Pesticides by soil

Gerstl Z, Helling CS. 1987. Evaluation of molecular connectivity as a predictive method for the adsorption of pesticides by soils. J Environ Sci Health B22 55-69. 

Bailey GW, White JL (1964) Review of adsorption and desorption of organic pesticides by soil colloids with implications concerning pesticide bioaviailability. Agri Food Chem 12 324-382... 

Arienzo M, Sanchez-Camazano M, Crisanto HT, et al. 1993. Effect of organic cosolvents on adsorption of organophosphorus pesticides by soils. Chemosphere 27(8) 1409-1417. 

The sorption and desorption of pesticides by soils and soil constituents such as clay minerals and humic substances has generally been characterized by an initial rapid rate folllowed by a much slower approach to an apparent equilibrium (Haque et al., 1968 Leenheer and Ahlrichs, 1971 Khan, 1973 McCall and Agin, 1985). The initial reaction(s) have been associated with diffusion of the pesticides to and from the surface of the sorbent, while the slower reaction(s) have been related to PD of the pesticides into and out of micropores of the sorbent. 

Soil type is one of the most important factors influencing the adsorption of pesticides by soils. Of special importance are the clay and organic matter. 

Adams, R.S., Factors influencing soil adsorption and bioactivity of pesticides, Res. Rev.f 47,1,1973. Bailey, G.W. and White, J.L., Review of adsorption and desorption of organic pesticides by soil colloids, with implications concerning pesticide bioactivity, /. Agric. Food Chem., 12, 324,1964. 

Gerstl, Z. and Helling, C.S. (1987). Evaluation of Molecular Connectivity as a Predictive Method for the Adsorption of Pesticides by Soils. J.Environ.Sci.Health, B22,55-69. 

Kaufman, D. D. 1974. Degradation of pesticides by soil microoiganisms. In Guenzi (ed.). Pesticides in Soil and Water, pp. 133-202. 

Bailey, G. W., White, J. L., Soil-pesticide Relationships Review of Adsorption and Desorption of Organic Pesticides by Soil Colloids, with Implications Concerning Pesticide Bioactivity, /. Agr. Food Chem, (1964) 12, 324-332. 

Several mathematical models have been proposed for representing the overall adsorption of pesticides by soils. The most comprehensive one appears to be that of Lambert et al. (9), in which the partition of pesticides between soil water and soil is represented by a linear adsorption equation similar to the Langmuir equation. In this model they have assumed that the active adsorbent for pesticides in soils is the soil organic matter. This approach has been successful in modeling the adsorption of nonionic pesticides on soils (12), Lambert (13) has introduced an index of soil adsorption of pesticides which is intended to indicate the amount of active organic matter in a soil and therefore may be used to compare the adsorption capacity of one soil with that of another. Lambert states that the index is independent of the pesticide being adsorbed. 

Another example of the usefulness of microcalorimetry to study the solid-liquid interface has been reported by Draoui et al. [118]. They analyzed the adsorption of Paraquat on different minerals, which are part of the soil, to study the retention process of this pesticide by soils. In the particular case of silica they concluded that the main driving force for adsorption is electrostatic. They found a linear decrease of the adsorption enthalpy in the range of -25 to -20 kJ/mol. Nevertheless, the Paraquat molecule has two charges the heat evolved during adsorption is of the same order as in the case of other single-charged molecules. This fact is explained assuming that the... 

Arienzo, M., M. Sanchez-Camazano, T. Cristano Herrero, and M.J. Sanchez-Mardn. Effect of Organic Cosolvents on Adsorption of Organophosphoms Pesticides by Soils, Awvrron. Sci. Technol, 27(8) 1409-1417 (1993). 

Hydrodechlorination is a common reaction of chlorinated pesticides such as atrazine (eq. 15), alachlor, and metolachlor (2) (eq. 16). These reactions are catalyzed primarily by transition metals or by soil surfaces (clays or humic substances). 

The pesticide component of SWRRB takes into account the fate of the chemical applied under field conditions For example, the amount of pesticide actually reaching the ground after application over a plant canopy is calculated. Further, field dissipation of the chemical by photolysis on leaf surfaces as well as degradation in the soil is accounted for with the pesticide component of SWRRB. Leaching of the pesticide below the top 1cm of soil is also computed and runoff corrected for such losses. Further, adsorption of the pesticide to soil surfaces and sediment is taken into account by SWRRB. 

Helling CS, Turner BC. Pesticide mobility determination by soil thin-layer chromatography. Science 1968 162 562-563. 

Qin BH, Yu BB, Zhang Y, Lin XC. Residual analysis of organochlorine pesticides in soil by gas chromatograph-electron capture detector (gc-ecd) and gas chromatograph-negative chemical ionization mass spectrometry (GC-NCI-MS). Environ. Forensics 2009 10 331-335. 

Moder M, Popp P, Eisert R, Pawliszyn J. Determination of polar pesticides in soil by solid phase microextraction coupled to high-performance liquid chromatography-electrospray/mass spectrometry. Fresenius. J. Anal. Chem. 1999 363 680-685. 

The problems relating to increased contamination levels and/or insufficient sensitivity may be overcome by using matrix-solid phase dispersion, MS detection in selected ion monitoring (SIM) mode, and/or large volume injection. An example of combined analysis that utilizes specific detection is shown in Fig. 2.6. It entails simultaneous analyses of PAHs, PCBs, chlorobenzene, and organochlorine pesticides in soil. 

It can be assumed that the rate of removal of these pesticides from soil by rain elution follows the usual exponential law, namely ... 

Kuhn EP, Suflita JM. 1989. Dehalogenation of pesticides by anaerobic microorganisms in soils and groundwater-a review. In Reactions and movement of organic chemicals in soils. Soil Science Society of America Special Publication 22 111 -180. 

L. Sun and H.K. Lee, Optimization of microwave-assisted extraction and supercritical fluid extraction of carbamate pesticides in soil by experimental design methodology. J. ChromatogrA 1014 (2003) 165-177. 

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