**5. Triazine degradation and uptake in the soil**

The sorption behaviour of triazines in soil directly influences their bioavailability to soil microorganisms and plants (Mudhoo & Garg, 2011), leading to their uptake and biodegradation. Numerous studies are available for atrazine as the most widely applied and apparently also persistent triazine in the soil (Jablonowski et al., 2011). Plant uptake of triazines from the contaminated soils is extensively studied as a means for bioremediation. The C4-metabolism plants show the greatest resistance to triazines and detoxify them by hydrolysis. Examples of plants shown to be useful in degrading atrazine in their rhizosphere are *Polygonum lapathifolium*, *Panicum dichotomiflorum* (Mudhoo & Garg, 2011), *Pennisetum clandestinum* (Popov & Cornish, 2006; Singh et al., 2004).

Ongoing research in the soil microorganisms capable of utilizing triazines as their energy source has resulted in an extensive array of isolated strains: *Acinetobacter* sp., *Cytophaga* sp., *Pseudomonas* sp., *Ralstonia* sp., *Agrobacterium* sp. (Mudhoo & Garg, 2011), *Klebsiella* sp. and *Comamonas* sp. (Yang et al., 2010), *Nocardioides* sp. and *Arthrobacter* sp. (Vibber et al., 2007). Most of them are capable of extensive mineralization of triazines (Mudhoo & Garg, 2011; Yang et al., 2010) and have a limited access even to aged herbicide residues in the soil (Jablonowski et al., 2008; Mudhoo & Garg, 2011). The species most often used for triazine degradation is *Pseudomonas* sp., its efficacy has been shown to be influenced by citrate addition (Jablonowski et al., 2008), soil humidity (Ngigi et al., 2011) and microorganism adsorption on simulated soil particle aggregates (Alekseeva et al., 2011). Green algae and diatoms (Mudhoo & Garg, 2011), as well as cyanobacteria (Gonzalez-Barreiro et al., 2006) are also capable of atrazine uptake and are thus a valuable option for the bioremediation of the contaminated waters. Certain fungal species able to grow on atrazine-contaminated soils and capable of its uptake have been identified as well (Mudhoo & Garg, 2011).

Compared to biotic degradation by microorganisms and higher plants, abiotic degradation of triazines in soils is a minor dissipation route. Humic substances at low pH catalyse the hydrolysis of atrazine and its chlorinated transformation products to their hydroxy analogues (Prosen & Zupančič-Kralj, 2005). Photolysis of atrazine under solar irradiation and in the presence of humic substances was found to be negligible (Prosen & Zupančič-Kralj, 2005); however, simazine and terbutylazine were found to dissipate faster under solar irradiation of the soil (Navarro et al., 2009). Photolytic transformation and eventual mineralization is enhanced by using a suitable photocatalytic agent, e.g. TiO2, which holds a potential for clean-up of contaminated sites (Konstantinou & Albanis, 2003).

#### **6. Analytical approaches and cautions for triazine determination in soil**

Triazine determination data for soil and other solid environmental samples are used to estimate the extent of the site pollution and potential toxicity (Jablonowski et al., 2011). However, determination of triazines and their TPs in solid samples is prone to many problems, as schematically depicted in Fig. 3.

Knowledge of sorption/desorption behaviour of triazines is frequently applied in bioremediation either to enhance their leaching or to stabilise the residues in the contaminated sites (Delgado-Moreno et al., 2010; Jones at al., 2011; J.F. Lee et al., 2004; Lima

The sorption behaviour of triazines in soil directly influences their bioavailability to soil microorganisms and plants (Mudhoo & Garg, 2011), leading to their uptake and biodegradation. Numerous studies are available for atrazine as the most widely applied and apparently also persistent triazine in the soil (Jablonowski et al., 2011). Plant uptake of triazines from the contaminated soils is extensively studied as a means for bioremediation. The C4-metabolism plants show the greatest resistance to triazines and detoxify them by hydrolysis. Examples of plants shown to be useful in degrading atrazine in their rhizosphere are *Polygonum lapathifolium*, *Panicum dichotomiflorum* (Mudhoo & Garg, 2011), *Pennisetum* 

Ongoing research in the soil microorganisms capable of utilizing triazines as their energy source has resulted in an extensive array of isolated strains: *Acinetobacter* sp., *Cytophaga* sp., *Pseudomonas* sp., *Ralstonia* sp., *Agrobacterium* sp. (Mudhoo & Garg, 2011), *Klebsiella* sp. and *Comamonas* sp. (Yang et al., 2010), *Nocardioides* sp. and *Arthrobacter* sp. (Vibber et al., 2007). Most of them are capable of extensive mineralization of triazines (Mudhoo & Garg, 2011; Yang et al., 2010) and have a limited access even to aged herbicide residues in the soil (Jablonowski et al., 2008; Mudhoo & Garg, 2011). The species most often used for triazine degradation is *Pseudomonas* sp., its efficacy has been shown to be influenced by citrate addition (Jablonowski et al., 2008), soil humidity (Ngigi et al., 2011) and microorganism adsorption on simulated soil particle aggregates (Alekseeva et al., 2011). Green algae and diatoms (Mudhoo & Garg, 2011), as well as cyanobacteria (Gonzalez-Barreiro et al., 2006) are also capable of atrazine uptake and are thus a valuable option for the bioremediation of the contaminated waters. Certain fungal species able to grow on atrazine-contaminated soils

and capable of its uptake have been identified as well (Mudhoo & Garg, 2011).

potential for clean-up of contaminated sites (Konstantinou & Albanis, 2003).

problems, as schematically depicted in Fig. 3.

**6. Analytical approaches and cautions for triazine determination in soil** 

Triazine determination data for soil and other solid environmental samples are used to estimate the extent of the site pollution and potential toxicity (Jablonowski et al., 2011). However, determination of triazines and their TPs in solid samples is prone to many

Compared to biotic degradation by microorganisms and higher plants, abiotic degradation of triazines in soils is a minor dissipation route. Humic substances at low pH catalyse the hydrolysis of atrazine and its chlorinated transformation products to their hydroxy analogues (Prosen & Zupančič-Kralj, 2005). Photolysis of atrazine under solar irradiation and in the presence of humic substances was found to be negligible (Prosen & Zupančič-Kralj, 2005); however, simazine and terbutylazine were found to dissipate faster under solar irradiation of the soil (Navarro et al., 2009). Photolytic transformation and eventual mineralization is enhanced by using a suitable photocatalytic agent, e.g. TiO2, which holds a

et al., 2010; Mudhoo & Garg, 2011; Ying et al., 2005).

**5. Triazine degradation and uptake in the soil** 

*clandestinum* (Popov & Cornish, 2006; Singh et al., 2004).

Fig. 3. Schematic representation of the problems and solutions for triazine determination in solid environmental samples.


Table 3. Common extraction techniques for triazines from the solid environmental samples (Andreu & Pico, 2004; Camel, 2000; Lesueur et al., 2008; Lopez-Avila, 1999).

Fate and Determination of Triazine Herbicides in Soil 51

Determination of triazines in the extracts after extraction and clean-up is usually accomplished using either gas (GC) or liquid chromatography (HPLC) (Andreu & Pico, 2004). Both techniques can be coupled with mass spectrometry, enabling simultaneous confirmation of compound identity (Andreu & Pico, 2004; Lesueur et al., 2008; Min et al., 2008; Tsang et al., 2009; Usenko et al., 2005). Other detectors frequently used in triazine analysis are spectrophotometric, preferably diode-array detector for HPLC (Andreu & Pico, 2004; Kovačić et al., 2004; Prosen et al., 2004), and nitrogen-phosphorous detector for GC

Besides chromatography, other analytical techniques are seldom applied to triazine determination, although they may offer some significant advantages: electromigration techniques, e.g. micellar electrokinetic chromatography (Lima et al., 2009; Prosen et al., 2004); voltammetry (De Souza et al., 2007). Biosensors and bioassays are used for preliminary screening of samples or sample extracts, but because of their cross-reactivity the samples with analyte content above the cut-off value should be re-analysed by a more specific analytical technique. The most widely applied is antibody-based ELISA, but some innovative approaches have been developed, e.g. sensors based on photosystem-II inhibition from plant

Analytical determination of triazines in solid samples, although often seen as a routine procedure, is prone to many errors. Starting with sampling, the sample taken for analysis should be representative of that part of environment for which the information about pollutant concentration should be obtained. To achieve this goal, an appropriate number of samples, as well as time and site of sampling should be considered. Preservation of samples during the transport and storage is important as well and should be carefully selected (Kebbekus & Mitra, 1998). An example is the need to completely dechlorinate drinking water to prevent rapid degradation of triazines (Smith et al., 2008). Next step, namely extraction with clean-up, is again critical due to the possibility of significant analyte losses because of improper sample preparation conditions. These should be optimised and tested for every analyte. The choice between exhaustive and milder extraction techniques has already been mentioned, but mild conditions are also needed to avoid thermal degradation. Most triazines and their TPs are thermally stable, but not all (Tsang et al., 2009). Another caveat with extraction is the significant difference in analyte binding and thus extraction recoveries between freshly-spiked blank samples and real-life samples containing the so-called »aged residues«. Various authors have proposed to reproduce aging under environmental conditions by leaving spiked blank samples at room temperature for anything between 3 days and 2 years (Andreu & Pico, 2004). However, simulation may not necessarily yield equivalent results to field conditions (Louchart & Voltz, 2007). Finally, determination technique is important in terms of selectivity, limits of detection and reliable quantification. To achieve the latter, standard solutions for the calibration should always match the actual matrix as close as possible to avoid the significant matrix effects seen with some types of detectors (Kovačić et al., 2004), especially with

photosynthetic membranes (Bengtson Nash et al., 2005; Varsamis et al., 2008).

**7. Elucidation of triazine fate in the soil as influenced by analytical** 

As already explored in subchapter 4 of this review, we are mainly concerned with triazine sorption, desorption, leaching and plant/microorganism uptake when dealing with triazine

(Andreu & Pico, 2004; Stalikas et al., 2002).

electrospray interface for LC-MS.

**determination** 

The analytical procedure usually comprises of a suitable extraction technique (Table 3), preferably enabling preconcentration as well, possibly a clean-up step, and an appropriate determination technique (Andreu & Pico, 2004; Camel, 2000; Lesueur et al., 2008; Lopez-Avila, 1999). The first dilemma encountered is whether to use an exhaustive extraction technique or a more mild one. Extraction techniques regarded as exhaustive under most conditions are Soxhlet's, MASE and PLE (Camel, 2000). There is a high probability that even triazines bound to soil components would be extracted, although this may depend on the type of compound (Kovačić et al., 2004). However, most of the unwanted organic compounds from the sample would be transferred to extract as well, and these interferences have to be selectively removed prior to analysis by an appropriate clean-up technique. The key word in this case is selectivity, as the clean-up may otherwise lead to significant loss of analytes as well. A selection of frequently applied clean-up techniques is listed in Table 4. In the second case, i.e. by applying a mild extraction technique (0.01 M CaCl2 solution or aqueous methanol), the obtained extract would better reflect the actual fraction of the triazines and TPs available to plants and microorganisms (Regitano et al., 2006) and could thus be more useful for the actual assessment of the residual toxicity of triazines (Jablonowski et al., 2008; Jablonowski et al., 2011).


Table 4. Common clean-up techniques for triazines in soil/sediment extracts (Andreu & Pico, 2004; Hylton & Mitra, 2007; Jonsson & Mathiasson, 2000; Masque et al., 2001; Min et al., 2008; Psillakis & Kalogerakis, 2002; Stalikas et al., 2002).

The analytical procedure usually comprises of a suitable extraction technique (Table 3), preferably enabling preconcentration as well, possibly a clean-up step, and an appropriate determination technique (Andreu & Pico, 2004; Camel, 2000; Lesueur et al., 2008; Lopez-Avila, 1999). The first dilemma encountered is whether to use an exhaustive extraction technique or a more mild one. Extraction techniques regarded as exhaustive under most conditions are Soxhlet's, MASE and PLE (Camel, 2000). There is a high probability that even triazines bound to soil components would be extracted, although this may depend on the type of compound (Kovačić et al., 2004). However, most of the unwanted organic compounds from the sample would be transferred to extract as well, and these interferences have to be selectively removed prior to analysis by an appropriate clean-up technique. The key word in this case is selectivity, as the clean-up may otherwise lead to significant loss of analytes as well. A selection of frequently applied clean-up techniques is listed in Table 4. In the second case, i.e. by applying a mild extraction technique (0.01 M CaCl2 solution or aqueous methanol), the obtained extract would better reflect the actual fraction of the triazines and TPs available to plants and microorganisms (Regitano et al., 2006) and could thus be more useful for the actual assessment of the residual toxicity of triazines

Technique Principle Advantages Disadvantages Variants and







Table 4. Common clean-up techniques for triazines in soil/sediment extracts (Andreu & Pico, 2004; Hylton & Mitra, 2007; Jonsson & Mathiasson, 2000; Masque et al., 2001; Min et al.,

improvements

supported liquid membrane extr. (SLME) liquid-phase microextr. (LPME) / single-drop microextraction

restricted access material (RAM) molecularly imprinted polymer (MIP) immunosorbents multi-walled nanotubes

in-tube SPME

(Jablonowski et al., 2008; Jablonowski et al., 2011).

partitioning between two immiscible solvents

adsorption / partitioning between aqueous and solid phase, followed by desorption with organic solvents

partitioning between aqueous and non-polar phase on fibre, follow by thermal or solvent desorption

2008; Psillakis & Kalogerakis, 2002; Stalikas et al., 2002).

Liquid-Liquid Extraction (LLE)

Solid Phase Extraction (SPE)

Solid Phase Microextraction (SPME)

Determination of triazines in the extracts after extraction and clean-up is usually accomplished using either gas (GC) or liquid chromatography (HPLC) (Andreu & Pico, 2004). Both techniques can be coupled with mass spectrometry, enabling simultaneous confirmation of compound identity (Andreu & Pico, 2004; Lesueur et al., 2008; Min et al., 2008; Tsang et al., 2009; Usenko et al., 2005). Other detectors frequently used in triazine analysis are spectrophotometric, preferably diode-array detector for HPLC (Andreu & Pico, 2004; Kovačić et al., 2004; Prosen et al., 2004), and nitrogen-phosphorous detector for GC (Andreu & Pico, 2004; Stalikas et al., 2002).

Besides chromatography, other analytical techniques are seldom applied to triazine determination, although they may offer some significant advantages: electromigration techniques, e.g. micellar electrokinetic chromatography (Lima et al., 2009; Prosen et al., 2004); voltammetry (De Souza et al., 2007). Biosensors and bioassays are used for preliminary screening of samples or sample extracts, but because of their cross-reactivity the samples with analyte content above the cut-off value should be re-analysed by a more specific analytical technique. The most widely applied is antibody-based ELISA, but some innovative approaches have been developed, e.g. sensors based on photosystem-II inhibition from plant photosynthetic membranes (Bengtson Nash et al., 2005; Varsamis et al., 2008).

Analytical determination of triazines in solid samples, although often seen as a routine procedure, is prone to many errors. Starting with sampling, the sample taken for analysis should be representative of that part of environment for which the information about pollutant concentration should be obtained. To achieve this goal, an appropriate number of samples, as well as time and site of sampling should be considered. Preservation of samples during the transport and storage is important as well and should be carefully selected (Kebbekus & Mitra, 1998). An example is the need to completely dechlorinate drinking water to prevent rapid degradation of triazines (Smith et al., 2008). Next step, namely extraction with clean-up, is again critical due to the possibility of significant analyte losses because of improper sample preparation conditions. These should be optimised and tested for every analyte. The choice between exhaustive and milder extraction techniques has already been mentioned, but mild conditions are also needed to avoid thermal degradation. Most triazines and their TPs are thermally stable, but not all (Tsang et al., 2009). Another caveat with extraction is the significant difference in analyte binding and thus extraction recoveries between freshly-spiked blank samples and real-life samples containing the so-called »aged residues«. Various authors have proposed to reproduce aging under environmental conditions by leaving spiked blank samples at room temperature for anything between 3 days and 2 years (Andreu & Pico, 2004). However, simulation may not necessarily yield equivalent results to field conditions (Louchart & Voltz, 2007). Finally, determination technique is important in terms of selectivity, limits of detection and reliable quantification. To achieve the latter, standard solutions for the calibration should always match the actual matrix as close as possible to avoid the significant matrix effects seen with some types of detectors (Kovačić et al., 2004), especially with electrospray interface for LC-MS.

#### **7. Elucidation of triazine fate in the soil as influenced by analytical determination**

As already explored in subchapter 4 of this review, we are mainly concerned with triazine sorption, desorption, leaching and plant/microorganism uptake when dealing with triazine

Fate and Determination of Triazine Herbicides in Soil 53

Pico, 2004; Camel, 2000; Hylton & Mitra, 2007; Jonsson & Mathiasson, 2000; Lopez-Avila,

Author would like to acknowledge the financial support from the Ministry of Higher

Aboul-Kasim, T. A. T., Simoneit, B. R. T. (2001). *Pollutant-solid phase interactions*. Springer,

Alekseeva, T., Prevot, V., Sancelme, M., Forano, C., Besse-Hoggan, P. (2011). Enhancing

Andreu, V., Picó, Y. (2004). Determination of pesticides and their degradation products in

Barton, C. D., Karathanasis, A. D. (2003). Influence of soil colloids on the migration of

Bengtson Nash, S. M., Schreiber, U., Ralph, P. J., Müller, J. F. (2005). The combined

Bermúdez-Saldaña, J. M., Escuder-Gilabert, L., Medina-Hernández, M. J., Villanueva-

Camel, V. (2000). Microwave-assisted solvent extraction of environmental samples. *Trends* 

Celano, G., Šmejkalova, D., Spaccini, R., Piccolo, A. (2008). Interactions of three *s*-triazines

Delgado-Moreno, L., Pena, A., Almendros, G. (2010). Contribution by different organic

Domange, N., Grégoire, C., Gouy, V., Tremolières, M. (2004). Effet du vieillissement des

solution. Abridged English version. *C. R. Geoscience*, Vol.336, 49-58.

biotransformed olive cake. *Journal of Hazardous Materials*, Vol.174, 93-99. De Souza, D., de Toledo, R. A., Galli, A., Salazar-Banda, G. R., Silva, M. R. C., Garbellini, G.

atrazine biodegradation by *Pseudomonas* sp. strain ADP adsorption to Layered Double Hydroxide bionanocomposites. *Journal of Hazardous Materials*, Vol.191, 126-

soil: critical review and comparison of methods. *Trends in Analytical Chemistry*,

atrazine and zinc through large soil monoliths. *Water, Air and Soil Pollution*, Vol.143,

SPE:ToxY-PAM phytotoxicity assay; application and appraisal of a novel biomonitoring tool for the aquatic environment. *Biosensors Bioelectronics*, Vol.20,

Camañas, R. M., Sagrado, S. (2006). Chromatographic estimation of the soilsorption coefficients of organic compounds. *Trends in Analytical Chemistry*, Vol.25,

with humic acids of different structure. *Journal of Agricultural Food Chemistry*,

fractions to triazines sorption in Calcaric Regosol amended with raw and

S., Mazo, L. H., Avaca, L. A., Machado, S. A. S. (2007). Determination of triazine herbicides: development of an electroanalytical method utilizing a solid amalgam electrode that minimizes toxic waste residues, and a comparative study between voltammetric and chromatographic techniques. *Analytical Bioanalytical Chemistry*,

céramiques poreuses sur leur capacité à évaluer la concentration de pesticide en

Education, Science and Technology of the Republic Slovenia through Grant P1-0153.

1999; Masque et al., 2001; Psillakis & Kalogerakis, 2002).

**9. Acknowledgment** 

Berlin, Germany.

Vol.23, 772-789.

**10. References** 

135.

3-21.

1443-1451.

122-132.

Vol.56, 7360-7366.

Vol.387, 2245-2253.

*in Analytical Chemistry*, Vol.19, 229-248.

fate in the soil. Sorption in its broadest sense (i.e. partitioning, non-covalent and covalent binding) is usually evaluated by sorption isotherms conforming to various theoretical models: Freundlich, Langmuir, Polanyi-Dubinin-Manes, etc. (Aboul-Kasim & Simoneit, 2001; Kleineidam et al., 2002). The most frequently used method to obtain the experimental data for isotherm construction remains the batch equilibrium method (Celano et al., 2008; Kleineidam et al., 2002; Konda et al., 2002; Kovaios et al., 2006; Lima et al., 2009; Ling et al., 2006; Stipičević et al., 2009). Other approaches are by chromatographic estimation (Bermudez-Saldana et al., 2006) or indirectly by structural descriptors (Schüürmann et al., 2006). In batch equilibrium method, several variables may influence the process of sorption and have to be carefully optimised: organic solvent content, ionic strength and pH, solid/solution ratio, sorption time (Celano et al., 2008; Kleineidam et al., 2002; Kovaios et al., 2006; Prosen & Zupančič-Kralj, 2000; Prosen et al., 2007). After the equilibrium is reached, the solution has to be separated from the sorbent either by centrifugation or filtration (Kleineidam et al., 2002). By using the latter, another potential source of error is introduced as more hydrophobic compounds may bind to certain types of filters.

The equilibrium concentration of the pollutant in the solution after the separation is determined by any of the analytical methods mentioned in subchapter 6. Preferably, it should be performed without previous extraction as this introduces another equilibrium and another possible source of error. Thus, direct HPLC (Celano et al., 2008; Prosen & Zupančič-Kralj, 2000) or electromigration techniques (Erny et al., 2011; Lima et al., 2009) are the methods of choice. If radiolabelled compounds are used, their equilibrium concentration can be measured by radioactivity measurement (Jablonowski et al., 2008). A different approach is to determine the free concentration directly in a multi-phase system by a nonexhaustive solid-phase microextraction and subsequent GC analysis (Heringa & Hermens, 2003; S. Lee et al., 2003; Prosen et al., 2007). The depletion of the compounds from the solution is considered to be negligible, thus giving the opportunity to measure the true equilibrium concentration in the solution (Heringa & Hermens, 2003). Distribution coefficients *K*d obtained by SPME-GC determination of equilibrium concentrations after the sorption experiment have been reported to be significantly different compared to those obtained by other determination methods (S. Lee et al., 2003).

As well as for sorption/desorption, the understanding of the leaching behaviour of triazines is significantly influenced by the determination method. The usual approach is to evaluate the mobility of the compound in soil columns by lysimeters (Jablonowski et al., 2011; Weber et al., 2007), but experiments should be conducted under the appropriate time-scale to avoid gross underestimations (Jablonowski et al., 2011). A different approach is the use of ceramic suction cups, but these are also prone to errors due to ageing effects (Domange et al., 2004).

#### **8. Conclusions**

This review attempts to cover a vast subject of triazine behaviour in the environment, especially soil, as well as their analytical determination in the same. Special attention was given to the various problems encountered in both. However, the broadness of the subject prevents its detailed evaluation; the interested reader can find more information in other excellent reviews that focus more on triazine behaviour in solid environmental compartment (Jablonowski et al., 2011; Mudhoo & Garg, 2011), their degradation and elimination (Konstantinou & Albanis, 2003) or the applied analytical methods (Andreu & Pico, 2004; Camel, 2000; Hylton & Mitra, 2007; Jonsson & Mathiasson, 2000; Lopez-Avila, 1999; Masque et al., 2001; Psillakis & Kalogerakis, 2002).

#### **9. Acknowledgment**

Author would like to acknowledge the financial support from the Ministry of Higher Education, Science and Technology of the Republic Slovenia through Grant P1-0153.

#### **10. References**

52 Herbicides – Properties, Synthesis and Control of Weeds

fate in the soil. Sorption in its broadest sense (i.e. partitioning, non-covalent and covalent binding) is usually evaluated by sorption isotherms conforming to various theoretical models: Freundlich, Langmuir, Polanyi-Dubinin-Manes, etc. (Aboul-Kasim & Simoneit, 2001; Kleineidam et al., 2002). The most frequently used method to obtain the experimental data for isotherm construction remains the batch equilibrium method (Celano et al., 2008; Kleineidam et al., 2002; Konda et al., 2002; Kovaios et al., 2006; Lima et al., 2009; Ling et al., 2006; Stipičević et al., 2009). Other approaches are by chromatographic estimation (Bermudez-Saldana et al., 2006) or indirectly by structural descriptors (Schüürmann et al., 2006). In batch equilibrium method, several variables may influence the process of sorption and have to be carefully optimised: organic solvent content, ionic strength and pH, solid/solution ratio, sorption time (Celano et al., 2008; Kleineidam et al., 2002; Kovaios et al., 2006; Prosen & Zupančič-Kralj, 2000; Prosen et al., 2007). After the equilibrium is reached, the solution has to be separated from the sorbent either by centrifugation or filtration (Kleineidam et al., 2002). By using the latter, another potential source of error is introduced

The equilibrium concentration of the pollutant in the solution after the separation is determined by any of the analytical methods mentioned in subchapter 6. Preferably, it should be performed without previous extraction as this introduces another equilibrium and another possible source of error. Thus, direct HPLC (Celano et al., 2008; Prosen & Zupančič-Kralj, 2000) or electromigration techniques (Erny et al., 2011; Lima et al., 2009) are the methods of choice. If radiolabelled compounds are used, their equilibrium concentration can be measured by radioactivity measurement (Jablonowski et al., 2008). A different approach is to determine the free concentration directly in a multi-phase system by a nonexhaustive solid-phase microextraction and subsequent GC analysis (Heringa & Hermens, 2003; S. Lee et al., 2003; Prosen et al., 2007). The depletion of the compounds from the solution is considered to be negligible, thus giving the opportunity to measure the true equilibrium concentration in the solution (Heringa & Hermens, 2003). Distribution coefficients *K*d obtained by SPME-GC determination of equilibrium concentrations after the sorption experiment have been reported to be significantly different compared to those

As well as for sorption/desorption, the understanding of the leaching behaviour of triazines is significantly influenced by the determination method. The usual approach is to evaluate the mobility of the compound in soil columns by lysimeters (Jablonowski et al., 2011; Weber et al., 2007), but experiments should be conducted under the appropriate time-scale to avoid gross underestimations (Jablonowski et al., 2011). A different approach is the use of ceramic suction cups, but these are also prone to errors due to ageing effects (Domange et al., 2004).

This review attempts to cover a vast subject of triazine behaviour in the environment, especially soil, as well as their analytical determination in the same. Special attention was given to the various problems encountered in both. However, the broadness of the subject prevents its detailed evaluation; the interested reader can find more information in other excellent reviews that focus more on triazine behaviour in solid environmental compartment (Jablonowski et al., 2011; Mudhoo & Garg, 2011), their degradation and elimination (Konstantinou & Albanis, 2003) or the applied analytical methods (Andreu &

as more hydrophobic compounds may bind to certain types of filters.

obtained by other determination methods (S. Lee et al., 2003).

**8. Conclusions** 


Fate and Determination of Triazine Herbicides in Soil 55

Konda, L. N., Czinkota, I., Fueleky, G., Morovjan, G. (2002). Modeling of single-step and

Konstantinou, I. K., Albanis, T. A. (2003). Photocatalytic transformation of pesticides in

Kovaios, I. D., Paraskeva, C. A., Koutsoukos, P. G., Payatakes, A. C. (2006). Adsorption of atrazine on soils: Model study. *Journal of Colloid Interface Science*, Vol.299, 88-94. Lee, J. F., Hsu, M. H., Chao, H. P., Huang, H. C., Wang, S. P. (2004). The effect of surfactants

Lee, S., Gan, J., Liu, W. P., Anderson, M. A. (2003). Evaluation of *K*d underestimation using solid phase microextraction. *Environmental Science Technology*, Vol.37, 5597-5602. Lesueur, C., Gartner, M., Mentler, A., Fuerhacker, M. (2008). Comparison of four extraction

Lima, D. L. D., Erny, G. L., Esteves, V. I. (2009). Application of MEKC to the monitoring of

Lima, D. L. D., Schneider, R. J., Scherer, H. W., Duarte, A. C., Santos, E. B. H., Esteves, V. I.

Ling, W., Xu, J., Gao, Y. (2006). Dissolved organic matter enhances the sorption of atrazine

Lopez-Avila, V. (1999). Sample preparation for environmental analysis. *Critical Reviews in* 

Louchart, X., Voltz, M. (2007). Aging effects on the availability of herbicides to runoff

Masqué, N., Marcé, R. M., Borrull, F. (2001). Molecularly imprinted polymers: new tailor-

Min, G., Wang, S., Zhu, H., Fang, G., Zhang, Y. (2008). Multi-walled carbon nanotubes as

Mudhoo, A., Garg, V.K. (2011). Sorption, transport and transformation of atrazine in soils,

Navarro, S., Bermejo, S., Vela, N., Hernandez, J. (2009). Rate of loss of simazine,

made materials for selective solid-phase extraction. *Trends in Analytical Chemistry*,

solid-phase extraction adsorbents for determination of atrazine and its principal metabolites in water and soil samples by gas chromatography-mass spectrometry.

terbuthylazine, isoproturon, and methabenzthiazuron during soil solarization.

by soil. *Biological Fertilization of Soils*, Vol.42, 418-425.

*Science of the Total Environment*, Vol.396, 79-85.

transfer. *Environmental Science Technology*, Vol.41, 1137-1144.

minerals and composts: a review. *Pedosphere*, Vol.21, 11-25.

*Journal of Agricultural Food Chemistry*, Vol.57, 6375-6382.

*Analytical Chemistry*, Vol.29, 195-230.

*Food Chemistry*, Vol.50, 7326-7331.

*Hazardus Materials B*, Vol.114, 123-130.

Vol.51, 395-407.

*Talanta*, Vol.75, 284-293.

3106.

Vol.20, 477-486.

multistep adsorption isotherms of organic pesticides on soil. *Journal of Agricultural* 

aqueous TiO2 suspensions using artificial and solar light: intermediates and degradation pathways. Review. *Applied Catalysis B: Environmental*, Vol.42, 319-335. Kovačić, N., Prosen, H., Zupančič-Kralj, L. (2004). Determination of triazines and atrazine

metabolites in soil by microwave-assisted solvent extraction and high-pressure liquid chromatography with photo-diode-array detection. *Acta Chimica Slovenica*,

on the distribution of organic compounds in the soil solid/water system. *Journal of* 

methods for the analysis of 24 pesticides in soil samples with gas chromatography– mass spectrometry and liquid chromatography–ion trap–mass spectrometry.

atrazine sorption behaviour on soils. *Journal of Separation Science*, Vol.32, 4241-4246.

(2010). Sorption-desorption behavior of atrazine on soils subjected to different organic long-term amendments. *Journal of Agricultural Food Chemistry*, Vol.58, 3101-


Drori, Y., Aizenshtat, Z., Chefetz, B. (2005). Sorption-desorption behavior of atrazine in soils

Eldridge, J. C., Wetzel, L. T., Tyrey, L. (1999). Estrous cycle patterns of Sprague-Dawley rats

Environmental Protection Agency (2006). Cumulative Risk From Triazine Pesticides. Doc. ID EPA-HQ-OPP-2005-0481-0003. Available from: http://www.regulations.gov/ Erny, G. L., Calisto, V., Lima, D. L. D., Esteves, V. I. (2011). Studying the interaction between

Filipov, N. M., Pinchuk, L. M., Boyd, B. L., Crittenden, P. L. (2005). Immunotoxic effects of

Gonzalez-Barreiro, O., Rioboo, C., Herrero, C., Cid, A. (2006). Removal of triazine herbicides

Heringa, M. B., Hermens, J. L. M. (2003). Measurement of free concentrations using

Hylton, K., Mitra, S. (2007). Automated, on-line membrane extraction. Review. *Journal of* 

Jablonowski, N. D., Modler, J., Schaeffer, A., Burauel, P. (2008). Bioaccessibility of

Jones, D. L., Edwards-Jones, G., Murphy, D. V. (2011). Biochar mediated alterations in

Jönsson, J. Å., Mathiasson, L. (2000). Membrane-based techniques for sample enrichment.

Kaune, A., Brüggemann R., Kettrup, A. (1998). High-performance liquid chromatographic

Kleineidam, S., Schueth, C., Grathwohl, P. (2002). Solubility-normalized combined

Kniewald, J., Jakominić, M., Tomljenović, A., Šimić, B., Romac, P., Vranešić, Đ., Kniewald, Z.

*Environmental Science of Pollution Research*, Vol.18, 328-331.

Review. *Journal of Chromatography A*, Vol.902, 205-225.

eletrochromatography. *Talanta*, Vol.84, 424-429.

1703-1710.

491-499.

Vol.86, 324-332.

*Pollution*, Vol.144, 266-271.

*Chemistry*, Vol.22, 575-587.

http://sitem.herts.ac.uk/aeru/iupac/

Boca Raton, FL, USA.

*Science Technology*, Vol.36, 4689-4697.

*Journal of Applied Toxicology*, Vol.20, 61-68.

*Chromatography A*, Vol. 152, 199-214. IUPAC Agrochemical Information (2011). Available from:

irrigated with reclaimed wastewater. *Soil Science Society of America Journal,* Vol.69,

during acute and chronic atrazine administration. *Reproductive Toxicology*, Vol.13,

triazines and humic substances—A new approach using open tubular capillary

short-term atrazine exposure in young male C57BL/6 mice. *Toxicological Science*,

from freshwater systems using photosynthetic microorganisms. *Environmental* 

negligible depletion-solid phase microextraction (nd-SPME). *Trends in Analytical* 

environmentally aged 14C-atrazine residues in an agriculturally used soil and its particle-size aggregates. *Environmental Science Technology*, Vol.42, 5904-5910. Jablonowski, N. D., Schäffer, A., Burauel, P. (2011). Still present after all these years:

persistence plus potential toxicity raise questions about the use of atrazine.

herbicide breakdown and leaching in soil. *Soil Biology Biochemistry*, Vol.43, 804-813.

measurement of the 1-octanol-water part. coefficient of *s*-triazine herbicides and some of their degradation products. *Journal of Chromatography A*, Vol.805, 119-126. Kebbekus, B. B., Mitra, S. (1998). *Environmental chemical analysis*. Chapman & Hall/CRC,

adsorption-partitioning sorption isotherms for organic pollutants. *Environmental* 

(2000). Disorders of male rat reproductive tract under the influence of atrazine.


Fate and Determination of Triazine Herbicides in Soil 57

Solomon, K. R., Carr, J. A., Du Preez, L. H., Giesy, J. P., Kendall, R. J., Smith, E. E., Van Der

Stalikas, C., Knopp, D., Niessner, R. (2002). Sol-gel glass immunosorbent-based

Stanko, J. P., Enoch, R. R., Rayner, J. L., Davis, C. C., Wolf, D. C., Malarkey, D. E., Fenton, S.

Stevens, J. T., Sumner, D. D. (1991). Herbicides. In: *Handbook of Pesticide Toxicology*, Hayes,

Stipičević, S., Fingler, S., Drevenkar, V. (2009). Effect of organic and mineral soil fractions on

Taketa, Y., Yoshida, M., Inoue, K., Takahashi, M., Sakamoto, Y., Watanabe, G., Taya, K.,

Tavera-Mendoza, L., Ruby, S., Brousseau, P., Fournier, M., Cyr, D., Marcogliese, D. (2002).

Tomlin, C. (ed.) (1994). *The Pesticide Manual Incorporating the Agrochemicals Handbook.* British

Tsang, V. W. H., Lei, N. Y., Lam, M. H. W. (2009). Determination of Irgarol-1051 and its

Usenko, S., Hageman, K.J., Schmedding, D. W., Wilson, G. R., Simonich, S. L. (2005). Trace

Vibber, L. L., Pressler, M. J., Colores, G. M. (2007). Isolation and characterization of novel

Weber, J. B., Warren, R. L., Swain, L. R., Yelverton, F. H. (2007). Physicochemical property

critical review. *Critical Reviews in Toxicology*, Vol.38, 721-772.

W. J., Laws, E.R. (eds.), Academic Press, San Diego, CF, USA.

*Hygiene and Occupational Toxicology*, Vol.60, 43-52.

Crop Protection Council, Surrey, UK.

herbicide detection. *Talanta*, Vol.77, 42-47.

*and Biotechnology*, Vol.75, 921-928.

*Crop Protection*, Vol.26, 299-311.

MS/MS. *Marine Pollution Bulletin*, Vol.58, 1462-1471.

*Journal of Chromatography A*, Vol.1202, 138-144.

Vol.36, 3372-3377.

278.

531.

*Toxicology*, Vol.30, 540-549.

waters using direct injection liquid chromatography tandem mass spectrometry.

Kraak, G. J. (2008). Effects of atrazine on fish, amphibians, and aquatic reptiles: A

determination of *s*-triazines in water and soil samples using gas chromatography with a nitrogen phosphorus detection system. *Environmental Science Technology*,

E. (2010). Effects of prenatal exposure to a low dose atrazine metabolite mixture on pubertal timing and prostate development of male Long-Evans rats. *Reproductive* 

sorption behaviour of chlorophenol and triazine micropollutants. *Archives of* 

Yamate, J., Nishikawa, A. (2011). Differential stimulation pathways of progesterone secretion from newly formed corpora lutea in rats treated with ethylene glycol monomethyl ether, sulpiride, or atrazine. *Toxicological Sciences*, Vol.121, 267-

Response of the amphibian tadpole (*Xenopus laevis*) to atrazine during sexual differentiation of the testis. *Environmental Toxicology and Chemistry*, Vol.21, 527-

related *s*-triazine species in coastal sediments and mussel tissues by HPLC–ESI-

analysis of semivolatile organic compounds in large volume samples of snow, lake water, and groundwater. *Environmental Science Technology*, Vol.39, 6006-6015. Varsamis, D. G., Touloupakis, E., Morlacchi, P., Ghanotakis, D. F., Giardi, M. T., Cullen, D.

C. (2008). Development of a photosystem II-based optical microfluidic sensor for

atrazine-degrading microorganisms from an agricultural soil. *Applied Microbiology* 

effects of three herbicides and three soils on herbicide mobility in field lysimeters.


Ngigi, A., Dörfler, U., Scherb, H., Getenga, Z., Boga, H., Schroll, R. (2011). Effect of

Noble, A. (1993). Partition coefficients (*n*-octanol-water) for pesticides. *Journal of* 

Polkowska, Ž., Kot, A., Wiergowski, M., Wolska, L., Wolowska, K., Namiesnik, J. (2000).

Popov, V. H., Cornish, P.S. (2006). Atrazine tolerance of grass species with potential for use

Prosen, H., Zupančič-Kralj, L. (2000). The interaction of triazine herbicides with humic acids.

Prosen, H., Guček, M., Zupančič-Kralj, L. (2004). Optimization of liquid chromatography

Prosen, H., Zupančič-Kralj, L. (2005). Evaluation of photolysis and hydrolysis of atrazine

Prosen, H., Fingler, S., Zupančič-Kralj, L., Drevenkar, V. (2007). Partitioning of selected

Psillakis, E., Kalogerakis, N. (2002). Developments in liquid-phase microextraction. *Trends in* 

Regitano, J. B., Koskinen, W. C., Sadowsky, M. J. (2006). Influence of soil aging on sorption

Sass, J. B., Colangelo, A. (2006). European Union bans atrazine, while the United States

Schaumann, G. E. (2006). Review Article - Soil organic matter beyond molecular structure.

Schüürmann, G., Ebert, R. U., Kühne, R. (2006). Prediction of sorption of organic compounds

Shiu, W.Y., Ma, K.C., Mackay, D., Seiber, J.N., Wauchope, R.D. (1990). Solubilities of

Singh, N., Megharaj, M., Kookana, R. S., Naidu, R., Sethunathan, N. (2004). Atrazine and simazine degradation in Pennisetum rhizosphere. *Chemosphere*, Vol.56, 257-263. Smith, G. A., Pepich, B. V., Munch, D. J. (2008). Preservation and analytical procedures for

in vegetated filters in Australia. *Plant Soil*, Vol.280, 115-126.

*Chromatographia Supplement*, Vol. 51, S155-S164.

*Chromatographia Supplement*, Vol.60, 107-112.

microextraction. *Chemosphere*, Vol.66, 1580-1589.

*Pollution*, Vol.133, 517-529.

*Health*, Vol.12, 260-267.

Vol.40, 7005-7011.

*Analytical Chemistry*, Vol.21, 53-63.

*and Soil Science*, Vol.169, 145-156.

*Contamination and Toxicology*, Vol.116, 15-187.

*Chemosphere*, Vol.84, 369-375.

*Chromatography*, Vol.642, 3-14.

1245.

1379.

fluctuating soil humidity on in situ bioavailability and degradation of atrazine.

Organic pollutants in precipitation: determination of pesticides and polycyclic aromatic hydrocarbons in Gdansk, Poland. *Atmospheric Environment*, Vol.34, 1233-

and micellar electrokinetic chromatography for the determination of atrazine and its first degradation products in humic waters without sample preparation.

and its first degradation products in the presence of humic acids. *Environmental* 

environmental pollutants into organic matter as determined by solid-phase

and bioavailability of simazine. *Journal of Agricultural Food Chemistry*, Vol.54, 1373-

negotiates continued use. *International Journal of Occupational and Environmental* 

Part I: Macromolecular and supramolecular characteristics. *Journal of Plant Nutrition* 

into soil organic matter from molecular structure. *Environmental Science Technology*,

pesticide chemicals in water. Part II: data compilation. *Reviews of. Environmental* 

the analysis of chloro-*s*-triazines and their chlorodegradate products in drinking

waters using direct injection liquid chromatography tandem mass spectrometry. *Journal of Chromatography A*, Vol.1202, 138-144.


**4** 

*USA* 

S.A. Clay and D.D. Malo

*Brookings, South Dakota* 

**The Influence of Biochar Production on** 

Biochar is the by-product of a thermal process conducted under low oxygen or oxygen-free conditions (pyrolysis) to convert vegetative biomass to biofuel (Jha et al., 2010). There are a wide variety of end-products that can be manufactured depending on processing parameters and initial feedstocks (Bridgewater, 2003). The pyrolytic process parameters such as temperature, heating rate, and pressure can change the recovery amounts of each end-product, energy values of the bio-oils, and the physico-chemical properties of biochar

Biochars are recalcitrant forms of carbon and, depending on properties, can remain in the soil for greater than 1000 years (Skjemstad et al., 2002). The long-term persistence of this carbon form is due to slow microbial degradation and chemical oxidation rates (Sanchez et al., 2009). In addition, biochar interacts with soil materials such as ions, organic matter, and clays that generally increase the persistence of biochar within the soil. However, biochars, unlike commercial fertilizers, are not precisely defined materials and vary widely in properties depending on organic material source and manufacturing process (Karaosmanoglu et al., 2000; McHenry, 2009; Sohi et al., 2010). Increasing pyrolytic temperature decreases biochar recovery but increases C concentration of the char compared with char recovered at lower temperatures (Daud et al., 2001; Katyal et al., 2003). For example, as temperature increased from 3000 to 8000 C, biochar C content increased from 56 to 93% whereas biochar yield decreased from 67 to 26% (Okimori et al., 2003). Other pyrolytic parameters, such as sweep gas flow, can influence biochar particle size with higher flows reducing the particle size but increasing heating values (Katyal et al., 2003; Demirbas, 2004). Biochar also can be influenced by reactor design and other reaction parameters including heating rate, residence time, pressure, and catalyst used. Feedstock type, quality, and initial physical characteristics of the material (e.g. particle size, shape, and structure) can impact the bio-oil yield and properties, as well as the type and amounts of biochar formed

Landspreading biochar for a soil amendment is suggested to improve crop production efficiency because regardless of the initial manufacturing process, biochars have a high charge density and surface area. The use of biochar as a soil amendment is not a new concept. Dark earths (terra preta) discovered in the Amazon Basin were found to have

**1. Introduction** 

(Yaman, 2004).

(Bridgewater et al., 1999).

**Herbicide Sorption Characteristics** 

*South Dakota State University, Plant Science Dept.* 

