**6. References**

484 Pesticides in the Modern World - Risks and Benefits

triply coordinated groups, respectively). Although there is a lack of experimental evidence for the availability of surface sites on the coated mineral oxide to support these results, it appears that the SOM coating on the goethite particles produces a significant reduction in

As already mentioned, the interaction between PQ and bare goethite at acidic pH is almost negligible, whereas significant adsorption is observed on HA-coated goethite (Figure 2b), which is also consistent with the results reported by Brigante et al. (2010). Taking into account the favourable electrostatic interactions between SOM and cationic pesticides, the adsorption of PQ on HA-coated goethite appears to take place by direct binding to the HA molecules adsorbed onto goethite particles. Although the shape of the PQ adsorption isotherm on the HA-coated goethite is similar to that obtained for PQ binding on dissolved HA (Figure 2), the magnitude of the PQ adsorption, expressed in mol of adsorbed PQ per kg of organic matter adsorbed on mineral surface, is approximately 2.5 times lower. The HA-goethite association is produced by interactions between the negatively charged functional groups of HA and the positively charged goethite surface groups. The acid groups of HA are also involved in the PQ binding, and therefore a significant fraction of the ionized acid groups of the HA adsorbed on

The amount of PQ adsorbed by the HA covering the surface of the goethite was similar to the amount adsorbed by the same amount of organic matter in the peat soil. However, it is not known if changes in the distribution and/or conformation of the functional groups of the organic fraction occur during the process of formation of the goethite-HA aggregate, which would confer a more similar nature to that of the solid SOM represented by the peat

In order to analyse whether the behaviour of the HA adsorbed on the goethite is more similar to that of the dissolved HA or of that of the peat soil, the amount of PQ adsorbed on the covered goethite was estimated from the individual behaviour of each of the reference SOM. The binding parameters corresponding to the HA and the peat soil were used for this purpose, and only a different concentration of the carboxylic groups accessible to the PQ was assumed. The results obtained in this simulation (Figure 2b) show how the form of the experimental isotherm for PQ-HA coated goethite was better represented by the behaviour of the dissolved HA. It is therefore possible to explain the adsorption of PQ on the goethite-HA aggregate by only taking into account a reduction in the available reactive sites on the

However, as already indicated, rigorous interpretation of the interaction between PQ and the covered surface is more complex, and requires a more detailed knowledge of the properties of the surface, beyond the individual contributions of the component fractions. Given the electrostatic nature of the interaction between the ionic pesticides and binary goethite-HA systems, it is essential to know how the charge on the mineral surface is

An overall view of how PQ and MCPA interact with the HA and peat soil samples reveals the electrostatic nature of the interaction between ionic pesticides and SOM. The partial ionization of the acid groups in the SOM explains the high affinity of SOM for cationic species, such as PQ, and its low affinity for anionic compounds like MCPA. The difference in the amount of PQ bound to both types of SOM samples also appears to be directly related

the number of surface sites available to interact with MCPA.

goethite become occupied and/or inaccessible for binding PQ.

HA, relative to the same amount of HA in solution.

to their respective carboxylic group contents.

modified by the adsorption of negatively charged HA molecules.

soil.

**4. Conclusions** 


Interactions Between Ionic Pesticides and Model Systems for Soil Fractions 487

Iglesias, A.; López, R.; Gondar, D.; Antelo, J.; Fiol, S. & Arce, F. (2010a). Adsorption of

Iglesias, A.; López, R.; Gondar, D.; Antelo, J.; Fiol, S. & Arce, F. (2010b). Adsorption of

Inacio, J.; Taviot-Guého, C.; Forano, C. & Besse, J.P. (2001). Adsorption of MCPA pesticide by MgAl-layered double hydroxides. *Appl. Clay Sci.* 18, 255-264, ISSN 0169-1317 Jones, M.N. & Bryan, N.D. (1980). Colloidal properties of of humic substances. *Adv. Colloid.* 

Keizer, M.G. & van Riemsdijk, W.H. (1998). *ECOSAT, Equilibrium Calculation of Speciation and* 

Kinniburgh, D.G. (1993). *FIT User Guide*. BGS Technical Report WD/93/23. British

Kinniburgh, D.G.; van Riemsdijk, W.H.; Koopal, L.K.; Borkovec, M.; Benedetti, M.F. &

Merdy, P.; Koopal, L.K. & Huclier, S. (2006). Model metal-particle interactions with an

Milne, C.J.; Kinniburgh, D.G.; van Riemsdijk, W.H. & Tipping, E. (2003). Generic NICA-

Narine, D.J. & Guy, R.D. (1982). Binding of diquat and paraquat to humic acid in aquatic

Pacheco, M.L., Peña-Méndez, E.M. & Havel, J. (2003). Supramolecular interactions of húmic

Pateiro-Moure, M.; Bermúdez-Couso, A.; Fernández-Calviño, D.; Arias-Estévez, M.; Rial-

Rytwo, G.; Tropp, D. & Serban, C. (2002). Adsorption of diquat, paraquat and methyl green

Saito, T.; Koopal, L.K.; van Riemsdijk, W.H.; Nagasaki, S. & Tanaka, S. (2004). Adsorption of

Seki, Y. & Yudarkoç, K. (2005). Paraquat adsorption onto clays and organoclays from

Smith, E.J.; Rey-Castro, C.; Logworth, H.; Lofts, S.; Lawlor, A.J. & Tipping, E. (2004) Cation

Spadoto, C.S. & Hornsby, A.G. (2003). Soil sorption of acidic pesticides: modelling pH

aqueous solution*. J. Colloid Interface Sci.* 287, 1-5, ISSN 0021-9797

*A: Physicochem. Eng. Aspects* 151, 40-54. ISSN 0927-7757

environments. *Soil Sci.* 133, 356-363, ISSN 0038-075X

ISSN 0045-6535

ISSN 0304-3894

936X

*Interface Sci.* 78, 1-48, ISSN 0001-8686

*Technol.* 37, 958-971, ISSN 0013-936X

*Chemosphere* 51, 95-108, ISSN 0045-6535

*Langmuir* 20, 689-700, ISSN 0743-7463

*Eur. J. Soil Sci.* 55, 433-447, ISSN 1365-2389

effects. *J. Environ. Qual*. 32, 949-956, ISSN 0047-2425

2672, ISSN 0021-9568

282, ISSN 0169-1317

Geological Survey, Keyworth

MCPA on goethite and humic acid-coated goethite. *Chemosphere* 78, 1403-1408,

paraquat on goethite and humic acid-coated goethite. *J. Haz. Mat.* 183, 664-668,

*Transport.* Technical report of the Soil Quality Department. Wageningen University

Avena, M.J. (1999). Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency. *Colloids and Surfaces* 

emphasis on natural organic matter. *Environ. Sci. Technol*. 40, 7459-7466, ISSN 0013-

Donnan Model parameters for metal-ion binding by humic substances. *Environ. Sci.* 

acids with organic and inorganic xenobiotics studied by capillary electrophoresis.

Otero, R. & Simal-Gándara, J. (2010). Paraquat and Diquat sorption on iron oxide coated quartz particles and the effect of phosphated. *J. Chem. Eng. Data* 55, 2668-

on sepiolite: experimental results and model calculations. *Appl. Clay Sci.* 20, 273-

humic acid on goethite: isotherms, charge adjustment, and potential profiles.

binding by acid-washed peat, interpreted with Humic Ion-Binding Model VI-FD.


Clausen, L. & Fabricius, I. (2001). Atrazine, isoproturon, mecoprop, 2,4-D, and bentazone adsorption onto iron oxides. *J. Environ. Qual*. 30, 858-869, ISSN 0047-2425 Companys, E.; Garcés, J.L.; Salvador, J.; Galceran, J.; Puy, J. & Mas, F. (2007). Electrostatic

Cornell, R.M. & Schwertmann, U. (1996). *The Iron Oxides: Structure Properties, Reactions,* 

Davis, J.A.; Coston, J.A.; Kent, D.B. & Fuller, C.C. (1998). Application of the surface

Draoui, K.; Denoyel, R.; Chgoura, M. & Rouquerol, J. (1999). Adsorption of paraquat on

Filius, J.D.; Hiemstra, T. & van Riemsdijk, W.H. (1997). Adsorption of small weak organic

Filius, J.D.; Meeussen, J.C.L.; Hiemstra, T. & van Riemsdijk, W.H. (2001). Modeling the

Giles, C.H.; MacEwan, T.H.; Nakhwa, S.N. & Smith, D. (1960). Studies in adsorption. Part XI.

Grant, P.G.; Lemke, S.L.; Dwyer, M.R. & Phillips, T.D. (1998). Modified Langmuir equation

Gustafsson, J.P. & Kleja, D.B. (2005). Modeling salt-dependent proton binding by organic

Gustafsson, J.P. (2010). *Visual MINTEQ version 2.53*, http://www2.lwr.kth.se/English/

Hayes, K.F.; Papelis, C. & Leckie, J.O. (1988). Modeling ionic strength effects on anion

Hesketh, N.; Jones, M.N. & Tipping, E. (1996). The interaction of some pesticides and herbicides with humic substances. *Anal. Chim. Acta* 327, 191-201, ISSN 0003-2670 Hiemstra, T. & van Riemsdijk, W.H. (1996). A surface structural approach to ion adsorption:

Hiemstra, T. & van Riemsdijk, W.H. (2006). On the relationship between charge distribution,

Iglesias, A.; López, R.; Gondar, D.; Antelo, J.; Fiol, S. & Arce, F. (2009). Effect of pH and

model. *J. Colloid Interface Sci.* 244, 31-42, ISSN 0021-9797

ISSN 0927-7757

ISSN 0021-9797

*Chem. Soc*. 3, 3973-3993

39, 5372-5377, ISSN 0013-936X

*Interface Sci.* 301, 1-18, ISSN 0021-9797

acids. *Chemosphere* 76, 107-113, ISSN 0045-6535

Oursoftware/vminteq/

ISSN 0021-9797

9797

2820-2828, ISSN 0013-936X

Germany

6150

and specific binding to macromolecular ligands. A general analytical expression for the Donnan volume. *Colloids and Surfaces A: Physicochem. Eng. Aspects* 306, 2-13.

*Occurrence, and Uses* (1st edition), VCH Publishers, ISBN 3-527-28576-8, Wienheim,

complexation concept to complex mineral assemblages. *Environ. Sci. Technol*. 32,

minerals. A thermodynamic study. *J. Therm. Anal. Calorim.* 58, 597-606, ISSN 1388-

acids on goethite: modeling of mechanisms. *J. Colloid Interface Sci*. 195, 368–380,

binding of benzenecarboxylates by goethite: the ligand and charge distribution

A system of classification of solution adsorption isotherms, and its use in diagnosis of adsorption mechanisms and measurement of specific surface areas of solids. *J.* 

for S-shaped and multisite isotherm plots. *Langmuir* 14, 4292-4299, ISSN 0743-7463.

soils with the NICA-Donnan and Stockholm Humic models. *Environ. Sci. Technol.* 

adsorption at hydrous oxide/solution interface. *J. Colloid Interface Sci*. 125, 717-726,

The charge distribution (CD) model. *J. Colloid Interface Sci.* 179, 488-508, ISSN 0021-

surface hydration, and the structure of the interface of metal hydroxides. *J. Colloid* 

ionic strength on the binding of paraquat and MCPA by soil fulvic and humic


**27** 

*Croatia* 

**Behavior and Fate of Imidacloprid in** 

**Croatian Olive Orchard Soils Under** 

Dalibor Broznić, Jelena Marinić and Čedomila Milin

*Department of Chemistry and Biochemistry, School of Medicine, University of Rijeka,* 

Over the last two decades, the worldwide production and use of pesticides have greatly increased, causing great concern about their fate in the soil environment, as well as their adverse effects on nontarget organisms, including human beings. An important thing to realize it that only a small part of the pesticide doses used reaches its intended target (< 0.1%), while the major part (over 99%) of it is distributed into the ecosystem (Pimentel & Levitan, 1986), where it can cause difficulties through its toxicity to nontarget species, and cause serious environmental problems, such as groundwater contamination, food contamination, and air pollution (Larson et al., 1997; Mathys, 1994). There is also increasing interest in their transformation products, because they can be present at higher levels in the soil than the parent itself. In some instances, transformation products are more toxic, so they represent a greater risk to the environment than the parent molecule. Therefore, it is essential to study the residue and degradation pattern of pesticide in crop, soils and water systematically in order to generate meaningful data from the point of view of plant

In the past few decades, three major groups of insecticides have dominated the market: organophosphates, carbamates and pyrethroids. Nevertheless, pests resistance limited their use and caused a need for the synthesis of a new group that will be effective and nontoxic to the environment and to mammals. The results was "the birth" of neonicotinoids which exhibited high insecticidity and low toxicity to the environment (Maienfisch et al., 2001). But because neonicotinoids are becoming extensively used, both in agriculture and for home use, the chance of their polluting water is still present despite the low application rates. Imidacloprid [1-(6-chloro-3pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine; IMI] was the first neonicotinoid registered by the United States Environmental Protection Agency (USEPA) for use as a pesticide through its actions as an agonist on the nicotinic acetylcholine receptor (nAChR) (Bai et al., 1991). The mode of action of IMI in the brain is shown in Figure 1. The toxicity of IMI is largely due to interference of the neurotransmission in the nicotinic cholinergic nervous system. Prolonged activation of the nAChR by IMI causes desensitization and blocking of the receptor, and leads to incoordination, tremors, decreased activity, reduced body temperature and death. IMI's favorable selective toxicity to insects versus mammals makes it safer for insect control than other neurotoxins (Tomizawa & Casida, 2003) and enables its diverse use in soil and foliar treatment in different crops, as

**1. Introduction** 

protection, public health and environmental safety.

 **Laboratory Conditions** 

