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The steadily growing demand for fertilizers and increasing interest for organic inputs result in rapid expansion and diversification of the solid nitrogen (N) fertilizer market. Fertilizer legislations distinct different fertilizers classes (i.e. organic, organo-mineral, inorganic), but standards and norms related to nutrient- and carbon origin remain dynamic and lag behind. This, together with poor analytical understanding of commercially available N sources leaves many open questions to industries and farmers, fostering increased prevalence of fertilizer adulteration and false claims on the organic fertilizer market. This work presents a thorough, science-based multivariate assessment on a wide sample set (n = 52) of the solid N fertilizer market, including multiple state-of-the-art analytical attributes, such as stable isotopes of nitrogen and carbon. Results present the possibility to correctly (94%) classify N fertilizers using multivariate fingerprinting with linear discriminant analysis. We extract analytical cut-off values for discriminants indicative for ingredient origin and conclude that, when a fertilizer has (i) a bulk δ15N below 2‰; and (ii) a relatively high total N content (> 15%), from which (iii) a high share (> 50%) is water soluble (i.e. in ammonium or nitrate form), it is extremely unlikely to be of pure biologic origin. We also present additional analyses (e.g. amino acids, peptide sequences, δ13C of specific compounds, and stable isotopes of boron) that can then be used to further trace down the N sources in novel fertilizer products. This work contributes to future debates, regulations, and further development of analytical standards for solid N fertilizers, possibly to be used in fraud detection. [ABSTRACT FROM AUTHOR]

This study represents the first extensive residue analysis of prehistoric pottery from northern Belgium. It examines pottery use and culinary practices across the Mesolithic-Neolithic transition, from the late 6th to the early 4th millennium cal BC. Residue analyses were performed on more than 200 samples from nine archaeological sites, representing different cultural groups from this transitional phase. This includes the analysis of charred food residues encrusted on the vessel surfaces by elemental analysis-isotope ratio mass spectrometry (EA-IRMS), gas chromatography-mass spectrometry (GC-MS), stereomicroscopic analysis and Scanning Electron Microscopy (SEM), as well as the analysis of absorbed lipids by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). This study provides the first evidence of ruminant dairy fats in Early Neolithic Limburg pottery, supporting the hypothesis that this pottery was produced and used by LBK farmers rather than hunter-gatherer populations. The first indigenous pottery of the Swifterbant culture was frequently used to process freshwater fish (often together with plant foods) and ruminant meat, although several of the studied vessels likely contained mixtures of resources which could also include porcine products. Ruminant dairy is nearly absent from this pottery. Similar results were obtained for pottery of the subsequent Michelsberg culture/Group of Spiere of the late 5th and early 4th millennium cal BC. The limited presence of ruminant dairy fats in this pottery contrasts with the findings for Middle Neolithic pottery from neighbouring regions, providing further evidence for the existence of regional variations in pottery use or culinary practices throughout prehistoric NW Europe. However, our current view of pottery use during the Mesolithic-Neolithic transition in northern Belgium might be biased by the difficulties in distinguishing between wild and domesticated ruminant adipose fats as well as in detecting plant foods through lipid residue analysis. [ABSTRACT FROM AUTHOR]

Copepods serve as a major link in marine food webs, bridging the energy transfer from primary producers to higher trophic levels. Oceanic warming is linked to reduced concentrations of essential fatty acids (FA) in phytoplankton, namely eicosapentaenoic acid (EPA, 20:5ω3) and docosahexaenoic acid (DHA, 22:6ω3), and it remains largely unknown if copepods have the capacity to endure. The calanoid Temora longicornis and the harpacticoid Platychelipus littoralis were chosen to analyse their FA and biosynthesis activity in response to a long-chain polyunsaturated FA (LC-PUFA) deficient diet (Dunaliella tertiolecta) along a temperature gradient. Copepods were fed D. tertiolecta labelled with the stable isotope carbon-13 (13C) to quantify carbon assimilation into their total FA and de novo EPA and DHA biosynthesis after 6 days incubated at 11, 14, 17, 20 and 23 °C. The calanoid had increased mortality with warming, whereas the harpacticoid exhibited high survival across the thermal gradient. After the incubation, P. littoralis assimilated minimal amounts of dietary carbon into its total FA in comparison to T. longicornis. T. longicornis depleted their field EPA and DHA stores more rapidly, whereas P. littoralis maintained its relative storage of EPA and DHA and absolute concentrations of DHA. T. longicornis displayed higher fractions of de novo EPA and DHA biosynthesis than P. littoralis at all temperatures, with the exception of DHA at 23 °C. Within our experimental incubation period both species were unable to meaningfully upgrade the LC-PUFA deficient algae to biosynthesize de novo EPA and DHA as a relevant source for higher trophic levels. [ABSTRACT FROM AUTHOR]

Background: Across the tropics, the share of secondary versus primary forests is strongly increasing. The high rate of biomass accumulation during this secondary succession relies on the availability of essential nutrients, such as nitrogen (N). Nitrogen primarily limits many young secondary forests in the tropics. However, recent studies have shown that forests of the Congo basin are subject to high inputs of atmospheric N deposition, potentially alleviating this N limitation in early succession. Methods: To address this hypothesis, we assessed the N status along a successional gradient of secondary forests in the Congo basin. In a set-up of 18 plots implemented along six successional stages, we quantified year-round N deposition, N leaching, N2O emission and the N flux of litterfall and fine root assimilation. Additionally, we determined the N content and C:N stoichiometry for canopy leaves, fine roots, and litter, as well as δ15N of canopy leaves. Results: We confirmed that these forests receive high amounts of atmospheric N deposition, with an increasing deposition as forest succession proceeds. Additionally, we noted lower C:N ratios, and higher N leaching losses, N2O emission, and foliar δ15N in older secondary forest (60 years). In contrast, higher foliar, litter and root C:N ratios, and lower foliar δ15N, N leaching, and N2O emission in young (< 20 years) secondary forest were observed. Conclusions: Altogether, we show that despite high N deposition, this early forest succession still shows conservative N cycling characteristics, which are likely indicating N limitation early on in secondary forest succession. As secondary succession advances, the N cycle gradually becomes more open. [ABSTRACT FROM AUTHOR]

The soil nitrogen (N) cycle in cold terrestrial ecosystems is slow and organically bound N is an important source of N for plants in these ecosystems. Many plant species can take up free amino acids from these infertile soils, either directly or indirectly via their mycorrhizal fungi. We hypothesized that plant community changes and local plant community differences will alter the soil free amino acid pool and composition; and that long-term warming could enhance this effect. To test this, we studied the composition of extractable free amino acids at five separate heath, meadow, and bog locations in subarctic and alpine Scandinavia, with long-term (13 to 24 years) warming manipulations. The plant communities all included a mixture of ecto-, ericoid-, and arbuscular mycorrhizal plant species. Vegetation dominated by grasses and forbs with arbuscular and non-mycorrhizal associations showed highest soil free amino acid content, distinguishing them from the sites dominated by shrubs with ecto- and ericoid-mycorrhizal associations. Warming increased shrub and decreased moss cover at two sites, and by using redundancy analysis, we found that altered soil free amino acid composition was related to this plant cover change. From this, we conclude that the mycorrhizal type is important in controlling soil N cycling and that expansion of shrubs with ectomycorrhiza (and to some extent ericoid mycorrhiza) can help retain N within the ecosystems by tightening the N cycle. [ABSTRACT FROM AUTHOR]

The occurrence and the treatment of potentially toxic metals in wastes are investigated by many studies, especially in territories exploited by industrial activities. Improper phosphogypsum waste storage is of serious environmental concern. The present work aimed to evaluate the potential of natural clay minerals from the Gabes area, southern Tunisia for sorption of several toxic metals (Zn, Cd, Cr, and As) that may leach from waste phosphogypsum. Clay materials are known by their versatility as adsorbents due to their low cost, great surface area, interchange capacity, and abundance in nature. The three clay samples collected in various locations in the Gabes district-Southern Tunisia were characterized by different techniques including X-ray fluorescence (XRF) and X-ray diffraction (XRD). The natural clays are mainly composed of alumina, iron, silica, calcium, and magnesium oxides. Chemical analysis of phosphogypsum waste indicated a high concentration of potentially toxic metals, particularly Cd, Cr, Zn, and As. Contents of the radioactive elements U and Thin contrast, were low not of environmental concern. Adsorption data showed that the studied three natural clay samples removed substantial amounts of metals (Zn, Cd, Cr, and As) from phosphogypsum waste. The removal efficiency followed pseudo-second-order kinetic model. These results suggest that the natural clays from Gabes area, Tunisia, turned out to be an effective natural adsorbent for capturing metals from phosphogypsum waste and can be effectively used for the treatment of contaminated wastewaters in the environment. [ABSTRACT FROM AUTHOR]

Central African tropical forests face increasing anthropogenic pressures, particularly in the form of deforestation and land-use conversion to agriculture. The long-term effects of this transformation of pristine forests to fallow-based agroecosystems and secondary forests on biogeochemical cycles that drive forest functioning are poorly understood. Here, we show that biomass burning on the African continent results in high phosphorus (P) deposition on an equatorial forest via fire-derived atmospheric emissions. Furthermore, we show that deposition loads increase with forest regrowth age, likely due to increasing canopy complexity, ranging from 0.4 kg P ha−1 yr−1 on agricultural fields to 3.1 kg P ha−1 yr−1 on old secondary forests. In forest systems, canopy wash-off of dry P deposition increases with rainfall amount, highlighting how tropical forest canopies act as dynamic reservoirs for enhanced addition of this essential plant nutrient. Overall, the observed P deposition load at the study site is substantial and demonstrates the importance of canopy trapping as a pathway for nutrient input into forest ecosystems. Nowhere is biomass burning more abundant than on the African continent, but the biogeochemical impacts on forests are poorly understood. Here the authors show that biomass burning leads to high phosphorus deposition in the Congo basin, which scales with forest age as a result of increasing canopy complexity. [ABSTRACT FROM AUTHOR]

It is uncertain how the predicted further rise of atmospheric carbon dioxide (CO2) concentration will affect plant nutrient availability in the future through indirect effects on the gross rates of nitrogen (N) mineralization (production of ammonium) and depolymerization (production of free amino acids) in soil. The response of soil nutrient availability to increasing atmospheric CO2 is particularly important for nutrient poor ecosystems. Within a FACE (Free-Air Carbon dioxide Enrichment) experiment in a native, nutrient poor Eucalyptus woodland (EucFACE) with low soil organic matter (≤ 3%), our results suggested there was no shortage of N. Despite this, microbial N use efficiency was high (c. 90%). The free amino acid (FAA) pool had a fast turnover time (4 h) compared to that of ammonium (NH4+) which was 11 h. Both NH4-N and FAA-N were important N pools; however, protein depolymerization rate was three times faster than gross N mineralization rates, indicating that organic N is directly important in the internal ecosystem N cycle. Hence, the depolymerization was the major provider of plant available N, while the gross N mineralization rate was the constraining factor for inorganic N. After two years of elevated CO2, no major effects on the pools and rates of the soil N cycle were found in spring (November) or at the end of summer (March). The limited response of N pools or N transformation rates to elevated CO2 suggest that N availability was not the limiting factor behind the lack of plant growth response to elevated CO2, previously observed at the site. [ABSTRACT FROM AUTHOR]

Aims: Disentangling direct and indirect effects of global change drivers on plant nitrogen (N) uptake in leaves is important for understanding species and community responses in a changing world. Methods: We created understorey herb communities on forest soils with and without recent agricultural history. We traced pulse additions of 15NH415NO3 within these mesocosms while applying two-level factorial treatments of N enrichment, warming and illumination. We modelled direct and indirect effects of treatments on leaf N content and 15N uptake in leaves. Results: Warming and illumination had three times larger direct negative effects on leaf N content per dry mass and percentage leaf N derived from label (Ndfl%) than their indirect negative effects via an increasing community cover. These results imply a tissue dilution of N with increasing growth, in response to environmental change directly and indirectly exacerbated by community cover. We additionally found that interspecific differences in Ndfl% correlated with a species' colonisation capacity and resource acquisition strategy. Conclusions: Global change can directly affect allocation of N into foliage, with simultaneous indirect effects via altered community properties that influence individual plant responses. Predicting the future of plant communities in a changing world requires accounting for such understudied pathways. [ABSTRACT FROM AUTHOR]

Aim: A growing number of studies show a discrepancy between the isotopic composition of xylem water and plant water sources. We tested the effect of arbuscular mycorrhizal fungi (AMF) on the isotopic composition of Acacia caven xylem water. As the most common plant-fungal association, AMF might explain this isotopic mismatch. Methods: Seedlings were grown with and without AMF and irrigated with the same water. After 120 days, stem and soil samples were collected and following cryogenic distillation, H and O isotopic composition of xylem and soil water, as well as irrigation water, was measured. Results: Xylem water of non-mycorrhizal seedlings was significantly depleted in 2H compared to soil water (differences up to −15.6‰). When AMF were present, the depletion was significantly higher and appeared for both H and O (differences up to −24.6‰ for δ2H and − 2.9‰ for δ18O between soil and xylem water). Conclusions: Results suggest that isotopic fractionation occurred during water uptake in this xerophytic species. To explain this, we propose an aquaporin-driven mechanism mediating water transport via transmembrane passage. Furthermore, we show for the first time, that AMF enhance the observed discrimination against heavy isotopes, probably by enforcing water passage through aquaporins. Given their ubiquity, AMF could question the fractionation-free assumption during root water uptake. [ABSTRACT FROM AUTHOR]

Rising carbon dioxide (CO) concentrations and temperatures are expected to stimulate plant productivity and ecosystem C sequestration, but these effects require a concurrent increase in N availability for plants. Plants might indirectly promote N availability as they release organic C into the soil (e.g., by root exudation) that can increase microbial soil organic matter (SOM) decomposition ('priming effect'), and possibly the enzymatic breakdown of N-rich polymers, such as proteins, into bio-available units ('N mining'). We tested the adjustment of protein depolymerization to changing soil C and N availability in a laboratory experiment. We added easily available C or N sources to six boreal forest soils, and determined soil organic C mineralization, gross protein depolymerization and gross ammonification rates (using N pool dilution assays), and potential extracellular enzyme activities after 1 week of incubation. Added C sources were C-labelled to distinguish substrate from soil derived C mineralization. Observed effects reflect short-term adaptations of non-symbiotic soil microorganisms to increased C or N availability. Although C input promoted microbial growth and N demand, we did not find indicators of increased N mobilization from SOM polymers, given that none of the soils showed a significant increase in protein depolymerization, and only one soil showed a significant increase in N-targeting enzymes. Instead, our findings suggest that microorganisms immobilized the already available N more efficiently, as indicated by decreased ammonification and inorganic N concentrations. Likewise, although N input stimulated ammonification, we found no significant effect on protein depolymerization. Although our findings do not rule out in general that higher plant-soil C allocation can promote microbial N mining, they suggest that such an effect can be counteracted, at least in the short term, by increased microbial N immobilization, further aggravating plant N limitation. [ABSTRACT FROM AUTHOR]

Benthic copepods (Harpacticoida) are key members of the meiofauna community, and potentially important conveyers of energy from primary producers to higher trophic levels. However, little is known on their capability for trophic upgrading of food quality (essential fatty acids). Therefore, Platychelipus littoralis copepods were subjected to famine (3 days) and subsequent refeeding (6 days) on high ( Thalassiosira weissflogii) and low ( Dunaliella tertiolecta) quality food at 4, 15 and 24 °C, and their resilience for recovery of structural and storage fatty acids was determined. Additionally, stable isotope probing of fatty acids gave insight into the copepods' ability to synthesize ARA (20:4ω6), EPA (20:5ω3) and DHA (22:6ω3) from low quality food under different temperatures. High intra-specific variability (among copepod replicates) in fatty acid composition and C enrichment was observed when copepods were exposed to heat (24 °C) and food quality stress, and operated therefore as an indicator of environmental stress. Synthesis of the essential fatty acids ARA, EPA and DHA from dietary precursors increased with temperature. However, despite the capability for synthesis, no fatty acid accumulation was observed, which suggested substantial fatty acid turnover, especially under heat stress. Moreover, synthesis rates were not sufficient to restore the ω3 pools and ensure survival, at least for the duration of the experiment. Therefore, the question rises whether copepods of this local P. littoralis population will be able to cope with the reduced dietary supply of essential ω3 fatty acids, as predicted under global warming, given that the physiological need for these essential compounds likely increases with temperature. [ABSTRACT FROM AUTHOR]

Purpose: Compound-specific stable isotope (CSSI) fingerprinting of sediment sources is a recently introduced tool to overcome some limitations of conventional approaches for sediment source apportionment. The technique uses the C CSSI signature of plant-derived fatty acids (δC-fatty acids) associated with soil minerals as a tracer. This paper provides methodological perspectives to advance the use of CSSI fingerprinting in combination with stable isotope mixing models (SIMMs) to apportion the relative contributions of different sediment sources (i.e. land uses) to sediments. Results and discussion: CSSI fingerprinting allows quantitative estimation of the relative contribution of sediment sources within a catchment at a spatio-temporal resolution, taking into account the following approaches. First, application of CSSI fingerprinting techniques to complex catchments presents particular challenges and calls for well-designed sampling strategies and data handling. Hereby, it is essential to balance the effort required for representative sample collection and analyses against the need to accurately quantify the variability within the system. Second, robustness of the CSSI approach depends on the specificity and conservativeness of the δC-FA fingerprint. Therefore, saturated long-chain (>20 carbon atoms) FAs, which are biosynthesised exclusively by higher plants and are more stable than the more commonly used short-chain FAs, should be used. Third, given that FA concentrations can vary largely between sources, concentration-dependent SIMMs that are also able to incorporate δC-FA variability should be standard operation procedures to correctly assess the contribution of sediment sources via SIMMs. Conclusions: This paper reflects on the use of δC-FAs in erosion studies and provides recommendations for its application. We strongly advise the use of saturated long-chain (>20 carbon atoms) FAs as tracers and concentration-dependent Bayesian SIMMs. We anticipate progress in CSSI sediment fingerprinting from two current developments: (i) development of hierarchical Bayesian SIMMs to better address catchment complexity and (ii) incorporation of dual isotope approaches ( δ C- and δ H-FA) to improve estimates of sediment sources. [ABSTRACT FROM AUTHOR]

The biotreatment of flue gases with algae cultures is a promising option to sequestrate CO, yet the emission of other greenhouse gases (GHG) from the cultures can hamper their environmental benefit. Quantitative data on the sequestration potential for CO and NO in relation to the direct production of CH and NO are urgently required. The present study assessed the flows of carbon (C) and nitrogen (N) through cultures of the green alga Dunaliella salina, supplied with biodiesel flue gas, by means of mass balancing. D. salina was grown in artificially lighted, field- (42-L bubble column reactor) and laboratory-scale cultures (23 °C, pH 7.5). In the bubble column reactor, algae grew with an average specific growth rate of 0.237 day under flue gas supplementation (6.3 % (v/v) CO, 1.2 ppmv NO), and CO was retained to 39 % in the system. The specific sequestration rate for CO was low, with 0.13 g CO L day. Cultures emitted up to 13.03 μg CH L day and 4261 μg NO L day. The moderate retention of NO-N was outweighed by emissions of NO-N, and total N in the system decreased by 15.48 % during the 9-day trial. Results suggest that GHG production was mainly the outcome of anaerobic microbial processes and their emission was lower in pre-sterilized cultures. Under the tested conditions, up to six times more CO equivalents were emitted during flue gas treatment. Therefore, the direct GHG emissions of algae culture systems, intended for flue gas treatment (i.e. open ponds) need to be reviewed critically. [ABSTRACT FROM AUTHOR]