A Field Study of Pesticide Pollution in Soil
Rajeev Yadav1*,
Dr. Devendra Kumar Namdeo2
1 Research Scholar,
Shri Krishna University, Chhatarpur, M.P.
ouriginal.sku@gmail.com
2 Associate Professor , Shri Krishna
University, Chhatarpur, M.P.
Abstract
The current work examines the
sublethal effects of four widely used pesticides on the gut histology and
enzymatic activity of the epigeic earthworm Perionyx excavatus:
pendimethalin, pretilachlor, dimethoate, and cypermethrin. Various biochemical
markers, such as acetylcholinesterase, alkaline phosphatase, and acid
phosphatase, were evaluated during field research in Madhya Pradesh's
Chhatarpur area to evaluate the physiological reactions of earthworms exposed
to these substances. According to the data, the levels of enzyme activity in
the treated samples were much lower than those in the control, with the effects
of dimethoate and cypermethrin being the most noticeable. In earthworms exposed
to pesticides, histological analysis of the chloragogen tissue lining the
intestine also showed obvious damage and distortion, with cypermethrin causing
the most tissue degradation. These results emphasise the need for more
environmentally friendly pest control techniques and the harmful effects of
agricultural pesticides on non-target soil species.
Keywords: Soil, Pesticides, Earthworms, Perionyx excavates, Enzyme.
INTRODUCTION
The xenobiotic assault by pesticides on ecosystems,
non-target species, humans, and civilisation began with this unfortunate event.
Written in the early 1960s by Rachel Carson, the fragile and melancholy
"Silent Spring" set out to show how organochlorine insecticides like
DDT had caused very negative consequences. In subsequent years, beginning in
1972, the use of pesticides containing organohlorine was outright banned in
most nations. However, the usage of synthetic pesticides did not decrease. [1]
organophosphates, carbamates, blended formulations,
and pyrethroids supplanted organochlrine as the primary pesticide. [2] Crop
output, both food and cash crops, has to rise to keep up with the world's
rapidly expanding population. Agriculture entered its modern age with the
introduction of high-yielding crop varieties, community farming, and new
technical equipment. Agrochemicals came into their own as a result of these
innovations, which paved the way for new farming techniques. [3]"Ecobichon"
was published in 2001. Higher application rates and ever-increasing potency of
insecticides were two of the many reasons that contributed to the pesticide
industry's meteoric rise to new heights of expansion. The farmers saw a quick
payoff for their efforts because of the abundant harvest. However, there were a
lot of pesticides in the environment. [4]
No one can deny the importance of pesticides in
reducing the harm that pests inflict to fruits and vegetables. [5] Ecosystems
have suffered greatly due to the careless and chronic use of various pesticides
over the last several decades. This is when environmental pollution became a
critically important issue. Testing various foods and water sources for
pesticide presence was one of the most important pieces of research. [6]
Pesticides in agricultural contexts disproportionately
impact earthworms, the most visible and vulnerable non-target soil organisms. [7]
They are particularly vulnerable to the pesticides used in agricultural
production because they make up a significant portion of the soil's
invertebrate biomassup to 92%. Numerous studies have shown the crucial role of
earthworms in nutrient cycling, litter decomposition, and soil formation. [8]
RESEARCH METHODOLOGY
Experimental investigation was conducted in Field studies.
·
Site
Selection For Field Data Collection
The Chhatarpur district in Madhya Pradesh, where SKU
is located, was the site of the field tests.
A hot tropical monsoon pattern describes the area
climate. Daytime highs may reach 40◦C, and the summer season begins in
April and continues until about the middle of June. The monsoon season, which
begins in the middle of June and lasts well into September, is responsible for
the majority of the annual rainfall of around 1500 millimetres. Winter, which
begins in December and continues until the beginning of March, often has
temperatures between 10 and 14 degrees.
·
Microorganism
Used For Testing
The species used for this investigation are the
epigeic earthworms Perionyx excavates.
Julika (1986, 1988) estimates that just over 500 species of earthworms call
India home. According to Chanda et al. (2003), the Chhatarpur district in
Madhya Pradesh is home to seventeen species that belong to two orders, six
families, and thirteen genera. A widespread species in India, Perinoyx
excavates is native to the Chhatarpur area.
An overview of the chosen
specimens' systematic placement and biology
Earthworms of the genus Perionyx and species Perionyx
excavatus are members of the following taxonomic groups: phylum Annelida,
class Oligochaeta, family Megascolicidae, order Haplotaxida.
The biology and
distribution of Perionyx excavatus
Perionyx
excavatus is the epigeic species of earthworm native to
India. This species is widespread in India, from the southern plains to the
northern Himalayas. Composite pits, locations for the disposal of organic waste
from homes and businesses, and other such organically rich systems are perfect
homes for Perionyx excavatus. Crop
fields that get sewage also contain this. The length, width, and number of
segments (125180) of a Perionyx excavatus may vary from 25185 mm, with
a diameter of 2.77 mm. At 280300 days, this species makes it through the
year. Earthworms spin tuft-like extensions inside their S-shaped cocoons.
"The juvenile," "non clitellate," and
"clitellate" are the three noticeable morphological stages that
earthworms go through after hatching.
·
Pesticides used
This investigation made use of four pesticides in a
variety of bioassays. The herbicides pendimethalin and pretilachlor, the
organophosphate insecticide dimethoate, and the pyrethroid cypermethrin were
the chemicals used. Indian farmers regularly apply all of these pesticides on
their crops. In the acute toxicity bioassay, all four insecticides were used.
To study the synergism between organophosphate insecticides and herbicides,
researchers examined the combined effects of the herbicide pendimethalin and
the organophosphate insecticide dimethoate on earthworm mortality. We
conducted chronic toxicity bioassays on all four pesticides after reviewing
their acute toxicity data and considering their eco-toxicological implications.
The pesticides utilised in this investigation may be found in Table along with
their sources of procurement.
Table 1: The study's pesticides
|
Sl.
No |
Pesticide
Group |
Chemical
Name |
Commercial
Name |
|
1 |
Herbicides |
Pendimethalin
(30% EC) |
DHANUTOP |
|
Pretilachlor
(50% EC) |
RACER |
||
|
2 |
Organophosphate
Insecticide |
Dimethoate
(30% EC) |
ROGORIN |
|
3 |
Pyrethroid |
Cypermethrin
(10% EC) |
USTAAD |
1. Pendimethalin
For the purpose of selective weed management in
various crops, pendimethalin is used. Pendimethalin is a non-ionic
dinitroalanine herbicide. According to Lee et al. (2000), it has a modest
persistence in soil. The chemical structure of pendimethalin is shown below,
and Table provides further technical
information on the herbicide.
Pendimethalin
Table 2: Some characteristics of pendimethalin
|
Parameters |
Properties |
|
Chemical
Name |
3,4-Dimethyl-2,6-dinitro-N-pentan-3-yl-alanine |
|
Chemical
Formula |
C₁₃H₁₉N₃O₄ |
|
Melting
Point |
4758°C |
|
Solubility |
Soluble
in water |
|
Stability |
Not degradable by
microbes; strongly adsorbed to organic soil materials and clay. Ninety days
is the half-life of soil. |
2. Pretilachlor
A selective herbicide belonging to the acetamide
group, pretilachor is used for the management of several annual grass and board
leaf weed species (Dharumarajan, et al., 2008). According to Asokaraja and Ali
(1995), Deepa (2002), and Tomoyoshi et al. (2004), it may be found in soil and
water for an extended period of time and can also build up in plant components.
The weather and the composition of the soil determine the residual
characteristics. The photodecomposition and volatilisation processes disperse
and deposit pretilachlor in the environment (Rai et al., 1999). The chemical
structure of the herbicide is shown below, and Table provides further technical
information regarding pretilachlor.
Table 3: Pretilachlor
Properties
|
Parameters |
Properties |
|
Chemical
Name |
2Chloro-N-(2,6-diethylphenyl)-N-(2-propoxyethyl)acetamide |
|
Chemical
Formula |
C₁₇H₂₆ClNO₂ |
|
Melting
Point |
4758°C |
|
Solubility |
Soluble
in water, benzene, hexane, methanol, etc. |
|
Stability |
Very stable in both water
and dirt. About ten days is the half-life of soil. |
3. Dimethoate
An organophosphate pesticide and acaricide, dimethoate
has several applications. As a class II moderately hazardous pesticide,
dimethoate is quite mobile in dirt. Although it is not often detected in high
concentrations in water, this pesticide is fairly persistent. But it's
poisonous to birds in moderate to high doses, aquatic creatures in moderate
doses, and honeybees in high doses (Gilbert, 2014). Although it degrades
quickly, it is easily taken and disseminated by plants (Dauetrman, 1960). The
chemical structure of dimethoate is shown below, and further technical
information is provided in Table.
Table 4: Dimethoate
Characteristics
|
Parameters |
Properties |
|
Chemical
Name |
O,O-dimethyl
S-[2-(methylamino)-2-oxoethyl] dithiophosphate |
|
Chemical
Formula |
C₅H₁₂NO₃PS₂ |
|
Melting
Point |
4345°C |
|
Solubility |
Mixable with water |
4. Cypermethrin
Pyrethrum is an all-natural pesticide derived from
dried Chrysanthemum flower heads; the active ingredient in pyrethrums is
pyrethrin, an insecticide. The term "pyrethroid" describes a class of
insecticides that include cypermethrin and other synthetic chemical compounds
of pyrethrum. When it comes to controlling ectoparasites that infest livestock,
sheep, and fowl, cypermethrin is a go-to herbicide. The broad-spectrum
pesticide cypermethrin is useful against many different types of cotton, fruit,
and vegetable crop pests. The assertion that cypermethrin is a wide range
pesticide, meaning it kills both target and beneficial species, was made by
Pascual and Perris in 1992. Frequent exposure to cypermethrin may cause insects
to acquire a resistance, which makes the insecticide useless, according to
Martinez-Cabrillo (1991). You may find the chemical structure of the pyrethroid
cypermethrin below, along with detailed technical details in Table.
Cypermethrin
Table 5: The
Cypermethrin Properties
|
Parameters |
Properties |
|
Chemical
Name |
((RS)α-cyano-3-phenoxybenzyl
(1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate) |
|
Chemical
Formula |
C₂₂H₁₉Cl₂NO₃ |
|
Melting
Point |
8183°C |
|
Solubility |
Solubility
in water: 0.009 mg/litre; soluble in organic solvents |
|
Stability |
Soil hydrolysis and
photolysis break it down. Chemical half-life: 6-20 days; Biological
half-life: less than 14 days. Hydrolysis of trans-isomers occurs 1.2-1.7
times more rapidly. (USDA, 1995) |
RESULTS
AND DICSUSSION
·
Enzyme
extrapolation in vivo utilising specific insecticides
Acid phosphatase
Figure shows the effects of pretilachlor,
cypermethrin, pendimethalin, and dimethoate on acid phosphatase activity.
Enzyme levels of dimethoate, pendimethalin, pretilachlor, and cypermethrin were
11.6±0.75 ΅g PNP/mg protein/30 minutes in the pesticide treated set (T2),
compared to 26.4±1.25 ΅g PNP/mg protein/30 mins in the control set (T1).
Table
6: Effects
of Pendimethalin, Pretilachlor, Dimethoate, and Cypermethrin on the acid
phosphatase activity of Perionyx
excavatus: a one-factor analysis of variance
|
Insecticide |
Source of variation |
df |
Mean square |
F |
Significance |
|
Dimethoate |
Treatment |
2 |
207.07 |
207.07 |
0.000 |
|
|
Error |
6 |
1.00 |
|
|
|
Pendimethalin |
Treatment |
2 |
149.97 |
164.802 |
0.000 |
|
|
Error |
6 |
0.910 |
|
|
|
Pretilachlor |
Treatment |
2 |
207.07 |
207.07 |
0.000 |
|
|
Error |
6 |
1.00 |
|
|
|
Cypermethrin |
Treatment |
2 |
308.280 |
308.280 |
0.000 |
|
|
Error |
6 |
1.000 |
|
|
Table
7: Acid
phosphatase activity as a function of pesticide treatment: the least
significant difference (LSD)
|
Insecticides |
Difference between |
Mean difference |
Significance |
|
Dimethoate |
T1 & T2 |
11.30 |
0.000 |
|
T1 & T3 |
16.20 |
0.000 |
|
|
T2 & T3 |
4.90 |
0.001 |
|
|
Pendimethalin |
T1 & T2 |
9.20 |
0.000 |
|
T1 & T3 |
13.90 |
0.000 |
|
|
T2 & T3 |
4.70 |
0.001 |
|
|
Pretilachlor |
T1 & T2 |
11.30 |
0.000 |
|
T1 & T3 |
16.20 |
0.000 |
|
|
T2 & T3 |
4.90 |
0.001 |
|
|
Cypermethrin |
T1 & T2 |
14.80 |
0.000 |
|
T1 & T3 |
19.40 |
0.000 |
|
|
T2 & T3 |
4.60 |
0.001 |
Figure 1: The acid phosphatase activity levels of P.
excavatus were measured in two experiments: one with P. excavatus exposed to sublethal dosages (T2) of certain
pesticides in an environment close to nature, and the other with no pesticide
at all (T1).
Alkaline phosphatase
Figure displays the effects of dimethoate,
pendimethalin, pretilachlor, and cypermethrin on the activity of alkaline
phosphatase. The alkaline phosphatase level in the control set (T1) was
51.6±2.25 ΅g PNP/mg protein/30 mins, whereas in the pesticide treated set (T2),
the enzyme levels were 77.8±1.50, 57.1±1.75, 65.7±1.10 ΅g, and 81.0±2.75 ΅g
PNP/mg protein/30 mins for dimethoate, pendimethalin, pretilachlor, and
cypermethrin, respectively.
Table
8:The
alkaline phosphatase activity of Pendimethalin, Pretilachlor, Dimethoate, and
Cypermethrin-exposed Perionyx excavatus
was analysed using a one-factor ANOVA.
|
Insecticide |
Source of variation |
df |
Mean square |
F |
Significance |
|
Dimethoate |
Treatment |
2 |
1154.92 |
362.328 |
0.000 |
|
|
Error |
6 |
3.188 |
|
|
|
Pendimethalin |
Treatment |
2 |
89.11 |
23.895 |
0.001 |
|
|
Error |
6 |
3.729 |
|
|
|
Pretilachlor |
Treatment |
2 |
355.030 |
142.344 |
0.000 |
|
|
Error |
6 |
2.494 |
|
|
|
Cypermethrin |
Treatment |
2 |
1443.510 |
214.515 |
0.000 |
|
|
Error |
6 |
6.729 |
|
|
Table 9: Alkaline phosphatase
activity as a function of pesticide treatment: the least significant difference
(LSD)
|
Insecticides |
Difference between |
Mean difference |
Significance |
|
Dimethoate |
T1 & T2 |
-26.20 |
0.000 |
|
T1 & T3 |
-38.40 |
0.000 |
|
|
T2 & T3 |
-12.20 |
0.000 |
|
|
Pendimethalin |
T1 & T2 |
-5.50 |
0.013 |
|
T1 & T3 |
-10.90 |
0.000 |
|
|
T2 & T3 |
-5.40 |
0.014 |
|
|
Pretilachlor |
T1 & T2 |
-14.10 |
0.000 |
|
T1 & T3 |
-21.40 |
0.000 |
|
|
T2 & T3 |
-7.30 |
0.001 |
|
|
Cypermethrin |
T1 & T2 |
-29.40 |
0.000 |
|
T1 & T3 |
-42.90 |
0.000 |
|
|
T2 & T3 |
-13.50 |
0.001 |
Acetylcholinesterase
Figure shows how the acetylcholinesterase activity is
affected by dimethoate, pendimethalin, pretilachlor, and cypermethrin.
Acetylcholinesterase levels were 160±2.50 nmolesthiocholine/min/mg tissue in
the control set (T1), and 60±1.75, 100±3.10, 120±2.25, and 40.8±1.35
nmolesthiocholine/min/mg tissue for dimethoate, pendimethalin, pretilachlor,
and cypermethrin, respectively, in the pesticide treated set (T2). Cypermethrin
exhibited the highest proportion of enzyme inhibition at 74.5 percent, whereas
pretilachlor showed the lowest percentage of inhibition at 25%. Pendimethalin
exhibited a 37.5% inhibition and dimethoate a 62.5% inhibition.
Table
10: Analysing
the effects of pendimethalin, pretilachlor, dimethoate, and cypermethrin on the
acetylcholinesterase activity of Perionyx
excavatus using a single-factor ANOVA
|
Insecticide |
Source of variation |
df |
Mean square |
F |
Significance |
|
Pendimethalin |
Treatment |
2 |
11725.000 |
2.842E3 |
0.000 |
|
|
Error |
6 |
4.125 |
|
|
|
Pretilachlor |
Treatment |
2 |
5200.00 |
612.485 |
0.000 |
|
|
Error |
6 |
8.490 |
|
|
|
Dimethoate |
Treatment |
2 |
2800.00 |
512.977 |
0.000 |
|
|
Error |
6 |
5.458 |
|
|
|
Cypermethrin |
Treatment |
2 |
16341.64 |
4.955E3 |
0.000 |
|
|
Error |
6 |
3.298 |
|
|
Table 11: Accetylcholinesterase activity as a function of
pesticide treatment: the least significant difference (LSD).
|
Insecticides |
Difference between |
Mean difference |
Significance |
|
Pendimethalin |
T1 & T2 |
100.00 |
0.000 |
|
T1 & T3 |
115.00 |
0.000 |
|
|
T2 & T3 |
15.00 |
0.000 |
|
|
Pretilachlor |
T1 & T2 |
60.00 |
0.000 |
|
T1 & T3 |
80.00 |
0.000 |
|
|
T2 & T3 |
20.00 |
0.000 |
|
|
Dimethoate |
T1 & T2 |
40.00 |
0.000 |
|
T1 & T3 |
60.00 |
0.000 |
|
|
T2 & T3 |
20.00 |
0.000 |
|
|
Cypermethrin |
T1 & T2 |
119.20 |
0.000 |
|
T1 & T3 |
135.00 |
0.000 |
|
|
T2 & T3 |
15.80 |
0.000 |
Figure 2: P. excavatus alkaline phosphatase activity levels in two groups:
one subjected to sublethal dosages (T2) of certain pesticides in an environment
mimicking nature, and the other without pesticide (T1).
Figure 3: Comparing the acetylcholinesterase (AchE) activity of P. excavatus in two conditions: one with
sublethal dosages (T2) of certain pesticides in an environment close to nature,
and another with no pesticide (T1).
·
Pesticide
effects on earthworm chloragogen cells in the gut
Treatments
with any of the three pesticides had a major impact on the earthworms'
choloragogen cell tissue lining, which lines their digestive tracts. The
earthworms in the control group had no damage to their guts or chloragogen
tissue layer lining. However, in the instance of all the polluted sets of the
chosen pesticides, the intestinal lining and the chloragogen tissue layer were
both significantly deformed with vacuole-like structures.
The
test specimens' chloragogen tissue layer and intestinal wall were the most
severely affected by permethrin.
Figure
4: The chloragogen tissue layer (Ch) in both the control
and pesticide-treated earthworm guts, as seen via histology.
CONCLUSION
The results of this research
unequivocally show that the physiological and histological characteristics of Perionyx
excavatus are adversely affected by sublethal quantities of common
pesticides, including dimethoate, cypermethrin, pretilachlor, and pendimethalin.
A disturbance in metabolic and neurological processes is indicated by the noted
decrease in vital enzyme activity, including acetylcholinesterase, acid
phosphatase, and alkaline phosphatase. Significant structural damage to the
chloragogen tissue and stomach lining was also found by histological
investigation, particularly in samples exposed to cypermethrin. The health and
ecological function of earthworms, which are essential for soil fertility and
ecosystem balance, may be jeopardised by pesticide exposure, even at non-lethal
levels, according to these impacts. As a result, the study highlights how
crucial it is to reduce the use of pesticides and promotes further
investigation into safe, ecologically friendly alternatives.
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