Influence of Pesticide Metabolites on the Development of Enhanced

Chapter 10

Influence of Pesticide Metabolites on the Development of Enhanced Biodegradation L. Somasundaram and Joel R. Coats

Downloaded by UNIV LAVAL on May 16, 2016 | http://pubs.acs.org Publication Date: May 3, 1990 | doi: 10.1021/bk-1990-0426.ch010

Department of Entomology, Iowa State University, Ames, IA 50011 Adaptation of soil microorganisms for rapid degradation of soil-applied pesticides can occur as a result of the complex interactions between the s o i l , the pesticide, the microbes, and environmental conditions. The current research addresses the role of breakdown products from the pesticide in the development of the condition. Several factors that influence enhanced microbial degradation include: nutrient value of the metabolite molecule, toxicity of the metabolite to soil microorganisms, and the availability of the metabolite to soil microbes. Comparisons of several pesticides, and their respective degradation products provide insight into the question of why soil microbial populations can develop rapid degradation capabilities for some pesticides but not others.

Enhanced

microbial

interaction, primary

degradation

influenced

factors,

influencing

these

factors

enhanced

several

ecosystems,

essential Many microbes (14) the

on

studied

including

turf

researchers (10,11),

the in

application properties degradation

grass

understand

that

detail. to of

the

have

the

also

Because

been (1),

and

them

metabolites

the

to

(2), dips

are

may

(3),

(7),

is

of

13),

and

it

phenomenon. soil

also

(8,9),

environment

The p r o p e r t i e s have

metabolized a

in

sorghum

role

short

not after

time,

influence

been the

the

significantly.

N O T E : T h i s chapter is J o u r n a l Paper N o . J - 1 3 7 9 4 o f the Iowa Agriculture and H o m e E c o n o m i c s Experiment Station, A m e s , I A . Project N o . 2306.

0097-6156/90/0426-0128$06.00/0 ©

these

process.

occur

this

degradation within

to

practices

degradation

pesticides.

enhanced of

corn

(12,

pesticides

some

the

cattle

practices of

addition

reported

influencing

investigated

degradation

pesticide

process

rice

In

a n d management

affect

has

(6),

influence soil,

soil-pesticide-microbe factors.

factors

factors

management

enhanced

pesticides

may

a

three

biodégradation

(4,5), to

is

a l l

environmental

Because

vegetables

by

1990 A m e r i c a n C h e m i c a l Society

Racke and Coats; Enhanced Biodegradation of Pesticides in the Environment ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

of

10.

Pesticide One or

of

Properties

the

microbes

pesticides microbial

to

ability

the

of

for

the

that

pesticide

the

pesticide

microbes

utilize

of

utilizable

The

presence

of

more

(e.g.,

2,4,5-T

microbial The the

availability whether s h o u l d be

or

microbial

Pesticide

completely to

is

an is

in

result

their

pesticide

nutrient

source

(15-

property

biodégradation.

largely

in The

determined

nitrogen

ring

the

to

in

important

enhanced

by

hydrolysis, hydrolysis pesticide

are

followed

as

degradation needs

by

moieties.

structures

number o f

(e.g.,

halogens

in

resistance

to

is

a

factor

to

enhanced

to

on

their

to

energy

parent

Condition

of

are

the

pesticides, an

initial

and u t i l i z a t i o n sources. of

are their

Pesticide

involves

of

The e f f e c t

subsequently

The p r o p e r t i e s

value,

may b e

different

reactions

well.

fate

nutritive

microbes

Metabolites

as

the pesticide.

period after

metabolism

usually

be a

through

hydrolytic

the

to of

their

low

and p h o r a t e ,

short

understood.

as

seem

degraded

metabolism or

suitable

availability,

value

important

microbes

of

exert

a

general,

better

soil

a

to

microbial

further

degradation

of

In

such

as

terbufos

within

nutrient

be

serving

degradation

as

the

or

in

The

microorganisms

nutritive

such

critical

biodégradation.

Thus,

enhanced

products

metabolites

availability

value.

often

by

the

are

soil

soil

microbes

to

them,

in

adapted

products

pesticides

the

Pesticides

(18).

ones

in

enhanced

metabolized

oxidations

catabolism

to

favor

of

soil

significant

Potential

some

saturated

pesticides

and h i g h

could

a n d some

application

of

to

could

available

Metabolites.

mechanisms,

pesticide

of

carbon or

increase

nutrient

toxicity, that

of

toxic

provide

properties

although

an

inhibition of

substrate,

most

the

The r e s i s t a n c e attributed

a pesticide

and t e f l u t h r i n )

pesticides,

almost

a

induction to

involved

value

the

toxicity

carbon and o r g a n i c

recalcitrant or

their

adaptation.

induction or

toxicity

as

nutritive

presence

and molinate)

is

may b e

susceptible

to

may i n f l u e n c e

microorganisms

129

Biodégradation

degradation.

adaptation

Soil

utilize

that

biodégradation

the

cycloate


microbial

Enhanced

pesticides

responsible

reflecting

rendering

of

enhanced

toxicity.

catabolism 17),

Influencing

properties

inhibition of

soil

and

Influence ofMetabolites on Degradation

SOMASUNDARAM & COATS

of

microbial

critical

in

of

applied toxicity,

the

induction

compounds.

Soils

for

Enhanced

Biodégradation The in

presence

parent the

of

for

we

pretreated

compound f o r

A clay

loam in

pretreated

a hydrolysis

1,

the

the

a

the 3,

product.

of

and 4

in

role

of to

times,

A week

was at

after

metabolites 4

(in

times

subsequently

organic

5 years

and in

weekly last

(19,20) of

in

and

their

conditioning

nonflooded

with

a

hydrolysis 1 4

applied

C-labeled

herbicides.

matter used

the

soils

degradation

compounds

up

the

rice

rapid

insecticides

(pH 6 . 5 , last

flooded

parent soil

fate

several

soil

in

resulted

respective

and s t u d i e d

any p e s t i c i d e

has

To a s s e s s

their

situations), parent

(21)

compounds.

soil

product

was

some m e t a b o l i t e s

c r a n b e r r y bogs

3.4%) this

not

treated

study.

intervals,

This

with

pretreatment,

with soil

5 ppm a l l


the

of

130

ENHANCED BIODEGRADATION O F PESTICIDES IN T H E ENVIRONMENT

treatments pesticide and

were and

surface-treated

incubated

metabolism

studies

for have

2.4-Dichlorophenoxyacetic dichlorophenol,

* C-2,4-D being

compared w i t h At

end

in

the

increase bound

3% i n

the

residues

pretreatments similar

documented

that 1 4

of as

increased such for

product

rapid

Prior

of

parathion

1 4

C0

1 4

to

2

to

the

of

as

2

there

was

The p o t e n t i a l

Acid.

a in

acid of

of

2,4-D

1 4

condition

C-2,4,5-T

of

soils

The amount

of

number

of

(Table

I).

degradation

applied

to

U

C0

of

to

4

p a r a t h i o n was

Sudhakar-Barik

et

al.

microbes

in

with

(19)

soils

d i d not

diazinon

for

degradation in

rice

the

we

studied

The In

serving

of

carbofuran

phenol.

II).

to

no

has

soil-bound

the

for

the

low

d i d not

hydrolysis

enhanced microbial in

this

predispose

reported

microbes

of

p-nitrophenol.

Enhanced b i o d é g r a d a t i o n

contain

residues

enrichment

with

elsewhere

been p r e v i o u s l y

d i d not

degradation with

the as

inducer,

its

(1).

capable

flooded is

but

soils

A bacterium

carbamate

side

secondary

hydrolysis

microbial

substrate.

1 4

of

of

rice

of

soils

source)

soils of

Evidently, adapting

for

pretreated been

product

the

up

to

4

of

(17).

carbofuran,

of

with the

phenol

may

of

serve

carbofuran amine,

the

as

degradation

N-methyl

Methyl may b e

phenol

degradation

enhanced

times

nitrogen

isolated of

the

affected

carbofuran

carbofuran phenol

evidence

not

carbofuran

India,

enhanced

that

f o u n d no

utilizing

c h a i n has

c a r b o f u r a n was product,

possible we

C-ring

hydrolysis

an energy

It

in

diazinon.

(Table nearly

p-nitrophenol

soils

Despite

(discussed

of

in

p-nitrophenol

observed

the

hydrolysis

degradation.

(20).

enzyme

of

soils

pretreated

III).

a

p-nitrophenol,

treated

hydroxypyrimidine metabolite

diazinon

an

(Table

availability

the

carbofuran

condition

the

increased

with

with

converted

soils

chapter),

Carbofuran.

as

mineralization

evolved

times

in

enhanced

the

2,4,5-

p-nitrophenol,

2

39%

and h i g h

(without

in

for

serve

2-Isopropyl-6-methyl-4-hydroxypyrimidine,

(Table

acid

soil

The

d i d not

increased

pretreatments

up

compared w i t h

of

soils

soil-

been

the

diazinon,

in

(Figure

structurally

has

Diazinon.

diazinon

the

and v a n i l l i c

product

soil

of

proportionate

2,4,5-Trichlorophenol,

d i d not

in

parathion-hydrolyzing

rapid

76%

as

2,4-dichlorophenol

degradation

resulted

pretreated

pretreatment.

toxicity

in

3 days,

2,4-dichlorophenol

2,4-dichlorophenol,

exposure

C0 .

soils

two-thirds and

2,4-

substrate.

parathion,

proportion In

with

within

2

incubation

resulted

and decrease

of

I).

2,4,5-T,

unlike

microbial

Parathion.

II) .

of

b i o d é g r a d a t i o n of

trichlorophenol,

product

no

evolved

2

soil

2,4-D,

C0

protocatechuic

2.4.5-Trichlorophenoxyacetic

suitable

U

to

number

(Table as

of

soil

(22).

(£3).

hydrolysis enhanced

Pretreating product

parent

of

elsewhere

incubation,

C0

the

C-labeled

The d e t a i l s

received

3-week

amount

soils

Acid.

soil

the

given

mineralized

the

formed

compounds

conditioning


of

been

hydrolysis

4

applied I) .

the

with

3 weeks.

a

preferred



14

1 4

2

F i g u r e 1. E f f e c t o f no p r e t r e a t m e n t ( 0 ) , one, t h r e e , and f o u r p r e t r e a t m e n t s o f 2 , 4 - d i c h l o r o p h e n o l on the e v o l u t i o n o f C 0 from [ C]2,4-D-treated soil.


h* U> h*

Ι

δ-

I

§

! I

I

S

β» ο

2

C2

en

Ο

ρ


co

2

e

d

" Means

e

in

each

e

Includes

volatile

products

in

99 . 1 7

0 .62

76 . 0 2

21 . 7 5

0 .55

0 .22

same

a

a

letter

than

a

b

b

b

a

a

c

a

b

a

a

a

b

as

a

e

e

a

a

b c

0

polar,

different

b

a

b

a

a

b

2,4,5-T)

2,4-D)

at

level

b

a

b

a

a

b

b

a

e

d

d

a

a

products.

5%

93.. 4 6

0. . 6 3

5. . 2 9

29.. 4 7

36. , 2 1

6. 3 0

15. . 7 5

103. , 0 6

0. , 4 0

90. 0 1

13.. 1 8

0. . 5 3

0. . 2 6

4

products

water-soluble

93.. 4 7

0. . 8 1

5. , 1 9

30. . 4 7

36. , 5 2

3

15. . 1 6 ab 5.

(from

101. , 0 5

0. , 4 7

81.. 4 7

18. , 5 2

0, . 4 0

0, . 1 8

(from

the

pesticide

by

hydrolysis

significantly

well

not

^ C O o as

are

87 . 6 0

0 .96

5 .58

30 . 2 1

30 . 6 2

15 . 3 7

a

a

3

with

applied

2,4- Dichlorophenol

4 .85

a

% of

pretreatments 1

influenced

2,4,5- Trichloropheno 1

of

recovered,

as

products

soil

hydrolysis

a

a

a

a

a

a

a

a

other

the

99.. 1 0

0. . 7 4

9. . 2 6

Test).

row w i t h

(Student-Newman-Keuls

a

Total

Others

2

30. , 9 4

Soil-bound

co

35. , 9 1

2,4,5-Trichloroanisole

14

4. . 4 1

17. . 8 4

101. , 0 5

0. , 8 7

69., 8 8

2,4,5-Trichlorophenol

2,4,5-T

Total

Others

14

29.. 4 6

0, . 6 3

Soil-bound

2,4-Dichlorophenol

0

Number

of

pesticides

pretreatment

Degradation of

0. . 2 1

I.

2,4-D

Fractions

Table


Χ Ο

5

Η

2

Β

Β

q

ι

as ο

Ο

1

3 δ

§

η

M


of

% of

influenced

94 . 0 8 a

18. . 1 6 0. . 7 7 13.. 0 3 93, . 8 3

a

a

a

a

18, . 7 3 18, . 1 8 1, . 0 4

a

a

a

18. . 4 3 19, . 5 9 0, . 9 5

Soil-bound

at

a

a

14, . 1 7 a

39.. 8 5 22. . 0 0

a

37, . 5 8

a

37, . 9 0

Diazinon

Hydroxypyrimidine

2

4

c o

2

Means

0

in

each

e

Includes

volatile

Test). other

than

^ C 0

2

are

a

as

as

polar,

significantly

well

not

89 . 7 3

same

89 . 2 9

a

12, . 8 5

the

13, . 7 4

Hyd r o x y p y r i m i d i n e

a

products


a - d i

Total

Others

1

Total

e

water-soluble

different

a

a

b

a

b

a

Diazinon)

101. , 1 0

a

96. . 2 6

a

96. . 7 0

c o

(from

2. , 6 8

a

1. , 9 1

a

1. 6 9

4

products.

level

a

5%

a

a

0, . 9 5

2

19, . 8 5

5

38, . 5 9 ab 20,

a

b

3.. 0 6 101. . 6 5

30. . 6 5 °

25., 5 7

a

13., 1 3

a

12. , 2 8

1

Others

b

d

b

3.. 2 9 30. . 8 0

b

2. , 8 4 29. 8 5

Soil-bound

p-Nitrophenol a

1. . 7 8 27. 2 7

a

0. , 7 5 26. , 9 6

d

33.. 8 4

c

55. 0 1 c

Parathion

40. , 8 7

4

products

b

Parathion)

hydrolysis

pesticide

the

b

(from

with

applied

by

52. , 1 4

p-Nitrophenol

3

pretreatments 1

as

products

soil

recovered,

letter

of

in

hydrolysis

a

0

Number

l^C

of

pesticides

pretreatment

Degradation

row w i t h

II.

a

Fractions

Table



co

2

e

a

a

a

a

a

a

1

93.. 0 7

1. . 1 4

3., 3 8

12. . 5 2

1, . 7 5

74, . 2 7

d

~ Means

in

each

e

Includes

volatile

products

a

same

a

other

the

98. , 2 7

Test).

row w i t h


a

Total

11. 7 9

letter

than

^CC>2

are

a

a

a

b

a

b

phenol

a

a

b

b

a

b

as

3

as

b

different

a

a

b

e

a

at

water-soluble

97, , 8 7

13, . 0 9

0. . 5 9

3., 6 9

0, , 8 8

polar,

a

a

a

b

a

a

1, . 4 1

75, . 2 0

93.. 5 4

0, , 7 8

3, . 0 8

13, . 0 6

level

a

a

b

d

a

e

a

a

a

b

a

b

products.

5%

99.. 6 5

10. , 4 0

0. , 6 0

2. . 8 3

0. , 7 3

85. . 0 8

Chlorpyrifos)

79, . 6 1

(from

96. . 2 7

0. . 5 8

3, . 2 7

13, . 2 5

1 .67

77 . 4 8

4

products

pesticide

the

hydrolysis

by

(from Carbofuran)

with

applied

significantly

well

not

96. , 0 0

10. . 7 1

0. . 7 6

e

4. . 7 2

a

5. . 7 2

0. , 7 3

79.. 0 8

a

a

a

6. , 1 9

73.. 7 8

Soil-bound

Others

% of

products

influenced

pretreatments

Carbofuran

of

as

hydrolysis

recovered,

of

pesticides

3,5,6 - T r i c h o l o r o - 2 - p y r i d i n o l

92. , 5 6

0. . 5 8

2, . 7 5

10. . 8 4

1, . 3 8

77, . 0 1

0

Number

l^C

pretreatment

Degradation of

0. , 7 8

III.

3,5,6-T-2-pyridinol

Chlorpyrifos

Total

Others

1 4

Soil-bound

3-Ketocarbofuran

Carbofuran

Fractions

Table


Η

Ο

Μ Μ

as

Η

3 Β 2

η

*J

Ο

δ

1

ο

3 δ α w

Ο M Ο

S3

10. SOMASUNDARAM & COATS Chlorpyrifos.

Prior

the

product

hydrolysis

chlorpyrifos was

about

5

pretreated

(Table to of

isofenphos 4

in

the

IV).

was

with

structurally

salicylic

this to

chapter),

its

to

acid, in

two-thirds

at

of

the

residues

the

end

the

in

of to

The a b i l i t y

of

(24),

been

availability value

condition

of

soils

(as

in

incubation to

3,5and

5-

reported.

The

low

later

a c i d may

enhanced

3

the

soils

discussed

salicylic

for

of

microbes

acid

relative

pretreated

3-week

65%

3,6-dichlorosalicylic has

degradation

soil

the

34

benefit

secondary

percent

as

their

its

applied

such

to

pyridinol-

with

enhanced

Seventy-eight

acid.

in

of

there

Increased

pretreated

compared w i t h

and n u t r i t i v e

potential

recovered

soils.

salicylic

soil-bound

similar

persistence

incubation,

compounds

(25)

toxicity,

soil

the

3-week

resulted

acid.

as

a

literature.

to

recovered

pretreated

chlorosalicylate

in

Nearly to

increased

of

control

the

soils

treatment

dichlorosalicylate,

end

isofenphos,

metabolize

microbial

to

135

3,5,6-trichloro-2-pyridinol,

chlorpyrifos

compound

salicylic

isofenphos

the

in

new

converted

with

control

At

of

of

(Table

was

times

applied

is

Exposure

isofenphos

and

a parent

product

of

chlorpyrifos,

compared w i t h

product

of

of

increase

degradation Isofenphos.

applications III).

as

persistence

hydrolysis


10%

soils


in

contribute

degradation

of

isofenphos.

Table

IV.

Degradation

of

pesticides

pretreatment

C

of

recovered,

as

influenced

hydrolysis

% of

by

the

products

applied

C

pesticide

Fractions Number

of

pretreatments

0

1

Isofenphos

oxon

Soil-bound 1 4

co

2

Others

e

Total

a _ d

Means

in

different e

Includes

soluble

each at

products

acid

4 (from

Isofenphos) c

78. . 0 4

a

65, . 3 0

b

36, . 8 1

c

33. . 6 9

8. , 9 5

a

7, . 8 1

a

5, . 3 5

b

4. . 4 3

b

8. . 7 5

a

12, , 3 4

b

21, . 3 2

c

24. . 9 0

d

38. . 7 2

3.. 9 1

a

9, . 9 3

b

34. . 4 7

c

0. . 3 6

a

0. . 4 2

a

0. . 2 6

a

0. , 3 3

a

100. .02

a

95. . 8 1

a

98. . 2 2

a

102. . 0 7

a

row w i t h

5% l e v e l

volatile

hydrolysis

3

Salicylic Isofenphos

with

the

same

letter

are


products

other

than

1 4

C0

2

not

significantly

Test). as

well

as

polar,

products.


water-

d

136

ENHANCED BIODEGRADATION OF PESTICIDES IN T H E ENVIRONMENT

Microbial

Toxicity

The Beckman M i c r o t o x system was employed t o a s s e s s the r e l a t i v e t o x i c i t y o f p e s t i c i d e s and t h e i r h y d r o l y s i s p r o d u c t s t o b a c t e r i a . T h i s system u t i l i z e s Photobacterium phosphoreum, a marine b i o l u m i n e s c e n t bacterium p h y l o g e n e t i c a l l y r e l a t e d to s e v e r a l genera of b a c t e r i a important i n s o i l . The M i c r o t o x system measures the l i g h t e m i t t e d from P. phosphoreum t h a t have been exposed t o a c h e m i c a l d i s s o l v e d i n the d i l u e n t . The d e t a i l s o f t h e o r y and o p e r a t i o n o f M i c r o t o x a n a l y z e r and e x p e r i m e n t a l c o n d i t i o n s u s e d have been d e s c r i b e d (26-28). The h y d r o l y s i s p r o d u c t s o f some p e s t i c i d e s s u s c e p t i b l e t o enhanced d e g r a d a t i o n ( i s o f e n p h o s , d i a z i n o n , c a r b o f u r a n ) y i e l d e d higher EC v a l u e s , r e f l e c t i n g t h e i r low t o x i c i t y t o b a c t e r i a ( T a b l e V). C o n v e r s e l y , some p e s t i c i d e s w i t h l i t t l e o r no p r o p e n s i t y f o r enhanced biodégradation y i e l d h y d r o l y s i s p r o d u c t s t h a t show c o n s i d e r a b l e a n t i b a c t e r i a l a c t i v i t y ( c h l o r p y r i f o s , 2,4,5-T). However 2 , 4 - d i c h l o r o p h e n o l and p - n i t r o p h e n o l , w h i c h a r e r e p o r t e d t o s e r v e as energy s o u r c e s t o s o i l m i c r o b e s , a l s o r e c o r d e d a low E C value. The t o x i c i t y o f h y d r o l y s i s p r o d u c t s t o P. phosphoreum may not correspond to t o x i c i t y to s o i l b a c t e r i a i n a l l i n s t a n c e s , b u t d a t a i n d i c a t e t h a t s u s c e p t i b i l i t y t o enhanced d e g r a d a t i o n may be p a r t l y i n f l u e n c e d by the t o x i c i t y o r l a c k o f t o x i c i t y o f the h y d r o l y s i s products to b a c t e r i a .


5 Q

5 0

T a b l e V.

The

t o x i c i t y o f p e s t i c i d e s and t h e i r h y d r o l y s i s p r o d u c t s d e t e r m i n e d w i t h the M i c r o t o x system

Pesticide

E C

2,4-D 2,4,5-T parathion chlorpyrifos carbofuran

100. 51. 8. 46. 20.

67 63 51 25 52

isofenphos

97. 81

diazinon

10. 30

Availability

product

EC 50

2,4-dichlorophenol 2,4,5-trichlorophenol p-nitrophenol 3,5,6-trichloro-2-pyridinol carbofuran phenol methylamine salicylic acid isopropyl salicylate 2-isopropyl-4-methyl-6-pyrimidine

5,.0 1,.77 13,.74 18,.58 60,.92 34..64 213. .92 5..62 886. .42

Hydrolysis

50

as

o f P e s t i c i d e s / H y d r o l y s i s Products

in Soils

A n o t h e r i m p o r t a n t v a r i a b l e t h a t d e t e r m i n e s the m i c r o b i a l m e t a b o l i s m o f s o i l - a p p l i e d p e s t i c i d e s i s the a v a i l a b i l i t y o f the c h e m i c a l t o the m i c r o b i a l systems d e g r a d i n g i t . The h y d r o l y s i s p r o d u c t and p a r e n t p e s t i c i d e s h o u l d be a v a i l a b l e t o m i c r o b e s so as t o e x e r t t h e i r t o x i c i t y or provide n u t r i e n t v a l u e . The l a c k o f a v a i l a b i l i t y o f some c h e m i c a l s may r e s u l t i n r e s i s t a n c e t o m i c r o b i a l a d a p t a t i o n .


10. SOMASUNDARAM & COATS



One l a b o r a t o r y a p p r o a c h t o the s t u d y o f a v a i l a b i l i t y i s the m o b i l i t y o f the p e s t i c i d e s on s o i l t h i n - l a y e r chromatography p l a t e s as a n i n d e x o f a compound's a d s o r p t i o n / d e s o r p t i o n b e h a v i o r . S o i l T h i n - L a v e r Chromatography. The s o i l t h i n - l a y e r chromatography t e c h n i q u e (STLC) was employed t o a s s e s s the m o b i l i t y o f p e s t i c i d e s and t h e i r h y d r o l y s i s p r o d u c t s i n s o i l . Because s o i l p r o p e r t i e s such as o r g a n i c m a t t e r , pH, and c l a y i n f l u e n c e t h e b e h a v i o r o f c h e m i c a l s i n s o i l , s i x t e x t u r a l l y d i f f e r e n t s o i l s w i t h a wide range i n o r g a n i c m a t t e r c o n t e n t (0.7 t o 6.1%) and pH (5.5 t o 8.5) were u s e d i n t h i s study. I n the STLC t e c h n i q u e , t h i n l a y e r s o f s o i l s e r v e a s the a d s o r b e n t phase and a r e d e v e l o p e d w i t h water b y u s i n g t e c h n i q u e s analogous t o c o n v e n t i o n a l t h i n - l a y e r chromatography ( 2 9 ) . R e l a b e l e d compounds were a p p l i e d as s p o t s on STLC p l a t e s and d e v e l o p e d w i t h d i s t i l l e d water by a s c e n d i n g chromatography. The d e v e l o p e d p l a t e s were exposed t o Kodak R o y a l B l u e X - r a y f i l m f o r 2 t o 3 weeks. The R v a l u e ( r e l a t i v e f r o n t a l movement) f o r each compound was measured as the f r o n t o f the s p o t o r s t r e a k i n the r e s u l t a n t autoradiogram (30). f

Mobility in Soils. C h l o r p y r i f o s was n o t m o b i l e i n any o f the s o i l s s t u d i e d , b u t i t s h y d r o l y s i s p r o d u c t t r i c h l o r o p y r i d i n o l was m o b i l e , e s p e c i a l l y i n loamy sand and s i l t loam s o i l s ( T a b l e V I ) . Parathion, d i a z i n o n , and i s o f e n p h o s were s l i g h t l y m o b i l e ( R < 0.25), and t h e i r h y d r o l y s i s p r o d u c t s were s i g n i f i c a n t l y more m o b i l e t h a n the r e s p e c t i v e p a r e n t compounds (p < 0.01). C a r b o f u r a n p h e n o l was more m o b i l e i n a l l s o i l s s t u d i e d (R 0.33 t o 0.68). 2,4-D was m o b i l e i n a l l s i x s o i l s s t u d i e d (R 0.56 t o 1.00), whereas i t s h y d r o l y s i s p r o d u c t , 2 , 4 - d i c h l o r o p h e n o l , was low t o i n t e r m e d i a t e i n m o b i l i t y . 2,4,5-T and 2 , 4 , 5 - t r i c h l o r o p h e n o l were n e a r l y immobile i n any o f the s o i l s s t u d i e d (R < 0.03). f

f

f

f

I m p l i c a t i o n s o f M o b i l i t y on the A v a i l a b i l i t y and D e g r a d a t i o n o f Pesticides i n Soil. Repeated a p p l i c a t i o n o f 2 , 4 - d i c h l o r o p h e n o l , p - n i t r o p h e n o l , and s a l i c y l i c a c i d (as o b s e r v e d i n c u r r e n t s t u d i e s ) and c a r b o f u r a n p h e n o l (20) has i n d u c e d enhanced m i c r o b i a l d e g r a d a t i o n o f t h e i r p a r e n t compounds. R v a l u e s o f t h e s e h y d r o l y s i s products i n d i c a t e intermediate to high m o b i l i t y i n s o i l s . The p - n i t r o p h e n o l , 2 , 4 - d i c h l o r o p h e n o l , and s a l i c y l i c a c i d were u t i l i z e d as energy s o u r c e s by m i c r o b e s , and t h e i r a v a i l a b i l i t y i n s o i l may c o n t r i b u t e t o the i n d u c t i o n o f r a p i d m i c r o b i a l m e t a b o l i s m . C a r b o f u r a n p h e n o l d i d n o t s e r v e as a m i c r o b i a l s u b s t r a t e b u t a l s o enhanced the d e g r a d a t i o n o f i t s p a r e n t compound, c a r b o f u r a n ( 2 0 ) . C a r b o f u r a n p h e n o l i s f r e e l y a v a i l a b l e i n a n a e r o b i c s o i l s , b u t the s i g n i f i c a n c e o f i t s a v a i l a b i l i t y i s y e t t o be u n d e r s t o o d . f

The m o b i l i t y d a t a f o r i s o f e n p h o s i n d i c a t e s t h a t , f o r a p e s t i c i d e t o be s u s c e p t i b l e t o enhanced d e g r a d a t i o n , the p e s t i c i d e n e e d n o t n e c e s s a r i l y be v e r y m o b i l e . A l t h o u g h i s o f e n p h o s has a low m o b i l i t y p a t t e r n , i t s s a l i c y l i c a c i d m e t a b o l i t e i s more r e a d i l y a v a i l a b l e to microorganisms. S a l i c y l i c a c i d i s a benzoic a c i d a n a l o g , and i t s h i g h a v a i l a b i l i t y i s s i m i l a r t o t h a t o f b e n z o i c a c i d and amiben ( 3 1 ) . Racke and Coats (11) s u g g e s t e d t h a t the f o r m a t i o n o f s a l i c y l i c a c i d d u r i n g i s o f e n p h o s m e t a b o l i s m i n s o i l may r e p r e s e n t a key f a c t o r i n the s u s c e p t i b i l i t y o f i s o f e n p h o s t o enhanced degradation. Our s t u d i e s w i t h s o i l s exposed t o s a l i c y l i c a c i d have


137

138

ENHANCED BIODEGRADATION OF PESTICIDES IN T H E ENVIRONMENT

confirmed the

this

salicylic

mobility

view. acid

and metabolism

isofenphos

may b e

microorganisms to

Some

pseudomonads

degradative studies

that

the

Table

M o b i l i t y of

six

indicate

resultant

microorganisms.

VI.

soils,

as

pesticides

determined

that

and

with

the by

their use

R

less

the

mobile

are

more

hydrolysis

of

carry

surface-soil

soil

value

f

to

from

available

products

TLC plates

in

product clay


reported

Observations

metabolites

Pesticide/ hydrolysis

been

(32).

h y d r o l y t i c a l l y metabolized

and

degrading

in

have

plasmid

loam

silty

sandy

loamy

silt

clay

loam

sand

loam

0, . 0 0

loam

loam

chlorpyrifos

0 .02

0 .02

0 .02

0 .02

0 . 02

t-pyridinol

0, . 2 6

0, . 2 6

0 .58

0 .36

0 . 94

1, . 0 0

0, . 1 0

0, . 1 0

0 .14

0, . 1 2

0 . 18

0, . 1 3

parathion p-nitrophenol diazinon hydroxypyrimidine isofenphos salicylic

acid

carbofuran carbofuran

phenol

2,4-D 2,4-dichlorophenol 2,4,5-T 2,4,5-T-phenol

The readily (33).

0, . 5 0

0, . 4 6

0 . 89

1, . 0 0

0, . 1 2

0, . 1 7

0 . 24

0, . 2 1

0, . 8 0

0. . 7 8

0, . 7 1

0, . 7 4

0 . 96

0. .81

0. .09

0. . 0 9

0, . 1 3

0, . 1 6

0 . 10

0. .16

0. .09

0. . 3 9

0, . 5 9

0. .35

0 . 75

0. .96

0. .57

0. .76

0. . 6 9

0. .77

0 . 81

0. .75

0 . 33

0 . .42

0. . 3 3

0. .63

0 . 68

0. .48

0 . .57

0 . 56

0. . 6 7

0. .68

1. 00

1. . 0 0

0 . .12

0. .11

0. .20

0. .14

0 . 58

0. ,46

0. ,00

0 . .02

0. .03

0. ,03

0 . 03

0. .00

0. ,00

0. ,00

0. .00

0. ,00

0 . 01

0. ,00

in

all

soils

Our M i c r o t o x s t u d i e s Availability,

m i c r o b i a l metabolism

enhanced

degradation

populations in

0, . 2 3 0, . 1 2

hydroxypyrimidine hydrolysis available

bacteria. to

0, . 1 5 0. . 1 0

our

of

degrading

laboratory

Chlorpyrifos microbes. mobile;

its

is

the

pyridinol-treated Both

2,4,5-T

unavailable

in

of its

and

this

is

of its

toxicity,

hydrolysis

parent

low

in

but

is

no

to

susceptibility

may

soils

more microbes

toxicity

and

product

compound

microorganisms,

diazinon

m i n e r a l i z e d by

demonstrated

microbial

immobile its

microbial to

have

low

product

favor

with

adaptation

was

noted

studies.

However,

contribute

of

tested

in

soil

and

is

pyridinol hydrolysis

toxicity

increased

not

and a v a i l a b i l i t y

persistence

of

available

product in

is

soil

chlorpyrifos

to

relatively may observed

in

soils. and 2 , 4 , 5 - t r i c h l o r o p h e n o l

soil,

indicating

their

low

are

relatively

availability

for

microbial

degradation.


10. SOMASUNDARAM & COATS Influence

of Soil

and t h e i r

loamy

and s i l t

hydrolysis loam

two

soils

The

pH h a s an i n d i r e c t

lower

stronger

mobility.

neutral faster

matter soils and

8.0).

soils clay

The i n c r e a s e d

contents.

because

of

the influence

organic

matter

data

of soil

versus

Silt

in

at

organic organic

loam and loamy

o f chemicals

content

i n these

pH and low o r g a n i c

of a state

to

to

two

enhanced

such

o f chemicals

sand (13.0

matter and

or country

characteristics

on the a v a i l a b i l i t y

weak

(36) a n d

greater

of pesticides

parts

by

resulting

is

movement

that

mobility.

the high

i n specific

(34,25),

( 0 . 7 a n d 1.2%) a n d c l a y

The s u s c e p t i b i l i t y

only

These

respectively.

(9).

availability to

i n the

used.

o f some p e s t i c i d e s

increased

indicated

retarded matter

soils

o f chemicals

of mobility

content

c o u l d be a t t r i b u t e d

degradation

to

o f the

mobile

and 8.5,

o n movement

soils

analysis

content

Most more

i n the other

adsorption

leading

h a d a low organic

were

a t low pH v a l u e s

i n alkaline

and clay

and clay

than

influence

regression

content

on M o b i l i t y .

products

p H ' s o f 8.3

adsorption

p H ' s and above,

Simple

high

In general,

degradation

matter

soils

had relatively

effecting


Characteristics

pesticides sand

Influence of Metabolites on Degradation

may b e

as pH a n d

microorganisms.

Conclusion Pesticide enhanced

degradation degradation

important

role

degradation products

i n the induction as g r e a t e r

value

in soils

with

o f these

findings

enhanced

make

directed

toward understanding

metabolites

of degrading

(primary,

as w e l l

as

we

i n which

resulting

the i n t e r a c t i o n secondary)

and

parent

microorganisms.

research,

research

microbial

toxicity,

or pesticide

source,

Future

for

an

degradation

of their

as a phenomenon

or nutrient

o f the pesticide.

of

low m i c r o b i a l

use o f the pesticide

as an energy

persistence

o f enhanced

degradation

and our r e l a t e d

soils

and could play

The p r o p e r t i e s

populations

microbial degradation

microorganisms products

or inhibition

enhanced

the

of conditioning

compounds

availability,

may f a v o r

compounds basis

are capable parent

o f some p e s t i c i d e s .

such

nutritive

products of their

adapted

soil

degradation

in

should

On

define

decreased

also

be

between microbes and

of

pesticides.

Acknowledgments This

research

Region Any

opinions,

authors

was s u p p o r t e d

Pesticide

Impact

findings,

by grants

Assessment

and conclusions

a n d do n o t n e c e s s a r i l y

agencies. Economics

Journal

reflect

Paper No.J-13794

Experiment

f r o m t h e USDA N o r t h

Station,

Ames,

Central

P r o g r a m a n d Dow C h e m i c a l C o m p a n y . expressed the views

are those o f the

o f the

granting

o f t h e Iowa

A g r i c u l t u r e a n d Home

IA, Project

2306.

Literature Cited 1. Sethunathan, N. Proc. Natl. Acad. Sci.(USA) 1971, 17(1). 18-19. 2. Rahman, Α.; Atkison, G.C.; Doughlas, J . A , ; Sinclair, D.P. Ν. Z. J . Agric. 1979, 139(3). 47-49. 3. Wilde, G.; Mize, T. Environ. Entomol. 1984, 13, 1079-1082. 4. Walker, Α.; Brown, P.A.; Entwistle, A.R. Pestic. Sci. 1986, 17, 183-193. 5. Harris, C.R.; Chapman, R.A.; Morris, R.F.; Stevenson, A.B. J . Environ. Sci. Health 1988, B23, 301-316.


139


140

ENHANCED BIODEGRADATION O F PESTICIDES IN T H E ENVIRONMENT

6. Niemczyk, H.D.; Chapman, R.A. J. Econ. Entomol. 1987, 80, 880882. 7. McDougall, K.W.; Machin, M.V. Pestic. Sci. 1988, 22, 307-315. 8. Abou-Assaf, N.; Coats, J.R. J. Environ. Sci. Health 1987, B22, 285-301. 9. Walker, A. Pestic. Sci. 1987, 21, 219-231. 10. Fournier, J.C.; Codaccioni, P.; Soulas, G.; Chemosphere 1981, 10, 977-984. 11. Racke, K.D.; Coats, J.R. J. Agric. Food Chem. 1987, 35, 94-99. 12. Abou-Assaf, N.; Coats, J.R.; Gray, M.E.; Tollefson J.J. J. Environ. Sci. Health 1987, B21, 425-446. 13. Somasundaram, L.; Racke, K.D.; Coats, J.R. Bull. Environ. Contam. Toxicol. 1987, 39, 579-586. 14. Chapman, R.A.; Harris, C.R.; Harris, C. J. Environ. Sci. Health 1986, B21, 125-141. 15. Cook, A.M.; Doughton, C.G.; Alexander, M. Appl. Environ. Microbiol. 1978, 36, 668-672. 16. Nelson, L.M. Soil Biol. Biochem. 1982, 14, 219-222. 17. Karns, J.S.; Mulbry, W.W.; Nelson, J.O.; Kearney, P.C. Pestic. Biochem. Physiol. 1986, 25, 211-217. 18. Harris, C.R.; Chapman, R.A. Can. Entomol. 1980, 112, 641-653. 19. Sudhakar-Barik; Wahid, P.A.; Ramakrishna, C . ; Sethunathan, N. J. Agric. Food Chem. 1979, 27, 1391-1392. 20. Rajagopal, B.S.; Panda, S.; Sethunathan, N. Bull. Environ. Contam. Toxicol. 1986, 36, 827-832. 21. Ferris, I . G . ; Lichtenstein, E.P. J. Agric. Food Chem. 1980, 28, 1011-1019. 22. Somasundaram, L.; Coats, J.R.; Racke, K.D.; J. Environ. Sci. Health 1989, B24, 457-478. 23. Kunc, F . ; Rybarova, J. Folia Microbiol. 1984, 29, 156-161. 24. Kruger, J.P.; Butz, R.G.; Atallah, Y.H.; Cork, D.J. J. Agric. Food Chem. 1989, 37, 534-538. 25. Crawford, R . L . ; Olson, P . E . ; Frick, T.D. Appl. Environ. Microbiol. 1979, 38, 379-384. 26. Anonymous, Interim Manual 015-555879; Beckman Instruments Inc.; Microbics Operations: Carlsbad, CA, 1979. 27. Bulich, A.A.; Greene, M.W.; Isenberg, D.L.; Aquatic Toxicology and Hazard Assessment: Fourth Conference 1981, ASTM STP 737, 338-347. 28. Somasundaram, L.; Coats, J.R.; Racke, K.D. Bull. Environ. Contam. Toxicol. 1990, 44, (2). 29. Helling, C.S.; Turner, B.C. Science 1968, 162, 562-563. 30. Somasundaram, L. Ph.D. Dissertation, Iowa State University, University Microfilms #90-03565, Ann Arbor, MI, 1989. 31. Bailey, G.W.; White, J.L.; Rotherberg, T. Soil Sci. Soc. Am. Proc. 1968, 32, 222-223. 32. Chakrabarty, A.M. J. Bacteriol. 1972, 112, 815-823. 33. Sethunathan, N.; Pathak, J. Agric. Food Chem. 1972, 20, 586-589. 34. Weber, J.B. Residue Rev. 1970, 32, 93-130. 35. Renner, K.A.; Meggitt, W.F.; Penner, D. Weed Sci. 1968, 36, 78-83. 36. Nicholls, P.H. Pestic. Sci. 1988, 22, 123-137. RECEIVED January 22, 1990


Influence of Pesticide Metabolites on the Development of Enhanced

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