Effects of pyrolysis and incineration on the phosphorus fertiliser potential of bio-waste- and plant-based materials.

Land application of biomass materials and their products of thermal treatment (biochars and ashes) can offset the unsustainable use of soluble P fertilisers. However, few evaluations of P fertiliser potential have systematically addressed diverse biomass types with contrasting P contents. This paper evaluates the relative P fertiliser potential of four P-rich biowastes (animal bone, poultry manure, pig slurry, and a municipal sewage sludge) and three low-P, plant-based materials (reeds [Phragmites australis L.], rice husks [Oryza sativa L.] and cocoa prunings [Theobroma cacao L.]) and their biochars and ashes. We utilised three complementary approaches: P extractability in single solvents (2% formic and citric acids, and 1 M neutral ammonium citrate); sequential chemical P fractionation, and P dissolution/desorption kinetics. In most cases, pyrolysis and incineration of the P-rich biowastes increased P extractability (% TP) in the single solvents, whilst decreasing water-soluble P. For pig slurry, for example, pyrolysis reduced water-soluble P 20-fold, with corresponding increases observed not only in the solvent-extractable P but also in the pool of potentially plant available, NaHCO3-Pi fraction (e.g., 17 to 35% TP). These complementary datasets were also evident for the low-P feedstocks and thermal products; e.g., pyrolysis increased the NaHCO3-Pi fraction in reed feedstock from 6 to 15% TP. For all biomass feedstocks, biochars and ashes, pseudo-second order P-release kinetics provided the best fit with the experimental data. The data demonstrate scope for using pyrolysis to upgrade the P fertiliser value of a wide range of biomass materials whilst reducing their environmental impact.

Stepwise redox changes alter the speciation and mobilization of phosphorus in hydromorphic soils.

Sustainable engineering and management of hydromorphic arable soils need deep knowledge about the redox-mediated interactions between nutrients and soil colloids. Consequently, we examined the redox-mediated interactions of P with metal oxides and organic carbon (OC) in toe-, mid-, and upper-slope arable soils under dynamic redox changes using geochemical (biogeochemical microcosm), spectroscopic (XANES), and molecular (quantum chemical calculations (QCC)) approaches. We controlled the redox potential (EH) in two directions i.e., 1) slowly oxidizing direction (SOD; EH increased from -286 to +564 mV); and 2) slowly reducing direction (SRD; EH decreased from +564 to -148 mV). In the SOD of all soils, P, Fe2+ and OC mobilized at EH ≤ 200 mV, due to the pH decrease from 7.2 to 4.1 and dissolution of Fe-oxyhydroxides/carbonates, as indicated by the decrease of Fe-P and Ca-P determined by P-K-edge-XANES. At EH > 200 mV, P immobilized due to the strong P binding with Fe3+ as suggested by QCC. In the SRD of mid-slope-soil, P immobilized with decreasing EH, due to pH increase and P retention by aromatic carbon and/or precipitation by carbonates, as supported by increase of organic-P and Ca-P. These findings help for management of P in arable soils.

Redox-induced mobilization of phosphorus in groundwater affected arable soil profiles.

Mobilization of phosphorus (P) in arable soils might be affected by groundwater fluctuations and the associated changes in redox potential (EH). However, the impact of systematic changes of EH on P mobilization in redoximorphic arable soils along a catena has not been studied so far. Therefore, we investigated P mobilization under different redox conditions in top- and sub-soil horizons of three groundwater affected arable soils along a slight slope (toe-, mid-, and upper-slope position) in Northern Germany using an automated biogeochemical microcosm system. The impact of pH, Al, Fe, Mn, and dissolved organic carbon (DOC) on P mobilization was also studied. The initial EH (+351 to +431 mV) and pH (6.5-7.0) decreased in all soil samples (EH = -280 mV; pH = 4.4) when creating a slurry. Thereafter, the pH increased to 7.1 and 6.4 with increasing EH in the mid-and toe-slope soil, respectively. Concentrations of dissolved P ranged between 20.8 mg L-1 under low EH in the toe slope topsoil and 0.69 mg L-1 under high EH in the toe- and mid-slop subsoil. Concentrations (mg L-1) of dissolved Fe (0.31-13.3) and DOC (92-2651) increased under low EH and decreased under high EH. The increase of P mobilization under low EH and pH in the soils might be due to the release of P via the reductive and acidic dissolution of Fe-(oxhydr)oxides and/or due to soil organic matter mineralization. The high mobilization of P under reducing conditions may increase its bioavailability; however, it may increase its loss in the soils, particularly in the toe slope profile.

Speciation and sorption of phosphorus in agricultural soil profiles of redoximorphic character.

Controlled drainage is considered as a soil management tool to improve water supply to crops and reduce nutrient losses from fields; however, its closure may affect phosphorus (P) mobilization in soil. To assess the P mobilization potential, three soil profiles with redoximorphic features were selected along a slight hill in Northern Germany. Soil samples from three depths of each profile were characterized for basic properties, total element content, oxalate- and dithionite-extractable pedogenic Al, Fe and Mn (hydr)oxides, P pools (sequential extraction), P species [P K-edge X-ray absorption near-edge structure (XANES) spectroscopy] and P sorption behavior. In topsoil (~ 10 cm depth), labile P (H2O-P + resin-P + NaHCO3-P) accounted for 26-32% of total P (Pt). Phosphorus K-edge XANES revealed that up to 49% of Pt was bound to Al and/or Fe (hydr)oxides, but sequential fractionation indicated that > 30% of this P was occluded within sesquioxide aggregates. A low binding capacity for P was demonstrated by P sorption capacity and low Kf coefficients (20-33 [Formula: see text]) of the Freundlich equation. In the subsoil layers (~ 30 and ~ 65 cm depth), higher proportions of Al- and Fe-bound P along with other characteristics suggested that all profiles might be prone to P mobilization/leaching risk under reducing conditions even if the degree of P saturation (DPS) of a profile under oxic conditions was < 25%. The results suggest that a closure of the controlled drainage may pose a risk of increased P mobilization, but this needs to be compared with the risk of uncontrolled drainage and P losses to avoid P leaching into the aquatic ecosystem.

Influence of metal ions on glyphosate detection by FMOC-Cl.

Glyphosate (GLP, N-(phosphonomethyl)glycine) is the most important broadband herbicide in the world, but discussions are controversial regarding its environmental behaviour and distribution. Residue analyses in a variety of environmental samples are commonly conducted by HPLC-MS where GLP needs to be derivatised with 9-fluoromethoxycarnonyl chloride (FMOC-Cl). Since this derivatisation reaction was suspected to be inhibited by metal ions in the sample matrix, the present study provides a comprehensive experimental study of the effect of metal ions (Al3+, Ca2+, Cd2+, Co2+, Cu2+, Fe2+, Fe3+, Mg2+, Mn2+, Zn2+) on derivatisation and GLP recovery. Results show that some metals (Cd2+, Co2+, Cu2+, Mn2+ and Zn2+) decreased the GLP recovery down to 19 to 59%. Complementary, quantum chemical modelling of 1:1 GLP-metal complexes as well as their reactivity with respect to FMOC-Cl was performed. Here, a decrease in reactivity of FMOC-Cl towards GLP-metal complexes is observed; i.e. the reaction is non-spontaneous in contrast to the free GLP case. The present results are in accord with previous studies and provide an explanation that full GLP recovery in different matrices was never reached. Remedy strategies to compensate for the inhibition effect are explored such as pH adjustment to acidic or alkaline conditions or addition of ethylenediaminetetraacetic acid (EDTA). In general, our results question the use of internal isotopic labelled standards (ILS) since this presupposes the presence of the analyte and the ILS in the same (free) form.

Bacterial potentials for uptake, solubilization and mineralization of extracellular phosphorus in agricultural soils are highly stable under different fertilization regimes.

Phosphorus is one of the most important macronutrient for plants. In agriculture, amending fertilizer with phosphorus (P) is common practice. However, natural phosphorus sources are finite, making research for more sustainable management practices necessary. We postulated that the addition of carbon (C) and nitrogen (N) would stimulate phosphorus mobilization by bacteria because of their desire to maintain a stable intracellular C:N:P stoichiometry. Therefore, we chose a metagenomic approach to investigate two agricultural soils, which only received mineral N fertilizer or mineral N and organic fertilizer for more than 20 years. The most abundant genes involved in the acquisition of external P sources in our study were those involved in solubilization and subsequent uptake of inorganic phosphorus. Independent of site and season, the relative abundance of genes involved in P turnover was not significantly affected by the addition of fertilizers. However, the type of fertilization had a significant impact on the diversity pattern of bacterial families harbouring genes coding for the different P transformation processes. This gives rise to the possibility that fertilizers can substantially change phosphorus turnover efficiency by favouring different families. Additionally, none of the families involved in phosphorus turnover covered all investigated processes. Therefore, promoting bacteria which play an essential role specifically in mobilization of hardly accessible phosphorus could help to secure the phosphorus supply of plants in soils with low P input.

Handling the phosphorus paradox in agriculture and natural ecosystems: Scarcity, necessity, and burden of P.

This special issue of Ambio compiles a series of contributions made at the 8th International Phosphorus Workshop (IPW8), held in September 2016 in Rostock, Germany. The introducing overview article summarizes major published scientific findings in the time period from IPW7 (2015) until recently, including presentations from IPW8. The P issue was subdivided into four themes along the logical sequence of P utilization in production, environmental, and societal systems: (1) Sufficiency and efficiency of P utilization, especially in animal husbandry and crop production; (2) P recycling: technologies and product applications; (3) P fluxes and cycling in the environment; and (4) P governance. The latter two themes had separate sessions for the first time in the International Phosphorus Workshops series; thus, this overview presents a scene-setting rather than an overview of the latest research for these themes. In summary, this paper details new findings in agricultural and environmental P research, which indicate reduced P inputs, improved management options, and provide translations into governance options for a more sustainable P use.

Phosphorus transformations in plant-based and bio-waste materials induced by pyrolysis.

Strategies are needed to increase the sustainability of phosphorus (P) fertiliser management in agriculture. This paper reports on the potential of pyrolysis treatment to recycle P from renewable materials previously regarded as wastes. The study used K-edge X-ray absorption near-edge structure (XANES) spectroscopy to examine chemical forms of P in the waste feedstock materials and corresponding biochars (pyrolysis at 480-500 °C) of four ligno-cellulosic, plant-based residues and five relatively P-rich livestock and water-treatment by-products, to acquire information on changes in potential P fertiliser value. Pyrolysis enriched P in the biochars by factors of 1.3-4.3, thus offering wide-ranging P fertiliser potential. XANES spectroscopy revealed hydroxyapatite (HAP) as one of the dominant chemical P compounds in the feedstocks, ranging from 14% (rice husks) to 98% (animal bone) of total P. For most materials, pyrolysis increased the proportion of HAP, and pyrophosphates were generated in several cases. These alterations possibly lead to diversity in the P solubility characteristics of the biochars if used as soil amendments; this is an important property of environmentally sound P fertilisers.

Plant available phosphorus in soil as predictor for the leaching potential: Insights from long-term lysimeter studies.

This study aimed to demonstrate the impact of phosphorus (P) mineral fertilization on topsoil P content and P leaching. We evaluated 83 datasets from 25 years from lysimeter experiments involving different cropping systems (winter crop, summer crop and autumn tillage, harvested grass) or unfertilized fallow, four types of soil texture, and three levels of applied mineral P fertilizer. A positive monotonic and significant correlation was indicated between P in the topsoil determined by the double lactate method (P DL) and the yearly flow-weight total (TP) concentrations in leachates with Spearman rank correlations r s (r s > 0.183) and probability (p) < 0.05. The present German recommended rates of P mineral fertilization are proposed insufficient to protect fresh and marine waters from undesired P pollution and eutrophication. A long-term reduction of excess soil P is urgent along with other measures to mitigate high P inputs to surface and ground waters.

Wood species affect the degradation of crude oil in beach sand.

The addition of wood chips as a co-substrate can promote the degradation of oil in soil. Therefore, in the present study, the tree species-specific impact of wood chips of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and Western balsam poplar (Populus trichocarpa L.) on the degradation of crude oil was tested in beach sand in a 4-week incubation experiment. The CO2-C release increased in the order of control without wood chips < +spruce < +pine < +poplar. Initial and final hydrocarbon concentrations (C10 to C40), as indicators for the oil degradation, were determined with gas chromatography-flame ionization detection (GC-FID). The degradation increased for the light fraction (C10 to C22), the heavy fraction (C23 to C40) as well as the whole range (C10 to C40) in the order of control without wood chips (f(degrad.) = 23% vs. 0% vs. 12%) < +poplar (f(degrad.) = 49% vs. 19% vs. 36%) < +spruce (f(degrad.) = 55% vs. 34% vs. 46%) < +pine (f(degrad.) = 60% vs. 44% vs. 53%), whereas the heavy fraction was less degraded in comparison to the light fraction. It can be concluded, that the tree species-specific wood quality is a significant control of the impact on the degradation of hydrocarbons, and pine wood chips might be promising, possibly caused by their lower decomposability and lower substrate replacement than the other wood species.

Bone char: a clean and renewable phosphorus fertilizer with cadmium immobilization capability.

Soil contamination with Cd from P fertilizer and other anthropogenic and geogenic sources is a serious problem. In situ immobilization by P application to soil is known as an applicable remediation technique leading to reduced Cd uptake by plants, and use of a Cd-free P fertilizer from renewable sources would be most favorable. Bone char (BC) (15% P, 28% Ca, 0.7% Mg) may be used as such a quality P fertilizer, but it is unknown if its dissolution in soil provides sufficient P and immobilizes Cd in moderately contaminated soils. We incubated BC and triple superphosphate (TSP) in 11 soils that contained between 0.3 to 19.6 mg Cd kg and determined the kinetics of P dissolution during a time period of 145 d. The concomitant Cd immobilization was determined by extracting the mobile Cd with 1 mol L NHNO solution. For most soils, BC increased the concentration of labile P immediately after application, reaching a maximum after 34 d, although the solubility was below that of TSP (2.9-19.3 vs. 4.1-24.0%). Among five kinetic models, the Langmuir-type equation provided the best description of P dissolution from BC and TSP. The Cd immobilization resulting from BC dissolution exceeded that of TSP by a factor of 1.4 to 2.7. The P dissolution from BC was negatively correlated with pH and positively with P sorption capacity, whereas Cd immobilization was positively correlated with soil pH. These causal relationships were expressed in multiple equations that enable predictions of P dissolution and Cd immobilization and thus may help to introduce BC as sustainable P fertilizer and useful soil amendment.

Controlled experimental soil organic matter modification for study of organic pollutant interactions in soil.

Interactions of organic pollutants with soil organic matter can be studied by adsorption of the pollutants on well-characterized soil samples with constant mineralogy but different organic matter compositions. Therefore, the objectives of the current study are establishing a set of different, well-characterized soil samples by systematic modifications of their organic matter content and molecular composition and prove these modifications by advanced complementary analytical techniques. Modifications were done by off-line pyrolysis and removal/addition of hot-water extracted organic fraction (HWE) from/to the original soil sample. Both pyrolysis-field ionization mass spectrometry (Py-FIMS) and synchrotron-based C- and N- X-ray absorption near-edge structure spectroscopy (XANES) were applied to investigate the composition of the soil organic matter. These complementary analytical methods in addition to elemental analysis agreed in showing the following order of organic matter contents: pyrolyzed soil

Greenhouse and field cultivations of antigen-expressing potatoes focusing on the variability in plant constituents and antigen expression.

The production of plant-derived pharmaceuticals essentially requires stable concentrations of plant constituents, especially recombinant proteins; nonetheless, soil and seasonal variations might drastically interfere with this stability. In addition, variability might depend on the plant organ used for production. Therefore, we investigated the variability in plant constituents and antigen expression in potato plants under greenhouse and field growth conditions and in leaves compared to tubers. Using potatoes expressing VP60, the only structural capsid protein of the rabbit haemorrhagic disease virus (RHDV), CTB, the non-toxic B subunit (CTB) of the cholera toxin (CTA-CTB(5)) and the marker protein NPTII (neomycinphosphotransferase) as a model, we compare greenhouse and field production of potato-derived antigens. The influence of the production organ turned out to be transgene specific. In general, yield, plant quality and transgene expression levels in the field were higher than or similar to those observed in the greenhouse. The variation (CV) of major plant constituents and the amount of transgene-encoded protein was not influenced by the higher variation of soil properties observed in the field. Amazingly, for specific events, the variability in the model protein concentrations was often lower under field than under greenhouse conditions. The changes in gene expression under environmental stress conditions in the field observed in another event do not reduce the positive influence on variability since events like these should excluded from production. Hence, it can be concluded that for specific applications, field production of transgenic plants producing pharmaceuticals is superior to greenhouse production, even concerning the stability of transgene expression over different years. On the basis of our results, we expect equal or even higher expression levels with lower variability of recombinant pharmaceuticals in the field compared to greenhouse production combined with approximately 10 times higher tuber yield in the field.

Effects of elm bark extracts from Ulmus laevis on human chorion carcinoma cell lines.

PURPOSE: The potential of substances from elm bark extracts to affect cancer has been described in several studies. In this study, the anticancer effects of extracts from Ulmus laevis bark were tested in hormone-dependent gynecological tumours using human chorion carcinoma cell lines. METHODS: The molecular-chemical composition of the bark extract was analysed by pyrolysis-field ionisation mass spectrometry. The influence of the extracts was determined on cell vitality and cytotoxicity in the human chorion carcinoma cell lines Jeg3 and BeWo in comparison with primary trophoblast cells. RESULTS: The elm bark extract was mainly composed of triterpenes, phytosterols, free fatty acids and suberins with lower amounts of dilignols and lipids. The elm bark extract significantly inhibited the vitality of Jeg3 and BeWo cells but increased the vitality of primary trophoblast cells. CONCLUSIONS: Substances extracted from elm bark might have beneficial effects for the prevention of hormone-dependent tumours.

Phosphorus speciation in agro-industrial byproducts: sequential fractionation, solution (31)P NMR, and P K- and L(2,3)-edge XANES spectroscopy.

Little is known about P species in agro-industrial byproducts from developing countries, which may be either pollutants or valuable soil amendments. The present study speciated P in dry (COD) and wet (COW) coffee, sisal (SIS), barley malt (BEB) and sugar cane processing (FIC) byproducts, and filter cakes of linseed (LIC) and niger seed (NIC)with sequential fractionation, solution (31)P nuclear magnetic resonance (NMR) spectroscopy, and P K- and L(2,3)-edge X-ray absorption near-edge structure (XANES) spectroscopy. The sequential P fractionation recovered 59% to almost 100% of total P (P(t)), and more than 50% of P(t) was extracted by H(2)O and NaHCO(3) in five out of seven samples. Similarly, the NaOH + EDTA extraction for solution (31)P NMR recovered 48-94% of P(t). The (31)P NMR spectra revealed orthophosphate (6-81%), pyrophosphate (0-10%), and orthophosphate monoesters (6-94%). Orthophosphate predominated in COD, COW, SIS, and FIC, whereas BEB, UC, and NIC were rich in orthophosphate monoesters. The concentrations of P(i), and P(o) determined in the sequential and NaOH + EDTA extractions and (31)P NMR spectra were strongly and positively correlated (r = 0.88-1.00). Furthermore, the P K- and L(2,3)-edge XANES confirmed the H(2)SO(4)--P(i) detected in the sequential fractionation by unequivocal identification of Ca--P phases in a few samples. The results indicate that the combined use of all four analytical methods is crucial for comprehensive P speciation in environmental samples and the application of these byproducts to soil.

Phosphorus speciation in sequentially extracted agro-industrial by-products: evidence from X-ray absorption near edge structure spectroscopy.

The phosphorus (P) in agro-industrial by-products--a potential source of freshwater eutrophication but also a valuable fertilizer--needs to be speciated to evaluate its fate in the environment. We investigated to what extent X-ray absorption near edge structure (XANES) spectroscopy at the P K- and L2.3-edges reflected differences in sequentially extracted filter cakes from sugarcane (Saccharum officinarum L.) (FIC) and niger seed (Guizotia abyssinica Cass.; NIC) processing industry in Ethiopia. The P fractionation removed more labile (54%) and H2SO4-P (28%) from FIC than from NIC (18% labile, 12% H2SO4-P). For the FIC residues after each extraction step, linear combination (LC) fitting of P K-edge spectra provided evidence for the enrichment of Ca-P after the NaOH-extraction and its almost complete removal after the H2SO4-treatment. The LC-fitting was unsuccessful for the NIC samples, likely because of the predominance of organic P compounds. The different proportions of Ca-P compounds between FIC (large) and NIC (small) were more distinctive in L2-than in the K-edge XANES spectra. In conclusion, the added value of complementary P K- and L2.3-edge XANES was clearly demonstrated, and the P fractionation and speciation results together justify using FIC and NIC as soil amendments in the tropics.

Inhibitory effects of bark extracts from Ulmus laevis on endometrial carcinoma: an in-vitro study.

Anti-inflammatory effects of elm tree have been shown in several studies. Besides this, protective effects of components of elm bark on damaged tissue have also been described. This study was carried out to investigate the antitumour potential of an ethanolic extract isolated from Ulmus laevis in the hormone-dependent endometrial carcinoma cell line RL95-2. A range of 2.5-500 microg/ml of elm bark extract was used as standard concentrations. The molecular-chemical composition of the bark extract was analysed by pyrolysis-field ionization mass spectrometry. The influence of the bark extracts was determined on cell vitality [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test], cell proliferation (5-bromo-2-deoxyuridine test) and cytotoxicity (lactate dehydrogenase test) in the human endometrial carcinoma cell line RL 95-2. By pyrolysis-field ionization mass spectrometry, the main substance classes of the extract as a composition of sterols/triterpenes, free fatty acids and a group of phenols, lignin monomers and flavonoids was identified. Our study showed a significant inhibition of cell vitality and proliferation measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test up to 5 microg/ml extract and up to 100 microg/ml according to the 5-bromo-2-deoxyuridine test. Concentrations of 500 microg/ml induced a significant inhibition of cell vitality up to 80% and cell proliferation up to 81.5%. A significant cytotoxity was not observed. The results lead to the assumption that the bark extract from Ulmus laevis has antiproliferation and anticancer potential in hormone-dependent endometrial carcinoma cells.

Phosphorus L(2,3)-edge XANES: overview of reference compounds.

Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy is becoming an increasingly used tool for the element speciation in complex samples. For phosphorus (P) almost all XANES measurements have been carried out at the K-edge. The small number of distinctive features at the P K-edge makes in some cases the identification of different P forms difficult or impossible. As indicated by a few previous studies, the P L(2,3)-edge spectra were richer in spectral features than those of the P K-edge. However, experimentally consistent spectra of a wide range of reference compounds have not been published so far. In this study a library of spectral features is presented for a number of mineral P, organic P and P-bearing minerals for fingerprinting identification. Furthermore, the effect of radiation damage is shown for three compounds and measures are proposed to reduce it. The spectra library provided lays a basis for the identification of individual P forms in samples of unknown composition for a variety of scientific areas.

New evidence for the molecular-chemical diversity of potato plant rhizodeposits obtained by pyrolysis-field Ionisation mass spectrometry.

INTRODUCTION: Detailed descriptions of the molecular-chemical diversity in plant rhizodeposits are scarce. The vast majority of our knowledge is derived from a priori methods of analysis, such as GC-MS and HPLC. OBJECTIVE: To analyse the composition of rhizodeposits from the potato cultivar Solanum tuberosum L. cv. Albatros by pyrolysis -field ionisation mass spectrometry (Py-FIMS) and to explain differences in relation to plant growth stage and photoperiod. METHODOLOGY: Potato (Solanum tuberosum L.) plants were grown in non-sterile, native soil under controlled environmental conditions (plant chamber). Rhizodeposit samples were collected by leaching during two different growth stages and after the physiological day- and night-cycle. All leachate samples were investigated by Py-FIMS. Mass spectrometric data were evaluated by multivariate statistics. RESULTS: Screening of the rhizodeposits by Py-FIMS revealed a broad range of m/z signals. Low-molecular-weight substances of m/z 15-56 (8.1-18.6%), alkylaromatics (12.0-15.9%), phenols and lignin monomers (8.8-13.1%) and carbohydrates (6.0-11.2%) comprised the largest proportions of total ion intensity (TII). Mass signals with significantly different abundance at the various sampling dates were assigned to compound classes of carbohydrates, phenols and lignin monomers, lignin dimers, lipids, N-containing compounds, sterols, peptides and free fatty acids; these were supplemented by marker signals for N-acetylmuramic acid from bacterial cell walls and signal molecules for the regulation of secondary pathways such as 4-hydroxycinnamic acid and linolenic acid. CONCLUSION: Py-FIMS was well suited to detect the molecular-chemical diversity of potato plant rhizodeposits and, compared with traditional a priori analytical methods, provided detailed evidence for significant differences in the composition of rhizodeposits depending on growth stage and diurnal period.

Nitrogen K-edge XANES - an overview of reference compounds used to identify unknown organic nitrogen in environmental samples.

The chemical nature of soil organic nitrogen (N) is still poorly understood and one-third to one-half of it is typically classified as ;unknown N'. Nitrogen K-edge XANES spectroscopy has been used to develop a systematic overview on spectral features of all major N functions in soil and environmental samples. The absolute calibration of the photon energy was completed using the 1s --> pi* transitions of pure gas-phase N(2). On this basis a library of spectral features is provided for mineral N, nitro N, amino acids, peptides, and substituted pyrroles, pyridines, imidazoles, pyrazoles, pyrazines, pyrimidines and purine bases. Although N XANES was previously considered ;non-destructive', effects of radiation damage were shown for two compound classes and an approach was proposed to minimize it. This new evidence is integrated into a proposal for the evaluation spectra from environmental samples with unknown composition. Thus a basis is laid to develop N K-edge XANES as a complementary standard research method to study the molecular composition and ecological functions of ;unknown N' in soil and the environment.