The effect of biochar soil amendment onbioavailability of Lead (Pb) in contaminatedsoil of Kabwe District of Zambia
By
KABENUKA MUNTHALISupervisors
Dr. Benson Chishala-ZAMBIA
Dr. Elijah Phiri-ZAMBIADr. Yoshitaka UCHIDA-JAPANProf. Samuel Mutiti-USA

INTRODUCTION• Soil contamination is an excess of any element or compound,through direct or secondary exposure, which causes a toxic
response to biota or humans, resulting in unacceptableenvironmental risks (Adriano, 2001; Abrahams, 2002;
Vangronsveld et al., 2009).
• Accumulation of such high levels of heavy metals is highly toxic
and would certainly kill the common nonaccumulator plant andadversely affect human life.
• Lead (Pb)belongs to those elements(heavy metals) that are poorly
mobile and rarely available to plants. However, it may create
different organic and inorganic compounds, easily absorbed byroots.

INTRODUCTION• Contamination of soils with both organic and inorganic toxins occurs
worldwide (Mench et al., 2010) and Kabwe town in Zambia has been
one of the most worst affected by previous mining activities (Kamonaet al., 1998)• Organic materials are a popular choice for this as they are derived
from biological matter and often require little pre-treatment before
they may be directly applied to soils.
• Reliable indications from experimental trials that suggest biochar as adependable technology for immobilizing and improving the physical,
chemical and biological status of soils.

INTRODUCTION• Biochars are also produced by combustion processes (pyrolysis), but
the source materials are generally limited to biological residues (e.g.
wood, poultry litter, crop residues etc) and not• However , the process involved in the remediation of contaminatedsoils through the applications of various amendments is a long-term
one.
• The desired outcome of such plans is mainly to reduce the transfer ofpollutants to nearby water bodies and to reduce uptake by plants aswell as useful microbes.

INTRODUCTION• However, in hyperaccumulator species, such concentrations areattainable. Nevertheless, the extent of metal removal is ultimately
limited by plant ability to extract and tolerate only a finite amount ofmetals (Verheijen et al., 2010).
• The amendment of soils for their remediation is a long standing
procedure, with the aim of reducing the risk of pollutant transfer toproximal waters or receptor organisms.

Statement of the Problem• In Zambia waste landfills are currently the mostwidely used method for municipal waste disposal andthis is raising some environmental concerns. Due tothe fact that landfills can be an active source of a large
number of Heavy metals, in this case Pb, because
heavy metals are able to through air fallout or leachate
release. This poses a greater risk, because at this pointtheir exposure is broad and non-selective on various
species throughout the food chain, thus posing aserious threat to the environment, animals, andhumans.

Justification• Heavy metal elements have proven to be toxic even in small
amounts, this is due to their non-biodegradable andcumulative nature. In addition, conventional methods ofremediation or environmental clean-up have with timedemonstrated to be an uneconomical approach to thisproblem. These huge costs render them unsustainable in third
world countries that face an urgent need for a clean and safeenvironment to enhance social and economic productivity. Itis in this regard that in situ phytoremediation as become
popular in the modern agenda as it provides a low cost andenvironmentally acceptable approach to reducing risk bypollutant transfer.

OBJECTIVES
Overall objective• The overall objective of the study was to evaluate the effects of biochar
as a soil amendment on the bioavailability of lead (Pb) in leadcontaminated soils
Specific objectives were to:• To determine if the amount of biochar added to the soil affects thebioavailability of lead concentrations in the soil profile• To analyze the effects of biochar on plant growth (Biomass) in thecontext of ecological restoration of contaminated soils

Hypotheses• There is not significant difference in the bioavailability concentrationsof lead in the soil profile.
• There is no significant difference in the effects of biochar on plant
growth in the context of ecological restoration of contaminated soils.

METHODS AND MATERIALS• Location: The soil was collected from the identified site in Kabwe(14º27’55.92” S, 028º26’40.02” E) in bulk (650kilograms from the top
30cm of the soil). This experiment was done at the University of Zambia,
school of agricultural sciences-Located at S15º23’38.8” and E028º20’03.3”
under greenhouse conditions.
• TEST CROPS: The test crops were Chinese cabbage (Brassica pekinensis)
and Tithonia (Tithonia diversifolia). The experiment was a two by four (2x4) factorial experiment which will take the form of a Split plot design. Thisexperiment had four (4) treatments at four levels of biochar application ratesof 0 (Control), 5, 10 and 20 t ha−1. The treatments was replicated four (4)times. Planting date 14th January, 2017.

MATERIALS AND METHODSMETHODS AND MATERIALSMAP OF ZAMBIA AND LOCATION OF KABWE

Tithonia (Tithonia diversifolia)

Chinese cabbage (Brassica pekinensis)

METHODS AND MATERIALS• Soil and Biochar information: Sampling was done at 20cm depth
and the sampling was done before and after planting. Standard
methods were used to analyze the physio-chemical properties of thesoil and results are shown in Table 1.
• Field layout and randomization was done as shown in figure 1 below:Figure 1:Field layout (Randomization)

Significance of study• This study will contribute to understanding the capacities androles of plants and soils amendments in the phytoremediation
process respectively. It will also provide a quantitative andqualitative description of this low risk strategy in themitigation of environmental hazards of areas polluted withheavymetals.
Underlining
thesignificanceofphytoremediation in the environmental cleanup process will
help build up more efficient management strategies

RESULTS AND DISCUSSIONRESULTS AND DISCUSSION
Table 1: Physical and chemical characterization of soils and biochars used in the experiment

RESULTS AND DISCUSSION

Figure 2: Lead concentration (ppm) in

Figure 3: Lead concentration (ppm) in

Tithonia for the four application rates(t/ha) ofbiochar

Chinese Cabbage for the four application
rates(t/ha) of biochar

RESULTS AND DISCUSSION

Figure 4: Schematic model of different phytoremediation technologies
involving removal and containment of contaminants; (B) physiologicalprocesses that take place in plants during phytoremediation (SOURCE;http://www.nature.com).

Figure 2: Greenhouse experiment with the Chinese
cabbage and Tithonia

RESULTS AND DISCUSSION

Figure 6: Biomass yield of Tithonia on dry weight (grams) in thefour application rates

Figure 7: Biomass yield of Tithonia on dry weight(grams) in the four application rates

RESULTS AND DISCUSSION•

Figures 2 and 3 show the effect of biochar amendment on the bioavailable
Pb in kabwe soils, it was revealed that the Pb was significantly (P<0.05)
reduced at 20 t/ha application rate.

•Figure 4 and 5 shows that biochar application did not have a significanteffect (P>0.05) the biomass yield of Chinese cabbage and Tithonia on drymass basis.

•Biomass was measured on dry weight basis to reduce error arising fromvariability in the moisture content of the plants used in the experiment.

CONCLUSIONS• From the results it cant be concluded that in the short term, the higher
levels of biochar amendment showed significant results inimmobilizing Pb.
• This experiment combined phytostabilization and phytoextraction asremediation technologies. A schematic figure was depicted in figure 4to explain the complexation of the Pb ion and the translocation of thebioavailable Pb in the plant system for uptake.

RECOMMENDATIONS• It would be important to exploit various organic materials as a sourceof biochar and measure their ability to chelating heavy metals as aphytoremediation measure• It is also important to measure the quantities of biochar that may beeconomical but still achieve the necessary results from the study.
• Additionally the practice of soil amendment may also be a convenientroute to the disposal of organic residues surplus to requirement.

Acknowledgements• I would like to thank my supervisors; Dr. B. Chishala, Dr. E. Phiri andProf. S. Mutiti, Prof. Yoshitaka Uchida for their support & guidance
they provided during the project.
• I am also thanking APPSA/GOVERNMENT OF ZAMBIA/WORLDBANK and JICA for financial support to pursue the MSc in ISFM. I
would also want to thank all staffs from Soils Department for theirsupport. Finally, I wish to thank my family their support andencouragement.

REFERENCES• Lehmann, J. et al. (2011b) ‘Biochar effects on soil biota - A review’, Soil
Biology and Biochemistry, 43(9), pp. 1812–1836. doi:
10.1016/j.soilbio.2011.04.022.
• Major, J., Lehmann, J., et al. (2010) ‘Fate of soil-applied black carbon:
Downward migration, leaching and soil respiration’, Global Change
Biology, 16(4), pp. 1366–1379. doi: 10.1111/j.1365-2486.2009.02044.x.
• Novak, J. M. et al. (2009) ‘Impact of Biochar Amendment on Fertility of aSoutheastern Coastal Plain Soil’, Soil Science,.
• Pandian, K. et al. (2016) ‘Effect of biochar amendment on soil physical,chemical and biological properties and groundnut yield in rainfed Alfisolof semi-arid tropics’, Archives of Agronomy and Soil Science,THE END

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