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Efficacy of Woodchip Biochar and Brown Coal Waste as Stable Sorbents for Abatement of Bioavailable Cadmium, Lead and Zinc in Soil
Amoah-Antwi, C. Kwiatkowska-Malina, J. Szara, E. Thornton, S. Fenton, Owen Malina, G.
Amoah-Antwi, C.
Kwiatkowska-Malina, J.
Szara, E.
Thornton, S.
Fenton, Owen
Malina, G.
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2020-10-03
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Amoah-Antwi, C., Kwiatkowska-Malina, J., Szara, E., Thornton, S., Fenton, O., Malina, G. Efficacy of Woodchip Biochar and Brown Coal Waste as Stable Sorbents for Abatement of Bioavailable Cadmium, Lead and Zinc in Soil. Water Air Soil Pollut., 2020 231, 515. DOI: https://doi.org/10.1007/s11270-020-04885-4
Abstract
Organic sorbents alter physicochemical soil
properties and mitigate heavy metal (HM) bioavailability. However, some sorbents are labile and, therefore,
introduce the risk of HM release into soil after
mineralisation. Before field application, new stable organic sorbents such as woodchip biochar (BIO) and
brown coal waste (BCW) need to be tested and compared with standard organic amendments like farmyard
manure (FYM). An incubated pot experiment was conducted to investigate the efficacy of FYM, BIO and
BCW (added to soil in pots at 5 and 10% w/w) to alter
soil physicochemical properties and mitigate bioavailability of Cd, Pb and Zn spiked in treatments at different
doses (in mg kg−1
); 0 (not spiked), 1 (1 Cd, 70 Pb, 100
Zn) and 2 (3 Cd, 500 Pb, 700 Zn), and incubated for
9 weeks. At the end of the experiment, the EDTAextractable HM fractions, pH, cation exchange capacity
(CEC) and specific surface area (SSA, to check trends)
were determined in all treated soils. Results showed that
FYM, BCW and BIO generally improved all soil properties (except reduced pH from BCW and apparent SSA
reduction from FYM) and accounted for respective
maximum abatements of Cd (50.2, 69.9 and 25.5%),
Pb (34.2, 64.3 and 17.4%) and Zn (14.9, 17.7 and
11.8%) bioavailability in soil. FYM and BCW were
more effective at 10% w/w especially in the low contaminated soil, whereas the highest efficacy for BIO was
at 5% w/w and in the high contaminated soil. The
efficacies of sorption by the organic sorbents varied
for different HMs and were in the orders: BCW >
FYM > BIO for Cd, FYM > BCW > BIO for Pb and
BIO > BCW > FYM for Zn. Soil pH and CEC were
strongly correlated with HM bioavailability in all treatments and implied that immobilisation of HMs occurred
via complex formation, ion exchange and pH-dependent
specific adsorption. All three sorbents were beneficial as
soil amendments, and in terms of HM mitigation, BCW
had the highest efficacy, followed by FYM and then
BIO. Considering the documented high soil stability of
BCW and BIO, these results are promising for further
trialling at field scale.