Panneers-Chap
Panneers-Chap
Panneers-Chap
net/publication/354858818
CITATIONS READS
0 706
5 authors, including:
Rittick Mondal
Raiganj University
27 PUBLICATIONS 51 CITATIONS
SEE PROFILE
Some of the authors of this publication are also working on these related projects:
Study of Rhizospheric soil microflora of Saussurea obvallata (DC.) Edgew. (Brahma Kamal) View project
Exploring the interaction of phyllosphere bacteria on rice stomatal complex for drought mitigation in rice View project
All content following this page was uploaded by Debasis Mitra on 02 January 2022.
Chapter-5
Table of contents
1. Introduction
2. Impact of heavy metals on soil microbes
3. Impact of polycyclic aromatic hydrocarbon on soil microflora
4. Impact of industrial wastes on soil microflora
5. Impact of pesticides on soil microflora
5.1. Impact of pesticides on soil fertility
5.2.Impact on mycorrhizal fungi
5.3. Impact on biological cycle
5.4. Impact on enzymes activities
5.5. Impact on others
6. Impact of soil pollution on environment
7. Conclusion
8. References
1. Introduction
As the world's population grows, so does the demand for food, which
necessitates increased and sustainable food production through intensive
agriculture, public health considerations, and proper use of natural resources. To
satisfy this demand, agriculture must be improved with advanced agricultural
technologies, and soil quality must be maintained21 (Jones et al., 2013). Soil quality
plays a major role in today's production. Concerns about soil pollution have grown
in significance in the current sense of fertilizer, waste, metals, and chemical usage,
among other things. The existence of xenobiotics (human-made) chemicals or other
changes in the natural soil environment cause soil contamination or pollution as
part of land degradation14 (Gianfreda, and Rao, 2008). Industrial activity,
agricultural chemicals, and excessive waste disposal are the most common causes.
It's important to realize that all soils contain substances that are harmful or toxic to
humans and other living things. The concentration of such compounds in
unpolluted soil, on the other hand, is low enough that they do not pose a threat to
the environment. The soil is said to be polluted when the concentration of one or
more toxic substances is high enough to damage living organisms. Soil pollution is
described as the contamination of soil with toxic chemicals or other contaminants in
such a way that the soil quality is lowered and it becomes uninhabitable for living
organisms (e.g. insects, microbes, plants, etc.)52 (Varjani et al., 2019).
Anthropogenic practices are primarily responsible for this increase. Heavy metals,
plastics, polycyclic aromatic hydrocarbons, and other non-biodegradable wastes are
considered to be major soil pollutants that have a direct impact on soil microbes and
earthworms22 (Keshavarzi et al., 2018).
One of the main factors causing soil pollution is the ever-increasing use of
chemicals such as pesticides, herbicides, insecticides, and fertilizers, which increase
salinity in the soil, making it unsuitable for crop production and negatively
affecting the microorganisms present in the soil, causing the soil to lose its fertility
and resulting in the loss of minerals present in the soil, thus causing soil pollution49
(Tsion and Steven, 2019). Other types of soil contamination typically arise from the
rupture of underground storage tanks, acid rain falling onto the soil, radioactive
fallout, percolation of contaminated surface water to subsurface strata, fuel
leakages from automobiles, unfavorable and harmful irrigation practices, leakages
from sanitary sewage, leaching of wastes from landfills or direct discharge of
industrial wastes to the soil, improper septic system and management and
maintenance, that get washed away due to rain and seep into the nearby soil and
unhealthy waste management techniques, which are characterized by release of
sewage into the large dumping grounds and nearby streams or rivers17
(Havugimana et al., 2015).
2. Impact of heavy metals on soil microbes
Heavy metal contamination is a serious global environmental issue because it
harms the growth of plants, soil indigenous species such as bacteria, earthworms,
and other soil-dwelling organisms in terms of population size, diversity, and
activities. Cd, Pb, As, Cu, Ni, and other heavy metals are the most harmful57 (Xie et
al., 2016). It was discovered that the impact of heavy metals on soil microflora and
their usable concentration have a strong negative relationship. As a result, factors
that influence heavy metal bioavailability in the soil may have an effect on the
metals' toxicity to the soil microbial community. Metal pollution in the soil causes a
significant decrease in microbial biomass. In certain cases, this decline occurs at
low metal concentrations23 (Khan and Scullion, 2002). Metal concentrations near
the EC in soil (Exciding concentrations-determined limits) are likely to trigger a
significant microbial biomass inhibition with long-term consequences for soil
productivity.
Heavy metals are refractory contaminants that are widespread and valuable.
Heavy metal toxicity is mainly determined by their bioavailability, or the number of
species that are ultimately absorbed into the body by absorption, migration, and
transformation. High concentrations of heavy metals on the toxicity of
microorganisms may have two reasons, heavy metals and microorganisms have a
strong affinity, and it is easy with some biological macromolecules such as enzyme
activity center22 (Dutta et al., 2019), and electron-donating groups such as nucleic
acid base, mercapto protein, and phosphate combination, resulting in the
inactivation of these biological macromolecules, more than the ability of organisms
to bear, resulting in biological disease and death, from a short-term perspective,
heavy metal pollution will lead to the degradation of microbiological diversity of
those who lack the pressure on the outside world, and at the same time lead to those
who can adapt to those pressures increased; secondly, due to heavy metals cannot
be microbial degradation of the majority of ligand metallothionein. With the food
chain of enrichment and transmission, a large number of metallothionein and small
molecules like glycine and taurine are simple to accumulate, endangering all
biological, particularly human health and life protection.
Heavy metals in the soil can affect the growth of soil microbes as well. Soil
microbes are involved in almost all soil biochemical reactions, and they play an
important role in the production of soil organic matter and its decomposition of
harmful compounds, biochemical cycles, and the formation of soil structure. Soil
microbial properties, such as the underlying soil respiration rate and enzyme
activity, which are influenced by soil pH, organic matter, and other chemical
properties, are negatively affected by heavy soil contamination46 (Stefanowicz et
al., 2020). Low concentrations of heavy metal polluted soil are, in most cases,
conducive to CO2 release; high concentrations of heavy metal contamination, major
inhibition of soil respiration; extreme heavy metal pollution may impair soil
microbial activity, posing a serious threat to soil ecosystem function, according to
studies42 (Shahid et al., 2017).
3. Impact of polycyclic aromatic hydrocarbon on soil microflora
PAHs (polycyclic aromatic hydrocarbons) are chemical contaminants that are
volatile. PAHs have carcinogenic and mutagenic properties. It has also shown
genotoxic effects (IARC, 2010). Even at low levels, PAHs have the ability to
damage the environment and/or human health. High levels of PAHs in soil, in
particular, may have a negative impact on total bacterial and fungal species,
microbial metabolic processes, and enzyme activities. PAHs can influence
microbial community composition by exerting pressure on sensitive soil
microorganisms.
Polycyclic aromatic hydrocarbons (often abbreviated to PAHs) are organic
compounds that:
Contain only carbon and hydrogen atoms.
Contain more than one aromatic ring in their chemical structures.
Pesticides are divided into five groups by their acute oral and dermal
toxicity, according to the World Health Organization. Aside from that, many
pesticides (such as Aldoxycarb, Butacarb, Cycluron, Erbon, and others) have been
phased out16 (Hun et al., 2021; Table 2).
Table-2. Classification of pesticides and some examples
Class Oral: LD50 in Dermal: LD50 in Examples
mg/kg body mg/kg body
weight of rat weight of rat
Ia- Extremely hazardous <5 <50 Disulfoton, Captafol
Ib- Highly hazardous 5-50 50-200 Dichlorvos,
Triazophos
II- Moderately hazardous 50-2000 200-2000 Benfuracarb,
Carbosulfan
III- Slightly hazardous Over 2000 Over 2000 Butylate, Malathion
U- Unlikely to present 5000 or more 5000 or more Bioresmethrin,
acute hazard Carpropamid