Co-transport of biochar colloids with organic contaminants in soil column

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RESEARCH ARTICLE

Co-transport of biochar colloids with organic contaminants in soil column Rashida Hameed 1 & Cheng Lei 1 & Jing Fang 2 & Daohui Lin 1,3 Received: 1 June 2020 / Accepted: 23 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract Co-transport of biochar (BC) colloids with coexisting organic contaminants (OCs) in soil involves complex interactions among BC colloids, OCs, and soil particles, which is significant for the environmental application and risk assessment of BC and yet has not been well addressed. This study explored co-transports of three typical OCs (i.e., phenanthrene (PHN), atrazine (ATZ), and oxytetracycline (OTC)) and BC colloids obtained from bulk BCs with different charring temperatures (200–700 °C) and particle sizes (250 nm, 500 nm, and 1 μm) in a soil column of 9 cm in height. Considerable transport of BC colloids alone was observed and the maximum breakthrough concentration (C/Co) increased from 0.08 to 0.77 as the charring temperature decreased from 700 to 200 °C. The mobilities of PHN, OTC, and ATZ alone were very low but were greatly increased by co-transports with BC colloids, and their maximum C/Co values were within 0.05–0.33, 0.03–0.44, and 0.05–0.62, respectively, in the absence and presence of various BC colloids. The enhancement effect of BC colloids on the OC transport decreased with increasing charring temperature or particle size of BC colloids. BC colloids mainly acted as a vehicle to facilitate the transport of OCs, and dissolved organic carbon from BC colloids also contributed to the increased mobility of OCs in dissolved form. These findings provide new insights into co-transport of BC colloids and contaminants in soil. Keywords Biochar colloids . Dissolved organic carbon . Organic contaminants . Co-transport . Soil column

Introduction Biochar (BC) has gained great interests from scientists, farmers, policymakers, and investors (Ahmad et al. 2014; Lehmann 2007; Lian and Xing 2017), especially for bulk BC (0.04–20 mm), which is frequently applied for agricultural and environmental purposes (Gao and Wu 2013). Once in soil, bulk BC can be fragmented and disintegrated by biotic Responsible Editor: Zhihong Xu Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10606-5) contains supplementary material, which is available to authorized users. * Daohui Lin [email protected] 1

Department of Environmental Science, Zhejiang University, Hangzhou 310058, China

2

School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China

3

Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China

and abiotic reactions, releasing nano- and micro-scale BC colloids (Heymann et al. 2014; Mia et al. 2017) and dissolved organic carbon (DOC) to soil solution. According to Fang et al. (2020), 16.0–50.2% of bulk BC in mass are BC colloids, and the extent is related to charring temperature and biomass source.