Degradation kinetics of biochar from pyrolysis and hydrothermal carbonization in temperate soils

Background and Aims

Estimates of biochar residence times in soils range over three orders of magnitude. We present the first direct comparison between the biodegradation of a char from hydrothermal carbonization (htcBC) and pyrolysis (pyrBC) with high temporal resolution.

Methods

Mineralization of the biochars and their shared Miscanthus feedstock in three soils was determined directly by the ¹³CO₂ efflux using a novel method incorporating wavelength scanned cavity ring-down spectroscopy. Biochar half-life (t_1/2) was estimated with three empirical models.

Results

(1) The htcBC was readily biodegradable, whereas pyrBC was more recalcitrant. (2) Cumulative degradation of both biochars increased with soil organic carbon and nitrogen content. (3) The corrected Akaike information criterion (AIC_C) showed an overall preference for the double exponential model (DEM) reflecting a labile and a recalcitrant C-pool, over the first-order degradation model (FODM) and a logarithmic model. (4) The DEM resulted in t_1/2 ranging from 19.7–44.5, 0.7–2.1 and 0.8–1.3 years for pyrBC, htcBC and feedstock, respectively.

Conclusion

The degradation was rather similar between feedstock and htcBC but one order of magnitude slower for pyrBC. The AIC_C preferred FODM in two cases, where the DEM parameters indicated no distinction between a labile and recalcitrant carbon pool.     

Gadopentatic acid affects in vitro proliferation and doxorubicin response in human breast adenocarcinoma cells

Contrasting agents (CAs) that are administered to patients during magnetic resonance imaging to facilitate tumor identification are generally considered harmless. However, gadolinium (Gd) based contrast agents can be retained in the body, inflicting specific cell line cytotoxicity. We investigate the effect of Gadopentatic acid (Gd-DTPA) on human breast adenocarcinoma MCF-7 cells. These cells exhibit a toggle switch response: exposure to 0.1 and 1 mM concentrations of Gd-DTPA enhances proliferation, which is hindered at a higher 10 mM concentration. Proliferation is enhanced when cells transition to 3D morphologies in post confluent conditions. The proliferation dependence on the concentration of CA is absent for Hs 578T and MDA-MB-231 triple negative cell lines. MCF-7 cells reveal a double toggle switch related to the expression of VEGF, which goes through high–low–high downregulation when cells are exposed to 0.1, 1, and 10 mM Gd-DTPA, respectively. Finally, doxorubicin drug response is assessed, which also reveals a double toggle switch behavior, where drug cytotoxicity exhibits a nonlinear dependence on the CA concentration. A toggle switch in cell characteristics that are exposed to 1 mM of Gd-DTPA amplifies the importance of this threshold, affecting several cell behaviors if surpassed. This work emphasizes the important effects that CAs can have on cells, specifically Gd-DTPA on MCF-7 cells, and the implications for cell growth and drug response during clinical and synthetic biology procedures.     

Scale-associated glycoproteins of Scherffelia dubia (Chlorophyta) form high-molecular-weight complexes between the scale layers and the flagellar membrane

Flagellar scales were isolated from the flagellate green alga Scherffelia dubia. The flagellar scales consist mainly of acidic polysaccharides (70%) and glycoproteins (10%), and monosaccharide analyses show that the scales contain high amounts of unusual 2-keto-sugar acids. Approximately, 72 mol% of total carbohydrate is 3-deoxy-manno-2-octulosonic acid, 3-deoxy-5-O-methylmanno-2-octulosonic acid and 3-deoxy-lyxo-2-heptulosaric acid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the presence of at least 18 different scale-associated proteins (SAPs), ranging in apparent molecular mass from 77 kDa to over 300 kDa. Lectin blot analyses performed in combination with glycosidase treatment, showed that SAPs contained N-glycans of the highmannose type and the hybrid type, as well as a complex type that was not immunologically related to higher-plant complex glycans. Most of the SAPs were present in two or possibly three high-molecular-weight complexes. In these complexes, individual polypeptides are cross-linked by disulfide bridges. A polyclonal antibody was raised against a SAP of 126 kDa (SAP 126), a glycoprotein present in a high-molecular-weight complex. The SAP126 antibody was used to localize the protein between scale layer and flagellar membrane. We suggest that these high-molecular-weight complexes link scales to the flagellar membrane.Abbreviations AAA Aleuria aurantia agglutinin - DSA Datura stramonium agglutinin - DTT dithiothreitol - GNA Galanthus nivalis agglutinin - RCA Ricinus communis agglutinin - SAP Scale-associated protein - TBS Tris-buffered saline Dedicated to Professor Eberhard Schnepf on the occasion of his 65th birthday.This work was supported by the Deutsche Forschungsgemeinschaft and an Alexander von Humboldt Foundation research award to L. Perasso. We thank G. Noat for providing the anti--glucosidase and anti-pectin methyl esterase antibodies.     

Can differences in microbial abundances help explain enhanced N2O emissions in a permanent grassland under elevated atmospheric CO2?

Long‐term effects of elevated atmospheric CO₂ on the ammonia‐oxidizing and denitrifying bacteria in a grassland soil were investigated to test whether a shift in abundance of these N‐cycling microorganisms was responsible for enhanced N₂O emissions under elevated atmospheric CO₂. Soil samples (7.5 cm increments to 45 cm depth) were collected in 2008 from the University of Giessen Free Air Carbon dioxide Enrichment (GiFACE), a permanent grassland exposed to moderately elevated atmospheric CO₂ (+20%) since 1998. GiFACE plots lay on a soil moisture gradient because of gradually changing depth to the underlying water table and labeled as the DRY block (furthest from water table), MED block (intermediate to water table), and WET block (nearest to water table). Mean N₂O emissions measured since 1998 have been significantly higher under elevated CO₂. This study sought to identify microbial and biochemical parameters that might explain higher N₂O emissions under elevated CO₂. Soil biochemical parameters [extractable organic carbon (EOC), dissolved organic nitrogen (DON), NH₄⁺, NO₃^?], and abundances of genes encoding the key enzymes involved in ammonia oxidation (amoA) and denitrification (nirK, nirS, nosZ) depended more on soil depth and block (underlying soil moisture gradient) than on elevated CO₂. Ammonia oxidation and denitrification gene abundances, relative abundances (ratios) of nirS to nirK, of nosZ to both nirS and to nirK, and of the measured soil biochemical properties DON and NO₃^? tended to be lower in elevated CO₂ plots as compared with ambient plots in the MED and WET blocks while the DRY block exhibited an opposite trend. High N₂O emissions under elevated CO₂ in the MED and WET blocks correlated with lower nosZ to nirK ratios, suggesting that increased N₂O emissions under elevated CO₂ might be caused by a higher proportion of N₂O‐producing rather than N₂O consuming (N₂ producing) denitrifiers.     

Response of aboveground grassland biomass and soil moisture to moderate long-term CO2 enrichment

Rising atmospheric CO₂ concentrations may alter C cycling and community composition, however, long-term studies in (semi-)natural ecosystems are still rare. In May 1998, the Giessen FACE (Free Air Carbon dioxide Enrichment) experiment started in a grassland ecosystem near Giessen, Germany, consisting of three enrichment (E plots) and three ambient control rings (A plots). Carbon dioxide concentrations were raised to +20% above ambient all-year-round during daylight hours. The wet grassland (Arrhenatheretum elatioris Br.-Bl.; not ploughed for >100 years) has been fertilized with 40 kg ha⁻¹ yr⁻¹ N, and mown two times each year for decades. Since 1993, the biomass has been monitored and since 1997 it was divided into grasses, legumes and non-leguminous forbs.During the 5 years prior to CO₂ enrichment, the annual biomass yield from the A plots was non-significantly higher (3%) than the later E plots yield. Under CO₂ enrichment, the biomass increased significantly from the third enrichment year on by 9.8%, 7.7% and 11.2% in the years 2000–2002, respectively. The increase was surprisingly high considering the moderate CO₂ enrichment regime of only +20% and sub-optimal N supply, possibly suggesting a non-linear response of temperate grassland ecosystems to rising atmospheric CO₂ levels.The leaf area index did not change significantly under elevated CO₂, nor did the soil moisture in the top 15 cm increase. No correlation existed between the magnitude of the yield stimulation under elevated CO₂ and the precipitation sums preceding the respective harvests. The grass biomass increased significantly under FACE, while the forb biomass declined strongly in the fourth and fifth year. The legume fraction was mostly below 1% of the total yield, and did not respond to CO₂ enrichment. These findings are in contrast to other grassland results and possible reasons are discussed.     

Identification of the initiation sequence for viral-strand DNA synthesis of wheat dwarf virus.

The intergenic region of the circular single-stranded DNA genome of geminiviruses contains a sequence potentially able to fold into a stem-loop structure. This sequence has been reported to be involved in viral replication by serving as the origin for rolling-circle replication. However, in wheat dwarf virus (WDV) a deletion of 128 bp, removing this sequence, surprisingly does not prevent de novo viral DNA synthesis, but instead abrogates the processing of replicative intermediates into monomeric genomes. This deletion mutant permitted us to study the initiation of viral-strand DNA synthesis independently from its termination and also to identify the sequence within which rolling-circle DNA replication of WDV begins. We have mapped the initiation site of replication to a pentanucleotide, TACCC, a sequence that occurs twice in the large intergenic region of WDV: it is found in the right half of the stem-loop sequence and again 170 bases upstream where it is part of a 15 nucleotide sequence highly homologous to the right half of the stem-loop sequence. Here we show that viral-strand DNA synthesis efficiently initiates at both sequences.     

Geminivirus-based shuttle vectors capable of replication in Escherichia coli and monocotyledonous plant cells

Shuttle vectors have been constructed that are able to replicate in either Escherichia coli or plant cells. They contain the ColE1 origin of replication and parts of the wheat dwarf virus genome, a geminivirus infecting a variety of species of monocotyledonous plants. Such plasmids are able to replicate in E. coli and wheat cells. The plasmids can be rescued in E. coli and show no changes during their passage through plant cells. Such an E. coli/plant cell shuttle vector system could be used for the amplification of foreign genes in plant cells, for studies on DNA rearrangement or the isolation of plant transposons.     

Biomass responses in a temperate European grassland through 17 years of elevated CO2

Future increase in atmospheric CO₂ concentrations will potentially enhance grassland biomass production and shift the functional group composition with consequences for ecosystem functioning. In the “GiFACE” experiment (Giessen Free Air Carbon dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO₂ (eCO₂) year‐round during daylight hours since 1998, at a level of +20% relative to ambient concentrations (in 1998, aCO₂ was 364 ppm and eCO₂ 399 ppm; in 2014, aCO₂ was 397 ppm and eCO₂ 518 ppm). Harvests were conducted twice annually through 23 years including 17 years with eCO₂ (1998 to 2014). Biomass consisted of C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass (TAB) was significantly increased under eCO₂ (p = .045 and .025, at first and second harvest). The dominant plant functional group grasses responded positively at the start, but for forbs, the effect of eCO₂ started out as a negative response. The increase in TAB in response to eCO₂ was approximately 15% during the period from 2006 to 2014, suggesting that there was no attenuation of eCO₂ effects over time, tentatively a consequence of the fertilization management. Biomass and soil moisture responses were closely linked. The soil moisture surplus (c. 3%) in eCO₂ manifested in the latter years was associated with a positive biomass response of both functional groups. The direction of the biomass response of the functional group forbs changed over the experimental duration, intensified by extreme weather conditions, pointing to the need of long‐term field studies for obtaining reliable responses of perennial ecosystems to eCO₂ and as a basis for model development.     

Annual cycles of apoptosis,DNA strand breaks,heat shock proteins,and metallothionen isoforms in dab (Limanda limanda): influences of natural factors and consequences for biological effect monitoring

The present study was undertaken to investigate the influence of natural and anthropogenic stressors on the induction of apoptosis, metallothionein (MT) isoforms, heat shock proteins and DNA strand breaks in the marine flatfish dab (Limbanda limanda) Seasonal changes and possible physiological influences were evaluated over a 1-year period at a fixed location northwest of Helgoland in the German Bight. These results were compared with data from sampling sites in the North Sea and the Baltic Sea. Annual cycles could be observed for all parameters except for Cd. The data revealed that changes in biomarker are not only linked to physiological processes related to reproduction but also to factors like water temperature changes, lipid content and zinc content. Cd and organochlorines had no influence on biomarkers whereas an influence of Cd on MT levels revealed in the regional observations was possibly masked by the major changes in Zn content during the annual cycle. Due to different abiotic factors we supposed that the annual cycles at each sampling site in the North and the Baltic Sea might be shifted temporally and therefore measurements at different locations during a small time window of a few weeks may lead to misinterpretation in biomarker research.