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Controlled release of CuSO4· H2O for the control of schistosomiasis — A field study
Journal of Controlled Release, 4 (1987) 279-282 Elsevier Science Publishers B.V., Amsterdam -Printed
279
in The Netherlands
CONTROLLED RELEASE OF CuSO,*H,O A FIELD STUDY
FOR THE CONTROL OF SCHISTOSOMIASIS
-
F.M. Helaly and M.H. Nosseir Polymer
and Pigment
(Received
July
Laboratory,
8, 1985;
accepted
National
Research Centre,
in revised form
July
Dokki,
Cairo (Egypt)
15, 1986)
It is known that controlled release techniques can be used to kill snails which are the intermediate host of schistosomiasis [I, 21, and for this reason field trials were performed [3]. Thus, it was of interest to study parameters which affect the lethal time and lethal dose which are known to be effective for snail control. It was found that the depth of water affects the spreading of copper ions which in turn affects both the LT,,, and LCIOO of snails.
INTRODUCTION
MATERIALS
Controlled release techniques can be used to destroy snails which are the intermediate host of schistosomiasis. The technique depends on regulating the release of the bioactive material CuSO, *H20 from a rubber matrix in the form of discs distributed in water streams infected with the snails. The aim of the present work was to evaluate controlled release formulations containing CuSO, *HZ0 and to demonstrate the potential of using a molluscidal formulation for controlling snails. The test consisted of application of controlled release molluscides in the field, and the evaluation was based on snail mortality as determined by periodic survey of the treated habitat. Field evaluation is necessary in order to adjudge the feasibility of the use of the controlled release materials as molluscides.
1. Materials
0168-3659/87/$03.50
0 1987
Elsevier
Science
AND EXPERIMENTAL
TECHNIQUES
The following materials were used: Styrene-butadiene rubber (SBR 1502); highabrasion furnace black (HAF), having a surface area of 80 m*/g; sulphur, tetramethylthioram disulphide (TMTD), zinc oxide, mercaptobenzothiazole (MBT), stearic acid, phenyl+naphthylamine (PBN), all of the types normally used in industry; copper sulphate monohydrate (M.W. 177.69, maximum particle size 125 pm), prepared from copper sulphate pentahydrate; and ammonium sulphate. Field tests were performed on a piece of land in the agricultural experimental station of the National Research Centre in Shalakan, 4 km northwest of the Delta Barrage in Qualubia Governorate.
Publishers
B.V.
280
Twenty thousand Bolinus and Biomphalaria alexandrina snails were used for each 10 m length of canal. The constituents of nature are mud and weed plants growing in the streams.
2. Experimental Preparation
techniques of slow release styrene-butadiene
rubber formulation
for field
use
Compounding and mixing were performed in a large-scale mixer (Buzuiuk Komarova NAR-Bodink, Komarova Horovic MTS, Vyrobinicisllo ‘7168, Type Strong 14240/P3, Rokvyroby 1967/l). The blend was made into 4 mm thick sheets and cut into rectangles of 170 X 60 cm. The sheets were vulcanized [4] at 143 + 2°C for 30 min in an autoclave (Skoda, Hradec Kralove, Czechoslovakia). After vulcanization, the sheets were cut with an electrical knife into small squares having average dimensions of 2 X 2 cm and 0.4 cm thickness. The formulation used was: SBR (loo), HAF (50), ZnO (3), S (l), MBT (l), TMTD (l), PBN (l), stearic acid (O.l), (NH&SO‘, (2), CuSO, *Hz0 (157.5).
Construction
of the canals for field tests
Six irrigation canals were constructed, three having a length of 30 m and widths of 2 m and 1.5 m at the upper surface and the bottom, respectively. The depth of the canals was about 1 m, and the canals were fed from a larger stream connected to the El-Bassosia canal. The draining canal was similar to the feeding stream, with a concrete base of 10 cm thickness, and brick walls of 25 cm thickness for the lower part of 45 cm height, and of 12.5 cm thickness for the upper part, with a total height of 1 m. Each canal was provided with inlet and outlet water openings. The other three canals had the same construction but differed in length and width (10.5 m length and widths of 1.5 m and 0.5 m at the upper surface and at the bottom, respectively). Figure 1 illustrates the canals.
Fig. 1. A graphical representation of one of the small irrigation canals constructed. Scale 1:300; all dimensions in centimeters.
Leaching
rate test [5, 61
The concentration of copper ions leached into the water of the canals was determined using the carbamate method. Thus, 20 ml of the leaching solution was transferred into a 250 ml separatory funnel, and then 2 ml of 20% citric acid solution, 2 ml 10% ammonium hydroxide solution and 2 ml 0.1% carbamate reagent solution were added. The yellow copper complex was extracted with an accurately measured amout of 10 ml carbon tetrachloride. Using a copper calibration curve [7] the leaching rate was calculated using the following equation: Leaching rate (pg/l) = F X D X 50 where F is the factor calculated from the calibration curve 33.3 [7] at X = 440 nm, and D is the optical density.
RESULTS
Effect
AND
DISCUSSION
of concentration
butadiene
of controlled
rubber formulation
release styrene-
on leaching
rate
The field tests were carried out during the months of May, June, and July, 1984. At the beginning of the experiment, the concentrations of copper ions in the water and in the
281
was relatively constant after a soaking period of 40 days, and these concentrations were very effective in achieving 100% mortality of snails. The above data suggest that LC,,, (the concentration at which 100% mortality occurs) is 116 r.lg/l, which is the minimum concentration for killing most snails. The LT,,, (the time at which 100% mortality occurs) increased by decreasing the concentration of the molluscides used, as shown in Fig. 3. Samples of mud from the bottom were also taken from the treated and untreated canals in order to determine adsorbed Cu? Results are shown in Table 1.
surface mud were 36-44 pg/l and 46-48 pug/g mud, respectively. The level of water was 50-60 cm and remained unchanged during the experiment, pH was 7.2-7.5, and the temperature was 24-27°C. The concentrations of rubber formulation containing CuS04 *Hz0 used were 1, 2, 4, and 6 kg/m3 in canals No. 1, 3, 4, and 6, respectively, leaving canals No. 2 and 5 without treatment as control. The leaching rate of copper ions in a canal containing clear water is shown in Fig. 2. The concentration of copper ions released into the water increases with increasing dose of the molluscide distributed in the streams. The concentration of copper ions in canals No. 1 and 3 was lower than those in canals No. 4 and 6 after an initial immersion of 6 days. After a further 20 days exposure, the concentrations of copper ions in canals No. 1, 3, 4, and 6 became 116,128,183, and 224 pg/l, respectively. These concentrations were found to be adequate to kill the Bolinus and Biomphalaria alexandrina snails which were used to test the efficacy of the controlled release molluscides. In canals No. 2 and 5 the concentration of copper ions remained unchanged at 44 pg/l. The rate of Cu” leached
zl
h
40-
.
20 -
0
[So 0
20
40
, Fig. 3. A graphical tion of LC,,,.
01
0
’ VJ
fi 20
30
00
so
60
,o
80 90 Time (days
)
100
Fig. 2. Effect of concentration of molluscide formulations on leaching rate. Key: 0: canals No. 2, 5, concentration of molluscide 0 kg/m3 (control); 0: canal No. 1, concentration 1 kg/m3; x : canal No. 3, conA: canal No. 4, concentration 4 centration 2 kg/m’; kg/m3;. : canal No. 6, concentration 6 kg/m3.
J
60
_
80
%o 100 _
representation
%Xl 120
140
160
of the determina-
In Table 1 it can be seen that the average copper ion concentrations in the surface mud were 98, 104, 110, and 114 pg/g dry mud after 20 days of exposure in canals No. 1, 3, 4, and 6, respectively, while the average copper ion concentration in canals No. 2 and 5 was still between 46 and 50 pg/g mud. These amounts of copper ions were relatively constant during the whole experiment. Therefore, the mortality rate of snails depends on the amount of copper ions released into the water and is not affected by copper ions adsorbed on the surface of the mud at the bottom and at the sides of the canals.
282 TABLE 1 CU*+ adsorbed on mud on the bottom Canal No.
1 2 3 4 5 6
of both treated and untreated
canals
Concentration of molluscide added (kg/m’)
Concentration of Cu’+ adsorbed on mud (pg/g) after soaking period of 0 days
10 days
20 days
1 0 2 4 0 6
46-48
61 47 68 76 46 78
98 48 104 110 48 114
40 days 98 48 115 115 50 120
100 days 104 48 98 110 48 118
TABLE 2 Effect of water level on concentration tration of molluscide added 2 kg/m3 Exp. No.
1 2 3
Level of Hz0 (cm)
20-25 30-40 50-60
of copper ions leached into clear water; concen-
Leached copper ions in clear water (pg/l) 0 days
3 days
5 days
10 days
15 days
20 days
36-44
66 52 52
98 96 86
186 111 96
225 198 102
246 125 116
Effect of water depth on copper ion concentrations
A study of the effect of the level of water on concentration of copper ions leached into water under environmental conditions is necessary in order to determine the molluscidal dose which is suitable for each level. Levels of water, and times of exposure at 25-27”C, are shown in Table 2. From Table 2, it can be observed that the concentration of molluscides under test (2 kg/m3) gave average concentrations of 66, 52, and 52 pg/l after an initial immersion of 3 days in experiments No. 1, 2, and 3, respectively. Also, it was shown that the concentration of Cu2’ increased in time but differs with the level of water. It is apparent, therefore, that at higher levels of water a higher dose of controlled release rubber formulation is required to obtain 100% mortality of snails within a suitable time. Also, concentration of Cu2’ in water was affected by the depth of water.
From results obtained in this study, it is concluded that this controlled release technique is an effective means for controlling snails and that it can be applied at any time of the year. REFERENCES
N.F. Cardarelli, Controlled Release Pesticide Formulations, CRC Press, Cleveland, OH, 1976, p. 20-25,28, 53-55,102. S.V. Kanakkanatt, Schistosomiasis control by slow release molluscides, Product Development Laboratory Report, University of Akron, OH, Sept. 15,1972. F.M. Helaly and M.H. Nosseir, Evaluation of controlled release styrenebutadiene rubber formulation containing copper sulphate monohydrate as molluscicides under small field conditions, Ind. J. Technol., in press. ASTM Designation, D 15-66 T, 1967. A. Parington, Paint Technol., 27( 3) (1963) 17. F. Marson, J.Oil Colour Chem. Assoc., 47 (1964) 323. N.A. Ghanem and M.M. Abd El-Malek, J. Chem. Arab Republic Egypt, 9 (1966) 377.
279
in The Netherlands
CONTROLLED RELEASE OF CuSO,*H,O A FIELD STUDY
FOR THE CONTROL OF SCHISTOSOMIASIS
-
F.M. Helaly and M.H. Nosseir Polymer
and Pigment
(Received
July
Laboratory,
8, 1985;
accepted
National
Research Centre,
in revised form
July
Dokki,
Cairo (Egypt)
15, 1986)
It is known that controlled release techniques can be used to kill snails which are the intermediate host of schistosomiasis [I, 21, and for this reason field trials were performed [3]. Thus, it was of interest to study parameters which affect the lethal time and lethal dose which are known to be effective for snail control. It was found that the depth of water affects the spreading of copper ions which in turn affects both the LT,,, and LCIOO of snails.
INTRODUCTION
MATERIALS
Controlled release techniques can be used to destroy snails which are the intermediate host of schistosomiasis. The technique depends on regulating the release of the bioactive material CuSO, *H20 from a rubber matrix in the form of discs distributed in water streams infected with the snails. The aim of the present work was to evaluate controlled release formulations containing CuSO, *HZ0 and to demonstrate the potential of using a molluscidal formulation for controlling snails. The test consisted of application of controlled release molluscides in the field, and the evaluation was based on snail mortality as determined by periodic survey of the treated habitat. Field evaluation is necessary in order to adjudge the feasibility of the use of the controlled release materials as molluscides.
1. Materials
0168-3659/87/$03.50
0 1987
Elsevier
Science
AND EXPERIMENTAL
TECHNIQUES
The following materials were used: Styrene-butadiene rubber (SBR 1502); highabrasion furnace black (HAF), having a surface area of 80 m*/g; sulphur, tetramethylthioram disulphide (TMTD), zinc oxide, mercaptobenzothiazole (MBT), stearic acid, phenyl+naphthylamine (PBN), all of the types normally used in industry; copper sulphate monohydrate (M.W. 177.69, maximum particle size 125 pm), prepared from copper sulphate pentahydrate; and ammonium sulphate. Field tests were performed on a piece of land in the agricultural experimental station of the National Research Centre in Shalakan, 4 km northwest of the Delta Barrage in Qualubia Governorate.
Publishers
B.V.
280
Twenty thousand Bolinus and Biomphalaria alexandrina snails were used for each 10 m length of canal. The constituents of nature are mud and weed plants growing in the streams.
2. Experimental Preparation
techniques of slow release styrene-butadiene
rubber formulation
for field
use
Compounding and mixing were performed in a large-scale mixer (Buzuiuk Komarova NAR-Bodink, Komarova Horovic MTS, Vyrobinicisllo ‘7168, Type Strong 14240/P3, Rokvyroby 1967/l). The blend was made into 4 mm thick sheets and cut into rectangles of 170 X 60 cm. The sheets were vulcanized [4] at 143 + 2°C for 30 min in an autoclave (Skoda, Hradec Kralove, Czechoslovakia). After vulcanization, the sheets were cut with an electrical knife into small squares having average dimensions of 2 X 2 cm and 0.4 cm thickness. The formulation used was: SBR (loo), HAF (50), ZnO (3), S (l), MBT (l), TMTD (l), PBN (l), stearic acid (O.l), (NH&SO‘, (2), CuSO, *Hz0 (157.5).
Construction
of the canals for field tests
Six irrigation canals were constructed, three having a length of 30 m and widths of 2 m and 1.5 m at the upper surface and the bottom, respectively. The depth of the canals was about 1 m, and the canals were fed from a larger stream connected to the El-Bassosia canal. The draining canal was similar to the feeding stream, with a concrete base of 10 cm thickness, and brick walls of 25 cm thickness for the lower part of 45 cm height, and of 12.5 cm thickness for the upper part, with a total height of 1 m. Each canal was provided with inlet and outlet water openings. The other three canals had the same construction but differed in length and width (10.5 m length and widths of 1.5 m and 0.5 m at the upper surface and at the bottom, respectively). Figure 1 illustrates the canals.
Fig. 1. A graphical representation of one of the small irrigation canals constructed. Scale 1:300; all dimensions in centimeters.
Leaching
rate test [5, 61
The concentration of copper ions leached into the water of the canals was determined using the carbamate method. Thus, 20 ml of the leaching solution was transferred into a 250 ml separatory funnel, and then 2 ml of 20% citric acid solution, 2 ml 10% ammonium hydroxide solution and 2 ml 0.1% carbamate reagent solution were added. The yellow copper complex was extracted with an accurately measured amout of 10 ml carbon tetrachloride. Using a copper calibration curve [7] the leaching rate was calculated using the following equation: Leaching rate (pg/l) = F X D X 50 where F is the factor calculated from the calibration curve 33.3 [7] at X = 440 nm, and D is the optical density.
RESULTS
Effect
AND
DISCUSSION
of concentration
butadiene
of controlled
rubber formulation
release styrene-
on leaching
rate
The field tests were carried out during the months of May, June, and July, 1984. At the beginning of the experiment, the concentrations of copper ions in the water and in the
281
was relatively constant after a soaking period of 40 days, and these concentrations were very effective in achieving 100% mortality of snails. The above data suggest that LC,,, (the concentration at which 100% mortality occurs) is 116 r.lg/l, which is the minimum concentration for killing most snails. The LT,,, (the time at which 100% mortality occurs) increased by decreasing the concentration of the molluscides used, as shown in Fig. 3. Samples of mud from the bottom were also taken from the treated and untreated canals in order to determine adsorbed Cu? Results are shown in Table 1.
surface mud were 36-44 pg/l and 46-48 pug/g mud, respectively. The level of water was 50-60 cm and remained unchanged during the experiment, pH was 7.2-7.5, and the temperature was 24-27°C. The concentrations of rubber formulation containing CuS04 *Hz0 used were 1, 2, 4, and 6 kg/m3 in canals No. 1, 3, 4, and 6, respectively, leaving canals No. 2 and 5 without treatment as control. The leaching rate of copper ions in a canal containing clear water is shown in Fig. 2. The concentration of copper ions released into the water increases with increasing dose of the molluscide distributed in the streams. The concentration of copper ions in canals No. 1 and 3 was lower than those in canals No. 4 and 6 after an initial immersion of 6 days. After a further 20 days exposure, the concentrations of copper ions in canals No. 1, 3, 4, and 6 became 116,128,183, and 224 pg/l, respectively. These concentrations were found to be adequate to kill the Bolinus and Biomphalaria alexandrina snails which were used to test the efficacy of the controlled release molluscides. In canals No. 2 and 5 the concentration of copper ions remained unchanged at 44 pg/l. The rate of Cu” leached
zl
h
40-
.
20 -
0
[So 0
20
40
, Fig. 3. A graphical tion of LC,,,.
01
0
’ VJ
fi 20
30
00
so
60
,o
80 90 Time (days
)
100
Fig. 2. Effect of concentration of molluscide formulations on leaching rate. Key: 0: canals No. 2, 5, concentration of molluscide 0 kg/m3 (control); 0: canal No. 1, concentration 1 kg/m3; x : canal No. 3, conA: canal No. 4, concentration 4 centration 2 kg/m’; kg/m3;. : canal No. 6, concentration 6 kg/m3.
J
60
_
80
%o 100 _
representation
%Xl 120
140
160
of the determina-
In Table 1 it can be seen that the average copper ion concentrations in the surface mud were 98, 104, 110, and 114 pg/g dry mud after 20 days of exposure in canals No. 1, 3, 4, and 6, respectively, while the average copper ion concentration in canals No. 2 and 5 was still between 46 and 50 pg/g mud. These amounts of copper ions were relatively constant during the whole experiment. Therefore, the mortality rate of snails depends on the amount of copper ions released into the water and is not affected by copper ions adsorbed on the surface of the mud at the bottom and at the sides of the canals.
282 TABLE 1 CU*+ adsorbed on mud on the bottom Canal No.
1 2 3 4 5 6
of both treated and untreated
canals
Concentration of molluscide added (kg/m’)
Concentration of Cu’+ adsorbed on mud (pg/g) after soaking period of 0 days
10 days
20 days
1 0 2 4 0 6
46-48
61 47 68 76 46 78
98 48 104 110 48 114
40 days 98 48 115 115 50 120
100 days 104 48 98 110 48 118
TABLE 2 Effect of water level on concentration tration of molluscide added 2 kg/m3 Exp. No.
1 2 3
Level of Hz0 (cm)
20-25 30-40 50-60
of copper ions leached into clear water; concen-
Leached copper ions in clear water (pg/l) 0 days
3 days
5 days
10 days
15 days
20 days
36-44
66 52 52
98 96 86
186 111 96
225 198 102
246 125 116
Effect of water depth on copper ion concentrations
A study of the effect of the level of water on concentration of copper ions leached into water under environmental conditions is necessary in order to determine the molluscidal dose which is suitable for each level. Levels of water, and times of exposure at 25-27”C, are shown in Table 2. From Table 2, it can be observed that the concentration of molluscides under test (2 kg/m3) gave average concentrations of 66, 52, and 52 pg/l after an initial immersion of 3 days in experiments No. 1, 2, and 3, respectively. Also, it was shown that the concentration of Cu2’ increased in time but differs with the level of water. It is apparent, therefore, that at higher levels of water a higher dose of controlled release rubber formulation is required to obtain 100% mortality of snails within a suitable time. Also, concentration of Cu2’ in water was affected by the depth of water.
From results obtained in this study, it is concluded that this controlled release technique is an effective means for controlling snails and that it can be applied at any time of the year. REFERENCES
N.F. Cardarelli, Controlled Release Pesticide Formulations, CRC Press, Cleveland, OH, 1976, p. 20-25,28, 53-55,102. S.V. Kanakkanatt, Schistosomiasis control by slow release molluscides, Product Development Laboratory Report, University of Akron, OH, Sept. 15,1972. F.M. Helaly and M.H. Nosseir, Evaluation of controlled release styrenebutadiene rubber formulation containing copper sulphate monohydrate as molluscicides under small field conditions, Ind. J. Technol., in press. ASTM Designation, D 15-66 T, 1967. A. Parington, Paint Technol., 27( 3) (1963) 17. F. Marson, J.Oil Colour Chem. Assoc., 47 (1964) 323. N.A. Ghanem and M.M. Abd El-Malek, J. Chem. Arab Republic Egypt, 9 (1966) 377.