论文检索 |
|||||
|
总访问量：5360152次 总访客量：313684人 | |||||
| 关键词:... | |||||
| 期刊：... | |||||
所有论文 |
|||||
23401. 题目: Dynamics of maturity and stability indices during decomposition of biodegradable city waste using rapo-compost technology Expeditious growth of population and urbanization has led the global challenge for Municipal Solid Waste (MSW) management. An investigation on rapid composting of biodegradable city waste was carried out with three treatments, two on a rapo-composter with and without consortia of thermophilic ligno-cellulolytic microbes and third is the common practice of compost producer. The quality of compost i.e. the maturity and stability index was tested at four different stages of decomposition. After 30 days of decomposition it was elucidated that rapo-composter with consortia (Bacillus sps., Streptomyces sps., Rhizomucor pusillus and Aspergillus flavus) fasten the decomposition time. This paper finds uniqueness in deriving 10 maturity parameters, 6 stability parameters with one parameter as confirmatory test of compost toxicity. It was concluded from the study that the Water Soluble Carbon (WSC) and Organic Nitrogen (Org. N) ratio is the key regulator of maturity parameter and the dehydrogenase (DHA) activity is important factor for compost stability. | |||||
23402. 题目: Ball-milled, solvent-free Sn-functionalisation of wood waste biochar for sugar conversion in food waste valorisation The use of biomass wastes for biochar production is a promising waste management option, and biochars can be potentially applied in the food waste recycling industry to produce value-added chemicals. In this study, an advanced Sn-functionalised biochar catalyst was synthesised via a novel solvent-free ball milling protocol to facilitate the isomerisation of glucose to fructose. Raw wood biomass (W) and its derived biochars pyrolysed at low (LB, 400 °C) and high (HB, 750 °C) temperatures were investigated as catalyst supports. The interactions between Sn and the carbonaceous supports were related to the surface chemistry of the catalysts. The raw W had a functional group-enriched surface, which provided more active sites for anchoring Sn, resulting in higher metal loading on the support compared to LB and HB. The annealing temperature was another critical factor determining the amount and speciation of loaded Sn. Catalytic conversion experiments indicated that SnW annealed at 750 °C exhibited the best fructose yield (12.8 mol%) and selectivity (20.2 mol%) at 160 °C for 20 min. The catalytic activity was mainly determined by the quantity and nature of active Sn sites. This study elucidated the roles of the carbon support and its surface chemistry for synthesising biochar-supported catalysts, highlighting a simple and green approach for designing effective solid catalysts for sustainable biorefineries. | |||||
23403. 题目: Effects of biogas slurry irrigation DOC/N ratios on the fate of soil nitrogen and GHG emissions: A laboratory study Following biogas slurry irrigation, high rates of nitrogen (N) leaching have been measured, and testing increased slurry ratios of dissolved organic carbon (DOC) to N as a potential technique to reduce leaching, have been evaluated in previous research. Here, we explored the effects of slurry DOC/N ratios on the fate of soil N and greenhouse gas (GHG) emissions in a laboratory study. Slurries with DOC/N ratios of 0.9, 7.3, and 17.3 were applied to soil columns. Overall, the application of biogas slurry with a DOC/N ratio of 0.9 and increasing the ratio, enhanced soil mineralization, N immobilization and denitrification, and resulted in net mineralization. Additionally, most of the applied N left the soil through gaseous N emissions rather than by N leaching. Increasing the slurry DOC/N ratio from 0.9 to 7.3 or to 17.3 reduced nitrous oxide (N2O) emissions by 13% and 25%, respectively, and reduced methane (CH4) emissions by 1168% and 483%, respectively. In comparison, the respective carbon dioxide (CO2) emissions were 58% and 113% higher. In summary, an increased slurry DOC/N ratio contributes to soil CO2 emissions, but reduces both soil N2O and CH4 emissions. However, the reductions in N2O and CH4 emissions warrant further study. | |||||
23404. 题目: Size-dependent influence of NOx on the growth rates of organic aerosol particles | |||||
23405. 题目: A new perspective of membrane fouling control by ultraviolet synergic ferrous iron catalytic persulfate (UV/Fe(II)/PS) as pretreatment prior to ultrafiltration The main purpose of this study was to control membrane fouling by degrading natural organic matter, mainly based on free radicals, with a dead-end ultrafiltration system integrated with pretreatment. Four advanced oxidation processes, namely, ultraviolet (UV)/Fe(II), UV/persulfate (PS), Fe(II)/PS and UV/Fe(II)/PS, were used to pretreat raw water prior to ultrafiltration. The priority of the pretreatment effect followed the order of UV/Fe(II)/PS > Fe(II)/PS > UV/PS > UV/Fe(II). In the UV/Fe(II)/PS pretreatment (Fe(II) = 100 μM and PS = 400 μM), the removal rates of UV254 with a UV irradiation time of 60 min reached 93.07%. Degradation experiments of free-radical probes (carbamazepine) and free-radical scavenger addition (sodium hyposulfite or tert-butanol) showed that the sulfate radical (SO4−) was dominant in degrading organic compounds. The specific flow rate (J/J0) increased by 139.13% and the irreversible fouling resistance was reduced by 69.94%. The total interfacial energy of the colloid-membrane interaction decreased by 84.42% and the separation distance was shortened to ~2 nm. The release of Fe(III) from water under UV radiation and its possible conversion to Fe(II) were observed on the surface of the fouled membranes. After UV/Fe(II)/PS pretreatment, bulky and rough pollutant particles were transformed into a slew of sheet-contaminated layer with the appearance of numerous permeable holes, and the average surface roughness was reduced to 38.1 nm according to atomic-force-microscopy characterization. | |||||
23406. 题目: Soil microbial community dynamics mediate the priming effects caused by in situ decomposition of fresh plant residues Extreme climate events always leave numerous fresh plant materials (FOM) in forests, thus increasing the input of carbon (C) resources to soil system. The input of exogenous C may accelerate or inhibit the decomposition of soil organic carbon (SOC), which is defined as the positive or negative priming effect (PE), respectively. However, the characteristics and microbial mechanisms of PE caused by FOM remain unknown. A 110-day in situ soil incubation experiment was conducted in a subtropical forest, with 13C-labeled fresh leaves from four native species (Castanopsis fissa, CF; Pinus massoniana, PM; Machilus chekiangensis, MC; and Castanopsis chinensis, CC) serving as the FOM respectively. We measured the CO2 effluxes derived from 13C-labeled FOM and soil, and the composition and diversity of soil bacterial and fungal communities throughout the incubation to explore the correlations between PE and microbial attributes. As a result, the PE caused by FOM inputs were negative initially but became positive after 61 d. The FOM decomposition rate was positively related to PE intensity, and there was a significant difference between coniferous and broadleaved species in the middle period of the study. More than 77% of the total C lost from FOM was emitted as CO2, indicating that FOM-C serves as an energy resource for soil microbes. The α-diversity of the bacterial community at genus-level showed significantly positive correlation with PE at 24 d, and the composition of bacterial community at OTU-level had a marked relationship with the PE between 24–110 d. The relationship between fungal community diversity and composition with PE was only observed at 7 and 110 d, respectively. This study firstly investigated the patterns of PE resulted from numerous FOM input, and the results suggested that soil bacterial community, in particular the Actinobacteria and Actinobacteria phyla, played a more important role in triggering such PEs than fungal community. | |||||
23407. 题目: Implications of layered double hydroxides assembled biochar composite in adsorptive removal of contaminants: Current status and future perspectives In recent years, biochar composites have received considerable attention for environmental applications. This paper reviews the current state of research on Layered Double Hydroxides (LDHs) tailored biochar composites in terms of their synthesis methods, characteristics, and their use as adsorbents for the removal of various pollutants from water, highlighting and discussing the key advancement in this area. The adsorption potential of LDHs-biochar composites for different inorganic and organic contaminants, important factors affecting composites' properties and the adsorption process, and the mechanisms involved in adsorption are discussed in this review. Though the adsorption capacities are high for the composites studied, partition coefficient which suggest the performance of composites remain low for most adsorbents. Despite the recent progress in the synthesis of LDHs-biochar composites, further research is needed to improve the performance of composites for different classes of aquatic pollutants, and to test their applicability in pilot-scale with real wastewater under real environmental conditions. | |||||
23408. 题目: Anaerobic digestates from sewage sludge used as fertilizer on a poor alkaline sandy soil and on a peat substrate: Effects on tomato plants growth and on soil properties Anaerobic digestates from sewage sludge (SSADs) are a by-product of the wastewater treatment process that still preserves a certain agronomic interest for its richness in plant nutrients and organic matter. Fertilizing properties of two liquid and two dewatered SSADs were tested on tomato plants (Solanum lycopersicum L.). Pot experiments were performed on sandy soil and peat substrate under greenhouse conditions with a SSADs application rate of 170 kg N/ha over a period of three months. Beneficial effects of SSADs were reported on different growth parameters, revealing an increase in biomass and height up to 37.5 and 6-folds over untreated control. No phytotoxic effect occurred on SSAD-exposed plants. Chemical analysis of soils treated with SSADs showed enrichment of macro- and micro-nutrients as well as organic matter. In some cases, the chemical characterization of leaves revealed an enhancement of uptaken macronutrients. This study contributed in general to deepen the knowledge on the short-term growing season fertilizing effects of SSAD. Despite the treatment dosage was calculated only on nitrogen requirements, the study highlighted the importance of the other nutrients and organic matter on plant growth. | |||||
23409. 题目: Change of disinfection byproducts formation potential of natural organic matter after exposure to persulfate and bicarbonate Activated persulfate (PS) oxidation is a promising in situ remediation technology for groundwater and soils. Application of this technology to contaminated zones may result in a large quantity of PS residue in subsurface environment due to inefficient activation and repeated injection during remediation. In this study, we demonstrated that natural organic matter (NOM) molecules could be reconfigured due to exposure to unactivated PS and bicarbonate, resulting in reduced disinfection byproducts formation potential in post chlorination process. Fourier transformed inferred spectrometry (FTIR), size exclusive chromotraghy (SEC), and mass spectrometry (MS) analysis revealed that hydroxylation and carboxylation of NOM occurred, followed by intra-molecular coupling via ether bonds. The change of both the reactivity toward free chlorine and molecular structure of NOM during PS/bicarbonate treatment was well mimicked by 3,5-dihydroxylbenzoic acid, suggesting that phenolic moieties in NOM molecules were the main sites underwent transformation in the PS/bicarbonate system. We propose that peroxymonocarbonate (HCO4−) formed upon the reaction between PS and bicarbonate was the main reactive species responsible for the reconfiguration of NOM. It selectively attacked the phenolic moieties via single-electron abstracting mechanism, leading to phenoxy radical intermediates which couple to each other via C–O–C bonds. The findings of this study shed light on the environmental behaviors and impacts of PS in groundwater environment. | |||||
23410. 题目: Role of crystalline iron oxides on stabilization of inositol phosphates in soil Inositol phosphates selective retention in soil is related to their great affinity to iron (Fe) oxides, with which they interact by the formation of ligand exchange complexes. Soils contain from amorphous to crystalline Fe oxides forms, as goethite (Gt), whose effect on inositol phosphates retention is well-known. The contribution of other widespread crystalline Fe oxides as haematite (Hm), magnetite (Mt) and maghemite (Mh) is instead less known. These oxides display different phosphorus (P) retention and release capacities due to their specific surface properties and stability towards protons, organic acids and complexing agents. We therefore investigated: i) the extent and mechanisms of myo-inositol hexaphosphate (InsP6) and inorganic phosphate (Pi) adsorption on Gt, Hm, Mt and Mh, also studying the computational geometries of InsP6 molecule; ii) the reversibility of the reaction as affected by pH and in the presence of citrate; iii) the efficiency of NaOH-EDTA on P extraction. Compared to Gt, Hm retained less InsP6, due to the distribution of superficial –OH groups allowing for the interaction of two phosphate groups instead of four, as for Gt. Mt and Mh retained more InsP6 than Hm, also through precipitation processes due to a partial dissolution of the oxides caused by InsP6. Desorption of InsP6 in the pH range 3.5–8.5 was negligible, except for Hm, while citrate led to larger desorption, with no release from Gt. NaOH-EDTA extraction of InsP6 was instead particularly effective from Gt and less from the other oxides. The four crystalline Fe oxides thus showed different capacity to retain organic P in the form of InsP6 as a function of surface properties and stability of the mineral-P complexes, therefore influencing the extent of release, accumulation and turnover in soils. | |||||
23411. 题目: Light Absorption Properties of Organic Aerosol from Wood Pyrolysis: Measurement Method Comparison and Radiative Implications | |||||
23412. 题目: Persistent free radicals on N-doped hydrochar for degradation of endocrine disrupting compounds Metal-free carbocatalysts are raising increased interest in advanced oxidation processes (AOPs) for green degradation of aqueous organic pollutants. In the present study, a series of N-doped hydrochars (NHCs) was prepared from pinewood biomass and used in carbocatalysis toward catalytic peroxymonosulfate (PMS) activation to degrade refractory endocrine disrupting compounds. Nitrogen-doping was found to regulate the concentrations and types of persistent free radicals (PFRs) on hydrochar, promoting the electron transfer and oxidative degradation of the contaminants. Mechanistic studies revealed that graphitic N not only shows a strong electron transfer to facilitate PMS activation in a nonradical pathway, but also induces the formation of oxygen-centered PFRs from the structure defects for a radical oxidation pathway. More importantly, the PMS/NHC system demonstrates efficient degradation and satisfactory stability for real water treatment. This study has gained in-depth understanding on the roles of N-dopants in radical and nonradical pathways of biomass-based carbocatalysis, and will provide a promising and environmental-friendly route for efficient degradation of refractory endocrine disrupting compounds for green remediation. | |||||
23413. 题目: Waste-derived biochar: Applications and future perspective in microbial fuel cells Application of microbial fuel cell (MFC) is coming to the forefront as a dual-purpose system for wastewater treatment and energy recovery. Future research should emphasize on developing low cost field-scale MFCs for removal of organic matter, nutrients, xenobiotic and recalcitrant compounds from wastewaters and powering low energy devices. For achieving this, low cost electrodes, low cost yet efficient cathode catalysts and proton exchange membrane (PEM) should be developed from waste-based resources to salvage the waste-derived material as much as possible, thereby reducing the fabrication cost of this device. Biochar is one such low cost material, which has wide range of applications. This review discusses different applications of biochar in MFC, viz. in the form of standalone electrodes, electrocatalyst and material for PEM in light of different characteristics of biochar. Further emphasis is given on the future direction of research for implementation of biochar-based PEMs and electrodes in field-scale MFCs. | |||||
23414. 题目: Biochar alters nitrogen and phosphorus dynamics in a western rangeland ecosystem Application of biochar to soils has been proposed as a novel approach to managing wood residuals, enhancing soil carbon (C) storage and improving soil fertility; however, the majority of biochar studies have been conducted in agricultural systems that rely on tillage and nutrient inputs associated with annual cropping schemes. Few studies have evaluated the influence of biochar on soil processes in semi-natural rangeland ecosystems that feature more complex plant communities, lack deep soil disturbance, and have relatively few external nutrient inputs. In August 2018, biochar produced using wood waste from a lumber mill in Columbia Falls, MT, USA was applied to surface soils in replicated plots at an experimental ranch in western Montana to test the impact of biochar on soil C storage and nutrient management. A series of soil biochemical properties including total soil C and nitrogen (N), microbial N functional genes, available phosphorus (P) and the net accumulation of nutrients below surface soil layer were evaluated over a one-year period following biochar addition with or without a poultry litter based organic fertilizer. Biochar used alone slightly reduced soil NH4+, significantly increased soil nitrification potential, increased the relative abundance of the bacterial amoA gene, and increased the soil nitrate (NO3−) pool size, while having no net effect on soil inorganic N accumulation below surface soil. By contrast, biochar previously charged with poultry litter (termed charged biochar) had no effect on NH4+ availability, but a positive effect on amoA abundance. Charged biochar significantly reduced NH4+ accumulation below 25 cm depth compared to poultry litter alone. Biochar additions led to a shift towards a more fungal dominated community and a general increase in P availability. However, biochar used alone also contributed to a greater amount of soluble P collected below surface soil, an effect slightly attenuated when biochar was applied with poultry litter. Soil pH increased from 5.7 to 6.9 in response to biochar addition and was one of the dominant factors governing much of the observed changes in soil processes. Charged biochar helped retain soil nutrients and promoted soil C storage in this semi-natural rangeland system over one growing season. Changes in these soil pools and fluxes may influence various trophic groups affecting ecosystem functioning over time. | |||||
23415. 题目: Nitrate migration and transformations in groundwater quantified by dual nitrate isotopes and hydrochemistry in a karst World Heritage site Karst aquifers are extremely vulnerable to pollution, including from nitrate. This research advances a systematic evaluation of water quality dynamics and processes in a relatively pristine karst flow system impacted by seasonal tourism, in particular migration and transformation of nitrate. Water samples from the Shuifang Spring basin (Jinfoshan Karst World Heritage Site, Chongqing, China) were collected for analysis of ion concentrations and dual nitrate isotopes. The principal sampling sites included untreated tap water from the Jinfoshan Holiday Hotel (JHH), JHH septic system effluent, discharged effluent at Sinkhole #1, and groundwater at Shuifang Spring (SFS, the resurgence of the basin). Sampling from April 2017 through April 2018 showed that higher nitrate concentrations were observed at SFS during busy tourist seasons that occurred in the summer drought and winter dry seasons. Between the septic system and SFS, nitrate was diluted by rainwater and infiltration from the matrix regions of the karst aquifer in the wet season. The MixSIAR model quantitatively revealed that nitrate from manure and sewage (M&S), soil organic nitrogen (SON) and atmospheric precipitation (AP) contributed roughly 55%, 41% and 4% on average, respectively. The mixture of effluent and oxygen-rich tap water from the JHH underwent nitrification at the septic system and Sinkhole #1. After the nitrification and decomposition of organic matter with oxygen consumption in the effluent, denitrification was the dominant response to nitrate attenuation in the effluent of Sinkhole #1 during peak tourism periods. The septic effluent sinking into the aquifer deteriorated the groundwater quality, which was controlled by nitrification in the summer drought and winter dry seasons. In contrast, microorganisms in groundwater assimilated nitrate from effluent in the wet season. Because of the relatively pristine ambient background conditions and seasonal tourism, these results can inform interpretation of background and impacted nitrogen processes in a range of karst settings. | |||||
23416. 题目: Effect of clay on greenhouse gas emissions and humification during pig manure composting as supported by spectroscopic evidence To evaluate the effect of clay on greenhouse gas (GHGs) emissions and humification during pig manure (PM) composting, two lab-scale composting experiments, a control and a 10% clay treatment, were established. The results showed that adding clay reduced the emissions of CH4 and N2O by 45.88% and 86.79%, respectively, promoted the degradation of organic matter (OM) and facilitated the synthesis of humic acid (HA). The spectrum of dissolved organic matter (DOM) indicated that adding clay promoted the formation of aromatic carbon compounds and the degradation of aliphatic carbon. Furthermore, compared with the control, the spectral parameters including the specific UV absorbance at 254 nm (SUVA254), the specific UV absorbance at 280 nm (SUVA280) and the ration of the area at 435-480 nm and at 300-345 nm (A4/A1) of DOM were increased by 5.45%, 3.66% and 29.26%, respectively. Combined with the excitation - emission matrix (EEM) and the percentage fluorescence response (Pi,n), the clay amendment promoted the decomposition of tyrosine and Tryptophan and the formation of humic-like substances, and thus increased humification. The variation in the HA/fulvic acid and the humification index confirmed these results. Therefore, clay amendment is beneficial for reducing GHG emissions, promoting humification and aromatization during pig manure composting. | |||||
23417. 题目: Logging residue piles of Norway spruce, Scots pine and silver birch in a clear-cut: Effects on nitrous oxide emissions and soil percolate water nitrogen We analysed how logging residue (LR) piles of common tree species in Finland, Norway spruce (Picea abies (L.) H. Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth), affect nitrogen (N) losses in forest soil after final felling. A Norway sprucedominated stand was clear-cut and followed by two experimental setups to study the nitrous oxide (N2O) emissions and leaching of carbon (C) and N. Experiments consisted of four treatments: tree species treatments consisting of 40 kg m−2 of LR and a control treatment without residues. The C losses were monitored as dissolved organic carbon (DOC), the N losses as ammonium (NH4-N), nitrate (NO3-N) and dissolved organic nitrogen (DON) fluxes and concentrations in soil percolation waters and the N2O emissions as fluxes from the forest soil to the atmosphere. In addition the soil temperatures, the molecular size distribution of the DOC from the soil percolation waters and the origin of the N2O production were determined. The LR piles lowered the soil temperatures and, especially those of birch, increased the concentrations of NO3-N in the soil percolation waters already 1 year after the establishment of the piles. The LR piles increased the NH4-N concentrations. The smallest molecular size fraction (<1 kD) of DOC predominated in all treatments. The N2O fluxes peaked under the piles during the second and third growing seasons; however, the inconsistent fluxes tended to be low. The production of N2O was driven by both nitrification and denitrification processes, the proportion depending on the tree species. Our results indicate that LR piles accelerate N losses 1 year after the clear-cutting, especially NO3-N, which predominates in the soil percolation waters under the birch residues, whereas spruce residues tend to stimulate N2O emissions longer. These results have implications for sustainable forest management practices and nutrition of regrowing vegetation. | |||||
23418. 题目: Exopolysaccharides may increase biocrust rigidity and induce runoff generation The potential of biocrusts (biological soil crusts) to generate runoff is a matter of great controversy, especially in arid and semiarid regions. Most authors maintain that runoff in the presence of biocrusts is generated as a result of hydrophobicity, crust structure, texture or surface roughness. Hypothesizing that runoff over biocrusts may result from partial pore clogging, brought on by extracellular polymeric substances (EPS), we compare two crust types from Nizzana in the northwestern Negev, Israel (NIZID, NIZPON) that readily generate runoff under natural field conditions to a crust type from Nizzanim in the southern coast of Israel (NIMID) that fails to generate runoff. We hypothesize that biocrust-induced EPS of the NIZ crusts will have different biochemical and viscoelastic properties than that of NIM. We conducted sprinkling experiments on the crusts, measured the biochemical properties (thickness, water repellency, compressive strength, water-holding capacity, silt and clay content, roughness) and the adhesion and viscoelastic properties of the crust EPS using quartz crystal microbalance with dissipation monitoring (QCM-D). Both crusts were not water repellent and were characterized by a relatively smooth surface. The NIZ crusts were however characterized by higher water-holding capacity and compressive strength. As far as the EPS is concerned, higher shear viscosity and shear modulus characterized the NIZ crusts, indicating higher crust integrity and rigidity and the formation of durable mineral grain-EPS matrix of the NIZ crusts. The findings point to a possible link between crust rigidity and runoff coefficients providing supporting evident for the role played by EPS in crust formation and runoff generation. Knowledge regarding the potentiality of runoff and hence water redistribution may assist in ecosystem management and agroforestry practices. | |||||
23419. 题目: Disulfide polymer grafted polypropylene/polyethylene filter media for selective cadmium removal Heavy metal pollution caused by stormwater runoff has triggered a demand for effective heavy metal sorbents. Effective heavy metal removal using conventional stormwater runoff treatment processes that employ filtration mechanisms as primary removal mechanisms is difficult. Therefore, we attempt to improve cadmium removal performance by attaching disulfide polymer (DiS-COP) containing soft bases, thiols, onto the surface of polypropylene/polyethylene (PP/PE) fiber media, which is widely used for stormwater runoff treatment. Material characterization demonstrated that DiS-COP was successfully grafted and grown on the surface of PP/PE (Dis-PP/PE). The batch and continuous flow adsorption capacities of Dis-PP/PE were 81.1 mg/g and 2.33 mg/g, respectively, which is 40 times higher than those of pristine PP/PE. Applicability of DiS-PP/PE at pH 6–8 was demonstrated, and effects of calcium and humic acid on cadmium adsorption were investigated. Calcium marginally affected cadmium adsorption, which can be explained using the Hard and soft (Lewis) acids and bases theory (HSAB), but cadmium removal efficiency decreased owing to humic acid (HA) -Cd complex formation and agglomeration in the presence of organic material. In a breakthrough test, the adsorption column exhibited complete cadmium uptake over 24 h until it reached the breakthrough point. Therefore, heavy metal adsorption performance of PP/PE was successfully enhanced by grafting DiS-COP on its surface. | |||||
23420. 题目: The spontaneous secondary synthesis of soil organic matter components: A critical examination of the soil continuum model theory The Soil Continuum Model questions the occurrence of any independent natural process of secondary synthesis that generates compounds structurally distinct from plant or microbial metabolites. This review shows that a vast volume of interdisciplinary scientific evidence supports the formation of relevant non-pre-existing complex molecules exhibiting various types of structures. These molecules form during degradation and decay of biological cell components. The spontaneous abiotic and enzymatically catalysed reactions of components of organic residues and of their oxidative decomposition products suggested by state-of-the-art studies are indeed those proposed by most of the classical descriptions of humification. The review also highlights the chemically active role of pedofauna, explaining why the apparently harsh conditions of alkaline extraction of HS cannot be considered un-natural. Many insects and larvae feeding on foliage of plants with a high content of tannins have a midgut pH above 9. Albeit, reducing conditions are often maintained to avoid oxidation, peroxidases are active in the intestinal tract and pass on to feces. Polyphenols are then immediately enzymatically oxidized to their reactive quinone form, once feces are excreted and exposed to oxygen. Implications of our current knowledge on the reactivity of plant components in soil are discussed in relation with the present state of the art research on humic substances. Contrary to claims by the Soil Continuum Model theory, complimentary modern approaches need to be used to understand the complexity of soil organic matter. | |||||
