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Degradation of Extraction from Seaweed and Its Complex with Rare Earths for Organophosphorous Pesticides
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ScienceDirect JOLRNAL OF RARE E4KTHS 25 (2007) 93 - 99
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Degradation of Extraction from Seaweed and Its Complex with Rare Earths for Organophosphorous Pesticides Xang Dongferg ( Z $ R ) ' *Sun , Jipeng ( ~ , J . % N $ ) ' , Du Dehong (#4%$1)' Sun , Liping ( ~ b $ ~ ) ' , Chen Zhende ,')&%.$P( Xue Changhu (@-k;@)' ( 1 . College o f Food Science and Engineering , Ocean University of China , Qingdao 266003, China ; 2 . Qingdao ilcndern~ of 4,rriculturnl Science , Qingdao 266100, China ) ReceiJed 30 hla 2006; rrtisrd 9 Aupust 2006
Abstract: On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE ) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with I;E on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The results shoived ti at the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88 % , 52.30% , 49.52% , and 22.88 % , respectively, for chlorpyifo: , dichlonos , omethoate , and dimethoate, and those by the complex decreased by 9 5 . 9 9 % , 54.23 % , 48.79 % , and 25.66 5% , respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach spra!r;l with the complex were decreased by 90.64% and 7 6 . 5 6 % , respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d . The fresh weight of brassica chinensis and cabbage incret >ed b>- 28.62 7c and 18.72% , and their dry weight increased by 4 4 . 4 9 % and 1 4 . 7 4 % , respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia Chinese were decreased by 36.36% and 50.00% , respectively, and their rate of decrease in cabbage was 40.00% and 75.00% , respectively, on 5th day after $praying with the complex, when compared with those in the vegetable from control. These results suggest that this romp ex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables. Key words : teaweed ; extraction ; organophosphorous pesticides ; degradation ; rare earths CLC number : 0614.3 ; S482.8 Document code : A Article ID: 1002 - 0721 (2007)Ol- 0093 - 07
Seaweed, kelp ( Laminaria juponiza ) , is an important plant. which is abundant in ocean. It has been used as a fertilizer in agriculture for the past several 1-3 . Tlir seaweed liquid fertilizer was first preyears pared in Brit,iin in 1949. So far, the liquid fertilizer has been prociuced and used in several countries, including Britain, *4ustralia. France, and China. It has been proved from several experiments carried out in
*
China that the seaweed liquid fertilizer can promote the growth and the development of crops and increase their yield, and the rate of increase of yield is 6% 35%. The results from various experiments have proved that the enhancement effect is mainly because of the presence of polysaccharide and oligosaccharides in the seaweed liquid fertilizer"' 4 3 5 1 . It was proved that there are rare earth elements
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Correspo iding author ( E-mail : wangdf@ our rdu . c n ) Foundatitin item: ProJert support~dby the Natural Srientifir Foundation of Shandong Province ( Z 20041)OS) arid Qingdao City (05-2-NS-21) Biographv : W m g Dongfmg ( 1956 - ) , M a l ~ .Doctor, Profewor; Research direction: Food chem. and food safety Copyright g2007. b! Editorial Committee of Journal of the Chinese Rare Earths Society. Published by Elsevier B . 1'. All rights reserved.
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JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . I , Feb. 2007
(REEs) in water extraction from tea (infusion), and that polysaccharide in tea binds REEsr6.7’ . Recently, it has been proved that complexes of tea polysaccharide or algae polysaccharides, and Ce4’ can degrade the phosphodiester bonds and chlorpyrifos at pH 7 . 0 and 37 T[5,8 - 1 0 ] In China, scientists have applied inorganic compounds of rare earths ( R E ) , such as RE ( N 0 3 ) 3 , as microelements fertilizers in agriculture and studied their effects on crop yield and quality. The results of agricultural experiments show that the use of RE can increase the production of crop nearly 50%, but these increase are typically in the range of 8% 10%“”. These results suggest that the complex made from the polysaccharide and REEs can increase the crop yield and degrade the organophosphorous pesticides. However, studies with regard to this have not been reported so far. Organophosphorous pesticides are widely used in agriculture after the ban of organochlorine insecticides because of their acute toxicity. The organophosphorous pesticides are highly effective to control the pests, and thereby avail low cost and high quality food. On the other hand, these pesticides pose severe health risks. These pesticides are discharged into air and water, and through the consumption of food that contains these pesticide residues it reaches human body. Risk of dietary exposure to the pesticide residues has been of public concern as the pesticides are used in agriculture. A method that can increase both the agricultural productivity and reduce the pesticide residues is required for increasing the crop production. This study focused on the degradation of organophosphorous pesticides in neutral solvent using an extract from seaweed liquid fertilizer and its complex with R E , and the effects of spraying with the complex on the residue of organophosphorous pesticides and the yields of vegetables. This may provide a novel method for increasing the agricultural productivity and reducing the use of pesticide residues in the production of vegetables.
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1 Materials and Methods 1.1 Reagents Chloropyrifos , omethoate , dichlorvos , and dimethoate were the regents used in agriculture. The certified standards of dimethoate ( CAS No, 60-51-5 ) , chlorpyrifos (CAS N o . 2921-88-2), omethoate (CAS No. 1113-02-6) , and dichlorvos ( CAS No. 62-73-7) were obtained from Sigma. RE( NO3), foliage fertilizer was obtained from Shangqiu Rare Earth Elements and
Microelements Fertilizer of Henan Pro\ irice in China, which was composed of La ( 6 1 . 4 9 % ) , Ce ( 1 4 . 4 8 % ) , Pr ( 5 . 7 8 % ) , Nd ( 16. 7 8 % ) , Sm ( 1 . 0 6 % ) , Gd ( 0 . 2 5 % ) , and Eu ( 0 . 2 2 % ) . All other chemicals used were of guaranteed grade and obtained from China Chemicals C o . , Ltcl. Double distilled water was used throughout this study.
1.2 Preparation of extract from seaweed The seaweed liquid fertilizer is a water-soluble extract obtained from seaweed, which is prepared using water or 0.01 mmol * L HCl“] . The water-soluble polysaccharide is the main function component in the fertilizer. An extract, coarse polysaccliaride , was prepared from the seaweed liquid fertilizer using the methods described by Fan et a l . “I, Zvyagintseva et al. [ I 2 ’ , and Qi et al. ‘13’ . The seaweed samples (Laminaria japonica) were purchased from Yantai City of Shangdong Province in China, in Oct . 2003. The extract was prepared as follows. The dried seaweed ( 1 0 0 . 0 g ) was successively extracted twice with 3000 ml of 0. 01 mmol. L-’ F I C ~at room temperature for 60 min. The extraction liquid was concentrated in rotary evaporator by reducing the pressure. sedimentated by 9 5 % alcohol for 24 h , and centrifugalized (5000 r - m i n - ’ ) . The sediment was washed five times with ethanol, acetone, and ether to ensure the complete removal of liquid. The extract, which contains mainly the water-soluble polysaccharides , was obtained by drying the sediment under vacuum at 70 “c . ~
’
1 . 3 Preparation of homogeneous solutions composed of extraction and RE The homogeneous solutions composed of the extraction and RE was prepared by the modification of the method proposed by Kajimura et a l . I‘“ and Qi et al. [13! . The R E ( N 0 3 ) 3was dissolved i n the water soluble extract with a concentration of 5 mg ml-’ , the content of RE (NO,), was 0.06 m g - m l - ’ in the homogeneous solutions, the pH of the solutions was adjusted to 7 . 0 using a small amount of NaOH , then reacted for 12 h at 45 “c. After centrifugalization for 12 months, a stable and homogeneous mixure solution was obtained. The solid complex was obtained by concentration and drying under vacuum at 7 0 “c .
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1 . 4 Degradation of extraction and its complex with RE for organophosphorous pesticides in neutral solvent The degradations of the pesticides chloropyrifos , omethoate , dichlorvos , and dimethoate in neutral solvent, which are widely used in agriculture, were car-
Wang D F et a1 . Degradation of Extraction from Seaweed with RE for Organophosphorous Pesticides
ried out in sealed glass tubes. The reaction system was as follows: .I otal of 0 . 1 ml of the extraction and its complex with RE (the concentration of both was approximately 5 ing * ml- ) were mixed with a fixed quantit!- of onrethoate, dichlorvos, chloropyrifos, and dimethoate, rtspectivel>-. The reaction was carried out at 25 T at pH 7 . 0 for 48 h . The contents of the pesticides were detected using gas chromatograph.
1 . 5 Degradation of extraction and its complex with RE for organophosphorous pesticides in spinach Chlorp!-i ifos and dimethoate are the commonly used pesticide, for spinach in China. This study focuses on whether chlorpprifos and dimethoate in spinach are degraded 7~ the extraction and its complex with R E . A spinacsi (Boza 10) garden representing general spinach gardens was selected from the experimental farni of the -4;:ricultural Science :lcademy of Qirigdao (Shandong Province. China) in March 2004. The soil conditions in lie experimental farm were very similar. Rows of spina .h in the garden were randomly selected for the experitnent with an area of 1 . 0 ni x 16. 7 m each. The spinach was treated as follows: eighteen plots were rat domly selected and nine of them were sprayed with ( irnethoate. another nine plots with chloropyrifos. To 'ricrezse the pesticides residues in spinach, the pest (,ides were s p r a y d twire acrording to the manufacturer's instructions. After 2 d , the plots were spraved t-ith an equal volume of the extraction, the complex 1 hoth concentration 5 mg ml- ) , and water. The sp naches were randomly reinaved from the same plots i t n iiediatel!. after spra? ing with the extraction, the comidex. and water, respectively, and then after 2 , 4 , 6 ind 8 d , cleaned. aired, weighed, and anal!-zed imni diatel!-. Eac,h treatment was repeated thrice (differeit plots ) , arid all the plots w~eresubjected to similar tlianagenient practices.
1.6
Effecls of complex on yield of vegetables and degradation of organophosphorsus pesticides
To further prove the effect of complex to reduce the pesticide iesidues and to increase productivity, the effects of the complex made from the extraction aqd RE on the ?ield of wgetables and the contents of org m n p h n s p h n r c ~ i iprqticdes ~ were stiidied in the experimental farm o Agricultural Science Academe of Qingdao ( Shandon: Province, China ) during May 2005. Brassica chint nsis ( Suzhouqin) and cabbage (Zhong Gan No. I 1 ) garden represelltirig general gardens were selected from the farm. K o w of the vegetables were
95
randomly selected from the experimend plots, with an area of 1 . O m x 14.9 m and 1.0 m x 2 6 . 4 m , respectively, for Brassica chinensis and cabbage. The brassica chinensis and cabbage were sprayed with the complex and the same volume of water as the control, respectively, on May 9. The 20 samples of cabbages and brassica chinensis within 2 m x 1 . 0 m were randomly pulled out from the plots after 24 d , fresh weight was immediately measured, and dry weight was measured according to the conventional method to analyze the effect of the complex on the productivity of the vegetables. Twenty-four plots were randomly selected at the farm and twelve of them were sprayed with dimethoate, another twelve plots with chlorpyrifos according to the manufacturer's instructions. After 1 d , the plots sprayed with dimethoate or chloropyrifos were randomly trisected. One of them was sprayed with the complex (concentration 5 m g * m l - ' ) , another with the same volume of water; the remaining four plots were neither sprayed with complex nor with water as the control. After 3 , 5 d , approximately 200.000 g of the samples from the different treatments were selected fos immediately analyzing the organophosphorous pesticides. Each treatment was repeated 4 times (different plots), and all the plots were subjected to the same management practices.
1.7
Analysis of organophosphorous pesticides
The residues of organophosphorous pesticides were analyzed according to the same method described in a previous study using gas chromatography ( G C ) ( HP6890) with flame photometric detector (FPD) and glass capillary column ( 30 m x 0 . 3 2 mm ID ) ( 190915-413). The pesticides were performed by automatic integration of the peak area, and certified standards of dimethoate ( CAS No. 60-51-5) , chlorpyrifos (CAS No. 2921-88-2), omethoate (CAS No. 1113-02-6) , and dichlorvos (CAS No. 62-73-7) were used for external calibration"" .
1.8
Analysis of REEs in extract and its complex with RE A total of 2 0 0 . 0 mg of samples were microwave
digested. and then the contents o f HEKs were analyzed using inductively coupled plasma atomic emission spectrometry ( ICP-AES ) ( VISTA-MPX , VARJAN, USA) similar to the method described in the previous study~I3j.
JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . 1 , Feb . 2007
96
Table 1 Contents of REEs in extract and complex (mg- kg-' , dw) * Elements
La
Ce
Er
Eu
Gd
Ha
Nd
Pr
Tm
XREEs
Extract/( mg .kg - )
0.34
13.63
0.47
0.01
0.05
ND
0.02
1.06
0.02
15.65
ND 0.11 0.02
0.13
6.37
0.13
100.00
29.53
67.47
4.03
547.28
5.40
12.33
0.74
100.00
Extrart/%
2.17
87.09
3.00
0.06
0.32
Cornplex/(mg.kg-')
208.07
224.58
0.77
0.78
11.94
Complex/%
38.02
41.04
0.14
0.14
2.18
Contents of REEs that are not indicated in the table were not detectable (data in the table are rxprrssed as means of n = 2 samples on the hasis of oven-dried weight, ND represents the contents that are not detectable) ++
2 Results and Discussion 2 . 1 Extract and complex containing REEs Researches have shown that REEs can enter into plants and animals, and REE-bound polysaccharides and REE-bound peroxidase protein have been identified 6 ' 7 9 ' 5 ' . To investigate the extract-bound REEs, the contents of KEEs in the extract were analyzed. The data in Ta& l indicate that the extract contains REEs and that the main REEs present in the extract are Ce, Pr, E r , and L a , accounting for about 99% of the total content of REEs , especially Ce content is the highest, accounting for about 87% . It is found that on cleavage of the phosphodiester bonds, the activity of REEs, especially Ce, was overwhelmingly higher than that of other metal ion^['^,'^, "]. However, REEs easily forms a gel of metal hydroxide in neutral solution, and this feature imposes limitations to the scope of its application in agricultural and environmental sciences . Fortunately, Kajimura et a1 . [I4' found that dextran , some monosaccharides and their ramifications such as lyxose and mannitol can coordinate with Ce4+ by oxygen atoms to form complexes, which can easily dissolve in water and hydrolyze The data in Table 1 show that the plasmid extract can bind REEs, which is attributed to the fact that the extract containing several saccharide molecules and oxygen atoms linked to the sugar moiety can bind REEs; therefore, it is possible to prepare complexes that are stable and homogeneous. The total content of REEs in the complex is 35 times higher 35 than that in the extract (Table 1) . The main REEs present in the complex are Ce, L a , P r , and Nd, accounting for about 97 % of the total content of REEs .
2. 2
Degradation of organophosphorous pesticides using extract and its complex in neutral solvent
It is found that on cleavage of phosphodiester bonds, the activity of REEs was overwhelmingly higher than that of other metal ions. Recently, the authors have reported that the complex of algae polysaccharide
and Ce4' can cleave plasmid DNA and hydrolyze chlorpyrifos"O1. Table 1 shows that the extract and its complex contains larger amounts of REEs, which suggests that the extract and its complex with RE can also hydrolyze organophosphorous pesticides . However, thus far, there has been no report on the hydrolytic activity of R E . To confirm the above speculation. the degradation of chloropyrifos , omethoate , dichlorvos , and dimethoate in neutral solvent were carried in sealed glass tubes, respectively, using the extract and its complex with R E . The results show that the extract and its complex with RE can degrade chlorpyrifos , dichlorvos, omethoate , and dimethoate (Table 2 ) . The residues of the pesticides treated using the extract decrease by 96. 88% , 52. 30% , 4 9 . 5 2 % , and 2 2 . 8 8 % , respectively, for chlorp! rifos , dichlorvos, omethoate , and dimethoate, and those treated using the complex decrease by 95. 99% , 54. 23 ?k , 4 8 . 7 9 % , and 25.66% , respectively, when compared with those in control. It is evident that the effluence resulting from the degradation of chlorprifos using the extract and its complex is overwhelmingly higher than that of other organophosphorous pesticides ; however, there is no difference between the extract and its complex with RE in vitro for degrading the pesticides.
Degradation of organophosphorous pesticides in spinach using the extract and its complex with RE
2. 3
Seaweed liquid fertilizer and RE has been applied Table 2
Degradation of organophosphorous pesticides in neutral solvent using the extract and its complex with RE(mg.L-') Dimethoate
*
Dichlorvos
Omethoate
8.26 k 0.57
Control
4.72 0.58
6.52 k 0.45
Extract
3.64+0.35
3.11 *0.35* * 4.17k0.36'
Chlorpyrifns
24.06 k 0.88 0.75k0.21" *
3.51k0.45" 2.98-0.32"" 4.25+0.55" 0.96k0.31"" P < 0.05 ; * * P < 0.01 ; The degradation of the pesticides in neu-
Complex
*
tral solvent was carried out in sealed glass tubes. The contents of the pesticides were analyzed using gas chromatography ( C,C 1 . Data are expressed as means f S . D. of n = 3 .
97
Wang D F et a1 . Degradation of Extraction from Seaweed with RE for Organophosphorous Pesticides
to agricultural i:rops in China to increase crop yield. It is found that the extract arid its coniplex with RE can degrade organcrphosphorous pesticides in neutral solvent. which sLggests that the!- can be used both for increasing agricdtural productivity and reducing pesticide residues. In this stud!-, emphasis is being laid on chlorpyrifos and dimethoate, as they are the most commonl!- used peiticides in spinach production. The results show that spraving with the extract and the complex can signi icantly degrade chlorpyrifos arid dimethoate in the sainach ( Fig. 1 ) . The data in Fig. 1 indicate that the residues of chlorpyrifos ar d dimethoate in spinach obtained from the plots spra!i.d with the extract decrease by 16.60% and 16.33% , respectively, when cornpared with those in spinach obt iined from the control plots when the interval between spraying and sampling is 2 d . It decreases by 6 5 . 4 6 7c and 47.34% , respectively, when the interval be tween spraying and sampling is 8 d . The resic ues of chlorpyrifos and dimethoate in spinach obtained from the plots spra>-ed with the complex were 0 . 35 and 0 . 97 mg k g - ' , respectively, whereas 9 . 09 and 3. 973 mg k g - ' in spinach from control plots 1. hen the intenal between spraying and sampling was 3 d . The residues of chlorpyrifos and dimethoate decri-ases b y 90.64% and 76.56% , respectively, when compared N-ith those in spinach from control plots. It i,, evident that the degradation of the pesticides in v i m using the complex is better than that of the extract. To facilil ate statistical analyses, the conceritrations of residues were plotted against time for each data set (Table 3). and the first-order kinetics were determined for b ith chlorpyrifos and dimethoate. The co-
efficient of determination ( R 2 ) was > 0.92 in all case s , proving the quality of fitting. The calculated firstorder kinetic parameters show that chlorpyrifos and dimethoate exhibited the highest values of half-life period ( t l i z ), 4.748 and 4 . 5 2 9 d , respectively, when the spinach was sprayed with water as control, whereas the pesticides exhibited the shortest values of half-life period, 2.126 and 2.616 d , respectively, when the spinach was sprayed with the complex.
2 . 4 Effects of complex on yield of vegetables and contents of organophosphorous pesticides residues Brassica chinensis and cabbage are vegetables that are common in China. 'Their growth season usually corresponds to the season during which diseases and insect pests are prevalent. At present, organophosphorous pesticides, such as omethoate and chlorpyrifos , have been widely used to protect the vegetables from Table 3
e
Equation and t1,2of chlorpyrifos and dimethoate of spinach sprayed with the extract and its complex with RE'
Experiments
Equation
K2
t iizld
Dimethoate Control Extract
~= 17,94e-n m X
y = 16.575e-n.?3'
0.9224 0.9944
4.529 3.258
Complex ChlorpTifos
y = 20.197
0.9545
2.616 __-
Control
y = 28.538 e ' 5 3 4 r 7 ~ 3 0 . 4 9 4e - " 282ir y = 3 4 , 4 1 e-".43Mx
0.9623
4.748
0.9903 0.9743
2.815 2.126
~~
~~
~"
Extract Complex x
162x
,-@
R2 = coeffirient of determination;
tl,?
= half-life period
20
2
4
6
8
Ob
2
4
6
8
Aftcr spraying ;d ARcr spraying id Fig. 1 Etfects i i spraying with extract and its complex with Kli on degradation 01 chlorpyrihs ( a ) a i d dirrirtliu& ( h ) i n spinach ( Spinaches were separatelv spraved with dimethoate and chloropyrifos . Two days later, the spinaches were separately sprayed with the extract. its corniilp\ with K E , and water as control. The spinaches were randomly picked up from the same plots immediately after spraying and the!- w r e anaiyzed after 2.4.6, and 8 (1. Data are expressed as means ? S . I). of n = 3 samples on the basis of fresh weight)
JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . 1 , Feb . 2007
98
the damage caused by insect pests in China because they are cost-effective easily available, and display a wide spectrum of bioactivity although some new molecules, which are biodegradable, have low toxicity to mammals and have low residual life, are being developed. Fig. 1 indicates that spraying with the complex can evidently decrease the residues of chlorpyrifos and dimethoate in spinach. To further prove the effects of the complex on the residues of organophosphorous pesticides and the yield of vegetables and acting as a novel method both for increasing productivity and reducing pesticide residues for vegetables production. The effects of the complex were studied on Brassica chinensis and cabbage. The results showed that spraying with the complex could both increase the yields of Brassica chinensis and cabbage and decrease the resi-
dues of the pesticides (Tables 4 and 5 ) . The fresh weight increased by 28.62% and 1 8 . 7 2 % , and the dry weight increased by 4 4 . 4 9 % and 1 4 . 7 4 % respectively, for Brassica chinensis and cabbage when compared with those of the controls. Table 4 Effects of spraying of complex on vegetable yield (8)* EXpennmh-
BrBsica chinensis
cabbage
Fmh weight
Fresh wreight
~
Dry wei&t
Dry weight
~~~
Contml Chmplex
873.2+852.6 5l2.3k57.5 11240.3k76.7 740.2+6$.3
25461.8k 7m.O 148.5*119.3 32%.1i '50.0 1641.3 k 37.2
*
Vegetables were sprayed with the complex and water as control, respectively. Samples were randomly picked up from the plots at 24 d later, and then the weight of the samples was measured immediatel? . Each treatment w a s repeated 4 times (different plots) , and all the plots were subjected to the same management practices. Data are expressed as means & S . D . of n = 4
#
Table 5 Contents of pesticide residues in vegetable at 3 and 5 d after spraying with complex (mg-kg-' f.wt) * Brassica chinensis Expenments
Dimethoate 3d
Control
0.29k0.04
Water Complex
Cabbage
~
-~
Sd
Chlorpymfos 3d
5 d
Dimethoate 3d
0.2220.06
1.81k0.53
0.99&0.09
0.03k0.01
5d 0.04+.0.01
0.26k0.06
0.22r0.04
1.64r0.21
0.76k0.27
0.03r0.02
0.27k0.05
0.11r0.03"
1.17*0.11
0.63&0.17"
0.03k0.03
_
_
_
_
_
Chlorpynfos 3rl
5d
O.lOkO.04
0.10+0.04
0.03&0.02
0.07kO.06
0.06kO.W
0.01+0.01*
0.03k0.01"
0.06kO.05
*
P < 0.05 ; The vegetables were sprayed with dimethoate and chloropyrifos, and 1 d later, they were sprayed with the complex and water, or neither as control. Samples are randomly picked up from the plots at 3 d and 5 d later, respectively, .and then the residues w'ere analyzed imine
The residues of chlorpyrifos and dimethoate in Brasscia chinensis and cabbage sprayed with the complex are smaller in percentage compared with those sprayed with water or with those that were not treated. The residues of chlorpyrifos and dimethoate in brasscia chinensis decrease by 36.36% and 5 0 . 0 0 % , respectively, at 5 d after spraying the complex, when compared with those in the vegetable from control plots and in cabbage where the residues decrease bv
ral Science ) , 2003, 1 : 28. [ 31 Zheng H X , Xu G M , Feng C .
[4]
[5]
Y
40.00% and 75.00 % respectively. It is evident that spraying with the complex can both increase the yields of vegetable and decrease the residues of organophosphorous pesticides. However further investigation should be carried out to know the mechanism by which the complex derived from the extract and RE increases crop yield and decreases pesticide residues.
[6]
[7]
[ 81
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ScienceDirect JOLRNAL OF RARE E4KTHS 25 (2007) 93 - 99
www .elsevier.codlocate/jre
Degradation of Extraction from Seaweed and Its Complex with Rare Earths for Organophosphorous Pesticides Xang Dongferg ( Z $ R ) ' *Sun , Jipeng ( ~ , J . % N $ ) ' , Du Dehong (#4%$1)' Sun , Liping ( ~ b $ ~ ) ' , Chen Zhende ,')&%.$P( Xue Changhu (@-k;@)' ( 1 . College o f Food Science and Engineering , Ocean University of China , Qingdao 266003, China ; 2 . Qingdao ilcndern~ of 4,rriculturnl Science , Qingdao 266100, China ) ReceiJed 30 hla 2006; rrtisrd 9 Aupust 2006
Abstract: On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE ) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with I;E on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The results shoived ti at the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88 % , 52.30% , 49.52% , and 22.88 % , respectively, for chlorpyifo: , dichlonos , omethoate , and dimethoate, and those by the complex decreased by 9 5 . 9 9 % , 54.23 % , 48.79 % , and 25.66 5% , respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach spra!r;l with the complex were decreased by 90.64% and 7 6 . 5 6 % , respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d . The fresh weight of brassica chinensis and cabbage incret >ed b>- 28.62 7c and 18.72% , and their dry weight increased by 4 4 . 4 9 % and 1 4 . 7 4 % , respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia Chinese were decreased by 36.36% and 50.00% , respectively, and their rate of decrease in cabbage was 40.00% and 75.00% , respectively, on 5th day after $praying with the complex, when compared with those in the vegetable from control. These results suggest that this romp ex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables. Key words : teaweed ; extraction ; organophosphorous pesticides ; degradation ; rare earths CLC number : 0614.3 ; S482.8 Document code : A Article ID: 1002 - 0721 (2007)Ol- 0093 - 07
Seaweed, kelp ( Laminaria juponiza ) , is an important plant. which is abundant in ocean. It has been used as a fertilizer in agriculture for the past several 1-3 . Tlir seaweed liquid fertilizer was first preyears pared in Brit,iin in 1949. So far, the liquid fertilizer has been prociuced and used in several countries, including Britain, *4ustralia. France, and China. It has been proved from several experiments carried out in
*
China that the seaweed liquid fertilizer can promote the growth and the development of crops and increase their yield, and the rate of increase of yield is 6% 35%. The results from various experiments have proved that the enhancement effect is mainly because of the presence of polysaccharide and oligosaccharides in the seaweed liquid fertilizer"' 4 3 5 1 . It was proved that there are rare earth elements
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Correspo iding author ( E-mail : wangdf@ our rdu . c n ) Foundatitin item: ProJert support~dby the Natural Srientifir Foundation of Shandong Province ( Z 20041)OS) arid Qingdao City (05-2-NS-21) Biographv : W m g Dongfmg ( 1956 - ) , M a l ~ .Doctor, Profewor; Research direction: Food chem. and food safety Copyright g2007. b! Editorial Committee of Journal of the Chinese Rare Earths Society. Published by Elsevier B . 1'. All rights reserved.
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JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . I , Feb. 2007
(REEs) in water extraction from tea (infusion), and that polysaccharide in tea binds REEsr6.7’ . Recently, it has been proved that complexes of tea polysaccharide or algae polysaccharides, and Ce4’ can degrade the phosphodiester bonds and chlorpyrifos at pH 7 . 0 and 37 T[5,8 - 1 0 ] In China, scientists have applied inorganic compounds of rare earths ( R E ) , such as RE ( N 0 3 ) 3 , as microelements fertilizers in agriculture and studied their effects on crop yield and quality. The results of agricultural experiments show that the use of RE can increase the production of crop nearly 50%, but these increase are typically in the range of 8% 10%“”. These results suggest that the complex made from the polysaccharide and REEs can increase the crop yield and degrade the organophosphorous pesticides. However, studies with regard to this have not been reported so far. Organophosphorous pesticides are widely used in agriculture after the ban of organochlorine insecticides because of their acute toxicity. The organophosphorous pesticides are highly effective to control the pests, and thereby avail low cost and high quality food. On the other hand, these pesticides pose severe health risks. These pesticides are discharged into air and water, and through the consumption of food that contains these pesticide residues it reaches human body. Risk of dietary exposure to the pesticide residues has been of public concern as the pesticides are used in agriculture. A method that can increase both the agricultural productivity and reduce the pesticide residues is required for increasing the crop production. This study focused on the degradation of organophosphorous pesticides in neutral solvent using an extract from seaweed liquid fertilizer and its complex with R E , and the effects of spraying with the complex on the residue of organophosphorous pesticides and the yields of vegetables. This may provide a novel method for increasing the agricultural productivity and reducing the use of pesticide residues in the production of vegetables.
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1 Materials and Methods 1.1 Reagents Chloropyrifos , omethoate , dichlorvos , and dimethoate were the regents used in agriculture. The certified standards of dimethoate ( CAS No, 60-51-5 ) , chlorpyrifos (CAS N o . 2921-88-2), omethoate (CAS No. 1113-02-6) , and dichlorvos ( CAS No. 62-73-7) were obtained from Sigma. RE( NO3), foliage fertilizer was obtained from Shangqiu Rare Earth Elements and
Microelements Fertilizer of Henan Pro\ irice in China, which was composed of La ( 6 1 . 4 9 % ) , Ce ( 1 4 . 4 8 % ) , Pr ( 5 . 7 8 % ) , Nd ( 16. 7 8 % ) , Sm ( 1 . 0 6 % ) , Gd ( 0 . 2 5 % ) , and Eu ( 0 . 2 2 % ) . All other chemicals used were of guaranteed grade and obtained from China Chemicals C o . , Ltcl. Double distilled water was used throughout this study.
1.2 Preparation of extract from seaweed The seaweed liquid fertilizer is a water-soluble extract obtained from seaweed, which is prepared using water or 0.01 mmol * L HCl“] . The water-soluble polysaccharide is the main function component in the fertilizer. An extract, coarse polysaccliaride , was prepared from the seaweed liquid fertilizer using the methods described by Fan et a l . “I, Zvyagintseva et al. [ I 2 ’ , and Qi et al. ‘13’ . The seaweed samples (Laminaria japonica) were purchased from Yantai City of Shangdong Province in China, in Oct . 2003. The extract was prepared as follows. The dried seaweed ( 1 0 0 . 0 g ) was successively extracted twice with 3000 ml of 0. 01 mmol. L-’ F I C ~at room temperature for 60 min. The extraction liquid was concentrated in rotary evaporator by reducing the pressure. sedimentated by 9 5 % alcohol for 24 h , and centrifugalized (5000 r - m i n - ’ ) . The sediment was washed five times with ethanol, acetone, and ether to ensure the complete removal of liquid. The extract, which contains mainly the water-soluble polysaccharides , was obtained by drying the sediment under vacuum at 70 “c . ~
’
1 . 3 Preparation of homogeneous solutions composed of extraction and RE The homogeneous solutions composed of the extraction and RE was prepared by the modification of the method proposed by Kajimura et a l . I‘“ and Qi et al. [13! . The R E ( N 0 3 ) 3was dissolved i n the water soluble extract with a concentration of 5 mg ml-’ , the content of RE (NO,), was 0.06 m g - m l - ’ in the homogeneous solutions, the pH of the solutions was adjusted to 7 . 0 using a small amount of NaOH , then reacted for 12 h at 45 “c. After centrifugalization for 12 months, a stable and homogeneous mixure solution was obtained. The solid complex was obtained by concentration and drying under vacuum at 7 0 “c .
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1 . 4 Degradation of extraction and its complex with RE for organophosphorous pesticides in neutral solvent The degradations of the pesticides chloropyrifos , omethoate , dichlorvos , and dimethoate in neutral solvent, which are widely used in agriculture, were car-
Wang D F et a1 . Degradation of Extraction from Seaweed with RE for Organophosphorous Pesticides
ried out in sealed glass tubes. The reaction system was as follows: .I otal of 0 . 1 ml of the extraction and its complex with RE (the concentration of both was approximately 5 ing * ml- ) were mixed with a fixed quantit!- of onrethoate, dichlorvos, chloropyrifos, and dimethoate, rtspectivel>-. The reaction was carried out at 25 T at pH 7 . 0 for 48 h . The contents of the pesticides were detected using gas chromatograph.
1 . 5 Degradation of extraction and its complex with RE for organophosphorous pesticides in spinach Chlorp!-i ifos and dimethoate are the commonly used pesticide, for spinach in China. This study focuses on whether chlorpprifos and dimethoate in spinach are degraded 7~ the extraction and its complex with R E . A spinacsi (Boza 10) garden representing general spinach gardens was selected from the experimental farni of the -4;:ricultural Science :lcademy of Qirigdao (Shandong Province. China) in March 2004. The soil conditions in lie experimental farm were very similar. Rows of spina .h in the garden were randomly selected for the experitnent with an area of 1 . 0 ni x 16. 7 m each. The spinach was treated as follows: eighteen plots were rat domly selected and nine of them were sprayed with ( irnethoate. another nine plots with chloropyrifos. To 'ricrezse the pesticides residues in spinach, the pest (,ides were s p r a y d twire acrording to the manufacturer's instructions. After 2 d , the plots were spraved t-ith an equal volume of the extraction, the complex 1 hoth concentration 5 mg ml- ) , and water. The sp naches were randomly reinaved from the same plots i t n iiediatel!. after spra? ing with the extraction, the comidex. and water, respectively, and then after 2 , 4 , 6 ind 8 d , cleaned. aired, weighed, and anal!-zed imni diatel!-. Eac,h treatment was repeated thrice (differeit plots ) , arid all the plots w~eresubjected to similar tlianagenient practices.
1.6
Effecls of complex on yield of vegetables and degradation of organophosphorsus pesticides
To further prove the effect of complex to reduce the pesticide iesidues and to increase productivity, the effects of the complex made from the extraction aqd RE on the ?ield of wgetables and the contents of org m n p h n s p h n r c ~ i iprqticdes ~ were stiidied in the experimental farm o Agricultural Science Academe of Qingdao ( Shandon: Province, China ) during May 2005. Brassica chint nsis ( Suzhouqin) and cabbage (Zhong Gan No. I 1 ) garden represelltirig general gardens were selected from the farm. K o w of the vegetables were
95
randomly selected from the experimend plots, with an area of 1 . O m x 14.9 m and 1.0 m x 2 6 . 4 m , respectively, for Brassica chinensis and cabbage. The brassica chinensis and cabbage were sprayed with the complex and the same volume of water as the control, respectively, on May 9. The 20 samples of cabbages and brassica chinensis within 2 m x 1 . 0 m were randomly pulled out from the plots after 24 d , fresh weight was immediately measured, and dry weight was measured according to the conventional method to analyze the effect of the complex on the productivity of the vegetables. Twenty-four plots were randomly selected at the farm and twelve of them were sprayed with dimethoate, another twelve plots with chlorpyrifos according to the manufacturer's instructions. After 1 d , the plots sprayed with dimethoate or chloropyrifos were randomly trisected. One of them was sprayed with the complex (concentration 5 m g * m l - ' ) , another with the same volume of water; the remaining four plots were neither sprayed with complex nor with water as the control. After 3 , 5 d , approximately 200.000 g of the samples from the different treatments were selected fos immediately analyzing the organophosphorous pesticides. Each treatment was repeated 4 times (different plots), and all the plots were subjected to the same management practices.
1.7
Analysis of organophosphorous pesticides
The residues of organophosphorous pesticides were analyzed according to the same method described in a previous study using gas chromatography ( G C ) ( HP6890) with flame photometric detector (FPD) and glass capillary column ( 30 m x 0 . 3 2 mm ID ) ( 190915-413). The pesticides were performed by automatic integration of the peak area, and certified standards of dimethoate ( CAS No. 60-51-5) , chlorpyrifos (CAS No. 2921-88-2), omethoate (CAS No. 1113-02-6) , and dichlorvos (CAS No. 62-73-7) were used for external calibration"" .
1.8
Analysis of REEs in extract and its complex with RE A total of 2 0 0 . 0 mg of samples were microwave
digested. and then the contents o f HEKs were analyzed using inductively coupled plasma atomic emission spectrometry ( ICP-AES ) ( VISTA-MPX , VARJAN, USA) similar to the method described in the previous study~I3j.
JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . 1 , Feb . 2007
96
Table 1 Contents of REEs in extract and complex (mg- kg-' , dw) * Elements
La
Ce
Er
Eu
Gd
Ha
Nd
Pr
Tm
XREEs
Extract/( mg .kg - )
0.34
13.63
0.47
0.01
0.05
ND
0.02
1.06
0.02
15.65
ND 0.11 0.02
0.13
6.37
0.13
100.00
29.53
67.47
4.03
547.28
5.40
12.33
0.74
100.00
Extrart/%
2.17
87.09
3.00
0.06
0.32
Cornplex/(mg.kg-')
208.07
224.58
0.77
0.78
11.94
Complex/%
38.02
41.04
0.14
0.14
2.18
Contents of REEs that are not indicated in the table were not detectable (data in the table are rxprrssed as means of n = 2 samples on the hasis of oven-dried weight, ND represents the contents that are not detectable) ++
2 Results and Discussion 2 . 1 Extract and complex containing REEs Researches have shown that REEs can enter into plants and animals, and REE-bound polysaccharides and REE-bound peroxidase protein have been identified 6 ' 7 9 ' 5 ' . To investigate the extract-bound REEs, the contents of KEEs in the extract were analyzed. The data in Ta& l indicate that the extract contains REEs and that the main REEs present in the extract are Ce, Pr, E r , and L a , accounting for about 99% of the total content of REEs , especially Ce content is the highest, accounting for about 87% . It is found that on cleavage of the phosphodiester bonds, the activity of REEs, especially Ce, was overwhelmingly higher than that of other metal ion^['^,'^, "]. However, REEs easily forms a gel of metal hydroxide in neutral solution, and this feature imposes limitations to the scope of its application in agricultural and environmental sciences . Fortunately, Kajimura et a1 . [I4' found that dextran , some monosaccharides and their ramifications such as lyxose and mannitol can coordinate with Ce4+ by oxygen atoms to form complexes, which can easily dissolve in water and hydrolyze The data in Table 1 show that the plasmid extract can bind REEs, which is attributed to the fact that the extract containing several saccharide molecules and oxygen atoms linked to the sugar moiety can bind REEs; therefore, it is possible to prepare complexes that are stable and homogeneous. The total content of REEs in the complex is 35 times higher 35 than that in the extract (Table 1) . The main REEs present in the complex are Ce, L a , P r , and Nd, accounting for about 97 % of the total content of REEs .
2. 2
Degradation of organophosphorous pesticides using extract and its complex in neutral solvent
It is found that on cleavage of phosphodiester bonds, the activity of REEs was overwhelmingly higher than that of other metal ions. Recently, the authors have reported that the complex of algae polysaccharide
and Ce4' can cleave plasmid DNA and hydrolyze chlorpyrifos"O1. Table 1 shows that the extract and its complex contains larger amounts of REEs, which suggests that the extract and its complex with RE can also hydrolyze organophosphorous pesticides . However, thus far, there has been no report on the hydrolytic activity of R E . To confirm the above speculation. the degradation of chloropyrifos , omethoate , dichlorvos , and dimethoate in neutral solvent were carried in sealed glass tubes, respectively, using the extract and its complex with R E . The results show that the extract and its complex with RE can degrade chlorpyrifos , dichlorvos, omethoate , and dimethoate (Table 2 ) . The residues of the pesticides treated using the extract decrease by 96. 88% , 52. 30% , 4 9 . 5 2 % , and 2 2 . 8 8 % , respectively, for chlorp! rifos , dichlorvos, omethoate , and dimethoate, and those treated using the complex decrease by 95. 99% , 54. 23 ?k , 4 8 . 7 9 % , and 25.66% , respectively, when compared with those in control. It is evident that the effluence resulting from the degradation of chlorprifos using the extract and its complex is overwhelmingly higher than that of other organophosphorous pesticides ; however, there is no difference between the extract and its complex with RE in vitro for degrading the pesticides.
Degradation of organophosphorous pesticides in spinach using the extract and its complex with RE
2. 3
Seaweed liquid fertilizer and RE has been applied Table 2
Degradation of organophosphorous pesticides in neutral solvent using the extract and its complex with RE(mg.L-') Dimethoate
*
Dichlorvos
Omethoate
8.26 k 0.57
Control
4.72 0.58
6.52 k 0.45
Extract
3.64+0.35
3.11 *0.35* * 4.17k0.36'
Chlorpyrifns
24.06 k 0.88 0.75k0.21" *
3.51k0.45" 2.98-0.32"" 4.25+0.55" 0.96k0.31"" P < 0.05 ; * * P < 0.01 ; The degradation of the pesticides in neu-
Complex
*
tral solvent was carried out in sealed glass tubes. The contents of the pesticides were analyzed using gas chromatography ( C,C 1 . Data are expressed as means f S . D. of n = 3 .
97
Wang D F et a1 . Degradation of Extraction from Seaweed with RE for Organophosphorous Pesticides
to agricultural i:rops in China to increase crop yield. It is found that the extract arid its coniplex with RE can degrade organcrphosphorous pesticides in neutral solvent. which sLggests that the!- can be used both for increasing agricdtural productivity and reducing pesticide residues. In this stud!-, emphasis is being laid on chlorpyrifos and dimethoate, as they are the most commonl!- used peiticides in spinach production. The results show that spraving with the extract and the complex can signi icantly degrade chlorpyrifos arid dimethoate in the sainach ( Fig. 1 ) . The data in Fig. 1 indicate that the residues of chlorpyrifos ar d dimethoate in spinach obtained from the plots spra!i.d with the extract decrease by 16.60% and 16.33% , respectively, when cornpared with those in spinach obt iined from the control plots when the interval between spraying and sampling is 2 d . It decreases by 6 5 . 4 6 7c and 47.34% , respectively, when the interval be tween spraying and sampling is 8 d . The resic ues of chlorpyrifos and dimethoate in spinach obtained from the plots spra>-ed with the complex were 0 . 35 and 0 . 97 mg k g - ' , respectively, whereas 9 . 09 and 3. 973 mg k g - ' in spinach from control plots 1. hen the intenal between spraying and sampling was 3 d . The residues of chlorpyrifos and dimethoate decri-ases b y 90.64% and 76.56% , respectively, when compared N-ith those in spinach from control plots. It i,, evident that the degradation of the pesticides in v i m using the complex is better than that of the extract. To facilil ate statistical analyses, the conceritrations of residues were plotted against time for each data set (Table 3). and the first-order kinetics were determined for b ith chlorpyrifos and dimethoate. The co-
efficient of determination ( R 2 ) was > 0.92 in all case s , proving the quality of fitting. The calculated firstorder kinetic parameters show that chlorpyrifos and dimethoate exhibited the highest values of half-life period ( t l i z ), 4.748 and 4 . 5 2 9 d , respectively, when the spinach was sprayed with water as control, whereas the pesticides exhibited the shortest values of half-life period, 2.126 and 2.616 d , respectively, when the spinach was sprayed with the complex.
2 . 4 Effects of complex on yield of vegetables and contents of organophosphorous pesticides residues Brassica chinensis and cabbage are vegetables that are common in China. 'Their growth season usually corresponds to the season during which diseases and insect pests are prevalent. At present, organophosphorous pesticides, such as omethoate and chlorpyrifos , have been widely used to protect the vegetables from Table 3
e
Equation and t1,2of chlorpyrifos and dimethoate of spinach sprayed with the extract and its complex with RE'
Experiments
Equation
K2
t iizld
Dimethoate Control Extract
~= 17,94e-n m X
y = 16.575e-n.?3'
0.9224 0.9944
4.529 3.258
Complex ChlorpTifos
y = 20.197
0.9545
2.616 __-
Control
y = 28.538 e ' 5 3 4 r 7 ~ 3 0 . 4 9 4e - " 282ir y = 3 4 , 4 1 e-".43Mx
0.9623
4.748
0.9903 0.9743
2.815 2.126
~~
~~
~"
Extract Complex x
162x
,-@
R2 = coeffirient of determination;
tl,?
= half-life period
20
2
4
6
8
Ob
2
4
6
8
Aftcr spraying ;d ARcr spraying id Fig. 1 Etfects i i spraying with extract and its complex with Kli on degradation 01 chlorpyrihs ( a ) a i d dirrirtliu& ( h ) i n spinach ( Spinaches were separatelv spraved with dimethoate and chloropyrifos . Two days later, the spinaches were separately sprayed with the extract. its corniilp\ with K E , and water as control. The spinaches were randomly picked up from the same plots immediately after spraying and the!- w r e anaiyzed after 2.4.6, and 8 (1. Data are expressed as means ? S . I). of n = 3 samples on the basis of fresh weight)
JOURNAL OF RARE EARTHS, Vol. 2 5 , N o . 1 , Feb . 2007
98
the damage caused by insect pests in China because they are cost-effective easily available, and display a wide spectrum of bioactivity although some new molecules, which are biodegradable, have low toxicity to mammals and have low residual life, are being developed. Fig. 1 indicates that spraying with the complex can evidently decrease the residues of chlorpyrifos and dimethoate in spinach. To further prove the effects of the complex on the residues of organophosphorous pesticides and the yield of vegetables and acting as a novel method both for increasing productivity and reducing pesticide residues for vegetables production. The effects of the complex were studied on Brassica chinensis and cabbage. The results showed that spraying with the complex could both increase the yields of Brassica chinensis and cabbage and decrease the resi-
dues of the pesticides (Tables 4 and 5 ) . The fresh weight increased by 28.62% and 1 8 . 7 2 % , and the dry weight increased by 4 4 . 4 9 % and 1 4 . 7 4 % respectively, for Brassica chinensis and cabbage when compared with those of the controls. Table 4 Effects of spraying of complex on vegetable yield (8)* EXpennmh-
BrBsica chinensis
cabbage
Fmh weight
Fresh wreight
~
Dry wei&t
Dry weight
~~~
Contml Chmplex
873.2+852.6 5l2.3k57.5 11240.3k76.7 740.2+6$.3
25461.8k 7m.O 148.5*119.3 32%.1i '50.0 1641.3 k 37.2
*
Vegetables were sprayed with the complex and water as control, respectively. Samples were randomly picked up from the plots at 24 d later, and then the weight of the samples was measured immediatel? . Each treatment w a s repeated 4 times (different plots) , and all the plots were subjected to the same management practices. Data are expressed as means & S . D . of n = 4
#
Table 5 Contents of pesticide residues in vegetable at 3 and 5 d after spraying with complex (mg-kg-' f.wt) * Brassica chinensis Expenments
Dimethoate 3d
Control
0.29k0.04
Water Complex
Cabbage
~
-~
Sd
Chlorpymfos 3d
5 d
Dimethoate 3d
0.2220.06
1.81k0.53
0.99&0.09
0.03k0.01
5d 0.04+.0.01
0.26k0.06
0.22r0.04
1.64r0.21
0.76k0.27
0.03r0.02
0.27k0.05
0.11r0.03"
1.17*0.11
0.63&0.17"
0.03k0.03
_
_
_
_
_
Chlorpynfos 3rl
5d
O.lOkO.04
0.10+0.04
0.03&0.02
0.07kO.06
0.06kO.W
0.01+0.01*
0.03k0.01"
0.06kO.05
*
P < 0.05 ; The vegetables were sprayed with dimethoate and chloropyrifos, and 1 d later, they were sprayed with the complex and water, or neither as control. Samples are randomly picked up from the plots at 3 d and 5 d later, respectively, .and then the residues w'ere analyzed imine
The residues of chlorpyrifos and dimethoate in Brasscia chinensis and cabbage sprayed with the complex are smaller in percentage compared with those sprayed with water or with those that were not treated. The residues of chlorpyrifos and dimethoate in brasscia chinensis decrease by 36.36% and 5 0 . 0 0 % , respectively, at 5 d after spraying the complex, when compared with those in the vegetable from control plots and in cabbage where the residues decrease bv
ral Science ) , 2003, 1 : 28. [ 31 Zheng H X , Xu G M , Feng C .
[4]
[5]
Y
40.00% and 75.00 % respectively. It is evident that spraying with the complex can both increase the yields of vegetable and decrease the residues of organophosphorous pesticides. However further investigation should be carried out to know the mechanism by which the complex derived from the extract and RE increases crop yield and decreases pesticide residues.
[6]
[7]
[ 81
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n-