Effect of dissolved organic carbon from sludge, Rice straw and spent coffee ground biochar on the mobility of arsenic in soil

Hye-Bin Kim; Seon-Hee Kim; Eun-Ki Jeon; Do-Hyung Kim; Daniel C W Tsang; Daniel S Alessi; Eilhann E Kwon; Kitae Baek

doi:10.1016/j.scitotenv.2018.04.406

Effect of dissolved organic carbon from sludge, Rice straw and spent coffee ground biochar on the mobility of arsenic in soil

Sci Total Environ. 2018 Sep 15:636:1241-1248. doi: 10.1016/j.scitotenv.2018.04.406. Epub 2018 May 9.

Authors

Hye-Bin Kim¹, Seon-Hee Kim¹, Eun-Ki Jeon¹, Do-Hyung Kim², Daniel C W Tsang³, Daniel S Alessi⁴, Eilhann E Kwon⁵, Kitae Baek⁶

Affiliations

¹ Department of Environmental Engineering and Soil Environment Research Center, Chonbuk National University,Jeonju, Jeollabukdo 57896, Republic of Korea.
² Korea Environmental Industry and Technology Institute, Seoul 03367, Republic of Korea.
³ Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
⁴ Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E3.
⁵ Department of Environment and Energy, Sejong University, Seoul 05006, Republic of Korea.
⁶ Department of Environmental Engineering and Soil Environment Research Center, Chonbuk National University,Jeonju, Jeollabukdo 57896, Republic of Korea. Electronic address: kbaek@jbnu.ac.kr.

PMID: 29913586
DOI: 10.1016/j.scitotenv.2018.04.406

Abstract

To date, studies on the mobility of arsenic (As) in soil amended with biochar have primarily relied on broad empirical observations, resulting in a gap between the behavior of As in amended soil and the chemical mechanisms controlling that behavior. This study focuses on the influence of abiotic factors in As mobility in As-contaminated soils amended with biochar. In order to understand the leaching of DOC and phosphate across a range of biomass feedstock and pyrolysis temperature, rice straw and granular sludge from an anaerobic digester were pyrolyzed at 300, 550, and 700 °C, and subjected to leaching studies by mixing air dried soil with 10 wt% of biochar at a soil: water ratio of 1:1(w/v). The concentration of DOC in the presence of granular sludge biochar and rice straw biochar increased from 190 mg L^-1 to 2605 mg L^-1 and 1192 mg L^-1, respectively, which considerable accelerated the mobilization of Fe and As. More specifically, DOC drove the reduction of Fe(III) to Fe(II). Our results suggest enhanced release of As via the reductive dissolution of iron oxides, including by the chelating-enhanced dissolution of Fe oxides, and competitive desorption by DOC and phosphate from biochar. The influence of DOC and phosphate was further evaluated using realistic application amounts (1, 3, and 5 wt%) of biochars derived from pyrolysis of granular sludge, rice straw and spent coffee ground at 300 and 550 °C. The results from these experiments further confirm that DOC is a key factor for influencing the mobility of As in the amendment of biochar to As-contaminated soil, which indicates that biochar having low levels of leachable carbon should be amended to As-contaminated soils, and with caution.

Keywords: Arsenic mobility; Biochar amendment; Dissolved organic matter; Fe-DOM complexation; Reductive dissolution; Ternary complexes.