Search

The transport of ferrihydrite colloid (FHC) through porous media is influenced by anions (e.g., PO43-) and cations (e.g., Ca2+) in the aqueous environment. This study investigated the cotransport of FHC with P and P/Ca in saturated sand columns. The results showed that P adsorption enhanced FHC transport, whereas Ca loaded onto P-FHC retarded FHC transport. Phosphate adsorption provided a negative potential on the FHC, while Ca added to P-FHC led to electrostatic screening, compression of the electric double layer, and formation of Ca5(PO4)3OH followed by heteroaggregation at pH ≥ 6.0. The monodentate and bidentate P surface complexes coexisted, and Ca mainly formed a ternary complex with bidentate P (≡(FeO)2PO2Ca). The unprotonation bidentate P at the Stern 1-plane had a considerable negative potential at the Van der Waals molecular surface. Extending the potential effect to the outer layer of FHC, the potential at the Stern 2-plane and zeta potential exhibited a corresponding change, resulting in a change in FHC mobility, which was validated by comparison of experimental results, DFT calculations, and CD-MUSIC models. Our results highlighted the influence of P and Ca on FHC transport and elucidated their interaction mechanisms based on quantum chemistry and colloidal chemical interface reactions.

Sedimentary interfaces between contrasting hydrogeological facies in alluvial aquifers drive the development of biogeochemical interfaces that influence subsurface and surface water quality. Here, we calibrate a reactive transport model on a series of dual-domain column experiments, where centimeter-scale, low-permeability, organic-rich anoxic lenses are embedded in coarser-grained aquifer material. Simulations explicitly account for C, Fe, and S cycling at the interface between the lenses and the aquifer in water-saturated conditions. Our results highlight the role of fine-grained, organic-rich inclusions not only as sources or sinks for redox-sensitive species, but also as exporters of nutrients that stimulate downgradient biogeochemical cycling. By releasing large amounts of organic carbon into the surrounding aquifer, such lenses drive the development of proximal secondary reduction zones (“halos”), characterized by high microbial activity (e.g., sulfate reduction) and accumulation of reduced reaction products (e.g., iron sulfide). If similar secondary reduction zones develop within the hydraulically conductive domain of an aquifer, they would be highly susceptible to changes in hydrologic conditions, for instance oxygen pulses associated with seasonal snowmelt. Our results also emphasize the limitations of relying solely on aqueous species measurements to inform reactivity in systems where fast redox cycling and/or sizeable particulate transport may limit the signature of reactivity in the dissolved phase.

Microbial reduction of soluble hexavalent uranium (U(VI)) to sparingly soluble tetravalent uranium (U(IV)) has been explored as an in situ strategy to immobilize U. Organic ligands might pose a potential hindrance to the success of such remediation efforts. In the current study, a set of structurally diverse organicligands were shown to enhance the dissolution of crystalline uraninite (UO2) for a wide range of ligand concentrations under anoxic conditions at pH 7.0. Comparisons were made to ligandinduced U mobilization from noncrystalline U(IV). For both U phases, aqueous U concentrations remained low in the absence of organic ligands (500 times more U mobilization). This work shows the potential of numerous organic ligands present in the environment to mobilize both recalcitrant and labile U forms under anoxic conditions to hazardous levels and, in doing so, undermine the stability of immobilized U(IV) sources.

Nanotechnology may be used to design more performant copper agrochemicals. Assessing the benefits and risks of the novel nano-products requires a good understanding of their fate in soil relative to other forms of copper. This study compares nine forms of Cu including nano and conventional Cu-based formulations, as well as their salt or bulk equivalents. Readily available Cu was extracted with 0.01 M CaCl2 over a period of 29 days in three soils with contrasting properties. For eight out of nine formulations, available Cu decreased over time indicating that complexation of Cu with soil phases was the process determining the availability of Cu. Freshly suspended CuO nanoparticles were the only form where available Cu increased over time, indicating that dissolution was limiting availability. The complexation/dissolution kinetics were mainly determined by the soil pH, whereas both soil pH and OC% determined the equilibrium concentration of Cu in the soil solution, in line with results from equilibrium modelling. Overall, the fraction of readily available Cu was very low in all cases, reaching

We steered the soil microbiome via applications of organic residues (mix of cover crop residues, sewage sludge + compost, and digestate + compost) to enhance multiple ecosystem services in line with climate-smart agriculture. Our result highlights the potential to reduce greenhouse gases (GHG) emissions from agricultural soils by the application of specific organic amendments (especially digestate + compost). Unexpectedly, also the addition of mineral fertilizer in our mesocosms led to similar combined GHG emissions than one of the specific organic amendments. However, the application of organic amendments has the potential to increase soil C, which is not the case when using mineral fertilizer. While GHG emissions from cover crop residues were significantly higher compared to mineral fertilizer and the other organic amendments, crop growth was promoted. Furthermore, all organic amendments induced a shift in the diversity and abundances of key microbial groups. We show that organic amendments have the potential to not only lower GHG emissions by modifying the microbial community abundance and composition, but also favour crop growth-promoting microorganisms. This modulation of the microbial community by organic amendments bears the potential to turn soils into more climate-smart soils in comparison to the more conventional use of mineral fertilizers.

The combination of biochar (BC) and iron minerals improves their pollutant adsorption capacity. However, little is known about the reactivity of BC-iron mineral composites regarding their interaction and change in the pore structure. In this study, the mechanism of cadmium (Cd) adsorption by BC-iron oxide composites, such as BC combined with ferrihydrite (FH) or goethite (GT), was explored. The synergistic effect of the BC-FH composite significantly improved its Cd adsorption capacity. The adsorption efficiencies of BC-FH and BC-GT increased by 15.0% and 10.8%, respectively, compared with that of uncombined BC, FH, and GT. The strong Cd adsorption by BC-FH was attributed to stable interactions and stereoscopic pore filling between BC and FH. The scanning electron microscopy results showed that FH particles entered the BC pores, whereas GT particles were loaded onto the BC surface. FTIR spectroscopy showed that GT covered a larger area of the BC surface than FH. After loading FH and GT, BC porosities decreased by 9.3% and 4.1%, respectively. Quantum chemical calculations and independent gradient mode analysis showed that van der Waals interactions, H-bonds, and covalent-like interactions maintained stability between iron minerals and BC. Additionally, humic acid increased the agglomeration of iron oxides and formed larger particles, causing additional aggregates to load onto the BC surface instead of entering the BC pores. Our results provide theoretical support to reveal the interfacial behavior of BC-iron mineral composites in soil and provide a reference for field applications of these materials for pollution control and environmental remediation.

Adsorption and transport of levofloxacin (LEV) and ofloxacin (OFL) enantiomers in a matrix containing goethite and natural organic matter (NOM) were investigated using batch and column experiments. In batch studies, competition and enantioselectivity were observed in the adsorption of LEV and OFL. Enantioselectivity upon adsorption was investigated by comparing changes in the enantiomer fraction (EF) (the ratio of LEV to the sum of LEV and OFL remaining in the solution) after and before adsorption. At pH < 7, there was hardly any selectivity in adsorption of OFL and LEV to goethite. At pH > 7, OFL showed a stronger adsorption than LEV to goethite, and this preference remained when NOM samples of Leonardite humic acid (LHA) and Elliott Soil fulvic acid (ESFA) were added. However, when Suwannee River NOM (SRNOM) was added, the preference was reversed, and LEV was adsorbed more strongly. In single systems, the presence of different types of NOM increased adsorption of LEV and OFL, especially LEV. In column studies, preloaded NOM decreased the transport of LEV and OFL through goethite-coated sand. The EF values in the effluent increased with retention time and reached the largest values (0.59–0.72) at around 1.5 pore volume (PV), and then decreased again, reaching a stable value at 5.0–30.0 PV. Both batch and column experiments showed that, fractionation of LEV and OFL occurred during adsorption and transport in the presence of NOM-goethite complexes, which would eventually affect their environmental fate

Atmospheric deposition is an essential cadmium (Cd) pollution source in agricultural ecosystems, entering crops via roots and leaves. In this study, atmospherically deposited Cd was simulated using cadmium sulfide nanoparticles (CdSN), and chili (Capsicum frutescens L.) was used to conduct a comparative foliar and root experiment. Root and foliar uptake significantly increased the Cd content of chili tissues as well as the subcellular Cd content. Scanning electron microscopy and high-resolution secondary ion mass spectrometry showed that Cd that entered the leaves via stomata was fixed in leaf cells, and the rest was mainly through phloem transport to the other organs. In leaf, stem, and root cell walls, Cd signal intensities were 47.4%, 72.2%, and 90.0%, respectively. Foliar Cd uptake significantly downregulated purine metabolism in leaves, whereas root Cd uptake inhibited stilbenoid, diarylheptanoid, and gingerol biosynthesis in roots. Root uptake contributed 90.4% Cd in fruits under simultaneous root and foliar uptake conditions attributed to xylem and phloem involvement in Cd translocation. Moreover, root uptake had a more significant effect on fruit metabolic pathways than foliar uptake. These findings are critical for choosing pollution control technologies and ensuring food security.

Knowledge of how arsenic (As) partitions among various phases in Fe-rich sulfidic environments is critical for understanding the fate and mobility of As in such environments. We studied the reaction of arsenite and arsenate sorbed on ferrihydrite nanoparticle surfaces with dissolved sulfide at varying S/Fe ratios (0.1–2.0) to understand the fate and transformation mechanism of As during sulfidation of ferrihydrite. By using aqueous As speciation analysis by IC-ICP-MS and solid-phase As speciation analysis by synchrotron-based X-ray absorption spectroscopy (XAS), we were able to discern the mechanism and pathways of As partitioning and thio-arsenic species formation. Our results provide a mechanistic understanding of the fate and transformation of arsenic during the codiagenesis of As, Fe, and S in reducing environments. Our aqueous-phase As speciation data, combined with solid-phase speciation data, indicate that sulfidation of As-sorbed ferrihydrite nanoparticles results in their transformation to trithioarsenate and arsenite, independent of the initial arsenic species used. The nature and extent of transformation and the thioarsenate species formed were controlled by S/Fe ratios in our experiments. However, arsenate was reduced to arsenite before transformation to trithioarsenate.

Phosphorus (P) is essential for plant growth, but most of the P in soils is not available for plant uptake as it binds strongly to mineral soil constituents. Additionally, the use of P in agriculture is challenged by both the current increase of the world population as well as a changing human diet towards more consumption of animal products. This results in a growing demand for food and P. Furthermore, the reserves of phosphate rock as source of mineral P fertiliser are declining, while areas that have historically received excessive P additions face environmental risks that are related to chronic dissolved P losses from legacy P soils to ground- and surface waters. These challenges associated with agricultural P use enforce us to increase productivity while using mineral P fertiliser in a more sustainable manner. Sustainable agricultural intensification will require adequate P fertiliser inputs, overcoming global P imbalances and finding ways to improve the utilisation of P already present in soil. This last strategy requires finding new ways to access soil P pools that are less available to plants. Exploring the role of earthworms in sustaining optimal P acquisition for plants can therefore contribute to solving the P challenges we are currently facing. In this thesis, I explored the role of earthworm-enhanced P-availability for improving soil P utilisation. My research primarily focussed on the effect of earthworms in grassland systems from the Netherlands, as grasslands are important to global food production, and can sustain large earthworm populations.The main objective of my thesis was to elucidate the effect of earthworms on plant-available P in soil and P uptake by grass, and to explore its potential to increase the sustainability of P nutrition of grass. The specific research objectives were (1) to assess the effect of different earthworm species on plant-available P and relate this to a) physico-chemical soil properties and b) earthworm ecology; (2) to determine the controlling mechanisms of earthworm-enhanced P-availability and quantify the relative importance of all contributing mechanisms; (3) to assess the effect of earthworm diversity on plant-available P; and (4) to evaluate if the effect of earthworms on plant-available P results in an increased grass P uptake and biomass production under realistic field conditions.My results showed that while all investigated earthworm species increased the total pool of reversibly adsorbed P, a large variation exists in the ability of earthworm species to alter the extent to which P is present in readily plant-available forms. This variation was not related to classical earthworm ecological classification, and species from the same functional group showed large variation in cast properties like pH and dissolved organic carbon as measured in water extracts. In turn, this variation could be linked to the existing variation in ortho-P solubility measured in the same extracts. It was therefore concluded that multiple pathways contributed to earthworm-enhanced P-availability.These multiple pathways were quantified further, and their relative importance was assessed. The probe-ion method, which derives the reactive surface area (RSA) of a soil, in combination with surface complexation modelling revealed a so far unconsidered mechanism: the decrease of the RSA of metal-(hydr)oxides in casts by particle growth, resulting in a decrease of the surface area that is available for P adsorption. The contribution of the controlling mechanisms of earthworm-enhanced P-availability in earthworm casts consists of: a) a relatively small effect of the increase of pH in casts; b) a major contribution of P addition through stimulated mineralisation inside the earthworm gut; c) a potentially major effect of a decrease in the RSA of casts by particle growth which is catalysed by the formation of Fe2+ during the reducing conditions caused by mineralisation; and d) a decrease in the competition between natural organic matter and P for binding sites on metal-(hydr)oxides in casts compared to the bulk soil. The reduction of the RSA was only observed for Fe-(hydr)oxide-dominated soils, whereas it was absent or minor in Al-(hydr)oxide-dominated soils. This demonstrated that soil mineralogy influences earthworm-enhanced P-availability and suggests that earthworms have the largest potential to improve the sustainability of P use in Fe-(hydr)oxide-dominated soils.All controlling mechanisms of earthworm-enhanced P-availability are directly or indirectly related to the capacity of an earthworm to mineralise the organic material it ingests. The potential activity of phosphatase enzymes that catalyse the mineralisation process of monoester P compounds was considerably increased by earthworms in the order casts>burrows>bulk soil. Phosphatase activity varied among earthworm species, and correlated with the P content of grass shoots, suggesting a direct earthworm-induced effect on grass P uptake through mineralisation of organic P.My mesocosm field experiment to the effect of earthworm diversity on grass biomass production and P uptake did not show an effect of a larger number of earthworm species on P uptake at the end of the experiment. However, using a multiple linear regression model on established communities, A. longa and L. terrestris were identified as keystone species to increase grass P uptake and biomass production. Furthermore, this study showed that the effect of earthworms on grass P uptake was not only present under controlled greenhouse conditions but can also be observed at the larger scale of more realistic field conditions.This research concludes that earthworm-enhanced P-availability has potential to contribute to a more sustainable P nutrition for agricultural grasslands in (the future of) the Netherlands. However, the challenges associated with agricultural P use are likely too large to be solved by a single approach. A combination of several approaches is needed by agriculture to provide an adequate P nutrition to grass on low agronomic P-status soils. My research shows that stimulating earthworm populations to increase the utilisation of P in soil could be one of those approaches. Future research should focus on assessing the effect of earthworm-enhanced P-availability on a global scale and its contribution to the utilisation of soil P over longer periods of time. Furthermore, future research should particularly focus on combining earthworms with other approaches that aim to increase P uptake from soils with a low P-status.&nbsp

Calcium (Ca) and magnesium (Mg) are the most abundant alkaline-earth metal ions in nature, and their interaction with ferrihydrite (Fh) affects the geochemical cycling of relevant ions, including phosphate (PO4). The interfacial interactions of Ca and Mg (M2+) with PO4 have not been analyzed yet for freshly precipitated Fh. Here, we studied experimentally this interaction in binary M2+-PO4 systems over a wide range of pH, M2+/PO4 ratios, and ion loadings. The primary adsorption data were scaled to the surface area of Fh using a recent ion-probing methodology that accounts for the size-dependent chemical composition of this nanomaterial (FeO1.4(OH)0.2·nH2O). The results have been interpreted with the charge distribution (CD) model, combined with a state-of-the-art structural surface model for Fh. The CD coefficients have been derived independently using MO/DFT/B3LYP/6-31+G** optimized geometries. M2+ and PO4 mutually enhance their adsorption to Fh. This synergy results from the combined effect of ternary surface complex formation and increased electrostatic interactions. The type of ternary complex formed (anion- vs cation-bridged) depends on the relative binding affinities of the co-adsorbing ions. For our Ca-PO4 systems, modeling suggests the formation of two anion-bridged ternary complexes, i.e., ≡(FeO)2PO2Ca and ≡FeOPO3Ca. The latter is most prominently present, leading to a relative increase in the fraction of monodentate PO4 complexes. In Mg-PO4 systems, only the formation of the ternary ≡FeOPO3Mg complex has been resolved. In the absence of Ca, the pH dependency of PO4 adsorption is stronger for Fh than for goethite, but this difference is largely, although not entirely, compensated in the presence of Ca. This study enables the use of Fh as a proxy for the natural oxide fraction, which will contribute to improved understanding of the mutual interactions of PO4 and M2+ in natural systems. Universidad de Costa Rica/[]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro de Investigaciones Agronómicas (CIA)

Hematite is ubiquitous in nature and holds great promise for a wide variety of applications in many frontiers of environmental issues such as heavy metal remediation in environment. Over the past decades, numerous efforts have been made to control and tailor the crystal structures of hematite to improve its adsorption performance for heavy metal ions (HMIs). It is now well established that the adsorption behavior of hematite nanocrystals is strongly affected by their particle sizes, crystal facet contributions, and defective structures. This review examined the size- and facet-dependent hematite, as well as the defective hematite according to their fabrication methods and growth mechanisms. Furthermore, the adsorption performance of various hematite particles for HMIs were introduced and compared to clarify the structure-active relationships of hematite. We also overviewed the advances in charge distribution (CD)-multisite complexation (MUSIC) modeling studies about the HMIs adsorption at the hematite-water interface and the binding parameters. The Present review systematically describes how the formation conditions impact the structural and surface properties of hematite particles, thereby providing new strategies for enhancing the performance of hematite for environmental remediation.

We steered the soil microbiome via applications of organic residues (mix of cover crop residues, sewage sludge + compost, and digestate + compost) to enhance multiple ecosystem services in line with climate-smart agriculture. Our result highlights the potential to reduce greenhouse gases (GHG) emissions from agricultural soils by the application of specific organic amendments (especially digestate + compost). Unexpectedly, also the addition of mineral fertilizer in our mesocosms led to similar combined GHG emissions than one of the specific organic amendments. However, the application of organic amendments has the potential to increase soil C, which is not the case when using mineral fertilizer. While GHG emissions from cover crop residues were significantly higher compared to mineral fertilizer and the other organic amendments, crop growth was promoted. Furthermore, all organic amendments induced a shift in the diversity and abundances of key microbial groups. We show that organic amendments have the potential to not only lower GHG emissions by modifying the microbial community abundance and composition, but also favour crop growth-promoting microorganisms. This modulation of the microbial community by organic amendments bears the potential to turn soils into more climate-smart soils in comparison to the more conventional use of mineral fertilizers.

We screened different organic amendments as single application or in combination to observe their influence on their GWP as well as on plant yield in a mesocosm experiment with two agricultural soils. Additionally, we screened changes occurring in microorganisms through the application of organic amendments.

It is generally assumed that the dependence of conventional agriculture on artificial fertilizers and pesticides strongly impacts the environment, while organic agriculture relying more on microbial functioning may mitigate these impacts. However, it is not well known how microbial diversity and community composition change in conventionally managed farmers’ fields that are converted to organic management. Here, we sequenced bacterial and fungal communities of 34 organic fields on sand and marine clay soils in a time series (chronosequence) covering 25 years of conversion. Nearby conventional fields were used as references. We found that community composition of bacteria and fungi differed between organic and conventionally managed fields. In the organic fields, fungal diversity increased with time since conversion. However, this effect disappeared when the conventional paired fields were included. There was a relationship between pH and soil organic matter content and the diversity and community composition of bacteria and fungi. In marine clay soils, when time since organic management increased, fungal communities in organic fields became more dissimilar to those in conventional fields. We conclude that conversion to organic management in these Dutch farmers’ fields did not increase microbial community diversity. Instead, we observed that in organic fields in marine clay when time since conversion increased soil fungal community composition became progressively dissimilar from that in conventional fields. Our results also showed that the paired sampling approach of organic and conventional fields was essential in order to control for environmental variation that was otherwise unaccounted for.

Data belonging to methodological comparison of organic carbon methods to quantify organic carbon in particulate (POM) and mineral-associated (MAOM) fractions in calcaerous soils.

Purpose Large parts of the Amazon rainforest grow on weathered soils depleted in phosphorus and rock-derived cations. We tested the hypothesis that in this ecosystem, fine roots stimulate decomposition and nutrient release from leaf litter biochemically by releasing enzymes, and by exuding labile carbon stimulating microbial decomposers. Methods We monitored leaf litter decomposition in a Central Amazon tropical rainforest, where fine roots were either present or excluded, over 188 days and added labile carbon substrates (glucose and citric acid) in a fully factorial design. We tracked litter mass loss, remaining carbon, nitrogen, phosphorus and cation concentrations, extracellular enzyme activity and microbial carbon and nutrient concentrations. Results Fine root presence did not affect litter mass loss but significantly increased the loss of phosphorus and cations from leaf litter. In the presence of fine roots, acid phosphatase activity was 43.2% higher, while neither microbial stoichiometry, nor extracellular enzyme activities targeting carbon- and nitrogen-containing compounds changed. Glucose additions increased phosphorus loss from litter when fine roots were present, and enhanced phosphatase activity in root exclusions. Citric acid additions reduced litter mass loss, microbial biomass nitrogen and phosphorus, regardless of fine root presence or exclusion. Conclusions We conclude that plant roots release significant amounts of acid phosphatases into the litter layer and mobilize phosphorus without affecting litter mass loss. Our results further indicate that added labile carbon inputs (i.e. glucose) can stimulate acid phosphatase production by microbial decomposers, highlighting the potential importance of plant-microbial feedbacks in tropical forest ecosystems.

Atmospherically deposited cadmium (Cd) may accumulate in plants through foliar uptake; however, the foliar uptake, accumulation, and distribution processes of Cd are still under discussion. Atmospherically deposited Cd was simulated using cadmium sulfide (CdS) with various particle sizes and solubility. Water spinach (Ipomoea aquatica Forsk, WS) and pak choi (Brassica chinensis L., PC) leaves were treated with suspensions of CdS nanoparticles (CdSN), which entered the leaves via the stomata. Cd concentrations of WS and PC leaves treated with 125 mg L−1 CdSN reached up to 39.8 and 11.0 mg kg−1, respectively, which are higher than the critical leaf concentration for toxicity. Slight changes were observed in fresh biomass, photosynthetic parameters, lipid peroxidation, and mineral nutrient uptake. Exposure concentration, rather than particle size or solubility, regulated the foliar uptake and accumulation of Cd. Subcellular and the high-resolution secondary ion mass spectrometry (NanoSIMS) results revealed that Cd was majorly stored in the soluble fraction and cell walls, which is an important Cd detoxification mechanism in leaves. The potential health risks associated with consuming CdS-containing vegetables were highlighted. These findings facilitate a better understanding of the fate of atmospheric Cd in plants, which is critical in ensuring food security.

Sustainability of agricultural systems is at stake, as phosphorus (P) is a non-renewable resource while its global reserves are limited. Stimulating earthworm activity can be a technology to increase the level of readily plant-available phosphate (PO$_4$). However, conclusive evidence on the mechanisms underlying an earthworm-enhanced PO$_4$ solubility is yet missing. This study aimed to reveal possibly overlooked pathways by which earthworms affect PO$_4$ solubility, and quantify the relative importance of all contributing mechanisms. Therefore, we set up a greenhouse pot experiment in which we investigated the large increase in water-extractable PO$_4$ in casts of three earthworm species (Lumbricus rubellus, Aporrectodea caliginosa, Lumbricus terrestris) in soils with either predominantly Fe- or Al-(hydr)oxides. Oxalate-extractable PO$_4$ was increased in earthworm casts compared to bulk soil which can be attributed to the mineralisation of natural organic matter (NOM). Surface complexation modelling was used to elucidate the mechanisms that control earthworm-enhanced PO$_4$ solubility. The results of our modelling showed that the increase in pH in earthworm casts relative to bulk soil affects PO$_4$ solubility only to a minor extent. Besides NOM mineralisation, two major mechanisms contributing to earthworm-enhanced PO$_4$ solubility are (i) a decrease in the reactive surface area (RSA) of the metal-(hydr)oxide fraction; and (ii) a decrease in the competition between NOM and PO$_4$ for binding sites of the metal-(hydr)oxides. As the newly discovered decrease of the RSA was only found for Fe-(hydr)oxide-dominated soils, earthworms have the largest potential to enhance PO$_4$ solubility in those soils.

Soil microorganisms are biological factors involved in the farmland environment. The factors that shape soil microbial communities and how these are influenced by geographic location, planting pattern (open-field or greenhouse), and soil organic pollutants (phthalate esters, PAEs) remain poorly understood at large scales. Using 16 S rRNA gene and ITS sequencing, we characterized the soil microbiota in open-field and greenhouse soils in Hebei Province, China, and correlated their structure and composition to geographic location, planting pattern and PAEs. Compared with geographic location, planting pattern is more decisive for shaping soil microbes and has more significant effects on bacteria, and the effects are shaped by the number and types of core OTUs. PAEs participated in the shaping of soil microbial communities by altering the relative abundances of dominant microorganisms in the two planting patterns, and the effects of PAEs with high Kow were more significant. PAEs have a greater impact on bacteria than fungi in both planting patterns. Bacteria in the greenhouse soil were sensitive to the 9 kinds of PAEs detected, however in the open-field samples, mainly responded to PAEs with high Kow and rarely respond to PAEs with low Kow. DEHP and DBP, as two monomers with the highest concentration, have significant effects on dominant genera of microorganisms under both planting patterns, with inhibiting effect on bacteria and significantly promotion on fungi. Our study clarified the factors that have a substantial impact on soil microorganisms at the provincial scale and the mechanisms involved in shaping soil microbial community structure, as well as the significant impact of PAEs on soil microbial dominant microorganisms.

Knowledge on organic matter (OM) concentration and composition is of major importance for predicting Zn speciation and bioavailability in soils, especially for low-Zn soils. However, comprehensive knowledge on the effect of soil-like organic amendments such as compost on metal speciation is limited. For the first time, multisurface modeling is applied on compost to study the effect of solid and dissolved OM composition on the speciation of reactive Zn as influenced by conditions applied in frequently used extractions to estimate Zn bioavailability. First, compost OM composition was determined by fractionation in operationally defined humic, fulvic, and hydrophilic acid pools under various extraction conditions, and subsequently, Zn speciation was modeled using the generic non-ideal competitive adsorption-Donnan (NICA-Donnan) model in addition to adsorption to hydrous ferric oxide (HFO) and clay. The results show a strong effect of extraction conditions on OM concentration and composition and related dissolved Zn speciation. Model predictions show that Zn in solution is mainly bound to dissolved humic acids. Analysis of deviations between measured and modeled Zn concentrations reveal specific limitations of the current generic model parameters, particularly with regard to Zn binding to OM at low concentrations and Ca-Zn competition, that is, typical conditions that occur in low-Zn soils.

Among natural organic matter (NOM), oxyanions and metal (hydr)oxides, a complicated interaction exists in natural aquatic and terrestrial systems and in waste waters. Effects of seven types of NOM (four humic acids (HA), three fulvic acids (FA)) that vary in properties on the adsorption of oxyanions, including phosphate, arsenate and arsenite, at goethite-water interface were quantitatively studied. Results show that the adsorption of oxyanions to goethite is decreased by the presence of NOM, especially for phosphate and arsenate at low pH. In general, the effects of the three FA are similar, which are more effective than HA in reducing oxyanion adsorption at low pH (

The application of herbicide fomesafen plays a crucial role in ensuring global soybean productivity in modern agriculture, but it results in both adverse effects on soil ecosystems and phytotoxicity to succeeding crops. Soil pollution due to herbicides has raised much concern worldwide. However, there has been little investigations concerning their effects on soil fauna, especially on the gut microbial communities of earthworms. In this study, the soil endogeic earthworm Pheretima guillelmi was incubated for 20 days in natural and fomesafen-polluted soils to investigate the effects of the herbicide on gut bacterial microbiota and the earthworm's physiological indices, including energy resource (protein) and antioxidant enzyme (superoxide dismutase, SOD) of earthworms in the soil ecosystem. A significantly different and smaller microbial community was presented in the earthworm's gut compared with the cast and the surrounding soil, with exposure to fomesafen further reducing the bacterial diversity and altering the gut community composition. This was observed as significant changes in the relative abundance of the phyla Actinobacteria, Firmicutes, and Proteobacteria as well as the genera Bacillus, Microvirga, Blastococcus, Nocardioides, and Gaiella. Moreover, exposure to fomesafen reduced earthworms' energy resources and activated the antioxidant system, with both effects being significantly correlated with the gut microbial diversity. These findings unravel the fact that exposure to the herbicide fomesafen may affect non-target soil fauna via changes in their microbiota and physiological indices, thereby contributing new knowledge regarding the adverse impacts of fomesafen on the terrestrial ecosystem.

Arsenic (As) and cadmium (Cd) are unnecessary metal(loids) toxic at high concentration to plants and humans, hence lessening their rice grain accumulation is crucial for food security and human healthiness. Charred eggshell (EB), corncob biochar (CB), and eggshell-corncob biochar (ECB) were produced and amended to As and Cd co-polluted paddy soil at 1% and 2% application rates to alleviate the metal(loids) contents in rice grains using pot experiments. All the amendments increased paddy yields at 1%, while EB at 2% significantly reduced the yields compared to untreated control. The resulting yield loss in 2%EB was from the combined effects of its high CaCO3 supplementation, and the increment of rhizosphere soil pH which could insolubilize plant nutrients. The amendments were inefficient in decreasing rice grain As (AsGrain), but all the treatments significantly reduced the rice grain Cd (CdGrain) at both 1% (44.4–77.1%) and 2% (79.8–91.5%) application rates compared to that of control. Regression analysis for contribution weights of control factors revealed that rhizosphere soil Eh and pH were vital influential factors regulating the AsGrain, whereas porewater Cd was main factor controlling CdGrain accumulation. These investigations indicated that the Ca-enriched eggshell-corncob biochar even at high application rate (i.e., 2%ECB) could be a potential tactic for grain accumulation remediation of the cationic pollutant (i.e., Cd) from the paddy soil to rice grain scheme with concurrent increase in rice yields.

An in-depth knowledge of pyrolytic kinetics is vital for understanding the thermal decomposition process. Numerous experimental studies have investigated the kinetic performance of the pyrolysis of different raw materials. An accurate prediction of pyrolysis kinetics could substantially reduce the efforts of researchers and decrease the cost of experiments. In this work, a model to predict the mean values of model-free activation energies of pyrolysis for five types of feedstocks was successfully constructed using the random forest machine learning method. The coefficient of determination of the fitting result reached a value as high as 0.9964, which indicates significant potential for making a quick initial pyrolytic kinetic estimation using machine learning methods. Specifically, from the results of a partial dependence analysis of the lignocellulose-type feedstock, the atomic ratios of H/C and O/C were found to have negative correlations with the pyrolytic activation energies. However, the effect of the ash content on the activation energy strongly depended on the organic component species present in the lignocellulose feedstocks. This work confirms the possibility of predicting model-free pyrolytic activation energies by utilizing machine learning methods, which can improve the efficiency and understanding of the kinetic analysis of pyrolysis for biomass and fossil investigations.

This dataset contains potential activities of soil extra cellular enzyme measured from soil samples from the Phosphorus Limitation And ecosystem responses to Carbon dioxide Enrichment (PLACE). The enzyme activities measured are 1,4-β-glucosidase, cellobiohydrolase, N-acetyl β-D-glucosaminidase, leucine aminopeptidase, and acid phosphatase. Soil samples were collected in Autumn 2018 and analysed in the laboratory at Wageningen University. The experimental design uses 35 cm x 35 cm turf mesocosms from a long term nutrient manipulation experiment. The original experiment is based at Wardlow Hay Cop in the Peak District, UK. Two adjacent P-limited grass lands on a limestone/ calcareous soil and an acidic soil have had nutrient manipulated for > 20 years. In 2018 these mesocosms were exposed to either ambient CO2 (ca. 410 ppm) or 600 ppm.,All data were generated by the authors. Enzyme analyses were conducted in triplicate (technical replication) and activities of unknown samples were calculated in reference to known substrate standards. All calculations were checked for errors prior to acceptance.

The impacts of two ecological earthworms on the removal of chlortetracycline (CTC, 0.5 and 15 mg kg−1) and antibiotic resistance genes (ARGs) in soil were explored through the soil column experiments. The findings showed that earthworm could significantly accelerate the degradation of CTC and its metabolites (ECTC) in soil (P < 0.05), with epigeic Eisenia fetida promoting degradation rapidly and endogeic Metaphire guillelmi exhibiting a slightly better elimination effect. Earthworms alleviated the abundances of tetR, tetD, tetPB, tetG, tetA, sul1, TnpA, ttgB and intI1 in soil, with the total relative abundances of ARGs decreasing by 35.0–44.2% in earthworm treatments at the 28th day of cultivation. High throughput sequencing results displayed that the structure of soil bacteria community was modified apparently with earthworm added, and some possible CTC degraders, Aeromonas, Flavobacterium and Luteolibacter, were promoted by two kinds of earthworms. Redundancy analysis demonstrated that the reduction of CTC residues, Actinobacteria, Acidobacteria and Gemmatimonadetes owing to earthworm stimulation was responsible for the removal of ARGs and intI1 in soil. Additionally, intI1 declined obviously in earthworm treatments, which could weaken the risk of horizontal transmission of ARGs. Therefore, earthworm could restore the CTC-contaminated soil via enhancing the removal of CTC, its metabolites and ARGs.

The widespread presence of phthalate esters (PAEs) in a variety of agricultural inputs has led to PAE contamination in soils and farm products. The endocrine disruption and carcinogenicity of PAEs have attracted much attention. Our research investigated the characteristics of PAE pollution in the soils of vegetable fields and adjacent stable crop fields in four provinces/municipalities across a major agricultural production area in China. We found that the concentrations of PAEs in vegetable soils were not significantly higher than those in stable crop soils. The noncarcinogenic and carcinogenic risks from bis (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) to humans were calculated to represent the risk posed by PAEs. The results showed that diet was the main route for noncarcinogenic risks from PAEs in crop soil and vegetable soils. Because of the combined effect of the population dietary structure and the concentration of PAEs in soils, the noncarcinogenic risks from PAEs in crop soils were similar to or higher than those in vegetable soils. The same pattern was also applicable to the carcinogenic risk from DEHP. Low noncarcinogenic and carcinogenic risks posed by DEHP and DBP indicated that the current level of PAEs in soils did not decrease the safety of agricultural products in the Huang-Huai-Hai region. Stable crop soil, as a non-negligibly phthalate-polluted area, is worthy of as much attention as vegetable soil. This study provides scientific support for food safety risk assessment and control of PAE pollution in the main agricultural production areas in China.

Iron (Fe) minerals, organic matter (OM), and pH can effectively regulate phosphorus (P) transport in the soil. However, their respective contributions in this regard are still unclear. In this study, P transport in soil columns was investigated by monitoring breakthrough curves and transport model fitting, and the contributions of Fe and total organic carbon (TOC) concentrations, as well as pH to P retention, were determined using multiple linear regression (MLR). The results showed that the rate of P transport in Fe-rich laterite soil was significantly lower (retardation factor R = 458.5) than that in the other soil types (R = 108.4–247.6). Additionally, it was observed that OM formed rate-limited adsorption sites, causing the rapid release of labile P, and owing to P release and readsorption. Even though more significant P releases were observed, chernozem soil had an obvious inhibiting effect on P transport owing to its relatively high Fe content, and the high P-Fe increment (48.9–90.4%) indicated the essential role of Fe minerals in P immobilization. Further, P was readily transported in natural or artificially modified fluvo-aquic soils with high calcium concentrations, and it was also observed that the convection–dispersion equation (CDE) and Thomas models were suitable for describing P retardation and adsorption, respectively. Furthermore, the contribution weights of Fe and TOC concentrations as well as pH to P retardation, based on MLR calculations, were approximately 1.0, −0.3, and −0.2, respectively. Our findings can support the control of eutrophication pollution caused by P leaching.

Ferrihydrite (Fh) is the most important iron (hydr)oxide nanoparticle in nature. Due to its large surface reactivity, Fh influences the cycling, availability, and mobility of nutrients and pollutants in soils and water bodies, largely via adsorption processes. Ferrihydrite also forms stable complexes with natural organic matter (NOM), contributing to the long-term stabilization of organic carbon in soils. In the context of surface complexation modeling (SCM), studying the surface reactivity of Fh is important because this nanomaterial is envisioned as a good proxy for describing the reactivity of the natural metal (hydr)oxide fraction in soils. However, despite the recognized importance of Fh as a highly reactive material, many fundamental aspects of its surface reactivity have remained poorly understood. This thesis aimed to gain new insights into the surface reactivity of Fh, focusing on the analysis of ion adsorption mechanisms and on the development of a SCM framework for describing the adsorption of a suite of relevant cat- and anions to Fh in a realistic physical-chemical manner. In this thesis, a special emphasis is given to the adsorption of phosphate (PO4) and its interfacial interactions with other ions (i.e. Ca, Mg, CO3) that are relevant in nature and from the perspective of soil chemical analysis. Phosphate has been chosen as a model oxyanion due to its ubiquity in the environment and its high affinity for binding Fe (hydr)oxide surfaces. Moreover, the adsorption of Ca and Mg to Fh has been also studied in single-ion systems due to the abundance of these ions in the environment and their effect on the adsorption behavior of other ions, such as PO4. The approaches implemented in this thesis comprise adsorption experiments with freshly-prepared Fh nanoparticles and data interpretation using an advanced SCM (i.e. CD-MUSIC model) as well as molecular orbital (MO) calculations that allow to derive independently the charge distribution (CD) coefficients of the surface complexes considered in the modeling. The consistent treatment of the size dependency of the Fh properties is an essential aspect of this thesis. For this, a novel methodology has been proposed to evaluate the specific surface area (SSA) of Fh nanoparticles in suspension and to derive a coherent set of size-dependent values for the molar mass, mass density, and Stern Layer capacitance(s) of Fh, which are all of major importance for scaling and modeling the collected ion adsorption data. The combination of the above approaches allowed the development of a self-consistent thermodynamic database for describing ion adsorption to Fh. The insights obtained from the model systems, using synthetic Fh suspensions, have been applied to assess the reactive surface area (RSA) of the metal (hydr)oxide fraction in a series of agricultural Dutch top-soils and weathered tropical top-soils. Ferrihydrite is found to be a better proxy than well-crystallized goethite for describing the reactivity of the metal (hydr)oxide fraction in both soil series, despite the contrasting differences in the ratio of crystalline and nanocrystalline metal (hydr)oxides in these two soil series. The reactive metal (hydr)oxide fraction in these soils is dominated by nano-sized particles (~1.5 – 5.0 nm) with a variable specific surface area (SSA ~350 – 1700 m2 g‒1). The interaction between metal (hydr)oxide nanoparticles and NOM has been evaluated in these soil series and a structural model has been formulated for the nanoscale arrangement of the organo-mineral associations in soils. Overall, the results of this thesis are relevant from both a fundamental and a practical perspective. They contribute to increase our understanding of molecular-scale ion adsorption processes occurring at the solid-solution interface of Fh, which is important to develop more accurate predictions of the behavior and availability of ions at the macroscopic level, studied at the laboratory and field scale.

Alkalinity, the excess of proton acceptors over donors, plays a major role in ocean chemistry, in buffering and in calcium carbonate precipitation and dissolution. Understanding alkalinity dynamics is pivotal to quantify ocean carbon dioxide uptake during times of global change. Here we review ocean alkalinity and its role in ocean buffering as well as the biogeochemical processes governing alkalinity and pH in the ocean. We show that it is important to distinguish between measurable titration alkalinity and charge balance alkalinity that is used to quantify calcification and carbonate dissolution and needed to understand the impact of biogeochemical processes on components of the carbon dioxide system. A general treatment of ocean buffering and quantification via sensitivity factors is presented and used to link existing buffer and sensitivity factors. The impact of individual biogeochemical processes on ocean alkalinity and pH is discussed and quantified using these sensitivity factors. Processes governing ocean alkalinity on longer time scales such as carbonate compensation, (reversed) silicate weathering, and anaerobic mineralization are discussed and used to derive a close‐to‐balance ocean alkalinity budget for the modern ocean., Key Points Titration and charge balance alkalinity differThe impact of biogeochemical processes on pH depends on environmental conditionsOcean alkalinity budget is balanced when the additional alkalinity input from riverine particulate inorganic carbon and sedimentary sources is included

Zero-valent iron amended biochar (ZVIB) has been proposed as a promising material in immobilizing heavy metals in paddy fields. In this study, the impacts of pH of ZVIB (pH 6.3 and pH 9.7) and watering management techniques (watering amount in the order of CON (control, 5/72)>3/72>1–3/72>3/100>1/72, with 5/72, for example, representing irrigation given to 5 cm above soil surface in 72 hr regular interval) on As and Cd bioavailability for rice and its grain yield (YieldBR) were investigated in a pot experiment. Brown rice As (AsBR) content was irrelative to the watering treatments, while significantly decreased (>50%) with the addition of both ZVIB materials. The diminutions of brown rice Cd (CdBR) content as well as the YieldBR were highly dependent on both the soil amendment materials’ pH and watering amount. Among all the watering treatments, 3/72 treatment (15% less irrigation water than the CON) with ZVIB 6.3 amendment was the optimum fit for simultaneous reduction of AsBR (50%) and CdBR contents (19%) as well as for significant increment (12%) of the YieldBR. Although high pH (9.7) ZVIB application could also efficiently decrease As and Cd contents in brown rice, it might risk grain yield lost if appropriate (e.g. 3/72 in our study) watering management technique was not chosen. Therefore, ZVIB would be an environmentally friendly option as an amendment material with proper selection of watering management technique to utilize As and Cd co-contaminated arable soils safely for paddy cultivation.

Composting is an essential biochemical process to pre-treat lignocellulosic biomass (e.g., wheat straw) to generate nutritious substrate for industrial Agaricus bisporus production. During composting numerous microbes target (hemi-)cellulose using their enzymatic machinery, while lignin has been assumed to remain unaffected. This research aimed to unravel the chemical and microbial changes during a 4-day industrial composting process with special emphasis on the fate of lignin. A recently developed pyrolysis-GC–MS method using a 13C-lignin isolate as internal standard enabled targeted quantitative lignin analysis. As previously demonstrated, a 40% w/w decrease in (hemi-)cellulose was observed, while unexpectedly lignin decreased by 30% w/w. Increased Cα-oxidized moieties and cleaved interunit linkages substantiated this lignin removal. Simultaneously, a microbial community shift towards Alphaproteobacteria, Gammaproteobacteria, Actinobacteria and Sordariomycetes occurred. Hence, the compost environment provided appropriate conditions to harbor a microbial community to alter and degrade lignin, and this research provides new insights into underlying lignin degradation mechanisms.

This study evaluated the mechanical and environmental properties of cement mortars containing fly ash from biomass combustion as a secondary cementitious material. Cement mortars with 20 and 40% wt. replacement of Portland cement with fly ash from two types of installations were tested for their compressive strength and leaching behaviour. Substitution of 20% Portland cement with wood fly ash complied with the reference standard for compressive strength of 42.5öMPa at 28ödays. Replacement rates of 40% developed a lower strength (30 and 33.5öMPa), but were still suitable for applications. The pulverized fuel ash perform substantially worse. We conclude that the biomass fly ash from fluidized bed combustion performs as a functional secondary cementitious material in cement, whereas the functionality of pulverized fuel fly ash is insufficient. The release of environmentally relevant elements from all the tested specimens fulfilled the Dutch leaching criteria for reuse. During second life as a granular construction material the release of Ba, Cr, Mo and V increased to a level of concern. However, this release was found to be similar to that of existing blended cements and was controlled by cement chemistry. The technical performance of cement mortars was influenced by the type and ratio of fly ash mixed with cement. However, the environmental performance was driven by the cement matrix that controlled the release of contaminants. Using biomass fly ash as a secondary cementitious material can reduce the carbon footprint of concrete by 40% while maintaining good technical and environmental performance.

A novel, regulatory accepted approach is developed that enables competent authorities to decide whether landfill aftercare can be reduced or terminated. Our previous paper (Brand et al., Waste Management 2016, 56, 255–261, https://doi.org//10.1016/j.wasman.2016.07.038) outlines the general approach, that consists of a 10-year treatment phase (e.g., aeration, leachate recirculation), in combination with site-specific Environmental Protection Criteria (EPC) for contaminant concentrations in the landfill leachate after treatment. The current paper presents the unique modelling approach by which the site-specific EPC are derived. The modelling approach is based on the use of mechanistic multi-surface geochemical models covering the main sorption processes in soils underneath the landfills, and is composed of widely-accepted surface complexation models in combination with published “generic” parameter sets. This approach enables the consideration of the main site-specific soil properties that influence the attenuation of emitted contaminants. In addition, the sensitivity of the EPC is shown for variation of the main physicochemical-assumptions and policy-based decisions. Site-specific soil properties have been found to substantially determine the EPC and include soil-pH, dissolved organic matter, and iron-(hydr)oxide content. Apart from the sorption capacity of the local soil, EPC also depend strongly on the assumed dilution with local groundwater in the saturated zone. An important policy-related decision that influences the calculated EPC is the assessment period during which the groundwater is protected. The transparent setup of the approach using geochemical modelling, the explicit consideration of site-specific properties and the achieved regulatory acceptance may also stimulate application to landfills in other countries.

In the environment, simultaneous presence of arsenic (As) of different oxidation states is common, which hampers our understanding of As behavior. In the current study, the pH dependency of arsenite (As(III)) and arsenate (As(V)) adsorption to goethite under the influence of calcium (Ca2+) (as a major cation) and phosphate (PO43−) (as a major anion) was studied, and the reliability of the CD-MUSIC model prediction was tested. The results show that the presence of the major ions led in general to a weaker and more complicated pH dependency of As adsorption. Calcium promoted As(V) adsorption especially at high pH, which can reverse the direction of the pH dependency. The presence of Ca2+ can even decrease As(III) adsorption when As(V) and/or PO43− are present. Phosphate competed strongly with both As(III) and As(V) in their adsorption, especially at intermediate and low pH. In the multi-component system, As(III) adsorbs weaker than As(V) over the environmental relevant pH range, therefore it is often the dominant As species in solution and soluble As(III) concentration generally decreases with increasing pH. In the same pH range, As(V) adsorption shows a complicated pH dependency. Soluble As(V) reaches a minimum around pH 6 at high concentration of major bivalent cations (e.g. Ca2+), whereas soluble As(V) will decrease with pH at low bivalent cation concentrations. The experimental results can be reliably predicted and explained with the CD-MUSIC model. The outcome of this study can provide understanding needed in the risk assessment and remediation of As contaminated soils and water.

Cd and As are difficult to co-remediate in co-contaminated soils. In this study, remediation materials comprising large-grained and nano-sized biochar (BC), ferrihydrite (FH), and complexes thereof were added to Cd- and As-contaminated soil. The uptake of Cd and As by pak choi (Brassica chinensis L.) was then evaluated using a pot experiment and the Cd and As concentrations of the soil pore water and leaching water were measured. The Cd and As concentrations of the pore and leaching water were slightly increased with the addition of BC, and decreased with addition of FH and the biochar–ferrihydrite complex (BC-FH). However, nano-sized BC (BCN), FH (FHN), and BC-FH (BC–FHN) had little influence on the decreases in Cd and As of the two monitored water types. Large-grained remediation materials, rather than nanomaterials, decreased the Cd and As concentrations of the two monitored water types. Nonetheless, nanomaterial treatments more effectively decreased the Cd and As concentrations in plants by an average of >10% relative to the large-grained treatments. The DLVO theory analysis suggested that BCN, FHN, and BC-FHN, immobilized in the topsoil, adsorbed heavy metals in the rhizosphere soil. The remainder of the nano-sized materials was dispersed in the rhizosphere soil pores, shielding the uptake of Cd and As by the roots. Although the doses of nanomaterials used in this study were less than one-fortieth of those of the large-grained materials, changes in the plant rhizosphere microenvironment caused by the nanomaterials decreased the risk of toxicity transfer from the soil to the plants.

Purpose: The electrode aging in soil microbial fuel cells (MFCs) disturbed the removal of pollutants and sensitivity of electrophysiological signal. Therefore, surveying the causes of aging electrodes could assist to take the prevention measures for remediation and biosensor application of soil MFCs. Materials and methods: The surface morphology, element accumulation on the surface of electrodes, and element migration in soils between electrodes were investigated by scanning electronic microscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy in a constructed soil MFC. Results and discussion: The rust was observed on the anode, and the soil gypsification was noted on the cathode after a long-term (300-day) contribution of soil MFCs. The major elements (At%) Na and Ca in soils on two electrodes increased by 338–562 and 100–119%, respectively. Beside, Al and Fe of increment (24 and 21%) in the anode and Mg and Fe of augmenter (84 and 155%) in the cathode were detected. Conclusions: The stacking of Ca and Fe besides Na in soils adjacent to electrodes probably led to the electrode corrosion and soil gypsification on the surface of electrodes. Thus, the electrode aging of soil MFCs should be paid more attention in further applications.

Efficient noninvasive techniques are desired for repairing organic-contaminated soils. Bioelectrochemical technology, especially microbial fuel cells (MFCs), has been widely used to promote a polluted environmental remediation approach, and applications include wastewater, sludge, sediment, and soil remediation. Soil MFC remediation has been of significant concern in recent years, and thus, several aspects, including reactor configuration, electrode materials, soil conductivity, mass transfer, and microbial activity, are reviewed. Recent studies and key issues of soil MFCs and perspectives of organic-contamination remedial application are summarized, with the aim of assisting environmental scholars and engineers to gain a comprehensive understanding of MFC remediation. Insights are also offered on how to extend applications to help soil MFC remediation technology to advance and be applied in the future on a large scale.

This dataset includes the data and calculations underlying the modeling work carried out for the scientific manuscript "Geochemical multi-surface modeling of reactive zinc speciation in compost as influenced by extraction conditions".

Elevated CO2 (eCO(2)) experiments provide critical information to quantify the effects of rising CO2 on vegetation 1-6 . Many eCO(2) experiments suggest that nutrient limitations modulate the local magnitude of the eCO(2) effect on plant biomass(1,3,5), but the global extent of these limitations has not been empirically quantified, complicating projections of the capacity of plants to take up CO27,9. Here, we present a data-driven global quantification of the eCO(2) effect on biomass based on 138 eCO(2) experiments. The strength of CO2 fertilization is primarily driven by nitrogen (N) in similar to 65% of global vegetation and by phosphorus (P) in similar to 25% of global vegetation, with N- or P-limitation modulated by mycorrhizal association. Our approach suggests that CO2 levels expected by 2100 can potentially enhance plant biomass by 12 +/- 3% above current values, equivalent to 59 +/- 13 PgC. The globalscale response to eCO(2) we derive from experiments is similar to past changes in greenness(9) and bio-mass(10) with rising CO2, suggesting that CO2 will continue to stimulate plant biomass in the future despite the constraining effect of soil nutrients. Our research reconciles conflicting evidence on CO2 fertilization across scales and provides an empirical estimate of the biomass sensitivity to eCO(2) that may help to constrain climate projections.

The performance of FeHBED in preventing Fe deficiency chlorosis in soybean (Glycine max (L.) Merr.) in comparison to FeEDDHA and FeEDDHMA was studied, as well as the importance of the ortho-ortho and ortho-para/rest isomers in defining the performance. To this end, chlorophyll production (SPAD), plant dry matter yield, and the mass fractions of important mineral elements in the plant were quantified in a greenhouse pot experiment. All three Fe chelates increased SPAD index and dry matter yield compared to the control. The effect of FeHBED on chlorophyll production was visible over a longer time span than that of FeEDDHA and FeEDDHMA. Additionally, FeHBED did not suppress Mn uptake as much as the other Fe chelates. Compared to the other Fe chelates, total Fe content in the young leaves was lower in the FeHBED treatment; however, total Fe content was not directly related to chlorophyll production and biomass yield. For each chelate, the ortho-ortho isomer was found to be more effective than the other isomers evaluated.

Aims: The study aimed to find soil parameters that are best related to Se plant uptake for low Se soils with predominantly organic Se, and to explore the mechanisms that control Se bioavailability in the soils under study. Methods: A pot experiment using nineteen soil samples taken from different fields of arable land (potato fields) in the Netherlands was conducted on summer wheat (Triticum aestivum L.). Selenium in wheat shoots and soil parameters, including basic soil properties, C:N ratio, inorganic selenite content, and Se and organic C in different soil extractions (0.01 M CaCl2, 0.43 M HNO3, hot water, ammonium oxalate, aqua regia) were analysed. Regression analysis was performed to identify soil parameters that determine Se content in wheat shoots. Results: The regression model shows that Se:DOC ratio in 0.01 M CaCl2 soil extraction explained about 88 % of the variability of Se uptake in wheat shoots. Selenium uptake increased with Se:DOC ratio in CaCl2 extraction, which can be interpreted as a measure of the content of soluble Se-rich organic molecules. Selenium:DOC ratio in CaCl2 extraction and Se uptake increased towards higher soil pH and lower soil C:N ratio. The soil C:N ratio is also negatively correlated to Se:organic C ratio in other extractions (0.43 M HNO3, hot water, ammonium oxalate, aqua regia), indicating that at low soil C:N ratio soil organic matter is richer in Se. Contrarily, the soil pH is positively and strongly correlated to Se:organic C ratio in CaCl2 and hot water extractions, but only weakly correlated to Se:organic C ratio in other extractions. Conclusions: Selenium-rich dissolved organic matter is the source of bioavailable Se in low Se soils with predominantly organic Se. The soil pH and quality of soil organic matter (i.e. soil C:N ratio) are the main soil properties determining Se bioavailability in these soil types.

Environmental contextThe concentration, types and distribution of antibiotics in soils can have environmental effects and can be modelled using laboratory systems. Adsorption of ofloxacin (OFL) and levofloxacin (LEV) enantiomers to goethite can probe this behaviour and each binds differently to the solid phase. The different behaviour of LEV and OFL in relation to solid-solution partitioning will affect their environmental fate. AbstractThe adsorption of ofloxacin enantiomers, namely levofloxacin (LEV) and ofloxacin (OFL), to goethite was investigated using batch experiments. Structural information of aqueous and adsorbed LEV or OFL was obtained with ultraviolet–visible (UV-Vis), three-dimensional excitation–emission matrix (EEM) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopic methods. The results indicated that LEV molecules formed a bridging bidentate complex (≡(FeO)2–LEV) with the surface of goethite, and OFL formed a monodentate complex (≡FeO–OFL). The adsorption of OFL to goethite was stronger than that of LEV, owing to differences in their physicochemical properties and bonding modes. The adsorption of LEV and OFL to goethite in single systems was well simulated using the charge distribution multi-site complexation (CD-MUSIC) model, but their adsorption in the LEV–OFL–goethite systems was overestimated at pH ~5.2 and high concentrations of LEV–OFL mixture (19.59μM), in which the predicted amounts of adsorbed LEV and OFL were higher (20.0, 30.8%) than the experimental results. Compared with the unprotonated LEV or OFL, the protonated (>99.9%) ones were mainly adsorbed to the surface of goethite, and the single species may be used during their following modelling.

Organic matter effectively regulates nanoparticles transport. However, little is known about the effect of agricultural organic inputs on the transport of ferrihydrite nanoparticles (FHNPs) during aging. In this study, columns were filled with sand mixed with varying proportions of pristine, water-processing, or alkali-processing biochar or swine manure and used to simulate the release of organic matter and changes in surface roughness of sand grains during field aging. The influence of these factors on FHNPs transport was investigated using column experiments. The dissolved organic matter (DOM) (0.008–24.8 mg L−1) released from agricultural organic inputs decreased the zeta potential of the FHNPs from 30.8 mV to 14.6–-48.9 mV and further caused electrostatic repulsion, osmotic repulsion, and elastic-steric repulsion between FHNPs and mixed sand, thus enhancing FHNPs transport. Ferrihydrite nanoparticles transport increased with increasing content of biochar and swine manure due to the increased amount of DOM. However, with the presence of organic inputs, surface roughness up to a certain degree (the increase in specific surface area up to 4.6 m2) became the dominant inhibition factor affecting FHNPs transport. After DOM release, agricultural organic inputs decreased the enhancement of FHNPs transport; with the increase input, their rougher surface gradually increased inhibition of FHNPs transport. The strongest FHNPs retention in the alkali-processing biochar (0.2–10%) or swine manure (1–2%) mixed sand columns indicated that fully aged agricultural organic inputs strongly inhibited FHNPs transport. Our findings provided novel insights into the critical influence of agricultural organic inputs and their aging on FHNPs transport, which changed gradually from enhancement to inhibition gradually.

Drinking water company Vitens produces iron sludge and fulvic acid as by-products of their drinking water production process. This study investigated the effectiveness of iron sludge as a source of iron for soybean. A pot experiment was performed with a soybean variety that is susceptible for Fe chlorosis, grown on a clay soil from Tricht (Netherlands) and a calcareous soil from Canaveralejo (Spain). In the Tricht soil, no symptoms of iron chlorosis were observed in any treatment. In the Canaveralejo soil, soybean suffered from iron chlorosis, and iron sludge, with or without fulvic acid, reduced symptoms of iron chlorosis and yield loss as compared to the control treatment. However, iron sludge was not as effective as Fe-HBED since this treatment gave an even higher yield and showed no symptoms of iron chlorosis during the course of the experiment. IJzerslib en fulvozuren zijn bijproducten van het drinkwaterproductieproces van Vitens B.V. Dit rapport beschrijft de resultaten van onderzoek naar de effectiviteit van ijzerslib, al dan niet gemengd met fulvozuur, als ijzernutriënt voor sojaboon op ijzerdeficiënte gronden. Hiervoor is een potproef uitgevoerd met sojaboon van een soort welke gevoelig is voor ijzerchlorose, geteeld op kleigrond uit Tricht (Nederland) en een kalkgrond uit Canaveralejo (Spanje). In de Tricht grond werd geen ijzergebrek waargenomen bij de sojaboon planten. In de Canaveralejo grond vertoonden sojaplanten wel verschijnselen behorende bij ijzergebrek. Behandeling met ijzerslib, al dan niet met fulvozuur, verminderde de ernst van de gebreksverschijnselen en verhoogde de opbrengst t.o.v. de controle. IJzerslib was echter minder effectief dan de behandeling met Fe-HBED, welke een hogere opbrengst gaf en waarin geen symptomen van ijzerchlorose werd waargenomen.

In this study, the reactions of engineered nanoparticles (ENPs) in soils, with respect to their nanospecific properties, and observed effects of key soil properties (e.g. pH, ionic strength and natural colloids) on their stability in pore water are discussed. Key processes include aggregation and dissolution of ENPs, straining of ENPs in the solid matrix, stabilization of ENPs in pore water due to binding of molecules from dissolved organic matter (DOM) and inorganic colloids and the effect of artificial coatings. In view of these processes, this study provides guidance in the development of a framework to measure available and total soil contents of ENPs, via a set of extraction methods and advanced analytical tools. Particularly, the lack of effective extraction methods is thoroughly discussed regarding the identification of most relevant research gaps preventing an effective assessment of the availability, mobility and risks of exposure of sensitive receptors to ENPs in soils. (C) 2015 Elsevier B.V. All rights reserved.