Abstract
The current study investigated the effect of biochars derived from cinnamomum woodchip, garden waste and mulberry woodchip on soil phytoavailable lead (Pb), cadmium (Cd) pools, and their uptake by Chinese cabbage (Brassica chinensis L.). The biochars were produced at 450 °C of pyrolysis temperature. The contaminated soils were collected from Yunfu (classified as Udept), Jiyuan (Ustalf) and Shaoguan (Udult) cities in China at the depth of 0–20 cm and amended with biochars at the rate of 3% w/w. After mixing the soil with biochar for 14 days, the Chinese cabbage was planted in the amended soils. Then, it was harvested on the 48th day after sowing period. In Udult soil, Chinese cabbage died 18 days after sowing period in control and soils amended with cinnamomum and mulberry biochars. Although only plants grown with the garden waste biochar treatment survived in Udult soil, amendment of garden waste or mulberry biochars at 3% w/w (450 °C) to Udult soil significantly increased (4.95–6.25) soil pH compared to other biochar treatments. In Udept and Ustalf soils, the application of garden waste and mulberry biochars significantly improved plant biomass compared to control, albeit it was dependent on both biochar and soil properties. Garden waste biochar significantly decreased soil Cd phytoavailable concentration by 26% in the Udult soil, while a decrease of soil Cd phytoavailable concentration by 16% and 9% was observed in Ustalf and Udept soils, respectively. The available phosphorus in biochar and soil pH were important factors controlling toxic metal phytouptake by the plant. Thus, the amendment of soil with biochar at 3% can effectively reduce the mobility of Cd and Pb in soil and plant uptake. However, biochar and soil properties should be well-known before being used for soil toxic metal immobilization.
Highlights
Contaminated agricultural soils with toxic metals occur mainly through human activities such as mining, waste disposal, irrigation with wastewater, and application of inorganic and organic fertilizers to agricultural land (Xiao et al 2019)
The plants cultivated in the Udult soil died 18 days after sowing period, except the plants grown in Udult soil amended with garden waste biochar (Table 3)
Garden waste biochar had its highest reduction in soil phytoavailable phytoavailable lead (Pb) concentration in Udult (16.7 ± 0.69%) followed by what it reduced in Ustalf (6.7 ± 0.76%) and Udept (− 7.87 ± 6.48%) soils, respectively
Summary
Contaminated agricultural soils with toxic metals occur mainly through human activities such as mining, waste disposal, irrigation with wastewater, and application of inorganic and organic fertilizers to agricultural land (Xiao et al 2019). Previous studies have discovered that crops cultivated in soils polluted with toxic metal(loid)s, e.g., cadmium (Cd), lead (Pb), and arsenic (As), could uptake high concentration of metal(loid)s by roots and accumulate them in their tissues (Gan et al 2017; Hussain et al 2021; Li et al 2020; Natasha et al 2021; Wen et al 2021). Various surveys have shown that heavy metal Cd and Pb contamination in soil has become a major problem in the quality of the global environment, in China (Guan et al 2018) These two metals are difficult to degrade and easy to be enriched by plants (Babalola and Ojuederie 2017). Crops grown in Cd- and Pb-contaminated soil without any pre-treatment may contain higher concentration of these toxic metals in their tissues (Anwar et al 2020)
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