Wei Zhang - Transport and retention of biochar particles in porous media: effect of pH, ionic strength, and particle size

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      Publication Details (including relevant citation   information): Zhang, Wei, Niu, Jianzhi, Morales,   Verónica L., Chen, Xincai, Hay, Anthony G., Lehmann, Johannes,   Steenhuis, Tammo S., Ecohydrol., 2010,   3 (4), pp 497-508

      Abstract: Biochar land application can   potentially be used for carbon sequestration, improving soil   quality, and reducing non-point source pollution. Understanding   biochar mobility is important because its transport in soil   greatly influences its stability, the dynamics of soil microbial   communities and organic matter, and the movement of   biochar-associated contaminants. Here, the transport of biochar   particles was studied in saturated and unsaturated sand columns   by measuring breakthroughs of biochar pulse under three pH and   two ionic strength (IS) levels. Breakthrough curves (BTCs) were   fitted to a convection–dispersion model with kinetic and   equilibrium deposition sites to estimate the key transport   parameters (e.g. biochar deposition rate coefficients). Biochar   retention was enhanced by lowering pH and increasing IS,   corroborating the trends of fitted deposition rate coefficients.   Under both saturated and unsaturated conditions, effluent mass   recoveries decreased, respectively, by a factor of 6·6 or 15 when   pH decreased from 10 to 4 at 10 mM IS, and by a factor of 1·4 or   3·9 when IS increased from 10 to 100 mM at pH 7. Biochar   retention was greater in unsaturated media, implying that   saturated flow elutes more biochar particles. The particles   larger than 5·4% of median grain diameter were filtered out of   suspension during passage through the media; whereas, the   retention of smaller particles was clearly dependent on solution   chemistry. Similar to other types of colloids, this study   highlights the importance of pH, IS, particle size, and soil   water saturation in controlling biochar movement by soil matrix   flow. Copyright © 2010 John Wiley & Sons, Ltd.

      Address (URL): http://dx.doi.org/10.1002/eco.160