Risk assessment of low-temperature biochar used as soil amendment on soil mesofauna

Abstract

Biochar as a carbon-rich highly porous substance has been proposed for use in agriculture and horticulture as a soil amendment. One of the main concerns of this application of biochar is its potential contamination with heavy metals (HMs) and polycyclic aromatic hydrocarbons. The aim of this research was to access the environmental risk of biochar used as a soil amendment on soil mesofauna (mites and springtails). We conducted both field and laboratory experiments with the use of wood-chip biochar from low-temperature (300 °C) flash pyrolysis. Biochar was free from polycyclic aromatic hydrocarbons (PAH), and the concentration of all tested toxic compounds was very low or even under the level of detection. Both the results of field and laboratory studies show no toxic effects on soil mesofauna. In the field studies, the biochar application of 50 t/ha in maize and oilseed rape crops significantly increased the mean number of mesofauna. This change probably resulted from improved soil chemical properties (in particular organic carbon content and cation exchange capacity) upon biochar addition. The results of the avoidance test with the use of springtail species Folsomia candida showed the possible short-term toxicity risk from a dose of 5%. The results of the reproduction test indicate the negative response of F. candida from the rate of 25% (higher than the field dose, which corresponds to 10% in laboratory tests). The reason for the short-term toxicity might be the considerable increase in soil pH after biochar addition. To our knowledge, this is the first study that has looked so widely into the effect of biochar on soil mesofauna. We encourage further studies into the risk assessment of biochar on soil organisms in both a controlled laboratory environment and in the open field.

Visualizing the emerging trends of biochar research and applications in 2019: a scientometric analysis and review

“…The toxicities of biochar were largely dependent on raw materials, pyrolysis temperature, and particle sizes of biochar (Liu et al 2019;Prodana et al 2019;Zhang et al 2019b, c). The elevated pH, PAHs and heavy metals contents, reactive oxygen species (ROS) levels upon the incorporation of biochar were the main reasons for the toxicities of biochar to soil biota and aquatic organisms (Gruss et al 2019;Liu et al 2019;Zhang et al 2019d). Hilber et al (2019) investigated the desorption resistance of PAHs (as an indirect measure of their bioaccessibility) in biochar as feed additive in cow ruminal liquid, and their results indicated that biochar containing < 10 mg/kg dw PAHs would not pose an increased unintended consequence to ruminants, which provided a novel and relative realistic method to assess these unintended health consequences of biochar (Hilber et al 2019).…”

“…To decrease the toxicities to microorganisms, it is required to select appropriate biochar as carriers for microorganism immobilization. The strong alkalinity of biochar caused by abundant minerals may also reduce microbial activity (Gruss et al 2019). This toxic effect could be reduced by washing biochar with acids and water to remove the minerals in biochar or selecting feedstocks which can result in neutral biochar.…”

The Effect of Biochar Used as Soil Amendment on Morphological Diversity of Collembola

“…Table 2. Soil properties after biochar application in oilseed rape and maize (sourced from Gruss et al [41]).…”

“…The chemical characteristic of biochar properties used in the experiment (sourced from Gruss et al[41]). …”

Role of Prosopis juliflora biochar in poly-aromatic hydrocarbon remediation using Trifolium alexandrinum L.

“…The plant growth parameters were examined at different time intervals in field, and samples were further stored and analyzed under laboratory conditions. The low-temperature P. juliflora biochar used in the experimental study had a high carbon content and ability for nutrient storage, and these results were in close proximity with [16,20,24].…”