Do soil amendments used to improve agricultural productivity have consequences for soils contaminated with heavy metals?

Abstract

This study presents an analysis of the effects of manure and lime commonly used to improve agricultural productivity and evaluates the potential for such soil amendments to mobilise/immobilise metal fractions in soils contaminated from nearby mine tailings in the Zambian Copperbelt. Lime and manure were applied at the onset of the study, and their effects were studied over two planting seasons, i.e. 2016-17 and 2017-18. Operationally defined plant-available Cd, Cu, Ni, Pb and Zn in the soil, were determined by extraction with DTPA-TEA (diethylenetriaminepentaacetic acid-triethanolamine) and 0.01 M Ca(NO 3 ) 2 , before, and after, applying the amendments. In unamended soils, Cd was the most available and Ni the least. Lime application decreased extractable Cd, Cu, Ni, Pb and Zn. The response to lime was greater in soils with an initially acidic pH than in those with approximately neutral pH values. Manure increased DTPA extractable Zn, but decreased DTPA and Ca(NO 3 ) 2 extractable Cd, Cu and Pb. Combined lime and manure amendment exhibited a greater reduction in DTPA extractable Cd, Ni, Pb, Zn, as well as for Ca(NO 3 ) 2 extractable Cd compared to separate applications of lime and manure. The amendments had a significant residual effect on most of the soil fractions between season 1 and 2. The results obtained in this study showed that soil amendment with minimal lime and manure whilst benefiting agricultural productivity, may significantly reduce the mobility or plant availability of metals from contaminated agricultural soils. This is important in contaminated, typical tropical soils used for crop production by resource poor communities affected by mining or other industrial activities.

Health risk assessment of heavy metals in soils and food crops from a coexist area of heavily industrialized and intensively cropping in the Chengdu Plain, Sichuan, China

“…Metal elements may have different behaviors such as bioavailability, leachability, and mobility in various environments. An extractable form by DTPA is commonly applied to evaluate availability in previous many studies ( Kim et al, 2015 ; Zahedifar et al, 2017 ; Kaninga et al, 2020 ). It was reported that Cd and Cu were readily extracted by DTPA compared to Pb and Zn ( Singh et al, 1998 ), suggesting that Cd and Cu have more bioavailability in the same field condition, and therefore it should be possible to incur more leachability and/or mobility in a wet–dry cropping rotation due to the function of water.…”

Practical limitations of bioaugmentation in treating heavy metal contaminated soil and role of plant growth promoting bacteria in phytoremediation as a promising alternative approach

“…(2017) Cd (0.98) Cu (29.6) Pb (3.34) Zn (38) Mining area Iran Cd (0.9) Shojaei et al. (2021) Cr (0.87) Mn (0.88) Pb (0.94) Mining area India Cd (5.16) Pradhan et al., 2020 Co (3,097.01) Cr (3,012.45) Cu (7.51) Fe (5,485.01) Mn (5,840.5) Ni (2,281.01) Zn (226.1) Mining area Zambia Cd (0.45) Kaninga et al. (2020) Cu (979) Ni (44) Pb (10.2) Zn (32) Mining area Morocco Cu (964.1) Raklami et al.…”

Crop uptake of heavy metals in response to the environment and agronomic practices on land near mine tailings in the Zambian Copperbelt Province

“…Each sub-plot was 45 m 2 , consisting of six 10 m long ridges, spaced 90 cm apart. Soil samples were collected from each plot and characterized for basic soil fertility, and heavy metal concentrations before amendments were applied as detailed in Kaninga et al (2020b). Lime (CaCO 3 ) and pre-treated chicken manure (designated 'manure') were applied only within the ridge area, i.e.…”

“…For quality assurance, blanks, duplicates and certified reference materials (CRMs) including NIST 1573a (tomato leaves), NIST 1570a (spinach) and NIST 1567b (wheat flour) were analysed alongside the plant samples -the latter are presented in Supplementary Table 1 demonstrating good analytical performance. Soil chemistry data was reported in Kaninga et al (2020b). For this paper, only crop data is considered for exposure related to direct human consumption of food produce.…”

“…The et al (2006) reported that the maize grain yield increase after application of lime in acid soils was largely due to reduction in exchangeable aluminium rather than to an increase in pH. This could explain the lack of differences in yield between Dam1 and Dam2 or the lack of an interaction between the Dam and lime as the soils in Dam1, though characterised as acidic (pH 5.1 -5.6), had only trace levels of exchangeable Al (Kaninga et al 2020b).…”