**5. Acknowledgment**

530 Pesticides in the Modern World - Risks and Benefits

and locking action, if the activated pesticides do not leave the reaction system, they may soon be locked and bound with SOM, and resulted in the pesticide level in the system to reduce. Locking and unlocking mechanism to pesticides is the dominant mechanism for oxalic acid with smaller molecule, and the action mechanism of tartaric acid and citric acid with larger molecules to pesticides dominated by the chelation is the same as to macromolecules DOM (Yang *et al.*, 2001) and unlocking mechanism, it can avoid free pesticides being locked again, Therefore, the release amount of pesticides by tartaric acid

O

O

OH OH OH OH OH OH OH OH OH

土壤胶体矿物

The results showed that the introduction of LMWOA could accelerate the release of the tested organochlorine pesticides (relative to the water, increased 15%~18% for DDTs, 7%~25% for HCHs). It implied that the LMWOA induced the complication of the kinetics release mechanisms of organochlorine pesticides (The best kinetics equation describing the release of pesticide changed from the first-order kinetic equation in water system to parabola diffuse equation, double constant equation or Elovich equation in LMWOA systems). It also indicated that the kinetics release mechanisms of OCPs by LMWOA involved not only the simple granular surface diffusion mechanism in water system, but also the outward diffusion mechanism of soil particles internal, activation and inactivation function of granular surface, the non-uniform mechanism of surface energy distribution induced by the solution of soil mineral and structure change of soil inherent organic matter

Fig. 4. Sketch about the interaction among pesticides, LMWOA, humic acids and soil

soil colloids and minerals

OH

O COOH

O O

O

COOH

O

腐殖酸

COOH

OH

Cl

Cl Cl

有机氯农药

organochlorine pesticides

OH

Cl

OH

SH

Cl

Cl

OH

humic acid

OH

OH O

O

OH COOH

COOH OH OH

and citric acid is much higher than that by oxalic acid and water.

OH

NH2

HOOC

O

OH

OH

O OH

O

酒石酸

tartaric acid

OH

OH O

柠檬酸

citric acid

O

草酸

oxalic acid

O

HO

O

HO

HO

mineral.

**4. Conclusion** 

OH

OH

coating onto the soil mineral surface by LMWOA.

OH

OH OH

The authors would like to acknowledge National Science and Technology major program (2009ZX 07317-007), National Natural Science Foundation of China (50839002), Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes foundation, Hohai University (2007KJ003) and the Fundamental Research Funds for the Central Universities (2009B17014).
