Effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil

Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611, United States.
Chemosphere (Impact Factor: 3.34). 07/2012; 89(11):1467-71. DOI: 10.1016/j.chemosphere.2012.06.002
Source: PubMed


When applied to soils, it is unclear whether and how biochar can affect soil nutrients. This has implications both to the availability of nutrients to plants or microbes, as well as to the question of whether biochar soil amendment may enhance or reduce the leaching of nutrients. In this work, a range of laboratory experiments were conducted to determine the effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil. A total of thirteen biochars were tested in laboratory sorption experiments and most of them showed little/no ability to sorb nitrate or phosphate. However, nine biochars could remove ammonium from aqueous solution. Biochars made from Brazilian pepperwood and peanut hull at 600°C (PH600 and BP600, respectively) were used in a column leaching experiment to assess their ability to hold nutrients in a sandy soil. The BP600 biochar effectively reduced the total amount of nitrate, ammonium, and phosphate in the leachates by 34.0%, 34.7%, and 20.6%, respectively, relative to the soil alone. The PH600 biochar also reduced the leaching of nitrate and ammonium by 34% and 14%, respectively, but caused additional phosphate release from the soil columns. These results indicate that the effect of biochar on the leaching of agricultural nutrients in soils is not uniform and varies by biochar and nutrient type. Therefore, the nutrient sorption characteristics of a biochar should be studied prior to its use in a particular soil amendment project.

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    • "Ammonium retention by biochar may be readily explained by electrostatic adsorption to negatively charged oxygen-containing surface functional groups (Cheng et al., 2006; Hale et al., 2013). Freshly produced biochars typically have very low ability to adsorb ammonium (Yao et al., 2012). Over time, biochar surfaces are oxidized and cation retention increases (Cheng et al., 2008, 2014), to levels greater than other organic matter in soils (Liang et al., 2006). "
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    ABSTRACT: The objective of this work was to investigate the retention mechanisms of ammonium in aqueous solution by using progressively oxidized maple wood biochar at different pH values. Hydrogen peroxide was used to oxidize the biochar to pH values ranging from 8.1 to 3.7, with one set being adjusted to a pH of 7 afterwards. Oxidizing the biochars at their lowered pH did not increase their ability to adsorb ammonium. However, neutralizing the oxygen-containing surface functional groups on oxidized biochar to pH 7 increased ammonia adsorption two to three-fold for biochars originally at pH 3.7-6, but did not change adsorption of biochars oxidized to pH 7 and above. The adsorption characteristics of ammonium are well described by the Freundlich equation. Adsorption was not fully reversible in water, and less than 27% ammonium was desorbed in water in two consecutive steps than previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 2M KCl increased from 34% to 99% of ammonium undesorbed by both preceding water extractions with increasing oxidation, largely irrespective of pH adjustment. Unrecovered ammonium in all extractions and residual biochar was negligible at high oxidation, but increased to 39% of initially adsorbed amounts at high pH, likely due to low amounts adsorbed and possible ammonia volatilization losses. Copyright © 2015. Published by Elsevier Ltd.
    Chemosphere 06/2015; 138:120-126. DOI:10.1016/j.chemosphere.2015.05.062 · 3.34 Impact Factor
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    • "In addition, biochar amendment can, in some instances, increase soil fertility and crop yield (Major et al., 2010), improve soil physical and chemical properties such as water holding and nutrient retention capacity (Bell and Worrall, 2011; Karhu et al., 2011). Biochar properties are strongly affected by their peak pyrolysis temperature (Yao et al., 2012; Park et al., 2013). As pyrolysis temperature increases, the degree of carbonization of the feedstock increases, as indicated by increased carbon (C) content as well as 0045-6535/Ó 2015 Elsevier Ltd. "
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    ABSTRACT: It is unclear how the properties of biochar control its ability to sorb metals. In this work, physicochemical properties of a variety of biochars, made from four types of feedstock at three pyrolysis temperatures (300, 450 and 600°C) were compared to their ability to sorb arsenic (As) and lead (Pb) in aqueous solutions. Experimental results showed that both feedstock types and pyrolysis temperature affected biochar's production rate, i.e., ratio of mass of biochar and biomass, thermal stability, elemental composition, non-combustible component (NCC) content, pH values, surface areas and thus their sorption ability to the two metals in aqueous solution. In general, the high temperature biochars had low O/C and H/C ratios, were more carbonized with larger surface area, and were more concentrated with alkaline cations. In addition, biochars made from woody feedstocks had larger surface area, but lower NCC contents than that made from grasses under the same conditions. Although all the tested biochars removed both As and Pb from aqueous solutions, they showed different sorption abilities because of the variations in properties. Statistical analyses suggested that feedstock type affected the sorption ability of the biochars to both As and Pb significantly (p<0.001). Pyrolysis temperature, however, showed little influence on biochar sorption of Pb in aqueous solutions. Statistical analyses also showed that electrostatic interaction played an important role in controlling the sorption of both As(V) and Pb(II) onto the biochar. Other mechanisms, such as precipitation and surface complexation, could also control the sorption of Pb(II) onto the biochars. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Chemosphere 05/2015; 134:257-262. DOI:10.1016/j.chemosphere.2015.04.062 · 3.34 Impact Factor
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    • "There is evidence that biochar increases nutrient retention [7] [8] [10]-[14] [17] [18] [22] in soil and that it can absorb nutrients from solution. This opens the possibility of using biochar as an adsorbent in wastewater treatment and then applying the biochar. "
    Open Journal of Soil Science 01/2015; 05(02):39-44. DOI:10.4236/ojss.2015.52004
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