Australian Journal of Soil Research - CSIRO Publishing

P u b l i s h i n g

Australian Journal of Soil Research Volume 40, 2002 © CSIRO 2002

An international journal for the publication of original research into all aspects of soil science

All enquiries and manuscripts should be directed to: Australian Journal of Soil Research CSIRO Publishing PO Box 1139 (150 Oxford St) Collingwood, Vic. 3066, Australia Telephone: +61 3 9662 7628 Fax: +61 3 9662 7611 Email: [email protected] Published by CSIRO Publishing for CSIRO and the Australian Academy of Science

w w w. p u b l i s h . c s i ro . a u / j o u r n a l s / a j s r

Aust. J. Soil Res., 2002, 40, 1085–1094

Sorption of pesticides used in banana production on soils of Ecuador Tanya CáceresA, Guang-Guo YingB, and Rai KookanaBC A

Comision Ecuatoriana de Energia Atomica, Apartado 17-01-2517, Quito, Ecuador. CSIRO Land and Water, Adelaide Laboratory, PMB 2, Glen Osmond, SA 5064, Australia. C Corresponding author; email: [email protected] B

Abstract There is concern about the migration and adverse impact of pesticides used in banana production systems in Ecuador on aquaculture and ecosystem health. Therefore, we studied the sorption of chlorothalonil, fenamiphos, and its 2 metabolites (fenamiphos sulfone and fenamiphos sulfoxide), by batch method on 6 surface soils from the Guayas River Basin (1–3°S, 79–81°W), a major banana production area of Ecuador. The sorption of chlorothalonil on the 6 soils was high and varied considerably as shown by the Kd values ranging from 68.50 to 152.60 L/kg. The sorption coefficients normalised with the organic carbon content of soil (Koc) for chlorothalonil ranged from 2330 to 7336 kg/L, with a mean value of 4012 kg/L. These Koc values are higher than those previously reported in the literature. The sorption of fenamiphos and its metabolites to the 6 soils varied among soils in a similar pattern. The Kd values ranged from 5.66 to 14.31 L/kg for fenamiphos, from 2.81 to 8.79 L/kg for fenamiphos sulfone, and from 0.77 to 4.00 L/kg for fenamiphos sulfoxide, respectively. In all of the soils the sorption coefficients of both metabolites of fenamiphos were lower than that for the parent compound. The Koc values ranged from 220 to 515 kg/L (mean value 371 kg/L) for fenamiphos, from 29 to 141 kg/L (mean value of 76 kg/L) for fenamiphos sulfoxide, and from 79 to 334 kg/L (mean value of 191 kg/L) for fenamiphos sulfone. Chlorothalonil had much stronger sorption than fenamiphos and its metabolites on the Ecuadorian soil. Due to lower sorption and therefore greater mobility and longer persistence of the fenamiphos metabolites, these compounds need adequate consideration during residue monitoring and assessment of potential off-site impacts on ecosystem health and aquaculture in the Guayas River Basin. SR0215 TeSa.Cátolrp.ctieornsofpesitcideson Ecuadoreansoils

Additional keywords: sorption, pesticides, water quality, aquaculture, Guayas River Basin.

Introduction Banana production and aquaculture are two important sources of export income for Ecuador, together constituting about 50% of the total export. The majority of banana plantations are located along the Guayas River Basin in La Costa region of Ecuador (1–3°S, 79–81°W). Pesticides are commonly used to control agricultural pests in banana plantations in this area. Fungal diseases such as Black Sigatoca and nematodes are the main problems in banana plantations. Nematodes damage banana crops by burrowing into the base of plants and promoting fungal and bacterial infestation (Stover and Simmonds 1987). Fungicides and nematicides are important groups of pesticides for banana production in several countries, including Australia (e.g. Brown and Rachman 1996). From the data supplied by the Ecadorian authorities, chlorothalonil, mancozeb, benomyl, and triazoles (e.g. propiconazole, tebuconazole, biternatol) were among the commonly used fungicides, and fenamiphos, cadusafos, terbufos, and ethoprop were the commonly used nematicides in the plantations. The pesticides are applied through aerial spraying in some major plantations. Aquaculture is also a major industry in the Guayas River Basin and there is considerable concern about the potential off-site impacts of pesticides used in banana production on the ecosystem health and, in particular, on the aquaculture industry. Currently no monitoring © CSIRO 2002

10.1071/SR02015

0004-9573/02/071085

1086

T. Cáceres et al.

data on pesticide residues in surface water are available from Ecuador. However, reports from similar banana production systems from Costa Rica have shown the presence of pesticide residues, including fungicides and nematicides, in water draining plantations (Castillo et al. 1998). Data on the environmental fate of pesticides in soils, such as sorption and degradation half-life, are essential for assessing the potential off-site impact of commonly used pesticides in Ecuador. Sorption of a pesticide on soil particles is an important process that influences the persistence and movement of pesticide in soil (Koskinen and Harper 1990). However, such data are currently not available on Ecuadorian soils. The study is linked to a major project on minimising off-site impact of pesticides in Ecuador, under the FAO/IAEA program in Food and Agriculture. The objective of this study was to quantify the sorption of chlorothalonil, fenamiphos, and its 2 metabolites on selected soils from the Guayas River Basin, Ecuador. Chlorothalonil and fenamiphos were chosen for this study because they represent the 2 important groups of pesticides in banana production systems in Ecuador and both have high toxicity to fish. The sorption data are to be used as an input for the assessment of the potential migration of pesticides into shrimp farms located downstream of banana plantations in the Guayas River Basin. Materials and methods Pesticides Chlorothalonil (tetrachloroisophthalonitrile) acts on the thiol groups of enzymes and, therefore, shows a broad spectrum of fungicidal activity (Vincent and Sisler 1968). It is generally applied at a dose of 1.5 kg/ha. The fungicide formulations are mainly in petroleum oil and applied at least 3 times a year. Chlorothalonil is quite stable to UV light in aqueous media and in the crystalline state (Peñuela and Barceló 1998). It degrades mainly through dechlorination and partly through a substitution reaction due to microbial action (Sato and Tanaka 1987). Chlorothalonil and its metabolites are highly toxic to fish, aquatic invertebrates, and marine organisms (Kidd and James 1991). It has a low water solubility of 0.6 mg/L and is moderately persistent in soil (Kidd and James 1991). The degradation of chlorothalonil in soil was suppressed by its repeated applications and can be restored by amendment with organic matter (Katayama et al. 1991; Takagi et al. 1991; Katyama et al. 1995). Fenamiphos (ethyl 4-methylthion-m-tolyl isopropylphosphoramidate) is an organophosphate pesticide that is commonly used for nematode control in bananas. Fenamiphos is applied manually in granular formulations (Nemacur 15G) at a dose of 30 kg product/ha. Applications are generally made once or twice a year, which depends on the degree of infestation. It is a highly toxic compound (e.g. LC50 for rainbow trout = 0.0721 mg/L) and has a water solubility of 700 mg/L (Kidd and James 1991). Fenamiphos is of moderate persistence in soil, with a reported half-life of about 50 days in soil (Wauchope et al. 1992; Kookana et al. 1997). It can be oxidised into its sulfoxide and sulfone metabolites in soil without losing its nematicidal properties (Ou and Rao 1986; Kookana et al. 1997). Singh et al. (1990) studied the sorption of fenamiphos in 4 Western Australian soils and found that it was moderately sorbed onto the soils. Data on fenamiphos metabolites are meagre. Chlorothalonil of technical grade with a purity of 99% was obtained from Chem Service Australia. The technical grade fenamiphos (94.6% pure), fenamiphos sulfoxide (98% pure), and fenamiphos sulfone (98% pure) were obtained from Chem Service Pennsylvania, USA. Acetonitrile, hexane, and toluene of HPLC grade were obtained from BDH, England. Pesticide stock solutions were prepared at a concentration of 100 mg/L in acetonitrile. Soils Seven soils were collected from a depth of 0–15 cm from the banana production area in the Guayas River Basin of Ecuador (Table 1). The taxonomical description of these soils was obtained from ORSTOM (1982, 1984). The soils were air-dried at room temperature and passed through a 2-mm sieve and immediately sent to Australia for this study. Soil pH was measured in a 1:5 w/v soil to water solution using a pH meter, while soil organic carbon was determined by a LECO Carbon and Nitrogen Analyzer. Soil particle size

Sorption of pesticides on Ecuadorean soils

Table 1. Soil no.

1087

Selected physiochemical properties of the soils used in the study from the Guayas River Basin, Ecuador Location

1

Nueva Colonia, Yaguachi

2 3 4 5 6

Santa Ana, Naranjal La Paz, El Triunfo Cristal, Quevedo Vanoni, Quevedo Monte de Oro, Machala

Soil TaxonomyA

HapludollsFluventic Europepts Ustipsamments Vertic Ustropepts AndicEutropept Kanhapludalf Tropofluvents

pH (water)

Organic carbon (%)

Clay (%)

Silt (%)

Fine sand (%)

Coarse sand (%)

6.79

2.8

41.5

40.6

13.9

5.5

7.42 7.26 7.11 7.05 6.38

3.5 1.1 3.0 3.6 3.2

42.9 23.9 23.3 21.1 44.4

34.6 29.0 25.9 30.5 27.4

21.5 43.4 50.7 47.1 27.6

1.1 5.9 1.5 1.5 0.0

A

Taxonomical classification was obtained from ORSTOM 1982, 1984.

distribution was analysed by using the pipette method (USDA 1996). The soils were in storage for less than 2 months prior to the following sorption studies. Sorption test The sorption of chlorothalonil, fenamiphos, fenamiphos sulfoxide, and fenamiphos sulfone on the Ecuadorian soils was studied in Australia, essentially following a standard protocol (USEPA 1998). Sorption was measured at room temperature by a batch equilibration method, initially against a single solution concentration. Pesticide solutions were all prepared in 0.01 M CaCl2. Due to the low water solubility of chlorothalonil (0.6 mg/L), 1% acetonitrile (ACN) was added to the solution as a co-solvent. The solutions of chlorothalonil, fenamiphos, fenamiphos sulfoxidem, and fenamiphos sulfone were prepared at varying concentrations in 0.01 M CaCl2. For single-point sorption measurement, the solution concentrations used for chlorothalonil, fenamiphos, fenamiphos sulfoxide, and fenamiphos sulfone were 10, 4, 2 and 2 mg/L in 0.01 M CaCl2, respectively. One gram of soil was weighed into each polypropylene tube and then 5 mL each of the pesticide solutions was added. Blanks without soils indicated no significant sorption loss on tube walls. The soil solutions were equilibrated by shaking in a mechanical shaker for 16 h. After equilibration, the tubes were centrifuged at 1200 rpm (rcf. = 470G) for 20 min. For chlorothalonil analyses, 3 mL of the supernatant was taken from each tube and extracted with 1 mL of hexane and 2 mL of toluene by shaking in a Vortex for 1 min. The extracts were analysed by gas chromatography. For fenamiphos and its metabolites, the supernatants from test tubes were directly analysed by high performance liquid chromatography (HPLC). Method details are given in a later section. All tests were done in duplicate. The effect of the co-solvent, acetonitrile, on sorption of chlorothalonil was investigated by using different percentages of acetonitrile (1, 5, 10, 20, and 30%) in the chlorothalonil solutions, using the experimental conditions for single-point sorption test. To assess the validity of using a single concentration for determining sorption coefficients, sorption isotherms for the 4 compounds were measured on 3 soils (Nueva Colonia, Yaguachi, and Cristal, Quevedo). The soils were selected to cover a range of soil organic matter and clay contents (Table 1). Five chlorothalonil concentrations (2, 4, 6, 8, and 10 mg/L) were employed in the test. For fenamiphos and its 2 metabolites, 4 solution concentrations (2, 3, 4, 5 mg/L) were used. The other experimental conditions were the same as the single-point sorption test. Residue analysis The extracts for chlorothalonil were analysed by an Auto-system Perkin-Elmer gas chromatogram with an electron capture detector (GC-ECD). The instrument was equipped with a J & W Scientific DB-5 column (30 m by 0.25 µm i.d., 0.25-µm film thickness). Its injector temperature was set at 280°C and the detector temperature was 300°C. The oven was programmed from 180°C (hold for 2 min) to 230°C (hold for 1 min) at 6°C/min. Helium was used as carrier gas at 2.4 mL/min with the split vent flow at 100 mL/min. High purity nitrogen gas (N2) was used as make-up gas at 40 mL/min. Data were processed by an on-line computer using Turbochrom 4 software. Fenamiphos and its sulfoxide and sulfone metabolites were analysed using a Varian liquid chromatograph (HPLC) equipped with a polychrom diode array (PDA) UV detector (Model 9065), a pump

1088

T. Cáceres et al.

60

Soil 1

40 y = 71.11x + 9.64

Concentration in soil (mg/kg)

20

R 2 = 0.99

0 0 50

0.2

0.6

0.4

Soil 4

40 30 20

Fig. 1. Linear plots of sorption data for chlorothalonil on three soils measured by batch method in the presence of 1% acetonitrile in water.

y = 49.56x − 2.12 R 2 = 0.93

10 0 0 60

0.2

0.4

0.6

0.8

1

Soil 6

40 y = 82.65x + 6.68 R 2 = 0.98

20 0 0

0.1

0.2

0.3

0.4

0.5

0.6

Concentration in solution (mg/L)

(Varian 9012), and a Star Chromatography Workstation for processing data. The wavelength of 210 nm was used to quantify the response for fenamiphos and its metabolites, which were separated on an SGE SSWakosil C18 AR column (100 by 4.6 mm, 5 mm) at a flow rate of 1 mL/min. A gradient mobile phase was used: 20% acetonitrile/80% Milli-Q water at 0 min to 40% acetonitrile/60% Milli-Q water at 20 min. Determination of sorption coefficient The sorption coefficient (Kd) was determined using the ratio of the concentration of pesticide sorbed by the soil (mg/kg) to the equilibrium solution concentration (mg/L). Kd (L/kg) was normalised on the basis of organic carbon content, to obtain Koc (Koc = Kd/fraction of organic carbon).

Results Chlorothalonil sorption The sorption isotherms for chlorothalonil in the 3 soils used in the study were found to be linear over the concentrations used in the test (Fig. 1), with R2 values of 0.99, 0.93, and 0.98 for soils 1, 4, and 6, respectively. This means that the sorption coefficient (Kd) is independent of the solution concentration and the use of single-point sorption measurement for calculating Kd was justified in the present study. For a generalised assessment of off-site migration potential of pesticides, single-point estimates of Kd were more than adequate. The sorption coefficients Kd of chlorothalonil based on single-point measurement in the 6 Ecuadorean soils varied from 68.50 to 152.60 kg/L (Table 2), showing a moderate to high sorption on these soils. Chlorothalonil had relatively lower Kd values on soils 3, 4, and 5, which ranged between 68.50 and 74.03 L/kg. Due to the low water solubility of chlorothalonil, stock solutions made in acetonitrile were used in sorption test resulting in the presence of 1% acetonitrile as a co-solvent in the above sorption tests. There was a possibility that sorption was influenced by the presence of co-solvent and therefore was underestimated. The sorption coefficients in aqueous solution were obtained by extrapolation using sorption data obtained at different fractions of acetonitrile in water, using the ‘Solvophobic Theory’ (Horvath and Melander 1983).


Table 2.

A

1089

Sorption coefficients (Kd, L/kg) of chlorothalonil, fenamiphos, and its two metabolites (± s.e.)

Soil

ChlorothalonilA

Fenamiphos

Fenamiphos sulfoxide

Fenamiphos sulfone

1 2 3 4 5 6

152.60 ± 29.06 123.28 ± 2.170 074.03 ± 7.140 068.50 ± 5.400 069.37 ± 3.890 108.42 ± 0.120

10.77 ± 0.26 12.75 ± 0.15 05.66 ± 0.18 08.94 ± 0.02 07.91 ± 0.33 14.31 ± 2.56

1.79 ± 0.03 2.47 ± 0.09 1.55 ± 0.11 0.77 ± 0.04 1.06 ± 0.13 4.00 ± 0.00

5.28 ± 0.35 6.20 ± 0.10 3.67 ± 0.14 2.81 ± 0.12 2.83 ± 0.14 8.79 ± 0.11

The Kd values were measured in 1% acetonitrile solutions. Table 3.

Relationship between measured Kd values of chlorothalonil and percentages of acetonitrile in binary solutions

Soil

log Kd v. % co-solvent

R2

Calculated Kd in aqueous solution (L/kg)

Koc (Kd/fraction organic carbon)

1 2 3 4 5 6

y = –0.048x + 2.149 y = –0.044x + 2.058 y = –0.042x + 1.907 y = –0.040x + 1.873 y = –0.041x + 1.924 y = –0.050x + 2.066

0.97 0.97 0.97 0.98 0.97 0.90

140.83 114.16 080.70 074.59 083.89 116.28

5029 3262 7336 2486 2330 3633

Other workers have previously used this method (Nkedi-Kizza et al. 1985; Kookana et al. 1990; Ying and Kookana 2001). It was found that the measured Kd values had a semi-log relation with percentage of co-solvent in solution (Table 3). The calculated Kd value for chlorothalonil in aqueous solution (Table 3) ranged from 74.59 L/kg for soil 4 to 140.83 L/kg for soil 1, which is similar to the Kd values measured in 1% acetonitrile (Table 2, Fig. 2). A plot of Kd values for 6 soils measured in the presence of 1% acetonitrile against those extrapolated using the regression equations (Table 3) in Fig. 2 shows that these are comparable. Therefore, the Kd values measured in 1% acetonitrile/water can represent the sorption occurring in aqueous solution reasonably well. The normalised sorption coefficients (Koc) of chlorothalonil on the soils ranged between 2330 and 7336 kg/L with an average value of 4012 kg/L. Fenamiphos and its metabolites The sorption isotherms for fenamiphos and its metabolites have been presented in Figs 3, 4, and 5. Isotherm linearity over the concentrations used was observed in all cases, except for fenamiphos sulfoxide on soils 1 and 4, which tended to follow ‘S’ shapes. The sorption coefficients determined for fenamiphos and its metabolites are presented in Table 2. The Kd values for the 6 Ecuadorean soils ranged from 5.66 to 14.31 L/kg for fenamiphos, from 0.77 to 4.00 L/kg for fenamiphos sulfoxide, and from 2.81 to 8.79 L/kg for fenamiphos sulfone, respectively. These values showed a weak to moderate sorption of fenamiphos and its metabolites on the soils. The sorption affinity of the 3 compounds for any given soils was as follows: fenamiphos > fenamiphos sulfone > fenamiphos sulfoxide. The sorption of fenamipohos and its metabolites on soils 3, 4, and 5 was relatively weaker than on soils 1, 2, and 6. The trend was similar to that observed for chlorothalonil.

1090

T. Cáceres et al.

Extrapolated Kd (aqueous solution)

180 160 140 120 100 80 60 40 20 0 0

50

100

150

Measured Kd (1% acetonitrile)

Fig. 2. A comparison of sorption coefficient (Kd) values measured in the presence of 1% acetonitrile in water with those calculated using solvophobic theory.

The organic carbon sorption coefficients (Koc) for the 6 soils were calculated to range between 220 and 515 kg/L with an average value of 371 kg/L for fenamiphos, between 29 and 141 kg/L with an average value of 76 kg/L for fenamiphos sulfoxide, and between 79 and 334 kg/L with an average value of 191 kg/L for fenamiphos sulfone. Discussion The sorption of pesticides on soils is dependent on the properties of soil, such as type and content of organic carbon and clay and in some cases on soil pH value (Walker and Crawford 1968; Graham-Bryce 1981; Loch 1991; Kookana et al. 1998; Ying and Kookana 20

Soil 1

15 10 y = 7.31x + 0.62


5

R 2 = 0.98

0 0 20

0.5

1

1.5

2

2.5

Soil 4

15 10

Fig. 3. Linear plots of sorption data for fenamiphos on three soils measured by batch method from aqueous solutions.

y = 7.80x − 0.60

5

R

2

= 1.00

0 0 20

0.5

1

1.5

2

2.5

Soil 6

15 10

y = 14.20x − 3.93 R 2 = 0.95

5 0 0

0.5

1

1.5


2


1091

Soil 1

15 10

y = 5.40x − 3.85 R 2 = 0.84


5 0 0

1

2

3

Soil 4

12 10 8 6 4 2 0

y = 4.81x − 5.97 R 2 = 0.76 0

15

1

2

4

3

Fig. 4. Linear plots of sorption data for fenamiphos sulfoxide on three soils measured by batch method from aqueous solutions.

Soil 6

10 y = 7.20x − 3.28 R 2 = 0.97

5 0 0

0.5

1

1.5

2

2.5


2001; Ahmad et al. 2001). The 4 compounds exhibited higher sorption in soils 1, 2, and 6 than in the soils 3, 4, and 5. The 6 soils used in the study had relatively high organic carbon contents (2.8–3.6%) except soil 3 (1.1%) (Table 1). Although soils 4 and 5 had comparable organic carbon contents to soils 1, 2, and 6, the sorption of the 4 chemicals on these 2 soils was much smaller. Clearly organic carbon content alone cannot describe the observed variation in sorption. However, clays appear to have also contributed to chemical sorption Soil 1

15 10

y = 3.93x + 1.14


5 0

R 2 = 0.97 0

10

1

2

3

Soil 4

8 6

Fig. 5. Linear plots of sorption data for fenamiphos sulfone on three soils measured by batch method from aqueous solutions.

y = 2.93x − 0.18

4

R

2

2

= 0.99

0 0

1

2

3

4

Soil 6

20 15 10

y = 6.12x + 1.43

5

R 2 = 0.97

0 0

0.5

1

1.5

2


2.5

1092

T. Cáceres et al.

in these Ecuadorean soils. The clay contents of soils 1, 2, and 6 were higher (ranging from 41.5 to 44.4%) than those for the other 3 soils (ranging from 21.1 to 23.9%). The mineralogical composition of clays through XRD revealed that all soils, except soil 5, were rich in smectite, with kaolin as a minor fraction. In the soil from Vanoni, Quevedo (soil 5), amorphous materials dominated, with smectite and albite as minor fraction. The combined contribution of organic matter and clays in the soils 1, 2, and 6 may explain the higher sorption in soils 1, 2, and 6. The nature of soil organic matter can also play a significant role in pesticide sorption (Ahmad et al. 2001). We believe that pH values had little effect on the sorption of the 4 pesticides in the present study. Soil pH is not expected to affect the sorption of non-ionic pesticides such as chlorothalonil and fenamiphos. Only ionic or ionisable (weak acidic and basic) pesticides are influenced by soil pH variations (Graham-Bryce 1981; Loch 1991). Furthermore, the pH values of the 6 soils were in a narrow range (6.38–7.42). The Koc values of chlorothalonil observed in the present study (2330–7336 kg/L, mean 4012 kg/L) on the 6 soils are all higher than those previously reported in the literature. For example, the database of Hornsby et al. (1996) recorded a Koc value of 1380, whereas Kawamoto and Urano (1989) reported a Koc value of 1820. For fenamiphos, while a Koc of 100 was reported by Hornsby et al. (1996), in a recent study on 23 soils from Western Australia, Kookana et al. (2001) found a mean value of Koc for fenamiphos to be 495 ± 492 (s.d.). In the same study, wide variations of Koc for the metabolites were observed. Such variations in Koc values are quite common in the literature and most likely reflect the heterogeneity in soil organic matter composition in soils from different countries (Ahmad et al. 2001). The other reason is that soil constituents other than organic carbon can also play a role in pesticide sorption. Practical implications of the findings The movement of pesticides from the target area through runoff and leaching into surface and ground waters is of concern due to the significant use of pesticides in banana plantations in Ecuador. The 4 chemicals studied here are very toxic to mammals and fish and other aquatic species (Kidd and James 1991). Due to the high sorption affinity of chlorothalonil on these soils, there is little risk of its leaching into groundwater. This is in agreement with the results of Winnett et al. (1990). However, chlorothalonil may migrate with soil or sediment by surface runoff and may cause contamination of surface water. Fenamiphos and its sulfoxide and sulfone metabolites are more mobile than chlorothalonil owing to their weaker sorption on soils. The metabolites of fenamiphos had lower Kd values, and thus are more mobile than their parent compound in soil. Both fenamiphos sulfoxide and fenamiphos sulfone will leach more easily than fenamiphos (Loffredo et al. 1991). Schneider et al. (1990) studied field movement and persistence of fenamiphos in drip-irrigated pineapple soils and found high concentrations of fenamiphos at 3 m depth from the root-zone. Fenamiphos is known to rapidly oxidise to the 2 metabolites, which were found to be more persistent that the parent compound in studies reported by Ou and Rao (1986) and Kookana et al. (1997). These studies also showed that fenamiphos sulfoxide was the main metabolite in soils. Given the lower sorption and longer persistence of fenamiphos sulfoxide in soils, this metabolite can potentially migrate to the surface and ground waters near banana plantations in Ecuador. Ammati and Mansour (1994) evaluated the mobility of fenamiphos and its metabolites using non-disturbed soil columns cropped with bananas, and found fenamiphos and its metabolites in the leachates.


1093

In terms of practical implications the study shows that off-site migration of chlorothalonil will be mainly thorough colloid transport or spray drift from the plantations. Clearly the loss is likely to be greater in areas prone to erosion losses. The risk of its movement in the dissolved phase (i.e. runoff water) is relatively low. In monitoring studies, care needs to be exercised as the residue of chlorothalonil on colloids may be excluded during filtration of the samples. For fenamiphos, both pathways (runoff water and colloidal transport) are important. The metabolites of fenamiphos have the greatest potential of migration in runoff water. Also from the point of view of groundwater contamination, the 2 metabolites of fenamiphos would present much greater risk than the parent compound. It is recommended that the 2 metabolites of fenamiphos be included in the monitoring studies and further assessments of off-site migration potential of pesticides in Ecuador. Acknowledgments This study was sponsored by the International Atomic Energy Agency (TCP ECU/5/021) in collaboration with CSIRO Land and Water and the Ecuadorean Atomic Energy Commission (Environmental Toxicology Division). The senior author, Miss Tanya Cáceres, conducted this study while on training at CSIRO Land and Water, Adelaide. We gratefully acknowledge the contributions by Yolanda Pástor and Ing. Julio Molineros of Ecuadorean Atomic Energy Commission, and by Dr Ian Ferris of International Atomic Energy Agency, for their support in these studies. Drs Ray Correll, Zuliang Chen, and M. Megharaj provided helpful assistance during Tanya’s training. Dr N. Singh and Ms Danni Oliver provided useful comments on this manuscript. We wish to thank Mr Richard Merry for his help with soil taxonomy. References Ahmad R, Kookana RS, Alston AM, Skjemstad JO (2001) The nature of soil organic matter affects sorption of pesticides. 1. Relationships with carbon chemistry as determined by 13C CPMAS NMR spectroscopy. Environmental Science and Technology 35, 878–884. Ammati M, Mansour M (1994) Movement of fenamiphos through non-disturbed soil columns. Fresenius Environmental Bulletin 3, 212–219. Brown SL, Rachman NJ (1996) Risk-based priorities for pesticide management initiatives. Chemosphere 33, 1355–1368. Castillo LE, Ruepert C, Silos E (1998) Pesticides in surface waters in areas influenced by banana production in Costa Rica. Report of a final Research Co-ordination Meeting organized by the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Panama City, Panama, 1998. Graham-Bryce IJ (1981) The behaviour of pesticides in soil. In ‘The Chemistry of soil processes’. (Eds DJ Greenland, MHB Hayes) pp. 621–670. (John Wiley and Sons Ltd: New York) Hornsby AG, Wauchope RD, Herner AE (1996) ‘Pesticide properties in the environment’. (Springer Verlag: New York) Horvath CS, Melander WR (1983) Theory of chromatography. In ‘Chromatography: Part A, Fundamentals and techniques’. (Ed. E Heftmann) pp. A27–A135. (Elsevier: Orinda, CA) Katayama A, Isemura H, Kuwatsuka S (1991) Suppression of chlorothalonil dissipation in soil by repeated applications. Journal of Pesticide Science 16, 233–238. Katayama A, Mori T, Kuwatsuka S (1995) Abiotic dissipation of chlorothalonil in soil accelerated by amendment with high applications of farmyard manure. Soil Biology and Biochemistry 27, 147–151. Kawamoto K, Urano K (1989) Parameters for predicting fate of organochlorine pesticides in the environment. (II) Adsorption constant to soil. Chemosphere 19, 1223–1231. Kidd H, James DR (Ed.) (1991) ‘The agrochemicals handbook.’ 3rd edn. pp. 6–10. (Royal Society of Chemistry Information Services: Cambridge, UK) Kookana RS, Baskaran S, Naidu R (1998) Pesticide fate and behaviour in Australian soils in relation to contamination and management of soil and water: a review. Australian Journal of Soil Research 36, 715–764.

1094

T. Cáceres et al.

Kookana RS, Gerritse RG, Aylmore LAG (1990) Effect of organic cosolvent on adsorption and desorption of linuron and simazine in soil. Ausralian Journal of Soil Research 28, 717–725. Kookana RS, Kerekes A, Oliver D, Salama RB, Byrne JD (2001) Sorption of selected pesticides and their metabolites in soil profiles of the Swan Coastal Plain. In ‘Proceedings of Conference on Agrochemical Pollution of Water Resources’. Hat Yai, Thailand, 16–18 Feb. 2000. Australian Centre for International Agricultural Research Proceedings No. 104. pp. 118–124. (ACIAR: Canberra) Kookana RS, Phang C, Aylmore LAG (1997) Transformation and degradation of fenamiphos nematicide and its metabolites in soils. Australian Journal of Soil Research 35, 753–761. Koskinen WC, Harper J (1990) The retention process: mechanisms. In ‘Pesticides in the soil environment: process, impacts and modelling’. (Ed. HH Cheng) pp. 51–77. (Soil Science Society of America: Madison, WI) Loch JPG (1991) Effect of soil type on pesticides threat to the soil/groundwater environment. In ‘Chemistry, agriculture and the environment’. (Ed. ML Richardson) pp. 291–307. (The Royal Society of Chemistry: UK) Loffredo E, Senesi N, Melillo VA, Lamberti F (1991) Leaching of fenamiphos, fenamiphos sulfoxide and fenamiphos sulfone in soil columns. Journal of Environmental Science and Health (Part B) 26, 99–113. Nkedi-Kizza P, Rao PSC, Hornsby AG (1985) Influence of organic cosolvent on sorption of hydrophosbic chemicals by soil. Environmental Science and Technology 19, 975–979. ORSTOM (1982) Mapa Morfo Pedológico. Hoja Machala, Quevedo. Escala 1:200000 Office de la Recherche Scientifique Et Technique Outer-Mer. Acuerdo Mag-ORSTOM. 1982. ORSTOM (1984) Mapa Morfo Pedológico. Hoja Guayaquil. Escala 1:200000. Office de la Recherche Scientifique Et Technique Outer-Mer. Acuerdo Mag-ORSTOM. 1984. Ou L-T, Rao PSC (1986) Degradation and metabolism of oxamyl and phenamiphos in soils. Journal of Environmental Science and Health B 21, 25–40. Peñuela GA, Barceló D (1998) Photodegradation and stability of chlorothalonil in water studied by solid-phase disk extraction, followed by gas chromatographic techniques. Journal of Chromatography A 823, 81–90. Sato K, Tanaka H (1987) Degradation and metabolism of a fungicide, 2,4,5,6-tetra-chloroisophthalonitrile (TPN) in soil. Biology and Fertility of Soils 3, 205–209. Schneider RC, Green RE, Apt WJ, Bartholomew DP, Caswell EP (1990) Field movement and persistence of fenamiphos in drip-irrigated pineapple soils. Pesticide Science 30, 243–257. Singh R, Gerritse RG, Aylmore LAG (1990) Adsorption-desorption of selected pesticides in some Western Australian soils. Australian Journal of Soil Research 28, 227–243. Stover RH, Simmonds NH (1987) ‘Bananas.’ (John Wiley and Sons: New York) Szalkowski MB, Stallard, DE (1977) Effect of pH on the hydrolysis of chlorothalonil. Journal of Agricultural and Food Chemistry 25, 208–210. Takagi K, Wada H, Yamazaki S (1991) Effect of long-term application of a fungicide, chlorothalonil (TPN) on upland ecosystem. Soil Science and Plant Nutrition 37, 583–590. USDA (1996) Soil Survey laboratory Methods Manual. Soil Survey Investigations Report No. 42, version 3.0, pp. 55–56. USEPA (1998) Fate, Transport and Transformation Test Guidelines. OPPTS 835.1220. Sediment and Soil Adsorption and Desorption Isotherms. EPA 712-C-98-048. Vincent PG, Sisler HD (1968) Antifungal action of 2,4,5,6-tetrachloroisophthalonitrile. Physiologia Plantarum 21, 1249–1264. Walker A, Crawford D (1968) The role of organic matter in adsorption of the triazine herbicides by soil. In ‘Isotopes and radiation in soil organic matter studies’. pp. 91–108. (IAEA: Vienna) Wauchope RD, Buttler TM, Hornsby AG, Augustijn-Beckers PW, Burt JP (1992) SCS/ARS/CES Pesticide properties database for environmental decision-making. Review of Environmental Contamination and Toxicology 123, 1–164. Winnett G, Marucci P, Reduker S, Uchrin CG (1990) The fate of chlorothalonil in ground water in commercial cranberry culture in the New Jersey Pine Barrens. Journal of Environmental Science and Health A25, 587–595. Ying GG, Kookana RS (2001) Sorption of fipronil and its metabolites on soils from South Australia. Journal of Environmental Science and Health B36, 545–558.

Manuscript received 23 January 2002, accepted 30 May 2002 http://www.publish.csiro.au/journals/ajsr