Dioxins and furans in biochars,hydrochars and torreficates produced by thermochemical conversion of biomass: a review

Converting raw biomass into valuable products protects the environment, improves economics, and helps tackle climate change by cutting resource demand and waste production. Thermochemical treatment is a common method for producing biochars, hydrochars and torreficates from biomass and organic wastes, which can also generate dioxins and furans and consequently limit the use of thermochemically converted chars. Here we review the presence of dioxins and furans in chars produced by hydrothermal carbonization, torrefaction, and pyrolysis processes under the influence of temperature, residence time, heating rate, pressure, and feedstock type. Dioxins and furans were mostly below 20 ng total toxic equivalence per kilogram (TEQ kg⁻¹), with the highest level of 113 ng TEQ kg⁻¹ found in over 100 samples of different char types. The most toxic products were hydrochars produced from sewage sludge. Processing temperature and feedstock type were key factors resulting in high dioxin levels in chars, and care should be taken when producing chars at temperatures up to 300 °C or using feedstocks previously contaminated with dioxins or preservatives.

     

Predicting applicants' job pursuit behavior from their selection expectations: the mediating role of the theory of planned behavior

Applicants' pretest expectations about the forthcoming selection procedure may serve as a key factor in applicants' decision‐making. The current study examined the validity of the theory of planned behavior (TPB) as an explanatory mechanism of the relationship between pretest selection expectations (warmth/respect, chance to demonstrate potential, difficulty of faking, unbiased assessment, feedback) and job pursuit behavior. Data were collected at two points in time, using a sample of applicants for the military. Selection expectations, job pursuit attitude, subjective norm, and controllability were significantly related to job pursuit intention. Job pursuit attitude mediated the relationship between selection expectations and job pursuit intention. Subjective norm and time lag were the only significant predictors of job pursuit behavior. Practical implications, strengths and limitations, as well as directions for further research are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

The variations of aluminium species in mountainous forest soils and its implications to soil acidification

Aluminium (Al) speciation is a characteristic that can be used as a tool for describing the soil acidification process. The question that was answered is how tree species (beech vs spruce) and type of soil horizon affect Al speciation. Our hypotesis is that spruce and beech forest vegetation are able to modify the chemical characteristics of organic horizon, hence the content of Al species. Moreover, these characteristics are seasonally dependent. To answer these questions, a detailed chromatographic speciation of Al in forest soils under contrasting tree species was performed. The Jizera Mountains area (Czech Republic) was chosen as a representative mountainous soil ecosystem. A basic forestry survey was performed on the investigated area. Soil and precipitation samples (throughfall, stemflow) were collected under both beech and spruce stands at monthly intervals from April to November during the years 2008–2011. Total aluminium content and Al speciation, pH, and dissolved organic carbon were determined in aqueous soil extracts and in precipitation samples. We found that the most important factors affecting the chemistry of soils, hence content of the Al species, are soil horizons and vegetation cover. pH strongly affects the amount of Al species under both forests. Fermentation (F) and humified (H) organic horizons contain a higher content of water extractable Al and Al³⁺ compared to organo-mineral (A) and mineral horizons (B). With increasing soil profile depth, the amount of water extractable Al, Al³⁺ and moisture decreases. The prevailing water-extractable species of Al in all studied soils and profiles under both spruce and beech forests were organically bound monovalent Al species. Distinct seasonal variations in organic and mineral soil horizons were found under both spruce and beech forests. Maximum concentrations of water-extractable Al and Al³⁺ were determined in the summer, and the lowest in spring.     

Multi-geochemical background comparison and the identification of the best normalizer for the estimation of PTE contamination in agricultural soil

Environmental Geochemistry and Health - Identifying a suitable geochemical background level (GBL) and an appropriate normalizer is imperative for ensuring soil quality, health, and security. The...     

Crosslinked Poly(2-Hydroxyethyl Methacrylate) by Emulsion Templating: Influence of Crosslinker on Microcellular Structure

The synthesis of microcellular porous polymers based on 2-hydroxyethyl methacrylate (HEMA) by free radical polymerisation of a continuous phase of high internal phase emulsion (HIPE) is reported. N,N’-methylene bisacrylamide (MBAA) and glutaraldehyde are used as crosslinking agents. GA is added to the monomer phase either during the emulsion preparation or post polymerisation crosslinking of HEMA is performed. The crosslinker influences the morphological structure of porous poly(HEMA) materials. In the case of using MBAA as the crosslinker, homogeneous polyHIPE structure is obtained, with average cavities diameter approximately 8 μm and interconnecting pore diameter approximately 3 μm. In the case of using GA in situ crosslinking a polyHIPE is obtained exhibiting cavities of diameter approximately 12 μm and interconnecting pores of approximately 3 μm. Post polymerisation crosslinking with GA influence the structural features resulting in a different morphology. Samples are characterised using FTIR spectroscopy, scanning electron microscopy, nitrogen adsorption and swelling behaviour measurements. Polymers are prepared in the form of monoliths and membranes.     

Diameter distribution of some subalpine fir stands in central British Columbia

Diameter distributions of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in central British Columbia were investigated. Nine fire-originated, old-growth stands were selected with maximum tree age at breast height of about 300 years. The stage of stand development was determined by testing how well a negative exponential function matched the cumulative diameter distribution. As a comparison, the negative exponential function was also fitted on the frequency distributions. Eight out of the nine distributions showed fewer medium-sized trees and more large-sized trees than predicted by the negative exponential function. One stand showed relatively good fit, but failed the lack-of-fit test. Although the diameter distributions are close to a balanced stage, stand establishment patterns are still evident 300 years after disturbance.     

Assessment of Temporal and Spatial Variation of Nitrate Removal in Riparian Zones

The aim of this study was to monitor long-term temporal and spatial groundwater NO₃^- removal efficiencies in different riparian zones via a limited number of sampling wells. Groundwater NO₃^- concentrations were measured fortnightly or monthly over a period of two years using transects of ground water sampling wells. Depending on the level of the NO₃^- load (up to 120mgNL^-1 at the input side of the riparian zone a distance of 10 to 30m was needed to remove NO₃^- from the groundwater below 11.3mgNL^-1. Considering all seasons, the mixed vegetation and grass riparian site succeeded to remove groundwater NO₃^- efficiently (92—100% within a distance of 30m. The forested riparian zone removed 72—90% of the total NO₃^- input within a distance of 30m. Evidence emerged that NO₃^- could also be removed actively at depths up to 2m, due to the presence of organically enriched layers of alluvial deposits or roots. Our four dimensional approach (three dimensional space and time), in combination with a limited number of sampling wells, was shown to be a useful monitoring tool to assess the variability of NO₃^- removal in riparian zones.