“The short term effect of the soil amendments; activated carbon, biochar and ferric oxyhydroxide, on bacteria and invertebrates.” Environmental Science & Technology, published on the web June 26, 2013. Online at http://dx.doi.org/10.1021/es400917g
Abstract: The aim of the present study was to evaluate the secondary ecotoxicological effects of soil amendment materials that can be added to contaminated soils in order to sequester harmful pollutants. To this end, a non-polluted agricultural soil was amended with 0.5, 2 and 5 % of the four amendments; powder activated carbon (PAC), granular activated carbon (GAC), corn stover biochar and ferric oxyhydroxide powder which have previously been proven to sequester pollutants in soil. The resulting immediate effects (i.e. without aging the mixtures before carrying out tests) on the springtail Folsomia candida, the earthworm species Aporectodea caliginosa and Eisenia fetida, the marine bacteria Vibrio fischeri, a suite of ten prokaryotic species and a eukaryote (the yeast species Pichia anomalia) were investigated. Reproduction of F. candida was significantly increased compared to the unamended soil when 2 % biochar was added to it. None of the treatments caused a negative effect on reproduction. All amendments had a deleterious effect on the growth of A. caliginosa when compared to the unamended soil, except the 0.5 % amendment of biochar. In avoidance tests, E. fetida preferred biochar compared to all other amendments including the unamended soil. All amendments reduced the inhibition of luminescence to V. fischeri, i.e. were beneficial for the bacteria, with PAC showing the greatest improvement. The effects of the amendments on the suite of prokaryotic species and the eukaryote were variable, but overall the 2 % biochar dose provided the most frequent positive effect on growth. It is concluded that the four soil amendments had variable but never strongly deleterious effects on the bacteria and invertebrates studied here during the respective recommended experimental test periods.
“Influence of biochar on isoproturon partitioning and bioaccessibility in soil”. Environmental Pollution 113(10), 44-50. Online at http://dx.doi.org/10.1016/j.envpol.2013.05.042
Abstract: The influence of biochar (5%) on the loss, partitioning and bioaccessibility of 14C-isoproturon (14C-IPU) was evaluated. Results indicated that biochar had a dramatic effect upon 14C-IPU partitioning: 14C-IPU extractability (0.01 M CaCl2) in biochar-amended treatments was reduced to <2% while, 14C-IPU extractability in biochar free treatments decreased with ageing from 90% to 40%. A partitioning model was constructed to derive an effective partition coefficient for biochar:water (KBW of 7.82 × 104 L kg−1). This was two orders of magnitude greater than the apparent Kfoc value of the soil organic carbon:water (631 L kg−1). 14C-radiorespirometry assays indicated high competence of microorganisms to mineralise 14C-IPU in the absence of biochar (40.3 ± 0.9%). Where biochar was present 14C-IPU mineralisation never exceeded 2%. These results indicate reduced herbicide bioaccessibility. Increasing IPU application to ×10 its recommended dose was ineffective at redressing IPU sequestration and its low bioaccessibility.
“Biochar mitigates negative effects of salt additions on two herbaceous plant species.” Journal of Environmental Management 129, 62-68. Online at http://dx.doi.org/10.1016/j.jenvman.2013.05.057
Abstract: Addition of pyrolyzed biomass (“biochar”) to soils has commonly been shown to increase crop yields and alleviate plant stresses associated with drought and exposure to toxic materials. Here we investigate the ability of biochar (at two dosages: 5 and 50 t ha−1) to mitigate salt-induced stress, simulating road salt additions in a factorial glasshouse experiment involving the broadleaved herbaceous plants Abutilon theophrasti and Prunella vulgaris. Salt additions of 30 g m−2 NaCl to unamended soils resulted in high mortality rates for both species. Biochar (Fagus grandifolia sawdust pyrolyzed at 378 °C), when applied at 50 t ha−1 as a top dressing, completely alleviated salt-induced mortality in A. theophrasti and prolonged survival of P. vulgaris. Surviving A. theophrasti plants that received both 50 t ha−1 biochar and salt addition treatments showed growth rates and physiological performance similar to plants without salt addition. Biochar treatments alone also substantially increased biomass of P. vulgaris, with a ∼50% increase relative to untreated controls at both biochar dosages. Biochar did not significantly affect photosynthetic carbon gain (Amax), water use efficiency, or chlorophyll fluorescence (Fv/Fm) in either species. Our results indicate that biochar can ameliorate salt stress effects on plants through salt sorption, suggesting novel applications of biochar to mitigate effects of salinization in agricultural, urban, and contaminated soils.