Ecotoxicological characterization of biochars: Role of feedstock and pyrolysis temperature

Domene X., Enders A., Hanley K., Lehmann J. (2015) Ecotoxicological characterization of biochars: Role of feedstock and pyrolysis temperature. Science of the Total Environment. 512-513: 552-561.
Link
Doi: 10.1016/j.scitotenv.2014.12.035

Abstract:

Seven contrasting feedstocks were subjected to slow pyrolysis at low (300 or 350°C) and high temperature (550 or 600°C), and both biochars and the corresponding feedstocks tested for short-term ecotoxicity using basal soil respiration and collembolan reproduction tests. After a 28-d incubation, soil basal respiration was not inhibited but stimulated by additions of feedstocks and biochars. However, variation in soil respiration was dependent on both feedstock and pyrolysis temperature. In the last case, respiration decreased with pyrolysis temperature (r=-0.78; p<0.0001, n=21) and increased with a higher volatile matter content (r=0.51; p<0.017), these two variables being correlated (r=-0.86, p<0.0001). Collembolan reproduction was generally unaffected by any of the additions, but when inhibited, it was mostly influenced by feedstock, and generally without any influence of charring itself and pyrolysis temperature. Strong inhibition was only observed in uncharred food waste and resulting biochars. Inhibition effects were probably linked to high soluble Na and NH4 concentrations when both feedstocks and biochars were considered, but mostly to soluble Na when only biochars were taken into account. The general lack of toxicity of the set of slow pyrolysis biochars in this study at typical field application rates (≤20Mgha-1) suggests a low short-term toxicity risk. At higher application rates (20-540Mgha-1), some biochars affected collembolan reproduction to some extent, but only strongly in the food waste biochars. Such negative impacts were not anticipated by the criteria set in currently available biochar quality standards, pointing out the need to consider ecotoxicological criteria either explicitly or implicitly in biochar characterization schemes or in management recommendations. © 2014 Elsevier B.V.

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Short-term mesofauna responses to soil additions of corn stover biochar and the role of microbial biomass

Domene X., Hanley K., Enders A., Lehmann J. (2015) Short-term mesofauna responses to soil additions of corn stover biochar and the role of microbial biomass. Applied Soil Ecology. 89: 10-17.
Link
Doi: 10.1016/j.apsoil.2014.12.005

Abstract:

Biochar additions have been suggested to influence soil microbial communities that, through a cascade effect, may also impact soil fauna. In turn, any direct biochar effects on fauna can influence microbial communities through grazing, physical fragmentation of organic debris (and biochar) and modifying soil structure. If biochar creates a favorable environment for soil microorganisms, it is also plausible for fauna to be attracted to such microbially enriched habitats. However, how soil fauna respond to biochar addition to soil and what are the main factors that drive their behavior has rarely been experimentally addressed. Therefore, the behavior of two mesofauna species was assessed as a result of corn stover biochar (slow pyrolysis at 600°C) additions to a loamy temperate soil, after preincubation for 2, 17, 31 and 61d, and related to variations in microbial biomass and activity. Microbial biomass increased by 5-56% and activity by 6-156% with increasing biochar rates for the different preincubation times. Over the incubation time, microbial biomass did not change or increased at most 15% with the different biochar rates, while in turn microbial activity decreased steadily (around 70-80% at day 61). Enchytraeids generally did not show avoidance or preference to biochar when provided with an alternative unamended soil, while collembolans often showed avoidance responses. However, collembolan avoidance to biochar decreased or disappeared in biochar mixtures with higher microbial biomass and soluble NH4-N content, agreeing with the plausible role of microorganisms to potentially attract soil fauna after biochar applications. Avoidance response was mainly explained by environmental preferences of the test species and not by any toxic effect of the biochar in this study. However, avoidance after the application of biochar may still need to be considered due to the potential negative impacts of individuals' migration on soil ecosystem functioning. © 2014 Elsevier B.V.

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Investigating the Use of Multi-Gaussian Nonlinear Regressions to Separate Collembolan Size Classes for Soil Quality Assessment

Marks E.A.N., Molowny-Horas R., Domene X. (2015) Investigating the Use of Multi-Gaussian Nonlinear Regressions to Separate Collembolan Size Classes for Soil Quality Assessment. Water, Air, and Soil Pollution. 226: 0-0.
Link
Doi: 10.1007/s11270-015-2503-6

Abstract:

Previous studies with bioindicator organisms have used somatic length distributions, i.e., population structure, to understand the effects of management, environment, or a potential contaminant on populations. We describe a statistical approach to separate somatic length classes of Folsomia candida juveniles as an endpoint for the assessment of changes in population structure. Reproduction-survival bioassays were carried out with five different biochars applied at increasing concentrations. Multi-Gaussian models parameterized juvenile size class cohorts, and the biomass of each size class cohort was estimated. Population structure was modified by both material type as well as concentration. Both biomass and population structure were sensitive to effects not reflected in juvenile number, the classic endpoint. Treatments with more size classes and larger individuals were taken to represent favorable conditions, and less size classes and smaller individuals indicated less favorable conditions. This extension of the standardized test provided additional information about the demography of the population. © 2015 Springer International Publishing Switzerland.

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