A comparative study of the properties of industrially produced humic substances

Humic substances (HSs) are produced industrially in large quantities from low rank coal, weathered coal, peat, also from soils, composts and other sources. Considering that the applications of industrially produced HSs also include food, pharmaceutical applications and environmental technologies, it is important to evaluate their composition and quality and to identify their sources. The aim of the present study is to compare the properties of industrially produced HS samples. HSs were characterised using spectroscopic and other methods. For the identification of origin of HSs, different methods can be used, such as elemental analysis and ratios of light stable isotopes. The results of the study indicate that many industrially produced HSs are of poor quality (low concentration of basic substance, admixture of undesirable substances, pollutants, no quality indications). In this situation, rigorous quality control should be implemented, providing detailed characteristics of the product. The composition of materials suggested for agricultural applications has not been analysed much. Most of the studied materials were designated as HAs, followed by fulvic acids (FAs) and HSs. However, an analysis of the humic matter types indicates that the majority of substances offered on the market are in fact mixtures of HAs and FAs; so, it would be more appropriate to designate them as HSs or their salts. This study identifies the main quality problems of industrially produced humic substances: 1) lack of strict quality indicators, 2) absence of indication of source materials/origins of HSs

What happens to peat during bog fires? Thermal transformation processes of peat organic matter

Bog fires are a serious natural phenomena. Major increase in the number of fires has happened during the last decades due to bog transformation into agricultural lands, accidents and human activities. During bog fires the peat is exposed to high temperatures due to which chemical transformation and even mineralisation of peat can occur. The aim of the study was to analyse the impacts of the bog fires on the bog as an ecosystem, advance the understanding and knowledge of fire impact on peat and humic matter properties and application possibilities. As the material for the study peat samples from burnt sites and thermally treated peat were used. To reveal peat transformation during bog fires, thermogravimetric analysis of peat samples were done, where amounts of bitumens, humic acids and mineral matter were estimated. During bog fires thermal modification of peat properties takes place, resulting in full mineralisation of peat and release of mineral substances. Bog fires lead to development of peat char, bitumens and significant changes in structure and properties of peat humic acids. However, from perspective of application of peat as a substrate and from perspective of impacts on the bog ecosystems, the effects are negligible

Measurement of the Total Active 8B Solar Neutrino Flux at the Sudbury Neutrino Observatory with Enhanced Neutral Current Sensitivity

The Sudbury Neutrino Observatory (SNO) has precisely determined the total active (nu_x) 8B solar neutrino flux without assumptions about the energy dependence of the nu_e survival probability. The measurements were made with dissolved NaCl in the heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 +/- 0.27 (stat) +/- 0.38 (syst) x10^6 cm^{-2}s^{-1}, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Delta m^{2} = 7.1^{+1.2}_{-0.6}x10^{-5} ev^2 and theta = 32.5^{+2.4}_{-2.3} degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations.Comment: Submitted to Phys. Rev. Let

Electron Antineutrino Search at the Sudbury Neutrino Observatory

Upper limits on the \nuebar flux at the Sudbury Neutrino Observatory have been set based on the \nuebar charged-current reaction on deuterium. The reaction produces a positron and two neutrons in coincidence. This distinctive signature allows a search with very low background for \nuebar's from the Sun and other potential sources. Both differential and integral limits on the \nuebar flux have been placed in the energy range from 4 -- 14.8 MeV. For an energy-independent \nu_e --> \nuebar conversion mechanism, the integral limit on the flux of solar \nuebar's in the energy range from 4 -- 14.8 MeV is found to be \Phi_\nuebar <= 3.4 x 10^4 cm^{-2} s^{-1} (90% C.L.), which corresponds to 0.81% of the standard solar model 8B \nu_e flux of 5.05 x 10^6 cm^{-2} s^{-1}, and is consistent with the more sensitive limit from KamLAND in the 8.3 -- 14.8 MeV range of 3.7 x 10^2 cm^{-2} s^{-1} (90% C.L.). In the energy range from 4 -- 8 MeV, a search for \nuebar's is conducted using coincidences in which only the two neutrons are detected. Assuming a \nuebar spectrum for the neutron induced fission of naturally occurring elements, a flux limit of Phi_\nuebar <= 2.0 x 10^6 cm^{-2} s^{-1}(90% C.L.) is obtained.Comment: submitted to Phys. Rev.

Constraints on Nucleon Decay via "Invisible" Modes from the Sudbury Neutrino Observatory

Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to ``invisible'' modes, such as n -> 3 nu. The analysis was based on a search for gamma-rays from the de-excitation of the residual nucleus that would result from the disappearance of either a proton or neutron from O16. A limit of tau_inv > 2 x 10^{29} years is obtained at 90% confidence for either neutron or proton decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton decay modes and 400 times more stringent than similar neutron modes.Comment: Update includes missing efficiency factor (limits change by factor of 2) Submitted to Physical Review Letter

2‐Methyltetrahydrofuran (2‐MeTHF) as a versatile green solvent for the synthesis of amphiphilic copolymers via ROP, FRP, and RAFT tandem polymerizations

2‐methyltetrahydrofuran (2‐MeTHF) is a readily available, inexpensive, neoteric, bio‐based solvent. It has been adopted across a wide range of chemical processes including the batch manufacture of fine chemicals, enzymatic polycondensations and ring opening polymerizations. To reduce the environmental burden related to the synthesis of pharmaceutical‐grade polymers based on lactide and caprolactone, we envisaged the use of 2‐MeTHF. For the first time, we combined a series of metal‐free and enzymatic ROPs with free radical and controlled RAFT polymerizations (carried out separately and in tandem) in 2‐MeTHF, in order to easily tune the chemistry and the architecture of the final polymers. After a simple purification, the amphiphilic polymers were formulated into nanoparticles and tested for their cytocompatibility in three model cell lines, to assess their application as potential polymeric excipients for nanomedicines

Fire and herbivory drive fungal and bacterial communities through distinct above- and belowground mechanisms

Fire and herbivory are important natural disturbances in grassy biomes. Both drivers are likely to influence belowground microbial communities but no studies have unravelled the long-term impact of both fire and herbivory on bacterial and fungal communities. We hypothesized that soil bacterial communities change through disturbance-induced shifts in soil properties (e.g. pH, nutrients) while soil fungal communities change through vegetation modification (biomass and species composition). To test these ideas, we characterised soil physico-chemical properties (pH, acidity, C, N, P and exchangeable cations content, texture, bulk density, moisture), plant species richness and biomass, microbial biomass and bacterial and fungal community composition and diversity (using 16S and ITS rRNA amplicon sequencing, respectively) in six long-term (18 to 70 years) ecological research sites in South African savanna and grassland ecosystems. We found that fire and herbivory regimes profoundly modified soil physico-chemical properties, plant species richness and standing biomass. In all sites, an increase in woody biomass (ranging from 12 to 50%) was observed when natural disturbances were excluded. The intensity and direction of changes in soil properties were highly dependent on the topo-pedo-climatic context. Overall, fire and herbivory shaped bacterial and fungal communities through distinct driving forces: edaphic properties (including Mg, pH, Ca) for bacteria, and vegetation (herbaceous biomass and woody cover) for fungi. Fire and herbivory explained on average 7.5 and 9.8% of the fungal community variability, respectively, compared to 6.0 and 5.6% for bacteria. The relatively small changes in microbial communities due to natural disturbance is in stark contrast to dramatic vegetation and edaphic changes and suggests that soil microbial communities, having evolved with disturbance, are resistant to change. This represents both a buffer to short-term anthropogenic-induced changes and a restoration challenge in the face of long-term changes

Fire and herbivory drive fungal and bacterial communities through distinct above- and belowground mechanisms

Fire and herbivory are important natural disturbances in grassy biomes. Both drivers are likely to influence belowgroundmicrobial communities but no studies have unravelled the long-term impact of both fire and herbivory on bacterial and fungal communities. We hypothesized that soil bacterial communities change through disturbance-induced shifts in soil properties (e.g. pH, nutrients) while soil fungal communities change through vegetation modification (biomass and species composition). To test these ideas, we characterised soil physicochemical properties (pH, acidity, C, N, P and exchangeable cations content, texture, bulk density, moisture), plant species richness and biomass,microbial biomass and bacterial and fungal community composition and diversity (using 16S and ITS rRNA amplicon sequencing, respectively) in six long-term (18 to 70 years) ecological research sites in South African savanna and grassland ecosystems.We found that fire and herbivory regimes profoundly modified soil physico-chemical properties, plant species richness and standing biomass. In all sites, an increase in woody biomass (ranging from 12 to 50%) was observed when natural disturbances were excluded. The intensity and direction of changes in soil properties were highly dependent on the topo-pedo-climatic context. Overall, fire and herbivory shaped bacterial and fungal communities through distinct driving forces: edaphic properties (including Mg, pH, Ca) for bacteria, and vegetation (herbaceous biomass and woody cover) for fungi. Fire and herbivory explained on average 7.5 and 9.8% of the fungal community variability, respectively, compared to 6.0 and 5.6% for bacteria. The relatively small changes inmicrobial communities due to natural disturbance is in stark contrast to dramatic vegetation and edaphic changes and suggests that soilmicrobial communities, having evolved with disturbance, are resistant to change. This represents both a buffer to short-term anthropogenicinduced changes and a restoration challenge in the face of long-term changes.The National Research Foundation, South Africa and the Patterson Foundation via Conservation International, South Africa.http://www.elsevier.com/locate/scitotenvam2022BiochemistryGeneticsMicrobiology and Plant Patholog

A ‘greener’ one-pot synthesis of monoterpene-functionalised lactide oligomers

© 2020 Elsevier Ltd In this work we aimed to achieve a totally sustainable Ring Opening Polymerisation (ROP) process, by harmonising the use of naturally occurring or derivable initiators and the green solvent 2-Methyltetrahydrofuran (2-MeTHF). First, a library of novel monoterpene-alcohols and existing terpenoids was used to provide renewably sourced initiators for a metal-free ROP synthetic step. A number of these initiators are derived from waste materials, further improving their sustainability. Secondly, we selected lactide (LA) as a monomer, because not only is it derived from biomass, but its resultant polymers are biocompatible and biodegradable. Interestingly, these new polymers self-assembled in water producing well defined, biocompatible nanoparticles (NPs) via direct nanoprecipitation without the use of additional stabilisers. We have highlighted a novel and promising (ROP) approach to produce biodegradable, amphiphilic ester-based macromolecules, based on lactide and terpenes (as initiators) in a green solvent, 2-MeTHF thus reducing solvent toxicity in an efficient, simple and sustainable new synthesis. The monoterpenes may provide a highly functionalisable and bio-renewable toolbox for a new generation of ROP initiators

Positronium laser cooling via the 13S1^3S-23P2^3P transition with a broadband laser pulse

We report on laser cooling of a large fraction of positronium (Ps) in free-flight by strongly saturating the $1^3S$-$2^3P$ transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived $3^3P$ states. The second effect is the one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) K to 170(20) K. We demonstrate a 58(9) % increase in the coldest fraction of the Ps ensemble.Comment: 6 pages, 5 figure