Presentation on Environmental issues

1. Rabbiya Abdul Qadir
Roll #79
BS Biotechnology
(Final year, 8th semester)
Seminar II course Presentation
Supervisor : Eng.Tabish Ali

2. Impact factor : 8.9
Journal : Journal Of Environmental
Management
REVIEW ARTICLE:
DIAGNOSIS OF SOIL
CONTAMINATION USING
MICROBIOLOGICAL INDICES: A
REVIEW ON HEAVY METAL
POLLUTION

3. SOURCES OF HEAVY METALS POLLUTION:
Trace heavy metals are indispensable for organisms
to maintain normal life activities. However, excessive
heavy metal accumulation is harmful to the natural
environment and human health. Excess heavy metals
were accumulated in soil through many pathways,
including the use of pesticides and fertilizers,
improper stacking of the industrial residue, chemical
manufacturing etc.

4. Heavy metal contamination of soil has become a serious global issue because of their
persistence in the environment and the non-biodegradable nature leading to their
accumulation to toxic levels. In order to achieve early warning and prevent soil quality
from deteriorating, it is necessary to select suitable indices to diagnose heavy metal
pollution. Microbiological indices for monitoring soil pollution by heavy metals are
gaining attention.
Microbiological indices mainly included:
1. Mirobial abundance
2. Microbial community
3. Microbial activity

5. • The microbial biomass of soil includes the total mass of algae, bacteria, fungi as well
as protozoa.
• Microbial biomass contains carbon, nitrogen, phosphorus, sulfur, etc.
• Microbial biomass is greatly affected by soil changes and a considerable amount of
evidence has shown that soil microbial biomass was sensitive to the increase of
heavy metal concentration.
• The change of microbial biomass can be used to predict soil quality. Soils with high
microbial biomass have relatively good functions, represent good soil quality and can
store and recycle more nutrients.
Microbial
abundance
1. Microbial
biomass
Microbial biomass
Carbon/Nitrogen
Microbial biomass
related ratios
1. MICROBIALABUNDANCE:

6. • Nitrification is a process that converts ammonium to nitrite and finally to nitrate.
• As the first and rate-limiting step, ammonia oxidation is the pivot of the global N-
cycle, which is catalyzed by ammonia oxidizing archaea (AOA) and ammonia-
oxidizing bacteria (AOB) with functional enzymes of AMO.
• The AMO is a trimeric membrane-binding protein consisting of alpha, beta and
gamma subunits encoded by amoA, amoB and amoC genes, respectively.
• Ammonia-oxidizing genes are sensitive to the stress of heavy metals, and have been
widely used as markers to diagnose soil contamination. The amoA gene has been
used extensively due to its highly conservative coding the α subunit.
Microbial
abundance
2. Nitrification
gene
AMO gene

7. • The functional genes encoding denitrifying enzymes are quite sensitive to the stress
of heavy metals, and diagnose the soil quality.
• Four different reductases: nitrate reductase (Nar), nitrite reductase (Nir), nitric oxide
reductase (Nor) and nitrous oxide reductase (Nos), are involved in the process. The
nos gene seems to be less sensitive to heavy metals than other denitrifying genes, and
it is necessary to continue to study its resistance to heavy metals in the future.
Microbial
abundance
3. Denitrification
gene
Nar, Nir, Nor, Nos gene

8. • Soil microbial community structure and diversity are highly sensitive to soil changes and
are often used as indexs of metal contaminations.
• The diversity of soil microbial communities is extremely rich, but in moderately heavy
metal contaminated soils, it is reduced by more than 1000 times. The heavy metals
contamination had less impact on the bacterial community structure, but significantly
affect soil bacterial diversity.
• It cannot be used as an independent indicator to diagnose soil quality. The indices of
community structure and diversity may not accurately reflect the function of microbial
performance or function.
Density
Structure
The changes of
indices under the
stress of heavy metal
Reaction mechanism/
Reason for difference
sensitivities
2. MICROBIAL COMMUNITY:
Microbial
community

9. • Numerous studies have shown that soil enzymes are sensitive to heavy metals. The
high activity of enzymes represents good soil quality, while the low activity may be
related to the toxicity of pollutants to biological processes.
• The response of soil enzymes to heavy metals can be roughly divided into three types:
(I)Activation; (II) Inhibition; (III) Not affected. However, most of the studies showed
that enzyme activity was greatly depressed, and the inhibition rely on the nature and
concentration of heavy metals
Catalase,
Urease,
Dehydrogen
ase, etc
3. MICROBIALACTIVITY:
Microbial
activity Enzyme activity

10. Microorganisms, the
most active element
of the soil ecosystem
are much more
susceptible to the
stress of heavy
metal.
03
Microbiological
diagnosis test is not
only easy, rapid and
cheap, but only
requires a small
amount of sample.
Microbes in soil are
not only extremely
abundant, but also
closely related to the
degradation of
pollutants as well as
the fertility soil.
WHY USING MICROBIOLOGICAL INDICES?
02
01

11. Diagnose soil quality with a set of
microbiological indicators.
Quantitative analysis of relationship
between soil and physiochemical
factors & microbial indicators.
Study the contribution of different
proportions of heavy metals to
synergistic or antagonistic effects.
Conduct the in-situ investigation.
FUTURE PROSPECTS:

12. REFERENCES:
1. Tang, J., Zhang, J., Ren, L., Zhou, Y., Gao, J., Luo, L., ... & Chen, A.
(2019). Diagnosis of soil contamination using microbiological indices:
A review on heavy metal pollution. Journal of Environmental
Management, 242, 121-130.
2. Baby, R., Saifullah, B., & Hussein, M. Z. (2019). Carbon
nanomaterials for the treatment of heavy metal-contaminated water and
environmental remediation. Nanoscale research letters, 14(1), 1-17.