Comparing biochar and hydrochar for reducing the risk of organic contaminants in polluted river sediments used for growing energy crops

• Published in: The Science of the total environment Vol. 843; p. 157122
• Main Authors: Maletić, Snežana, Isakovski, Marijana Kragulj, Sigmund, Gabriel, Hofmann, Thilo, Hüffer, Thorsten, Beljin, Jelena, Rončević, Srđan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-10-2022
• Subjects: Bioaccessible fraction; Biochar; Hydrochar; Phytotoxicity; River sediment; Hydrochar; River sediment; Phytotoxicity; Biochar; Bioaccessible fraction
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.157122

In Europe alone, >200 million m3 of river sediments are dredged each year, part of which are contaminated to such an extent that they have to be landfilled. This study compares the use of biochar and hydrochar for the remediation of sediment contaminated with pentachlorobenzene, hexachlorobenzene, lindane, trifluralin, alachlor, simazine, and atrazine with the motivation to make sediments contaminated by such priority substances usable as arable land for growing energy crops. Biochar and hydrochar originating from Miscanthus giganteus and Beta vulgaris shreds were compared for their potential to reduce contaminant associated risk in sediments. Specifically, by investigating the effects of sorbent amendment rate (1, 5, and 10 %) and incubation time (14, 30, and 180 d) on contaminant bioaccessibility, toxicity to the bacteria Vibrio fischeri, as well as toxicity and plant uptake in Zea mays. Biochar reduced contaminant bioaccessibility up to five times more than hydrochar. The bioaccessibility of contaminants decreased up to sevenfold with increasing incubation time, indicating that the performance of carbonaceous sorbents may be underestimated in short-term lab experiments. Biochar reduced contaminants toxicity to Vibrio fischeri, whereas hydrochar was itself toxic to the bacteria. Toxicity to Zea mays was determined by contaminant bioaccessibility but also sorbent feedstock with cellulose rich Beta vulgaris based sorbents exhibiting toxic effects. The plant uptake of all contaminants decreased after sorbent amendment.
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•Biochars and hydrochars were compared for risk reduction of contaminated sediments.•Biochar reduced contaminant bioaccessibility in sediment below 10 %.•Increasing incubation time up to 180 days, reduced contaminant bioaccessibility.•Beta vulgaris based sorbents inhibited germination of Zea mays by 80–100 %.