Amendment of Husk Biochar on Accumulation and Chemical Form of Cadmium in Lettuce and Pak-Choi Grown in Contaminated Soil

Abstract

(1) Background: Cadmium (Cd) accumulated in vegetables not only affects their growth but can also enter the human body via food chains and lead to various illnesses. Plants can decrease the toxicity by changing the chemical forms of Cd, which include inorganic (FE), water-soluble (FW), pectate- and protein-integrated (FNaCl), undissolved phosphate (FHAc), oxalate (FHCl), and residual forms (FR). Among them, FE and FW chemical forms show higher mobility to translocate upward from roots to shoots compared with the others. (2) Methods: Different varieties or cultivars of lettuce and pak-choi were grown in Cd-contaminated soils amended with husk biochar (BC) to replenish nitrogen to the recommended amount and also to raise the soil pH value. (3) Results: More than 73% of the accumulated Cd in the edible organs was compartmentalized in FE chemical form in both leafy vegetables regardless of treatments. In comparison with control, the application of BC decreased the Cd concentrations and bioconcentration factors in the roots and shoots of two leafy vegetables at different growth periods in general. The chemical form and bioaccessible fraction of Cd in the edible blanching tissues were used to calculate the risk of oral intake. The vegetable-induced hazard quotients of lettuce and pak-choi were acceptable, except for pak-choi grown in control without applying BC.

Effect of Vermicompost Amendment on the Accumulation and Chemical Forms of Trace Metals in Leafy Vegetables Grown in Contaminated Soils

“…Sweet (coded as LSS). The experimental results of the previous study showed that the LSC and LSS accumulated 2.1–6.9 and 1.8–3.1 mg kg −1 of Cd in the shoots after being grown for 35–49 d; moreover, the BCC and BCW accumulated 2.9–12.7 and 6.6–32.3 mg kg −1 of Cd in the shoots after being grown in the same Cd-contaminated soils for 35–49 d [ 43 ]. The two varieties of pak choi used in this study had higher accumulating capacity of Cd compared with the two lettuce cultivars.…”

“…Another index translocation factor (TF)—the ratio of TM concentration in the shoot of a plant to that in the root of the plant—was used to examine the upward transport of TMs under different treatments. The hazard quotient (HQ v ) was calculated in accordance with Chen et al [ 43 ] to assess the health risk of TM through oral ingestion of vegetables using Equation (1), where C p is the TM concentration (mg kg −1 ) in the edible parts of the four leafy vegetables, MIDVC is the mean individual daily vegetable consumption (kg d −1 ), and TDI v is the tolerable daily intakes through oral ingestion of vegetables (mg kg −1 -BW d −1 ). Based on the Nutrition and Health Survey report and vegetable calorie counts, the MIDVC in Taiwan during 2013–2016 was 0.133 kg d −1 [ 43 ].…”

“…The hazard quotient (HQ v ) was calculated in accordance with Chen et al [ 43 ] to assess the health risk of TM through oral ingestion of vegetables using Equation (1), where C p is the TM concentration (mg kg −1 ) in the edible parts of the four leafy vegetables, MIDVC is the mean individual daily vegetable consumption (kg d −1 ), and TDI v is the tolerable daily intakes through oral ingestion of vegetables (mg kg −1 -BW d −1 ). Based on the Nutrition and Health Survey report and vegetable calorie counts, the MIDVC in Taiwan during 2013–2016 was 0.133 kg d −1 [ 43 ]. The TDIs of Cd, Cu, Ni, and Zn set by the European Food Safety Authority (EFSA) [ 52 , 53 ] and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) [ 54 , 55 ] were 0.36, 500, 2.8, and 300 μg kg −1 -BW d −1 , respectively.…”

Ecological and Health Risk of Soils, Sediments, and Water Contamination

“…Biochar from rice husk was applied into a cadmium (Cd) contaminated soil by Chen et al [7]. Lettuce (Lactuca sative) and pak-choi (Brassica chinensis) were planted in the biochar-amended soil to observe the accumulation, translocation, and chemical forms of Cd in the leafy vegetables.…”