Effect of sewage sludge derived compost or biochar amendment on the phytoaccumulation of potentially toxic elements and radionuclides by Chinese cabbage

• Published in: Journal of environmental management Vol. 293; p. 112955
• Main Authors: Černe, Marko, Palčić, Igor, Major, Nikola, Pasković, Igor, Perković, Josipa, Užila, Zoran, Filipović, Vilim, Romić, Marija, Goreta Ban, Smiljana, Jaćimović, Radojko, Benedik, Ljudmila, Heath, David John, Ban, Dean
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2021
• Subjects: Aerobic stabilisation; Edible tissue uptake; Health risk; Pyrolysis; Radioisotopes; Trace metals; Radioisotopes; Pyrolysis; Edible tissue uptake; Aerobic stabilisation; Trace metals; Health risk
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.112955

This study set out to evaluate the effect of using sewage sludge-derived compost (SSC) or biochar (SSB) as a soil amendment on the phytoaccumulation of potentially toxic elements, PTE (Cd, Cr, Cu, Ni, Pb, Zn) and natural radionuclides (238U and 232Th) by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) in terra rossa and rendzina soils, which are the two common soil types in Croatia. The experiment consisted of a greenhouse pot trial using a three-factor design where soil type, sludge post-stabilisation procedure and amendment rate (12 and 120 mgP/L) were the main factors. At harvest, the concentrations of analytes in the substrate, leaves and roots were measured, from which the edible tissue uptake (ETU) and concentration ratios (CR) were determined. Also, the average daily dose (ADD) and hazard quotient (HQ) were determined to assess the health risk, as well as soil contamination factor (CF). The results showed that neither adding SSC nor SSB affected the soil loading at the rates applied, suggesting a low risk of soil contamination (CF ≤ 1). The ETU of Cd, Cu, and Zn were 0.0061, 1.23, and 0.91 mg/plant from compost-amended soil and 0.0046, 0.78 and 0.65 mg/plant for biochar-amended soil, respectively. This difference suggests that their ETU was higher in compost-amended soils than in soils treated with biochar. The CR data indicate that the bioavailability of Cu (CR of 5.30) is highest at an amendment rate of 12 mgP/L, while for Zn (CR of 0.69), the highest bioaccumulation was observed with an amendment rate of 120 mgP/L. Translocation of Cr, Ni, Pb and 238U to the leaves was limited. Overall, the HQ (<1) for Cd, Cu and Zn in the edible parts confirmed that consuming Chinese cabbage does not threaten human health. Similarly, the daily intake of 232Th remained below the limit (3 μg) set by ICRP, suggesting no radiological risk. Finally, although the amendment rate, which was 10-times the amount stipulated in Croatian regulation and the CR ranged from 0.007 to 5.30, the precautionary principle is advised, and the long-term impact of sewage sludge derived compost or biochar on different plant groups (incl. root vegetables) at the field-scale is recommended.
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•Sewage sludge compost or biochar amendment did not result in soil contamination.•Biochar amendment reduced Cd, Cu and Zn edible tissue uptake relative to compost use.•No evidence of phytoaccumulation of Cr, Ni, Pb and 238U in Chinese cabbage leaves.•Levels of Cd, Cu, Zn and 232Th in the edible tissues does not pose a health risk.