944 (IARC, 1986) and worldwide since 1950 (Munro et al. 1992). The widespread use of 2,4-D as a domestic herbicide and as a component of Orange Agent

Human exposure to chlorophenoxy herbicides may occur through inhalation, skin contact or ingestion. The predominant route for occupational exposure to 2,4-D has been the

Several studies have shown that doses of 50, 70 or 100 mg/kg body weight (bw)/day of 2,4- D produce a wide range of toxic effects on the embryo and on the reproductive and neural

**1. Introduction** 

and plant growth (Munro et al., 1992).

encouraged the study of its toxicity.

Fig. 1. Structure of the 2,4-Dichlorophenoxyacetic Acid.

absorption of spills or aerosol droplets through the skin.

**of Toxicity of the Herbicide 2,4-**

*1Laboratorio de Toxicología Experimental, Departamento de* 

Bettina Bongiovanni1, Cintia Konjuh1, Arístides Pochettino1 and Alejandro Ferri2

*Ciencias de los Alimentos y Medio Ambiente;* 

*Universidad Nacional de Rosario, Rosario,* 

**Dichlorophenoxyacetic Acid (2,4-D)** 

