Ke Sun , Mingjie Kang , Zheyun Zhang , Jie Jin , Ziying Wang , Zezhen Pan , Dongyu Xu , Fengchang Wu , and Baoshan Xing (2013). “Impact of De-Ashing Treatment on Biochar Structural Properties and Potential Sorption Mechanisms of Phenanthrene.” Environmental Science and Technology (ES&T), September 11, 2013. DOI: 10.1021/es4026744.
Abstract: Knowledge of the mineral effects of biochars on their sorption of hydrophobic organic contaminants (HOCs) is limited. Sorption of phenanthrene (PHE) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at two heating treatment temperatures (HTTs) (450 and 600 oC) and their corresponding de-ashed biochars was investigated. The decreased surface polarity and increased bulk polarity of biochars after de-ashing treatment indicated that abundant minerals of biochars benefit external exposure of polar groups associated organic matter (OM). Organic carbon (OC)-normalized distribution coefficients (Koc) of PHE by biochars generally increased after de-ashing, likely due to enhancement of favorable and hydrophobic sorption sites caused by mineral removal. Positive correlation between PHE logKoc by PLABs and bulk polarity combined with negative correlation between PHE logKoc values by ANIBs and surface polarity suggested PLABs and ANIBs have different sorption mechanisms, probably attributed to their large variation of ash content because minerals influenced OM spatial arrangement within biochars. Results of this work could help us better understand the impact of minerals, bulk/surface polarity, and sorption domain arrangement of biochars on their HOCs sorption and predict the fate of HOCs in soils after biochar application.
Liqiang Cui, Jinlong Yan, Yage Yang, Lianqing Li, Guixiang Quan, Cheng Ding, Tianming Chen, Qiang Fu, Andrew Chang (2013). “Influence of Biochar on Microbial Activities of Heavy Metals Contaminated Paddy Fields.” BioResources 8(4). Open source. Available online.
Biochar (BC) amendments might decrease the bioavailability of metals in soils that are contaminated with heavy metals. In general, soil microbial communities are sensitive to changes in soil property changes. Microbial communities were tested in a Cd- and Pb-polluted paddy field in southern China. BC was applied as a basal soil amendment before rice transplantation in 2009. The BC was applied at rates of 0, 10, 20, and 40 tons per hectare. Soil heavy metal fractions with sequential extraction procedure, soil microorganisms, and enzymes were monitored in 2011. The soil pH and soil organic carbon (SOC) were significantly increased by 2% to 5% and 16% to 51% under BC amendment, respectively. Compared to the non-BC treatment, the cadmium (Cd) and lead (Pb) acid-soluble fraction concentrations were significantly decreased by 15.3% to 26.7% and 18.2% to 30.9%. The Cd and Pb reducible fraction were decreased by 13.5% to 25.6% and 21.9% to 23.53%.The Cd and Pb oxidizable fraction by 15.4% to 69.2% and 22.7% to 29.3% with BC application, respectively. The populations of actinomycetes and fungi were increased by 19.0% to 38.5% and 3.7 to 9.3 times, respectively. Meanwhile, BC significantly increased the cellulose, urine enzyme, neutral phosphatase, and sucrase activities by 117.4% to 178.3%, 31.1% to 37.6%, 29.7% to 193.8%, and 36.5% to 328.6%, respectively. BC amendment offers a basic option to reduce Cd and Pb bioavailability and change the fractions. The BC also increases microorganism quantity and soil enzyme activity.