Increased concentration of PAH derivatives in biochar-amended soil observed in a long-term experiment.

During biochar preparation or application some toxic substances may be formed. The established limitations of the content of polycyclic aromatic hydrocarbons (PAHs) aim to monitor the fate of PAHs in the life cycle of biochar. The latest studies have revealed that besides PAHs, some of their derivatives with confirmed toxicity are formed. There has been no policy regards PAH derivatives in biochar yet. The aim of the presented studies was the estimation the changes in the content of PAHs and their derivatives during the agricultural application of biochar. A pot experiment with grass revealed that in a short time, both the content of PAHs and their derivatives was reduced. Similarly, when biochar was added to soil in a long-term experiment, the content of determined derivatives was below the limit of detection, whereas interestingly, the content of pristine PAHs increased with time. Co-addition of biochar and sewage sludge increased the content of PAHs and their derivatives indicating potential environmental hazard due to their presence. However, the key point is the estimation of the bioavailability of PAHs and their derivatives as only the bioavailable fraction is revealing the environmental hazard.

Chemical properties of soil determine the persistence and bioavailability of polycyclic aromatic hydrocarbons in sewage sludge- or sewage sludge/biomass-derived biochar-amended soils.

In this study the persistence (organic solvent extractable) and bioavailability (freely dissolved) of polycyclic aromatic hydrocarbons (PAHs) in soils with various properties amended with sewage sludge (BCSSL)- or sewage sludge/biomass (BCSSLW)-derived biochars was examined. Biochars produced at 600 °C were applied to soils (acidic, neutral, or alkaline) at a dose of 2% and subsequently incubated for 180 days. Here, the use of biochars regarding the soil's type was examined for the first time. Depending on the soil pH and the feedstock, the content of sum of 16 organic solvent extractable PAHs was found to decrease from 7.5 to 37% (soil + BCSSL) and from 24 to 40% (soil + BCSSLW). The decrease in the content of sum of 16 freely dissolved PAHs ranged from 18 to 36% (soil + BCSSL) and from 17 to 54% (soil + BCSSLW). In acidic BCSSL-amended soil and the alkaline BCSSLW-amended soil no statistically significant differences in the content of sum of 16 freely dissolved PAHs were noted between the beginning and end of the study. BCSSLW was characterized by a greater reduction content of organic solvent extractable PAHs in the acidic and alkaline soils, while in the neutral one - BCSSL. In turn, a larger reduction in freely dissolved PAH content in the acidic and neutral soils could be seen in the presence of BCSSLW, whereas in the alkaline soil in the presence of BCSSL. The persistence and bioavailability of PAHs in the biochar-amended soils were closely related to the chemical properties of these soils. This was confirmed by numerous statistically significant (P ≤ 0.05) relationships between organic solvent extractable PAHs and pH, cation exchange capacity, available magnesium, potassium and phosphorus, and dissolved organic carbon as well as between freely dissolved PAH and pH, dissolved organic carbon, available potassium and phosphorus content, and electrical conductivity.

Effect of carrier gas change during sewage sludge or sewage sludge and willow pyrolysis on ecotoxicity of biochar-amended soil.

Different pyrolysis conditions determine the properties of the biochar. The properties of biochar may affect directly or indirectly their influence on living organisms. The aim of this study was to determine the toxicity of biochar obtained under different conditions (temperature: 500 or 700 °C, carrier gas: N2 or CO2, feedstock: sewage sludge or sewage sludge/biomass mixture) after adding to the soil in long-term pot experiment (180 days). Biochars were added to the podzolic loamy sand at a 2% (w/w) dose. Samples were collected at the beginning of the experiment and after 30, 90 and 180 days. The bacteria Aliivibrio fischeri (luminescence inhibition - Microtox), the plant Lepidium sativum (root growth and germination inhibition test - Phytotoxkit F), and the invertebrate Folsomia candida (mortality and reproduction inhibition test - Collembolan test) were used as the test organisms. In the long-term perspective for most tests, changing the carrier gas from N2 to CO2 resulted in reduced toxicity of the biochar. A particularly beneficial effect of changing the gas to CO2 was observed for the solid-phase test with L. sativum. The CO2 during pyrolysis had the least beneficial effect on toxicity towards A. fischeri.

Low bioavailability of derivatives of polycyclic aromatic hydrocarbons in biochar obtained from different feedstock.

In the last years, there is great progress in the field of studies on the thermal transformation of wastes into valuable materials such as biochar. High-temperature processes, however, are connected with the formation of polycyclic aromatic hydrocarbons (PAHs) with confirmed toxicity. However, during pyrolysis, some derivatives containing oxygen, nitrogen, or sulfur can also be formed. Their toxicity is expected to be higher than parent PAHs. However, the key parameter in the agricultural application of carbonaceous materials is PAHs' bioavailability. The aim of the presented studies was the determination of the effect of various feedstock (wheat straw (Triticum L.), willow (Salix viminalis), sunflower, residues from softwood and hardwood, sewage sludges, and residues from biogas production) on the formation of PAHs and their derivatives (O-, N-PAHs) in biochar and their bioavailability. The results indicated that the content of total and bioavailable PAHs in obtained biochar was rather low. The concentration of total PAHs in plant-derived biochar reached 57 ± 3 ng g-1 - 181 ± 8 ng g-1, whereas sewage sludge-derived biochar contained from 121 ± 6 ng g-1 to 188 ± 9 ng g-1 of PAHs. The highest concentration of PAHs was noted in biochar obtained from residues from biochar production - up to 202 ± 9 ng g-1. The total concentration of bioavailable PAHs was lower and reached 2-4.45 ng L-1 for plant-derived biochar, 3-40 ng L-1 for sewage sludge-derived biochar. The highest content of bioavailable PAHs was noted in biochar obtained from residues from biogas production: 9-42 ng L-1 indicating that increased attention should be paid to using this type of biochar. Among PAHs derivatives, nitronaphthalene, 1-methyl-5-nitronaphthalene, 1-methyl-6-nitronaphthalene, 9,10-anthracenedione, 4H-cyclopenta(def)phenanthrene, nitropyrene were determined at various levels and their concentrations were from below the limit of detection (LOD) to 28 ng L-1 for plant-derived biochar, 3-16 ng L-1 for biochar obtained from residues from biogas production, and 5-45 ng L-1 for sewage sludge-derived biochar. The content of bioavailable PAHs derivatives was, generally, one order of magnitude lower than parent PAHs derivatives, and reached from below LOD up to almost 1 ng L-1 for plant-derived biochar, from 0.5 to 2 ng L-1 for biochar obtained from residues from biogas production, and from 0.2 to almost 5 ng L-1 for sewage sludge-derived biochar confirming the safety of agricultural usage of biochar.

Nitrogen Fertilization and Solvents as Factors Modifying the Antioxidant and Anticancer Potential of Arnica montana L. Flower Head Extracts.

Arnica montana L. is one of Europe's endemic endangered medicinal plants, with diverse biological activities commonly used in medicine, pharmacy, and cosmetics. Its flower heads are a rich source of raw material, with antibacterial, antifungal, antiseptic, anti-inflammatory, antiradical, antioxidant, and antitumor properties. The objective of the present study was (i) to characterize the chemical composition of flower heads of A. montana plants cultivated under nitrogen fertilization, (ii) to identify the impact of the nitrogen fertilization and extraction method (water, ethanol) on the antioxidant activity of extracts, and (iii) to determine the role of different nitrogen doses applied during plant cultivation and different extraction methods in the anticancer activity of the extracts through analysis of apoptosis and autophagy induction in HT29, HeLa, and SW620 cell lines. The present study shows that nitrogen is a crucial determinant of the chemical composition of arnica flower heads and the antioxidant and anticancer activity of the analyzed extracts. Nitrogen fertilization can modify the composition of pharmacologically active substances (sesquiterpene lactones, flavonoids, essential oil) in Arnicae flos. The content of sesquiterpene lactones, flavonoids, and essential oil increased with the increase in the nitrogen doses to 60 kg N ha-1 by 0.66%, 1.45%, and 0.27%, respectively. A further increase in the nitrogen dose resulted in a decrease in the content of the analyzed secondary metabolites. Varied levels of nitrogen application can be regarded as a relevant way to modify the chemical composition of arnica flower heads and to increase the anticancer activity, which was confirmed by the increase in the level of apoptosis with the increase in fertilization to a level of 60 kg N ha-1. The fertilization of arnica plants with low doses of nitrogen (30 and 60 kg N ha-1) significantly increased the LOX inhibition ability of the ethanol extracts. The present study is the first report on the anticancer activity of A. montana water extracts, with emphasis on the role of water as a solvent. In further studies of factors modifying the quality of Arnicae flos, attention should be paid to the simultaneous use of nitrogen and other microelements to achieve synergistic results and to the possibility of a more frequent use of water as a solvent in studies on the biological activity of A. montana extracts.

Sewage sludge and solid residues from biogas production derived biochar as an effective bio-waste adsorbent of fulvic acids from water or wastewater.

Due to environmental concern, direct utilization of sewage sludge or residues from biogas production is restricted. Conversion of problematic bio-wastes into biochars can be a very effective solution. In the presented study, the adsorption of fulvic acids onto series of biochars produced from bio-wastes such as sewage sludge, residues from biogas production, and plant (Miscanthus sp.) were performed to examine the behavior of biochars in the environment and interactions with fulvic acids as the representatives of dissolved organic matter. The results clearly indicate that the highest excess of fulvic acids, 93-96 mg g-1, was chemisorbed onto biochar obtained specifically from sewage sludge. The mechanism of the adsorption was independent from applied biochar feedstock. Monolayer coverage was dominant onto all biochars. Generally, adsorption was assumed to be controlled by polar interactions between fulvic acids and the biochars or pre-adsorbed and residual fulvic acids molecules (which were dominant) and the strong π-π interactions. The obtained high values of the adsorption capacity of sewage sludge derived biochars confirmed that thermal treatment is a very effective tool of bio-waste management.

Sustainable synthesis of rose flower-like magnetic biochar from tea waste for environmental applications.

Introduction: Biochar utilization for adsorption seems to be the most cost-effective, easy/fast approach for pollutants removal from water and wastewater. Due to the high adsorption properties, magnetic biochar proved to be efficient in the sorption of heavy metals and nutrients. Although there are several studies on development of magnetic biochars, there is a lack of research on development of high-performance magnetic biochar from food waste for removal applications. Objectives: This study aimed at preparing new classes of magnetic biochar derived from tea waste (TBC) for removal of heavy metals (Ni2+, Co2+), and nutrients (NH4+ and PO43-) from water and effective fertilizer (source of NH4+ and PO43-). Methods: Standard carbonization process and ultrafast microwave have been used for fabrication of TBCs. The removal of nickel, cobalt as the representatives of heavy metals, and over-enriched nutrients (NH4+ and PO43-) from water were tested and the removal kinetics, mechanism, and the effect of pH, dissolved organic matter and ionic strength were studied. Simultaneously, possible fertilizing effect of TBC for controlled release of nutrients (NH4+ and PO43-) in soil was investigated. Results: Up to 147.84 mg g-1 of Ni2+ and 160.00 mg g-1 of Co2+ were adsorbed onto tested biochars. The process of co-adsorption was also efficient (at least 131.68 mg g-1 of Co2+ and 160.00 mg g-1 of Ni2+). The highest adsorbed amount of NH4+ was 49.43 mg g-1, and the highest amount of PO43- was 112.61 mg g-1. The increase of the solution ionic strength and the presence of natural organic matter affected both the amount of adsorbed Ni2++Co2+ and the reaction mechanism. Conclusions: The results revealed that magnetic nanoparticle impregnated onto tea biochar, can be a very promising alternative for wastewater treatment especially considering removal of heavy metals and nutrients and slow-release fertilizer to improve the composition of soil elements.

Co-pyrolysis of sewage sludge and biomass in carbon dioxide as a carrier gas affects the total and leachable metals in biochars.

The total and available (water extracted) content of selected metal were determined in co-pyrolyzed SSL with willow (8:2, 6:2 w/w) at 500, 600, and 700 °C using two different carrier gases (N2 or CO2). The study investigated the relationship of metal content and bioavailability to toxicity of biochars towards bacteria (Vibrio fischeri), plants (Lepidium sativum), and arthropods (Folsomia candida). For the biochar produced at a ratio of 6:4 (SSL:willow), the content of most metals significant decrease (P ≤ 0.05) from 5.9% to 28.9%. Co-pyrolysis of SSL with willow decreased water extractable metal concentrations (Ba, Cd, Cu, Fe, Mn, Ni, and Zn) from 8.0% to 100%. The CO2 resulted from 6 to 200 % increase (P ≤ 0.05) of metal content relative to the biochar pyrolyzed in N2. An increase in pyrolysis temperature caused a higher concentration of the metals in the biochars. The available content of most metals decreased from 9 to 100 %. The adverse effect of these biochars on living organisms was reduced due to a stronger binding of the metals (especially Cu and Cd) with the biochar matrix. The negative impact of Cd, Cr, and Cu on living organisms was also confirmed by principal component analysis (PCA).

Carbon dioxide as a carrier gas and mixed feedstock pyrolysis decreased toxicity of sewage sludge biochar.

The common use of sewage sludge (SSL)-derived biochar can be limited due to contaminants present in SSL, which may affect SSL-derived biochar toxicity. We propose the reduction of SSL-derived biochar toxicity by it co-pyrolysis with biomass and in CO2 atmosphere. Ecotoxicity of biochars produced at 500, 600, and 700 °C from SSL and SSL with the addition of willow (at a ratio of SSL:willow - 8:2 and 6:4, w/w) in an atmosphere of N2 or CO2 were investigated. The toxicity of aqueous extracts derived from the biochars (Lepidium sativum - Elongation test, Vibrio fischeri - Microtox) or solid-phase toxicity (Lepidium sativum - Phytotoxkit F, Folsomia candida - Collembolan test) was also studied. SSL-derived biochar produced at N2 atmosphere usually was toxic for all tested organisms. Co-pyrolysis of mixed feedstock reduced the toxicity of the produced biochar. In the case of biochars produced from SSL and willow under N2 atmosphere decrease in inhibition of F. candida reproduction (from 27 to 58%) or its stimulation (from 7 to 30%) in comparison to SSL alone derived biochar, was observed. Co-pyrolysis of SSL with willow significantly reduced the toxicity of extracts the SSL-derived biochar towards L. sativum. The aqueous extracts obtained from the biochars produced at temperatures of 500 and 600 °C with willow addition were also less toxic to V. fischeri than the biochars produced from SSL alone. The change of carrier gas from N2 to CO2, regardless of the feedstock used, in most cases reduced toxicity or positively affected the test organisms. This was probably caused by changes in the physicochemical properties and content of contaminants in the biochars produced in an atmosphere of CO2, compared to N2. An exception was root growth inhibition in the solid phase tests where no significant differences were found between biochars produced in N2 and CO2.

Impact of ZnO and ZnS nanoparticles in sewage sludge-amended soil on bacteria, plant and invertebrates.

The effect of zinc oxide nanoparticles (ZnO NPs) and zinc sulfide nanoparticles (ZnS NPs) on the toxicity of sewage sludges in sewage sludge-amended soils was investigated with respect to plant- (Lepidium sativum) and soil- (Folsomia candida) species. The toxicity of porewater obtained from the tested soils towards Vibrio fischeri (Microtox®) was also investigated. Two sewage sludges (SSL1 and SSL2) with different organic matter content were amended with nanoparticles. Depending on the type of biotest and the type of sewage sludge, different effects of ZnO or ZnS NPs on the toxicity of sewage sludge-amended soil were observed. In general, ZnO and ZnS NPs stimulated root growth for SSL1 or reduced the harmful impact of SSL2 on the root growth of L. sativum roots. Greater stimulation or inhibition of root growth was observed for the ZnO than ZnS NPs. The unfavorable effect of ZnO/ZnS NPs on F. candida mortality and reproduction was observed at a concentration of ZnO/ZnS in sewage sludge ≥250 mg/kg. Generally, there were no significant differences between ZnO and ZnS NPs toxicity towards F. candida. Aging for 45 days of sewage sludge-amended soil containing NPs affected ZnO and ZnS NPs toxicity to all tested organisms. In the most cases, the toxicity decreased after 45 days of aging for plant (L. sativum) and invertebrates (F. candida). The toxicity of porewater to V. fischeri from sewage sludge-amended soil contains ZnO NPs did not change, while in the case of ZnS NPs, the toxicity increased after 45 days of aging.

Carbon dioxide as a carrier gas and biomass addition decrease the total and bioavailable polycyclic aromatic hydrocarbons in biochar produced from sewage sludge.

Organic-solvent extractable (Ctot) and freely dissolved (Cfree) polycyclic aromatic hydrocarbons (PAHs) (US EPA 16 PAHs) were determined in biochars produced from the mixture of sewage sludge and sewage sludge and willow (8:2 or 6:4, w/w). The pyrolysis was carried out at 500, 600, and 700 °C using two different carrier gases (N2 or CO2). Addition of willow and the change of carrier gas from N2 to CO2 reduced Ctot PAHs (from 7.0 to 52%) and Cfree PAHs (15-29%) content. Co-application of willow and SSL and the use of CO2 as a carrier gas also beneficially affected the PAHs profile. The biochars produced with willow addition and/or in a CO2 atmosphere were characterized by a lower (from 9.0 to 62.8%) percentage of 3-6-ring PAHs (Ctot) than the biochars derived from sewage sludge alone in N2 atmosphere. The contribution of individual Cfree PAHs did not differ significantly between biochars. The presence of willow during pyrolysis influenced the direction of the changes in the Ctot PAH content depending on the pyrolysis temperature. For SSL alone, regardless of the carrier gas used, the content of Ctot PAHs was observed to decrease with increasing temperature, whereas in the presence of willow temperature did not affect significantly (P ≥ 0.05) the Ctot PAHs content. The change of carrier gas from N2 to CO2 increased the affinity of the biochars to PAHs as confirmed by the distribution coefficients log KTOC.

Adsorption capacity of phenanthrene and pyrene to engineered carbon-based adsorbents produced from sewage sludge or sewage sludge-biomass mixture in various gaseous conditions.

Adsorption of phenanthrene (PHE) and pyrene (PYR) by engineered carbon-based adsorbents produced from sewage sludge in an atmosphere of nitrogen (N2) or carbon dioxide (CO2) at temperatures of 500, 600, and 700 °C was investigated. The addition of willow to the SSL decreased the biochar adsorption capacity. However, there was an increase in the adsorption capacity after changing N2 to CO2. The addition of willow to SSL and the type of carrier gas affected the mechanism of adsorption. The adsorption of PHE and PYR on the SSL-derived adsorbents produced in N2 occurred through pore filling. The adsorption on the SSL-derived adsorbents with willow followed the mechanism of π-π electron-donor-acceptor (EDA) interactions and hydrophobic interactions. A similar mechanism was observed with regard to the biochars produced from SSL in atmosphere of CO2. For the SSL-derived adsorbents with willow in CO2, the adsorption mechanism was observed to vary between PHE and PYR.

Application of biochar to sewage sludge reduces toxicity and improve organisms growth in sewage sludge-amended soil in long term field experiment.

The aim of the present study was to determine changes in the physicochemical properties and toxicity of soil amended with sewage sludge (10tdw/ha) or sewage sludge (10tdw/ha) with biochar addition (2.5, 5 or 10% of sewage sludge). The study was carried out as a field experiment over a period of 18months. Samples for analysis were taken at the beginning of the experiment as well as after 6, 12 and 18months. The study investigated toxicity of the unamended soil, sewage sludge-amended soil and sewage sludge-amended soil with biochar addition towards Folsomia candida (collembolan test) and Lepidium sativum (Phytotoxkit F). Moreover, toxicity of aqueous extracts obtained from the tested soils towards Vibrio fischeri (Microtox®) and Lepidium sativum (elongation test) was determined. The study showed that addition of biochar to the sewage sludge and soil reduced leaching of nutrients (mainly phosphorus and potassium) from the amended soil. Biochar significantly reduced sewage sludge toxicity, exhibiting a stimulating effect on the tested organisms. The stimulating effect of biochar addition to the sewage sludge persisted throughout the entire experiment. Apart from the remediatory character of biochar, this is also evidence of its fertilizing character. In the tests with L. sativum (leachates and solid phase) and V. fischeri (leachates), increasing the rate of biochar in the sewage sludge increased root growth stimulation (L. sativum) and bacteria luminescence (V. fischeri). However, increasing biochar rate decreased F. candida reproduction stimulation, which could have been an effect of reduced nutrient bioavailability due to the biochar.