Recycled Iron Phosphates: A New Phosphorus Fertilizer for Paddy Rice.

The potential of recycled iron phosphates (FePs), e.g., vivianites (Fe3(PO4)2·8H2O) and Fe(III)-rich phosphorus (P) adsorbent materials, as phosphorus fertilizer is limited by the strong interaction between Fe and P. In this study, the efficiency of FePs as P fertilizer was explored by applying them as granules or powder in flooded strongly P-fixing soils (acid and calcareous), thereby taking advantage of increased P release induced by reductive dissolution of P-bearing Fe(III) minerals. First, no P diffusion from granular FeP fertilizers into flooded soils was detectable by the diffusive gradient in thin films (DGT) technique and microfocused X-ray fluorescence (µ-XRF) analysis of thin soil sections, in contrast to detectable P diffusion away from granules of soluble triple superphosphate (TSP) fertilizer. On the contrary, powdered FePs demonstrated an excellent increase in extractable P (1 mM CaCl2) in a 120-day incubation experiment in flooded soils. Second, a pot experiment was performed with rice (Oryza sativa) grown in flooded acid and calcareous soils. The fertilizer value of FePs was remarkable when dosed as powder, as it was even up to 3-fold higher than TSP in the acid soil and similar to TSP in the calcareous soil. The beneficial effect of FeP over TSP in the acid soil is attributed to the slow release of P from FePs, which allows to partly overcome P fixation. The promising results of FePs as P fertilizer applied as powders in flooded soils debunk the generally accepted idea that FePs are poor sources of P while demonstrating the importance of the timing of FeP fertilizer application.

Cottage industry as a source of high exposure to lead: A biomonitoring study among people involved in manufacturing cookware from scrap metal.

In low-income countries, a widespread but poorly studied type of cottage industry consists of melting scrap metal for making cookware. We assessed the exposure to lead (Pb) among artisanal workers, and their families, involved in manufacturing cookware from scrap metal. In a cross-sectional survey, we compared artisanal cookware manufacturing foundries with carpentry workshops (negative controls) and car battery repair workshops (positive controls), all located in residential areas, in Lubumbashi (DR Congo). We collected surface dust in the workspaces, and blood and urine samples among workers, as well as residents living in the cookware workshops. Trace elements were quantified in the samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In surface dust, median Pb concentrations were higher in cookware foundries (347 mg/kg) than in carpentries (234 mg/kg) but lower than in battery repair workshops (22,000 mg/kg). In workers making the cookware (n = 24), geometric mean (GM) Pb blood cencentration was 118 µg/L [interquartile range (IQR) 78.4-204], i.e. nearly twice as high as among carpenters [60.2 µg/L (44.4-84.7), n = 33], and half the concentration of battery repair workers [255 µg/L (197-362), n = 23]. Resident children from the cookware foundries, had higher urinary Pb [6.2 µg/g creatinine (2.3-19.3), n = 6] than adults [2.3 (2.2-2.5), n = 3]. Our investigation confirms the high Pb hazard linked to car battery repair and reveals a high exposure to Pb among artisanal cookware manufacturers and their families, especially children, in residential areas of a city in a low-income country.

Internal loading of phosphorus in streams described by a Sediment-Water Exchange Model for Phosphorus (SWEMP): From lab to field scale.

The reaction of phosphorus (P) between sediments and water in streams strongly affects the surface water P concentrations. A new reactive transport model (SWEMP: Sediment-Water Exchange Model for Phosphorus) was developed to describe redox dependent P sorption in the sediment and vertical diffusive transport of solutes to the overlying stream. The model parameters were independently obtained to first predict P release in ten different sediment-water batch systems and in two flumes. Input parameters are the degree of P saturation of the sediment, its organic matter content, dissolved oxygen (DO) concentration and temperature. The dissolved P concentrations in the overlying waters ranged from 0.02 to 1.2 mg P L-1 in these systems and were correctly predicted by the model within, on average, a factor 1.3 (batch) or 1.1 (flume). The P flux from the sediment towards the overlying water increased with increasing sediment P:Fe ratio and respiration rates, and with decreasing DO and water pH. After validation of the model with experimental data, it was used to predict monthly P concentrations in Flemish rivers using the total P emission data, total discharge, average sediment properties and the monthly averaged water temperatures, DO concentrations and electric conductivity. The monthly average P concentrations oscillate annually between 0.24 and 0.73 mg P L-1 and predictions matched the long-term monitoring data within 10 % using only one adjustable parameter for the entire water system (N > 250,000). The model predicts that summer peaks in P are related to internal loading from the sediment under anoxic conditions rather than to emission-dilution effects, i.e. external input of P and/or its concentration at lower flow rates. This suggests that, surface water P concentrations can be lowered by enhanced DO in the water, the addition of Fe and Al rich binding agents to the sediments and by reducing P emissions.

Extrapolating Metal (Cu, Ni, Zn) Toxicity from Individuals to Populations Across Daphnia Species Using Mechanistic Models: The Roles of Uncertainty Propagation and Combined Physiological Modes of Action.

Mechanistic effect modeling is a promising tool to improve the ecological realism of environmental risk assessment. An open question for the mechanistic modeling of metal toxicity is whether the same physiological mode of action (PMoA) could be assumed for closely related species. The implications of various modeling choices, such as the use of parameter point estimates and assumption of simplistic toxicodynamic models, are largely unexplored. We conducted life-table experiments with Daphnia longispina, Daphnia magna, and Daphnia pulex exposed to the single metals Cu, Ni, and Zn, and calibrated toxicokinetic-toxicodynamic (TKTD) models based on dynamic energy budget theory. We developed TKTD models with single and combined PMoAs to compare their goodness-of-fit and predicted population-level sensitivity. We identified the PMoA reproduction efficiency as most probable in all species for Ni and Zn, but not for Cu, and found that combined-PMoA models predicted higher population-level sensitivity than single-PMoA models, which was related to the predicted individual-level sensitivity, rather than to mechanistic differences between models. Using point estimates of parameters, instead of sampling from the probability distributions of parameters, could also lead to differences in the predicted population-level sensitivity. According to model predictions, apical chronic endpoints (cumulative reproduction, survival) are conservative for single-metal population effects across metals and species. We conclude that the assumption of an identical PMoA for different species of Daphnia could be justified for Ni and Zn, but not for Cu. Single-PMoA models are more appropriate than combined-PMoA models from a model selection perspective, but propagation of the associated uncertainty should be considered. More accurate predictions of effects at low concentrations may nevertheless motivate the use of combined-PMoA models. Environ Toxicol Chem 2024;43:338-358. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Transplacental transfer of cobalt: Evidence from a study of mothers and their neonates in the African Copperbelt.

BACKGROUND: Transfer of the trace metal cobalt (Co) from mother to foetus has not been documented in populations with high environmental exposure to Co, as is the case in the African Copperbelt mining region. We analysed data obtained from 246 mother-infant pairs included (at delivery) in a previously published case-control study on birth defects, done in Lubumbashi (Democratic Republic of Congo) between March 1, 2013, and Feb 28, 2015. METHODS: Co was measured by Inductively Coupled Plasma Mass Spectrometry in maternal blood, maternal urine, umbilical cord blood and placental tissue, as available. RESULTS: The Co concentrations [geometric mean (GM) with interquartile range (IQR)] in maternal blood (GM 1.77 µg/L, IQR 1.07-2.93) and urine (GM 7.42 µg/g creatinine, IQR 4.41-11.0) were highly correlated (Spearman r = 0.71, n = 166; p < 0.001) and considerably higher than reference values determined for general populations elsewhere in the world. The concentrations of Co in umbilical cord blood (GM 2.41 µg/L) were higher (Wilcoxon test, p < 0.001) than in maternal blood (GM 1.37 µg/L), with a correlation between both values (Spearman r = 0.34; n = 127, p < 0.001). Co concentrations in placental tissue (geometric mean 0.02 µg/g wet weight) correlated with concentrations in maternal blood (Spearman r = 0.50, n = 86, p < 0.001) and in neonatal blood (Spearman r = 0.23, n = 83, p = 0.039). CONCLUSION: This first study of maternal and neonatal Co concentrations in the African Copperbelt provides strong evidence of a high transfer of Co from mother to foetus.

Metal Mixture Toxicity of Ni, Cu, and Zn in Freshwater Algal Communities and the Correlation of Single-Species Sensitivities Among Single Metals: A Comparative Analysis.

The effects assessment of metals is mainly based on data of single metals on single species, thereby not accounting for effects of metal mixtures or effects of species interactions. Both of these effects were tested in combination, thereby hypothesizing that the sensitivity of a community to synergistic mixture toxicity depends on the correlation of single-species sensitivities among the single metals. Single-metal and metal-mixture effects were tested in full concentration-response experiments (fixed ray of 1:1:3 and 5:1:13 mass ratio Ni:Cu:Zn) on eight single freshwater algal species and 14 algal communities of four species each. The mean correlation of single-species median effect concentrations among the single metals (Ni-Cu, Cu-Zn, and Zn-Ni) for all species in a community ( r ̅ ) ranged from -0.4 to 0.9 among the communities; most of these (12/14) were positive. Functional endpoints (total biomass) were overall less sensitive than structural endpoints (Bray-Curtis similarity index) for communities with positively correlated single-species sensitivities among the single metals ( r ̅ > 0.33 ), suggesting that such correlations indicate functional redundancy under metal-mixture stress. Antagonistic metal-mixture interactions were predominantly found in single species, whereas metal-mixture interactions were antagonistic and surprisingly synergistic for the communities, irrespective of the reference mixture model used (concentration addition or independent action). The mixture interactions close to the carrying capacity (day 7) of communities gradually shifted from antagonism to more noninteractions with increasing correlation of single-species sensitivities among the single metals. Overall, this suggests that functional redundancy under mixed-metal stress comes at the cost of reduced biodiversity and that synergisms can emerge at the community level without any synergisms on the single-species level. Environ Toxicol Chem 2023;42:2666-2683. © 2023 SETAC.

Monitoring cadmium concentrations in cacao: inter-laboratory variation and the effect of sample size on variability among ready-for-sale beans.

Since the implementation of new EU limits on cadmium (Cd) in cacao-derived products, reliable measurements of the Cd concentration in cacao samples have become even more important. This study was set up to analyse the robustness of the measured Cd concentrations in cacao as affected by sampling strategy and by the laboratory receiving these samples. Six different homogenised cacao liquor samples were sent to 25 laboratories, mainly located in Latin America. On average, only 76% of the laboratories reported acceptable results per sample using internationally accepted criteria. More unreliable data was obtained when Atomic Absorption Spectroscopy (AAS) rather than Inductively Coupled Plasma (ICP) instruments were used or where concentrations were outside the calibration range. Subsequently, four commercial lots in Ecuadorian warehouses were sampled to identify the variation among beans, bags and replicate chemical analyses of ground samples. Simulations indicate that a composite sample should be made from at least 10 bags on a pallet and at least 60 beans should be ground prior to analysis to obtain an acceptable CV below 15%. This study shows that current Cd analyses in cacao on the market are neither sufficiently accurate nor precise and that more control on laboratory certifications is needed for reliable screening of Cd in cacao.

Colloids facilitate cadmium and uranium transport in an undisturbed soil: A comparison of soil solution isolation methods.

Accurate data of cadmium (Cd) and uranium (U) leaching are needed in the context of identifying their mass balances in agricultural soils. There is some controversy related to sampling methods and the contribution of colloid facilitated transport. Here, leaching was measured in undisturbed unsaturated soils and the impact of colloids was measured with due attention to solution sampling protocols. Soils were sampled in an arable, pH neutral silty loam soil. The columns (n = 8) were irrigated and PTFE suction plates (1 µm pores) at the bottom ensured unsaturated flow. New here is that both percolates and associated suction plates were collected, the elements in the plates were recovered with acid digestion and used as a lower estimate of colloidal forms. The fraction of elements collected in the plates were 33 % (Cd) and 80 % (U) of the total mobility (=percolates + plates), illustrating colloidal transport. Composition of pore water extracted by soil centrifugation varied largely between initial and final samples and showed that colloids increased as a result of reduced solution calcium after leaching two pore volumes with low calcium water. Flow Field-Flow Fractionation (FIFFF) of the pore water and percolates revealed co-elution of U with colloidal organic matter, oxyhydroxides and clay, illustrating colloidal transport of U by these vectors. Colloidal transport of Cd was less pronounced and was dominated by organic matter. Soil extracts with 0.01 M CaCl2 have lower colloid concentration and consequently underestimate mobile U. In contrast, Cd concentrations in 0.01 M CaCl2 extracts exceed that of percolates due to chloride complexation and higher calcium, mobilizing Cd. Soil leaching experiments better indicate potential leaching losses than a single pore water composition because the former yields the time integrated data. Suction plates and/or bottom filters need to be analysed in leaching studies to account for metal transport by colloids.

Screening redox stability of iron rich by-products for effective phosphate immobilisation in freshwater sediments.

Iron (Fe) rich by-products can be added to lake or river sediments to immobilise phosphate (PO4) and lower eutrophication risks. These Fe materials differ in mineralogy and specific surface area, hence differing in PO4 sorption capacity and stability under reducing conditions. This study was set up to identify key properties of these amendments in their capacity to immobilise PO4 in sediments. Eleven Fe rich by-products, collected from drinking water treatment plants and acid mine drainage, were characterised. The PO4 adsorption to these by-products was first determined under aerobic conditions and the solid-liquid distribution coefficient KD for PO4 correlated strongly to oxalate extractable Fe content. A static sediment-water incubation test was subsequently used to evaluate the redox stability of these by-products. The reductive processes gradually released Fe to solution and more Fe was release from the amended than from the control sediments. The total Fe release to solution was positively related to ascorbate reducible Fe fractions in the by-products, suggesting that such fractions indicate potential loss of P retention capacity on the long term. The final PO4 concentration in the overlying water was 5.6 mg P L-1 in the control and was successfully lowered by factor 30-420 depending on the by-product. The factor by which solution PO4 was reduced in Fe treatments increased with increasing KD determined under aerobic conditions. This study suggests that efficient by-products to trap P in sediments are characterised by a high oxalate Fe content and a low reducible Fe fraction.

Effect of external and internal loading on source-sink phosphorus dynamics of river sediment amended with iron-rich glauconite sand.

Glauconite sands (GS) are abundantly available iron (Fe)-rich minerals that are efficient in lowering the release of phosphorus (P) from sediments to the overlying water. Many river sediments are, however, net sinks for P rather than sources and it is unclear if these GS minerals also enhance the P uptake from water. This is because the concentration of Fe(III) minerals at the sediment-water interface (SWI) depends on the redox potential that is affected by physicochemical processes. This study was set-up to investigate if a sediment amendment with GS can both lower P release from the sediment and enhance P uptake from the overlying water. The P fluxes across the SWI were compared between GS-amended (added at 10% weight fraction) and non-amended river sediment in static (incubation) and dynamic (flume) systems. The net P uptake was measured in response to a pulse external P loading (0.5-5 mg P L-1). Sodium glutamate was added to all treatments to simulate water with a high oxygen demand. Before the P pulse, the GS-amended sediments released significantly less P to the overlying water than the non-amended sediments in both static as dynamic systems. Spiking the water reverted the net P flux over the SWI only in the dynamic system, and the net P uptake in the sediment was factor two larger in GS-amended sediment compared to the non-amended sediment. This study showed that GS addition not only reduced internal P release, but also enhanced P uptake from the overlying water. However, the long-term efficiency in streams likely decreases over time due to saturation processes.

Quantitative clay mineralogy predicts radiocesium bioavailability to ryegrass grown on reconstituted soils.

Current radiocesium (137Cs) models to evaluate the risk of 137Cs transfer from soil to plants are based on the clay and exchangeable potassium (K) contents in soil. These models disregard the mineralogy of the clay fraction and are likely not capable of accurately predicting the 137Cs transfer factor (TF) in soils of contrasting parent rocks and weathering stages. The objectives of this study were to test that hypothesis and to identify whether quantitative information on mineralogy can improve the predictions. A pot cultivation experiment was set up with clay-sand mixtures in single and double clay doses that were fertilized, spiked with 137Cs and grown with ryegrass for 30 days. Four clays (illite, biotite, smectite and vermiculite) along with six deposits from clay-rich geological units were compared. The TF generally decreased with increasing clay dose for each of these ten different clay groups, however, the TF varied two orders of magnitude across clay groups and doses. The TF was highest for clays with little 137Cs specific sites such as bentonite and/or where the exchangeable K content was low compared to the other clays. The TF was well predicted from the soil solution 137Cs and K concentrations (R2 = 0.72 for log transformed TF), corroborating earlier findings in natural soils. The TF (log transformed) was statistically unrelated to total phyllosilicate content or 1:1 and 2:1:1 type phyllosilicate content while it significantly decreased with increasing 2:1 phyllosilicate content (R2 = 0.32). A multiple regression model with four different X-ray diffraction (XRD) based phyllosilicate groups yielded the strongest predictive power (R2 = 0.74). We conclude that XRD quantification is valuable for describing 137Cs bioavailability in plant substrates. These findings now await confirmation for natural soils.

The contribution of cacao consumption to the bioaccessible dietary cadmium exposure in the Belgian population.

Since 2019, EU limits apply to cadmium (Cd) concentrations in cacao-derived food products. The dietary risk assessment leading to that regulation used consumption surveys aggregated to a limited number of chocolate product categories and did not consider differences in Cd bioaccessibility. Here, the cacao-related dietary Cd exposure in the Belgian population was estimated with higher resolution and accounting for bioaccessibility. A food frequency questionnaire and a 24-h recall (N = 2055) were set up for the Belgian population, in combination with ICP-MS analysis of a large subset of cacao-containing products (N = 349). Both the average chocolate consumption (28 g day-1) and the relative contribution of chocolate to the total dietary Cd exposure (7-9%) were higher than previously estimated for the Belgian population, probably because of some selection bias towards chocolate consumers in the cohort. The Cd bioaccessibility in chocolate products was a factor 5 (cacao powder) and 2 (dark chocolate) lower compared to wheat flour, suggesting lower bioavailability in chocolate than in wheat, which is a main contributor to dietary Cd. This study suggests that Cd intake from cacao consumption has been underestimated because of hidden cacao in non-chocolate food categories but, in contrast, may have overestimated the true exposure because of lower bioavailability compared to the main foodstuffs contributing to Cd exposure.

Re-evaluation of the existing health-based guidance values for copper and exposure assessment from all sources.

Copper is an essential micronutrient and also a regulated product used in organic and in conventional farming pest management. Both deficiency and excessive exposure to copper can have adverse health effects. In this Scientific Opinion, the EFSA 2021 harmonised approach for establishing health-based guidance values (HBGVs) for substances that are regulated products and also nutrients was used to resolve the divergent existing HBGVs for copper. The tightly regulated homeostasis prevents toxicity manifestation in the short term, but the development of chronic copper toxicity is dependent on copper homeostasis and its tissue retention. Evidence from Wilson disease suggests that hepatic retention is indicative of potential future and possibly sudden onset of copper toxicity under conditions of continuous intake. Hence, emphasis was placed on copper retention as an early marker of potential adverse effects. The relationships between (a) chronic copper exposure and its retention in the body, particularly the liver, and (b) hepatic copper concentrations and evidence of toxicity were examined. The Scientific Committee (SC) concludes that no retention of copper is expected to occur with intake of 5 mg/day and established an Acceptable Daily Intake (ADI) of 0.07 mg/kg bw. A refined dietary exposure assessment was performed, assessing contribution from dietary and non-dietary sources. Background copper levels are a significant source of copper. The contribution of copper from its use as plant protection product (PPP), food and feed additives or fertilisers is negligible. The use of copper in fertilisers or PPPs contributes to copper accumulation in soil. Infant formula and follow-on formula are important contributors to dietary exposure of copper in infants and toddlers. Contribution from non-oral sources is negligible. Dietary exposure to total copper does not exceed the HBGV in adolescents, adults, elderly and the very elderly. Neither hepatic copper retention nor adverse effects are expected to occur from the estimated copper exposure in children due to higher nutrient requirements related to growth.

Revealing the pathways of cadmium uptake and translocation in cacao trees (Theobroma cacao L.): A 108Cd pulse-chase experiment.

The pathways through which cadmium (Cd) is taken up and loaded into cacao beans (nibs) are yet to be revealed. Previous work suggested that Cd loading into cacao nibs may occur via direct xylem uptake rather than phloem-mediated redistribution from the leaves. A stable isotope (108Cd) pulse-chase experiment was set up to identify the pathways of Cd loading into cacao nibs. The topsoil beneath two mature cacao trees in the field was enriched in 108Cd via surface irrigation with a spiked solution. The increase in 108Cd isotopic abundance (IA) in the plant tissues was followed up for 548 days after spiking. The 108Cd IA in the plant tissues increased from natural abundance (0.89 %) to 7.0 % (tree A) and 10.1 % (tree B) at equilibrium. The tracer was taken up in the plant tissues in the order immature leaves > mature leaves > nibs in both trees, while tracer uptake in flowers and cherelles was less consistent between the trees. Half of the equilibrium 108Cd IA was reached in the nibs at 191 days after spiking, significantly later than corresponding values for mature (151 days) and immature leaves (117 days). Pod maturation from flower stage takes about 6 months with most Cd entering the nibs at the last stage of development. The rather slow rise in the 108Cd IA in the nibs compared to the leaves hence suggests that Cd in cacao nibs likely originates from phloem-redistribution from the stem, branches or mature leaves and not from direct root-to-nib transport via the xylem.

Phosphorus immobilisation in sediment by using iron rich by-product as affected by water pH and sulphate concentrations.

Iron (Fe) rich by-product from drinking water treatment plants can be added to rivers and lakes to immobilise phosphorus (P) in sediment and lower eutrophication risks. This study was set up to investigate the P immobilisation efficiency of an Fe rich by-product as affected by the pH and sulphate (SO4) concentration in the overlying water. Both factors are known to inhibit long-term P immobilisation under anoxic conditions. A static sediment-water incubation was conducted at varying buffered water pH values (6, 7 and 8) and different initial SO4 concentrations (0-170 mg SO4 L-1) with or without Fe rich by-product amendment to the sediment. In the unamended sediment, the P release to the overlying water was highest, and up to 6 mg P L-1, at lowest water pH due to higher reductive dissolution of Fe(III) oxyhydroxides. The Fe rich by-product amendment to the sediment largely reduced P release from sediment by factors 50-160 depending on pH, with slightly lowest immobilisation at highest pH 8, likely because of pH dependent P sorption. The total sulphur (S) concentrations in the overlying water reduced during incubation. The P release in unamended sediments increased from 2.7 mg L-1 to 4.2 mg L-1 with higher initial SO4 concentrations, suggesting sulphide formation during incubation and FeS precipitation that facilitates release of P. However, no such SO4 effects were found where Fe rich by-product was applied that lowered P release to <0.1 mg L-1 illustrating high stability of immobilised P in amended sediments. This study suggests that Fe rich by-product is efficient for P immobilisation but that loss of Fe in low pH water may lower its long-term effect.

Phosphorus reference conditions in lowland streams: Survey in old forests and anaerobic sediment release.

The reference (pristine) concentrations of total dissolved phosphorus (TDP) in surface waters are difficult to define in lowland regions because of their high population density. Here, we estimated reference conditions of TDP from headwaters and their riverbed sediments (n = 140) in old forests. Surface waters and sediments were collected in the lowland region of Belgium as transects starting in 20 different old forests (before 1775; pristine) to up to 1.5 km outside the forest edge (disturbed). Sediment P concentrations in disturbed samples readily increased with increasing distance from the borders of old forests. The P mobilized from the sediments to the overlying water was also measured in laboratory incubations to mimic P release during seasonal redox cycles. The sediment respiration was larger in disturbed than in the reference sediments. Disturbed sediments released more P during anaerobic than aerobic incubations, while reference sediments did not show such a difference. The mean TDP in the reference surface water samples is 57 µg TDP L-1 [95 % confidence interval 41; 72], very close to the pre-industrial background previously estimated for the Scheldt river. The 90th percentile of the reference water is 137 [110; 180] µg TDP L-1. That P90 is just under the prevailing TP limit of 140 µg P L-1, illustrating that this limit is very close to the upper baseline of reference conditions. The P75, often proposed as the threshold for high ecological status, was 84 [55; 122] µg P L-1. This study showed that soil or sediments in old forests might serve to identify reference conditions. The well-established summer peaks of TDP in lowland rivers are unlikely to occur in pristine areas.

How can we possibly resolve the planet's nitrogen dilemma?

Nitrogen is the most crucial element in the production of nutritious feeds and foods. The production of reactive nitrogen by means of fossil fuel has thus far been able to guarantee the protein supply for the world population. Yet, the production and massive use of fertilizer nitrogen constitute a major threat in terms of environmental health and sustainability. It is crucial to promote consumer acceptance and awareness towards proteins produced by highly effective microorganisms, and their potential to replace proteins obtained with poor nitrogen efficiencies from plants and animals. The fact that reactive fertilizer nitrogen, produced by the Haber Bosch process, consumes a significant amount of fossil fuel worldwide is of concern. Moreover, recently, the prices of fossil fuels have increased the cost of reactive nitrogen by a factor of 3 to 5 times, while international policies are fostering the transition towards a more sustainable agro-ecology by reducing mineral fertilizers inputs and increasing organic farming. The combination of these pressures and challenges opens opportunities to use the reactive nitrogen nutrient more carefully. Time has come to effectively recover used nitrogen from secondary resources and to upgrade it to a legal status of fertilizer. Organic nitrogen is a slow-release fertilizer, it has a factor of 2.5 or higher economic value per unit nitrogen as fertilizer and thus adequate technologies to produce it, for instance by implementing photobiological processes, are promising. Finally, it appears wise to start the integration in our overall feed and food supply chains of the exceptional potential of biological nitrogen fixation. Nitrogen produced by the nitrogenase enzyme, either in the soil or in novel biotechnology reactor systems, deserves to have a 'renaissance' in the context of planetary governance in general and the increasing number of people who desire to be fed in a sustainable way in particular.

Incubation tests mimicking fermentation reveal that phytate breakdown is key to lower the cadmium concentrations in cacao nibs.

Earlier studies revealed that cadmium (Cd) concentrations in cacao nibs can decrease by a factor up to 1.3 during fermentation. Here, fermentation was mimicked by incubating beans at different temperatures, and acetic acid and ethanol concentrations in the incubation media. Nib Cd concentrations decreased during incubation by mobilisation in the nibs and subsequent outward migration to the testa and the incubation solution. This was most pronounced when high concentrations of acetic acid were combined with high temperature, while ethanol had no statistically significant effect. Incubation under typical fermentation conditions (45 °C and 20.0 g acetic acid L-1) reduced the nib Cd concentration by a factor 1.3. This factor increased to 1.6 under more extreme conditions, i.e. 65 °C and 40 g acetic acid L-1. The final nib Cd concentrations correlated well to nib phytate concentrations (R2 = 0.56), suggesting hydrolysis of phytate and mobilisation of the associated Cd2+.

From soil to cacao bean: Unravelling the pathways of cadmium translocation in a high Cd accumulating cultivar of Theobroma cacao L.

The research on strategies to reduce cadmium (Cd) accumulation in cacao beans is currently limited by a lack of understanding of the Cd transfer pathways within the cacao tree. Here, we elucidated the transfer of Cd from soil to the nib (seed) in a high Cd accumulating cacao cultivar. Here, we elucidated the transfer of Cd from soil to the nib (seed) in a high Cd accumulating cacao cultivar through Cd stable isotope fractionation, speciation (X-Ray Absorption Spectroscopy), and localization (Laser Ablation Inductively Coupled Plasma Mass Spectrometry). The plant Cd concentrations were 10-28 higher than the topsoil Cd concentrations and increased as placenta< nib< testa< pod husk< root< leaf< branch. The retention of Cd in the roots was low. Light Cd isotopes were retained in the roots whilst heavier Cd isotopes were transported to the shoots (Δ 114/110 Cd shoot-root = 0.27 ± 0.02 ‰ (weighted average ± standard deviation)). Leaf Cd isotopes were heavier than Cd in the branches (Δ 114/110 Cd IF3 leaves-branch = 0.18 ± 0.01 ‰), confirming typical trends observed in annual crops. Nibs and branches were statistically not distinguishable (Δ 114/110 Cd nib-branch = -0.08‰ ± 0.06 ‰), contrary to the leaves and nibs (Δ 114/110 Cd nib-IF3 leaves = -0.25‰ ± 0.05 ‰). These isotope fractionation patterns alluded to a more direct transfer from branches to nibs rather than from leaves to nibs. The largest fraction (57%) of total plant Cd was present in the branches where it was primarily bound to carboxyl-ligands (60-100%) and mainly localized in the phloem rays and phelloderm of the bark. Cadmium in the nibs was mainly bound to oxygen ligands (60-90%), with phytate as the most plausible ligand. The weight of evidence suggested that Cd was transferred like other nutrients from root to shoot and accumulated in the phloem rays and phelloderm of the branches to reduce the transfer to foliage. Finally, the data indicated that the main contribution of nib Cd was from the phloem tissues of the branch rather than from leaf remobilization. This study extended the limited knowledge on Cd accumulation in perennial, woody crops and revealed that the Cd pathways in cacao are markedly different than in annual crops.

Enhancing the phosphorus content of layered double hydroxide fertilizers by intercalating polymeric phosphate instead of orthophosphate: A feasibility study.

HYPOTHESIS: Layered double hydroxide (LDH) loaded with orthophosphate (PO4) are suggested as slow-release P fertilizers. However, PO4-LDHs have a low maximal P content, related to high charge HPO42-/PO43- anions occupying the anion exchange capacity (AEC) of LDHs. We postulate that the P content of LDHs can be enhanced by exchanging them with polymeric-P (i.e. trimetaphosphate, P3O9), which has a lower molar charge/P ratio than its monomer. EXPERIMENTS: Adsorption capacities were compared between PO4 and P3O9 for as-synthesized and calcined MgAl LDHs with Mg/Al ratio of 2, 3, or 4; the P-LDHs were characterized (XRD, FTIR). Dialysis and soil incubation experiments were performed with PO4-LDHs, P3O9-LDHs, and corresponding soluble fertilizers to compare their P release and P solubility (CaCl2 extract). FINDINGS: The P adsorption capacities were 1.25-1.60 fold larger for P3O9 compared to PO4, yet the high theoretical P contents with P3O9 were not achieved (incomplete loading, P3O9 depolymerization). P3O9-Mg3Al released polymeric-P whereas P3O9-Mg2Al released depolymerized PO4, and P release from P3O9-LDHs was slower than that of PO4-LDHs. With soil incubation, soluble P from P3O9-LDH was initially lower but later converged to that of PO4-LDH as result of continued hydrolysis, yet did not exceed that of the soluble P3O9 and PO4 fertilizers.